Science.gov

Sample records for subcooled hydrothermal boiling

  1. Saturated and subcooled hydrothermal boiling in groundwater flow channels as a source of harmonic tremor

    NASA Astrophysics Data System (ADS)

    Leet, Robert C.

    1988-05-01

    The potential of hydrothermal boiling in groundwater flow channels for generating harmonic tremor (a relatively monochromatic ground vibration associated with volcanic activity) is examined. We use simple "organ pipe" theory of normal-mode fluid vibration and fundamental energy considerations to develop a first-order analytical model of a hydrothermal-boiling source of harmonic tremor. We use this model to estimate order-of-magnitude groundwater flow channel lengths and boiling heat transfer rates required to produce harmonic tremor with dominant frequencies in the range 0.5-5 Hz and surface wave reduced displacements of up to 100 cm2. Depending on groundwater sound speed, flow channel lengths of the order of 1-1000 m are required to produce fluid vibration eigenfrequencies in the range 0.5-5 Hz. The boiling heat transfer rate required to produce tremor with a given surface wave reduced displacement depends on the tremor frequency and on whether saturated boiling or subcooled boiling is the cause of the tremor. Saturated boiling produces groundwater vibration via steam bubble growth, whereas subcooled boiling produces groundwater vibration via steam bubble collapse. We find that subcooled hydrothermal boiling is from 102 to 104 times more efficient than saturated boiling in converting boiling "thermal" power to seismic power. For example, the boiling heat transfer rates required to produce 1-Hz tremor with reduced displacements of up to 100 cm2 via subcooled boiling are generally less than a few thousand megawatts; for saturated boiling, the required boiling heat transfer rates are several orders of magnitude larger than this. The highest values of heat flow reported in the literature for volcanic crater lakes and terrestrial and ocean floor geothermal areas are of the order of 1000 MW. Taking this value as a first-order estimate of an upper limit on possible boiling heat transfer rates in volcanic hydrothermal systems, our results suggest that saturated hydrothermal boiling is capable of generating only low-amplitude harmonic tremor, with surface wave reduced displacements no higher than a few square centimeters. However, subcooled hydrothermal boiling could potentially generate high-amplitude harmonic tremor, with reduced displacements as large as several hundred square centimeters. As a specific application of our model, we evaluate the potential of hydrothermal boiling for generating harmonic tremor at recently active Mount St. Helens and Nevado Del Ruiz volcanoes. We conclude that subcooled boiling likely could have produced the tremor episodes considered at both volcanoes. Saturated boiling also could explain the Nevado Del Ruiz tremor but probably not the more powerful Mount St. Helens tremor.

  2. Theory of Subcooled Boiling

    SciTech Connect

    Bankoff, S. G.; Davis, S. H.

    2002-09-15

    Subcooled boiling refers to boiling from a heated solid surface when the bulk liquid is below the saturation temperature. Particularly, when there is a bulk liquid flow past the surface, the heat fluxes thus sustained can be very large, in fact, subcooled boiling is the most efficient mode of cooling high-heat flux surfaces known, and as such is useful for cooling densely-packed computer microchips, as well as other applications, as in the heat treatment of metals. We have studied several aspects of subcooled boiling from a fundamental aspect, leading, among other things, to a resolution of a long-standing question as to the dominant mechanism of subcooled boiling: vapor transport through an ultrathin layer liquid underneath the growing bubble or stirring of the liquid surrounding the growing-and collapsing bubble.

  3. (Investigation of subcooled hydrothermal boiling in ground water flow channels as a source of harmonic tremors)

    SciTech Connect

    Not Available

    1989-01-01

    As a first step toward assessing the ability of hydrothermal boiling to explain geothermal ground noise and volcanic tremor observations, we are investigating the acoustic power spectrum of boiling (the source'' spectrum in the above model). We simulate boiling in the lab by injecting high pressure steam from a boiler into a pressure vessel filled with water. The water pressure fluctuations that result from the repeated formation and collapse of steam bubbles at the steam inlet vents are recorded by a hydrophone whose output is digitized at 2 {times} 10{sup 4} samples/second by a computer. The range of pressure and temperature conditions attainable within the pressure vessel is limited to <3.5 bars, <139{degree}C, due to the finite strength of observation windows affixed to the pressure vessel. Therefore, dimensional analysis will be used to correlate the experimental results with the pertinent experimental variables. Besides the overall shape of the boiling power spectrum, we are investigating the absolute spectral levels in frequency bands typical of geothermal ground noise and volcanic tremor (0.5 Hz-10 Hz), and the ratio of acoustic power liberated to total available power. The values of these parameters are critical to hydrothermal boiling's ability to generate ground motion amplitudes in accordance with observation. If it can be shown that the range of observed ground noise/tremor amplitudes can be accounted for by hydrothermal boiling at reasonable heat transfer rates, this knowledge would be invaluable to designers of seismic monitoring experiments who are interested in geothermal resource exploration/evaluation and volcanic eruption prediction.

  4. Subcooled flow boiling at high heat flux

    NASA Astrophysics Data System (ADS)

    Delvallem, V. H.; Kenning, D. B. R.

    Subcooled flow nucleate boiling of water at atmospheric pressure on stainless steel was studied. The heat transfer coefficient increases with increasing subcooling and also with increasing wall thickness over the range 0.08 to 0.20 mm. Bubble size, frequency, and the distribution of nucleation sites were measured at 1.7 m/sec inlet velocity, 80 C subcooling, 0.08 mm wall thickness, and heat fluxes 70% to 95% of the critical flux. The observations are consistent with a model for heat transfer primarily by surface quenching at the bubble frequency, supplemented by single-phase convection and a small contribution from microlayer evaporation. Although the total population of nucleation sites increases with increasing wall superheat, the start-up of new sites deactivates sites active at lower superheat.

  5. Critical heat flux in subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    Hall, David Douglas

    The critical heat flux (CHF) phenomenon was investigated for water flow in tubes with particular emphasis on the development of methods for predicting CHF in the subcooled flow boiling regime. The Purdue University Boiling and Two-Phase Flow Laboratory (PU-BTPFL) CHF database for water flow in a uniformly heated tube was compiled from the world literature dating back to 1949 and represents the largest CHF database ever assembled with 32,544 data points from over 100 sources. The superiority of this database was proven via a detailed examination of previous databases. The PU-BTPFL CHF database is an invaluable tool for the development of CHF correlations and mechanistic models that are superior to existing ones developed with smaller, less comprehensive CHF databases. In response to the many inaccurate and inordinately complex correlations, two nondimensional, subcooled CHF correlations were formulated, containing only five adjustable constants and whose unique functional forms were determined without using a statistical analysis but rather using the parametric trends observed in less than 10% of the subcooled CHF data. The correlation based on inlet conditions (diameter, heated length, mass velocity, pressure, inlet quality) was by far the most accurate of all known subcooled CHF correlations, having mean absolute and root-mean-square (RMS) errors of 10.3% and 14.3%, respectively. The outlet (local) conditions correlation was the most accurate correlation based on local CHF conditions (diameter, mass velocity, pressure, outlet quality) and may be used with a nonuniform axial heat flux. Both correlations proved more accurate than a recent CHF look-up table commonly employed in nuclear reactor thermal hydraulic computer codes. An interfacial lift-off, subcooled CHF model was developed from a consideration of the instability of the vapor-liquid interface and the fraction of heat required for liquid-vapor conversion as opposed to that for bulk liquid heating. Severe vapor effusion in an upstream wetting front lifts the vapor-liquid interface off the surface, triggering CHF. Since the model is entirely based on physical observations, it has the potential to accurately predict CHF for other fluids and flow geometries which are beyond the conditions for which it was validated.

  6. Unsteady heat transfer during subcooled film boiling

    NASA Astrophysics Data System (ADS)

    Yagov, V. V.; Zabirov, A. R.; Lexin, M. A.

    2015-11-01

    Cooling of high-temperature bodies in subcooled liquid is of importance for quenching technologies and also for understanding the processes initiating vapor explosion. An analysis of the available experimental information shows that the mechanisms governing heat transfer in these processes are interpreted ambiguously; a more clear-cut definition of the Leidenfrost temperature notion is required. The results of experimental observations (Hewitt, Kenning, and previous investigations performed by the authors of this article) allow us to draw a conclusion that there exists a special mode of intense heat transfer during film boil- ing of highly subcooled liquid. For revealing regularities and mechanisms governing intense transfer of energy in this process, specialists of Moscow Power Engineering Institute's (MPEI) Department of Engineering Thermal Physics conduct systematic works aimed at investigating the cooling of high-temperature balls made of different metals in water with a temperature ranging from 20 to 100°C. It has been determined that the field of temperatures that takes place in balls with a diameter of more than 30 mm in intense cooling modes loses its spherical symmetry. An approximate procedure for solving the inverse thermal conductivity problem for calculating the heat flux density on the ball surface is developed. During film boiling, in which the ball surface temperature is well above the critical level for water, and in which liquid cannot come in direct contact with the wall, the calculated heat fluxes reach 3-7 MW/m2.

  7. The entrance effect on subcooled boiling in heated channels

    SciTech Connect

    Kurul, N.; Podowski, M.Z. )

    1989-11-01

    One of the major problems in the analysis of diabatic two-phase flows concerns the effect of thermodynamic nonequilibrium between the phases. In particular, this effect applies to forced-convection subcooled boiling in boiling water reactors (BWRs). An approach commonly used to evaluate the void distribution along reactor coolant channels is based on one-dimensional models of combined two-phase flow and boiling heat transfer. In the subcooled boiling region, the rate of phase change is governed mainly by the lateral transport of the vapor phase toward the subcooled liquid; thus, the related processes cannot be mechanistically modeled by one-dimensional, axially dependent models. Consequently, most existing subcooled boiling models are based on experimental correlations for parameters such as the onset of nucleate boiling (ONB) and the net vapor generation rate. This paper presents the results of analysis of subcooled boiling phenomena in the developing flow region of a boiling channel, based on a mechanistic two-dimensional, two-fluid model. The effect of turbulence has been accounted for by a k-{epsilon} model. The PHOENICS code was used to solve the governing mass, momentum, and energy conservation equations in both the nonboiling and boiling regions. The parameters calculated by the model include radially and axially dependent distributions of the local void fraction, temperatures and velocities of both phases, and the axial distribution of wall temperature.

  8. RELAP5/MOD3 subcooled boiling model assessment

    SciTech Connect

    Devkin, A.S.; Podosenov, A.S.

    1998-05-01

    This report presents the assessment of the RELAP5/Mod3 (5m5 version) code subcooled boiling process model which is based on a variety of experiments. The accuracy of the model is confirmed for a wide range of regime parameters for the case of uniform heating along the channel. The condensation rate is rather underpredicted, which may lead to considerable errors in void fraction behavior prediction in subcooled boiling regimes for nonuniformly or unheated channels.

  9. Transition to Film Boiling in Microgravity: Influence of Subcooling

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Fu; Li, Jing; Yan, Na; Wang, Shuang-Feng

    2010-07-01

    The transition process to film pool boiling in microgravity is studied experimentally aboard the Chinese recoverable satellite SJ-8. A quasi-steady heating method is adopted, in which the heating voltage is controlled to increase exponentially with time. Small, primary bubbles are formed and slid on the surface, which coalesce with each other to form a large coalesced bubble. Two ways are observed for the transition from nucleate to film boiling at different subcoolings. At high subcooling, the coalesced bubble with a smooth surface grows slowly. It is then difficult for the coalesced bubble to cover the whole heater surface, resulting in a special region of transition boiling in which nucleate boiling and local dry areas can coexist. In contrast, strong oscillation of the coalesced bubble surface at low subcooling may cause rewetting of local dry areas and activation of more nucleate sites, resulting in an abrupt transition to film boiling.

  10. Improvements in Predicting Void Fraction in Subcooled Boiling

    SciTech Connect

    Ha, Kwi Seok; Lee, Yong Bum; No, Hee Cheon

    2005-06-15

    A simple two-phase thermal-hydraulic tool with the drift-flux model has been used to develop a subcooled boiling model. The tool is composed of four governing equations: mixture mass, vapor mass, mixture momentum, and mixture enthalpy. Using the developed tool, various subcooled boiling models were investigated through the published experimental data. In the process of evaluation, two models were developed associated with the subcooled boiling. First, the Saha and Zuber correlation predicting the point of the net vapor generation was modified to consider the thermal and dynamic effects at the high-velocity region. Second, the pumping factor model was developed using the pi-theorem based on parameters related to the bubble generation mechanism, and it produced an additional parameter: the boiling number. The proposed models and several other models were evaluated against a series of subcooled flow boiling experiments at the pressure range of 1 to 146.8 bars. From the root-mean-square analysis for the predicted void fraction in the subcooled boiling region, the results of the proposed model presented the best predictions for the whole-pressure ranges. Also, the implementation of the developed models into RELAP5/MOD3.3 brought about improved results compared to those of the default model of the code.

  11. Bubble behavior and mean diameter in subcooled flow boiling

    SciTech Connect

    Zeitoun, O.; Shoukri, M.

    1996-02-01

    Bubble behavior and mean bubble diameter in subcooled upward flow boiling in a vertical annular channel were investigated under low pressure and mass flux conditions. High-speed photographic results indicated that, contrary to the common understanding, bubbles tend to detach from the heating surface upstream of the net vapor generation point. Digital image processing technique was used to measure the mean bubble diameter along the subcooled flow boiling region. Data on the axial area-averaged void fraction distributions were also obtained using a single-beam gamma densitometer. Effects of the liquid subcooling, applied heat flux and mass flux on the mean bubble size were investigated. A correlation for the mean bubble diameter as a function of the local subcooling, heat flux, and mass flux was obtained. 28 refs., 8 figs., 1 tab.

  12. Subcooled forced convection boiling of trichlorotrifluoroethane

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Panian, D. J.

    1972-01-01

    Experimental heat-transfer data were obtained for the forced-convection boiling of trichlorotrifluoroethane (R-113 or Freon-113) in a vertical annular test annular test section. The 97 data points obtained covered heat transfer by forced convection, local boiling, and fully-developed boiling. Correlating methods were obtained which accurately predicted the heat flux as a function of wall superheat (boiling curve) over the range of parameters studied.

  13. Subcooled Boiling Near a Heated Wall

    SciTech Connect

    T.A. Trabold; C.C. Maneri; P.F. Vassallo; D.M. Considine

    2000-10-27

    Experimental measurements of void fraction, bubble frequency, and velocity are obtained in subcooled R-134a flowing over a heated flat plate near an unheated wall and compared to analytical predictions. The measurements were obtained for a fixed system pressure and mass flow rate (P = 2.4 MPa and w = 106 kg/hr) at various inlet liquid temperatures. During the experiments, electrical power was applied at a constant rate to one side of the test section. The local void fraction data, acquired with a hot-film anemometer probe, showed the existence of a significant peak near the heated wall and a smaller secondary peak near the unheated wall for the larger inlet subcoolings. Local vapor velocity data, taken with the hot-film probe and a laser Doppler velocimeter, showed broad maxima near the centerline between the heated and unheated plates. Significant temperature gradients near the heated wall were observed for large inlet subcooling. Bubble size data, inferred from measurements of void fraction, bubble frequency and vapor velocity, when combined with the measured bubble chord length distributions illustrate the transition from pure three dimensional spherical to two-dimensional planar bubble flow, the latter being initiated when the bubbles fill the gap between the plates. These various two-phase flow measurements were used for development of a multidimensional, four-field calculational method; comparisons of the data to the calculations show reasonable agreement.

  14. Changes of enthalpy slope in subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    Collado, Francisco J.; Monné, Carlos; Pascau, Antonio

    2006-03-01

    Void fraction data in subcooled flow boiling of water at low pressure measured by General Electric in the 1960s are analyzed following the classical model of Griffith et al. (in Proceedings of ASME-AIChE heat transfer conference, #58-HT-19, 1958). In addition, a new proposal for analyzing one-dimensional steady flow boiling is used. This is based on the physical fact that if the two phases have different velocities, they cannot cover the same distance—the control volume length—in the same time. So a slight modification of the heat balance is suggested, i.e., the explicit inclusion of the vapor liquid velocity ratio or slip ratio as scaling time factor between the phases, which is successfully checked against the data. Finally, the prediction of void fraction using correlations of the net rate of change of vapor enthalpy in the fully developed regime of subcooled flow boiling is explored.

  15. Development of a mechanistic model for forced convection subcooled boiling

    NASA Astrophysics Data System (ADS)

    Shaver, Dillon R.

    The focus of this work is on the formulation, implementation, and testing of a mechanistic model of subcooled boiling. Subcooled boiling is the process of vapor generation on a heated wall when the bulk liquid temperature is still below saturation. This is part of a larger effort by the US DoE's CASL project to apply advanced computational tools to the simulation of light water reactors. To support this effort, the formulation of the dispersed field model is described and a complete model of interfacial forces is formulated. The model has been implemented in the NPHASE-CMFD computer code with a K-epsilon model of turbulence. The interfacial force models are built on extensive work by other authors, and include novel formulations of the turbulent dispersion and lift forces. The complete model of interfacial forces is compared to experiments for adiabatic bubbly flows, including both steady-state and unsteady conditions. The same model is then applied to a transient gas/liquid flow in a complex geometry of fuel channels in a sodium fast reactor. Building on the foundation of the interfacial force model, a mechanistic model of forced-convection subcooled boiling is proposed. This model uses the heat flux partitioning concept and accounts for condensation of bubbles attached to the wall. This allows the model to capture the enhanced heat transfer associated with boiling before the point of net generation of vapor, a phenomenon consistent with existing experimental observations. The model is compared to four different experiments encompassing flows of light water, heavy water, and R12 at different pressures, in cylindrical channels, an internally heated annulus, and a rectangular channel. The experimental data includes axial and radial profiles of both liquid temperature and vapor volume fraction, and the agreement can be considered quite good. The complete model is then applied to simulations of subcooled boiling in nuclear reactor subchannels consistent with the operating conditions of the AP1000 pressurized water reactor. The effects of both axial and lateral nonuniform power distributions inside reactor fuel elements are accounted for. Boiling flows are simulated for three different computational domains of increasing complexity: a quarter-subchannel bordering a single fuel pin, two subchannels surround by an array of 2 by 3 fuel pins, and in four subchannels surrounded by an array of 3 by 3 fuel pins. The predicted behavior is consistent with expectations. In the 3 by 3 array, the two-phase coolant is predicted to flow from the hot channels to the cold channels, enhancing heat exchange between subchannels. This, in turn, demonstrates that the new model is capable of capturing the turbulence- and buoyancy-induced coolant mixing across the neighboring channels.

  16. Critical Heat Fluxes of Subcooled Water Flow Boiling against Inlet Subcooling in Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Komori, Hirokazu; Shiotsu, Masahiro; Noda, Nobuaki

    The critical heat fluxes (CHFs) of subcooled water flow boiling for the test tube inner diameters (d=3 and 6mm) and the heated lengths (L=67, 120 and 150mm) are systematically measured for the flow velocities (u=4.0 to 13.3m/s), the inlet subcoolings (ΔTsub, in=48 to 148K), the outlet subcoolings (ΔTsub, out=10.5 to 95.1K), the inlet pressure (Pin=753 to 995kPa) and the outlet pressure (Pout=720 to 887kPa). The SUS304 tubes of L=67, 120 and 150mm for d=3mm and L=150mm for d=6mm are used. The values of L/d are 22, 40 and 50 for d=3mm, and 25 for d=6mm, respectively. The CHFs, qcr, sub, for a fixed ΔTsub, out become gradually lower with an increase in the L/d in the whole experimental range. The CHF correlation against outlet subcooling, which has been previously derived for L/d lower than 16, was modified to new one containing the L/d effect based on these experimental data. Furthermore, the relation between qcr, sub and L/d for a fixed ΔTsub, in was checked. The values of qcr, sub for a fixed ΔTsub, in became exponentially lower with the increase in L/d. CHF correlation against inlet subcooling has been given based on the experimental data for L/d ranging from 4.08 to 50. The correlations against outlet and inlet subcoolings can describe not only the CHFs obtained in this work for the inner diameter of 3 and 6mm at the outlet pressure of around 800kPa but also the authors' published CHFs data (1611 points) for the wide ranges of Pin=159kPa to 1MPa, d=3 to 12mm, L=33 to 150mm and u=4.0 to 13.3m/s within 15% difference for 30K≤ΔTsub, out≤140K and 40K≤ΔTsub, in≤151K.

  17. Critical heat flux in forced convective subcooled boiling with a plane wall jet (effect of subcooling on CHF)

    NASA Astrophysics Data System (ADS)

    Wang, X.; Monde, M.

    Critical heat flux (CHF) during forced convective subcooled boiling with a plane jet has been yet made insufficient except for saturation condition when comparing CHF with impinging jet system including multiple jets. The present experiment has measured the CHF with plane jet on a rectangular heated surface of 40, 60, and 80mm in length and 10 and 20mm in width. Subcooled liquid being supplied through the plane jet with a different thickness of 1 and 2mm, covers the heated surface where rigorous boiling takes place. The experiment varies a jet velocity from 3 to 15m/s, a subcooling from 0 to 60K, and system pressure at 0.1MPa for water and at 1.5 to 3.0MPa for R22. It is found that the existing correlation for saturation can be applied to the CHF of water, but hardly to the CHF of R22 in spite of saturation condition. After the effects of jet velocity and subcooling on the CHF can be elucidated, a new correlation including the effect of subcooling is proposed to predict most of the CHF data within an accuracy of +/-20 percent. This correlation for saturated condition is found to interestingly agree with that theoretically derived by applying the Katto and Haramura criterion to this system.

  18. Effect of subcooling on film boiling from a downward-facing curved surface

    SciTech Connect

    El-Genk, M.S.; Glebov, A.G.

    1995-12-31

    Pool boiling from inclined and downward-facing flat and curved surfaces is of interest to the passive cooling of the pressure vessel lower head of a Light Water Reactor following a core meltdown accident. The effect of water subcooling on film boiling from a downward-facing curved surface was investigated experimentally. The local and surface average Nusselt numbers were correlated for both saturation and subcooling (5, 10, and 14 K) conditions. Video images of boiling surface and analysis of data demonstrated that surface rewetting in saturation boiling was hydrodynamic in nature, but thermally driven in subcooled boiling. Results confirmed that lower minimum film boiling heat flux values were associated with longer rewetting times and vice versa. Surface rewetting occurred when vapor film reached a critical thickness, {delta}{sub c}, first at the lowermost position, {theta} = 0{degree}, then sequentially at higher inclinations. For saturation boiling, {delta}{sub c} {approximately} 85 {micro}m and 180 {micro}m at {theta} = 0{degree} and 8.26{degree}, respectively. For subcooled boiling, however, {delta}{sub c} varied for {approximately}50 to 175 {micro}m, depending on the values of local inclination and water subcooling.

  19. The influence of bubble size on void fraction distribution in subcooled flow boiling at low pressure

    SciTech Connect

    Tu, J.Y. )

    1999-07-01

    Subcooled flow boiling is encountered in many applications: nuclear reactors, boilers, refrigeration systems, and heat exchangers. The effect of bubble size on void fraction distribution in subcooled flow boiling in a vertical annular channel at low pressure is studied numerically. It is found that a simple linear formula used by Anglart and Nylund and adopted for calculation of bubble size as a function of local subcooling lacks a physical and experimental basis limiting the general application of the model for predicting subcooled flow boiling. A bubble size correlation proposed by Zeitoun and Shoukri has been employed in this study. The predictions of void fraction profiles and the bubble size distributions, after incorporating the above bubble size correction, show very good agreement with the experimental data.

  20. Numerical study on temperature distribution around a boiling bubble departing from heating surface in subcooled pool

    NASA Astrophysics Data System (ADS)

    Ose, Yasuo; Kunugi, Tomoaki

    2014-06-01

    In this paper, the transient three-dimensional numerical simulations based on the MARS (Multi-interface Advection and Reconstruction Solver) with the non-empirical boiling and condensation model have been conducted for an isolated boiling bubble behavior in a subcooled pool. The temperature distributions formed around the subcooled pool boiling bubble departing from a heating surface obtained by the numerical simulations were investigated. As the results, it was found that several thermal plumes with different temperature were formed during the bubble departure from the heating surface by using the volume rendering visualization technique.

  1. Subcooled and low quality film boiling of water in vertical flow at atmospheric pressure. [PWR; BWR

    SciTech Connect

    Fung, K.K.

    1981-08-01

    Subcooled and low quality film boiling is usually encountered in safety analyses of nuclear reactors. In most of the previous subcooled film boiling studies, cryogenic fluids were used either in a stagnant pool or a forced convective set-up. These data cannot be applied to reactor safety analysis without excessive conservatism or skepticism. In this study, a unique method is used to establish flow film boiling of water in a vertical tube at atmospheric pressure. The data cover a mass flux range of 50 to 500 kg.m/sup -2/.s/sup -1/ and an inlet subcooling range of 5 to 70/sup 0/C. It is found that the heat transfer coefficient depends on the mass flux, inlet subcooling and the axial distance from the point where film boiling first starts. A physical model is developed to predict the wall temperature of a tube during inverted annular film boiling. It considers the thermal boundary layers in the subcooled liquid core and in the superheated vapor film. The predicted wall temperatures and void fractions compare well with the measurements.

  2. Local nucleation propagation on heat transfer uniformity during subcooled convective boiling

    NASA Astrophysics Data System (ADS)

    Kim, Beom Seok; Yang, Gang Mo; Shin, Sangwoo; Choi, Geehong; Cho, Hyung Hee

    2015-01-01

    Convective boiling heat transfer is an efficient cooling mechanism to dissipate amount of thermal energy by accompanying the phase transition of the working fluids. Particularly, the amount of heat dissipation capacity can be readily extensible by increasing the degree of subcooling due to initial demands requiring for coolant saturation. Under severely subcooled condition of 60°, we investigate boiling heat transfer phenomena regarding spatial heat transfer uniformity and stability on a planar surface. Severe subcooling can induce locally concentrated thermal loads due to poor spatial uniformity of the heat transfer. For reliable cooling, a high degree of spatial uniformity of the heat transfer should be guaranteed with minimized spatial deviation of heat transfer characteristics. Under pre-requisite safeguards below CHF, we experimentally elucidate the principal factors affecting the spatial uniformity of the heat transfer for a flow/thermal boundary layer considering heat transfer domains from a single-phase regime to a fully-developed boiling regime. Based on the local heat transfer evaluation, we demonstrate that full nucleation boiling over the entire heat transfer surface under subcooling conditions is favorable in terms of the uniformity of heat dissipation through the phase-change of the working fluid.

  3. Local Heat Transfer and CHF for Subcooled Flow Boiling - Annual Report 1994

    SciTech Connect

    Dr. Ronald D. Boyd

    2000-07-01

    The physical phenomenon of forced convective boiling is probably one of the most interesting and complex transport phenomena. It has been under study for more than two centuries. Simply stated, forced convective subcooled boiling involves a locally boiling fluid: (1) whose mean temperature is below its saturation temperature, and (2) that flows over a surface exposed uniformly or non-uniformly to a high heat flux (HHF). The objective of this work is to assess and/or improve the present ability to predict local axial heat transfer distributions in the subcooled flow boiling regime for the case of uniformly heated coolant channels. This requires an accurate and complete representation of the boiling curve up to the CHF. The present. results will be useful for both heat transfer research and industrial design applications. Future refinements may result in the application of the results to non-uniformly heated channels or other geometries, and other fluids. Several existing heat transfer models for uniformly heated channels were examined for: (1) accurate representation of the boiling curve, and (2) characterizing the local heat transfer coefficient under high heat flux (HHF) conditions. Comparisons with HHF data showed that major correlation modifications were needed in the subcooled partial nucleate boiling (SPNB) region. Since the slope of boiling curve in this region is important to assure continuity of the HHF trends into the fully developed boiling region and up to the critical heat flux, accurate characterization in the SPNB region is essential. Approximations for the asymptotic limits for the SPNB region have been obtained and have been used to develop an improved composite correlation. The developed correlation has been compared with 363 water data points. For the local heat transfer coefficient and wall temperature, the over-all percent standard deviations with respect to the data were 19% and 3%, respectively, for the high velocity water data.

  4. Influence of Heating Rate on Subcooled Flow Boiling Critical Heat Flux in a Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki

    The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m/s), the inlet subcoolings (ΔTsub, in=130 to 161K), the inlet pressure (Pin=812 to 1315kPa), the dissolved oxygen concentration (O2=5.88 and 7.34ppm) and the increasing heat input (Q0exp(t/τ), τ=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test tube inner diameter (d=6mm), heated length (L=60mm), L/d=10 and wall thickness (δ=0.5mm) with the rough finished inner surface (Surface roughness, Ra=3.18µm) is used in this work. The CHF data for high heating rate were compared with the quasi steady state ones previously obtained and the values calculated by the steady state CHF correlations against outlet and inlet subcoolings. Transient CHF correlation against inlet subcooling has been given based on the experimental data for wide exponentially increasing heat input (Q0exp(t/τ), τ=38.1ms to 8.3s). The influence of heating rate on CHF was investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux for high heating rate was discussed.

  5. Visualization of Sub-Cooled Flow Film Boiling in Horizontal Channel on Flat Heat Exchangers

    SciTech Connect

    Wen Wu; Peipei Chen; Jones, Barclay G.; Newell, Ty A.

    2006-07-01

    The observation of sub-cooled flow film boiling was performed on a single-side-heated flat heat exchanger by using refrigerant R134a as the testing fluid. A stable vapor film was observed with the co-existence of sub-cooled bulk liquid. Vapor bubbles might release from the film, with the number and frequency changing under different conditions. The purpose of this paper is to describe these observations, and to provide a quantitative analysis of the phenomena. Results are compared with Berenson's model on horizontal heating surface, with discussion and suggestion made. (authors)

  6. Subcooled flow film boiling across a horizontal cylinder. Part II. Comparison to experimental data

    SciTech Connect

    Chou, X.S.; Sankaran, S.; Witte, L.C. )

    1995-02-01

    In this paper, the results of a rigorous heat transfer analysis of subcooled flow film boiling over a heated cylinder are compared to experimental data. The analysis includes both the influence of the front part of the heater and the wake region behind the heater. Experiments using Freon-113 were conducted at subcooling levels up to 58[degree]C and at velocities up to 3.81 m/s. The configuration was upflowing Freon-113 in crossflow over a 0.635-cm electric heater. A comparison of these data as well as other available experimental data to the analysis of Chou and Witte showed good agreement as long as the subcooling level of the liquid was substantial - that is, for liquid Jakob numbers above about 0.04. This represents a considerable improvement over other models that have been developed to predict subcooled flow boiling heat transfer. A method using a temperature correction to a constant-property heat transfer solution that corresponds to the full variable-property solution is also presented, and applied to water and Freon-113. 11 refs., 5 figs., 2 tabs.

  7. Analysis and Measurement of Bubble Dynamics and Associated Flow Field in Subcooled Nucleate Boiling Flows

    SciTech Connect

    Barclay G. Jones

    2008-10-01

    In recent years, subooled nucleate boiling (SNB) has attrcted expanding research interest owing to the emergence of axial offset anomaly (AOA) or crud-induced power shigt (CIPS) in many operating US PWRs, which is an unexpected deviation in the core axial power distribution from the predicted power curves. Research indicates that the formation of the crud, which directly leads to AOA phenomena, results from the presence of the subcooled nucleate boiling, and is especially realted to bubble motion occurring in the core region.

  8. The effect of the radiative heat transfer on subcooled film boiling

    NASA Astrophysics Data System (ADS)

    Nilsuwankosit, Sunchai

    A Monte-Carlo model for the radiative heat transport was constructed to simulate the absorption of radiative heat in various parts of a multiphase medium of different configurations. The results obtained from the simulations were used to construct a profile which could be used to calculate the intensity of radiative heat in a given system. Together with the data on the absorption coefficients of liquid water and steam, the obtained profile was used to evaluate the volumetric heat source due to absorption of radiative heat in the medium. This volumetric heat source was applied in the boundary layer equations for subcooled film boiling. With the results obtained by solving the boundary layer equations for subcooled film boiling over a heating planar surface and over a heating spherical surface, the correlations describing the fraction of radiative heat absorbed in the liquid boundary layer for subcooled film boiling were constructed. The mixing phase calculation of the fuel-coolant interaction (FCI) by the computer code TEXAS was improved with the obtained correlations to account for the effect of radiative heat transfer. This verified that part of the radiative heat lost from the system was due to the small absorption coefficient of the steam and the absorption of radiative heat at the wall of the vessel. Because liquid water has a much larger absorption coefficient, more radiative heat is absorbed in water which then results in a lower temperature for steam and a higher temperature for water compared to that calculated without the effect of the radiative heat.

  9. Bubble Behavior in Subcooled Pool Boiling of Water under Reduced Gravity

    NASA Astrophysics Data System (ADS)

    Suzuki, Koichi; Suzuki, Motohiro; Takahash, Saika; Kawamura, Hirosi; Abe, Yoshiyuki

    2003-01-01

    Subcooled pool boiling of water was conducted in reduced gravity performed by a parabolic flight of aircraft and a drop-shaft facility. A small stainless steel plate was physically burned out in the subcooled water by AC electric power during the parabolic flight. Boiling bubbles grew with increasing heating power but did not detached from the heating surface. The burnout heat fluxes obtained were 200 ~ 400 percent higher than the existing theories. In the ground experiment, boiling bubbles were attached to the heating surface with a flat plate placed over the heating surface, and the experiment was performed by the same heating procedure as practiced under the reduced gravity. Same burnout heat fluxes as under the reduced gravity were obtained by adjusting the plate clearance to the heating surface. As the heating time extended longer than the reduced gravity duration, the burnout heat fluxes decreased gradually and became constant. Contact area of bubbles with heating surface was observed using a transparent heating surface in microgravity performed by a drop-shaft facility. The contact area of bubbles increased significantly at the start of microgravity. It is suggested by the experimental results that the boiling bubbles expand rapidly in the high heat flux region and the rapid evaporation of liquid layer remained between the bubbles and the heating surface raises up the critical heat flux higher than the existing theories in microgravity.

  10. Modeling the onset of flow instability for subcooled boiling in downflow

    SciTech Connect

    Qureshi, Z. ); Barry, J.J.; Crowley, C.J. )

    1990-01-01

    A postulated loss-of-coolant accident (LOCA) scenario for the Savannah River Plant (SRP) production reactors involves a double-ended break of a reactor primary coolant pipe. The flow of coolant (D{sub 2}O) in the reactor may decrease in such an event. As the flow into the reactor decreases, boiling may occur, followed by dryout and failure of the fuel due to overheating. A typical SRP fuel assembly consists of multiple concentric tubes containing the fuel and target materials. Coolant passes through the annular passages in the assembly in downflow. Under normal operating conditions, the flow rate is maintained high enough to suppress or minimize subcooled boiling, i.e. the flow remains essentially single phase throughout. At high coolant flow rates, the flow is single phase or partially developed subcooled boiling, and the pressure drop decreases with decreasing flow rate. Here friction dominates the pressure gradient, and the flow is stable. Below a certain flow rate, however, pressure drop may increase with decreasing flow rate. This occurs when significant voids are produced by boiling, resulting in a large acceleration component to the pressure drop. The negative slope of the curve leads to an instability because the pressure drop cannot adjust to compensate -- the flow is driven to a lower value. Overheating of the channel may result. 15 refs., 14 figs.

  11. Subcooled flow film boiling across a horizontal cylinder. Part I. Analytical model

    SciTech Connect

    Chou, X.S.; Witte, L.C. )

    1995-02-01

    An analytical model of stable subcooled flow film boiling on the front of a horizontal cylinder and a model for the wake region downstream of the flow separation points were developed. The flow and temperature fields upstream of the separation points were represented by a 'local-similarity' solution obtained through a rigorous mathematical transformation. The transformed governing equations were solved numerically using a finite-difference scheme. Numerical solutions for the vapor layer thickness, the velocity, and the temperature fields were obtained for both the liquid and vapor layers. The results showed that the liquid boundary layer was thicker than the vapor film. Increases in the liquid subcooling and in the free-stream velocity decreased the vapor layer thickness. The influence of convection in the vapor layer is small yielding a near-linear temperature distribution. A two-dimensional vapor wake model was developed based on mass and energy balances. Numerical solutions, including the vapor layer thickness and the temperature field of the front part and the wake part, were matched at the separation points. The results showed that increases in the liquid subcooling decreased the vapor layer thickness. Heat transfer in the wake region can amount up to 20 percent of the heat transfer in the forward region and should not be neglected especially at high subcooling. 19 refs., 8 figs.

  12. Assessment of correlations and models for the prediction of CHF in water subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    Celata, G. P.; Cumo, M.; Mariani, A.

    1994-01-01

    The present paper provides an analysis of available correlations and models for the prediction of Critical Heat Flux (CHF) in subcooled flow boiling in the range of interest of fusion reactors thermal-hydraulic conditions, i.e. high inlet liquid subcooling and velocity and small channel diameter and length. The aim of the study was to establish the limits of validity of present predictive tools (most of them were proposed with reference to light water reactors (LWR) thermal-hydraulic studies) in the above conditions. The reference dataset represents almost all available data (1865 data points) covering wide ranges of operating conditions in the frame of present interest (0.1 less than p less than 8.4 MPa; 0.3 less than D less than 25.4 mm; 0.1 less than L less than 0.61 m; 2 less than G less than 90.0 Mg/sq m/s; 90 less than delta T(sub sub,in) less than 230 K). Among the tens of predictive tools available in literature four correlations (Levy, Westinghouse, modified-Tong and Tong-75) and three models (Weisman and Ileslamlou, Lee and Mudawar and Katto) were selected. The modified-Tong correlation and the Katto model seem to be reliable predictive tools for the calculation of the CHF in subcooled flow boiling.

  13. The effect of flowrate of subcooling water on boiling from downward-facing curved surface

    SciTech Connect

    Yefanov, A.D.; Kalyakin, S.G.; Grachev, N.S.; Grabezhnaya, V.A.

    1997-12-01

    Experimental results are presented on boiling from downward-facing curved surface. The investigations were carried out at a facility equipped with reactor pressure vessel simulator having the elliptic bottom of 400 mm inside diameter. The molten core (corium) was simulated by lead-bismuth alloy. The cooling of the simulator was produced by forced circulation of water along the annular gap of 16 mm between the pressure vessel and the shell. The results show that maximum heat fluxes for subcooled boiling slowly depend upon the position along the curved wall, and the transition from film boiling to the nucleate one take the origin at the lowermost position ({var_phi} = 0) spreading upon the surface. 14 refs., 7 figs.

  14. Flow Boiling Heat Transfer to Lithium Bromide Aqueous Solution in Subcooled Region

    NASA Astrophysics Data System (ADS)

    Kaji, Masao; Furukawa, Masahiro; Nishizumi, Takeharu; Ozaki, Shinji; Sekoguchi, Kotohiko

    A theoretical prediction model of the boiling heat transfer coefficient in the subcooled region for water and lithium bromide aqueous solution flowing in a rectangular channel is proposed. In the present heat transfer model, a heat flux is assumed to consist of both the forced convective and the boiling effect components. The forced convective component is evaluated from the empirical correlation of convective heat transfer coefficient for single-phase flow considering the effect of increase of liquid velocity due to net vapor generation. Empirical correlations for determining the heat flux due to the boiling effect and the quality at the onset point of net vapor generation are obtained from the data presented in the first report1). Agreement between the present theoretical prediction and the experimental data is satisfactorily good both for water and lithium bromide aqueous solution.

  15. Experimental study on subcooled flow boiling on heating surfaces with different thermal conductivities

    NASA Astrophysics Data System (ADS)

    Zou, Ling

    Subcooled flow boiling is generally characterized by high heat transfer capacity and low wall superheat, which is essential for cooling applications requiring high heat transfer rate, such as nuclear reactors and fossil boilers. In this study, subcooled flow boiling on copper and stainless steel heating surfaces was experimentally investigated from both macroscopic and microscopic points of view. Flow boiling heat flux and heat transfer coefficient were experimentally measured on both surfaces under different conditions, such as pressure, flow rate and inlet subcooling. Significant boiling heat transfer coefficient differences were found between the copper and the stainless steel heating surfaces. To explain the different flow boiling behaviors on these two heating surfaces, nucleation site density and bubble dynamics were visually observed and measured at different experimental conditions utilizing a high-speed digital video camera. These two parameters are believed to be keys in determining flow boiling heat flux. Wall superheat, critical cavity size and wall heat flux were used to correlate with nucleation site density data. Among them, wall heat flux shows the best correlation for eliminating both pressure and surface property effects. The observed nucleation site distribution shows a random distribution. When compared to the spatial Poisson distribution, similarity between them was found, while the measured nucleation site distribution is more uniform. From experimental observations, for the two surface materials investigated, which have similar surface wettability but sharply different thermal properties, bubble dynamics displayed fairly similar behavior. The obtained experimental results indicate that thermal conductivity of heating surface material plays an important role in boiling heat transfer. This is due to thermal conductivity having a significant impact on the lateral heat conduction at the heating surface and consequently temperature uniformity of the heating surface. A model was then developed and solved numerically for heat conduction at the heating surface when bubbles are present. Several key parameters which impact lateral heat conduction and surface temperature profile were studied. These parameters include material thermal conductivity, bubble size, heating surface thickness, etc. Numerical results show that, temperature profile on the heating surface tends to be more uniform and have a lower average value on a heating surface with higher thermal conductivity, which agrees well with the experimental observation.

  16. Influence of Test Tube Material on Subcooled Flow Boiling Critical Heat Flux in Short Vertical Tube

    NASA Astrophysics Data System (ADS)

    Hata, Koichi; Shiotsu, Masahiro; Noda, Nobuaki

    The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3 m/s), the inlet subcoolings (ΔTsub,in=48.6 to 154.7 K), the inlet pressure (Pin=735.2 to 969.0 kPa) and the increasing heat input (Q0 exp(t/τ), τ=10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tube of inner diameter (d=6 mm), heated length (L=66 mm) and L/d=11 with the inner surface of rough finished (Surface roughness, Ra=3.18 μm), the Cupro Nickel (Cu-Ni 30%) test tube of d=6 mm, L=60 mm and L/d=10 with Ra=0.18 μm and the Platinum (Pt) test tubes of d=3 and 6 mm, L=66.5 and 69.6 mm, and L/d=22.2 and 11.6 respectively with Ra=0.45 μm are used in this work. The CHF data for the SUS304, Cu-Ni 30% and Pt test tubes were compared with SUS304 ones for the wide ranges of d and L/d previously obtained and the values calculated by the authors' published steady state CHF correlations against outlet and inlet subcoolings. The influence of the test tube material on CHF is investigated into details and the dominant mechanism of subcooled flow boiling critical heat flux is discussed.

  17. Numerical Simulation on Subcooled Boiling Heat Transfer Characteristics of Water-Cooled W/Cu Divertors

    NASA Astrophysics Data System (ADS)

    Han, Le; Chang, Haiping; Zhang, Jingyang; Xu, Tiejun

    2015-04-01

    In order to realize safe and stable operation of a water-cooled W/Cu divertor under high heating condition, the exact knowledge of its subcooled boiling heat transfer characteristics under different design parameters is crucial. In this paper, subcooled boiling heat transfer in a water-cooled W/Cu divertor was numerically investigated based on computational fluid dynamic (CFD). The boiling heat transfer was simulated based on the Euler homogeneous phase model, and local differences of liquid physical properties were considered under one-sided high heating conditions. The calculated wall temperature was in good agreement with experimental results, with the maximum error of 5% only. On this basis, the void fraction distribution, flow field and heat transfer coefficient (HTC) distribution were obtained. The effects of heat flux, inlet velocity and inlet temperature on temperature distribution and pressure drop of a water-cooled W/Cu divertor were also investigated. These results provide a valuable reference for the thermal-hydraulic design of a water-cooled W/Cu divertor. supported by the National Magnetic Confinement Fusion Science Program of China (No. 2010GB104005), Funding of Jiangsu Innovation Program for Graduate Education (CXLX12_0170), the Fundamental Research Funds for the Central Universities of China

  18. An experimental study of subcooled flow film boiling across horizontal cylinders

    NASA Astrophysics Data System (ADS)

    Warrier, Gopinath Rama

    An experimental investigation of subcooled flow film boiling of Freon-113 over horizontal cylinders was undertaken. Experiments were performed for liquid velocities ranging from 0.78 m/s to 3.05 m/s, and for liquid subcooling ranging from 55.3°C to 72.6°C. Simultaneous wall temperature measurements were recorded using five miniature thermocouples embedded in the heater. A two-dimensional nonlinear inverse heat conduction problem (IHCP) was formulated based on the well-posed hyperbolic heat conduction equation, to estimate the surface heat flux, given measured heater temperatures. Based on the transient surface heat flux estimates and the measured wall temperature fluctuations, solid-liquid and pseudo contacts were identified. Contact parameters such as duration of contact, energy removed per contact, and wall temperature depression per contact were extracted from the data. The results showed that the contacts were not periodic. No clear trend was evident in the data. Correlation of the data was impossible due to the large scatter present. Boiling curves based on both "apparent" and "corrected" heat fluxes were compared to emphasize the importance of internal heat conduction in the heater. The effect of the thermal properties of the heater was investigated using computer simulations. It showed that the lava core was unaffected by short duration contacts. The lava core acts as an energy storage medium. Analysis of the nucleate-film boiling showed that the heater was capable of sustaining simultaneous nucleate and film boiling on its surface. An analytical flow film boiling model was also developed. Though this model does not include heat transfer in the wake of the heater and the effects of solid-liquid or pseudo contact, it is still a major improvement over all existing analytical models. However, these limitations of the model resulted in poor agreement between predicted wall temperatures and those experimentally measured.

  19. Heating surface materials effect on subcooled flow boiling heat transfer of R134a

    SciTech Connect

    Ling Zou; Barclay G. Jones

    2012-11-01

    In this study, subcooled flow boiling of R134a on copper (Cu) and stainless steel (SS) heating surfaces was experimentally investigated from both macroscopic and microscopic points of view. By utilizing a high-speed digital camera, bubble growth rate, bubble departure size, and nucleation site density, were able to be observed and analyzed from the microscopic point of view. Macroscopic characteristics of the subcooled flow boiling, such as heat transfer coefficient, were able to be measured as well. Experimental results showed that there are no obvious difference between the copper and the stainless surface with respect to bubble dynamics, such as contact angle, growth rate and departure size. On the contrary, the results clearly showed a trend that the copper surface had a better performance than the stainless steel surface in terms of heat transfer coefficient. It was also observed that wall heat fluxes on both surfaces were found highly correlated with nucleation site density, as bubble hydrodynamics are similar on these two surfaces. The difference between these two surfaces was concluded as results of different surface thermal conductivities.

  20. Physical modeling and numerical simulation of subcooled boiling in one- and three-dimensional representation of bundle geometry

    SciTech Connect

    Bottoni, M.; Lyczkowski, R.; Ahuja, S.

    1995-07-01

    Numerical simulation of subcooled boiling in one-dimensional geometry with the Homogeneous Equilibrium Model (HEM) may yield difficulties related to the very low sonic velocity associated with the HEM. These difficulties do not arise with subcritical flow. Possible solutions of the problem include introducing a relaxation of the vapor production rate. Three-dimensional simulations of subcooled boiling in bundle geometry typical of fast reactors can be performed by using two systems of conservation equations, one for the HEM and the other for a Separated Phases Model (SPM), with a smooth transition between the two models.

  1. A critical review of predictive models for the onset of significant void in forced-convection subcooled boiling

    SciTech Connect

    Dorra, H.; Lee, S.C.; Bankoff, S.G.

    1993-06-01

    This predictive models for the onset of significant void (OSV) in forced-convection subcooled boiling are reviewed and compared with extensive data. Three analytical models and seven empirical correlations are considered in this review. These models and correlations are put onto a common basis and are compared, again on a common basis, with a variety of data. The evaluation of their range of validity and applicability under various operating conditions are discussed. The results show that the correlations of Saha-Zuber seems to be the best model to predict OSV in vertical subcooled boiling flow.

  2. A combined photographic/thermographic study of highly subcooled flow boiling in a narrow channel

    NASA Astrophysics Data System (ADS)

    Ozer, Arif Bilal

    Minichannels (those with channel spacing near 1 mm) offer an attractive scale range for technological applications of two-phase cooling. They are small enough to create large heat fluxes, but large enough to remove significant quantities of heat, and they do not present the same degree of fouling and maintenance issues anticipated for applications of true micro-scale channels. This study applies liquid crystal thermography in concert with high-speed video imaging of a two-phase flow field to study highly subcooled bubbly flow within a millimeter-scale channel. The experiments were conducted with a high-aspect-ratio (12x23 mm) rectangular, horizontal channel with one wide wall forming a uniform-heat-generation boundary and the other designed for optical access to the flow field. By using a thermochromic liquid crystal coating on the uniform-heat-generation boundary, wall temperature variations were obtained and the heat transfer characteristics were investigated. The experiments were focused on high inlet subcooling, typically 15--50 °C. The test surface temperature increases downstream until boiling initiates when a group of nucleation sites activate at a "boiling front." It is commonly thought that cooling of the surface downstream of the front would be dominated by active nucleation sites. However, few active sites were observed downstream of those near the current position of the boiling front. This observation provides strong evidence that it is the action of bubbles sliding in the confined channel that causes the enhancement of heat transfer, not the extensive nucleation of bubbles. A quenching/diffusion analytical model was developed to describe the heat process associated with sliding bubbles. The model is based on a transient conduction hypothesis. It is able to capture the elevated heat transfer rates measured in the channel without the need to consider nucleate boiling from the surface or microlayer evaporation from the sliding bubbles. Bubble speed and size enter the model through a Fourier number associated with the bubble passage frequency. The insight gathered from this experimental investigation provides the basis for a better understanding of the physics of subcooled bubbly flow in minichannels, and this understanding should lead to new models of this regime.

  3. Flow regimes and mechanistic modeling of critical heat flux under subcooled flow boiling conditions

    NASA Astrophysics Data System (ADS)

    Le Corre, Jean-Marie

    Thermal performance of heat flux controlled boiling heat exchangers are usually limited by the Critical Heat Flux (CHF) above which the heat transfer degrades quickly, possibly leading to heater overheating and destruction. In an effort to better understand the phenomena, a literature review of CHF experimental visualizations under subcooled flow boiling conditions was performed and systematically analyzed. Three major types of CHF flow regimes were identified (bubbly, vapor clot and slug flow regime) and a CHF flow regime map was developed, based on a dimensional analysis of the phenomena and available data. It was found that for similar geometric characteristics and pressure, a Weber number (We)/thermodynamic quality (x) map can be used to predict the CHF flow regime. Based on the experimental observations and the review of the available CHF mechanistic models under subcooled flow boiling conditions, hypothetical CHF mechanisms were selected for each CHF flow regime, all based on a concept of wall dry spot overheating, rewetting prevention and subsequent dry spot spreading. It is postulated that a high local wall superheat occurs locally in a dry area of the heated wall, due to a cyclical event inherent to the considered CHF two-phase flow regime, preventing rewetting (Leidenfrost effect). The selected modeling concept has the potential to span the CHF conditions from highly subcooled bubbly flow to early stage of annular flow. A numerical model using a two-dimensional transient thermal analysis of the heater undergoing nucleation was developed to mechanistically predict CHF in the case of a bubbly flow regime. In this type of CHF two-phase flow regime, the high local wall superheat occurs underneath a nucleating bubble at the time of bubble departure. The model simulates the spatial and temporal heater temperature variations during nucleation at the wall, accounting for the stochastic nature of the boiling phenomena. The model has also the potential to evaluate the post-DNB heater temperature up to the point of heater melting. Validation of the proposed model was performed using detailed measured wall boiling parameters near CHF, thereby bypassing most needed constitutive relations. It was found that under limiting nucleation conditions; a peak wall temperature at the time of bubble departure can be reached at CHF preventing wall cooling by quenching. The simulations show that the resulting dry patch can survive the surrounding quenching event, preventing further nucleation and leading to a fast heater temperature increase. For more practical applications, the model was applied at known CHF conditions in simple geometry coupled with one-dimensional and three-dimensional (CFD) codes. It was found that, in the case where CHF occurs under bubbly flow conditions, the local wall superheat underneath nucleating bubbles is predicted to reach the Leidenfrost temperature. However, a better knowledge of statistical variations in wall boiling parameters would be necessary to correctly capture the CHF trends with mass flux (or Weber number). In addition, consideration of relevant parameter influences on the Leidenfrost temperature and consideration of interfacial microphysics at the wall would allow improved simulation of the wall rewetting prevention and subsequent dry patch spreading.

  4. Prediction of the onset of significant void in transient subcooled flow boiling

    SciTech Connect

    Lee, S.C.; Bankoff, S.G.

    1993-06-01

    A new model to predict the onset of significant void (OSV) in transient subcooled flow boiling has been developed. The model is based upon the influence on vapor bubble departure of the single-phase temperature profile. The steady-state result of the present model was compared to the experimental data of Whittle and Forgan and Dougherty, et al., showing an excellent agreement. The model was then employed in a transient analysis of OSV for vertical downwards turbulent flow to predict whether OSV takes place. The condition for OSV to occur in transient flow situations was also predicted by this model. Two modes for pressure gradient change inside the channel are considered in the present study: step change and ramp change. The calculations were made for various combinations of the flow operating condition and the mode of pressure drop change.

  5. Flow Boiling Heat Transfer to Lithium Bromide Aqueous Solution in Subcooled Region

    NASA Astrophysics Data System (ADS)

    Furukawa, Masahiro; Kaji, Masao; Nishizumi, Takeharu; Ozaki, Shinji; Sekoguchi, Kotohiko

    To improve the thermal performance of high temperature generator of absorption chiller/heater, heat transfer characteristics of flow boiling of lithium bromide aqueous solution in the subcooled region were experimentally investigated. Experiments were made for water and lithium bromide aqueous solution flowing in a rectangular channel (5 mm × 20 mm cross section) with one side wall heated. Boiling onset quality of lithium bromide aqueous solution is greater than that of water. The heat transfer coefficient of lithium bromide aqueous solution is about a half of that of water under the same experimental conditions of inlet velocity and heat flux. The experimental data of heat transfer coefficient for water are compared with the empirical correlation of Thom et al.11) and a fairly good agreement is obtained. The predictive calculations by the method of Sekoguchi et al.12) are compared with the data for water and lithium bromide aqueous solution. Agreement between them is good for water, while the results for lithium bromide aqueous solution are not satisfactory.

  6. Dependence of Vapor Void Fraction on Fundamental Bubble Parameters in Subcooled Flow Boiling

    SciTech Connect

    Hayato Kubota; Tatsuhiro Ishida; Tomio Okawa; Isao Kataoka; Michitsugu Mori

    2006-07-01

    A visual study of water subcooled flow boiling was conducted to clarify the mechanism of triggering the net vapor generation (NVG). The test section was a transparent sapphire grass tube of 20 mm in inside diameter; a high-speed camera was used to capture the behavior of vapor bubbles. In the present experiments, the vapor void fraction in the heated tube was expressed as the function of the following bubble parameters: nucleation site density, frequency of bubble release, bubble lifetime, and bubble size. Among these four bubble parameters, the bubble size had a particularly strong influence on the vapor void fraction: the void fraction was approximately proportional to the forth power of mean bubble diameter. Consequently, mean bubble diameter should be large enough for the vapor void fraction to increase rapidly with the wall heat flux. In low flowrate experiments, bubbles generated at nucleation sites were relatively large at the onset of nucleate boiling (ONB). The heat flux at ONB hence appeared the reasonable approximation of that at NVG. Whereas, in high flowrate experiments, bubbles were small at ONB and much higher heat flux was necessary to obtain large bubbles. Thus, the heat flux required to trigger NVG was much higher than that at ONB. It was concluded in the present experimental conditions that accurate evaluation of mean bubble diameter was of significant importance in predicting the onset of net vapor generation. (authors)

  7. Complete Numerical Simulation of Subcooled Flow Boiling in the Presence of Thermal and Chemical Interactions

    SciTech Connect

    V.K. Dhir

    2003-04-28

    At present, guidelines for fuel cycle designs to prevent axial offset anomalies (AOA) in pressurized water reactor (PWR) cores are based on empirical data from several operating reactors. Although the guidelines provide an ad-hoc solution to the problem, a unified approach based on simultaneous modeling of thermal-hydraulics, chemical, and nuclear interactions with vapor generation at the fuel cladding surface does not exist. As a result, the fuel designs are overly constrained with a resulting economic penalty. The objective of present project is to develop a numerical simulation model supported by laboratory experiments that can be used for fuel cycle design with respect to thermal duty of the fuel to avoid economic penalty, as well as, AOA. At first, two-dimensional numerical simulation of the growth and departure of a bubble in pool boiling with chemical interaction is considered. A finite difference scheme is used to solve the equations governing conservation of mass, momentum, energy, and species concentration. The Level Set method is used to capture the evolving liquid-vapor interface. A dilute aqueous boron solution is considered in the simulation. From numerical simulations, the dynamic change in concentration distribution of boron during the bubble growth shows that the precipitation of boron can occur near the advancing and receding liquid-vapor interface when the ambient boron concentration level is 3,000 ppm by weight. Secondly, a complete three-dimensional numerical simulation of inception, growth and departure of a single bubble subjected to forced flow parallel to the heater surface was developed. Experiments on a flat plate heater with water and with boron dissolved in the water were carried out. The heater was made out of well-polished silicon wafer. Numbers of nucleation sites and their locations were well controlled. Bubble dynamics in great details on an isolated nucleation site were obtained while varying the wall superheat, liquid subcooling and flow velocity parametrically. Concentration variation of boron near the liquid-vapor interface was detected successfully with a newly developed miniature concentration sensor. The measured concentration variations at different radial locations from the center of cavity have the same trend as given by the numerical simulations. The deposition of boron was found near the nucleation site on the heater surface, which validates the numerical simulation. Subcooled flow boiling experiments at three pressures were performed on a nine-rod bundle with water and with boron dissolved in the water. The test runs were conducted with a wide range of mass fluxes (186 to 2800 kg/m2s) and heat fluxes (1.0 to 30.0 W/ cm2). Not only the variables required to develop mechanistic models for subcooled flow boiling were measured, but also the crud formation during boiling and its effect on the heat transfer process were investigated. (B204)

  8. Effect of rolling motion on critical heat flux for subcooled flow boiling in vertical tube

    SciTech Connect

    Hwang, J. S.; Park, I. U.; Park, M. Y.; Park, G. C.

    2012-07-01

    This paper presents defining characteristics of the critical heat flux (CHF) for the boiling of R-134a in vertical tube operation under rolling motion in marine reactor. It is important to predict CHF of marine reactor having the rolling motion in order to increase the safety of the reactor. Marine Reactor Moving Simulator (MARMS) tests are conducted to measure the critical heat flux using R-134a flowing upward in a uniformly heated vertical tube under rolling motion. MARMS was rotated by motor and mechanical power transmission gear. The CHF tests were performed in a 9.5 mm I.D. test section with heated length of 1 m. Mass fluxes range from 285 to 1300 kg m{sup -2}s{sup -1}, inlet subcooling from 3 to 38 deg. C and outlet pressures from 13 to 24 bar. Amplitudes of rolling range from 15 to 40 degrees and periods from 6 to 12 sec. To convert the test conditions of CHF test using R-134a in water, Katto's fluid-to-fluid modeling was used in present investigation. A CHF correlation is presented which accounts for the effects of pressure, mass flux, inlet subcooling and rolling angle over all conditions tested. Unlike existing transient CHF experiments, CHF ratio of certain mass flux and pressure are different in rolling motion. For the mass fluxes below 500 kg m{sup -2}s{sup -1} at 13, 16 (region of relative low mass flux), CHF ratio was decreased but was increased above that mass flux (region of relative high mass flux). Moreover, CHF tend to enhance in entire mass flux at 24 bar. (authors)

  9. SUBCOOLING DETECTOR

    DOEpatents

    McCann, J.A.

    1963-12-17

    A system for detecting and measuring directly the subcooling margin in a liquid bulk coolant is described. A thermocouple sensor is electrically heated, and a small amount of nearly stagnant bulk coolant is heated to the boiling point by this heated thermocouple. The sequential measurement of the original ambient temperature, zeroing out this ambient temperature, and then measuring the boiling temperature of the coolant permits direct determination of the subcooling margin of the ambient liquid. (AEC)

  10. Critical heat flux of subcooled flow boiling in swirl tubes relevant to high-heat-flux components

    SciTech Connect

    Inasaka, Fujio; Nariai, Hideki

    1996-07-01

    It is necessary to accurately determine the critical heat flux (CHF) of cooling systems used in fusion reactors. Currently, sufficiently accurate CHF correlations for one-sided heating have not been established. A design method for subcooled boiling cooling systems using swirl tubes is described. From a review of existing work under uniform heating conditions, the correlations of Gunther and Nariai-Inasaka are recommended for smooth and swirl flow, respectively. The effects of thermal conductivity and geometry of the cooling sections on both the nouniformity factor and the peaking factor were investigated by solving a heat conduction equation. For swirl flow under one-sided heating, the CHF multiplier increases with the increasing nonuniformity factor. Design criteria for subcooled boiling swirl-tube cooling systems are presented. 33 refs., 13 figs., 4 tabs.

  11. A Study on Bubble Departure and Bubble Lift-Off in Sub-Cooled Nucleate Boiling Flows

    SciTech Connect

    Wu, Wen; Chen, Peipei; Jones, Barclay G.; Newell, Ty A.

    2006-07-01

    This research examines bubble departure and bubble lift-off phenomena under subcooled nucleate boiling condition, using a high fidelity digital imaging apparatus. Refrigerant R- 134a is chosen as a simulant fluid due to its merits of having smaller surface tension, reduced latent heat, and lower boiling temperature than water. Images at frame rates up to 4000 frames/s were obtained with varying experimental parameters e.g. pressure, inlet sub-cooled level, and flow rate, etc., showing characteristics of bubble behavior under different conditions. Bubble size and position information was calculated via Canny's algorithm for edge detection and Fitzgibbon's algorithm for ellipse fitting. Bubble departure and lift-off radiuses were obtained and compared with existing bubble forces and detachment models proposed by Thorncroft et al., with good agreement observed. (authors)

  12. Numerical Analysis of Nucleate Boiling on High Heat-Flux and High Subcooling Condition for Reactivity Initiation Accident

    SciTech Connect

    Heo, S.; Koshizuka, S.; Oka, Y.

    2002-07-01

    This paper shows the numerical simulation study on the growth of the bubble in the transient pool boiling using MPS-MAFL method. The growth process of a bubble with the different initial radii is calculated in a high heat-flux and high subcooling condition expected in nuclear reactor core during RIA. The smaller initial radius is, the earlier the growth starts. The initial bubble radius has little effect on the growth initiation time and the bubble departure radius. (authors)

  13. Enhancement of CHF water subcooled flow boiling in tubes using helically coiled wires

    NASA Astrophysics Data System (ADS)

    Celata, G. P.; Cumo, M.; Mariani, A.

    1994-01-01

    The present paper reports the results of an experimental investigation about the occurrence of the critical heat flux (CHF) in subcooled flow boiling of water, carried out to ascertain the influence of thermal hydraulic parameters on CHF under conditions typical of themronuclear fusion divertor thermal hydraulic design. Helically coiled wires were used as turbulence promoters to enhance the CHF with respect to the smooth channel. Geometric characteristics of stainless steel 304 Type test sections were: 6.0 and 8.0 mm i.d., 0.25 mm wal thickness, 0.1 and 0.15 m heated length, horizontal and vertical (upflow) position. Test sections were uniformly heated using d.c. current. A maximum CHF of about 30 MW/sq m was reached with smooth tubes under the following conditions: T(sub in) = 30 C, p = 4.6 MPa, u = 10 m/s, D = 8.0 mm, L = 0.1 m. Helically coiled wires (d = 1.0 mm, pitch = 20.0 mm) allowed an increase of the CHF up to 50%, with reference to smooth channels, coupled with a moderate increase of pressure drop (down to 25%). Pressure revealed a negative effect on the efficiency of turbulence promoters. No observable influence of the channel orientation was detected.

  14. Modeling and Thermal Performance Evaluation of Porous Curd Layers in Sub-Cooled Boiling Region of PWRs and Effects of Sub-Cooled Nucleate Boiling on Anomalous Porous Crud Deposition on Fuel Pin Surfaces

    SciTech Connect

    Barclay Jones

    2005-06-27

    A significant number of current PWRs around the world are experiencing anomalous crud deposition in the sub-cooled region of the core, resulting in an axial power shift or Axial Offset Anomaly (AOA), a condition that continues to elude prediction of occurrence and thermal/neutronic performance. This creates an operational difficulty of not being able to accurately determine power safety margin. In some cases this condition has required power ''down rating'' by as much as thirty percent and the concomitant considerable loss of revenue for the utility. This study examines two aspects of the issue: thermal performance of crud layer and effect of sub-cooled nucleate boiling on the solute concentration and its influence on initiation of crud deposition/formation on fuel pin surface.

  15. Numerical investigation of water-based nanofluid subcooled flow boiling by three-phase Euler-Euler, Euler-Lagrange approach

    NASA Astrophysics Data System (ADS)

    Valizadeh, Ziba; Shams, Mehrzad

    2015-09-01

    A numerical scheme for simulating the subcooled flow boiling of water and water-based nanofluids was developed. At first, subcooled flow boiling of water was simulated by the Eulerian multiphase scheme. Then the simulation results were compared with previous experimental data and a good agreement was observed. In the next step, subcooled flow boiling of water-based nanofluid was modeled. In the previous studies in this field, the nanofluid assumed as a homogeneous liquid and the two-phase scheme was used to simulate its boiling. In the present study, a new scheme was used to model the nanofluid boiling. In this scheme, to model the nanofluid flow boiling, three phases, water, vapor and nanoparticles were considered. The Eulerian-Eulerian approach was used for modeling water-vapor interphase and Eulerian-Lagrangian scheme was selected to observe water-nanoparticle interphase behavior. The results from the nanofluid boiling modeling were validated with an experimental investigation. The results of the present work and experimental data were consistent. The addition of 0.0935 % volume fraction of nanoparticles in pure liquid boiling flow increases the vapor volume fraction at the outlet almost by 40.7 %. The results show the three-phase model is a good approach to simulate the nanofluid boiling flow.

  16. Validation and Calibration of Nuclear Thermal Hydraulics Multiscale Multiphysics Models - Subcooled Flow Boiling Study

    SciTech Connect

    Anh Bui; Nam Dinh; Brian Williams

    2013-09-01

    In addition to validation data plan, development of advanced techniques for calibration and validation of complex multiscale, multiphysics nuclear reactor simulation codes are a main objective of the CASL VUQ plan. Advanced modeling of LWR systems normally involves a range of physico-chemical models describing multiple interacting phenomena, such as thermal hydraulics, reactor physics, coolant chemistry, etc., which occur over a wide range of spatial and temporal scales. To a large extent, the accuracy of (and uncertainty in) overall model predictions is determined by the correctness of various sub-models, which are not conservation-laws based, but empirically derived from measurement data. Such sub-models normally require extensive calibration before the models can be applied to analysis of real reactor problems. This work demonstrates a case study of calibration of a common model of subcooled flow boiling, which is an important multiscale, multiphysics phenomenon in LWR thermal hydraulics. The calibration process is based on a new strategy of model-data integration, in which, all sub-models are simultaneously analyzed and calibrated using multiple sets of data of different types. Specifically, both data on large-scale distributions of void fraction and fluid temperature and data on small-scale physics of wall evaporation were simultaneously used in this work’s calibration. In a departure from traditional (or common-sense) practice of tuning/calibrating complex models, a modern calibration technique based on statistical modeling and Bayesian inference was employed, which allowed simultaneous calibration of multiple sub-models (and related parameters) using different datasets. Quality of data (relevancy, scalability, and uncertainty) could be taken into consideration in the calibration process. This work presents a step forward in the development and realization of the “CIPS Validation Data Plan” at the Consortium for Advanced Simulation of LWRs to enable quantitative assessment of the CASL modeling of Crud-Induced Power Shift (CIPS) phenomenon, in particular, and the CASL advanced predictive capabilities, in general. This report is prepared for the Department of Energy’s Consortium for Advanced Simulation of LWRs program’s VUQ Focus Area.

  17. Effects of ultrasonic vibration on subcooled pool boiling critical heat flux

    NASA Astrophysics Data System (ADS)

    Jeong, J. H.; Kwon, Y. C.

    2006-10-01

    The effects of ultrasonic vibration on critical heat flux (CHF) have been experimentally investigated under natural convection condition. Flat bakelite plates coated with thin copper layer and distilled water are used as heated specimens and working fluid, respectively. Measurements of CHF on flat heated surface were made with and without ultrasonic vibration applied to working fluid. An inclination angle of the heated surface and water subcooling are varied as well. Examined water subcoolings are 5°C, 20°C, 40°C and the angles are 0°, 10°, 20°, 45°, 90°, 180°. The measurements show that ultrasonic wave applied to water enhances CHF and its extent is dependent upon inclination angle as well as water subcooling. The rate of increase in CHF increases with an increase in water subcooling while it decreases with an increase in inclination angle. Visual observation shows that the cause of CHF augmentation is closely related with the dynamic behaviour of bubble generation and departure in acoustic field.

  18. Subcooled freon-11 flow boiling in top-heated finned coolant channels with and without a twisted tape

    NASA Technical Reports Server (NTRS)

    Smith, Alvin; Boyd, Ronald D., Sr.

    1989-01-01

    An experimental study was conducted in top-heated finned horizontal tubes to study the effect of enhancement devices on flow boiling heat transfer in coolant channels. The objectives are to examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for circular coolant channels with spiral finned walls and/or spiral fins with a twisted tape, and improve the data reduction technique of a previous investigator. The working fluid is freon-11 with an inlet temperature of 22.2 C (approximately 21 C subcooling). The coolant channel's exit pressure and mass velocity are 0.19 M Pa (absolute) and 0.21 Mg/sq. ms, respectively. Two tube configurations were examined; i.e., tubes had either 6.52 (small pitch) or 4.0 (large pitch) fins/cm of the circumferential length (26 and 16 fins, respectively). The large pitch fins were also examined with a twisted tape insert. The inside nominal diameter of the copper channels at the root of the fins was 1.0 cm. The results show that by adding enhancement devices, boiling occurs almost simultaneously at all axial locations. The case of spiral fins with large pitch resulted in larger mean (circumferentially averaged) heat transfer coefficients, h sub m, at all axial locations. Finally, when twisted tape is added to the tube with large-pitched fins, the power required for the onset of boiling is reduced at all axial and circumferential locations.

  19. A Digital Photographic Study on Nucleate Boiling in Subcooled Flow for Water and Refrigerant 134a Fluids

    SciTech Connect

    In Cheol Bang; Soon Heung Chang; Won-Pil Baek

    2002-07-01

    The behavior of near-wall bubbles in subcooled flow boiling has been investigated photographically for water flow in vertical, one-side heated and rectangular channels at mass fluxes of 500, 1500, 2000 kg/m{sup 2}s under atmospheric pressure and for R134a in channels of the same kind at mass fluxes of 1000, 2000 kg/m{sup 2}s under 7 bar. Digital photographic techniques are used for the visualization, which are rapidly advanced in recent. Primary attention is given to the bubble coalescence phenomenon and the structure of the near-wall bubble layer. At subcooled and low-quality conditions of both fluids, discrete attached bubbles, sliding bubbles, small coalesced bubbles and large coalesced bubbles or vapor clots are observed on the heated surface as the heat flux is increased from a low value. Particularly for R134a, vapor remnants below discrete bubble on the heating surface are observed. Nucleation site density increases with the increases in heat flux and channel-averaged enthalpy, while discrete bubbles coalesce and form large bubbles, resulting in large vapor clots. Waves formed on the surface of the vapor clots are closely related to Helmholtz instability. At sufficiently high heat fluxes, three characteristic layers were observed in the heated channel: (a) a superheated liquid layer with small bubbles attached on the heated wall, (b) a flowing bubble layer consisting of large coalesced bubbles over the superheated liquid layer, and (c) the liquid core over the flowing bubble layer. (authors)

  20. Experimental Investigation on the Effects of Coolant Concentration on Sub-Cooled Boiling and Crud Deposition on Reactor Cladding at Prototypical PWR Operating Conditions

    SciTech Connect

    Schultis, J., Kenneth; Fenton, Donald, L.

    2006-10-20

    Increasing demand for energy necessitates nuclear power units to increase power limits. This implies significant changes in the design of the core of the nuclear power units, therefore providing better performance and safety in operations. A major hindrance to the increase of nuclear reactor performance especially in Pressurized Deionized water Reactors (PWR) is Axial Offset Anomaly (AOA)--the unexpected change in the core axial power distribution during operation from the predicted distribution. This problem is thought to be occur because of precipitation and deposition of lithiated compounds like boric acid (H{sub 2}BO{sub 3}) and lithium metaborate (LiBO{sub 2}) on the fuel rod cladding. Deposited boron absorbs neutrons thereby affecting the total power distribution inside the reactor. AOA is thought to occur when there is sufficient build-up of crud deposits on the cladding during subcooled nucleate boiling. Predicting AOA is difficult as there is very little information regarding the heat and mass transfer during subcooled nucleate boiling. An experimental investigation was conducted to study the heat transfer characteristics during subcooled nucleate boiling at prototypical PWR conditions. Pool boiling tests were conducted with varying concentrations of lithium metaborate (LiBO{sub 2}) and boric acid (H{sub 2}BO{sub 3}) solutions in deionized water. The experimental data collected includes the effect of coolant concentration, subcooling, system pressure and heat flux on pool the boiling heat transfer coefficient. The analysis of particulate deposits formed on the fuel cladding surface during subcooled nucleate boiling was also performed. The results indicate that the pool boiling heat transfer coefficient degrades in the presence of boric acid and lithium metaborate compared to pure deionized water due to lesser nucleation. The pool boiling heat transfer coefficients decreased by about 24% for 5000 ppm concentrated boric acid solution and by 27% for 5000 ppm lithium metaborate solution respectively at the saturation temperature for 1000 psi (68.9 bar) coolant pressure. Boiling tests also revealed the formation of fine deposits of boron and lithium on the cladding surface which degraded the heat transfer rates. The boron and lithium metaborate precipitates after a 5 day test at 5000 ppm concentration and 1000 psi (68.9 bar) operating pressure reduced the heat transfer rate 21% and 30%, respectively for the two solutions.

  1. Heat transfer performance of engine coolants under sub-cooled boiling conditions

    SciTech Connect

    Bhowmick, S.; Branchi, C.; McAssey, E.V. Jr.; Gollin, M.

    1996-12-31

    An experimental program has been conducted to evaluate the heat transfer performance of two engine cooling fluid mixtures, propylene-glycol/water and ethylene-glycol/water. These tests were performed under conditions closely simulating normal engine operation. For both mixtures, results were obtained over a range of heat transfer regimes from single phase convection to saturated flow boiling. Tests showed that propylene-glycol/water and ethylene-glycol/water have very similar heat transfer performances. Performance is defined as the steady state wall temperature maintained for a given surface heat flux and test section inlet velocity. For the lowest velocity tested, the test section experienced saturated boiling over approximately one-half of its heated length. The experimental results were also compared to analytical predictions based upon the Chen correlation. At higher fluxes, the analytical methods under-predicted the test section wall temperature.

  2. Experimental study of static flow instability in subcooled flow boiling in parallel channels

    SciTech Connect

    Siman-Tov, M.; Felde, D.K.; McDuffee, J.L.; Yoder, G.L.

    1995-12-31

    Experimental data for static flow instability or flow excursion (FE) at conditions applicable to the Advanced Neutron Source Reactor are very limited. A series of FE tests with light water flowing vertically upward was completed covering a local exit heat flux range of 0.7--18 MW/m{sup 2}, exit velocity range of 2.8--28.4 m/s, exit pressure range of 0.117--1.7 MPa, and inlet temperature range of 40-- 50{degrees}C. Most of the tests were performed in a ``stiff`` (constant flow) system where the instability threshold was detected through the minimum of the pressure-drop curve. A few tests were also conducted using as ``soft`` (constant pressure drop) a system as possible to secure a true FE phenomenon (actual secondary burnout). True critical heat flux experiments under similar conditions were also conducted using a stiff system. The FE data reported in this study considerably extend the velocity range of data presently available worldwide, most of which were obtained at velocities below 10 m/s. The Saha and Zuber correlation had the best fit with the data out of the three correlations compared. However, a modification was necessary to take into account the demonstrated dependence of the St and Nu numbers on subcooling levels, especially in the low subcooling regime. Comparison of Thermal Hydraulic Test Loop (THTL) data, as well as extensive data from other investigators, led to a proposed modification to the Saha and Zuber correlation for onset of significant void, applied to FE prediction. The mean and standard deviation of the THTL data were 0.95 and 15%, respectively, when comparing the THTL data with the original Saha and Zuber correlation, and 0.93 and 10% when comparing them with the modification. Comparison with the worldwide database showed a mean and standard deviation of 1.37 and 53%, respectively, for the original Saha and Zuber correlation and 1.0 and 27% for the modification.

  3. Subcooled Pool Boiling Heat Transfer Mechanisms in Microgravity: Terrier-improved Orion Sounding Rocket Experiment

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; Benton, John; Kucner, Robert

    2000-01-01

    A microscale heater array was used to study boiling in earth gravity and microgravity. The heater array consisted of 96 serpentine heaters on a quartz substrate. Each heater was 0.27 square millimeters. Electronic feedback loops kept each heater's temperature at a specified value. The University of Maryland constructed an experiment for the Terrier-Improved Orion sounding rocket that was delivered to NASA Wallops and flown. About 200 s of high quality microgravity and heat transfer data were obtained. The VCR malfunctioned, and no video was acquired. Subsequently, the test package was redesigned to fly on the KC-135 to obtain both data and video. The pressure was held at atmospheric pressure and the bulk temperature was about 20 C. The wall temperature was varied from 85 to 65 C. Results show that gravity has little effect on boiling heat transfer at wall superheats below 25 C, despite vast differences in bubble behavior between gravity levels. In microgravity, a large primary bubble was surrounded by smaller bubbles, which eventually merged with the primary bubble. This bubble was formed by smaller bubbles coalescing, but had a constant size for a given superheat, indicating a balance between evaporation at the base and condensation on the cap. Most of the heaters under the bubble indicated low heat transfer, suggesting dryout at those heaters. High heat transfer occurred at the contact line surrounding the primary bubble. Marangoni convection formed a "jet" of fluid into the bulk fluid that forced the bubble onto the heater.

  4. Application of high-speed digital holographic interferometry for the analysis of temperature distributions and velocity fields in subcooled flow boiling

    NASA Astrophysics Data System (ADS)

    Bloch, Gregor; Kuczaty, Julian; Sattelmayer, Thomas

    2014-02-01

    Holographic interferometry can be used to visualize density fields in fluids, and thus give insight into temperature distributions in flows. A fully digital reconstruction technique for holographic interferograms is presented that allows to create high-speed interferometric recordings and gives time-resolved information about heat transfer processes. The technique can also be used for a sequential (image to image) analysis of the recordings, which offers higher sensitivity and fewer errors due to optical impurities. Experiments are conducted with a vertical flow boiling channel with one heated wall, using a low boiling fluorocarbon as working liquid in regimes of steady-state nucleate boiling at critical heat flux (CHF), steady-state film boiling and CHF transient. Recording frequencies are up to 7,000 fps. The technique is used to analyze boiling processes at different fluid subcoolings with and without added turbulence. The results give enhanced insight into the temperature distributions, effects of different flow inserts and mechanisms of heat transfer in flow boiling at high heat fluxes. Furthermore, a velocimetric application of the technique is presented using cross-correlation for tracing of density gradients both in boiling and unheated flows. This application gives insight to the velocity distributions in the liquid surrounding the vapor layer. The results show good comparison to particle image velocimetry measurements for the same setup.

  5. An experimental study on sub-cooled flow boiling CHF of R134a at low pressure condition with atmospheric pressure (AP) plasma assisted surface modification

    SciTech Connect

    Kim, Seung Jun; Zou, Ling; Jones, Barclay G.

    2015-02-01

    In this study, sub-cooled flow boiling critical heat flux tests at low pressure were conducted in a rectangular flow channel with one uniformly heated surface, using simulant fluid R-134a as coolant. The experiments were conducted under the following conditions: (1) inlet pressure (P) of 400-800 kPa, (2) mass flux (G) of 124-248 kg/m2s, (3) inlet sub-cooling enthalpy (ΔHi) of 12~ 26 kJ/kg. Parametric trends of macroscopic system parameters (G, P, Hi) were examined by changing inlet conditions. Those trends were found to be generally consistent with previous understandings of CHF behavior at low pressure condition (i.e. reduced pressure less than 0.2). A fluid-to-fluid scaling model was utilized to convert the test data obtained with the simulant fluid (R-134a) into the prototypical fluid (water). The comparison between the converted CHF of equivalent water and CHF look-up table with same operation conditions were conducted, which showed good agreement. Furthermore, the effect of surface wettability on CHF was also investigated by applying atmospheric pressure plasma (AP-Plasma) treatment to modify the surface characteristic. With AP-Plasma treatment, the change of microscopic surface characteristic was measured in terms of static contact angle. The static contact angle was reduced from 80° on original non-treated surface to 15° on treated surface. An enhancement of 18% on CHF values under flow boiling conditions were observed on AP-Plasma treated surfaces compared to those on non-treated heating surfaces.

  6. Boils

    MedlinePlus

    ... the boil is very bad or comes back. Antibacterial soaps and creams cannot help much once a ... following may help prevent the spread of infection: Antibacterial soaps Antiseptic (germ-killing) washes Keeping clean (such ...

  7. BOILING REACTORS

    DOEpatents

    Untermyer, S.

    1962-04-10

    A boiling reactor having a reactivity which is reduced by an increase in the volume of vaporized coolant therein is described. In this system unvaporized liquid coolant is extracted from the reactor, heat is extracted therefrom, and it is returned to the reactor as sub-cooled liquid coolant. This reduces a portion of the coolant which includes vaporized coolant within the core assembly thereby enhancing the power output of the assembly and rendering the reactor substantially self-regulating. (AEC)

  8. Local jet impingement boiling heat transfer with R113

    NASA Astrophysics Data System (ADS)

    Zhou, D. W.; Ma, C. F.

    An experimental study was performed to characterize the boiling heat transfer of impinging circular submerged jets on simulated microelectronic chips with a nominal area of 5 mm × 5 mm. The heat transfer modes included natural convection, partially developed nucleate boiling, fully developed nucleate boiling and critical heat flux. The study included the effects of jet parameters and fluid subcooling on the nucleate boiling. The results showed that the nucleate boiling data varied only with fluid subcooling regardless of jet parameters and that both the pool and impingement nucleate boiling curves at the same subcooling condition were well correlated. The high heat flux portions of the boiling curves with jet exit velocities greater than 10 m/s were corrected for the elevated saturation temperature. A new expression was developed with an interpolation method to construct the partially developed nucleate boiling curve.

  9. Boiling incipience and convective boiling of neon and nitrogen

    NASA Technical Reports Server (NTRS)

    Papell, S. S.; Hendricks, R. C.

    1977-01-01

    Forced convection and subcooled boiling heat transfer data for liquid nitrogen and liquid neon were obtained in support of a design study for a 30 tesla cryomagnet cooled by forced convection of liquid neon. The cryogen data obtained over a range of system pressures, fluid flow rates, and applied heat fluxes were used to develop correlations for predicting boiling incipience and convective boiling heat transfer coefficients in uniformly heated flow channels. The accuracy of the correlating equations was then evaluated. A technique was also developed to calculate the position of boiling incipience in a uniformly heated flow channel. Comparisons made with the experimental data showed a prediction accuracy of + or - 15 percent.

  10. Subcooling for Long Duration In-Space Cryogenic Propellant Storage

    NASA Technical Reports Server (NTRS)

    Mustafi, Shuvo; Johnson, Wesley; Kashani, Ali; Jurns, John; Kutter, Bernard; Kirk, Daniel; Shull, Jeff

    2010-01-01

    Cryogenic propellants such as hydrogen and oxygen are crucial for exploration of the solar system because of their superior specific impulse capability. Future missions may require vehicles to remain in space for months, necessitating long-term storage of these cryogens. A Thermodynamic Cryogen Subcooler (TCS) can ease the challenge of cryogenic fluid storage by removing energy from the cryogenic propellant through isobaric subcooling of the cryogen below its normal boiling point prior to launch. The isobaric subcooling of the cryogenic propellant will be performed by using a cold pressurant to maintain the tank pressure while the cryogen's temperature is simultaneously reduced using the TCS. The TCS hardware will be integrated into the launch infrastructure and there will be no significant addition to the launched dry mass. Heat leaks into all cryogenic propellant tanks, despite the use of the best insulation systems. However, the large heat capacity available in the subcooled cryogenic propellants allows the energy that leaks into the tank to be absorbed until the cryogen reaches its operational thermodynamic condition. During this period of heating of the subcooled cryogen there will be minimal loss of the propellant due to venting for pressure control. This simple technique can extend the operational life of a spacecraft or an orbital cryogenic depot for months with minimal mass penalty. In fact isobaric subcooling can more than double the in-space hold time of liquid hydrogen compared to normal boiling point hydrogen. A TCS for cryogenic propellants would thus provide an enhanced level of mission flexibility. Advances in the important components of the TCS will be discussed in this paper.

  11. Geochemistry of hydrothermal fluids from Axial Seamount Hydrothermal Emissions Study vent field, Juan de Fuca Ridge: Subseafloor boiling and subsequent fluid-rock interaction

    SciTech Connect

    Butterfield, D.A.; McDuff, R.E.; Lilley, M.D. ); Massoth, G.J. ); Lupton, J.E. )

    1990-08-10

    Hydrothermal fluids collected from the ASHES vent field in 1986, 1987, and 1988 exhibit a very wide range of chemical composition over a small area ({approximately} 60 m in diameter). Compositions range from a 300C, gas-enriched (285 mmol/kg CO{sub 2}), low-chlorinity ({approximately} 33% of seawater) fluid to a 328C, relatively gas-depleted (50 mmol/kg CO{sub 2}), high-chlorinity ({approximately} 116% of seawater) fluid. The entire range of measured compositions at ASHES is best explained by a single hydrothermal fluid undergoing phase separation while rising through the ocean crust, followed by partial segregation of the vapor and brine phases. Other mechanisms proposed to produce chlorinity variations in hydrothermal fluids (precipitation/dissolution of a chloride-bearing mineral or crustal hydration) cannot produce the covariation of chlorinity and gas content observed at ASHES. There is good argument of the measured fluid compositions generated by a simple model of phase separation, in which gases are partitioned according to Henry's law and all salt remains in the liquid phase. Significant enrichments in silica, lithium and boron in the low-chlorinity fluids over levels predicted by the model are attributed to fluid-rock interaction in the upflow zone. Depletions in iron and calcium suggest that these elements have been removed by iron-sulfide and anhydrite precipitation at some time in the history of the low-chlorinity fluids. The distribution of low- and high-chlorinity venting is consistent with mechanisms of phase segregation based on differential buoyancy or relative permeability. The relatively shallow depth of the seafloor (1,540 m) and the observed chemistry of ASHES fluids are consistent with phase separation in the sub-critical or near-critical region.

  12. Condensation on a noncollapsing vapor bubble in a subcooled liquid

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Simoneau, R. J.

    1979-01-01

    An experimental procedure is presented by which an estimate can be made of the condensation coefficient on a noncollapsing stationary vapor bubble in subcooled liquid nitrogen. Film boiling from a thin wire was used to generate vapor bubbles which remain fixed to the wire at their base. A balance was established between the evaporation in the thin annular region along the wire and the condensation in the vapor bubbles.

  13. Condensation on a noncollapsing vapor bubble in a subcooled liquid

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Simoneau, R. J.

    1979-01-01

    An experimental procedure is presented by which an estimate can be made of the condensation coefficient on a noncollapsing stationary vapor bubble in subcooled liquid nitrogen. The present experimental study utilizes film boiling from a thin wire to generate vapor bubbles which remain fixed to the wire at their base. A balance was established between the evaporation in the thin annular region along the wire and the condensation in the vapor bubbles.

  14. Interfacial instability of a condensing vapor bubble in a subcooled liquid

    NASA Astrophysics Data System (ADS)

    Ueno, I.; Ando, J.; Koiwa, Y.; Saiki, T.; Kaneko, T.

    2015-03-01

    A special attention is paid to the condensing and collapsing processes of vapor bubble injected into a subcooled pool. We try to extract the vapor-liquid interaction by employing a vapor generator that supplies vapor to the subcooled pool through an orifice instead of using a immersed heating surface to realize vapor bubbles by boiling phenomenon. This system enables ones to detect a spatio-temporal behavior of a single bubble of superheated vapor exposed to a subcooled liquid. In the present study, vapor of water is injected through an orifice at constant flow rate to the subcooled pool of water at the designated degree of subcooling under the atmospheric pressure. The degree of subcooling of the pool is ranged from 0 K to 70 K, and the vapor temperature is kept constant at 101 ?C. The behaviors of the injected vapor are captured by high-speed camera at frame rate up to 0.3 million frame per second (fps) to track the temporal variation of the vapor bubble shape. It is found that the abrupt collapse of the vapor bubble exposed to the subcooled pool takes place under the condition that the degree of subcooling is greater than around 30 K, and that the abrupt collapse always takes place accompanying the fine disturbances or instability emerged on the free surface. We then evaluate a temporal variation of the apparent `volume' of the bubble V under the assumption of the axisymmetric shape of the vapor bubble. It is also found that the instability emerges slightly after the volume of the vapor bubble reaches the maximum value. It is evaluated that the second derivative of the corresponding `radius' R of the vapor bubble is negative when the instability appears on the bubble surface, where R = 3? 3V/4?. We also illustrate that the wave number of the instability on the liquid-vapor interface increases as the degree of subcooling.

  15. Self-sustained hydrodynamic oscillations in a natural-circulation two-phase-flow boiling loop

    NASA Technical Reports Server (NTRS)

    Jain, K. C.

    1969-01-01

    Results of an experimental and theoretical study of factors affecting self-sustaining hydrodynamic oscillations in boiling-water loops are reported. Data on flow variables, and the effects of geometry, subcooling and pressure on the development of oscillatory behavior in a natural-circulation two-phase-flow boiling loop are included.

  16. An analysis of a flat-plate solar collector with internal boiling

    SciTech Connect

    Abramzon, B.; Borde, I.; Yaron, I.

    1983-11-01

    The extended mathematical model of a flat-plate solar collector-evaporator permits prediction of the effects of boiling of the working fluid in the collector tubes on the efficiency of the collector. The efficiency increases sharply and approaches the ideal on transition from single phase flow to the subcooled and saturated boiling regimes, regardless of the nature of the working fluid.

  17. Flow boiling in vertical down-flow

    SciTech Connect

    Dougherty, T.; Fighetti, C.; Reddy, G.; Yang, B.; Jafri, T. ); McAssey, E. ); Qureshi, Z. )

    1989-01-01

    An experimental program has been conducted to investigate the onset of Ledinegg instability in vertical down-flow. For three size uniformly heated test sections with L/D ratios from 100 to 150, the pressure drop under subcooled boiling conditions has been obtained for a wide range of operating parameters. The results are presented in non-dimensional forms which correlate the important variables and provide techniques for predicting the onset of flow instability. 3 refs.

  18. Flow boiling in vertical down-flow

    SciTech Connect

    Dougherty, T.; Fighetti, C.; Reddy, G.; Yang, B.; Jafri, T.; McAssey, E.; Qureshi, Z.

    1989-12-31

    An experimental program has been conducted to investigate the onset of Ledinegg instability in vertical down-flow. For three size uniformly heated test sections with L/D ratios from 100 to 150, the pressure drop under subcooled boiling conditions has been obtained for a wide range of operating parameters. The results are presented in non-dimensional forms which correlate the important variables and provide techniques for predicting the onset of flow instability. 3 refs.

  19. Analysis of boiling flat-plate collectors

    SciTech Connect

    Price, H.W.; Klein, S.A.; Beckman, W.A.

    1986-05-01

    A detailed model for use with TRNSYS, capable of modelling a wide range of boiling collector types, was used to analyze boiling flat-plate collector systems. This model can account for a subcooled liquid entering the collector, heat losses in the vapor and the liquid return line, pressure drops due to friction in the collector and piping, and pressure drops due to the hydrostatic head of the fluid. The model has been used to determine the yearly performance of boiling flat-plate solar collector systems. A simplified approach was also developed which can be used with the f-Chart method to predict yearly performance of boiling flat-plate collector systems.

  20. Testing and evaluation of small cavitating venturis with water at low inlet subcooling

    NASA Astrophysics Data System (ADS)

    Liou, S. G.; Chen, I. Y.; Sheu, J. S.

    1998-01-01

    Cavitating venturi (CV) has been widely used as a flow control device in many different industries. In 1990, cavitating venturi was selected as the baseline flow control device in the Space Station Freedom's (SSF's) two-phase active thermal control system (ATCS). However, the design and the operation of the CVs used in SSF's ATCS is quite different in many ways from that typically used in the industry, such as low mass flow rate, small size, low pressure difference between inlet and outlet, and low inlet subcooling. During the prototypic ATCS' testing at NASA/Johnson Space Center, a phenomenon called overflow associated with throat superheat was observed. Although data was obtained and analyzed, no useful correlation for the superheat at rechoking was acquired. The objective of this study is to conduct a performance test on small CVs under low inlet subcooling. Water is used as the working fluid. Data acquisition and analysis are carried out under normal choked flow, over flow and recovery conditions. The effects of CV's size, fluid temperature, flow condition and inlet subcooling on CV performance are evaluated. Analysis of the test results showed that the superheat necessary for the onset of nucleation in pool boiling can be applied for the estimation of superheat required at rechoking for the CVs. With this postulated superheat and the predetermined CV loss coefficient, a equation as a function of inlet subcooling is recommended for predicting the pressure ratio at the recovery for the choked flow control in a mechanically pumped system.

  1. Evaluation of engine coolants under flow boiling conditions

    SciTech Connect

    McAssey, E.V. Jr.; Stinson, C.; Gollin, M.

    1995-12-31

    An experimental program has been conducted to evaluate the heat transfer performance of two engine coolant mixtures, propylene-glycol/water and ethylene-glycol/water. In each mixture, the concentration was 50-50 by volume. Performance in this situation is defined as the ability to maintain a lower surface temperature for a given flux. The heat transfer regimes considered covered the range from single phase forced convection through saturated flow boiling. Results show that both coolants perform satisfactorily. However, in single phase convection, ethylene-glycol/water is slightly more effective. Conversely, for sub-cooled nucleate boiling and saturated boiling, propylene-glycol/water results in slightly lower metal temperatures.

  2. Sliding bubbles on a hot horizontal wire in a subcooled bath

    NASA Astrophysics Data System (ADS)

    Duchesne, Alexis; Dubois, Charles; Caps, Hervé

    2015-11-01

    When a wire is heated up to the boiling point in a liquid bath some bubbles will nucleate on the wire surface. Traditional nucleate boiling theory predicts that bubbles generate from active nucleate site, grow up and depart from the heating surface due to buoyancy and inertia. However, an alternative scenario is presented in the literature for a subcooled bath: bubbles slide along the horizontal wire before departing. New experiments were performed by using a constantan wire and different liquids, varying the injected power. Silicone oil, water and even liquid nitrogen were tested in order to vary wetting conditions, liquid viscosities and surface tensions. We explored the influence of the wire diameter and of the subcooled bath temperature. We observed, of course, sliding motion, but also a wide range of behaviors from bubbles clustering to film boiling. We noticed that bubbles could change moving sense, especially when encountering with another bubble. The bubble speed is carefully measured and can reach more than 100 mm/s for a millimetric bubble. We investigated the dependence of the speed on the different parameters and found that this speed is, for a given configuration, quite independent of the injected power. We understand these phenomena in terms of Marangoni effects. This project has been financially supported by ARC SuperCool contract of the University of Liège.

  3. TAURUS II launch vehicle lox subcooler

    NASA Astrophysics Data System (ADS)

    McIntosh, Glen E.

    2012-06-01

    The Orbital Sciences Taurus II medium lift launch vehicle utilizes first stage engines fueled by liquid oxygen and RP-1. Performance of the Taurus II is enhanced by densifying the liquid oxygen from a saturation temperature of 94 K to a subcooled temperature of 77.9 K. Subcooling the 75.07 kg/s liquid oxygen flow is accomplished in a 1.907 megawatt heat exchanger cooled by a flow of 9.62 kg/s ambient pressure liquid nitrogen. Design, fabrication, insulation and testing of the densification heat exchanger is described in this paper.

  4. Visualization study on pool boiling heat transfer

    NASA Astrophysics Data System (ADS)

    Kamei, Shuya; Hirata, Masaru

    1991-04-01

    The visualized boiling phenomena were observed by means of high speed photographic shadowgraphy using a rotating prism camera (nac HIGH SPEED CAMERA model-16HD) with the speed of about 3500 frames per second. The photographs show that pool boiling heat transfer phenomena are varied for the boiling curve based on the experiments. Experiments have been carried out to investigate pool boiling heat transfer phenomena on a horizontal thin filament in subcooled and saturated distilled water. The experiments were performed for atmospheric pressure,for filament diameters of about 0.3 mm, for region of natural convection to film boiling. The color-film made by high speed movie camera are converted to high speed color video-tape. It is convenient to edit and show the tape for visualization with teaching the students. The high speed color video showed that the successive motion and shape of bubbles during their process of detachment varied with increasing heat flux on the heated surface of a filament. From these results, it was confirmed that the high speed phenomena of boiling by the slow motion video pictures could be estimated clearly.

  5. To boil or not to boil -- A study of bubble embryo dormancy limits

    SciTech Connect

    Martin-Dominguez, I.R.; McDonald, T.W.

    1997-12-31

    In the literature, particularly for refrigerants, experimental studies on the superheat required to initiate nucleate boiling tend to be widely scattered, not only among investigators but even for repeated tests by the same investigator. This study provides an explanation of why this occurs and how to avoid such scatter in future tests. With few exceptions, only re-entrant surface cavities are capable of containing dormant vapor bubble embryos. These dormant embryos are essential to initiate nucleate boiling from a cavity. The temperature (wall superheat) range over which an embryo is stable depends upon the cavity shape, neck size, and the fluid surface tension and thermal properties. Above the upper wall-superheat limit, nucleate boiling occurs. Below the lower limit, the embryo will quench (vanish) and cannot be reactivated by increasing the wall superheat. This study makes the following points, for a given cavity shape, fluid, and pressure (1) The larger the cavity neck radius, the smaller the wall-superheat range over which an embryo can exist. (2) Upon cooling any surface, the boiling cavity with the smallest neck radius will be the first to stop boiling but will require the greatest reduction in wall superheat to quench its embryo. (3) Each site that retains a (dormant) vapor embryo will resume boiling at the same wall-superheat at which it ceased boiling. (4) Small cavities can have a shape such that their vapor embryos will always exist, regardless of the wall temperature. Boiling can always be reinitiated from them. (5) Any wall subject to boiling has a memory. The greater the past wall-subcooling, the greater will be the wall-superheat required to initiate boiling. (6) The wall memory can be erased with sufficient wall-superheat and the presence of vapor.

  6. Pool boiling from rotating and stationary spheres in liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Cuan, Winston M.; Schwartz, Sidney H.

    1988-01-01

    Results are presented for a preliminary experiment involving saturated pool boiling at 1 atm from rotating 2 and 3 in. diameter spheres which were immersed in liquid nitrogen (LN2). Additional results are presented for a stationary, 2 inch diameter sphere, quenched in LN2, which were obtained utilizing a more versatile and complete experimental apparatus that will eventually be used for additional rotating sphere experiments. The speed for the rotational tests was varied from 0 to 10,000 rpm. The stationary experiments parametrically varied pressure and subcooling levels from 0 to 600 psig and from 0 to 50 F, respectively. During the rotational tests, a high speed photographic analysis was undertaken to measure the thickness of the vapor film surrounding the sphere. The average Nusselt number over the cooling period was plotted against the rotational Reynolds number. Stationary sphere results included local boiling heat transfer coefficients at different latitudinal locations, for various pressure and subcooling levels.

  7. A Study of Nucleate Boiling with Forced Convection in Microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1999-01-01

    The ultimate objective of basic studies of flow boiling in microgravity is to improve the understanding of the processes involved, as manifested by the ability to predict its behavior. This is not yet the case for boiling heat transfer even in earth gravity, despite the considerable research activity over the past 30 years. The elements that constitute the nucleate boiling process - nucleation, growth, motion, and collapse of the vapor bubbles (if the bulk liquid is subcooled) - are common to both pool and flow boiling. It is well known that the imposition of bulk liquid motion affects the vapor bubble behavior relative to pool boiling, but does not appear to significantly influence the heat transfer. Indeed, it has been recommended in the past that empirical correlations or experimental data of pool boiling be used for design purposes with forced convection nucleate boiling. It is anticipated that such will most certainly not be possible for boiling in microgravity, based on observations made with pool boiling in microgravity. In earth gravity buoyancy will act to remove the vapor bubbles from the vicinity of the heater surface regardless of how much the imposed bulk velocity is reduced, depending, of course, on the geometry of the system. Vapor bubbles have been observed to dramatically increase in size in pool boiling in microgravity, and the heat flux at which dryout took place was reduced considerably below what is generally termed the critical heat flux (CHF) in earth gravity, depending on the bulk liquid subcooling. However, at heat flux levels below dryout, the nucleate pool boiling process was enhanced considerably over that in earth gravity, in spite of the large vapor bubbles formed in microgravity and perhaps as a consequence. These large vapor bubbles tended to remain in the vicinity of the heater surface, and the enhanced heat transfer appeared to be associated with the presence of what variously has been referred to as a liquid microlayer between the bubble and the heater surface. The enhancement of the boiling process with low velocities in earth gravity for those orientations producing the formation of a liquid macrolayer described above, accompanied by "sliding" vapor bubbles, has been demonstrated. The enhancement was presented as a function of orientation, subcooling, and heated length, while a criterion for the heat transfer for mixed natural/forced convection nucleate boiling was given previously. A major unknown in the prediction and application of flow boiling heat transfer in microgravity is the upper limit of the heat flux for the onset of dryout (or critical heat flux - CHF), for given conditions of fluid-heater surfaces, including geometry, system pressure and bulk liquid subcooling. It is clearly understood that the behavior in microgravity will be no different than on earth with sufficiently high flow velocities, and would require no space experimentation. However, the boundary at which this takes place is still an unknown. Previous results of CHF measurements were presented for low velocity flow boiling at various orientations in earth gravity as a function of flow velocity and bulk liquid subcooling, along with preliminary measurements of bubble residence times on a flat heater surface. This showed promise as a parameter to be used in modeling the CHF, both in earth gravity and in microgravity. The objective of the work here is to draw attention to and show results of current modeling efforts for the CHF, with low velocities in earth gravity at different orientations and subcoolings. Many geometrical possibilities for a heater surface exist in flowing boiling, with boiling on the inner and outer surfaces of tubes perhaps being the most common. If the vapor bubble residence time on and departure size from the heater surface bear a relationship to the CHF, as results to be given indicate, it is important that visualization of and access to vapor bubble growth be conveniently available for research purposes. In addition, it is desirable to reduce the number of variables as much as possible in a fundamental study. These considerations dictated the use of a flat heater surface, which is rectangular in shape, 1.91 cm by 3.81 cm (0.75 x 1.5 inches), consisting either of a 400 Angstrom thick semi-transparent gold film sputtered on a quartz substrate which serves simultaneously as a heater and a resistance thermometer, or a copper substrate of the same size. The heater substrate is a disc which can be rotated so that the heated length in the flow direction can be changed from 1.91 to 3.81 cm (0.75 to 1.5 inches). The fluid is R-113, and the velocities can be varied between 0.5 cm/s and 60 cm/s. For a sufficiently low velocity the CHF can be modeled reasonably well at various orientations by the correlation for pool boiling corrected for the influence of bulk liquid subcooling, multiplied by the square root of q, the angle relative to horizontal. This arises from equating buoyancy and drag forces in the inverted positions where the vapor bubbles are held against the heater surface as they slide. A distortion of the measurements relative to pool boiling occurs as the flow velocity increases. In modeling this effect at different levels of subcooling it appeared appropriate to estimate the volumetric rate of vapor generation, using measurements of bubble frequency (or residence time), void fraction and average bubble boundary layer thickness. These were determined with the use of a platinum hot wire probe 0.025 mm in diameter by 1.3 mm long, applying a constant current to distinguish between contact with liquid or vapor. Two-dimensional spatial variations are obtained with a special mechanism to resolve displacements in increments of 0.025 mm. From such measurements it was determined that the fraction of the surface heat transfer resulting in evaporation varies inversely with the subcooling correction factor for the CHF. The measured inverse bubble residence time is normalized relative to that predicted for an infinite horizontal flat plate at the CHF, and is correlated well with the CHF normalized relative to that for pool boiling, for various orientation angles and subcooling levels. This correspondence is then combined with a normalizing factor for the energy flux leaving the heater surface at the CHF and the computed bubble radius at departure, determined from the balance between the outward velocity of the interface due to evaporation and the buoyance induced velocity of the center of mass of the bubble. The product of the CHF and the corresponding residence time was determined to be a constant for all orientations at a given bulk flow velocity and liquid subcooling, and must be determined empirically for each velocity and subcooling at present. It then becomes possible to predict the CHF for the different orientations, velocities, and subcoolings. These are compared with normalized measurements of the CHF for velocities ranging from 4 cm/s to 55 cm/s, subcoolings from 2.8 to 22.2 K, over orientations angles of 360 degrees.

  8. Boiling Experiment Facility for Heat Transfer Studies in Microgravity

    NASA Technical Reports Server (NTRS)

    Delombard, Richard; McQuillen, John; Chao, David

    2008-01-01

    Pool boiling in microgravity is an area of both scientific and practical interest. By conducting tests in microgravity, it is possible to assess the effect of buoyancy on the overall boiling process and assess the relative magnitude of effects with regards to other "forces" and phenomena such as Marangoni forces, liquid momentum forces, and microlayer evaporation. The Boiling eXperiment Facility is now being built for the Microgravity Science Glovebox that will use normal perfluorohexane as a test fluid to extend the range of test conditions to include longer test durations and less liquid subcooling. Two experiments, the Microheater Array Boiling Experiment and the Nucleate Pool Boiling eXperiment will use the Boiling eXperiment Facility. The objectives of these studies are to determine the differences in local boiling heat transfer mechanisms in microgravity and normal gravity from nucleate boiling, through critical heat flux and into the transition boiling regime and to examine the bubble nucleation, growth, departure and coalescence processes. Custom-designed heaters will be utilized to achieve these objectives.

  9. Modeling of subcooling and solidification of phase change materials

    NASA Astrophysics Data System (ADS)

    Günther, Eva; Mehling, Harald; Hiebler, Stefan

    2007-12-01

    Phase change materials (PCM) are able to store thermal energy in small temperature intervals very efficiently due to their high latent heat. Particularly high storage capacity is found in salt hydrates. Salt hydrates however often show subcooling, thus inhibiting the release of the stored heat. In the state of the art simulations of PCM, the effect of subcooling is almost always neglected. This is a practicable approach for small subcooling, but it is problematic for subcooling in the order of the driving temperature gradient on unloading the storage. In this paper, we first present a new algorithm to simulate subcooling in a physically proper way. Then, we present a parametric study to demonstrate the main features of the algorithm and a comparison of computed and experimentally obtained data. The new algorithm should be particularly useful in simulating applications with low cooling rates, for example building applications.

  10. Boiling Heat Transfer Mechanisms in Earth and Low Gravity: Boundary Condition and Heater Aspect Ratio Effects

    NASA Technical Reports Server (NTRS)

    Kim, Jungho

    2004-01-01

    Boiling is a complex phenomenon where hydrodynamics, heat transfer, mass transfer, and interfacial phenomena are tightly interwoven. An understanding of boiling and critical heat flux in microgravity environments is of importance to space based hardware and processes such as heat exchange, cryogenic fuel storage and transportation, electronic cooling, and material processing due to the large amounts of heat that can be removed with relatively little increase in temperature. Although research in this area has been performed in the past four decades, the mechanisms by which heat is removed from surfaces in microgravity are still unclear. Recently, time and space resolved heat transfer data were obtained in both earth and low gravity environments using an array of microheaters varying in size between 100 microns to 700 microns. These heaters were operated in both constant temperature as well as constant heat flux mode. Heat transfer under nucleating bubbles in earth gravity were directly measured using a microheater array with 100 m resolution operated in constant temperature mode with low and high subcooled bulk liquid along with images from below and from the side. The individual bubble departure diameter and energy transfer were larger with low subcooling but the departure frequency increased at high subcooling, resulting in higher overall heat transfer. The bubble growth for both subcoolings was primarily due to energy transfer from the superheated liquid layer relatively little was due to wall heat transfer during the bubble growth process. Oscillating bubbles and sliding bubbles were also observed in highly subcooled boiling. Transient conduction and/or microconvection was the dominant heat transfer mechanism in the above cases. A transient conduction model was developed and compared with the experimental data with good agreement. Data was also obtained with the heater array operated in a constant heat flux mode and measuring the temperature distribution across the array during boiling. The instantaneous heat transfer into the substrate was numerically determined and subtracted from the supplied heat to obtain the wall to liquid heat flux.

  11. Hydrothermal processes above the Yellowstone magma chamber: Large hydrothermal systems and large hydrothermal explosions

    USGS Publications Warehouse

    Morgan, L.A.; Shanks, W.C. Pat, III; Pierce, K.L.

    2009-01-01

    Hydrothermal explosions are violent and dramatic events resulting in the rapid ejection of boiling water, steam, mud, and rock fragments from source craters that range from a few meters up to more than 2 km in diameter; associated breccia can be emplaced as much as 3 to 4 km from the largest craters. Hydrothermal explosions occur where shallow interconnected reservoirs of steam- and liquid-saturated fluids with temperatures at or near the boiling curve underlie thermal fields. Sudden reduction in confi ning pressure causes fluids to fl ash to steam, resulting in signifi cant expansion, rock fragmentation, and debris ejection. In Yellowstone, hydrothermal explosions are a potentially signifi cant hazard for visitors and facilities and can damage or even destroy thermal features. The breccia deposits and associated craters formed from hydrothermal explosions are mapped as mostly Holocene (the Mary Bay deposit is older) units throughout Yellowstone National Park (YNP) and are spatially related to within the 0.64-Ma Yellowstone caldera and along the active Norris-Mammoth tectonic corridor. In Yellowstone, at least 20 large (>100 m in diameter) hydrothermal explosion craters have been identifi ed; the scale of the individual associated events dwarfs similar features in geothermal areas elsewhere in the world. Large hydrothermal explosions in Yellowstone have occurred over the past 16 ka averaging ??1 every 700 yr; similar events are likely in the future. Our studies of large hydrothermal explosion events indicate: (1) none are directly associated with eruptive volcanic or shallow intrusive events; (2) several historical explosions have been triggered by seismic events; (3) lithic clasts and comingled matrix material that form hydrothermal explosion deposits are extensively altered, indicating that explosions occur in areas subjected to intense hydrothermal processes; (4) many lithic clasts contained in explosion breccia deposits preserve evidence of repeated fracturing and vein-fi lling; and (5) areal dimensions of many large hydrothermal explosion craters in Yellowstone are similar to those of its active geyser basins and thermal areas. For Yellowstone, our knowledge of hydrothermal craters and ejecta is generally limited to after the Yellowstone Plateau emerged from beneath a late Pleistocene icecap that was roughly a kilometer thick. Large hydrothermal explosions may have occurred earlier as indicated by multiple episodes of cementation and brecciation commonly observed in hydrothermal ejecta clasts. Critical components for large, explosive hydrothermal systems include a watersaturated system at or near boiling temperatures and an interconnected system of well-developed joints and fractures along which hydrothermal fluids flow. Active deformation of the Yellowstone caldera, active faulting and moderate local seismicity, high heat flow, rapid changes in climate, and regional stresses are factors that have strong infl uences on the type of hydrothermal system developed. Ascending hydrothermal fluids flow along fractures that have developed in response to active caldera deformation and along edges of low-permeability rhyolitic lava flows. Alteration of the area affected, self-sealing leading to development of a caprock for the hydrothermal system, and dissolution of silica-rich rocks are additional factors that may constrain the distribution and development of hydrothermal fields. A partial lowpermeability layer that acts as a cap to the hydrothermal system may produce some over-pressurization, thought to be small in most systems. Any abrupt drop in pressure initiates steam fl ashing and is rapidly transmitted through interconnected fractures that result in a series of multiple large-scale explosions contributing to the excavation of a larger explosion crater. Similarities between the size and dimensions of large hydrothermal explosion craters and thermal fields in Yellowstone may indicate that catastrophic events which result in l

  12. Steady State Vapor Bubble in Pool Boiling.

    PubMed

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  13. Steady State Vapor Bubble in Pool Boiling

    NASA Astrophysics Data System (ADS)

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-02-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.

  14. Steady State Vapor Bubble in Pool Boiling

    PubMed Central

    Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.

    2016-01-01

    Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464

  15. Low velocity nucleate flow boiling at various orientations

    NASA Technical Reports Server (NTRS)

    Kirk, Kevin M.; Merte, Herman, Jr.; Keller, Robert B.

    1992-01-01

    Subcooled forced convection nucleate boiling experiments with R-113 were conducted at low velocities using both thin film semi-transparent gold on quartz and gold coated cooper substrate flat heaters at varying orientations. The results are intended to assist in understanding effects of buoyancy in forced convection boiling and in better defining requirements for studying flow boiling in the microgravity environment of space. Measurements of the heat flux and the surface superheat were made at three levels of subcooling from 2.2 C to 11.1 C, four bulk velocities from 4.1 cm/s to 32.4 cm/s and various orientations spanning 360 deg. The experiments demonstrate that if buoyancy is significant reative to bulk liquid momentum, then a decrease in the buoyant force normal and away from the heater surface enhances the heat transfer, with the effect being most prominent at low values of heat flux. Furthermore, the effect of velocity is shown to be dependent on the surface orientation.

  16. Hydrothermal Processing

    SciTech Connect

    Elliott, Douglas C.

    2011-03-11

    This chapter is a contribution to a book on Thermochemical Conversion of Biomass being edited by Prof. Robert Brown of Iowa State University. It describes both hydrothermal liquefaction and hydrothermal gasification of biomass to fuels.

  17. Net vapor generation point in boiling flow of trichlorotrifluoroethane at high pressures

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Lippert, T. E.

    1973-01-01

    The conditions at which the void in subcooled boiling starts to undergo a rapid increase were studied experimentally. The experiments were performed in a 12.7 x 9.5 mm rectangular channel. Heating was from a 3.2 mm wide strip embedded in one wall. The pressure ranged from 9.45 to 20.7 bar, mass velocity from 600 to 7000 kg/sq m sec, and subcooling from 16 to 67 C. Photographs were used to determine when detached bubbles first appeared in the bulk flow. Measurements of bubble layer thickness along the wall were also made. Results showed that the point of net vapor generation is close to the occurrence of fully-developed boiling.

  18. Nucleate Boiling Heat Transfer Studied Under Reduced-Gravity Conditions

    NASA Technical Reports Server (NTRS)

    Chao, David F.; Hasan, Mohammad M.

    2000-01-01

    Boiling is known to be a very efficient mode of heat transfer, and as such, it is employed in component cooling and in various energy-conversion systems. In space, boiling heat transfer may be used in thermal management, fluid handling and control, power systems, and on-orbit storage and supply systems for cryogenic propellants and life-support fluids. Recent interest in the exploration of Mars and other planets and in the concept of in situ resource utilization on the Martian and Lunar surfaces highlights the need to understand how gravity levels varying from the Earth's gravity to microgravity (1g = or > g/g(sub e) = or > 10(exp -6)g) affect boiling heat transfer. Because of the complex nature of the boiling process, no generalized prediction or procedure has been developed to describe the boiling heat transfer coefficient, particularly at reduced gravity levels. Recently, Professor Vijay K. Dhir of the University of California at Los Angeles proposed a novel building-block approach to investigate the boiling phenomena in low-gravity to microgravity environments. This approach experimentally investigates the complete process of bubble inception, growth, and departure for single bubbles formed at a well-defined and controllable nucleation site. Principal investigator Professor Vijay K. Dhir, with support from researchers from the NASA Glenn Research Center at Lewis Field, is performing a series of pool boiling experiments in the low-gravity environments of the KC 135 microgravity aircraft s parabolic flight to investigate the inception, growth, departure, and merger of bubbles from single- and multiple-nucleation sites as a function of the wall superheat and the liquid subcooling. Silicon wafers with single and multiple cavities of known characteristics are being used as test surfaces. Water and PF5060 (an inert liquid) were chosen as test liquids so that the role of surface wettability and the magnitude of the effect of interfacial tension on boiling in reduced gravity can be investigated.

  19. Secondary pool boiling effects

    NASA Astrophysics Data System (ADS)

    Kruse, C.; Tsubaki, A.; Zuhlke, C.; Anderson, T.; Alexander, D.; Gogos, G.; Ndao, S.

    2016-02-01

    A pool boiling phenomenon referred to as secondary boiling effects is discussed. Based on the experimental trends, a mechanism is proposed that identifies the parameters that lead to this phenomenon. Secondary boiling effects refer to a distinct decrease in the wall superheat temperature near the critical heat flux due to a significant increase in the heat transfer coefficient. Recent pool boiling heat transfer experiments using femtosecond laser processed Inconel, stainless steel, and copper multiscale surfaces consistently displayed secondary boiling effects, which were found to be a result of both temperature drop along the microstructures and nucleation characteristic length scales. The temperature drop is a function of microstructure height and thermal conductivity. An increased microstructure height and a decreased thermal conductivity result in a significant temperature drop along the microstructures. This temperature drop becomes more pronounced at higher heat fluxes and along with the right nucleation characteristic length scales results in a change of the boiling dynamics. Nucleation spreads from the bottom of the microstructure valleys to the top of the microstructures, resulting in a decreased surface superheat with an increasing heat flux. This decrease in the wall superheat at higher heat fluxes is reflected by a "hook back" of the traditional boiling curve and is thus referred to as secondary boiling effects. In addition, a boiling hysteresis during increasing and decreasing heat flux develops due to the secondary boiling effects. This hysteresis further validates the existence of secondary boiling effects.

  20. Liquid Nitrogen Subcooler ofr Calorimeters LN2 Supply

    SciTech Connect

    Sarychev, Michael; /Fermilab

    2002-09-16

    This note provides calculations of heat load and coil sizing for a LN2 subcooler which will be installed in the liquid nitrogen line going from Dewar 42 to the. Liquid argon calorimeters. This subcooler must improve LN2 quality and facilitate LAr pressure regulation. The system is described in Engineering note 3740.510-EN-382. This note contains the calculations of heat loads/pressure drops of the liquid Nitrogen supply line going from the Dewar 42 to the liquid Argon calorimeters, and also the sizing of existing LN2 subcooler located in the V-tube. The note is used as a reference. The state of Nitrogen {at} point 6 - ECS entrance (according to 3740.510-EN-382) is used in the calculations. The quality of liquid x = 0.0066 with the use of existing 75 W LN2 subcooler. It has been determined that we need 29.3 W of additional subcooling in order to obtain. 100% liquid at this point with the mass flow of 25 g/s. Keeping in mind the possible error in heat transfer calculations, a 300W subcooler will be installed to replace the old 75 W subcooler. In order to achieve an acceptable conclusion, an assumption of a fully developed boundary layer was made. The hot fluid or the fluid condensing on the inside surface will determine the rate of heat transfer because A{sub o} = A{sub i} and h{sub o}A{sub o} >> h{sub i}A{sub i}. The conclusion drawn is to use a 1/2-inch copper tube wound approximately 8 times about a 9-inch diameter circle. The pressure drop in this coil will be 0.05 psi (0.0034 atm) and can be neglected.

  1. Flow boiling with enhancement devices for cold plate coolant channel design

    NASA Technical Reports Server (NTRS)

    Boyd, Ronald D., Sr.; Smith, Alvin

    1990-01-01

    The use of flow boiling for thermal energy transport is intended to provide an alternative for accommodating higher heat fluxes in commercial space systems. The objectives are to: (1) examine the variations in both the mean and local (axial and circumferential) heat transfer coefficients for a circular coolant channel with either smooth walls, spiral fins, or both spiral fins and a twisted tape; (2) examine the effects of channel diameter and subcooling; and (3) develop an improved reduction analysis and/or suggest possible heat transfer correlation of the present data. Freon-11 is the working fluid. Two-dimensional (circumferential and axial) wall temperature distributions were measured for coolant channels with the above noted internal geometries. The flow regimes which are being studied are: (1) single phase; (2) subcooled flow boiling; and (3) stratified flow boiling. The inside diameter of all test sections is near 1.0 cm. Cicumferentially averaged heat transfer coefficients at several axial locations were obtained for selected coolant channels for a mass velocity of 210 kg/sq m s, an exit pressure of 0.19 MPa (absolute), and an inlet subcooling of 20.8 C. Overall (averaged over the entire channel) heat transfer coefficients were compared for the above channel geometries. This comparison showed that the channel with large pitch spiral fins had higher heat transfer coefficients at all power levels.

  2. Stability of forced-convection subcooled boiling in steady-state and transient annular flow

    SciTech Connect

    Gehrke, V.; Bankoff, S.G.

    1993-06-01

    A semi-analytical model developed by Lee and Bankoff for OFI in round tubes is extended to annular or parallel-plate flows with unequal heat fluxes, and shown to compare well with data by Dougherty, et al. and by Whittle and Forgan. The model is a better fit in the high Peclet number range than the Saha-Zuber model, and is simple to use.

  3. Simulation of Bubble Dynamics in Sub-Cooled Boiling on Fuel Clad in PWRs

    SciTech Connect

    Wu, Wen; Jones, Barclay G.

    2002-07-01

    The crud deposition on nuclear fuel assembly cladding generally increases the resistance to heat transfer, which may result in deterioration of thermal performance, degradation of the fuel cladding, and an axial power shift, i.e. Axial Offset Anomaly (AOA). Crud formation continues to elude prediction. An operational difficulty, of not being able to accurately determine power safety margin, then arises. In some cases, this condition has required decreasing the core power by as much as thirty percent, hence, resulting in considerable loss of revenue for the utility. The specific purpose of this study is to examine bubble dynamics, flow characteristics of the surrounding fluid, and its impact on the formation of the curd. The presence of a bubble on the clad surface affects the flow field around it, particularly in forming a stagnant flow region behind the bubble. The temperature difference between the bubble and the bulk coolant surrounding it causes vaporization at the bubble-clad interface and condensation at its apex. Pure water is thereby moved into the bubble through vaporization resulting in the concentration of solutes in the water at the bubble/wall surface region, which may cause their precipitation on and/or attachment to the clad surface, thereby initiating crud deposition. We investigate analytically and numerically, the growth of a bubble in the boundary layer and the influence of the bubble on the flow. Because of the small bubble size, a spherical model of the bubble is selected for our research. A two-step calculation is applied to this model. In the first step, bubble growth is estimated analytically with omission of the effect of the bulk fluid velocity, a reasonable approximation. In the second step, the flow field around the stationary bubble is obtained through numerical methods. Some parameters in PWR operating condition have been determined approximately e.g. size of the bubble, boundary layer thickness, flow velocity and drag forces on the bubble. (authors)

  4. New methods of subcooled water recognition in dew point hygrometers

    NASA Astrophysics Data System (ADS)

    Weremczuk, Jerzy; Jachowicz, Ryszard

    2001-08-01

    Two new methods of sub-cooled water recognition in dew point hygrometers are presented in this paper. The first one- impedance method use a new semiconductor mirror in which the dew point detector, the thermometer and the heaters were integrated all together. The second one an optical method based on a multi-section optical detector is discussed in the report. Experimental results of both methods are shown. New types of dew pont hydrometers of ability to recognized sub-cooled water were proposed.

  5. A study of forced convection boiling under reduced gravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1992-01-01

    This report presents the results of activities conducted over the period 1/2/85-12/31/90, in which the study of forced convection boiling under reduced gravity was initiated. The study seeks to improve the understanding of the basic processes that constitute forced convection boiling by removing the buoyancy effects which may mask other phenomena. Specific objectives may also be expressed in terms of the following questions: (1) what effects, if any, will the removal of body forces to the lowest possible levels have on the forced convection boiling heat transfer processes in well-defined and meaningful circumstances? (this includes those effects and processes associated with the nucleation or onset of boiling during the transient increase in heater surface temperature, as well as the heat transfer and vapor bubble behaviors with established or steady-state conditions); and (2) if such effects are present, what are the boundaries of the relevant parameters such as heat flux, heater surface superheat, fluid velocity, bulk subcooling, and geometric/orientation relationships within which such effects will be produced?

  6. Development of Flow Boiling and Condensation Experiment on the International Space Station- Normal and Low Gravity Flow Boiling Experiment Development and Test Results

    NASA Technical Reports Server (NTRS)

    Nahra, Henry K.; Hall, Nancy R.; Hasan, Mohammad M.; Wagner, James D.; May, Rochelle L.; Mackey, Jeffrey R.; Kolacz, John S.; Butcher, Robert L.; Frankenfield, Bruce J.; Mudawar, Issam; Konichi, Chris; Hyounsoon, Lee

    2013-01-01

    Flow boiling and condensation have been identified as two key mechanisms for heat transport that are vital for achieving weight and volume reduction as well as performance enhancement in future space systems. Since inertia driven flows are demanding on power usage, lower flows are desirable. However, in microgravity, lower flows are dominated by forces other than inertia (like the capillary force). It is of paramount interest to investigate limits of low flows beyond which the flow is inertial enough to be gravity independent. One of the objectives of the Flow Boiling and Condensation Flight Experiment sets to investigate these limits for flow boiling and condensation. A two-phase flow loop consisting of a Flow Boiling Module and two Condensation Modules has been developed to experimentally study flow boiling condensation heat transfer in the reduced gravity environment provided by the reduced gravity platform. This effort supports the development of a flow boiling and condensation facility for the International Space Station (ISS). The closed loop test facility is designed to deliver the test fluid, FC-72 to the inlet of any one of the test modules at specified thermodynamic and flow conditions. The zero-g-aircraft tests will provide subcooled and saturated flow boiling critical heat flux and flow condensation heat transfer data over wide range of flow velocities. Additionally, these tests will verify the performance of all gravity sensitive components, such as evaporator, condenser and accumulator associated with the two-phase flow loop. We will present in this paper the breadboard development and testing results which consist of detailed performance evaluation of the heater and condenser combination in reduced and normal gravity. We will also present the design of the reduced gravity aircraft rack and the results of the ground flow boiling heat transfer testing performed with the Flow Boiling Module that is designed to investigate flow boiling heat transfer and Critical Heat Flux (CHF) phenomena.

  7. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  8. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The

  9. Boiling heat transfer enhancement of nanofluids on a smooth surface with agitation

    NASA Astrophysics Data System (ADS)

    Kong, Xin; Qi, Baojin; Wei, Jinjia; Li, Wei; Ding, Jie; Zhang, Yonghai

    2016-02-01

    The pool boiling heat transfer performance on a smooth silicon chip surface with agitation was experimentally investigated in this study. The nanofluids (Ag/alcohol) of 0.02 % volume concentration and ethyl alcohol with purification over 99.9 % were the two contrast working fluids. For each group, subcoolings of 40, 50 and 60 K were conducted under atmospheric pressure. To enhance the heat transfer performance, an agitating device was fixed above the top of the chip. The experimental results indicated that nanofluids could enhance the heat transfer performance especially in the nucleate boiling region. The heat transfer coefficient was significantly increased with nanofluids, while the critical heat flux (CHF) was nearly not changed. In the agitation Reynolds number of 20,300, the heat transfer performance of nanofluids was significantly enhanced in the convection region, and the CHF was increased by more than 25 % for all groups. This boiling phenomenon was observed for both nanofluids and alcohol groups. Meanwhile, the boiling curves of different liquid subcoolings in the nucleate region were quite similar to each other under agitation.

  10. Boiling Heat Transfer in High Temperature Generator of Absorption Chiller/Heater

    NASA Astrophysics Data System (ADS)

    Furukawa, Masahiro; Enomoto, Eiichi; Sekoguchi, Kotohiko

    Heat transfer performance of forced convective boiling in high temperature generator was experimentally studied using an actual absorption chiller/heater. Measurements were made at six locations, three different levels on a couple of laterally separated lines, for the fluid rising along the rear wall of the high temperature generator furnace. Fluids tested were water and lithium bromide aqueous solution. System pressures were maintained at 96 and 24 kPa, and firing rates were changed from 100 to 40 % of the full load of the machine. Through the experiments, thermodynamic states of both of the fluids were in subcooled region at the lower and middle locations and in saturated region at the upper location. It can be suggested that saturated boiling occurs at comparatively narrow area, located at the upper zone of heat transfer surface of the generator, while forced convective heat transfer and subcooled boiling appear at the remaining broad area. Enhancement of heat transfer due to saturated boiling was not pronounced for lithium bromide aqueous solution than for water.

  11. Marangoni Effects in the Boiling of Binary Fluid Mixtures

    NASA Technical Reports Server (NTRS)

    Ahmed, Sayeed; Carey, Van P.; Motil, Brian

    1996-01-01

    Results of very recent experimental studies indicate that during nucleate boiling in some binary mixture, Marangoni effects augment the gravity driven flow of liquid towards the heated surface. With gravity present, it is impossible to separate the two effects. The reduced gravity environment gives an unique opportunity to explore th role of Marangoni effects on the boiling mechanisms free of gravitational body forces that obscure the role of such effects. However, recent experimental results suggest that under reduced gravity conditions, Marangoni effects is the dominant mechanism of vapor-liquid exchange at the surface for some binary mixture. To further explore such effects, experiments have been conducted with water/2-propanol mixtures at three different concentrations under normal gravity with different orientations of the heater surface and under reduce gravity aboard the DC-9 aircraft at NASA Lewis Research Center. The system pressure was sub atmospheric (approx. 8 kP at 1g(n)) and the bulk liquid temperature varied from low subcooling to near saturation. The molar concentrations of 2-propanol tested were 0.015, 0.025, and 0.1. Boiling curves were obtained both for high gravity (approx. 2g(n)) and reduce gravity (approx. 0.01g(n)). For each concentration of 2-propanol, the critical heat flux has been determined in the flight experiments only for reduced gravity conditions. Comparison of boiling curves and CHF obtained under l-g(n) an reduced gravity indicates that boiling mechanism in this mixtures is nearly independent of gravity. The results also indicate that the Marangoni mechanism is strong enough in these mixtures to sustain the boiling under reduced gravity conditions.

  12. Consideration of sub-cooled LN2 circulation system for HTS power machines

    NASA Astrophysics Data System (ADS)

    Yoshida, Shigeru; Hirai, Hirokazu; Nara, N.; Nagasaka, T.; Hirokawa, M.; Okamoto, H.; Hayashi, H.; Shiohara, Y.

    2012-06-01

    We consider a sub-cooled liquid nitrogen (LN) circulation system for HTS power equipment. The planned circulation system consists of a sub-cool heat exchanger (subcooler) and a circulation pump. The sub-cooler will be connected to a neon turbo- Brayton cycle refrigerator with a cooling power of 2 kW at 65 K. Sub-cooled LN will be delivered into the sub-cooler by the pump and cooled within it. Sub-cooled LN is adequate fluid for cooling HTS power equipment, because its dielectric strength is high and it supports a large critical current. However, a possibility of LN solidification in the sub-cooler is a considerable issue. The refrigerator will produce cold neon gas of about 60 K, which is lower than the nitrogen freezing temperature of 63 K. Therefore, we designed two-stage heat exchangers which are based on a plate-fin type and a tube-intube type. Process simulations of those heat exchangers indicate that sub-cooled LN is not frozen in either sub-cooler. The plate-fin type sub-cooler is consequently adopted for its reliability and compactness. Furthermore, we found that a cooling system with a Brayton refrigerator has the same total cooling efficiency as a cooling system with a Stirling refrigerator.

  13. Boiling from small cylinders.

    NASA Technical Reports Server (NTRS)

    Bakhru, N.; Lienhard, J. H.

    1972-01-01

    Heat transfer is observed as a function of temperature on small horizontal wires in water and four organic liquids. When the wire radius is sufficiently small, the hydrodynamic transitions in the boiling curve disappear and the curve becomes monotonic. Three modes of heat removal are identified for the monotonic curve and described analytically: a natural convection mode, a mixed film boiling and natural convection mode, and a pure film boiling mode. Nucleate boiling does not occur on the small wires. The study was motivated by an interest in predicting the behavior of large heaters at low gravity. The application of the present results to such circumstances is therefore discussed. It is proposed that the peak and minimum heat fluxes will vanish at low gravity as well as on small wires.

  14. Odd-Boiled Eggs

    ERIC Educational Resources Information Center

    Kaminsky, Kenneth; Scheman, Naomi

    2010-01-01

    At a Shabbat lunch in Madrid not long ago, the conversation turned to the question of boiling eggs. One of the guests mentioned that a Dutch rabbi he knew had heard that in order to make it more likely that boiled eggs be kosher, you should add an egg to the pot if the number you began with was even. According to the laws of Kashruth, Jews may not…

  15. Thermal Diffusion of Heat Pulse in Subcooled Liquid Nitrogen

    NASA Astrophysics Data System (ADS)

    Chang, H. M.; Byun, J. J.; Choi, J. H.; Ha, C. J.; Kim, M. J.; Kim, H. M.; Ko, T. K.

    2006-04-01

    Transient heat transfer caused by a heat pulse in subcooled liquid nitrogen is investigated experimentally. This study is part of our ongoing efforts to develop a stable cryogenic cooling system for superconducting fault current limiters (SFCL) in Korea. A thin heater attached by epoxy on one surface of a GFRP plate is immersed in a liquid-nitrogen bath at temperatures between 77 K and 65 K. A strong heat flux up to 150 W/cm2 is generated for 100 ms, and the temperature of the heater surface is measured as a function of time. The behavior of bubbles on the heating surface can be indirectly explained by comparing the measured temperature history for vertical and two different horizontal (up and down) orientations. It is concluded that subcooling liquid nitrogen below 70 K is a very effective method to suppress bubbles and result in better thermal protection and faster recovery from a heat pulse.

  16. SATURATED-SUBCOOLED STRATIFIED FLOW IN HORIZONTAL PIPES

    SciTech Connect

    Richard Schultz

    2010-08-01

    Advanced light water reactor systems are designed to use passive emergency core cooling systems with horizontal pipes that provide highly subcooled water from water storage tanks or passive heat exchangers to the reactor vessel core under accident conditions. Because passive systems are driven by density gradients, the horizontal pipes often do not flow full and thus have a free surface that is exposed to saturated steam and stratified flow is present.

  17. Critical flashing flows in nozzles with subcooled inlet conditions

    SciTech Connect

    Abuaf, N.; Jones, O.C. Jr.; Wu, B.J.C.

    1983-05-01

    Examination of a large number of experiments dealing with flashing flows in converging and converging-diverging nozzles reveals that knowledge of the flashing inception point is the key to the prediction of critical flow rates. An extension of the static flashing inception correlation of Jones (16) and Alamgir and Lienhard (17) to flowing systems has allowed the determination of the location of flashing inception in nozzle flows with subcooled inlet conditions. It is shown that in all the experiments examined with subcooled inlet regardless of the degree of inlet subcooling, flashing inception invariably occurred very close to the throat. A correlation is given to predict flashing inception in both pipes and nozzles which matches all data available, but is lacking verification in intermediate nozzle geometries where turbulence may be important. A consequence of this behavior is that the critical mass flux may be correlated to the pressure difference between the nozzle inlet and flashing inception, through a single phase liquid discharge coefficient and an accurate prediction of the flashing inception pressure at the throat. Comparison with the available experiments indicate that the predicted mass fluxes are within 5 percent of the measurements.

  18. Enhancement of Nucleate Boiling Heat Flux on Macro/Micro-Structured Surfaces Cooled by Multiple Impinging Jets

    NASA Technical Reports Server (NTRS)

    Kugler, Scott Lee

    1997-01-01

    An experimental investigation of nucleate boiling heat transfer from modified surfaces cooled by multiple in-line impinging circular jets is reported and found to agree with single jet results. A copper block is heated from the back by two electrical arcs, and cooled on the opposite side by three identical liquid jets of distilled water at subcoolings of 25 C 50 C and 77 C and Freon 113 at 24 C subcooling. Liquid flow rates are held constant at 5, 10, and 15 GPH for each of the three jets with jet velocities ranging from 1.4 m/s to 1 1.2 m/s and jet diameters from 0.95 mm to 2.2 mm. To increase the maximum heat flux (CHF) and heat removal rate, the boiling surface was modified by both macro and micro enhancements. Macro modification consists of machined radial grooves in the boiling surface arranged in an optimally designed pattern to allow better liquid distribution along the surface. These grooves also reduce splashing of liquid droplets, and provide 'channels' to sweep away bubbles. Micro modification was achieved by flame spraying metal powder on the boiling surface, creating a porous, sintered surface. With the addition of both micro and macro structured enhancements, maximum heat flux and nucleate boiling can be enhanced by more than 200%. Examination of each surface modification separately and together indicates that at lower superheats, the micro structure provides the enhanced heat transfer by providing more nucleation sites, while for higher superheats the macro structure allows better liquid distribution and bubble removal. A correlation is presented to account for liquid subcoolings and surface enhancements, in addition to the geometrical and fluid properties previously reported in the literature.

  19. Model for boiling and dryout in particle beds. [LMFBR

    SciTech Connect

    Lipinski, R. J.

    1982-06-01

    Over the last ten years experiments and modeling of dryout in particle beds have produced over fifty papers. Considering only volume-heated beds, over 250 dryout measurements have been made, and are listed in this work. In addition, fifteen models to predict dryout have been produced and are discussed. A model is developed in this report for one-dimensional boiling and dryout in a porous medium. It is based on conservation laws for mass, momentum, and energy. The initial coupled differential equations are reduced to a single first-order differential equation with an algebraic equation for the upper boundary condition. The model includes the effects of both laminar and turbulent flow, two-phase friction, and capillary force. The boundary condition at the bed bottom includes the possibility of inflowing liquid and either an adiabatic or a bottom-cooled support structure. The top of the bed may be either channeled or subcooled. In the first case the channel length and the saturation at the base of the channels are predicted. In the latter case, a criterion for penetration of the subcooled zone by channels is obtained.

  20. Transient heat transfer from a wire to a forced flow of subcooled liquid hydrogen passing through a vertically- mounted pipe

    NASA Astrophysics Data System (ADS)

    Tatsumoto, H.; Shirai, Y.; Shiotsu, M.; Naruo, Y.; Kobayashi, H.; Nonaka, S.; Inatani, Y.

    2015-12-01

    Transient heat transfers from Pt-Co wire heaters inserted into vertically-mounted pipes, through which forced flow subcooled liquid hydrogen was passed, were measured by increasing the exponential heat input with various time periods at a pressure of 0.7 MPa and inlet temperature of 21 K. The flow velocities ranged from 0.3 to 7 m/s. The Pt-Co wire heaters had a diameter of 1.2 mm and lengths of 60 mm, 120 mm and 200 mm and were inserted into the pipes with diameters of 5.7mm, 8.0 mm, and 5.0 mm, respectively, which were made of Fiber reinforced plastic due to thermal insulation. With increase in the heat flux to the onset of nucleate boiling, surface temperature increased along the curve predicted by the Dittus-Boelter correlation for longer period, where it can be almost regarded as steady-state. For shorter period, the heat transfer became higher than the Dittus-Boelter correlation. In nucleate boiling regime, the heat flux steeply increased to the transient CHF (critical heat flux) heat flux, which became higher for shorter period. Effect of flow velocity, period, and heated geometry on the transient CHF heat flux was clarified.

  1. Nucleate pool boiling in the long duration low gravity environment of the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Hasan, M. M.; Lin, C. S.; Knoll, R. H.; Bentz, M. D.; Meserole, J. S.

    1993-01-01

    The results are presented of an experimental study of nucleate pool boiling performed in the low gravity environment of the space shuttle. Photographic observations of pool boiling in Freon 113 were obtained during the 'Tank Pressure Control Experiment,' flown on the Space Transportation System, STS-43 in August 1991. Nucleate boiling data from large (relative to bubble size) flat heating surfaces (0.1046 by 0.0742 m) was obtained at very low heat fluxes (0.22 to 1.19 kW/sq m). The system pressure and the bulk liquid subcooling varied in the range of 40 to 60 kPa and 3 to 5 C respectively. Thirty-eight boiling tests, each of 10-min duration for a given heat flux, were conducted. Measurements included the heater power, heater surface temperature, the liquid temperature and the system pressure as functions of heating time. Video data of the first 2 min of heating was recorded for each test. In some tests the video clearly shows the inception of boiling and the growth and departure of bubbles from the surface during the first 2 min of heating. In the absence of video data, the heater temperature variation during heating shows the inception of boiling and stable nucleate boiling. During the stable nucleate boiling, the wall superheat varied between 2.8 to 3.8 C for heat fluxes in the range of 0.95 to 1.19 kW/sq m. The wall superheat at the inception of boiling varied between 2 to 13 C.

  2. Boiling inception in trichlorotrifluoroethane during forced convection at high pressures

    NASA Technical Reports Server (NTRS)

    Dougall, R. S.; Lippert, T. E.

    1972-01-01

    The inception of bubbles during forced convection was studied experimentally by using trichlorotrifluoroethane (R-113 or Freon-113). The experiments were performed in a rectangular channel, 12.7 x 9.5 mm in cross section. Heating was from a 3.2 mm wide strip embedded in the longer side of the channel. The pressures studied ranged from 3.6 to 20.7 bar, mass velocities from 700 to 600 kg/sq m/sec, and inlet subcoolings from 26 to 97 C. Photographs of the flow were used to determine when bubbles first appeared on the heated surface. These data were compared with wall temperature measurements and inception theories. A reasonable method for calculating the complete boiling curve was found to agree with these results.

  3. Radiolysis of boiling water

    NASA Astrophysics Data System (ADS)

    Yang, Shuang; Katsumura, Yosuke; Yamashita, Shinichi; Matsuura, Chihiro; Hiroishi, Daisuke; Lertnaisat, Phantira; Taguchi, Mitsumasa

    2016-06-01

    γ-radiolysis of boiling water has been investigated. The G-value of H2 evolution was found to be very sensitive to the purity of water. In high-purity water, both H2 and O2 gases were formed in the stoichiometric ratio of 2:1; a negligible amount of H2O2 remained in the liquid phase. The G-values of H2 and O2 gas evolution depend on the dose rate: lower dose rates produce larger yields. To clarify the importance of the interface between liquid and gas phase for gas evolution, the gas evolution under Ar gas bubbling was measured. A large amount of H2 was detected, similar to the radiolysis of boiling water. The evolution of gas was enhanced in a 0.5 M NaCl aqueous solution. Deterministic chemical kinetics simulation elucidated the mechanism of radiolysis in boiling water.

  4. Hydrothermal Processes

    NASA Astrophysics Data System (ADS)

    German, C. R.; von Damm, K. L.

    2003-12-01

    What is Hydrothermal Circulation?Hydrothermal circulation occurs when seawater percolates downward through fractured ocean crust along the volcanic mid-ocean ridge (MOR) system. The seawater is first heated and then undergoes chemical modification through reaction with the host rock as it continues downward, reaching maximum temperatures that can exceed 400 °C. At these temperatures the fluids become extremely buoyant and rise rapidly back to the seafloor where they are expelled into the overlying water column. Seafloor hydrothermal circulation plays a significant role in the cycling of energy and mass between the solid earth and the oceans; the first identification of submarine hydrothermal venting and their accompanying chemosynthetically based communities in the late 1970s remains one of the most exciting discoveries in modern science. The existence of some form of hydrothermal circulation had been predicted almost as soon as the significance of ridges themselves was first recognized, with the emergence of plate tectonic theory. Magma wells up from the Earth's interior along "spreading centers" or "MORs" to produce fresh ocean crust at a rate of ˜20 km3 yr-1, forming new seafloor at a rate of ˜3.3 km2 yr-1 (Parsons, 1981; White et al., 1992). The young oceanic lithosphere formed in this way cools as it moves away from the ridge crest. Although much of this cooling occurs by upward conduction of heat through the lithosphere, early heat-flow studies quickly established that a significant proportion of the total heat flux must also occur via some additional convective process (Figure 1), i.e., through circulation of cold seawater within the upper ocean crust (Anderson and Silbeck, 1981). (2K)Figure 1. Oceanic heat flow versus age of ocean crust. Data from the Pacific, Atlantic, and Indian oceans, averaged over 2 Ma intervals (circles) depart from the theoretical cooling curve (solid line) indicating convective cooling of young ocean crust by circulating seawater (after C. A. Stein and S. Stein, 1994). The first geochemical evidence for the existence of hydrothermal vents on the ocean floor came in the mid-1960s when investigations in the Red Sea revealed deep basins filled with hot, salty water (40-60 °C) and underlain by thick layers of metal-rich sediment (Degens and Ross, 1969). Because the Red Sea represents a young, rifting, ocean basin it was speculated that the phenomena observed there might also prevail along other young MOR spreading centers. An analysis of core-top sediments from throughout the world's oceans ( Figure 2) revealed that such metalliferous sediments did, indeed, appear to be concentrated along the newly recognized global ridge crest (Boström et al., 1969). Another early indication of hydrothermal activity came from the detection of plumes of excess 3He in the Pacific Ocean Basin (Clarke et al., 1969) - notably the >2,000 km wide section in the South Pacific ( Lupton and Craig, 1981) - because 3He present in the deep ocean could only be sourced through some form of active degassing of the Earth's interior, at the seafloor. (62K)Figure 2. Global map of the (Al+Fe+Mn):Al ratio for surficial marine sediments. Highest ratios mimic the trend of the global MOR axis (after Boström et al., 1969). One area where early heat-flow studies suggested hydrothermal activity was likely to occur was along the Galapagos Spreading Center in the eastern equatorial Pacific Ocean (Anderson and Hobart, 1976). In 1977, scientists diving at this location found hydrothermal fluids discharging chemically altered seawater from young volcanic seafloor at elevated temperatures up to 17 °C ( Edmond et al., 1979). Two years later, the first high-temperature (380±30 °C) vent fluids were found at 21° N on the East Pacific Rise (EPR) (Spiess et al., 1980) - with fluid compositions remarkably close to those predicted from the lower-temperature Galapagos findings ( Edmond et al., 1979). Since that time, hydrothermal activity has been found at more than 40 locations throughout the Pacific, North Atlantic, and Indian Oceans (e.g., Van Dover et al., 2002) with further evidence - from characteristic chemical anomalies in the ocean water column - of its occurrence in even the most remote and slowly spreading ocean basins ( Figure 3), from the polar seas of the Southern Ocean (German et al., 2000; Klinkhammer et al., 2001) to the extremes of the ice-covered Arctic ( Edmonds et al., 2003). (61K)Figure 3. Schematic map of the global ridge crest showing the major ridge sections along which active hydrothermal vents have already been found (red circles) or are known to exist from the detection of characteristic chemical signals in the overlying water column (orange circles). Full details of all known hydrothermally active sites and plume signals are maintained at the InterRidge web-site: http://triton.ori.u-tokyo.ac.jp/~intridge/wg-gdha.htm The most spectacular manifestation of seafloor hydrothermal circulation is, without doubt, the high-temperature (>400 °C) "black smokers" that expel fluids from the seafloor along all parts of the global ocean ridge crest. In addition to being visually compelling, vent fluids also exhibit important enrichments and depletions when compared to ambient seawater. Many of the dissolved chemicals released from the Earth's interior during venting precipitate upon mixing with the cold, overlying seawater, generating thick columns of black metal-sulfide and oxide mineral-rich smoke - hence the colloquial name for these vents: "black smokers" (Figure 4). In spite of their common appearance, high-temperature hydrothermal vent fluids actually exhibit a wide range of temperatures and chemical compositions, which are determined by subsurface reaction conditions. Despite their spectacular appearance, however, high-temperature vents may only represent a small fraction - perhaps as little as 10% - of the total hydrothermal heat flux close to ridge axes. A range of studies - most notably along the Juan de Fuca Ridge (JdFR) in the NE Pacific Ocean (Rona and Trivett, 1992; Schultz et al., 1992; Ginster et al., 1994) have suggested that, instead, axial hydrothermal circulation may be dominated by much lower-temperature diffuse flow exiting the seafloor at temperatures comparable to those first observed at the Galapagos vent sites in 1977. The relative importance of high- and low-temperature hydrothermal circulation to overall ocean chemistry remains a topic of active debate. (141K)Figure 4. (a) Photograph of a "black smoker" hydrothermal vent emitting hot (>400 °C) fluid at a depth of 2,834 m into the base of the oceanic water column at the Brandon vent site, southern EPR. The vent is instrumented with a recording temperature probe. (b) Diffuse flow hydrothermal fluids have temperatures that are generally <35 °C and, therefore, may host animal communities. This diffuse flow site at a depth of 2,500 m on the EPR at 9°50' N is populated by Riftia tubeworms, mussels, crabs, and other organisms. While most studies of seafloor hydrothermal systems have focused on the currently active plate boundary (˜0-1 Ma crust), pooled heat-flow data from throughout the world's ocean basins (Figure 1) indicate that convective heat loss from the oceanic lithosphere actually continues in crust from 0-65 Ma in age ( Stein et al., 1995). Indeed, most recent estimates would indicate that hydrothermal circulation through this older (1-65 Ma) section, termed "flank fluxes," may be responsible for some 70% or more of the total hydrothermal heat loss associated with spreading-plate boundaries - either in the form of warm (20-65 °C) altered seawater, or as cooler water, which is only much more subtly chemically altered ( Mottl, 2003).When considering the impact of hydrothermal circulation upon the chemical composition of the oceans and their underlying sediments, however, attention returns - for many elements - to the high-temperature "black smoker" systems. Only here do many species escape from the seafloor in high abundance. When they do, the buoyancy of the high-temperature fluids carries them hundreds of meters up into the overlying water column as they mix and eventually form nonbuoyant plumes containing a wide variety of both dissolved chemicals and freshly precipitated mineral phases. The processes active within these dispersing hydrothermal plumes play a major role in determining the net impact of hydrothermal circulation upon the oceans and marine geochemistry.

  5. Pool film boiling from rotating and stationary spheres in liquid nitrogen. [for SSME turbopump ball bearings

    NASA Technical Reports Server (NTRS)

    Cuan, Winston M.; Schwartz, Sidney H.

    1988-01-01

    Results are presented for a preliminary experiment involving a saturated pool boiling at 1 atm from rotating 2 and 3 inch diameter spheres which were immersed in LN2. Additional results are presented for a stationary 2 inch diameter sphere quenched in LN2, which were obtained with a more versatile and complete experimental apparatus. The speed of the rotational tests varied from 0 to 10,000 rpm. The stationary experiments parametrically varied pressure and subcooling levels from 0 to 600 psig and from 0 to 50 F, respectively. During the rotational tests, a high speed photographic analysis was undertaken to measure the thickness of the vapor film surrounding the sphere.

  6. Microheater Array Boiling Experiment

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; McQuillen, John; Balombin, Joe

    2002-01-01

    By conducting pool boiling tests in microgravity, the effect of buoyancy on the overall boiling process and the relative magnitude of other phenomena can be assessed. Data from KC-135 and sounding rocket experiments indicate little effect of gravity on boiling heat transfer at wall superheats below 25 C, despite vast differences in bubble behavior between gravity levels. In microgravity, a large primary bubble, surrounded by smaller satellite bubbles, moved over the surface, occasionally causing nucleation. Once formed, the primary bubble size remained constant for a given superheat, indicating evaporation at the bubble base is balanced with condensation on the bubble cap. The primary bubble's size increased with wall superheat. Most heaters under the primary bubble had low heat transfer rates, suggesting liquid dryout. Strong Marangoni convection developed in microgravity, forming a 'jet' into the bulk liquid that forced the bubble onto the heater. An experiment is being designed for the. Microgravity Science Glovebox. This experiment uses two 96 element microheater arrays, 2.7 and 7.0 mm in size. These heaters are individually controlled to operate at a constant temperature, measuring local heat fluxes as a function of time and space. Most boiling experiments operate at constant wall heat flux with larger heaters, allowing only time and space-averaged measurements. Each heater is about the bubble departure size in normal gravity, but significantly smaller than the bubble departure size in reduced gravity.

  7. Numerical Investigation of Boiling

    NASA Astrophysics Data System (ADS)

    Sagan, Michael; Tanguy, Sebastien; Colin, Catherine

    2012-11-01

    In this work, boiling is numerically investigated, using two phase flow direct numerical simulation based on a level set / Ghost Fluid method. Nucleate boiling implies both thermal issue and multiphase dynamics issues at different scales and at different stages of bubble growth. As a result, the different phenomena are investigated separately, considering their nature and the scale at which they occur. First, boiling of a static bubble immersed in an overheated liquid is analysed. Numerical simulations have been performed at different Jakob numbers in the case of strong density discontinuity through the interface. The results show a good agreement on bubble radius evolution between the theoretical evolution and numerical simulation. After the validation of the code for the Scriven test case, interaction of a bubble with a wall is studied. A numerical method taking into account contact angle is evaluated by comparing simulations of the spreading of a liquid droplet impacting on a plate, with experimental data. Then the heat transfer near the contact line is investigated, and simulations of nucleate boiling are performed considering different contact angles values. Finally, the relevance of including a model to take into account the evaporation of the micro layer is discussed.

  8. Critical discharge of initially subcooled water through slits. [PWR; BWR

    SciTech Connect

    Amos, C N; Schrock, V E

    1983-09-01

    This report describes an experimental investigation into the critical flow of initially subcooled water through rectangular slits. The study of such flows is relevant to the prediction of leak flow rates from cracks in piping, or pressure vessels, which contain sufficient enthalpy that vaporization will occur if they are allowed to expand to the ambient pressure. Two new analytical models, which allow for the generation of a metastable liquid phase, are developed. Experimental results are compared with the predictions of both these new models and with a Fanno Homogeneous Equilibrium Model.

  9. Sub-cooled liquid nitrogen cryogenic system with neon turbo-refrigerator for HTS power equipment

    NASA Astrophysics Data System (ADS)

    Yoshida, S.; Hirai, H.; Nara, N.; Ozaki, S.; Hirokawa, M.; Eguchi, T.; Hayashi, H.; Iwakuma, M.; Shiohara, Y.

    2014-01-01

    We developed a prototype sub-cooled liquid nitrogen (LN) circulation system for HTS power equipment. The system consists of a neon turbo-Brayton refrigerator with a LN sub-cooler and LN circulation pump unit. The neon refrigerator has more than 2 kW cooling power at 65 K. The LN sub-cooler is a plate-fin type heat exchanger and is installed in a refrigerator cold box. In order to carry out the system performance tests, a dummy cryostat having an electric heater was set instead of a HTS power equipment. Sub-cooled LN is delivered into the sub-cooler by the LN circulation pump and cooled within it. After the sub-cooler, sub-cooled LN goes out from the cold box to the dummy cryostat, and comes back to the pump unit. The system can control an outlet sub-cooled LN temperature by adjusting refrigerator cooling power. The refrigerator cooling power is automatically controlled by the turbo-compressor rotational speed. In the performance tests, we increased an electric heater power from 200 W to 1300 W abruptly. We confirmed the temperature fluctuation was about ±1 K. We show the cryogenic system details and performance test results in this paper.

  10. Visualization and void fraction measurement of decompressed boiling flow in a capillary tube

    NASA Astrophysics Data System (ADS)

    Asano, H.; Murakawa, H.; Takenaka, N.; Takiguchi, K.; Okamoto, M.; Tsuchiya, T.; Kitaide, Y.; Maruyama, N.

    2011-09-01

    A capillary tube is often used as a throttle for a refrigerating cycle. Subcooled refrigerant usually flows from a condenser into the capillary tube. Then, the refrigerant is decompressed along the capillary tube. When the static pressure falls below the saturation pressure for the liquid temperature, spontaneous boiling occurs. A vapor-liquid two-phase mixture is discharged from the tube. In designing a capillary tube, it is necessary to calculate the flow rate for given boundary conditions on pressure and temperature at the inlet and exit. Since total pressure loss is dominated by frictional and acceleration losses during two-phase flow, it is first necessary to specify the boiling inception point. However, there will be a delay in boiling inception during decompressed flow. This study aimed to clarify the boiling inception point and two-phase flow characteristics of refrigerant in a capillary tube. Refrigerant flows in a coiled copper capillary tube were visualized by neutron radiography. The one-dimensional distribution of volumetric average void fraction was measured from radiographs through image processing. From the void fraction distribution, the boiling inception point was determined. Moreover, a simplified CT method was successfully applied to a radiograph for cross-sectional measurements. The experimental results show the flow pattern transition from intermittent flow to annular flow that occurred at a void fraction of about 0.45.

  11. Subcooled choked flow through steam generator tube cracks

    NASA Astrophysics Data System (ADS)

    Wolf, Brian J.

    The work presented here describes an experimental investigation into the choked flow of initially subcooled water through simulated steam generator tube cracks at pressures up to 6.9 MPa. The study of such flow is relevant to the prediction of leak flow rates from a nuclear reactor primary side to secondary side through cracks in steam generator tubes. An experimental approach to measuring such flow is de- scribed. Experimental results from data found in literature as well as the data collected in this work are compared with predictions from presented models as well as predictions from the thermal-hydraulic system code RELAP5. It is found that the homogeneous equilibrium model underpredicts choked flow rates of subcooled water through slits and artificial steam generator tube cracks. Additional modeling of thermal non-equilibrium improves the predictibility of choking mass flux for homogeneous models, however they fail to account for the characteristics of the two-phase pressure drop. An integral modeling approach is enhanced using a correlation developed from the data herein. Also, an assessment of the thermal-hydraulics code RELAP5 is performed and it’s applicability to predict choking flow rates through steam generator tube cracks is addressed. This assessment determined that the Henry & Fauske model, as coded in RELAP5, is best suited for modeling choked flow through steam generator tube cracks. Finally, an approach to applying choked flow data that is not at the same thermo-dynamic conditions as a prototype is developed.

  12. Liquid metal boiling inception

    NASA Technical Reports Server (NTRS)

    Sabin, C. M.; Poppendiek, H. F.; Mouritzen, G.; Meckel, P. T.; Cloakey, J. E.

    1972-01-01

    An experimental study of the inception of boiling in potassium in forced convection is reported. The boiler consisted of a 0.19-inch inside diameter, niobium-1% zirconium boiler tube approximately six feet long. Heating was accomplished by direct electrical tube wall conduction. Experiments were performed with both all-liquid fill and two-phase fill startup sequences and with a range of flow rates, saturation temperatures, inert gas levels, and fill liquid temperatures. Superheat of the liquid above the equilibrium saturation temperature was observed in all the experiments. Incipient boiling liquid superheat ranged from a few degrees to several hundred. Comparisons of these data with other data and with several analytical treatments are presented.

  13. Investigations of Mechanisms Associated with Nucleate Boiling Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Dhir, Vijay K.; Hasan, M.; Chao, David (Technical Monitor)

    2003-01-01

    In this work a building block type of approach is used so that a basic understanding of the processes that contribute to nucleate boiling heat fluxes under microgravity conditions can be developed. This understanding will lead to development of a mechanistic model for nucleate boiling heat transfer which could eventually be used as a design tool in space applications. Task Description Task 1: Fabrication of the Experimental Setup. Under this task, the test section and liquid holding and viewing chambers will be fabricated. Artificial cylinder cavities will be formed on silicon wafers. A single cavity and two or four cavities, with a prescribed spacing and size, will be formed. The desired nucleation wall superheat will be used to determine the size of the mouth of the cavities. Task 2: Experiments. The basic experiments for flow and temperature field around single and multiple (2 or 4 separated or merged bubbles growing on downward facing or inclined surfaces) will be carried out under normal gravity conditions. The experiments will be conducted at one atmosphere pressure, but liquid subcooling will be varied from 0 to 30C. Water and PF-5050 will be used as test liquids. Task 3: Analytical/Numerical Models. In this task, transient temperature and flow field in vapor and liquid will be determined during growth of a single bubble. Analysis will include the evolution of the vapor-liquid interface and development of microlayer underneath the bubbles. For merged bubbles, detailed calculations of flow and temperature field will be carried out for transient shapes of vapor stems supporting a large bubble and the corresponding evaporation rate. Flow and temperature field for a bubble sliding along a heated wall will also be determined. Microgravity conditions will be simulated and a framework of a numerical tool for prediction of nucleate boiling heat fluxes under microgravity conditions will be developed. Task 4: Experiments in a KC-135. To understand bubble growth and detachment behavior of single or large merged bubbles, boiling experiments will be conducted under low gravity (10-2 g) conditions of the aircraft. In these experiments, 'designed' surfaces will be used. Visual observations and heat transfer data will be taken, but holography will not be used. The apparatus used for laboratory experiments will also be employed for experiments in the aircraft. Task 5: Experiments in the Space Shuttle. Effort will be devoted for defining a boiling experiment to be conducted on a 'designed' surface. The experiment will provide microgravity data on bubble growth and departure. These data are needed for development of a credible model for nucleate boiling heat fluxes under microgravity conditions. The heat transfer data will also be obtained and will be used to validate the models.

  14. Design inputs document: Boiling behavior during flow instability

    SciTech Connect

    Coutts, D.A.

    1991-01-01

    The coolant flow in a nuclear reactor core under normal operating conditions is kept as a subcooled liquid. This coolant is evenly distributed throughout the multiple flow channels with a uniform pressure profile across each coolant flow channel. If the coolant flow is reduced, the flow through individual channels will also decrease. A decrease in coolant flow will result in higher coolant temperatures if the heat flux is not reduced. When flow is significantly decreased, localized boiling may occur. This localized boiling can restrict coolant flow and the ability to transfer heat out of the reactor system. The maximum operating power for the reactor may be limited by how the coolant system reacts to a flow instability. One of the methods to assure safe operation during a reducing flow instability, is to operate at a power level below that necessary to initiate a flow excursion. Several correlations have been used to predict the conditions which precede a flow excursion. These correlations rely on the steady state behavior of the coolant and are based on steady state testing. This task will evaluate if there are any deviations between the actual transient flow excursion behavior and the flow excursion behavior based on steady state correlations (ONB, OSV, and CHF). Correlations will be developed which will allow a comparison between the time to excursive behavior predicted using steady state techniques and the actual time to excursive behavior.

  15. Design inputs document: Boiling behavior during flow instability

    SciTech Connect

    Coutts, D.A.

    1991-12-31

    The coolant flow in a nuclear reactor core under normal operating conditions is kept as a subcooled liquid. This coolant is evenly distributed throughout the multiple flow channels with a uniform pressure profile across each coolant flow channel. If the coolant flow is reduced, the flow through individual channels will also decrease. A decrease in coolant flow will result in higher coolant temperatures if the heat flux is not reduced. When flow is significantly decreased, localized boiling may occur. This localized boiling can restrict coolant flow and the ability to transfer heat out of the reactor system. The maximum operating power for the reactor may be limited by how the coolant system reacts to a flow instability. One of the methods to assure safe operation during a reducing flow instability, is to operate at a power level below that necessary to initiate a flow excursion. Several correlations have been used to predict the conditions which precede a flow excursion. These correlations rely on the steady state behavior of the coolant and are based on steady state testing. This task will evaluate if there are any deviations between the actual transient flow excursion behavior and the flow excursion behavior based on steady state correlations (ONB, OSV, and CHF). Correlations will be developed which will allow a comparison between the time to excursive behavior predicted using steady state techniques and the actual time to excursive behavior.

  16. Effect of Non-Condensable Gas on the Subcooled Water Critical Flow in a Safety Valve

    SciTech Connect

    Se Won Kim; Sang Kyoon Lee; Hee Cheon No

    2002-07-01

    The effect of non-condensable gas on the subcooled water critical flow in a safety valve is investigated experimentally at various sub-cooling with 3 different disk lifts. To evaluate its effect on the critical pressure ratio and critical flow rate, three parameters are considered: the ratios of outlet pressure to inlet pressure, the subcooling to inlet temperature, and the gas volumetric flow to water volumetric flow are 0.15-0.23, 0.07-0.12, and 0-0.8, respectively. It turns out that the critical pressure ratio is mainly dependent on the subcooling, and its dependency on the gas fraction and the pressure drop is relatively small. When the ratio of nitrogen gas volumetric flow to water volumetric flow becomes lower than 20%, the subcooled water critical flow rate is decreased about 10 % compare to the water flow rate of without non-condensable gas. However, it maintains a constant value after the ratio of gas volumetric flow to water volumetric flow becomes higher than 20%. The subcooled water critical flow correlation, which considers subcooling, disc lift, back-pressure, and non-condensable gas, shows good agreement with the total present experimental data with the root mean square error 8.17%. (authors)

  17. Liquid Acquisition Device Testing with Sub-Cooled Liquid Oxygen

    NASA Technical Reports Server (NTRS)

    Jurns, John M.; McQuillen, John B.

    2008-01-01

    When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth s gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMD) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. Previous experimental test programs conducted at NASA have collected LAD data for a number of cryogenic fluids, including: liquid nitrogen (LN2), liquid oxygen (LOX), liquid hydrogen (LH2), and liquid methane (LCH4). The present work reports on additional testing with sub-cooled LOX as part of NASA s continuing cryogenic LAD development program. Test results extend the range of LOX fluid conditions examined, and provide insight into factors affecting predicting LAD bubble point pressures.

  18. How Does Water Boil?

    NASA Astrophysics Data System (ADS)

    Zahn, Dirk

    2004-11-01

    Insight into the boiling of water is obtained from molecular dynamics simulations. The process is initiated by the spontaneous formation of small vacuum cavities in liquid water. By themselves, these defects are very short lived. If, however, several cavities occur at close distances, they are likely to merge into larger vacuum holes. At the liquid-vapor interfaces, single or small groups of water molecules tend to leave the liquid surface. Once the system is propagated beyond the transition state, these evaporation events outnumber the competing reintegration into the hydrogen-bonded network.

  19. Experimental study of boiling phenomena and heat transfer performances of FC-72 over micro-pin-finned silicon chips

    NASA Astrophysics Data System (ADS)

    Wei, J. J.; Guo, L. J.; Honda, H.

    2005-06-01

    Experiments were conducted to study the effects of micro-pin-fins on boiling phenomena and heat transfer from square simulated silicon chips immersed in a pool of FC-72. Two kinds of micro-pin-fins having fin thickness of 30 μm and fin heights of 60 and 200 μm, respectively, were fabricated on the silicon chip surface with the dry etching technique. The experiments were conducted at the liquid subcoolings of 3, 25, 35 and 45 K. The effects of dissolved air in FC-72 and chip orientation were also investigated. The boiling curve of the micro-pin-finned chips was characterized by a very small increase in wall superheat with increasing heat flux, and the wall temperatures at the CHF point for all the micro-pin-finned chips were less than the upper limit for the reliable operation of LSI chips (Tw=85°C). Liquid subcooling was very effective in elevating CHF for the micro-pin-finned chips compared to the smooth surface and other treated surfaces. The enhanced boiling heat transfer mechanisms for the micro-pin-finned chips were discussed.

  20. A high-fidelity approach towards simulation of pool boiling

    NASA Astrophysics Data System (ADS)

    Yazdani, Miad; Radcliff, Thomas; Soteriou, Marios; Alahyari, Abbas A.

    2016-01-01

    A novel numerical approach is developed to simulate the multiscale problem of pool-boiling phase change. The particular focus is to develop a simulation technique that is capable of predicting the heat transfer and hydrodynamic characteristics of nucleate boiling and the transition to critical heat flux on surfaces of arbitrary shape and roughness distribution addressing a critical need to design enhanced boiling heat transfer surfaces. The macro-scale of the phase change and bubble dynamics is addressed through employing off-the-shelf Computational Fluid Dynamics (CFD) methods for interface tracking and interphase mass and energy transfer. The micro-scale of the microlayer, which forms at early stage of bubble nucleation near the wall, is resolved through asymptotic approximation of the thin-film theory which provides a closed-form solution for the distribution of the micro-layer and its influence on the evaporation process. In addition, the sub-grid surface roughness is represented stochastically through probabilistic density functions and its role in bubble nucleation and growth is then represented based on the thermodynamics of nucleation process. This combination of deterministic CFD, local approximation, and stochastic representation allows the simulation of pool boiling on any surface with known roughness and enhancement characteristics. The numerical model is validated for dynamics and hydrothermal characteristics of a single nucleated bubble on a flat surface against available literature data. In addition, the prediction of pool-boiling heat transfer coefficient is verified against experimental measurements as well as reputable correlations for various roughness distributions and different surface orientations. Finally, the model is employed to demonstrate pool-boiling phenomenon on enhanced structures with reentrance cavities and to explore the effect of enhancement feature design on thermal and hydrodynamic characteristics of these surfaces.

  1. Evidence of Ni 2FeBO 5 and m-ZrO 2 precipitates in fuel rod deposits in AOA-affected high boiling duty PWR core

    NASA Astrophysics Data System (ADS)

    Sawicki, Jerzy A.

    2008-02-01

    This paper describes the characteristics of corrosion product deposits found in upper regions of high axial offset anomaly (AOA) once-burnt fuel assemblies after Cycle 9 in the Callaway pressurized water reactor (PWR). The ˜100-μm-thick deposits consisted of a new type of highly porous and structured Ni-, Fe-, B-, and Zr-rich material. The analyses showed that deposits contain a large amount (about 50 wt%) of Ni-Fe oxyborate (Ni 2FeBO 5, mineral name bonaccordite), in the form of matted ˜0.1-μm-thick and ˜10-μm-long, needle-like particles. An especially high density of Ni 2FeBO 5 needles was found in a 30-40-μm-thick zone on the clad side of the deposits. This compound has not previously been reported as a component of PWR fuel crud. Common fuel crud components such as nickel ferrite and nickel oxide were observed only in small quantities (about 10 wt%). Reference samples of Ni 2FeBO 5 were obtained by hydrothermal reactions in alkaline aqueous solutions starting from about 400 °C, or by sintering at about 1000 °C. Formation of Ni 2FeBO 5 has been identified as a new mechanism for boron retention and neutron absorption on PWR fuel. Aggregates of apparently hydrothermally precipitated ˜0.1-0.3-μm-sized particles of monoclinic m-ZrO 2(˜30 wt%) were found in the deposits, which is indicative of a dissolution-precipitation process at the cladding surface. This process may be enhanced by a LiOH concentration mechanism in crud, which is a result of both sub-cooled nucleate boiling and 10B(n,α) 7Li reactions. Consistently, the isotopic abundance of 10B in Ni 2FeBO 5 in crud samples was reduced to about 10% of the total boron.

  2. A Photographic Study on Flow Boiling of R-134a in a Vertical Channel

    SciTech Connect

    Bang, In Cheol; Chang, Soon Heung; Baek, Won-Pil

    2002-07-01

    The behavior of near-wall bubbles in subcooled flow boiling has been investigated photographically for R134a flow in vertical, one-side heated and rectangular channels at mass fluxes of 0, 190, 1000 and 2000 kg/m{sup 2}.s and inlet subcooling condition of 8 deg. C under 7 bar(T{sub sat} 27 deg. C). Digital photographic techniques and high-speed camera are used for the visualization, which have significantly advanced for recent decades. Primary attention is given to the bubble coalescence phenomena and the structure of the near-wall bubble layer. At subcooled and low quality conditions, discrete attached bubbles, sliding bubbles, small coalesced bubbles and large coalesced bubbles or vapor clots are observed on the heated surface as the heat flux is increased from a low value. Particularly in beginning of vapor formation, vapor remnants below discrete bubble on the heating surface are clearly observed. Nucleation site density increases with the increases in heat flux and channel-averaged enthalpy, while discrete bubbles coalesce and form large bubbles, resulting in large vapor clots. Waves formed on the surface of the vapor clots are closely related to Helmholtz instability. At CHF occurrence it is also observed that wall bubble layer beneath large vapor clots is removed and large film boiling occurs. Through the present visual test, it is observed that wall bubble layer begins to develop with the onset of nucleate boiling (ONB) and to extinguish with the occurrence of the CHF. It could be considered that this layer made an important role of CHF mechanism macroscopically. However, there may be another structure beneath wall bubbles which supplies specific information on CHF from viewpoint of microstructure based upon the observation of the liquid sublayer beneath coalesced bubbles. Through this microscopic visualization, it may be suggested that the following flow structures characterize the flow boiling phenomena: (a) vapor remnants as a continuous source of bubbles, (b) liquid sublayer depleted with bubble formation if there is not new supply of liquid, and (c) vapor clot as an obstructer blanketing liquid supply to sublayer in high heat flux. (authors)

  3. Subcooled-Water Nonstickiness of Condensate Microdrop Self-Propelling Nanosurfaces.

    PubMed

    Li, Juan; Luo, Yuting; Zhu, Jie; Li, Hong; Gao, Xuefeng

    2015-12-01

    We report perfect humidity-tolerant subcooled-water nonstickiness on condensate microdrop self-propelling (CMDSP) surfaces. As exemplified by a CMDSP nanoneedle surface, we find that impinged subcooled drops can instantly rebound and simultaneously take away surface condensate. Remarkably, continuously poured subcooled water can also shed off on the nanosample surface. In sharp contrast, they instantly freeze on the contrast flat hydrophobic surface. Such a superior performance may be ascribed to nanostructure-induced extremely low solid-liquid interface adhesion and prevention of phase transition from the liquid subcooled water to the solid ice. These findings help in the development of low-adhesive superhydrophobic surfaces suitable for a cold and humid environment. PMID:26584134

  4. Boil-off experiments with the EIR-NEPTUN Facility: Analysis and code assessment overview report

    SciTech Connect

    Aksan, S.N.; Stierli, F.; Analytis, G.T.

    1992-03-01

    The NEPTUN data discussed in this report are from core uncovery (boil-off) experiments designed to investigate the mixture level decrease and the heat up of the fuel rod simulators above the mixture level for conditions simulating core boil-off for a nuclear reactor under small break loss-of-coolant accident conditions. The first series of experiments performed in the NEPTUN test facility consisted of ten boil-off (uncovery) and one adiabatic heat-up tests. In these tests three parameters were varied: rod power, system pressure and initial coolant subcooling. The NEPTUN experiments showed that the external surface thermocouples do not cause a significant cooling influence in the rods to which they are attached under boil-off conditions. The reflooding tests performed later on indicated that the external surface thermocouples have some effect during reflooding for NEPTUN electrically heated rod bundle. Peak cladding temperatures are reduced by about 30--40C and quench times occur 20--70 seconds earlier than rods with embedded thermocouples. Additionally, the external surface-thermocouples give readings up to 20 K lower than those obtained with internal surface thermocouples (in the absence of external thermocouples) in the peak cladding temperature zone. Some of the boil-off data obtained from the NEPTUN test facility are used for the assessment of the thermal-hydraulic transient computer codes. These calculations were performed extensively using the frozen version of TRAC-BD1/MOD1 (version 22). A limited number of assessment calculations were done with RELAP5/MOD2 (version 36.02). In this report the main results and conclusions of these calculations are presented with the identification of problem areas in relation to models relevant to boil-off phenomena. On the basis of further analysis and calculations done, changing some of the models such as the bubbly/slug flow interfacial friction correlation which eliminate some of the problems are recommended.

  5. Design and test of a compact optics system for the pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Ling, Jerri S.; Laubenthal, James R.

    1990-01-01

    The experiment described seeks to improve the understanding of the fundamental mechanisms that constitute nucleate pool boiling. The vehicle for accomplishing this is an investigation, including tests to be conducted in microgravity and coupled with appropriate analyses, of the heat transfer and vapor bubble dynamics associated with nucleation, bubble growth/collapse and subsequent motion, considering the interrelations between buoyancy, momentum and surface tension which will govern the motion of the vapor and surrounding liquid, as a function of the heating rate at the heat transfer surface and the temperature level and distribution in the bulk liquid. The experiment is designed to be contained within the confines of a Get-Away-Special Canister (GAS Can) installed in the bay of the space shuttle. When the shuttle reaches orbit, the experiment will be turned on and testing will proceed automatically. In the proposed Pool Boiling Experiment a pool of liquid, initially at a precisely defined pressure and temperature, will be subjected to a step imposed heat flux from a semitransparent thin-film heater forming part of one wall of the container such that boiling is initiated and maintained for a defined period of time at a constant pressure level. Transient measurements of the heater surface and fluid temperatures near the surface will be made, noting especially the conditions at the onset of boiling, along with motion photography of the boiling process in two simultaneous views, from beneath the heating surface and from the side. The conduct of the experiment and the data acquisition will be completely automated and self-contained. For the initial flight, a total of nine tests are proposed, with three levels of heat flux and three levels of subcooling. The design process used in the development and check-out of the compact photographic/optics system for the Pool Boiling Experiment is documented.

  6. When water does not boil at the boiling point.

    PubMed

    Chang, Hasok

    2007-03-01

    Every schoolchild learns that, under standard pressure, pure water always boils at 100 degrees C. Except that it does not. By the late 18th century, pioneering scientists had already discovered great variations in the boiling temperature of water under fixed pressure. So, why have most of us been taught that the boiling point of water is constant? And, if it is not constant, how can it be used as a 'fixed point' for the calibration of thermometers? History of science has the answers. PMID:17336380

  7. Pressure drop, heat transfer, critical heat flux, and flow stability of two-phase flow boiling of water and ethylene glycol/water mixtures - final report for project "Efficent cooling in engines with nucleate boiling."

    SciTech Connect

    Yu, W.; France, D. M.; Routbort, J. L.

    2011-01-19

    Because of its order-of-magnitude higher heat transfer rates, there is interest in using controllable two-phase nucleate boiling instead of conventional single-phase forced convection in vehicular cooling systems to remove ever increasing heat loads and to eliminate potential hot spots in engines. However, the fundamental understanding of flow boiling mechanisms of a 50/50 ethylene glycol/water mixture under engineering application conditions is still limited. In addition, it is impractical to precisely maintain the volume concentration ratio of the ethylene glycol/water mixture coolant at 50/50. Therefore, any investigation into engine coolant characteristics should include a range of volume concentration ratios around the nominal 50/50 mark. In this study, the forced convective boiling heat transfer of distilled water and ethylene glycol/water mixtures with volume concentration ratios of 40/60, 50/50, and 60/40 in a 2.98-mm-inner-diameter circular tube has been investigated in both the horizontal flow and the vertical flow. The two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux of the test fluids were determined experimentally over a range of the mass flux, the vapor mass quality, and the inlet subcooling through a new boiling data reduction procedure that allowed the analytical calculation of the fluid boiling temperatures along the experimental test section by applying the ideal mixture assumption and the equilibrium assumption along with Raoult's law. Based on the experimental data, predictive methods for the two-phase pressure drop, the forced convective boiling heat transfer coefficient, and the critical heat flux under engine application conditions were developed. The results summarized in this final project report provide the necessary information for designing and implementing nucleate-boiling vehicular cooling systems.

  8. Theoretical and experimental study of inverted annular film boiling and regime transition during reflood transients

    NASA Astrophysics Data System (ADS)

    Mohanta, Lokanath

    The Loss of Coolant Accident (LOCA) is a design basis accident for light water reactors that usually determines the limits on core power. During a LOCA, film boiling is the dominant mode of heat transfer prior to the quenching of the fuel rods. The study of film boiling is important because this mode of heat transfer determines if the core can be safely cooled. One important film boiling regime is the so-called Inverted Annular Film Boiling (IAFB) regime which is characterized by a liquid core downstream of the quench front enveloped by a vapor film separating it from the fuel rod. Much research have been conducted for IAFB, but these studies have been limited to steady state experiments in single tubes. In the present work, subcooled and saturated IAFB are investigated using high temperature reflood data from the experiments carried out in the Rod Bundle Heat Transfer (RBHT) test facility. Parametric effects of system parameters including the pressure, inlet subcooling, and flooding rate on the heat transfer are investigated. The heat transfer behavior during transition to Inverted Slug Film Boiling (ISFB) regime is studied and is found to be different than that reported in previous studies. The effects of spacer grids on heat transfer in the IAFB and ISFB regimes are also presented. Currently design basis accidents are evaluated with codes in which heat transfer and wall drag must be calculated with local flow parameters. The existing models for heat transfer are applicable up to a void fraction of 0.6, i.e. in the IAFB regime and there is no heat transfer correlation for ISFB. A new semi-empirical heat transfer model is developed covering the IAFB and ISFB regimes which is valid for a void fraction up to 90% using the local flow variables. The mean absolute percentage error in predicting the RBHT data is 11% and root mean square error is 15%. This new semi-empirical model is found to compare well with the reflood data of FLECHT-SEASET experiments as well as data from single tube experiments. The root mean square error in predicting the FLECHT-SEASET data is 20% whereas for single tube data it is 12%. In previous studies, the transition criterion from the IAFB to the ISFB regime is purely empirical. In this work, a theoretical stability analysis of a liquid jet co-flowing with its vapor in a tube is carried out to seek a better understanding of the underlying physics of the regime transition. The effect of heat and mass transfer at the interface is included in the stability analysis. Also, the effect of viscous force is included in the stability analysis, by employing the viscous potential flow method. The wavelength that is responsible for breakup of the liquid core in IAFB is predicted in the present analysis and is compared with the adiabatic experiments of IAFB from the literature. The effects of various controlling parameters including the relative Weber number, vapor Reynolds number, velocity ratio, density ratio and viscosity ratio of vapor and liquid are studied to understand the physics of transition. Finally a physics-based heat transfer model is proposed for heat transfer in the ISFB regime using the wavelength obtained from the stability analysis. Keywords: Inverted annular film boiling, Two-phase heat transfer, Subcooled flow film boiling, Inverted slug film boiling, Regime transition, Void fraction in post CHF regime, Rod bundle, Spacer grid, Stability, Two-phase flow, Kelvin-Helmholtz instability, Capillary instability, Co-axial jets, Viscous potential flow, Interfacial heat and mass transfer.

  9. Film boiling of mercury droplets

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

    1975-01-01

    Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

  10. Film boiling of mercury droplets

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Schoessow, G. J.; Chmielewski, C. E.

    1975-01-01

    Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. Diffusion from the upper surface of the drop appears as a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

  11. Film boiling on spheres in single- and two-phase flows.

    SciTech Connect

    Liu, C.; Theofanous, T. G.

    2000-08-29

    Film boiling on spheres in single- and two-phase flows was studied experimentally and theoretically with an emphasis on establishing the film boiling heat transfer closure law, which is useful in the analysis of nuclear reactor core melt accidents. Systematic experimentation of film boiling on spheres in single-phase water flows was carried out to investigate the effects of liquid subcooling (from 0 to 40 C), liquid velocity (from 0 to 2 m/s), sphere superheat (from 200 to 900 C), sphere diameter (from 6 to 19 mm), and sphere material (stainless steel and brass) on film boiling heat transfer. Based on the experimental data a general film boiling heat transfer correlation is developed. Utilizing a two-phase laminar boundary-layer model for the unseparated front film region and a turbulent eddy model for the separated rear region, a theoretical model was developed to predict the film boiling heat transfer in all single-phase regimes. The film boiling from a sphere in two-phase flows was investigated both in upward two-phase flows (with void fraction from 0.2 to 0.65, water velocity from 0.6 to 3.2 m/s, and steam velocity from 3.0 to 9.0 m/s) and in downward two-phase flows (with void fraction from 0.7 to 0.95, water velocity from 1.9 to 6.5 m/s, and steam velocity from 1.1 to 9.0 m/s). The saturated single-phase heat transfer correlation was found to be applicable to the two-phase film boiling data by making use of the actual water velocity (water phase velocity), and an adjustment factor of (1 - {alpha}){sup 1/4} (with a being the void fraction) for downward flow case only. Slight adjustments of the Reynolds number exponents in the correlation provided an even better interpretation of the two-phase data. Preliminary experiments were also conducted to address the influences of multi-sphere structure on the film boiling heat transfer in single- and two-phase flows.

  12. High flux film and transition boiling

    SciTech Connect

    Witte, L.C.

    1990-01-01

    This report is a bench-scale experiment on transition boiling. The author gives a detailed description on experimental apparatus and conditions. The visual observed boiling phenomena; nucleate boiling and film boiling, and the effect of heat transfer are also elucidated. 10 refs., 11 figs., 1 tab.

  13. Numerical investigation on boiling flow of liquid nitrogen in a vertical tube using bubble number density approach

    NASA Astrophysics Data System (ADS)

    Shao, Xuefeng; Li, Xiangdong; Wang, Rongshun

    2016-04-01

    An average bubble number density (ABND) model was formulated and numerically resolved for the subcooled flow boiling of liquid nitrogen. The effects of bubble coalescence and breakup were taken into account. Some new closure correlations describing bubble nucleation and departure on the heating surface were selected as well. For the purpose of comparison, flow boiling of liquid nitrogen was also numerically simulated using a modified two-fluid model. The results show that the simulations performed by using the ABND model achieve encouraging improvement in accuracy in predicting heat flux and wall temperature of a vertical tube. Moreover, the influence of the bubble coalescence and breakup is shown to be great on predicting overall pressure beyond the transition point.

  14. Numerical investigation on boiling flow of liquid nitrogen in a vertical tube using bubble number density approach

    NASA Astrophysics Data System (ADS)

    Shao, Xuefeng; Li, Xiangdong; Wang, Rongshun

    2015-06-01

    An average bubble number density (ABND) model was formulated and numerically resolved for the subcooled flow boiling of liquid nitrogen. The effects of bubble coalescence and breakup were taken into account. Some new closure correlations describing bubble nucleation and departure on the heating surface were selected as well. For the purpose of comparison, flow boiling of liquid nitrogen was also numerically simulated using a modified two-fluid model. The results show that the simulations performed by using the ABND model achieve encouraging improvement in accuracy in predicting heat flux and wall temperature of a vertical tube. Moreover, the influence of the bubble coalescence and breakup is shown to be great on predicting overall pressure beyond the transition point.

  15. Super eruption environments make for "super" hydrothermal explosions: Extreme hydrothermal explosions in Yellowstone National Park

    NASA Astrophysics Data System (ADS)

    Morgan, L. A.; Shanks, W. P.; Pierce, K. L.

    2006-12-01

    Hydrothermal explosions are violent events resulting in the rapid ejection of boiling water, steam, mud, and rock fragments over areas that range from a few meters in diameter up to several kilometers in diameter. Hydrothermal explosions occur where shallow interconnected reservoirs of steam-saturated fluids underlie thermal fields. Sudden reduction in pressure causes the fluids to flash to steam resulting in significant expansion, rock fragmentation, and debris ejection. In Yellowstone, at least 20 large (>100 meters in diameter) hydrothermal explosions have been identified, and the scale of the individual events dwarfs similar features in other hydrothermal and geothermal areas of the world. Large explosions in Yellowstone have occurred over the past 16 ka at an interval of ~1 per every 700 yrs and similar events are likely to occur in the future. Our studies of hydrothermal explosive events indicate: 1) none are associated with magmatic or volcanic events; 2) several have been triggered by seismic events coupled with other processes; 3) lithic clasts and matrix from explosion deposits are extensively altered, indicating long-term, extensive hydrothermal mineralization in areas that were incorporated into the explosion deposit; 4) many lithic clasts in explosion breccia deposits contain evidence of repeated fracturing and cementation; and 4) dimensions of many documented large hydrothermal explosion craters in Yellowstone are similar to the dimensions of currently active geyser basins or thermal areas in Yellowstone. The vast majority of active thermal areas in Yellowstone are characterized by 1) high-temperature hot-water systems in areas of high heat-flow, 2) extensive systems of hot springs, fumaroles, geysers, sinter terraces, mud pots, and, in places, small hydrothermal explosion craters, 3) widespread alteration of host rocks, 4) large areal dimensions (>several 100 m) and 5) intermittent but long-lived activity (40,000 to 300,000 years). Critical requirements for large hydrothermal explosions are an interconnected system of well-developed joints and fractures along which hydrothermal fluids flow and a water-saturated system close to or at boiling temperatures. Important factors are the active deformation of the Yellowstone caldera, active faults and moderate seismicity, high heat flow, climate changes, and regional stresses. Ascending fluids flow along fractures that develop in response to active deformation of the Yellowstone caldera and along edges of impermeable rhyolitic lava flows. Alteration, self sealing, and dissolution further constrain the distribution and development of hydrothermal fields. A partial impermeable cap can contribute to the final over-pressurization. An abrupt drop in pressure initiates steam-flashing and is instantly transmitted through interconnected fractures, resulting in a series of multiple large-scale explosions and excavation of an explosion crater. Strong similarities between large hydrothermal explosion craters and thermal fields in Yellowstone may indicate that catastrophic failures leading to large hydrothermal explosions represent a unique phase in the life cycle of a geyser basin.

  16. Using noble gases measured in spring discharge to trace hydrothermal processes in the Norris Geyser Basin, Yellowstone National Park, U.S.A.

    USGS Publications Warehouse

    Gardner, W.P.; Susong, D.D.; Solomon, D.K.; Heasler, H.P.

    2010-01-01

    Dissolved noble gas concentrations in springs are used to investigate boiling of hydrothermal water and mixing of hydrothermal and shallow cool water in the Norris Geyser Basin area. Noble gas concentrations in water are modeled for single stage and continuous steam removal. Limitations on boiling using noble gas concentrations are then used to estimate the isotopic effect of boiling on hydrothermal water, allowing the isotopic composition of the parent hydrothermal water to be determined from that measured in spring. In neutral chloride springs of the Norris Geyser Basin, steam loss since the last addition of noble gas charged water is less than 30% of the total hydrothermal discharge, which results in an isotopic shift due to boiling of ?? 2.5% ??D. Noble gas concentrations in water rapidly and predictably change in dual phase systems, making them invaluable tracers of gas-liquid interaction in hydrothermal systems. By combining traditional tracers of hydrothermal flow such as deuterium with dissolved noble gas measurements, more complex hydrothermal processes can be interpreted. ?? 2010 Elsevier B.V.

  17. The Influence of the Heating Condition on the Void Fraction in a Boiling Channel

    NASA Astrophysics Data System (ADS)

    Umekawa, H.; Nakamura, S.; Fujiyoshi, S.; Ami, T.; Ozawa, M.; Saito, Y.; Ito, D.

    The void fraction profile in a boiling channel is essential in analyzing convective flow boiling, where several investigations have been conducted. But due to the difficulty in the treatment of the non-thermodynamic equilibrium phenomena under subcooled conditions, the issues in comprehensive void fraction profile has not been solved, yet. To improve the understanding of these phenomena, detailed measurement results are required. In this investigation, by using five kinds of test sections, i.e. I.D.=3 mm L=400 mm, I.D.=5 mm L=200, 400, 1000 mm, and I.D.=10 mm L=400 mm, the void fraction was measured quantitatively over the whole length. For the measurements, thermal neutron radiography at the B-4 port of the Kyoto University Research Reactor was used. This facility is designed for the visualization of forced convective flow boiling in vertical tubes. To introduce the performance of this facility, this paper presents the measurement results of void fraction and the estimation results briefly.

  18. Forced Convection Boiling and Critical Heat Flux of Ethanol in Electrically Heated Tube Tests

    NASA Technical Reports Server (NTRS)

    Meyer, Michael L.; Linne, Diane L.; Rousar, Donald C.

    1998-01-01

    Electrically heated tube tests were conducted to characterize the critical heat flux (transition from nucleate to film boiling) of subcritical ethanol flowing at conditions relevant to the design of a regeneratively cooled rocket engine thrust chamber. The coolant was SDA-3C alcohol (95% ethyl alcohol, 5% isopropyl alcohol by weight), and tests were conducted over the following ranges of conditions: pressure from 144 to 703 psia, flow velocities from 9.7 to 77 ft/s, coolant subcooling from 33 to 362 F, and critical heat fluxes up to 8.7 BTU/in(exp 2)/sec. For the data taken near 200 psia, critical heat flux was correlated as a function of the product of velocity and fluid subcooling to within +/- 20%. For data taken at higher pressures, an additional pressure term is needed to correlate the critical heat flux. It was also shown that at the higher test pressures and/or flow rates, exceeding the critical heat flux did not result in wall burnout. This result may significantly increase the engine heat flux design envelope for higher pressure conditions.

  19. Hydrothermal processes at Mount Rainier, Washington

    SciTech Connect

    Frank, D.G.

    1985-01-01

    Field studies and thermal-infrared mapping at Mount Rainier indicate areas of active hydrothermal alteration where excess surface heat flux is about 9 megawatts. Three representative settings include: (1) An extensive area (greater than 12,000 m/sup 2/) of heated ground and slightly acidic boiling-point fumaroles at 76-82/sup 0/C at East and West Craters on the volcano's summit; (2) A small area (less than 500 m/sup 2/) of heated ground and sub-boiling-point fumaroles at 55-60/sup 0/C on the upper flank at Disappointment Cleaver, and other probably similar areas at Willis Wall, Sunset Amphitheater, and the South Tahoma and Kautz headwalls; (3) Sulfate and carbon dioxide enriched thermal springs at 9-24/sup 0/C on the lower flank of the volcano in valley walls beside the Winthrop and Paradise Glaciers. In addition, chloride- and carbon dioxide-enriched thermal springs issue from thin sediments that overlie Tertiary rocks at, or somewhat beyond, the base of the volcanic edifice in valley bottoms of the Nisqually and Ohanapecosh Rivers where maximum spring temperatures are 19-25/sup 0/C, respectively, and where extensive travertine deposits have developed. The heat flow, distribution of thermal activity, and nature of alteration products indicate that a narrow, central hydrothermal system exists within Mount Rainier forming steam-heated snowmelt at the summit craters and localized leakage of steam-heated fluids within 2 kilometers of the summit. The lateral extent of the hydrothermal system is limited in that only sparse, neutral sulfate-enriched thermal water issues from the lower flank of the cone. Simulations of geochemical mass transfer suggest that the thermal springs may be derived from an acid sulfate-chloride parent fluid which has been neutralized by reaction with andesite and highly diluted with shallow ground water.

  20. Two-phase choked flow of subcooled nitrogen through a slit. [flow rate and pressure distribution

    NASA Technical Reports Server (NTRS)

    Simoneau, R. J.

    1974-01-01

    Two-phase choked flow rate and pressure distribution data are reported for subcooled nitrogen flowing through a slit. The slip was a narrow rectangular passage of equal length and width. The inlet stagnation pressure ranged from slightly above saturation to twice the thermodynamic critical pressure. Four stagnation isotherms were investigated covering a range which spanned the critical temperature. The results suggested a uniform two-phase flow pattern with vaporization occurring at or near the exit in most cases. The results compared favorably with the theory of Henry for nonequilibrium subcooled two-phase choked flow in long tubes.

  1. Dynamics of a two-dimensional vapor bubble confined between superheated or subcooled parallel plates.

    PubMed

    Das, Kausik S; Wilson, Stephen K

    2010-04-01

    The dynamics of a long, two-dimensional vapor bubble confined in the gap between two superheated or subcooled parallel plates is analyzed theoretically. The unsteady expansion and/or contraction of the bubble is driven by mass transfer between the liquid and the vapor. The analysis uses the approach developed by Wilson [J. Fluid Mech. 391, 1 (1999)] for a situation with "large" gaps and "small" superheating or subcooling to consider a situation with small gaps and large superheating or subcooling in which the mass transfer from or to the semicircular nose of the bubble is comparable to that from or to the thin liquid films on the plates. In order to permit a (semi-) analytical treatment the analysis is restricted to low Prandtl number liquids. When both plates are superheated the bubble always expands. In this case there are two possible constant-velocity continuous-film solutions for the expansion of the bubble, namely, an unstable fast mode and a stable slow mode. The evolution of the bubble is calculated numerically for a range of values of the parameters. In particular, these calculations show that eventually the bubble expands either with the constant velocity of the slow mode or exponentially. When both plates are subcooled the bubble always collapses to zero length in a finite time. When one plate is subcooled and the other plate is superheated the situation is rather more complicated. If the magnitude of the subcooling is less than that of the superheating then if the magnitude of the subcooling is greater than a critical value then a variety of complicated behaviors (including the possibility of an unexpected "waiting time" behavior in which the bubble remains almost stationary for a finite period of time) can occur before the bubble eventually collapses to a finite length in an infinite time, whereas if it is less than this critical value then the bubble always expands and eventually does so exponentially. If the magnitude of the subcooling is greater than that of the superheating then the bubble always collapses to zero length in a finite time. PMID:20481834

  2. Characteristics of Transient Boiling Heat Transfer

    SciTech Connect

    Liu, Wei; Monde, Masanori; Mitsutake, Y.

    2002-07-01

    In this paper, one dimensional inverse heat conduction solution is used for a measurement of pool boiling curve. The experiments are performed under atmospheric pressure for copper, brass, carbon steel and gold. Boiling curves, including unsteady transition boiling region, are found can be traced fairly well from a simple experiment system by solving inverse heat conduction solution. Boiling curves for steady heating and transient heating, for heating process and cooling process are compared. Surface behavior around CHF point, transition boiling and film-boiling regions are observed by using a high-speed camera. The results show the practicability of the inverse heat conduction solution in tracing boiling curve and thereby supply us a new way in boiling heat transfer research. (authors)

  3. Thermal and dynamic evolution of a spherical bubble moving steadily in a superheated or subcooled liquid

    NASA Astrophysics Data System (ADS)

    Legendre, Dominique; Borée, Jacques; Magnaudet, Jacques

    1998-06-01

    The heat transfer rate and the hydrodynamic forces experienced by a single vapor bubble of variable radius moving in a superheated or subcooled liquid are studied by means of numerical simulation. For that purpose the full Navier-Stokes equations and the temperature equation are solved in a frame of reference where the bubble surface is steady. The time evolution of the bubble radius is determined by solving the energy balance at the bubble surface. The numerical method is first validated by comparing present predictions with previous asymptotic or numerical results in the case where no relative motion between the liquid and the bubble exists. Then the situation where a constant relative velocity exists is considered. Effects of the mean flow on the heat transfer rate and on the bubble radius evolution are first discussed. Two different stages are generally observed in the computations. First, the radial motion induced by the displacement of the bubble surface dominates and the bubble evolution is essentially identical to the one observed in a liquid at rest. Then the ratio between the radial velocity and the translatory velocity decreases and the heat transfer rate becomes governed by streamwise advection effects. In this second stage a substantial increase of the growth or collapse rate of the bubble is observed, compared to the case of a liquid at rest. For a growing bubble it is shown that the complete process is successively described by the analytical solutions given by Scriven [Chem. Eng. Sci. 10, 1 (1959)] and Rückenstein [Chem. Eng. Sci. 10, 22 (1959)]. The situation is much less simple for a collapsing bubble and the reasons of this increased complexity are discussed. It is found that, when the heat transfer mechanism is dominated by streamwise advection, the bubble evolution and the collapse time predicted by the simulations agree well with the experimental results obtained by Chen and Mayinger [Int. J. Multiphase Flow 18, 877 (1992)]. Based on the present results, a general correlation giving the collapse time as a function of the characteristic parameters of the problem is proposed. The second contribution of the present work concerns the hydrodynamic force experienced by the bubble. Using a general decomposition procedure, the added mass effect and the viscous contribution are separately identified. It is first shown that the added mass coefficient is strictly constant and equal to one half, whatever the Reynolds number and the relative magnitude of the radial velocity. The viscous drag is then systematically compared with the quasisteady viscous drag corresponding to the instantaneous value of the Reynolds number. In situations of boiling, effects due to unsteadiness are found to exist during the first stages of the motion if the initial Reynolds number is not very large. In contrast, for a collapsing bubble, such effects remain significant all along the process because the relative importance of viscous phenomena increases in time. In both cases it is shown that the time variations of the bubble radius may affect deeply the viscous drag force. For example, when the radial velocity is high enough, the viscous drag force is found to be identical to the one corresponding to a potential flow, even if the instantaneous Reynolds number is low. These effects are discussed with the help of two asymptotic expressions of this force derived recently by Magnaudet and Legendre [Phys. Fluids 10, 550 (1998)] for a bubble with a time-dependent radius.

  4. D0 Silicon Upgrade: ASME Code and Pressure Calculations for Liquid Nitrogen Subcooler

    SciTech Connect

    Kuwazaki, Andrew; Leicht, Todd; /Fermilab

    1995-10-04

    Included in this engineering note are three separate calculation divisions. The first calculations are the determination of the required thickness of the LN{sub 2} subcooler flat head according to ASME code. This section includes Appendix A-C. The minimum plate thickness determined was 0.563 in. The actual thickness chosen in fabrication was a 3/4-inch plate milled to 0.594-inch at the bolt circle. Along with the plate thickness, this section calculates the required reinforcement area at the top plate penetrations. It was found that a 1/4-inch fillet weld at each penetration was adequate. The next set of calculations were done to prove that the subcooler internal pressure will always be less than 15 psig and therefore will not be classified as a pressure vessel. The subcooler is always open to a vent pipe. Appendix D calculations show that the vent pipe has a capacity of 1042 lbs/hr if 15 psig is present at the subcooler. It goes on to show that the inlet piping would at that flow rate, see a pressure drop of 104 psig. The maximum supply pressure of the LN{sub 2} storage dewar is 50 psig. Appendix E addresses required flow rates for steady state, loss of vacuum, or fire conditions. Page E9 shows a summary which states the maximum pressure would be 1.50 psig at fire conditions and internal pressure.

  5. The study of passive flow control device performance at low inlet subcooling

    NASA Astrophysics Data System (ADS)

    Liou, S. G.; Chen, I. Y.; Chang, S. K.

    1999-01-01

    Passive flow control devices (PFCDs) are normally used for flow measurement and flow regulation in many liquid flow systems. The typical PFCDs are venturis, orifices, nozzles, and capillary tubes. The PFCDs have several advantages over active flow control valves in thermal-fluid systems. They require no electrical power, data, command signal for operation and are not subject to wear or breakage, as well as the need of feedback control. When liquid flow venturi cavitates, it has the ability to passively control the flow in thermal-fluid systems at the choked flow regime. However, when the cavitating venturi (CV) operates at low value of inlet subcooling to conserve electrical power, an all-liquid overflow phenomenon can occur. If cavitation cannot be guaranteed in CV, then the constant flow rate performance of CV could not be obtained. Then, the CV may not be the best choice for the thermal-fluid control systems. For this reason, the main objective of this study is to evaluate the performance of possible PFCDs at low inlet subcooling. Experiments were performed for the alternate PFCDs of orifice, nozzle, and capillary tube at low levels of inlet subcooling in order to explore the physical phenomena of the PFCD relevant to their operation parameters. The test results of PFCDs are compared with CV's performance, and recommendations are made for the best type of passive flow control device at low inlet subcooling for the industrial and aerospace thermal-fluid control system applications.

  6. Transition from Pool to Flow Boiling: The Effect of Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Dhir, Vijay K.

    2004-01-01

    Applications of boiling heat transfer in space can be found in the areas of thermal management, fluid handling and control, power systems, on-orbit storage and supply systems for cryogenic propellants and life support fluids, and for cooling of electronic packages for power systems associated with various instrumentation and control systems. Recent interest in exploration of Mars and other planets, and the concepts of in-situ resource utiliLation on Mars highlights the need to understand the effect of gravity on boiling heat transfer at gravity levels varying from 1>= g/g(sub e) >=10(exp -6). The objective of the proposed work was to develop a mechanistic understanding of nucleate boiling and critical heat flux under low and micro-gravity conditions when the velocity of the imposed flow is small. For pool boiling, the effect of reduced gravity is to stretch both the length scale as well as the time scale for the boiling process. At high flow velocities, the inertia of the liquid determines the time and the length scales and as such the gravitational acceleration plays little role. However, at low velocities and at low gravity levels both liquid inertia and buoyancy are of equal importance. At present, we have little understanding of the interacting roles of gravity and liquid inertia on the nucleate boiling process. Little data that has been reported in the literature does not have much practical value in that it can not serve as a basis for design of heat exchange components to be used in space. Both experimental and complete numerical simulations of the low velocity, low-gravity nucleate boiling process were carried out. A building block type of approach was used in that first the growth and detachment process of a single bubble and flow and heat transfer associated with the sliding motion of the bubble over the heater surface after detachment was studied. Liquid subcooling and flow velocity were varied parametrically. The experiments were conducted at 1 g(sub e), while varying the orientation of surface with respect to the gravity vector. In the laboratory experiments, holographic interferometry was used to obtain data on velocity and temperature fields associated with a bubble prior to, and after detachment and during sliding motion. A test rig for conducting experiments in the KC-135 was developed, but experiments could not be conducted due to the unavailability of the aircraft prior to completion of the project. Numerical simulations modeling the micro and macro regions of the bubble were carried out in three dimensions. The results of the experiments were used to validate analytical/numerical models.

  7. A study of flow boiling phenomena using real time neutron radiography

    NASA Astrophysics Data System (ADS)

    Novog, David Raymond

    The operation and safety of both fossil-fuel and nuclear power stations depend on adequate cooling of the thermal source involved. This is usually accomplished using liquid coolants that are forced through the high temperature regions by a pumping system; this fluid then transports the thermal energy to another section of the power station. However, fluids that undergo boiling during this process create vapor that can be detrimental, and influence safe operation of other system components. The behavior of this vapor, or void, as it is generated and transported through the system is critical in predicting the operational and safety performance. This study uses two advanced penetrating radiation techniques, Real Time Neutron Radiography (RTNR), and High Speed X-Ray Tomography (HS-XCT), to examine void generation and transport behavior in a flow boiling system. The geometries studied were tube side flow boiling in a cylindrical configuration, and a similar flow channel with an internal twisted tape swirl flow generator. The heat transfer performance and pressure drop characteristics were monitored in addition to void distribution measurements, so that the impact of void distribution could be determined. The RTNR and heat transfer pipe flow studies were conducted using boiling Refrigerant 134a at pressures from 500 to 700 kPa, inlet subcooling from 3 to 12°C and mass fluxes from 55 to 170kg/m 2-s with heat fluxes up to 40 kW/m2. RTNR and HS-XCT were used to measure the distribution and size of the vapor phases in the channel for cylindrical tube-side flow boiling and swirl-flow boiling geometries. The results clearly show that the averaged void is similar for both geometries, but that there is a significant difference in the void distribution, velocity and transport behavior from one configuration to the next. Specifically, the void distribution during flow boiling in a cylindrical-tube test section showed that the void fraction was largest near the tube center and decreased with increasing radial distance. For swirling flow, the void concentration was highest in the center of each subchannel formed by the twisted tape insert, producing two local void maxima at each axial position. Furthermore, the instantaneous RTNR results show that the effects of bubble agglomeration change from one geometry to the next. To further examine the application of RTNR for void distribution measurement, both vertical and horizontal orientations were examined. These experimental results show similar cross sectional averaged axial distributions of the void fraction but significant differences in the local void behavior. The HS-XCT experiments were conducted on swirl-flow boiling of Refrigerant 123 at similar conditions as the RTNR experiments. These tests were conducted to qualitatively compare and verify the void distribution and behavior obtained using RTNR techniques. The HS-XCT results verify that during smooth flow boiling in a vertical tube the void tends to concentrate in the center of the channel and decrease outward to the channel walls. For swirl flow, the void tends to concentrate near the center of each subchannel formed by the twisted tape. Furthermore, wall region void fraction for smooth-flow boiling was significantly higher than swirling flow conditions due to the significant centrifugal forces present in swirl-flow. These centrifugal forces may improve the heat transfer and dryout behavior during swirl-flow conditions. This work contributes to the development of two-phase flow diagnostics based on penetrating radiative techniques, i.e., RTNR and HS-XCT for void distribution measurement, and enhances the knowledge of flow boiling systems. The application of HS-XCT and RTNR for the study of flow boiling phenomena using smooth and swirl-flow geometries has clearly demonstrated that differences in local void distribution result in differences in heat transfer behavior.

  8. Sub-cooled liquid helium flow supply for design D magnet cooling at MDTF. [Magnet Development and Test Facility

    SciTech Connect

    Ohmori, T.

    1986-07-01

    The parameters of the subcooled 4ATM helium flow from MTDF refrigerator and helium subcooler proposed to cool the SSC Design 'D' magnet is discussed. The system operating parameters are pressure - 4ATM and temperature - 4.35K. The higher than normal operating pressure is obtained by shutting down the cold turbine (T2) of MTDF refrigerator, and then not J-T the high pressure dense helium gas until after the magnet and liquid return line. The resultant helium temperature at the refrigerator outlet is described and the heat transfer tube length of the subcooler required to cool the flow to the ultimate desired temperature is evaluated.

  9. Computations of Boiling in Microgravity

    NASA Technical Reports Server (NTRS)

    Tryggvason, Gretar; Jacqmin, David

    1999-01-01

    The absence (or reduction) of gravity, can lead to major changes in boiling heat transfer. On Earth, convection has a major effect on the heat distribution ahead of an evaporation front, and buoyancy determines the motion of the growing bubbles. In microgravity, convection and buoyancy are absent or greatly reduced and the dynamics of the growing vapor bubbles can change in a fundamental way. In particular, the lack of redistribution of heat can lead to a large superheat and explosive growth of bubbles once they form. While considerable efforts have been devoted to examining boiling experimentally, including the effect of microgravity, theoretical and computational work is limited to very simple models. In this project, the growth of boiling bubbles is studied by direct numerical simulations where the flow field is fully resolved and the effects of inertia, viscosity, surface deformation, heat conduction and convection, as well as the phase change, are fully accounted for. The proposed work is based on previously funded NASA work that allowed us to develop a two-dimensional numerical method for boiling flows and to demonstrate the ability of the method to simulate film boiling. While numerical simulations of multi-fluid flows have been advanced in a major way during the last five years, or so, similar capability for flows with phase change are still in their infancy. Although the feasibility of the proposed approach has been demonstrated, it has yet to be extended and applied to fully three-dimensional simulations. Here, a fully three-dimensional, parallel, grid adaptive code will be developed. The numerical method will be used to study nucleate boiling in microgravity, with particular emphasis on two aspects of the problem: 1) Examination of the growth of bubbles at a wall nucleation site and the instabilities of rapidly growing bubbles. Particular emphasis will be put on accurately capturing the thin wall layer left behind as a bubble expands along a wall, on computing instabilities on bubble surfaces as bubbles grow, and on quantifying the effects of both these phenomena on heat transfer; and 2) Examination of the effect of shear flow on bubble growth and heat transfer.

  10. The behavior of vapor bubbles during boiling enhanced with acoustics and open microchannels

    NASA Astrophysics Data System (ADS)

    Boziuk, Thomas; Smith, Marc K.; Glezer, Ari

    2012-11-01

    Boiling heat transfer on a submerged heated surface is enhanced by combining a grid of surface micromachined open channels and ultrasonic acoustic actuation to control the formation and evolution of vapor bubbles and to inhibit the instability that leads to film boiling at the critical heat flux (CHF). The microchannels provide nucleation sites for vapor bubble formation and enable the entrainment of bulk subcooled fluid to these sites for sustained evaporation. Acoustic actuation excites interfacial oscillations of the detached bubbles and leads to accelerated condensation in the bulk fluid, thereby limiting the formation of vapor columns that precede the CHF instability. The combined effects of microchannels and acoustic actuation are investigated experimentally with emphasis on bubble nucleation, growth, detachment, and condensation. It is shown that this hybrid approach leads to a significant increase in the critical heat flux, a reduction of the vapor mass above the surface, and the breakup of low-frequency vapor slug formation. A large-scale model of the microchannel grid reveals details of the flow near the nucleation site and shows that the presence of the microchannels decreases the surface superheat at a given heat flux. Supported by ONR.

  11. Visualization Study of Growth of Spherical Bubble in He II Boiling under Microgravity Condition

    NASA Astrophysics Data System (ADS)

    Takada, Suguru; Kimura, Nobuhiro; Mamiya, Mikito; Nagai, Hideaki; Murakami, Masahide

    Under microgravityconditions, the heat transfer is considered to bedifferent from that in normal gravity becauseof zero subcooling due to zero hydrodynamic pressure in saturated He II. Thus the heat transfer in He II under microgravity is an interesting research target. Microgravity experiment is expected to reveal some hidden mechanism of boiling heat transfer acrossthe vapor-liquid interface because stable large-scale vapor bubblesare formed. In the present study, the behavior of a single spherical bubble generated by a micro heater was observed under microgravity conditionduring free fall in a drop tower for about 1.3 second. The visualized images taken by a high-speed camera were analyzed to examine the time variation of a large vapor bubble ofthe order of 10 mm. It was seen that the sizes of a single bubble increased with decreasing He II temperature for fixed heat input. The bubble size near the lambda temperature was smaller than that at 1.9 K though the effective thermal conductivity is quite small. The magnitude of the saturated vapor pressure seems to be a dominant factor to determine the bubble size. For the case of He I, the vapor bubble growth can be predicted by a simple consideration in terms of the latent heat and the gas density in film boiling state.

  12. Models and Stability Analysis of Boiling Water Reactors

    SciTech Connect

    John Dorning

    2002-04-15

    We have studied the nuclear-coupled thermal-hydraulic stability of boiling water reactors (BWRs) using a model that includes: space-time modal neutron kinetics based on spatial w-modes; single- and two-phase flow in parallel boiling channels; fuel rod heat conduction dynamics; and a simple model of the recirculation loop. The BR model is represented by a set of time-dependent nonlinear ordinary differential equations, and is studied as a dynamical system using the modern bifurcation theory and nonlinear dynamical systems analysis. We first determine the stability boundary (SB) - or Hopf bifurcation set- in the most relevant parameter plane, the inlet-subcooling-number/external-pressure-drop plane, for a fixed control rod induced external reactivity equal to the 100% rod line value; then we transform the SB to the practical power-flow map used by BWR operating engineers and regulatory agencies. Using this SB, we show that the normal operating point at 100% power is very stable, that stability of points on the 100% rod line decreases as the flow rate is reduced, and that operating points in the low-flow/high-power region are least stable. We also determine the SB that results when the modal kinetics is replaced by simple point reactor kinetics, and we thereby show that the first harmonic mode does not have a significant effect on the SB. However, we later show that it nevertheless has a significant effect on stability because it affects the basin of attraction of stable operating points. Using numerical simulations we show that, in the important low-flow/high-power region, the Hopf bifurcation that occurs as the SB is crossed is subcritical; hence, growing oscillations can result following small finite perturbations of stable steady-states on the 100% rod line at points in the low-flow/high-power region. Numerical simulations are also performed to calculate the decay ratios (DRs) and frequencies of oscillations for various points on the 100% rod line. It is determined that the U.S. NRC requirement of DR is not rigorously satisfied in the low-flow/high-power region; hence, this region should be avoided during normal startup and shutdown operations. The frequency of oscillation is shown to decrease as the flow rate is reduced. Moreover, the simulation frequency of 0.5Hz determined in the low-flow/high-power region is consistent with those observed during actual instability incidents. Additional numerical simulations show that in the low-flow/high-power region, for the same initial conditions, the use of point kinetics leads to damped oscillations, whereas the model that includes the modal neutron kinetics equations results in growing nonlinear oscillations.

  13. Study on condensation of a single vapor bubble into subcooled water-Part 2; Experimental analysis

    SciTech Connect

    Kamei, S.; Hirata, M. )

    1990-01-01

    This paper reports experimental analyses performed for the results of flow visualization in which saturated steam bubbles approximately 10 mm in diameter were injected into quiescent subcooled water. The patterns of bubble collapse were analyzed from photographs selected from a motion picture film and presented as the instantaneous bubble diameter vs. time. An upward motion was imparted to the bubbles by buoyancy, and because of heat transfer and condensation at the liquid-vapor interface, the bubbles diminished in size as they ascended. The time variations of the bubble diameter and position were determined from detailed analysis of the photographs. The experiments were performed for pressure levels from atmospheric to 10{sup 6}Pa and for temperature differences between the saturated steam and subcooled water from 10 to 70{degrees}C. From these, the time for bubbler collapse and the average heat transfer coefficient are inferred.

  14. Determination of heat transfer coefficient for an interaction of sub-cooled gas and metal

    NASA Astrophysics Data System (ADS)

    Zaidi Sidek, Mohd; Syahidan Kamarudin, Muhammad

    2016-02-01

    Heat transfer coefficient (HTC) for a hot metal surface and their surrounding is one of the need be defined parameter in hot forming process. This study has been conducted to determine the HTC for an interaction between sub-cooled gas sprayed on a hot metal surface. Both experiments and finite element have been adopted in this work. Initially, the designated experiment was conducted to obtain temperature history of spray cooling process. Then, an inverse method was adopted to calculate the HTC value before we validate in a finite element simulation model. The result shows that the heat transfer coefficient for interaction of subcooled gas and hot metal surface is 1000 W/m2K.

  15. Effects of subcooling and rod drop speed on the BWR rod drop accident

    SciTech Connect

    Cokinos, D.; Carew, J.; Aronson, A.

    1982-01-01

    The techniques and models used in the analysis of the control rod drop accident (CRDA) in a BWR have ranged from approximate conservative methods with a simple feedback model to detailed representations of the thermal-hydraulic and neutronic mechanisms. In a recent paper Cheng and Diamond presented a detailed evaluation of the CRDA and the effects of varying a number of important accident parameters. Their calculations performed with the BNL-TWIGL core dynamics code, have shown that the effect of inlet subcooling and rod drop speed play an important role in determining the severity of the rod drop accident. The purpose of the work summarized in this paper has been to determine in detail the dependence of the rod drop accident parameters on the (1) inlet subcooling; and (2) rod drop speed.

  16. Rate correlation for condensation of pure vapor on turbulent, subcooled liquid

    NASA Technical Reports Server (NTRS)

    Brown, J. Steven; Khoo, Boo Cheong; Sonin, Ain A.

    1990-01-01

    An empirical correlation is presented for the condensation of pure vapor on a subcooled, turbulent liquid with a shear-free interface. The correlation expresses the dependence of the condensation rate on fluid properties, on the liquid-side turbulence (which is imposed from below), and on the effects of buoyancy in the interfacial thermal layer. The correlation is derived from experiments with steam and water, but under conditions which simulate typical cryogenic fluids.

  17. Spray Cooling Modeling: Droplet Sub-Cooling Effect on Heat Transfer

    SciTech Connect

    Johnston, Joseph E.; Selvam, R. P.; Silk, Eric A.

    2008-01-21

    Spray cooling has become increasingly popular as a thermal management solution for high-heat flux (>100 W/cm{sup 2}) applications such as laser diodes and radars. Research has shown that using sub-cooled liquid can increase the heat flux from the hot surface. The objective of this study was to use a multi-phase numerical model to simulate the effect of a sub-cooled droplet impacting a growing vapor bubble in a thin (<100 {mu}m) liquid film. The two-phase model captured the liquid-vapor interface using the level set method. The effects of surface tension, viscosity, gravity and phase change were accounted for by using a modification to the incompressible Navier-Stokes equations, which were solved using the finite difference method. The computed liquid-vapor interface and temperature distributions were visualized for better understanding of the heat removal process. To understand the heat transfer mechanisms of sub-cooled droplet impact on a growing vapor bubble, various initial droplet temperatures were modeled (from 20 deg. C below saturation temperature to saturation temperature). This may provide insights into how to improve the heat transfer in future spray cooling systems.

  18. Compact counter-flow cooling system with subcooled gravity-fed circulating liquid nitrogen

    NASA Astrophysics Data System (ADS)

    Ivanov, Yu.; Radovinsky, A.; Zhukovsky, A.; Sasaki, A.; Watanabe, H.; Kawahara, T.; Hamabe, M.; Yamaguchi, S.

    2010-11-01

    A liquid nitrogen (LN2) is usually used to keep the high-temperature superconducting (HTS) cable low temperature. A pump is utilized to circulate LN2 inside the cryopipes. In order to minimize heat leakage, a thermal siphon circulation scheme can be realized instead. Here, we discuss the effectiveness of thermal siphon with counter-flow circulation loop composed of cryogen flow channel and inner cable channel. The main feature of the system is the existence of essential parasitic heat exchange between upwards and downwards flows. Feasibility of the proposed scheme for cable up to 500 m in length has been investigated numerically. Calculated profiles of temperature and pressure show small differences of T and p in the inner and the outer flows at the same elevation, which allows not worrying about mechanical stability of the cable. In the case under consideration the thermal insulating properties of a conventional electrical insulating material (polypropylene laminated paper, PPLP) appear to be sufficient. Two interesting effects were disclosed due to analysis of subcooling of LN2. In case of highly inclined siphon subcooling causes significant increase of temperature maximum that can breakup of superconductivity. In case of slightly inclined siphon high heat flux from outer flow to inner flow causes condensation of nitrogen gas in outer channel. It leads to circulation loss. Results of numerical analyses indicate that counter-flow thermosiphon cooling system is a promising way to increase performance of short-length power transmission (PT) lines, but conventional subcooling technique should be applied carefully.

  19. Cavitating venturi performance at low inlet subcooling: Normal operation, overflow and recovery of overflow

    SciTech Connect

    Ungar, E.K.; Dzenitis, J.M.; Sifuentes, R.T.

    1994-12-31

    Cavitating venturis (CVs) were to have been used to passively control the flow of liquid ammonia to the evaporators in the Space Station Freedom (SSF) two-phase active thermal control system (ATCS). Because the head rise of the SSF ATCS pump was low to conserve electrical power, the inlet subcooling at the cavitating venturi would have been lower than is the case in normal CV applications. Testing at NASA/Johnson Space Center has shown that when cavitating venturis are operated at low values of inlet subcooling (on the order of 100 kPa or 15 psid), an overflow phenomenon can occur. Here the flow is liquid throughout the venturi and flows at a higher mass flow rate than the cavitation limit. Once overflow occurs, cavitation is reestablished only when the downstream pressure is decreased to a low value. Overflow test data were obtained for six cavitating venturis with throat diameters between 0.28 and 1.83 mm (0.011 and 0.072 in). Analysis of the test result showed that overflow could not be sustained beyond a critical value of the superheat pressure at the cavitating venturi throat. In the present work, the phenomenon of overflow is explored and its implications for cavitating venturis in general applications and for applications similar to SSF are discussed. Recommendations are made for predicting the mode of operation of a cavitating venturi at low values of the inlet subcooling.

  20. Acoustic noise of a boiling liquid

    SciTech Connect

    Nesis, Y.I.

    1990-01-01

    This paper presents ideas on the mechanism of the emission of noise for different regimes of convective liquid boiling. Based on the analysis of experimental data, fundamental differences in the amplitude-frequency spectra of the acoustic noise accompanying these regimes are revealed as well as the nature of elementary sound emitters in a boiling liquid. Methods are indicated which allow one in principle to diagnose the regime of boiling in large reservoirs or cylindrical channels.

  1. Boiling significantly promotes photodegradation of perfluorooctane sulfonate.

    PubMed

    Lyu, Xian-Jin; Li, Wen-Wei; Lam, Paul K S; Yu, Han-Qing

    2015-11-01

    The application of photochemical processes for perfluorooctane sulfonate (PFOS) degradation has been limited by a low treatment efficiency. This study reports a significant acceleration of PFOS photodegradation under boiling condition compared with the non-boiling control. The PFOS decomposition rate increased with the increasing boiling intensity, but declined at a higher hydronium level or under oxygenation. These results suggest that the boiling state of solution resulted in higher effective concentrations of reactants at the gas-liquid interface and enhanced the interfacial mass transfer, thereby accelerating the PFOS decomposition. This study broadens our knowledge of PFOS photodegradation process and may have implications for development of efficient photodegradation technologies. PMID:26117498

  2. CHIMNEY FOR BOILING WATER REACTOR

    DOEpatents

    Petrick, M.

    1961-08-01

    A boiling-water reactor is described which has vertical fuel-containing channels for forming steam from water. Risers above the channels increase the head of water radially outward, whereby water is moved upward through the channels with greater force. The risers are concentric and the radial width of the space between them is somewhat small. There is a relatively low rate of flow of water up through the radially outer fuel-containing channels, with which the space between the risers is in communication. (AE C)

  3. Boils

    MedlinePlus

    ... Online Store Welcome Calendar of Events Find a Dermatology DO Osteopathic Medicine Disease Database Contributors Doctor Derm ... of Trustees Contact Us Ethics Foundation for Osteopathic Dermatology What is the FOD? Governance By-Laws Committees ...

  4. Catalytic Hydrothermal Gasification

    SciTech Connect

    Elliott, Douglas C.

    2015-05-31

    The term “hydrothermal” used here refers to the processing of biomass in water slurries at elevated temperature and pressure to facilitate the chemical conversion of the organic structures in biomass into useful fuels. The process is meant to provide a means for treating wet biomass materials without drying and to access ionic reaction conditions by maintaining a liquid water processing medium. Typical hydrothermal processing conditions are 523-647K of temperature and operating pressures from 4-22 MPa of pressure. The temperature is sufficient to initiate pyrolytic mechanisms in the biopolymers while the pressure is sufficient to maintain a liquid water processing phase. Hydrothermal gasification is accomplished at the upper end of the process temperature range. It can be considered an extension of the hydrothermal liquefaction mechanisms that begin at the lowest hydrothermal conditions with subsequent decomposition of biopolymer fragments formed in liquefaction to smaller molecules and eventually to gas. Typically, hydrothermal gasification requires an active catalyst to accomplish reasonable rates of gas formation from biomass.

  5. Lattice Boltzmann modeling of boiling heat transfer: The boiling curve and the effects of wettability

    DOE PAGESBeta

    Li, Q.; Kang, Q. J.; Francois, M. M.; He, Y. L.; Luo, K. H.

    2015-03-03

    A hybrid thermal lattice Boltzmann (LB) model is presented to simulate thermal multiphase flows with phase change based on an improved pseudopotential LB approach (Li et al., 2013). The present model does not suffer from the spurious term caused by the forcing-term effect, which was encountered in some previous thermal LB models for liquid–vapor phase change. Using the model, the liquid–vapor boiling process is simulated. The boiling curve together with the three boiling stages (nucleate boiling, transition boiling, and film boiling) is numerically reproduced in the LB community for the first time. The numerical results show that the basic featuresmore » and the fundamental characteristics of boiling heat transfer are well captured, such as the severe fluctuation of transient heat flux in the transition boiling and the feature that the maximum heat transfer coefficient lies at a lower wall superheat than that of the maximum heat flux. Moreover, the effects of the heating surface wettability on boiling heat transfer are investigated. It is found that an increase in contact angle promotes the onset of boiling but reduces the critical heat flux, and makes the boiling process enter into the film boiling regime at a lower wall superheat, which is consistent with the findings from experimental studies.« less

  6. Lattice Boltzmann modeling of boiling heat transfer: The boiling curve and the effects of wettability

    SciTech Connect

    Li, Q.; Kang, Q. J.; Francois, M. M.; He, Y. L.; Luo, K. H.

    2015-03-03

    A hybrid thermal lattice Boltzmann (LB) model is presented to simulate thermal multiphase flows with phase change based on an improved pseudopotential LB approach (Li et al., 2013). The present model does not suffer from the spurious term caused by the forcing-term effect, which was encountered in some previous thermal LB models for liquid–vapor phase change. Using the model, the liquid–vapor boiling process is simulated. The boiling curve together with the three boiling stages (nucleate boiling, transition boiling, and film boiling) is numerically reproduced in the LB community for the first time. The numerical results show that the basic features and the fundamental characteristics of boiling heat transfer are well captured, such as the severe fluctuation of transient heat flux in the transition boiling and the feature that the maximum heat transfer coefficient lies at a lower wall superheat than that of the maximum heat flux. Moreover, the effects of the heating surface wettability on boiling heat transfer are investigated. It is found that an increase in contact angle promotes the onset of boiling but reduces the critical heat flux, and makes the boiling process enter into the film boiling regime at a lower wall superheat, which is consistent with the findings from experimental studies.

  7. COMBUSTION OF HYDROTHERMALLY TREATED COALS

    EPA Science Inventory

    The report gives results of an evaluation of: (1) the relationship of the combustion characteristics of hydrothermally treated (HTT) coals to environmental emissions, boiler design, and interchangeability of solid fuels produced by the Hydrothermal Coal Process (HCP) with raw coa...

  8. An experimental investigation of liquid methane convection and boiling in rocket engine cooling channels

    NASA Astrophysics Data System (ADS)

    Trujillo, Abraham Gerardo

    In the past decades, interest in developing hydrocarbon-fueled rocket engines for deep spaceflight missions has continued to grow. In particular, liquid methane (LCH4) has been of interest due to the weight efficiency, storage, and handling advantages it offers over several currently used propellants. Deep space exploration requires reusable, long life rocket engines. Due to the high temperatures reached during combustion, the life of an engine is significantly impacted by the cooling system's efficiency. Regenerative (regen) cooling is presented as a viable alternative to common cooling methods such as film and dump cooling since it provides improved engine efficiency. Due to limited availability of experimental sub-critical liquid methane cooling data for regen engine design, there has been an interest in studying the heat transfer characteristics of the propellant. For this reason, recent experimental studies at the Center for Space Exploration Technology Research (cSETR) at the University of Texas at El Paso (UTEP) have focused on investigating the heat transfer characteristics of sub-critical CH4 flowing through sub-scale cooling channels. To conduct the experiments, the csETR developed a High Heat Flux Test Facility (HHFTF) where all the channels are heated using a conduction-based thermal concentrator. In this study, two smooth channels with cross sectional geometries of 1.8 mm x 4.1 mm and 3.2 mm x 3.2 mm were tested. In addition, three roughened channels all with a 3.2 mm x 3.2 mm square cross section were also tested. For the rectangular smooth channel, Reynolds numbers ranged between 68,000 and 131,000, while the Nusselt numbers were between 40 and 325. For the rough channels, Reynolds numbers ranged from 82,000 to 131,000, and Nusselt numbers were between 65 and 810. Sub-cooled film-boiling phenomena were confirmed for all the channels presented in this work. Film-boiling onset at Critical Heat Flux (CHF) was correlated to a Boiling Number (Bo) of approximately 0.1 for all channels. Convective Nusselt number follows predicted trends for Reynolds number with a wall temperature correction for both the boiling and non-boiling regimes.

  9. Boiling Fluids Behave Quite Differently in Space - Duration: 19 seconds.

    NASA Video Gallery

    The boiling process is really different in space, since the vapor phase of a boiling liquid does not rise via buoyancy. Spacecraft and Earth-based systems use boiling to efficiently remove large am...

  10. Pool Boiling Experiment Has Successful Flights

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Pool Boiling Experiment (PBE) is designed to improve understanding of the fundamental mechanisms that constitute nucleate pool boiling. Nucleate pool boiling is a process wherein a stagnant pool of liquid is in contact with a surface that can supply heat to the liquid. If the liquid absorbs enough heat, a vapor bubble can be formed. This process occurs when a pot of water boils. On Earth, gravity tends to remove the vapor bubble from the heating surface because it is dominated by buoyant convection. In the orbiting space shuttle, however, buoyant convection has much less of an effect because the forces of gravity are very small. The Pool Boiling Experiment was initiated to provide insight into this nucleate boiling process, which has many Earthbound applications, such as steam-generation power plants, petroleum, and other chemical plants. Also, by using the test fluid R-113, the Pool Boiling Experiment can provide some basic understanding of the boiling behavior of cryogenic fluids without the large cost of an experiment using an actual cryogen.

  11. Pool Boiling Experiment Has Five Successful Flights

    NASA Technical Reports Server (NTRS)

    Chiaramonte, Fran

    1997-01-01

    The Pool Boiling Experiment (PBE) is designed to improve understanding of the fundamental mechanisms that constitute nucleate pool boiling. Nucleate pool boiling is a process wherein a stagnant pool of liquid is in contact with a surface that can supply heat to the liquid. If the liquid absorbs enough heat, a vapor bubble can be formed. This process occurs when a pot of water boils. On Earth, gravity tends to remove the vapor bubble from the heating surface because it is dominated by buoyant convection. In the orbiting space shuttle, however, buoyant convection has much less of an effect because the forces of gravity are very small. The Pool Boiling Experiment was initiated to provide insight into this nucleate boiling process, which has many earthbound applications in steamgeneration power plants, petroleum plants, and other chemical plants. In addition, by using the test fluid R-113, the Pool Boiling Experiment can provide some basic understanding of the boiling behavior of cryogenic fluids without the large cost of an experiment using an actual cryogen.

  12. Hydrothermal pretreatment of coal

    SciTech Connect

    Loo, Bock; Ross, D.S.

    1990-08-14

    We are examining the effects on composition and behavior of Argonne-supplied Wyodak coal under both thermal (no added water/N{sub 2}) and hydrothermal (liquid water/N{sub 2}) conditions at 350{degree}C for periods of 30 min and 5 hr, with emphasis during this period on the longer treatment. Field ionization mass spectrometry (FIMS) of the untreated, thermally treated, and hydrothermally treated coals is conducted at conditions where the samples are heated from ambient to 500{degree}C at 2.5{degree}/min. In the 5 hr work the volatilities of the coals are 24%, 16%, and 25% respectively. Solvent swelling studies with the recovered coals do not demonstrate the expected lower degree of crosslinking in the hydrothermal case. Both the thermal and hydrothermal treatments yield products with a decreased swelling ratio, but the ratio for the product from the aqueous treatment is slightly lower than that from thermal treatment. At present we cannot reconcile this result with our other data. 4 refs., 6 figs.

  13. Computations of Boiling in Microgravity

    NASA Technical Reports Server (NTRS)

    Tryggvason, G.; Jacqmin, Dave

    2000-01-01

    The absence (or reduction) of gravity, can lead to major changes in boiling heat transfer. On Earth, convection has a major effect on the heat distribution ahead of an evaporation front, and buoyancy determines the motion of the growing bubbles. In microgravity, convection and buoyancy are absent or greatly reduced and the dynamics of the growing vapor bubbles can change in a fundamental way. In particular, the lack of redistribution of heat can lead to a large superheat and explosive growth of bubbles once they form. While considerable efforts have been devoted to examining boiling experimentally, including the effect of microgravity, theoretical and computational work have been limited. Here, the growth of boiling bubbles is studied by direct numerical simulations where the flow field is fully resolved and the effects of inertia, viscosity, surface deformation, heat conduction and convection, as well as the phase change, are fully accounted for. Boiling involves both fluid flow and heat transfer and thus requires the solution of the Navier-Stokes and the energy equations. The numerical method is based on writing one set of governing transport equations which is valid in both the liquid and vapor phases. This local, single-field formulation incorporates the effect of the interface in the governing equations as source terms acting only at the interface. These sources account for surface tension and latent heat in the equations for conservation of momentum and energy as well as mass transfer across the interface due to phase change. The single-field formulation naturally incorporates the correct mass, momentum and energy balances across the interface. Integration of the conservation equations across the interface directly yields the jump conditions derived in the local instant formulation for two-phase systems. In the numerical implementation, the conservation equations for the whole computational domain (both vapor and liquid) are solved using a stationary grid and the phase boundary is followed by a moving unstructured two-dimensional grid. While two-dimensional simulations have been used for preliminary studies and to examine the resolution requirement, the focus is on fully three-dimensional simulations. The numerical methodology, including the parallelization and grid refinement strategy is discussed, and preliminary results shown. For buoyancy driven flow, the heat transfer is in good agreement with experimental correlations. The changes when gravity is turned off and/or fluid shear is added are discussed, as well as the difference between simulations of a layer freely releasing bubbles versus simulations using only one wavelength initial perturbation. Figure 1 shows the early stages of the formation of a three-dimensional bubble from a thin vapor layer. The boundary conditions are periodic in the x and y direction, the bottom is a hot and the top allows a free outflow. The jagged edge of the surface close to the bottom of the computational domain is due to some of the surface elements being on the other side of the domain and some elements not plotted by our plotting routine. In the second figure, we show the temperature distribution through two perpendicular planes.

  14. Dryout and Rewetting in the Pool Boiling Experiment Flown on STS-72 (PBE-2 B) and STS-77 (PBE-2 A)

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.; Lee, Ho Sung; Keller, Robert B.

    1998-01-01

    Experiments were conducted in the microgravity of space in which a pool of liquid (R-113), initially at a precisely defined pressure and temperature, is subjected to a step imposed heat flux from a semi-transparent thin-film heater forming part of one wall of the container such that boiling is initiated and maintained for a defined period of time at a constant pressure level. A total of nine tests were conducted at three levels of heat flux and three levels of subcooling in each of the two space experiments in a GAS canister on the STS-77, -72, respectively. Three (3) modes of propagation of boiling across the heater surface and subsequent vapor bubble growths were observed, in addition to the two (2) modes observed in the previous microgravity pool boiling space flights on STS-47, -57, and -60. Of particular interest were the extremely dynamic or "explosive" growths, which were determined to be the consequence of the large increase in the liquid-vapor interface area associated with the appearance of a corrugated or rough interface. Predictions of circumstances for its onset have been carried out. Assumptions were necessary regarding the character of disturbances necessary for the instabilities to grow. Also, a new vapor bubble phenomena was observed in which small vapor bubbles migrated toward a larger bubble, eventually coalescing with this larger bubble. The heat transfer was enhanced approximately 30% as a result of these migrating bubbles, which is believed to be a vapor bubble manifestation of Marangoni convection and/or molecular momentum effects, sometimes referred to as vapor recoil. The circumstances of heat flux and liquid subcooling necessary to produce heater surface dryout for an initially stagnant liquid subjected to an imposed heat flux have been more closely identified.

  15. Cryostabilization of high-temperature superconducting magnets with subcooled flow in microchannels

    SciTech Connect

    Cha, Y.S.; Hull, J.R.; Choi, U.S.

    1992-07-06

    Subcooled flow of liquid nitrogen in microchannels is proposed as a means to enhance the stability of a superconducting magnet. Analysis shows high current density or a low stabilizer fraction is obtainable in a cryostable magnet. Increase in stability (using the Stekley criterion) is directly related to coolant velocity and coolant channel aspect ratio, however, there is a corresponding increase in pressure drop of the system. Another constraint is the coolant temperature rise, which is found to be a function of coolant residence time and the coolant to conductor ratio.

  16. Boiling Heat Transfer to Halogenated Hydrocarbon Refrigerants

    NASA Astrophysics Data System (ADS)

    Yoshida, Suguru; Fujita, Yasunobu

    The current state of knowledge on heat transfer to boiling refrigerants (halogenated hydrocarbons) in a pool and flowing inside a horizontal tube is reviewed with an emphasis on information relevant to the design of refrigerant evaporators, and some recommendations are made for future research. The review covers two-phase flow pattern, heat transfer characteristics, correlation of heat transfer coefficient, influence of oil, heat transfer augmentation, boiling from tube-bundle, influence of return bend, burnout heat flux, film boiling, dryout and post-dryout heat transfer.

  17. Significant role of climatic trends on hydrothermal activity Coso Hot Springs, California

    SciTech Connect

    Lofgren, B.E. )

    1990-05-01

    The hydrothermal features of Coso Hot Springs have attracted visitors for 130 yr and scientific investigators for two decades. In 1978, anticipating effects of major geothermal developments nearby, the Naval Weapons Center (NWC) initiated a comprehensive monitoring program at a dozen hydrothermal sites in the Coso Hot Springs area. Nine years of monitoring preceded power production in the nearby Coso geothermal field in July 1987. During this period, steam was rising from numerous vents and gently boiling mud pots. Local rainfall caused increased boiling activity in several mud pots, with some overflowing during wet periods. Then in August 1988, a year after geothermal power production began major changes in hot spring activity commenced. Small mud pots and steamers started to grow and coalesce. In March 1989, mud-pot activity became more violent. Many buried wells failed causing surface activity in other areas to diminish. During ensuing months, large mud cones developed and much of the steam and boiling water occurred in a few major pots. Because the abrupt changes in hydrothermal activity followed so closely after nearby geothermal production began, the obvious cause has been attributed to geothermal developments. Studies of NWC baseline monitoring data indicate, however, that no effects of geothermal developments have been felt in the hot springs area. Rainfall and barometric effects account for most of the fluctuations in records of the past decade. Early accounts and field evidence suggest similar changes have occurred in the past.

  18. Hydrothermal reactivity of saponite.

    USGS Publications Warehouse

    Whitney, G.

    1983-01-01

    The nature and extent of the reactions of synthetic Fe-free saponite have been investigated under experimental hydrothermal conditions as a first step towards understanding saponite reactivity under relatively simple conditions. Saponite crystallizes from amorphous gel of ideal saponite composition within 7 days at 300o-550oC under P = 1 kbar. Reactions subsequent to this initial crystallization depend on reaction T and interlayer cations. Saponite is found to react hydrothermally, over a period of 200 days, at T down to 400oC, at least 150oC lower than previously reported, but showed no signs of reaction below 400oC. At 450oC, a mixture of talc/saponite and saponite/phlogopite clays forms from K-saponite via intracrystalline layer transformations, while above 450oC the initial K-saponite dissolves, with talc and phlogopite forming as discrete phases. After 200 days reactions at 400-450oC were not complete, so that given sufficient time to reach equilibrium, a lower hydrothermal stability limit for saponite is possible. Further study of the Fe-bearing saponite system will be required before experimental results can be applied to natural systems.-D.F.B.

  19. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  20. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  1. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  2. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Boiling water sterilizer. 872.6710 Section 872...) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device that consists of a container for boiling...

  3. Conceptual design for spacelab pool boiling experiment

    NASA Technical Reports Server (NTRS)

    Lienhard, J. H.; Peck, R. E.

    1978-01-01

    A pool boiling heat transfer experiment to be incorporated with a larger two-phase flow experiment on Spacelab was designed to confirm (or alter) the results of earth-normal gravity experiments which indicate that the hydrodynamic peak and minimum pool boiling heat fluxes vanish at very low gravity. Twelve small sealed test cells containing water, methanol or Freon 113 and cylindrical heaters of various sizes are to be built. Each cell will be subjected to one or more 45 sec tests in which the surface heat flux on the heaters is increased linearly until the surface temperature reaches a limiting value of 500 C. The entire boiling process will be photographed in slow-motion. Boiling curves will be constructed from thermocouple and electric input data, for comparison with the motion picture records. The conduct of the experiment will require no more than a few hours of operator time.

  4. SUPERHEATING IN A BOILING WATER REACTOR

    DOEpatents

    Treshow, M.

    1960-05-31

    A boiling-water reactor is described in which the steam developed in the reactor is superheated in the reactor. This is accomplished by providing means for separating the steam from the water and passing the steam over a surface of the fissionable material which is not in contact with the water. Specifically water is boiled on the outside of tubular fuel elements and the steam is superheated on the inside of the fuel elements.

  5. Visualizational study on nucleate pool boiling phenomena

    NASA Astrophysics Data System (ADS)

    Kamei, Shuya

    1993-01-01

    It is important to visualize the intricate bubble behavior and the strong agitation of liquid near the heating surface to clarify the details concerning boiling mechanism. The visualization of nucleate pool boiling phenomena was confirmed by means of shadowgraphy using a still- camera (Nikon Photomic Camera) with the speed of 2000 frames per second. Illumination was provided by a photo spotlight or a stroboscope. The photographs show that the boiling phenomena and bubbles' behavior are varied for the heat flux of nucleate pool boiling based on the experiments. By considering the effect of revolving angle and the influence of a space between a tube and a tube, experiments have been carried out to investigate the nucleate pool boiling phenomena on horizontal stainless-steel-multi-tube in saturated distilled water. These experiments were performed for atmospheric pressure, for a stainless-tube diameter of 1.0 mm for a length of 80 mm, for a region of natural convection to nucleate boiling near burnout. From these results, photographs show that the successive motion and shape of bubbles during their process of detachment on the heating tube surface varied with increasing heat flux.

  6. Experimental and analytical study of stability characteristics of natural circulation boiling water reactors during startup transient

    NASA Astrophysics Data System (ADS)

    Woo, Kyoungsuk

    Two-phase natural circulation loops are unstable at low pressure operating conditions. New reactor design relying on natural circulation for both normal and abnormal core cooling is susceptible to different types of flow instabilities. In contrast to forced circulation boiling water reactor (BWR), natural circulation BWR is started up without recirculation pumps. The tall chimney placed on the top of the core makes the system susceptible to flashing during low pressure start-up. In addition, the considerable saturation temperature variation may induce complicated dynamic behavior driven by thermal non-equilibrium between the liquid and steam. The thermal-hydraulic problems in two-phase natural circulation systems at low pressure and low power conditions are investigated through experimental methods. Fuel heat conduction, neutron kinetics, flow kinematics, energetics and dynamics that govern the flow behavior at low pressure, are formulated. A dimensionless analysis is introduced to obtain governing dimensionless groups which are groundwork of the system scaling. Based on the robust scaling method and start-up procedures of a typical natural circulation BWR, the simulation strategies for the transient with and without void reactivity feedback is developed. Three different heat-up rates are applied to the transient simulations to study characteristics of the stability during the start-up. Reducing heat-up rate leads to increase in the period of flashing-induced density wave oscillation and decrease in the system pressurization rate. However, reducing the heat-up rate is unable to completely prevent flashing-induced oscillations. Five characteristic regions of stability are discovered at low pressure conditions. They are stable single-phase, flashing near the separator, intermittent oscillation, sinusoidal oscillation and low subcooling stable regions. Stability maps were acquired for system pressures ranging 100 kPa to 400 kPa. According to experimental investigation, the flow becomes stable below a certain heat flux regardless of the inlet subcooling at the core and system pressure. At higher heat flux, unstable phenomena were indentified within a certain range of inlet subcooling. The unstable region diminishes as the system pressure increases. In natural circulation BWRs, the significant gravitational pressure drop over the tall chimney section induces a Type-I instability. The Type-I instability becomes especially important during low power and pressure conditions during reactor start-up. Under these circumstances the effect of pressure variations on the saturation enthalpy becomes significant. An experimental study shows that the flashing phenomenon in the adiabatic chimney section is dominant during the start-up of a natural circulation BWR. Since flashing occurs outside the core, nuclear feedback effects on the stability are small. Furthermore, the thermal-hydraulic oscillation period is much longer than power fluctuation period caused by void reactivity feedback. In the natural circulation system increasing the inlet restriction reduces the natural circulation flow rate, shifting the unstable region to higher inlet subcooling.

  7. A Mechanistic Study of Nucleate Boiling Heat Transfer Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Dhir, V. K.; Hasan, M. M.

    2000-01-01

    Experimental studies of growth and detachment processes of a single bubble and multiple bubbles formed on a heated surface have been conducted in the parabola flights of KC-135 aircraft. Distilled water and PF5060 were used as the test liquids. A micro-fabricated test surface was designed and built. Artificial cavities of diameters 10 microns, 7 microns and 4 microns were made on a thin polished Silicon wafer that was electrically heated by a number of small heating elements on the back side in order to control the surface superheat. Bubble growth period, bubble size and shape from nucleation to departure were measured under subcooled and saturation conditions. Significantly larger bubble departure diameters and bubble growth periods than those at earth normal gravity were observed. Bubble departure diameters as large as 20 mm for water and 6 mm for PF5060 were observed as opposed to about 3 mm for water and less than 1 mm for PF5060 at earth normal gravity respectively. It is found that the bubble departure diameter can be approximately related to the gravity level through the relation D(sub d) proportional 1/g(exp 1/2). For water,the effect of wall superheat and liquid subcooling on bubble departure diameter is found to be small.The growth periods are found to be very sensitive to liquid subcooling at a given wall superheat. However,the preliminary results of single bubble dynamics using PF5060 showed that the departure diameter increases when wall superheat is elevated at the same gravity and subcooling. Growth period of single bubbles in water has been found to vary as t(sub g) proportional g(exp -.93). For water, when the magnitude of horizontal gravitational components was comparable to that of gravity normal to the surface, single bubbles slid along the heater surface and departed with smaller diameter at the same gravity level in the direction normal to the surface. For PF5060, even a very small horizontal gravitational component caused the sliding of bubble along the surface. The numerical simulation has been carried out by solving under the condition of axisymmetry, the mass, momentum, and energy equations for the vapor and the liquid phases. In the model the contribution of micro-layer has been included and instantaneous shape of the evolving vapor-liquid interface is determined from the analysis. Consistent with the experimental results, it is found that effect of reduced gravity is to stretch the growth period and bubble diameter It is found that effect of reduced gravity is to stretch the growth period and bubble diameter at departure. The numerical simulations are in good agreement with the experimental data for both the departure diameters and the growth periods. In the study on dynamics of multiple bubbles, horizontal merger of 2,3 4,and 5 bubbles was observed. It is found that after merger of 2 and 3 bubbles the equivalent diameter of the detached bubble is smaller than that of a single bubble departing at the same gravity level. During and after bubble merger, liquid still fills the space between the vapor stems so as to form mushroom type bubbles. The experimental and numerical studies conducted so far have brought us a step closer to prediction of nucleate boiling heat fluxes under low gravity conditions. Preparations for a space flight are continuing.

  8. Hydrothermal Liquefaction of Biomass

    SciTech Connect

    Elliott, Douglas C.

    2010-12-10

    Hydrothermal liquefaction technology is describes in its relationship to fast pyrolysis of biomass. The scope of work at PNNL is discussed and some intial results are presented. HydroThermal Liquefaction (HTL), called high-pressure liquefaction in earlier years, is an alternative process for conversion of biomass into liquid products. Some experts consider it to be pyrolysis in solvent phase. It is typically performed at about 350 C and 200 atm pressure such that the water carrier for biomass slurry is maintained in a liquid phase, i.e. below super-critical conditions. In some applications catalysts and/or reducing gases have been added to the system with the expectation of producing higher yields of higher quality products. Slurry agents ('carriers') evaluated have included water, various hydrocarbon oils and recycled bio-oil. High-pressure pumping of biomass slurry has been a major limitation in the process development. Process research in this field faded away in the 1990s except for the HydroThermal Upgrading (HTU) effort in the Netherlands, but has new resurgence with other renewable fuels in light of the increased oil prices and climate change concerns. Research restarted at Pacific Northwest National Laboratory (PNNL) in 2007 with a project, 'HydroThermal Liquefaction of Agricultural and Biorefinery Residues' with partners Archer-Daniels-Midland Company and ConocoPhillips. Through bench-scale experimentation in a continuous-flow system this project investigated the bio-oil yield and quality that could be achieved from a range of biomass feedstocks and derivatives. The project was completed earlier this year with the issuance of the final report. HydroThermal Liquefaction research continues within the National Advanced Biofuels Consortium with the effort focused at PNNL. The bench-scale reactor is being used for conversion of lignocellulosic biomass including pine forest residue and corn stover. A complementary project is an international collaboration with Canada to investigate kelp (seaweed) as a biomass feedstock. The collaborative project includes process testing of the kelp in HydroThermal Liquefaction in the bench-scale unit at PNNL. HydroThermal Liquefaction at PNNL is performed in the hydrothermal processing bench-scale reactor system. Slurries of biomass are prepared in the laboratory from whole ground biomass materials. Both wet processing and dry processing mills can be used, but the wet milling to final slurry is accomplished in a stirred ball mill filled with angle-cut stainless steel shot. The PNNL HTL system, as shown in the figure, is a continuous-flow system including a 1-litre stirred tank preheater/reactor, which can be connected to a 1-litre tubular reactor. The product is filtered at high-pressure to remove mineral precipitate before it is collected in the two high-pressure collectors, which allow the liquid products to be collected batchwise and recovered alternately from the process flow. The filter can be intermittently back-flushed as needed during the run to maintain operation. By-product gas is vented out the wet test meter for volume measurement and samples are collected for gas chromatography compositional analysis. The bio-oil product is analyzed for elemental content in order to calculate mass and elemental balances around the experiments. Detailed chemical analysis is performed by gas chromatography-mass spectrometry and 13-C nuclear magnetic resonance is used to evaluate functional group types in the bio-oil. Sufficient product is produced to allow subsequent catalytic hydroprocessing to produce liquid hydrocarbon fuels. The product bio-oil from hydrothermal liquefaction is typically a more viscous product compared to fast pyrolysis bio-oil. There are several reasons for this difference. The HTL bio-oil contains a lower level of oxygen because of more extensive secondary reaction of the pyrolysis products. There are less amounts of the many light oxygenates derived from the carbohydrate structures as they have been further reacted to phenolic Aldol condensation products. The bio-oil is more hydrophobic because of the lower oxygen content and resulting lower polarity and therefore has a lower amount of dissolved water. Without the light oxygenates acting as solvents along with the water, the bio-oil product is much more viscous. Related results are that the bio-oil is less dense and has a higher energy content. These differences in properties led to the earlier held belief that the HTL bio-oils could be upgraded by catalytic hydroprocessing in a manner more similar to simple petroleum hydrotreating. Some initial results from the HydroThermal Liquefaction of kelp are shown in Table 1. The experiments were performed with kelp slurries of 5-13 wt.% dry solids in water. Oil yields from kelp are low at 24% on ash-free basis but up to 41% calculated on a carbon basis. The bulk of the rest of the carbon ends up dissolved in the water stream.

  9. On the theory of the conversion of metallic mixed phases. 5: Fluctuations and nucleation in sub-cooled phases

    NASA Technical Reports Server (NTRS)

    Borelius, G.

    1988-01-01

    A comparison is made between fluctuation-theoretical calculations and empirical results. Concentration fluctuations and the resulting separation, and the distribution function of the reversible fluctuations are approximately calculated. The relation of this distribution to the concentration-dependence of the free energy is discussed. Possible effects of fluctuations are discussed, and other attempts to explain the sub-cooling are described.

  10. Experimental studies of adiabatic flow boiling in fractal-like branching microchannels

    SciTech Connect

    Daniels, Brian J.; Liburdy, James A.; Pence, Deborah V.

    2011-01-15

    Experimental results of adiabatic boiling of water flowing through a fractal-like branching microchannel network are presented and compared to numerical model simulations. The goal is to assess the ability of current pressure loss models applied to a bifurcating flow geometry. The fractal-like branching channel network is based on channel length and width ratios between adjacent branching levels of 2{sup -1/2}. There are four branching sections for a total flow length of 18 mm, a channel height of 150 {mu}m and a terminal channel width of 100 {mu}m. The channels were Deep Reactive Ion Etched (DRIE) into a silicon disk. A Pyrex disk was anodically bonded to the silicon to form the channel top to allow visualization of the flow within the channels. The flow rates ranged from 100 to 225 g/min and the inlet subcooling levels varied from 0.5 to 6 C. Pressure drop along the flow network and time averaged void fraction in each branching level were measured for each of the test conditions. The measured pressure drop ranged from 20 to 90 kPa, and the measured void fraction ranged from 0.3 to 0.9. The measured pressure drop results agree well with separated flow model predictions accounting for the varying flow geometry. The measured void fraction results followed the same trends as the model; however, the scatter in the experimental results is rather large. (author)

  11. Cryogenic Boil-Off Reduction System

    NASA Astrophysics Data System (ADS)

    Plachta, David W.; Guzik, Monica C.

    2014-03-01

    A computational model of the cryogenic boil-off reduction system being developed by NASA as part of the Cryogenic Propellant Storage and Transfer technology maturation project has been applied to a range of propellant storage tanks sizes for high-performing in-space cryogenic propulsion applications. This effort focuses on the scaling of multi-layer insulation (MLI), cryocoolers, broad area cooling shields, radiators, solar arrays, and tanks for liquid hydrogen propellant storage tanks ranging from 2 to 10 m in diameter. Component scaling equations were incorporated into the Cryogenic Analysis Tool, a spreadsheet-based tool used to perform system-level parametric studies. The primary addition to the evolution of this updated tool is the integration of a scaling method for reverse turbo-Brayton cycle cryocoolers, as well as the development and inclusion of Self-Supporting Multi-Layer Insulation. Mass, power, and sizing relationships are traded parametrically to establish the appropriate loiter period beyond which this boil-off reduction system application reduces mass. The projected benefit compares passive thermal control to active thermal control, where active thermal control is evaluated for reduced boil-off with a 90 K shield, zero boil-off with a single heat interception stage at the tank wall, and zero boil-off with a second interception stage at a 90 K shield. Parametric studies show a benefit over passive storage at loiter durations under one month, in addition to showing a benefit for two-stage zero boil-off in terms of reducing power and mass as compared to single stage zero boil-off. Furthermore, active cooling reduces the effect of varied multi-layer insulation performance, which, historically, has been shown to be significant.

  12. Liquid crystal thermography in boiling heat transfer

    SciTech Connect

    Klausner, J.F.; Mei, R.; Chen, W.C.

    1995-12-31

    The utilization of liquid crystal thermography to study heterogeneous boiling phenomena has gained popularity in recent years. In order not to disturb the nucleation process, which occurs in the microstructure of the heating surface, the crystals are applied to the backside of a thin heater. This work critically examines the ability of liquid crystal thermography to quantitatively capture the thermal field on the boiling surface. The thermal field identified experimentally through liquid crystal thermography is compared against that computed in the vicinity of a growing vapor bubble using a simulation which considers the simultaneous heat transfer between three phases: the solid heater, the liquid microlayer, and the growing vapor bubble. The temperature history beneath a growing vapor bubble elucidates the high frequency response required to capture the transient thermal fields commonly encountered in boiling experiments. Examination of the governing equations and numerical results reveal that due to the heater thermal inertia, the temperature variation on the bottom of the heater is significantly different than that on the boiling surface. In addition, the crystals themselves have a finite spatial resolution and frequency response which filter out much of the microscale phenomenon associated with boiling heat transfer. Analysis of existing pool and flow boiling liquid crystal thermographs indicate that the typical spacial resolution is on the order of 0.25 mm and the response time is on the order of 5 ms which are insufficient to resolve the fine spacial and temporal details of the heating surface thermal field. Thus the data obtained from liquid crystal thermography applied to boiling heat transfer must be cautiously interpreted.

  13. Cody hydrothermal system

    SciTech Connect

    Heasler, H.P.

    1982-01-01

    The hot springs of Colter's Hell are the surface manifestations of a much larger hydothermal system. That system has been studied to define its extent, maximum temperature, and mechanism of operation. The study area covers 2700 km/sup 2/ (1040 mi/sup 2/) in northwest Wyoming. Research and field work included locating and sampling the hot springs, geologic mapping, thermal logging of available wells, measuring thermal conductivities, analyzing over 200 oil and gas well bottom-hole temperatures, and compiling and analyzing hydrologic data. These data were used to generate a model for the hydrothermal system.

  14. Enceladus: Starting Hydrothermal Activity

    NASA Technical Reports Server (NTRS)

    Matson, D. L.; Castillo-Rogez, J. C.; Johnson, T. V.; Lunine, J. I.; Davies, A. G.

    2011-01-01

    We describe a process for starting the hydrothermal activity in Enceladus' South Polar Region. The process takes advantage of fissures that reach the water table, about 1 kilometer below the surface. Filling these fissures with fresh ocean water initiates a flow of water up from an ocean that can be self-sustaining. In this hypothesis the heat to sustain the thermal anomalies and the plumes comes from a slightly warm ocean at depth. The heat is brought to the surface by water that circulates up, through the crust and then returns to the ocean.

  15. Flow boiling heat transfer of R134a, R236fa and R245fa in a horizontal 1.030 mm circular channel

    SciTech Connect

    Ong, Chin L.; Thome, John R.

    2009-04-15

    This research focuses on acquiring accurate flow boiling heat transfer data and flow pattern visualization for three refrigerants, R134a, R236fa and R245fa in a 1.030 mm channel. We investigate trends in the data, and their possible mechanisms, for mass fluxes from 200 to 1600 kg/m{sup 2}s, heat fluxes from 2.3 kW/m{sup 2} to 250 kW/m{sup 2} at T{sub sat} = 31 C and {delta}T{sub sub} from 2 to 9 K. The local saturated flow boiling heat transfer coefficients display a heat flux and a mass flux dependency but no residual subcooling influence. The changes in heat transfer trends correspond well with flow regime transitions. These were segregated into the isolated bubble (IB) regime, the coalescing bubble (CB) regime, and the annular (A) regime for the three fluids. The importance of nucleate boiling and forced convection in these small channels is still relatively unclear and requires further research. (author)

  16. Origin of tonalites from the Boil Mountain ophiolitic complex, west-central Maine

    SciTech Connect

    Chow, J.S. . Geology Dept.)

    1993-03-01

    The Boil Mountain ophiolitic complex, west-central Maine, marks the suture between the Boundary Mountain and Gander terranes that became amalgamated in the late Cambrian during a pre-Taconic collisional event known as the Penobscottian orogeny. This even formed a composite terrane that is believed to have collided with the proto-North American margin during the Ordovician Taconic orogeny. The ophiolite is unusual in that there is no associated tectonized ultramafic section; there is a lack of a sheeted dike sequence; and an intrusive tonalite layer comprises a significant volume of the complex. Preliminary major and trace element geochemical analysis of the tonalites indicates that this unit is derived by partial melting of the associated mafic volcanics. This melting may have been induced by stopping water-rich hydrothermally altered basalts into subcrustal magma chambers. The association of arc-like volcanics and plutonics of the Boil Mountain ophiolite with the adjacent Hurricane melange suggests that the Boil Mountain may be a fragment of a forearc supra-subduction zone complex. Similar interpretations have been made recently for the Late Proterozoic Bou Azzer ophiolite in Morocco and the Coast Range ophiolite.

  17. Performance Assessment of 239 Series Helium Sub-Cooling Heat Exchangers for the Large Hadron Collider

    NASA Astrophysics Data System (ADS)

    Gilbert, N.; Roussel, P.; Riddone, G.; Moracchioli, R.; Tavian, L.

    2006-04-01

    Helium sub-cooling heat exchangers of the counter-flow type are used to minimize the vapor fraction produced in the final expansion of the 1.9 K distributed cooling loops used for cooling the superconducting magnets of the Large Hadron Collider (LHC). These components are of compact design, featuring low-pressure drop and handling very low pressure vapor at low temperature. Following a qualification phase of prototypes, a contract has been placed in European industry for the supply of 239 heat exchanger units. Different levels of extracted heat load require three different variants of heat exchangers. This paper will describe the manufacturing phase with emphasis on the main difficulties encountered to keep the production quality after a brief recall of the prototype phase. Finally, the acceptance tests performed at room temperature and at the nominal cryogenic condition at the factory and at CEA-Grenoble will be presented.

  18. Some factors affecting the metering of subcooled water with a choked venturi

    SciTech Connect

    Fincke, J.R.; Collins, D.R.

    1981-01-01

    A series of experiments was performed to characterize the subcooled choking process in a convergent-divergent nozzle with a constant-area throat. The experiments were conducted in a low-pressure flow loop capable of a maximum water flow rate of 5.5 L/s with a pressure head of 300 kPa. The pressure and temperature upstream of the nozzle in the flow loop were adjusted between 90 and 300 kPa and 53 and 96/sup 0/C, respectively. The variables measured in this study of critical flow phenomena were the flow rate, upstream pressure and temperature, and the axial wall pressure profiles in the nozzle. Critical mass flow rate data were acquired along five isotherms as a function of stagnation pressure. Factors affecting metering performance are examined.

  19. Enhancements of Nucleate Boiling Under Microgravity Conditions

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.; Yang, W. J.

    2000-01-01

    This paper presents two means for enhancing nucleate boiling and critical heat flux under microgravity conditions: using micro-configured metal-graphite composites as the boiling surface and dilute aqueous solutions of long-chain alcohols as the working fluid. In the former, thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix plays an important role in bubble detachment. Thus boiling-heat transfer performance does not deteriorate in a reduced-gravity environment. In the latter cases, the surface tension-temperature gradient of the long-chain alcohol solutions turns positive as the temperature exceeds a certain value. Consequently, the Marangoni effect does not impede, but rather aids in bubble departure from the heating surface. This feature is most favorable in microgravity. As a result, the bubble size of departure is substantially reduced at higher frequencies. Based on the existing experimental data, and a two-tier theoretical model, correlation formulas are derived for nucleate boiling on the copper-graphite and aluminum-graphite composite surfaces, in both the isolated and coalesced bubble regimes. In addition, performance equations for nucleate boiling and critical heat flux in dilute aqueous solutions of long-chain alcohols are obtained.

  20. Thermodynamic Vent System Performance Testing with Subcooled Liquid Methane and Gaseous Helium Pressurant

    NASA Technical Reports Server (NTRS)

    Flachbart, R. H.; Hastings, L. J.; Hedayat, A.; Nelson, S. L.; Tucker, S. P.

    2007-01-01

    Due to its high specific impulse and favorable thermal properties for storage, liquid methane (LCH4) is being considered as a candidate propellant for exploration architectures. In order to gain an -understanding of any unique considerations involving micro-gravity pressure control with LCH4, testing was conducted at the Marshall Space Flight Center using the Multipurpose Hydrogen Test Bed (MHTB) to evaluate the performance of a spray-bar thermodynamic vent system (TVS) with subcooled LCH4 and gaseous helium (GHe) pressurant. Thirteen days of testing were performed in November 2006, with total tank heat leak conditions of about 715 W and 420 W at a fill level of approximately 90%. The TVS system was used to subcool the LCH4 to a liquid saturation pressure of approximately 55.2 kPa before the tank was pressurized with GHe to a total pressure of 165.5 kPa. A total of 23 TVS cycles were completed. The TVS successfully controlled the ullage pressure within a prescribed control band but did not maintain a stable liquid saturation pressure. This was likely. due to a TVS design not optimized for this particular propellant and test conditions, and possibly due to a large artificially induced heat input directly into the liquid. The capability to reduce liquid saturation pressure as well as maintain it within a prescribed control band, demonstrated that the TVS could be used to seek and maintain a desired liquid inlet temperature for an engine (at a cost of propellant lost through the TVS vent). One special test was conducted at the conclusion of the planned test activities. Reduction of the tank ullage pressure by opening the Joule-Thomson valve (JT) without operating the pump was attempted. The JT remained open for over 9300 seconds, resulting in an ullage pressure reduction of 30 kPa. The special test demonstrated the feasibility of using the JT valve for limited ullage pressure reduction in the event of a pump failure.

  1. Characteristics of hydrothermal eruptions, with examples from New Zealand and elsewhere

    NASA Astrophysics Data System (ADS)

    Browne, P. R. L.; Lawless, J. V.

    2001-02-01

    Hydrothermal eruptions have occurred in many hot water geothermal fields. This paper concentrates on examples from New Zealand but also mentions others elsewhere, which demonstrate points of particular interest. Numerous small eruptions (maximum focal depths of about 90 m) have occurred in historic times (past 150 years) at Wairakei/Tauhara, Rotorua, Tikitere, Ngatamariki, Mokai and Waimangu. The presence of breccia deposits shows that much larger (with estimated maximum focal depths of about 450 m), prehistoric hydrothermal eruptions have also occurred at Kawerau, Wairakei, Tikitere, Orakeikorako, Te Kopia, Rotokawa and Waiotapu. One of the largest known hydrothermal eruptions in New Zealand took place at Rotokawa 6060±60 years ago; this produced a deposit that extended over an area with a diameter of 4 km, and has a maximum thickness of 11 m. Deposits from hydrothermal eruptions are typically very poorly sorted, matrix-supported, and may contain hydrothermally altered clasts that derive from within the geothermal reservoir. Their lithologies and alteration mineralogies are useful guides to subsurface conditions. Hydrothermal eruptions do not require any direct input of either mass or energy derived directly from a magma and, thus, differ from both phreatic and phreatomagmatic eruptions. Many hydrothermal eruptions in a hot water field start very close to the ground surface and result from the rapid formation of steam due to a sudden pressure reduction. This steam provides the energy necessary to brecciate, lift and eject fragments of the host rocks as a flashing front descends and water nearby in the reservoir boils. A rock brecciation zone accompanies this front, and both precede the descent of the eruption surface. A hydrothermal eruption continues until the steam is produced too slowly to lift the brecciated rocks. There is no genetic difference between the small eruptions induced by exploitation and those which occur as a geothermal system evolves naturally and whose effects may penetrate to much greater depths. Hydrothermal eruptions do not need the presence of either field-wide cap rocks or pressures within a reservoir that exceed that provided by a hydrostatic column of water very close to its boiling temperature.

  2. Boiling on Microconfigured Composite Surfaces Enhanced

    NASA Technical Reports Server (NTRS)

    Chao, David F.

    2000-01-01

    Boiling heat transfer is one of the key technologies for the two-phase active thermal-control system used on space platforms, as well as for the dynamic power systems aboard the International Space Station. Because it is an effective heat transfer mode, boiling is integral to many space applications, such as heat exchangers and other cooling devices. Nucleate boiling near the critical heat flux (CHF) can transport very large thermal loads with a much smaller device and much lower pumping power than for single-phase heat exchangers. However, boiling performance sharply deteriorates in a reduced-gravity environment, and operation in the CHF regime is somewhat perilous because of the risk of burnout to the device surface. New materials called microconfigured metal-graphite composites can enhance boiling. The photomicrograph shows the microconfiguration (x3000) of the copper-graphite (Cu-Gr) surface as viewed by scanning electronic microscope. The graphite fiber tips appear as plateaus with rugged surfaces embedded in the copper matrix. It has been experimentally demonstrated that this type of material manifests excellent boiling heat transfer performance characteristics and an increased CHF. Nonisothermal surfaces were less sensitive to variations of wall superheat in the CHF regime. Because of the great difference in conductivity between the copper base and the graphite fiber, the composite surfaces have a nonisothermal surface characteristic and, therefore, will have a much larger "safe" operating region in the CHF regime. In addition, the thermocapillary forces induced by the temperature differences between the fiber tips and the metal matrix play an important role in bubble detachment, and may not be adversely affected in a reduced-gravity environment. All these factors indicate that microconfigured composites may improve the reliability and economy (dominant factors in all space applications) of various thermal components found on spacecraft during future missions.

  3. CONTINUOUS ANALYZER UTILIZING BOILING POINT DETERMINATION

    DOEpatents

    Pappas, W.S.

    1963-03-19

    A device is designed for continuously determining the boiling point of a mixture of liquids. The device comprises a distillation chamber for boiling a liquid; outlet conduit means for maintaining the liquid contents of said chamber at a constant level; a reflux condenser mounted above said distillation chamber; means for continuously introducing an incoming liquid sample into said reflux condenser and into intimate contact with vapors refluxing within said condenser; and means for measuring the temperature of the liquid flowing through said distillation chamber. (AEC)

  4. The boiling point of stratospheric aerosols.

    NASA Technical Reports Server (NTRS)

    Rosen, J. M.

    1971-01-01

    A photoelectric particle counter was used for the measurement of aerosol boiling points. The operational principle involves raising the temperature of the aerosol by vigorously heating a portion of the intake tube. At or above the boiling point, the particles disintegrate rather quickly, and a noticeable effect on the size distribution and concentration is observed. Stratospheric aerosols appear to have the same volatility as a solution of 75% sulfuric acid. Chemical analysis of the aerosols indicates that there are other substances present, but that the sulfate radical is apparently the major constituent.

  5. Wall temperature patterns in nucleate boiling

    NASA Astrophysics Data System (ADS)

    Kenning, D. B. R.

    Temperature patterns on the back of a thin stainless steel heated plate during pool nucleate boiling of water are measured with thermocromic liquid crystal. It is shown that spatial variations which are large fractions of the mean wall superheat are to be expected in many experimental and industrial applications of boiling. They can cause errors on the measurement of the mean wall superheat by some conventional methods. Established mechanistic models which assume uniformity of wall superheat cannot represent correctly the processes controlling the density and intermittent activity of the bubble nucleation sites on walls of finite thermal conductivity. The essential features of a realistic model are described.

  6. Proteomic Investigation of Protein Profile Changes and Amino Acid Residue Level Modification in Cooked Lamb Meat: The Effect of Boiling.

    PubMed

    Yu, Tzer-Yang; Morton, James D; Clerens, Stefan; Dyer, Jolon M

    2015-10-21

    Hydrothermal treatment (heating in water) is a common method of general food processing and preparation. For red-meat-based foods, boiling is common; however, how the molecular level effects of this treatment correlate to the overall food properties is not yet well-understood. The effects of differing boiling times on lamb meat and the resultant cooking water were here examined through proteomic evaluation. The longer boiling time was found to result in increased protein aggregation involving particularly proteins such as glyceraldehyde-3-phosphate dehydrogenase, as well as truncation in proteins such as in α-actinin-2. Heat-induced protein backbone cleavage was observed adjacent to aspartic acid and asparagine residues. Side-chain modifications of amino acid residues resulting from the heating, including oxidation of phenylalanine and formation of carboxyethyllysine, were characterized in the cooked samples. Actin and myoglobin bands from the cooked meat per se remained visible on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, even after significant cooking time. These proteins were also found to be the major source of observed heat-induced modifications. This study provides new insights into molecular-level modifications occurring in lamb meat proteins during boiling and a protein chemistry basis for better understanding the effect of this common treatment on the nutritional and functional properties of red-meat-based foods. PMID:26381020

  7. An Investigation of Graduate Scientists' Understandings of Evaporation and Boiling.

    ERIC Educational Resources Information Center

    Goodwin, Alan; Orlik, Yuri

    2000-01-01

    Uses a video presentation of six situations relating to the evaporation and boiling of liquids and the escape of dissolved gases from solution and investigates graduate scientists' understanding of the concepts of boiling and evaporation. (Author/YDS)

  8. Hydrothermal processes at seafloor spreading centers,

    SciTech Connect

    Sleep, N.H.

    1983-01-01

    This chapter discusses the initial entry of hydrothermal seawater into deep levels of the oceanic crust, the effectiveness of hydrothermal circulation in cooling the crust, the geometry of hydrothermal circulation, the relationship between the hydrothermal circulation and the magma chamber, the reaction of the oceanic crust with the seawater, and the identification of the hydrothermal fluid which alters a rock sample. Topics considered include the crack front, observation relevant to the crack front, the limitations of the crack front hypothesis, the observed pattern of hydrothermal alteration, the nature of the hydrothermal fluid, the physics of large scale convection, and convection through crack zones. Knowledge of hydrothermal circulation at the ridge axis is based on sampling of the hydrothermal fluid, indirect geophysical measurements of the oceanic crust, and studies of rocks which are believed to have undergone hydrothermal alteration at the ridge axis. Includes 2 drawings.

  9. Oxygen and carbon isotope ratios of hydrothermal minerals from Yellowstone drill cores

    USGS Publications Warehouse

    Sturchio, N.C.; Keith, T.E.C.; Muehlenbachs, K.

    1990-01-01

    Oxygen and carbon isotope ratios were measured for hydrothermal minerals (silica, clay and calcite) from fractures and vugs in altered rhyolite, located between 28 and 129 m below surface (in situ temperatures ranging from 81 to 199??C) in Yellowstone drill holes. The purpose of this study was to investigate the mechanism of formation of these minerals. The ??18O values of the thirty-two analyzed silica samples (quartz, chalcedony, ??-cristobalite, and ??-cristobalite) range from -7.5 to +2.8???. About one third of the silica 7samples have ??18O values that are consistent with isotopic equilibrium with present thermal waters; most of the other silica samples appear to have precipitated from water enriched in 18O (up to 4.7???) relative to present thermal water, assuming precipitation at present in situ temperatures. Available data on fluid-inclusion homogenization temperatures in hydrothermal quartz indicate that silica precipitation occurred mostly at temperatures above those measured during drilling and imply that 15O enrichments in water during silica precipitation were generally larger than those estimated from present conditions. Similarly, clay minerals (celadonite and smectite) have ??18O values higher (by 3.5 to 7.9???) than equilibrium values under present conditions. In contrast, all eight analyzed calcite samples are close to isotopic equilibrium with present thermal waters. The frequent incidence of apparent 18O enrichment in thermal water from which the hydrothermal minerals precipitated may indicate that a higher proportion of strongly 18O-enriched deep hydrothermal fluid once circulated through shallow portions of the Yellowstone system, or that a recurring transient 18O-enrichment effect occurs at shallow depths and is caused either by sudden decompressional boiling or by isotopic exchange at low water/rock ratios in new fractures. The mineralogy and apparent 18O enrichments of hydrothermal fracture-filling minerals are consistent with deposition during transient boiling or rock-water exchange (fracturing) events. ?? 1990.

  10. Electrohydrodynamic Pool Boiling in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Shaw, Benjamin D.; Stahl, S. L.

    1996-01-01

    This research is concerned with studying the effects of applied electric fields on pool boiling in a reduced-gravity environment. Experiments are conducted at the NASA Lewis 2.2 sec Drop tower using a drop rig constructed at UC Davis. In the experiments, a platinum wire is heated while immersed in saturated liquid refrigerants (FC-72 and FC-87), or water, causing vapor formation at the wire surface. Electric fields are applied between the wire surface and an outer screen electrode that surrounds the wire. Preliminary normal-gravity experiments with water have demonstrated that applied electric fields generated by the rig electronics can influence boiling characteristics. Reduced-gravity experiments will be performed in the summer of 1996. The experiments will provide fundamental data on electric field strengths required to disrupt film boiling (for various wire heat generation input rates) in reduced gravity for a cylindrical geometry. The experiments should also shed light on the roles of characteristic bubble generation times and charge relaxation times in determining the effects of electric fields on pool boiling. Normal-gravity comparison experiments will also be performed.

  11. The Plausibility of Boiling Geysers on Triton

    NASA Technical Reports Server (NTRS)

    Duxbury, N. S.; Brown, R. H.

    1995-01-01

    A mechanism is suggested and modeled whereby there may be boiling geysers on Triton. The geysers would be of nitrogen considering that Voyager detected cryovolcanic activity, that solid nitrogen conducts heat much less than water ice, and that there is internal heat on Triton.

  12. Big Bubbles in Boiling Liquids: Students' Views

    ERIC Educational Resources Information Center

    Costu, Bayram

    2008-01-01

    The aim of this study was to elicit students' conceptions about big bubbles in boiling liquids (water, ethanol and aqueous CuSO[subscript 4] solution). The study is based on twenty-four students at different ages and grades. The clinical interviews technique was conducted to solicit students' conceptions and the interviews were analyzed to…

  13. Cryogenic Boil-Off Reduction System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, David W.; Johnson, Wesley L.; Feller, Jeffery

    2014-01-01

    The Cryogenic Boil-Off Reduction System was tested with LH2 and LOX in a vacuum chamber to simulate space vacuum and the temperatures of low Earth orbit. Testing was successful and results validated the scaling study model that predicts active cooling reduces upper stage cryogenic propulsion mass for loiter periods greater than 2 weeks.

  14. Classic and Hard-Boiled Detective Fiction.

    ERIC Educational Resources Information Center

    Reilly, John M.

    Through an analysis of several stories, this paper defines the similarities and differences between classic and hard-boiled detective fiction. The characters and plots of three stories are discussed: "The Red House" by A. A. Milne; "I, The Jury" by Mickey Spillane; and "League of Frightened Men" by Rex Stout. The classic detective story is defined…

  15. The plumbing of Old Faithful Geyser revealed by hydrothermal tremor

    NASA Astrophysics Data System (ADS)

    Vandemeulebrouck, J.; Roux, P.; Cros, E.

    2013-05-01

    Faithful Geyser in Yellowstone National Park (USA) has attracted numerous scientific investigations for over two centuries to better understand its geological structure, the physics of its eruptions, and the controls of its intermittency. Using data acquired with a seismic array in 1992, we track the sources of hydrothermal tremor produced by boiling and cavitation inside the geyser. The location of seismic sources identifies a previously unknown lateral cavity at 15 m below the surface, on the SW side of the vent, and connected to the conduit. This reservoir is activated at the beginning of each geyser eruption cycle and plays a major role in the oscillatory behavior of the water level in the conduit before each eruption.

  16. A new regime of nucleate boiling in microsphere mesostructures: Jumping pool boiling

    NASA Astrophysics Data System (ADS)

    Dmitriev, A. S.; Makarov, P. G.; El Bouz, M. A.

    2015-03-01

    We have studied a new regime of nucleate boiling in distilled water on substrates representing mesostructures of monodisperse and/or polydisperse microspheres made of various materials. It is experimentally established that, under some conditions of nucleate boiling, there appear "jumping pool boiling" regimes in which bubbles do not reach the surface of underheated liquid. In addition, bubbles may capture a certain number of microspheres, lift them up to some height, and then sink together down to the vessel bottom. Alternatively, microspheres may trap a certain number of bubbles, float up toward the evaporating surface, and then (without reaching the surface) sink back to the bottom layer where the nucleate bubbling takes place. Subregimes of this boiling mechanism involving microspheres of various densities and dimensions have also been observed.

  17. Sulfur speciation in natural hydrothermal waters, Iceland

    NASA Astrophysics Data System (ADS)

    Kaasalainen, Hanna; Stefánsson, Andri

    2011-05-01

    The speciation of aqueous dissolved sulfur was determined in hydrothermal waters in Iceland. The waters sampled included hot springs, acid-sulfate pools and mud pots, sub-boiling well discharges and two-phase wells. The water temperatures ranged from 4 to 210 °C, the pH T was between 2.20 and 9.30 at the discharge temperature and the SO 4 and Cl concentrations were 0.020-52.7 and <0.01-10.0 mmol kg -1, respectively. The analyses were carried out on-site within ˜10 min of sampling using ion chromatography (IC) for sulfate (SO 42-), thiosulfate (S 2O 32-) and polythionates (S xO 62-) and titration and/or colorimetry for total dissolved sulfide (S 2-). Sulfite (SO 32-) could also be determined in a few cases using IC. Alternatively, for few samples in remote locations the sulfur oxyanions were stabilized on a resin on site following elution and analysis by IC in the laboratory. Dissolved sulfate and with few exceptions also S 2- were detected in all samples with concentrations of 0.02-52.7 mmol kg -1 and <1-4100 μmol kg -1, respectively. Thiosulfate was detected in 49 samples of the 73 analyzed with concentrations in the range of <1-394 μmol kg -1 (S-equivalents). Sulfite was detected in few samples with concentrations in the range of <1-3 μmol kg -1. Thiosulfate and SO 32- were not detected in <100 °C well waters and S 2O 32- was observed only at low concentrations (<1-8 μmol kg -1) in ˜200 °C well waters. In alkaline and neutral pH hot springs, S 2O 32- was present in significant concentrations sometimes corresponding to up to 23% of total dissolved sulfur (S TOT). In steam-heated acid-sulfate waters, S 2O 32- was not a significant sulfur species. The results demonstrate that S 2O 32- and SO 32- do not occur in the deeper parts of <150 °C hydrothermal systems and only in trace concentrations in ˜200-300 °C systems. Upon ascent to the surface and mixing with oxygenated ground and surface waters and/or dissolution of atmospheric O 2, S 2- is degassed and oxidized to SO 32- and S 2O 32- and eventually to SO 42- at pH >8. In near-neutral hydrothermal waters the oxidation of S 2- and the interaction of S 2- and S 0 resulting in the formation of S x2- are considered important. At lower pH values the reactions seemed to proceed relatively rapidly to SO 42- and the sulfur chemistry of acid-sulfate pools was dominated by SO 42-, which corresponded to >99% of S TOT. The results suggest that the aqueous speciation of sulfur in natural hydrothermal waters is dynamic and both kinetically and source-controlled and cannot be estimated from thermodynamic speciation calculations.

  18. 21 CFR 872.6710 - Boiling water sterilizer.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Boiling water sterilizer. 872.6710 Section 872.6710 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is...

  19. Cryogenic Boil-Off Reduction System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, David W.; Johnson, Wesley L.; Feller, Jeffrey R.

    2014-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration due to the high specific impulse that can be achieved using engines suitable for moving 10's to 100's of metric tons of payload mass to destinations outside of low earth orbit. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for missions with durations greater than several days. The losses can be greatly reduced by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and by the integration of self-supporting multi-layer insulation. The active thermal control technology under development is the integration of the reverse turbo- Brayton cycle cryocooler to the propellant tank through a distributed cooling network of tubes coupled to a shield in the tank insulation and to the tank wall itself. Also, the self-supporting insulation technology was utilized under the shield to obtain needed tank applied LH2 performance. These elements were recently tested at NASA Glenn Research Center in a series of three tests, two that reduced LH2 boil-off and one to eliminate LO2 boil-off. This test series was conducted in a vacuum chamber that replicated the vacuum of space and the temperatures of low Earth orbit. The test results show that LH2 boil-off was reduced 60% by the cryocooler system operating at 90K and that robust LO2 zero boil-off storage, including full tank pressure control was achieved.

  20. Evaluating the Consequences of Edifice Instability-Related Processes in Hydrothermal Ore Genesis at Composite Volcanoes

    NASA Astrophysics Data System (ADS)

    Szakacs, A.

    2009-05-01

    Composite volcanoes intrinsically evolve toward instability, which is resolved through sudden (e.g. flank/edifice failure) or gradual (e.g. volcano-basement interaction) processes. They commonly host hydrothermal systems and related ore deposits within their edifices and shallow basement. The nature and extent of the influence instability-related processes exert on these hydrothermal systems and ore genesis are as yet poorly understood. Short-term effects are basically related to sudden depressurization of the system. The key factors determining the response of the hydrothermal system are its depth and maturity, and amount of depressurization. Deep excavation will lead to evisceration of the edifice-hosted hydrothermal system, dispersion of its volatiles in the atmosphere and incorporation of solid-phase components in the resulting debris avalanche deposit (DAD). When mature, such a system may provide DAD-hosted ore deposits. The fate of the deeper, basement-hosted hydrothermal system depends on its maturity. The evolution of an immature system will be aborted as a consequence of premature depressurization-driven boiling, and no ore-grade mineralization forms. Mature systems, however, will benefit from pressure drop and induced boiling by massive deposition of pressure-sensitive ore minerals and formation of high-grade ore. Long-range effects of edifice-failure are related to increase of the meteoric input into the hydrothermal system due to the formation of a large depression and reorganization of the surface hydrologic regime. Shift from high-T vapor-dominated regime to low-T dilute hydrothermal regime is its expected outcome. The influence of gradual release of edifice instability by volcano spreading and related phenomena on the hydrothermal system has not been studied so far. Deformation induced in both edifice and basement would result in change of fluid pathways according to the shift of local stress regimes between compressional and tensional, in turn depending on a number of factors (e.g. the presence, depth and thickness of a plastically deformable layer in the basement). That would determine the actual location of ore mineral deposition. Thorough understanding of instability-related processes greatly helps in mineral exploration activities at extinct and old composite volcanoes.

  1. Microbial ecology of hydrothermal biotypes

    NASA Astrophysics Data System (ADS)

    Montero, Clemente I.; Conners, Shannon B.; Johnson, Matthew R.; Pysz, Marybeth A.; Shockley, Keith R.; Kelly, Robert M.

    2004-02-01

    Hydrothermal environments, whether terrestrial or marine, provide a window into potentially thriving ecosystems on other solar bodies. If such extraterrestrial biotopes do exist, they might be inhabited by extremophilic microorganisms, perhaps related to hyperthermophiles (optimal growth temperature > 80°C) previously characterized from geothermal sites on this planet. Study of the physiological and metabolic patterns in hyperthermophiles will shed light on microbial lifestyles consistent with putative hydrothermal niches on other planets and moons.

  2. Hydrothermal monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States

    USGS Publications Warehouse

    Ingebritsen, S.E.; Randolph-Flagg, N. G.; Gelwick, K.D.; Lundstrom, E.A.; Crankshaw, I.M.; Murveit, A.M.; Schmidt, M.E.; Bergfeld, D.; Spicer, K.R.; Tucker, D.S.; Mariner, R.H.; Evans, William C.

    2014-01-01

    Ongoing (1996–present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of hydrothermal anomalies, including elevated temperatures, elevated major ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the US Geological Survey to begin a systematic hydrothermal-monitoring effort encompassing 25 sites and 10 of the highest-risk volcanoes in the Cascade volcanic arc, from Mount Baker near the Canadian border to Lassen Peak in northern California. A concerted effort was made to develop hourly, multiyear records of temperature and/or hydrothermal solute flux, suitable for retrospective comparison with other continuous geophysical monitoring data. Targets included summit fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and/or anomalous fluxes of magmatic CO2 or heat. As of 2009–2012, summit fumarole temperatures in the Cascade Range were generally near or below the local pure water boiling point; the maximum observed superheat was 3 during periods of hourly record. Hydrothermal responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multidecadal trends indicates that whereas the hydrothermal system at Mount St. Helens is still fast-evolving in response to the 1980–present eruptive cycle, there is no clear evidence of ongoing long-term trends in hydrothermal activity at other Cascade Range volcanoes that have been active or restless during the past century (Baker, South Sister, and Lassen). Experience gained during the Cascade Range hydrothermal-monitoring experiment informs ongoing efforts to capture entire unrest cycles at more active but generally less accessible volcanoes such as those in the Aleutian arc.

  3. Experimental study of condensate subcooling with the use of a model of an air-cooled condenser

    NASA Astrophysics Data System (ADS)

    Sukhanov, V. A.; Bezukhov, A. P.; Bogov, I. A.; Dontsov, N. Y.; Volkovitsky, I. D.; Tolmachev, V. V.

    2016-01-01

    Water-supply deficit is now felt in many regions of the world. This hampers the construction of new steam-turbine and combined steam-and-gas thermal power plants. The use of dry cooling systems and, specifically, steam-turbine air-cooled condensers (ACCs) expands the choice of sites for the construction of such power plants. The significance of condensate subcooling Δ t as a parameter that negatively affects the engineering and economic performance of steam-turbine plants is thereby increased. The operation and design factors that influence the condensate subcooling in ACCs are revealed, and the research objective is, thus, formulated properly. The indicated research was conducted through physical modeling with the use of the Steam-Turbine Air-Cooled Condenser Unit specialized, multipurpose, laboratory bench. The design and the combined schematic and measurement diagram of this test bench are discussed. The experimental results are presented in the form of graphic dependences of the condensate subcooling value on cooling ratio m and relative weight content ɛ' of air in steam at the ACC inlet at different temperatures of cooling air t ca ' . The typical ranges of condensate subcooling variation (4 ≤ Δ t ≤ 6°C, 2 ≤ Δ t ≤ 4°C, and 0 ≤ Δ t ≤ 2°C) are identified based on the results of analysis of the attained Δ t levels in the ACC and numerous Δ t reduction estimates. The corresponding ranges of cooling ratio variation at different temperatures of cooling air at the ACC inlet are specified. The guidelines for choosing the adjusted ranges of cooling ratio variation with account of the results of experimental studies of the dependences of the absolute pressure of the steam-air mixture in the top header of the ACC and the heat flux density on the cooling ratio at different temperatures of cooling air at the ACC inlet are given.

  4. Hydrothermal Growth of Polyscale Crystals

    NASA Astrophysics Data System (ADS)

    Byrappa, Kullaiah

    In this chapter, the importance of the hydrothermal technique for growth of polyscale crystals is discussed with reference to its efficiency in synthesizing high-quality crystals of various sizes for modern technological applications. The historical development of the hydrothermal technique is briefly discussed, to show its evolution over time. Also some of the important types of apparatus used in routine hydrothermal research, including the continuous production of nanosize crystals, are discussed. The latest trends in the hydrothermal growth of crystals, such as thermodynamic modeling and understanding of the solution chemistry, are elucidated with appropriate examples. The growth of some selected bulk, fine, and nanosized crystals of current technological significance, such as quartz, aluminum and gallium berlinites, calcite, gemstones, rare-earth vanadates, electroceramic titanates, and carbon polymorphs, is discussed in detail. Future trends in the hydrothermal technique, required to meet the challenges of fast-growing demand for materials in various technological fields, are described. At the end of this chapter, an Appendix 18.A containing a more or less complete list of the characteristic families of crystals synthesized by the hydrothermal technique is given with the solvent and pressure-temperature (PT) conditions used in their synthesis.

  5. First in-situ sensing of volcanic gas plume composition at Boiling Lake (Dominica, West Indies)

    NASA Astrophysics Data System (ADS)

    Di Napoli, R.; Aiuppa, A.; Allard, P.

    2012-12-01

    Dominica, a small Caribbean island between Martinique (to the South) and Guadeloupe (to the North), is, because of the high number of potentially active volcanic centres, one of the most susceptible sites to volcanic risk in the Lesser Antilles arc. Seven major volcanic centres, active during the last 10ka, are considered likely to erupt again, and one of these is the Valley of Desolation volcanic complex. This is an area of 0.5 km2, located in on SW Dominica, where a number of small explosion craters, hot springs, bubbling pools and fumaroles testify for vigorous and persistent hydrothermal activity. Two main phreatic explosions have been documented in historical time (1880 and 1997), and the most likely centre of future activity is the Boiling Lake, a nearby high-T volcanic crater lake produced by an undated phreatic/phreato-magmatic explosion. Hot (80 to 90C) and acidic (4-6) waters normally characterize the steady-state activity of the lake, whereby which vigorous gas upwelling in the lake's centre feeds a persistent steaming plume. Stability of the Boiling Lake has occasionally been interrupted in the past (since 1876) by crises, the most recent in 2004, involving rapid draining of the lake and changes in water temperature and pH, likely as a result of drastic decrease of hydrothermal fluid input into the lake. While the chemical and isotopic composition of the lake waters is well characterised, there are no compositional data available for the gas plume leaving the lake, due to inherent difficulties in direct gas sampling. Here, we present the results of the first direct measurements of the Boiling Lake's plume, performed by using the MultiGAS technique in February 2012. We acquired 0.5 Hz time-series of H2O, CO2, H2S and SO2 plume concentrations, which were seen to peak (with maximum background-corrected concentrations of 3680, 101 and 25 ppm for respectively H2O, CO2 and H2S) during phases of visible increase in lake outgassing. SO2 was virtually absent in the plume. From the concentration data, the characteristic CO2/H2S (5.20.4) and H2O/CO2 (31.46) volatile ratios in the Boiling lake's atmospheric plume were derived. This reveals similar C to S signature for Boiling lake and Valley of Desolation (for which we also obtained data using the same technique), likely indicative of common source reservoir. The Boiling lake's plume is far more H2O-rich than the Valley of Desolation gas, suggesting that a significant fraction of in-plume H2O in the former originates from re-evaporation of the lake water itself. Our data here provide a first compositional baseline for quiescent volcanic gas emissions at Boiling Lake, and may form the basis to stimulate emerging geochemical monitoring programs in the area.

  6. Experimental Investigation of Pool Boiling Heat Transfer Enhancement in Microgravity in the Presence of Electric Fields

    NASA Technical Reports Server (NTRS)

    Herman, Cila

    1999-01-01

    In boiling high heat fluxes are possible driven by relatively small temperature differences, which make its use increasingly attractive in aerospace applications. The objective of the research is to develop ways to overcome specific problems associated with boiling in the low gravity environment by substituting the buoyancy force with the electric force to enhance bubble removal from the heated surface. Previous studies indicate that in terrestrial applications nucleate boiling heat transfer can be increased by a factor of 50, as compared to values obtained for the same system without electric fields. The goal of our research is to experimentally explore the mechanisms responsible for EHD heat transfer enhancement in boiling in low gravity conditions, by visualizing the temperature distributions in the vicinity of the heated surface and around the bubble during boiling using real-time holographic interferometry (HI) combined with high-speed cinematography. In the first phase of the project the influence of the electric field on a single bubble is investigated. Pool boiling is simulated by injecting a single bubble through a nozzle into the subcooled liquid or into the thermal boundary layer developed along the flat heater surface. Since the exact location of bubble formation is known, the optical equipment can be aligned and focused accurately, which is an essential requirement for precision measurements of bubble shape, size and deformation, as well as the visualization of temperature fields by HI. The size of the bubble and the frequency of bubble departure can be controlled by suitable selection of nozzle diameter and mass flow rate of vapor. In this approach effects due to the presence of the electric field can be separated from effects caused by the temperature gradients in the thermal boundary layer. The influence of the thermal boundary layer can be investigated after activating the heater at a later stage of the research. For the visualization experiments a test cell was developed. All four vertical walls of the test cell are transparent, and they allow transillumination with laser light for visualization experiments by HI. The bottom electrode is a copper cylinder, which is electrically grounded. The copper block is heated with a resistive heater and it is equipped with 6 thermocouples that provide reference temperatures for the measurements with HI. The top electrode is a mesh electrode. Bubbles are injected with a syringe into the test cell through the bottom electrode. The working fluids presently used in the interferometric visualization experiments, water and PF 5052, satisfy requirements regarding thermophysical, optical and electrical properties. A 30kV power supply equipped with a voltmeter allows to apply the electric field to the electrodes during the experiments. The magnitude of the applied voltage can be adjusted either manually or through the LabVIEW data acquisition and control system connected to a PC. Temperatures of the heated block are recorded using type-T thermocouples, whose output is read by a data acquisition system. Images of the bubbles are recorded with 35mm photographic and 16mm high-speed cameras, scanned and analyzed using various software packages. Visualized temperature fields HI allows the visualization of temperature fields in the vicinity of bubbles during boiling in the form of fringes. Typical visualized temperature distributions around the air bubbles injected into the thermal boundary layer in PF5052 are shown. The temperature of the heated surface is 35 C. The temperature difference for a pair of fringes is approximately 0.05 C. The heat flux applied to the bottom surface is moderate, and the fringe patterns are regular. In the image a bubble penetrating the thermal boundary layer is visible. Because of the axial symmetry of the problem, simplified reconstruction techniques can be applied to recover the temperature field. The thermal plume developing above the heated surface for more intensive heating is shown. The temperature distribution in the liquid is clearly 3D, and tomographic techniques have to be applied to recover the temperature distribution in such a physical situation. A sequence of interferometric images showing the temperature distribution around the rising bubble, recorded with a high-speed camera is shown. Again, the temperature distribution is 3D, and a more complex approach to the evaluation, the tomographic reconstruction has to be taken. Measurement of the temperature distribution from the fringe pattern temperature distributions that yield important information regarding heat transfer are determined. Two algorithms that allow the quantitative evaluation of interferometric fringe patterns and the reconstruction of temperature fields during boiling have been developed at the Heat Transfer Laboratory of the Johns Hopkins University. In the first algorithm the bubble is assumed to be axially symmetrical, which significantly reduces the computational effort for quantifying the temperature distribution around the bubble. For this purpose the thermal boundary layer around the bubble is divided into equidistant concentric shells, and the refractive index is assumed to be constant in each of the shells. Since large temperature gradients are expected in the vicinity of the bubble during boiling, the deflection of the light beam cannot be neglected in boiling experiments. Since the exit angle of the light beam is known, this allows to account for the deflections and phase shifts outside the boundary layer (in the bulk fluid and in the windows of the test cell). Three dimensional temperature distributions in the vicinity of the bubble are reconstructed using tomographic techniques. In tomography, the measurement volume is sliced into 2D planes. In the present study these planes are parallel to the heated surface. The objective is to determine the values of the field parameter of interest in form of the field function in these 2D planes. The field parameter is the change of the refractive index of the liquid in the measurement volume caused by temperature changes. By superimposing data for many 2D planes recorded at the same time instant, the 3D temperature distribution in the measurement volume is recovered.

  7. Marangoni Effects on Near-Bubble Microscale Transport During Boiling of Binary Fluid Mixtures

    NASA Technical Reports Server (NTRS)

    V. Carey; Sun, C.; Carey, V. P.

    2000-01-01

    In earlier investigations, Marangoni effects were observed to be the dominant mechanism of boiling transport in 2-propanol/water mixtures under reduced gravity conditions. In this investigation we have examined the mechanisms of binary mixture boiling by exploring the transport near a single bubble generated in a binary mixture between a heated surface and cold surface. The temperature field created in the liquid around the bubble produces vaporization over the portion of its interface near the heated surface and condensation over portions of its interface near the cold surface. Experiments were conducted using different mixtures of water and 2-propanol under 1g conditions and under reduced gravity conditions aboard the KC135 aircraft. Since 2-propanol is more volatile than water, there is a lower concentration of 2-propanol near the hot surface and a higher concentration of 2-propanol near the cold plate relative to the bulk quantity. This difference in interface concentration gives rise to strong Marangoni effects that move liquid toward the hot plate in the near bubble region for 2-propanol and water mixtures. In the experiments in this study, the pressure of the test system was maintained at about 5 kPa to achieve the full spectrum of boiling behavior (nucleate boiling, critical heat flux and film boiling) at low temperature and heat flux levels. Heat transfer data and visual documentation of the bubble shape were extracted from the experimental results. In the 1-g experiments at moderate to high heat flux levels, the bubble was observed to grow into a mushroom shape with a larger top portion near the cold plate due to the buoyancy effect. The shape of the bubble was somewhat affected by the cold plate subcooling and the superheat of the heated surface. At low superheat levels for the heated surface, several active nucleation sites were observed, and the vapor stems from them merged to form a larger bubble. The generation rate of vapor is moderate in this regime and the bubble shape is cylindrical in appearance. In some instances, the bubble interface appeared to oscillate. At higher applied heat flux levels, the top of the bubble became larger, apparently to provide more condensing interface area adjacent to the cold plate. Increasing the applied heat flux ultimately led to dry-out of the heated surface, with conditions just prior to dryout corresponding to the maximum heat flux (CHF). A more stable bubble was observed when the system attained the minimum heat flux (for film boiling). In this regime, most of the surface under the bottom of the bubble was dry with nucleate boiling sometimes occuring around the contact perimeter of the bubble at heated surface. Different variations (e.g. gap between two plates, molar concentration of the liquid mixture) of the experiments were examined to determine parametric effects on the boiling process and to determine the best conditions for the KC135 reduced gravity tests. Variation of the gap was found to have a minor impact on the CHF. However, reducing the gap between the hot and cold surface was observed to significantly reduce the minimum heat flux for fixed molar concentration of 2-propanol. In the reduced gravity experiments aboard the KC135 aircraft, the bubble formed in the 6.4 mm gap was generally cylindrical or barrel shaped and it increased its extent laterally as the surface superheat increased. In reduced gravity experiments, dryout of the heated surface under the bubble was observed to occur at a lower superheated temperature than for 1g conditions. Observed features of the boiling process and heat transfer data under reduced gravity will be discussed in detail. The results of the reduced gravity experiments will also be compared to those obtained in comparable 1g experiments. In tandem with the experiments we are also developing a computational model of the transport in the liquid surrounding the bubble during the boiling process. The computational model uses a level set method to model motion of the interface. It will incorporate a macroscale treatment of the transport in the liquid gap between the surfaces and a microscale treatment of transport in the regions between the bubble interface and the solid surfaces. The features of the model will be described in detail. Future research directions suggested by the results to date will also be discussed.

  8. Thermohydrodynamics of boiling in a van der Waals fluid.

    PubMed

    Laurila, T; Carlson, A; Do-Quang, M; Ala-Nissila, T; Amberg, G

    2012-02-01

    We present a modeling approach that enables numerical simulations of a boiling Van der Waals fluid based on the diffuse interface description. A boundary condition is implemented that allows in and out flux of mass at constant external pressure. In addition, a boundary condition for controlled wetting properties of the boiling surface is also proposed. We present isothermal verification cases for each element of our modeling approach. By using these two boundary conditions we are able to numerically access a system that contains the essential physics of the boiling process at microscopic scales. Evolution of bubbles under film boiling and nucleate boiling conditions are observed by varying boiling surface wettability. We observe flow patters around the three-phase contact line where the phase change is greatest. For a hydrophilic boiling surface, a complex flow pattern consistent with vapor recoil theory is observed. PMID:22463330

  9. Anomaly Geochemical Fields in Siberian Hydrothermal Gold Deposits

    NASA Astrophysics Data System (ADS)

    Voroshilov, V.; Savinova, O.; Ananev, Yu; Abramova, R.

    2014-08-01

    The composition and internal structure of geochemical fields associated to hydrothermal gold deposits within the Siberian territory were investigated. The concentric zonal structure of ore-forming geochemical fields embracing accumulations of Au, Ag, Bi, Pb, Zn, Cu, Te, As in ore bodies and their adjacent locations, and Ni, Co, V, Cr, Mn, Ba, Ti - within the external margin of gold ore formations were determined. The thermometric properties of gas-fluid inclusions in minerals of hydrothermal gold deposits were described. The results specified not only high-mineralized but also weakly-salted fluids are involved in the formation of the deposit. The latter is subjected to both retrogressive boiling and the mechanisms of direct and reverse osmosis. In this case, ascending and descending fluids produce eddy fluxes during Earth rotation, where minerals of different composition are formed in this flow path. Produced spiral mineral-geochemical fields can be observed on satellite images as hierarchy circular pattern system. Both the analysis of anomalous geochemical field structure and satellite images make it possible to predict the ore bodies of different grades in complicated landscape geological conditions.

  10. Hydrothermal ore-forming processes in the light of studies in rock- buffered systems: II. Some general geologic applications

    USGS Publications Warehouse

    Hemley, J.J.; Hunt, J.P.

    1992-01-01

    The experimental metal solubilities for rock-buffered hydrothermal systems provide important insights into the acquisition, transport, and deposition of metals in real hydrothermal systems that produced base metal ore deposits. Water-rock reactions that determine pH, together with total chloride and changes in temperature and fluid pressure, play significant roles in controlling the solubility of metals and determining where metals are fixed to form ore deposits. Deposition of metals in hydrothermal systems occurs where changes such as cooling, pH increase due to rock alteration, boiling, or fluid mixing cause the aqueous metal concentration to exceed saturation. Metal zoning results from deposition occurring at successive saturation surfaces. Zoning is not a reflection simply of relative solubility but of the manner of intersection of transport concentration paths with those surfaces. Saturation surfaces will tend to migrate outward and inward in prograde and retrograde time, respectively, controlled by either temperature or chemical variables. -from Authors

  11. Unorthodox bubbles when boiling in cold water

    NASA Astrophysics Data System (ADS)

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling.

  12. Unorthodox bubbles when boiling in cold water.

    PubMed

    Parker, Scott; Granick, Steve

    2014-01-01

    High-speed movies are taken when bubbles grow at gold surfaces heated spotwise with a near-infrared laser beam heating water below the boiling point (60-70 °C) with heating powers spanning the range from very low to so high that water fails to rewet the surface after bubbles detach. Roughly half the bubbles are conventional: They grow symmetrically through evaporation until buoyancy lifts them away. Others have unorthodox shapes and appear to contribute disproportionately to heat transfer efficiency: mushroom cloud shapes, violently explosive bubbles, and cavitation events, probably stimulated by a combination of superheating, convection, turbulence, and surface dewetting during the initial bubble growth. Moreover, bubbles often follow one another in complex sequences, often beginning with an unorthodox bubble that stirs the water, followed by several conventional bubbles. This large dataset is analyzed and discussed with emphasis on how explosive phenomena such as cavitation induce discrepancies from classical expectations about boiling. PMID:24580324

  13. Hydrothermal pretreatment of coal

    SciTech Connect

    Ross, D.S.

    1989-12-21

    We have examined changes in Argonne Premium samples of Wyodak coal following 30 min treatment in liquid water at autogenous pressures at 150{degrees}, 250{degrees}, and 350{degrees}C. In most runs the coal was initially dried at 60{degrees}C/1 torr/20 hr. The changes were monitored by pyrolysis field ionization mass spectrometry (py-FIMS) operating at 2.5{degrees}C/min from ambient to 500{degrees}C. We recorded the volatility patterns of the coal tars evolved over that temperature range, and in all cases the tar yields were 25%--30% of the starting coal on mass basis. There was essentially no change after the 150{degrees}C treatment. Small increases in volatility were seen following the 250{degrees}C treatment, but major effects were seen in the 350{degrees} work. The tar quantity remained unchanged; however, the volatility increased so the temperature of half volatility for the as-received coal of 400{degrees}C was reduced to 340{degrees}C. Control runs with no water showed some thermal effect, but the net effect from the presence of liquid water was clearly evident. The composition was unchanged after the 150{degrees} and 250{degrees}C treatments, but the 350{degrees} treatment brought about a 30% loss of oxygen. The change corresponded to loss of the elements of water, although loss of OH'' seemed to fit the analysis data somewhat better. The water loss takes place both in the presence and in the absence of added water, but it is noteworthy that the loss in the hydrothermal runs occurs at p(H{sub 2}O) = 160 atm. We conclude that the process must involve the dehydration solely of chemically bound elements of water, the dehydration of catechol is a specific, likely candidate.

  14. Flow boiling test of GDP replacement coolants

    SciTech Connect

    Park, S.H.

    1995-08-01

    The tests were part of the CFC replacement program to identify and test alternate coolants to replace CFC-114 being used in the uranium enrichment plants at Paducah and Portsmouth. The coolants tested, C{sub 4}F{sub 10} and C{sub 4}F{sub 8}, were selected based on their compatibility with the uranium hexafluoride process gas and how well the boiling temperature and vapor pressure matched that of CFC-114. However, the heat of vaporization of both coolants is lower than that of CFC-114 requiring larger coolant mass flow than CFC-114 to remove the same amount of heat. The vapor pressure of these coolants is higher than CFC-114 within the cascade operational range, and each coolant can be used as a replacement coolant with some limitation at 3,300 hp operation. The results of the CFC-114/C{sub 4}F{sub 10} mixture tests show boiling heat transfer coefficient degraded to a minimum value with about 25% C{sub 4}F{sub 10} weight mixture in CFC-114 and the degree of degradation is about 20% from that of CFC-114 boiling heat transfer coefficient. This report consists of the final reports from Cudo Technologies, Ltd.

  15. POOL BOILING OF HIGH-FREQUENCY CONDUCTORS

    SciTech Connect

    Wright, S. E.; Konecni, S.; Ammerman, C. N.; Sims, J. R.

    2001-01-01

    This study presents development of a unique, powerful method for cooling high-frequency, AC conductors that can benefit end users of transformer windings, electrical machine windings, and magnet coils. This method of heat removal involves boiling a dielectric, fluorinert refrigerant that is in direct contact with litz wire conductors. A pool boiling test vessel is constructed, which provides for temperature control of the pool of fluorinert liquid. The test vessel is fitted with viewing ports so that the experiments are observed and studied with the aid of high-speed photography. Tests are performed on a variety of litz wire conductors. The boiling heat transfer coefficient is dependent on the conductor surface roughness. The size of the features on the conductor surface depends on the single-strand wire gage from which the conductor is constructed. All tests are performed with the conductors mounted horizontally. These tests are performed using a DC power supply. The results of these experiments will aid in the design of future cooling systems.

  16. Fundamental Boiling and RP-1 Freezing Experiments

    NASA Technical Reports Server (NTRS)

    Goode, Brian; Turner, Larry D. (Technical Monitor)

    2001-01-01

    This paper describes results from experiments performed to help understand certain aspects of the MC-1 engine prestart thermal conditioning procedure. The procedure was constrained by the fact that the engine must chill long enough to get quality LOX at the LOX pump inlet but must be short enough to prevent freezing of RP-1 in the fuel pump. A chill test of an MC-1 LOX impeller was performed in LN2 to obtain data on film boiling, transition boiling and impeller temperature histories. The transition boiling data was important to the chill time so a subsequent experiment was performed chilling simple steel plates in LOX to obtain similar data for LOX. To address the fuel freezing concern, two experiments were performed. First, fuel was frozen in a tray and its physical characteristics were observed and temperatures of the fuel were measured. The result was physical characteristics as a function of temperature. Second was an attempt to measure the frozen thickness of RP-1 on a cold wall submerged in warm RP-1 and to develop a method for calculating that thickness for other conditions.

  17. Temperatures of Mediterranean Volcanic Hydrothermal Systems Reflected by Gas Geothermometry

    NASA Astrophysics Data System (ADS)

    Fiebig, J.; Tassi, F.; D'Alessandro, W.; Vaselli, O.; Woodland, A. B.

    2011-12-01

    We have addressed the genetic relationship between H2, H2O, CO, CO2, n-alkanes and n-alkenes in volcanic-hydrothermal gases emitted from Nisyros (Greece), Vesuvio, Campi Flegrei and Pantelleria (all Italy). Methane attains chemical and isotopic equilibrium with CO2 in the associated hydrothermal systems within the single liquid phase. Calculated aquifer temperatures at depth are ~360C at Nisyros, 420-460C at Vesuvio, ~450C at Campi Flegrei and ~540C at Pantelleria. CH4-CO2 equilibrium temperatures are in agreement with propane/propene concentration ratios. Temperatures >400C are additionally confirmed by ethane/ethene ratios. In contrast to CH4-CO2, metastable equilibration of the alkane/alkene pairs takes place in the saturated water vapor phase. Overall agreement of vapor and liquid equilibration temperatures suggests that boiling in the investigated high-enthalpy hydrothermal systems is essentially isothermal. Our results imply that the chemical and isotopic CH4-CO2 geothermometer is least prone to re-equilibration reactions occurring in the vapor phase after vapor separation. Redox conditions during these re-equilibration reactions are homogeneously buffered by H2/H2O ratios of the vapor phase, which, in turn, are controlled by those of the parental liquid phase and by the degree of superimposed vapor separation. Amongst the redox pairs investigated, CO/CO2 is most prone to secondary vapor phase equilibration. Our results imply that the isotopic CH4-CO2 geothermometer has the potential to record temperatures of aquifers associated with dormant volcanoes. Alkene/alkane and H2/H2O concentration ratios should be measured along with CH4 and CO2 to prove independently whether isotopic equilibrium has been attained.

  18. Combined heat and mass transfer under different inlet subcooling modes during NH{sub 3}-H{sub 2}O falling film absorption process

    SciTech Connect

    Kang, Y.T.; Fujita, Y.; Akisawa, A.; Kashiwagi, T.

    1999-07-01

    Experiments were conducted for ammonia-water falling film absorption in a plate heat exchanger with offset strip fins. The objectives of this paper were to analyze combined heat and mass transfer during the ammonia-water absorption process under different inlet subcooling modes, and to obtain heat transfer coefficients (Nusselt number). This paper examined the effects of the inlet subcooling modes, the inlet concentration difference, liquid Reynolds number, and vapor Reynolds number on the heat transfer performance. Inlet liquid concentrations were set at 0, 5, 10 and 15% in mass of ammonia while inlet vapor concentration ranged from 64.7 to 83.6%. Experiments were conducted in three ways according to the inlet subcooling conditions, i.e., Case A (T{sub v}>T{sub 1}), Case B (T{sub v}{approximately}T{sub 1}), and Case C (T{sub v}subcooling effect. Water desorption was confirmed in the experiments, which resulted in a lower absorption performance. The heat transfer coefficient increased as the inlet subcooling increased in all cases. The effect of inlet subcooling on heat transfer performance was more significant in Case A than those in Case B and Case C. The inlet subcooling had more significant effect on the heat transfer performance than the inlet concentration difference. Nusselt number increased as liquid and vapor Reynolds numbers increased. The vapor velocity should be maximized to increase absorption performance in co-current ammonia-water absorption process.

  19. Stability monitoring for boiling water reactors

    NASA Astrophysics Data System (ADS)

    Cecenas-Falcon, Miguel

    1999-11-01

    A methodology is presented to evaluate the stability properties of Boiling Water Reactors based on a reduced order model, power measurements, and a non-linear estimation technique. For a Boiling Water Reactor, the feedback reactivity imposed by the thermal-hydraulics has an important effect in the system stability, where the dominant contribution to this feedback reactivity is provided by the void reactivity. The feedback reactivity is a function of the operating conditions of the system, and cannot be directly measured. However, power measurements are relatively easy to obtain from the nuclear instrumentation and process computer, and are used in conjunction with a reduced order model to estimate the gain of the thermal-hydraulics feedback using an Extended Kalman Filter. The reduced order model is obtained by estimating the thermal-hydraulic transfer function from the frequency-domain BWR code LAPUR, and the stability properties are evaluated based on the pair of complex conjugate eigenvalues. Because of the recursive nature of the Kalman Filter, an estimate of the decay ratio is generated every sampling time, allowing continuous estimation of the stability parameters. A test platform based on a nuclear-coupled boiling channel is developed to validate the capability of the BWR stability monitoring methodology. The thermal-hydraulics for the boiling channel is modeled and coupled with neutron kinetics to analyze the non-linear dynamics of the closed-loop system. The model uses point kinetics to study core-wide oscillations, and normalized modal kinetics are introduced to study out-of-phase oscillations. The coolant flow dynamics is dominant in the power fluctuations observed by in-core nuclear instrumentation, and additive white noise is added to the solution for the channel flow in the thermal-hydraulic model to generate noisy power time series. The operating conditions of the channel can be modified to accommodate a wide range of stability conditions. Autoregressive analysis performed with the computer-generated series agrees with the stability properties of the boiling channel and with the results of the reduced order model method. Finally, a method to separate the fundamental and first harmonic modes form LPRM readings is presented and tested with computer simulations and plant data.

  20. Boiling radial flow in fractures of varying wall porosity

    SciTech Connect

    Barnitt, Robb Allan

    2000-06-01

    The focus of this report is the coupling of conductive heat transfer and boiling convective heat transfer, with boiling flow in a rock fracture. A series of experiments observed differences in boiling regimes and behavior, and attempted to quantify a boiling convection coefficient. The experimental study involved boiling radial flow in a simulated fracture, bounded by a variety of materials. Nonporous and impermeable aluminum, highly porous and permeable Berea sandstone, and minimally porous and permeable graywacke from The Geysers geothermal field. On nonporous surfaces, the heat flux was not strongly coupled to injection rate into the fracture. However, for porous surfaces, heat flux, and associated values of excess temperature and a boiling convection coefficient exhibited variation with injection rate. Nucleation was shown to occur not upon the visible surface of porous materials, but a distance below the surface, within the matrix. The depth of boiling was a function of injection rate, thermal power supplied to the fracture, and the porosity and permeability of the rock. Although matrix boiling beyond fracture wall may apply only to a finite radius around the point of injection, higher values of heat flux and a boiling convection coefficient may be realized with boiling in a porous, rather than nonporous surface bounded fracture.

  1. Hydrothermal synthesis of ammonium illite

    USGS Publications Warehouse

    Sucha, V.; Elsass, F.; Eberl, D.D.; Kuchta, L'.; Madejova, J.; Gates, W.P.; Komadel, P.

    1998-01-01

    Synthetic gel and glass of illitic composition, natural kaolinite, and mixed-layer illite-smectite were used as starting materials for hydrothermal synthesis of ammonium illite. Ammonium illite was prepared from synthetic gel by hydrothermal treatment at 300??C. The onset of crystallization began within 3 h, and well-crystallized ammonium illite appeared at 24 h. Increasing reaction time (up to four weeks) led to many illite layers per crystal. In the presence of equivalent proportions of potassium and ammonium, the gel was transformed to illite with equimolar contents of K and NH4. In contrast, synthesis using glass under the same conditions resulted in a mixture of mixed-layer ammonium illite-smectite with large expandability and discrete illite. Hydrothermal treatments of the fine fractions of natural kaolinite and illite-smectite produced ammonium illite from kaolinite but the illite-smectite remained unchanged.

  2. A new type of diabatic flow pattern map for boiling heat transfer in microchannels

    NASA Astrophysics Data System (ADS)

    Revellin, R.; Thome, J. R.

    2007-04-01

    Flow pattern data and bubble measurements for two small diameter sight glass tubes are used to propose a new type of flow pattern map for evaporating flows in microchannels. Rather than segregating the observations into the traditional flow regimes and an adiabatic map, the new diabatic map classifies flows into three types: (i) the isolated bubble regime, where the bubble generation rate is much larger than the bubble coalescence rate and includes both bubbly and slug flows, (ii) the coalescing bubble regime, where the bubble coalescence rate is much larger than the bubble generation rate and exists up to the end of the coalescence process and (iii) the annular regime, whose extent is limited by the vapor quality at the onset of critical heat flux. This formulation is thought to be more useful for phenomenological modeling of the processes controlling boiling heat transfer and two-phase pressure drops in microchannels, and it also visually defines the feasible operating limit of microchannel heat spreaders at the critical vapor quality corresponding to critical heat flux (CHF). The database covers two refrigerants (R-134a and R-245fa) and two channel diameters (0.509 and 0.790 mm). The micro-evaporator length was varied from 20 to 70 mm, the inlet subcooling from 2 to 15 °C, the mass flux from 200 to 2000 kg m-2 s-1 and heat fluxes up to 597 kW m-2. Three different saturation temperatures were tested: 26, 30 and 35 °C.

  3. Hydrothermal alteration in research drill hole Y-3, Lower Geyser Basin, Yellowstone National Park, Wyoming

    USGS Publications Warehouse

    Bargar, Keith E.; Beeson, Melvin H.

    1985-01-01

    Y-3, a U.S. Geological Survey research diamond-drill hole in Lower Geyser Basin, Yellowstone National Park, Wyoming, reached a depth of 156.7 m. The recovered drill core consists of 42.2 m of surficial (mostly glacial) sediments and two rhyolite flows (Nez Perce Creek flow and an older, unnamed rhyolite flow) of the Central Plateau Member of the Pleistocene Plateau Rhyolite. Hydrothermal alteration is fairly extensive in most of the drill core. The surficial deposits are largely cemented by silica and zeolite minerals; and the two rhyolite flows are, in part, bleached by thermal water that deposited numerous hydrothermal minerals in cavities and fractures. Hydrothermal minerals containing sodium as a dominant cation (analcime, clinoptilolite, mordenite, Na-smectite, and aegirine) are more abundant than calcium-bearing minerals (calcite, fluorite, Ca-smectite, and pectolite) in the sedimentary section of the drill core. In the volcanic section of drill core Y-3, calcium-rich minerals (dachiardite, laumontite, yugawaralite, calcite, fluorite, Ca-smectite, pectolite, and truscottite) are predominant over sodium-bearing minerals (aegirine, mordenite, and Na-smectite). Hydrothermal minerals that contain significant amounts of potassium (alunite and lepidolite in the sediments and illitesmectite in the rhyolite flows) are found in the two drill-core intervals. Drill core y:.3 also contains hydrothermal silica minerals (opal, [3-cristobalite, chalcedony, and quartz), other clay minerals (allophane, halloysite, kaolinite, and chlorite), gypsum, pyrite, and hematite. The dominance of calcium-bearing hydrothermal minerals in the lower rhyolitic section of the y:.3 drill core appears to be due to loss of calcium, along with potassium, during adiabatic cooling of an ascending boiling water.

  4. D0 Silicon Upgrade: Vapor Pressure Thermometry System Near LN2 Subcooler

    SciTech Connect

    Kuwazaki, Andrew; /Fermilab

    1996-07-01

    Fermi National Accelerator Laboratory (Fermilab) is in the process of upgrading its detectors. Among these upgrades is the need for more transfer lines containing both liquid nitrogen and helium gas. These two fluids are used to provide the necessary operating cryogenic temperatures for the various detectors, such as the Visible Light Photon Counter (VLPC) and the solenoid inside the detector's calorimeter. With additional piping, it is important to monitor the temperatures to assure that the detectors can operate correctly. This can be done two ways. The first method is to use a Resistance Temperature Device, called a RTD, which is made using either a carbon resistor or a platinum resistor and measures the temperature based on resistance. The second method is to use a vapor-pressure thermometry system. This design will focus on the second method. A nitrogen Vapor Pressure Thermometer (VPT) system is designed to determine the temperature of the liquid nitrogen (LN{sub 2}) supply line, after exiting the LN{sub 2} subcooler, inside the D-Zero Assembly Hall. The operating temperature range is designed from 77 to 300 Kelvin with an initial charge pressure of 100 psia. A cylindrical bulb with a 0.1875-inch diameter and 0.625-inch length allows for minimum cold and warm 1/4-inch O.D. SS 304L tubing lengths, 12-inch and 18-inch respectively, and maintains a liquid level of 50% inside the bulb during cold operation. The amount of nitrogen needed to fill the cylindrical bulb approximately half full is 0.149 grams. In order to conform to the conventional cold volume and warm volume VPT systems, we need to enlarge the existing 1/2-inch x 2-inch SCH. 10 LN{sub 2} supply line over a one foot section to 1-inch x 3-inch SCH. 10 piping.

  5. Hydrothermal alteration facies within the intrusive-hosted Salave gold prospect, NW Spain

    SciTech Connect

    Harris, M.

    1985-01-01

    The Salave gold prospect occurs within an Hercynian granodioritic complex intruding Cambro-Ordovician metasediments and a heterogeneous gabbroic body. Mineralization consists mostly of disseminated and veinlet pyrite, arsenopyrite, molybdenite, stibnite, and lesser sphalerite associated with a zoned sequence of hydrothermal alteration. Gold occurs as free particles and/or intergrown with the sulfides. Mathematical appraisal of analytical data suggests that the hydrothermal alteration resulted from largely isochemical redistribution processes imposed on the mineralogy of the host granodiorite by influxes of sporadically boiling fluids rich in CO/sub 2/. Hydrothermal alteration is described in terms of a zonal sequence inward from unaltered host rock through (1) chlorite-sericite alteration-(2) propylitic to advanced propylitic alterations-(3)albitites-(4) an auriferous (greater than or equal to 1g/t Au) sericite-carbonate-albite-(+/-)quartz-sulfide cataclastic facies. The zonation corresponds to increasing carbonatization, sericitization, albitization, desilification, and destruction of the original igneous texture. Aventurine alteration is common and is thought to be the product of late stage hydrothermal oxidizing conditions. Potassic alteration in the form of K-feldspar or biotite was occasionally observed.

  6. Correlations between Archaeal Diversity and Geochemical Parameters in an Arsenic-Rich Hydrothermal System

    NASA Astrophysics Data System (ADS)

    Franks, M.; Omelon, C.; Engel, A. S.; Bennett, P.

    2009-04-01

    Characterizing microbial communities within their geochemical environment is useful for understanding microbial distribution and microbial adaptations to extreme physical and chemical conditions. The hydrothermal waters at El Tatio geyser field (ETGF) demonstrate extreme geochemical conditions, with discharge water from springs and geysers at local boiling temperature (85oC), arsenic concentrations of 0.5 mM, and inorganic carbon concentrations (DIC) as low as 0.2mM. Yet many of El Tatio's hundred plus hydrothermal features host extensive microbial mat communities. Recent work has shown correlations between the metabolic guilds of microorganisms present and variations in water chemistry. ETGF is a high-altitude hydrothermal basin with over 100 mapped hydrothermal features, located within a 30km2 area near the Chile-Bolivia border. The Na-Cl type waters have a circumneutral pH and contain abundant dissolved metals. Shallow runoff aprons extend tens of meters from some geyser features, where silica rapidly precipitates from cooling water. Thick mats, which appear microbial but consist primarily of silica, iron and arsenic mineral deposits, containing

  7. Implementation of Sub-Cooling of Cryogenic Propellants by Injection of Non-condensing Gas to the Generalized Fluid Systems Simulation Program (GFSSP)

    NASA Technical Reports Server (NTRS)

    Huggett, Daniel J.; Majumdar, Alok

    2013-01-01

    Cryogenic propellants are readily heated when used. This poses a problem for rocket engine efficiency and effective boot-strapping of the engine, as seen in the "hot" LOX (Liquid Oxygen) problem on the S-1 stage of the Saturn vehicle. In order to remedy this issue, cryogenic fluids were found to be sub-cooled by injection of a warm non-condensing gas. Experimental results show that the mechanism behind the sub-cooling is evaporative cooling. It has been shown that a sub-cooled temperature difference of approximately 13 deg F below saturation temperature [1]. The phenomenon of sub-cooling of cryogenic propellants by a non-condensing gas is not readily available with the General Fluid System Simulation Program (GFSSP) [2]. GFSSP is a thermal-fluid program used to analyze a wide variety of systems that are directly impacted by thermodynamics and fluid mechanics. In order to model this phenomenon, additional capabilities had to be added to GFSSP in the form of a FORTRAN coded sub-routine to calculate the temperature of the sub-cooled fluid. Once this was accomplished, the sub-routine was implemented to a GFSSP model that was created to replicate an experiment that was conducted to validate the GFSSP results.

  8. Effect of Residual Noncondensables on Pressurization and Pressure Control of a Zero-Boil-Off Tank in Microgravity

    NASA Technical Reports Server (NTRS)

    Kassemi, Mohammad; Hylton, Sonya; Kartizova, Olga

    2013-01-01

    The Zero-Boil-Off Tank (ZBOT) Experiment is a small-scale experiment that uses a transparent ventless Dewar and a transparent simulant phase-change fluid to study sealed tank pressurization and pressure control with applications to on-surface and in-orbit storage of propellant cryogens. The experiment will be carried out under microgravity conditions aboard the International Space Station in the 2014 timeframe. This paper presents preliminary results from ZBOT's ground-based research that focuses on the effects of residual noncondensable gases in the ullage on both pressurization and pressure reduction trends in the sealed Dewar. Tank pressurization is accomplished through heating of the test cell wall in the wetted and un-wetted regions simultaneously or separately. Pressure control is established through mixing and destratification of the bulk liquid using a temperature controlled forced jet flow with different degrees of liquid jet subcooling. A Two-Dimensional axisymmetric two-phase CFD model for tank pressurization and pressure control is also presented. Numerical prediction of the model are compared to experimental 1g results to both validate the model and also indicate the effect of the noncondensable gas on evolution of pressure and temperature distributions in the ullage during pressurization and pressure control. Microgravity simulations case studies are also performed using the validated model to underscore and delineate the profound effect of the noncondensables on condensation rates and interfacial temperature distributions with serious implications for tank pressure control in reduced gravity.

  9. Critical heat flux on micro-structured zircaloy surfaces for flow boiling of water at low pressures

    SciTech Connect

    Haas, C.; Miassoedov, A.; Schulenberg, T.; Wetzel, T.

    2012-07-01

    The influence of surface structure on critical heat flux for flow boiling of water was investigated for Zircaloy tubes in a vertical annular test section. The objectives were to find suitable surface modification processes for Zircaloy tubes and to test their critical heat flux performance in comparison to the smooth tube. Surface structures with micro-channels, porous layer, oxidized layer, and elevations in micro- and nano-scale were produced on a section of a Zircaloy cladding tube. These modified tubes were tested in an internally heated vertical annulus with a heated length of 326 mm and an inner and outer diameter of 9.5 and 18 mm. The experiments were performed with mass fluxes of 250 and 400 kg/(m{sup 2}s), outlet pressures between 120 and 300 kPa, and constant inlet subcooling enthalpy of 167 kJ/kg. Only a small influence of modified surface structures on critical heat flux was observed for the pressure of 120 kPa in the present test section geometry. However, with increasing pressure the critical heat flux could increase up to 29% using the surface structured tubes with micro-channels, porous and oxidized layers. Capillary effects and increased nucleation site density are assumed to improve the critical heat flux performance. (authors)

  10. Water boiling inside carbon nanotubes: toward efficient drug release.

    PubMed

    Chaban, Vitaly V; Prezhdo, Oleg V

    2011-07-26

    We show using molecular dynamics simulation that spatial confinement of water inside carbon nanotubes (CNTs) substantially increases its boiling temperature and that a small temperature growth above the boiling point dramatically raises the inside pressure. Capillary theory successfully predicts the boiling point elevation down to 2 nm, below which large deviations between the theory and atomistic simulation take place. Water behaves qualitatively different inside narrow CNTs, exhibiting transition into an unusual phase, where pressure is gas-like and grows linearly with temperature, while the diffusion constant is temperature-independent. Precise control over boiling by CNT diameter, together with the rapid growth of inside pressure above the boiling point, suggests a novel drug delivery protocol. Polar drug molecules are packaged inside CNTs; the latter are delivered into living tissues and heated by laser. Solvent boiling facilitates drug release. PMID:21648482

  11. Zero Boil-Off System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, David W.; Johnson, Wesley L.; Feller, Jeffrey R.

    2015-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration due to their high specific impulse for rocket motors of upper stages suitable for transporting 10s to 100s of metric tons of payload mass to destinations outside of low earth orbit and for their return. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for missions with durations greater than several months. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler to control tank pressure. The active thermal control technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center, in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. Testing consisted of three passive tests with the active cryocooler system off, and 7 active tests, with the cryocooler powered up. The test matrix included zero boil-off tests performed at 90 full and 25 full, and several demonstrations at excess cooling capacity and reduced cooling capacity. From this, the tank pressure response with varied cryocooler power inputs was determined. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

  12. Ocean ridge magmatic and hydrothermal geochemical processes

    NASA Astrophysics Data System (ADS)

    Klein, Emily M.

    The ocean ridge system as an interaction site linking the interior of the earth with the lithosphere, biosphere, and hydrosphere is characterized in a critical review of U.S. research from the period 1987-1990. Sections are devoted to magmatic and hydrothermal processes, with particular attention to the chemical variability of MORB, studies of magmatic segmentation in the East Pacific Rise, plans for sampling the Pacific-Antarctic Ridge, regional differences in the extent and pressure of melting, the diversity of oceanic plutonic rocks, observations of active hydrothermal venting, the composition of hydrothermal fluids, models of hydrothermal circulation, and the mineralogy and geochemistry of hydrothermal deposits. A comprehensive bibliography is provided.

  13. Bubble departure size in flow boiling

    NASA Astrophysics Data System (ADS)

    Guan, Peng; Jia, Li; Yin, Liaofei; Tan, Zetao

    2014-12-01

    Flow boiling experiments were conducted in a vertical annular channel to study bubble departure characteristics. Deionized water was used as the working fluid, and the tests were performed at atmospheric pressure. Bubble departure diameters were obtained from the images which were captured by a high-speed digital camera. The relationship between bubble contact diameter and departure diameter was discussed. A new model base on force balance analysis, taking bubble contact diameter into account for predicting bubble departure diameter is proposed in this study. A good agreement between predicted and measured results is achieved.

  14. Optimizing the Combination of Smoking and Boiling on Quality of Korean Traditional Boiled Loin (M. longissimus dorsi)

    PubMed Central

    Choi, Yun-Sang; Kim, Hyun-Wook; Kim, Young-Boong; Kim, Cheon-Jei

    2015-01-01

    The combined effects of smoking and boiling on the proximate composition, technological quality traits, shear force, and sensory characteristics of the Korean traditional boiled loin were studied. Cooking loss, processing loss, and shear force were lower in the smoked/boiled samples than those in the control (without smoking treatment) (p<0.05). The results showed that the boiled loin samples between the control and treatment did not differ significantly in protein, fat, or ash contents, or pH values (p>0.05). The treated samples had higher score for overall acceptability than the control (p<0.05). Thus, these results show that the Korean traditional boiled loin treated with smoking for 60 min before boiling had improved physicochemical properties and sensory characteristics. PMID:26761822

  15. Hydrothermal processes at seafloor spreading centers,

    SciTech Connect

    Rona, P.A.; Bostrom, K.; Laubier, L.; Smith, K.L.

    1983-01-01

    This book examines research on the description and interpretation of hydrothermal and associated phenomena at seafloor spreading centers. An interdisciplinary overview of the subject is presented, including geological, geophysical, geochemical, and biological discoveries. The implications of the discoveries for understanding the earth's heat transfer, geochemical mass balances and cycles, mineralization, and biological adaptation are discussed. Topics considered include geologic setting (e.g., the four dimensions of the spreading axis, geological processes of the mid-ocean ridge), hydrothermal convection (e.g., oxygen and hydrogen isotope studies, the basic physics of water penetration into hot rock), Iceland and oceanic ridges (e.g., chemical evidence from Icelandic geothermal systems, the physical environment of hydrothermal systems), mass balances and cycles (e.g., reduced gases and bacteria in hydrothermal fluids, the effects of hydrothermal activity on sedimentary organic matter), ferromanganese deposits, hydrothermal mineralization, and the biology of hydrothermal vents.

  16. (Boiling water reactor (BWR) CORA experiments)

    SciTech Connect

    Ott, L.J.

    1990-10-16

    To participate in the 1990 CORA Workshop at Kernforschungszentrum Karlsruhe (KfK) GmbH, Karlsruhe, FRG, on October 1--4, and to participate in detailed discussions on October 5 with the KfK CORA Boiling Water Reactor (BWR) experiments. The traveler attended the 1990 CORA Workshop at KfK, FRG. Participation included the presentation of a paper on work performed by the Boiling Water Reactor Core Melt Progression Phenomena Program at Oak Ridge National Laboratory (ORNL) on posttest analyses of CORA BWR experiments. The Statement of Work (November 1989) for the BWR Core Melt Progression Phenomena Program provides for pretest and posttest analyses of the BWR CORA experiments performed at KfK. Additionally, it is intended that ORNL personnel participate in the planning process for future CORA BWR experiments. For these purposes, meetings were held with KfK staff to discuss such topics as (1) experimental test schedule, (2) BWR test conduct, (3) perceived BWR experimental needs, and (4) KfK operational staff needs with respect to ORNL support. 19 refs.

  17. Development boiling to sprinkled tube bundle

    NASA Astrophysics Data System (ADS)

    Kracík, Petr; Pospíšil, Jiří

    2016-03-01

    This paper presents results of a studied heat transfer coefficient at the surface of a sprinkled tube bundle where boiling occurs. Research in the area of sprinkled exchangers can be divided into two major parts. The first part is research on heat transfer and determination of the heat transfer coefficient at sprinkled tube bundles for various liquids, whether boiling or not. The second part is testing of sprinkle modes for various tube diameters, tube pitches and tube materials and determination of individual modes' interface. All results published so far for water as the falling film liquid apply to one to three tubes for which the mentioned relations studied are determined in rigid laboratory conditions defined strictly in advance. The sprinkled tubes were not viewed from the operational perspective where there are more tubes and various modes may occur in different parts with various heat transfer values. The article focuses on these processes. The tube is located in a low-pressure chamber where vacuum is generated using an exhauster via ejector. The tube consists of smooth copper tubes of 12 mm diameter placed horizontally one above another.

  18. Zero Boil-Off System Testing

    NASA Technical Reports Server (NTRS)

    Plachta, D. W.; Johnson, W. L.; Feller, J. R.

    2015-01-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration plans due to their high specific impulse for rocket motors of upper stages. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for long duration missions. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler temperature to control tank pressure. The technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

  19. Zero boil-off system testing

    NASA Astrophysics Data System (ADS)

    Plachta, D. W.; Johnson, W. L.; Feller, J. R.

    2016-03-01

    Cryogenic propellants such as liquid hydrogen (LH2) and liquid oxygen (LO2) are a part of NASA's future space exploration plans due to their high specific impulse for rocket motors of upper stages. However, the low storage temperatures of LH2 and LO2 cause substantial boil-off losses for long duration missions. These losses can be eliminated by incorporating high performance cryocooler technology to intercept heat load to the propellant tanks and modulating the cryocooler temperature to control tank pressure. The technology being developed by NASA is the reverse turbo-Brayton cycle cryocooler and its integration to the propellant tank through a distributed cooling tubing network coupled to the tank wall. This configuration was recently tested at NASA Glenn Research Center in a vacuum chamber and cryoshroud that simulated the essential thermal aspects of low Earth orbit, its vacuum and temperature. This test series established that the active cooling system integrated with the propellant tank eliminated boil-off and robustly controlled tank pressure.

  20. Lead chloride crystal growth from boiling solutions

    NASA Astrophysics Data System (ADS)

    Veintemillas-Verdaguer, S.; Rodríguez-Clemente, R.; Torrent-Burgues, J.

    1993-03-01

    Lead chloride single crystals can be grown from boiling solutions using KNO3-H20 solutions as a solvent. Crystals of 1 mm size produced by gel-growth technique were used as seeds. The solubility of PbC12 increases almost linearly with the KNO3 molality being 0.63m in a 7m KNO3 aqueous solutions at 105°C and pH = 2.6; this increase is related to the decrease of the activity coefficient of lead chloride in these solutions. In the first experiments, the supersaturation was attained by solvent extraction, but due to the simultaneous changes in the concentration of the KNO3 mineralizer during the extraction, the growth rate was irregular and defective crystals were obtained. The experimental set-up was therefore modified and a transport technique was added to the system in order to feed the boiling reactor continuously with fresh lead chloride solution. The growth of the crystals takes place at constant concentration of KNO3 in these new conditions. With this experimental modification, isometric PbCI2 crystals of up to lcm size were obtained in three weeks. The observed morphology is close to that calculated by Woensdregt and Hartmann [J. Crystal Growth 87(1988)561].

  1. Droplet Impingement Boiling on Heated Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Crockett, Julie; Clavijo, Cristian; Maynes, Daniel

    2015-11-01

    When a droplet impinges on a solid surface at a temperature well above the saturation temperature, vaporization of the liquid begins immediately after contact. Different boiling regimes may result depending on the surface temperature and volatility of the liquid. The nucleate boiling regime is characterized by explosive atomization, which occurs when vapor bubbles burst causing an extravagant shower of small micro droplets as well as the well-known ``sizzling'' sound. In this work, we show that the vapor is surprisingly re-directed during impingement on a superhydrophobic surface such that atomization is completely suppressed. We hypothesize that this occurs because vapor escapes through the superhydrophobic interface such that the top of the droplet remains free of bursting vapor bubbles. We explore a wide range of surface patterning with feature spacing of 8 to 32 microns and solid area fractions of 10 to 50 percent; surface temperatures from 100 C to 400 C; and Weber numbers of 1 to 100. Atomization is found to decrease with increasing feature spacing and decreasing solid fraction, and vanishes completely for large spacing. It may be that large feature spacing promotes early transition to the Leidenfrost regime.

  2. Effects of glacial ice on subsurface temperatures of hydrothermal systems in Yellowstone National Park, Wyoming: Fluid-inclusion evidence

    SciTech Connect

    Bargar, K.E.; Fournier, R.O. )

    1988-12-01

    Hydrothermal quartz and fluorite crystals containing liquid-rich fluid inclusions (coexisting vapor-rich fluid inclusions were not observed) were found in drill cores from eight relatively shallow research holes drilled by the US Geological Survey in and near major geyser basins of Yellowstone National Park. Homogenization temperatures (T{sub h}) for mostly secondary fluid inclusions show variations in temperature that have occurred at give depths since precipitation of the host minerals. Within major hydrothermal upflow zones, fluid-inclusion T{sub h} values all were found to be equal to or higher (commonly 20-50 C and up to 155 C higher) than present temperatures at the depths sampled. During periods when thick glacial ice covered the Yellowstone National Park region, pore-fluid pressures in the underlying rock were increased in proportion to the weight of the overlying column of ice. Accordingly, theoretical reference boiling-point curves that reflect the maximum temperature attainable in a hot-water geothermal system at a given depth were elevated, and temperatures within zones of major hydrothermal upflow (drill holes Y-2, Y-3, Y-6, Y-11, Y-13, and upper part of Y-5) increased. The thicknesses of ice required to elevate boiling-point curves sufficiently to account for the observed fluid-inclusion T{sub h} values are within the ranges estimated by glacial geologic studies. At the margins of major hydrothermal upflow zones (drill holes Y-4 and Y-9), fluid-inclusion T{sub h} values at given depths range from 57 C lower to about the same as the current temperature measurements because of a previous decrease in the rate of discharge of warm water and/or an increase in the rate of recharge of cold water into the hydrothermal system.

  3. TRAC analysis of the effect of increased ECC subcooling on the reflood transient in the Slab Core Test Facility. [PWR

    SciTech Connect

    Smith, S.T.

    1982-01-01

    A blind posttest calculation of Slab Core Test Facility (SCTF) Run 510, the high-subcooling test, was completed with TRAC-PD2/MOD1 using initial conditions provided by the Japan Atomic Energy Research Institute (JAERI), but without knowledge of the actual test results. There is good comparison between the calculation and the data for rod temperatures, turnaround times, core differential pressures, and mass inventories, and reasonable comparison for absolute pressures, upper plenum pool formation, and fluid temperatures and mass accumulation in the steam-water separator. Comparison of this calculation with the calculation of the base case test (Run 507) shows that the qualitative behavior during reflood is calculated correctly for both cases. In addition, from this comparison the following conclusions can be drawn: for the high-subcooling case, the peak rod temperture was lower, calculated quench times were earlier, there was more entrainment and liquid carryover from the core to the upper plenum, and the liquid mass accumulation in both the core and the upper plenum was greater.

  4. Potential cavitating venturi modifications to improve performance at low inlet subcooling: Backward facing steps and threaded throats

    SciTech Connect

    Ungar, E.K.; Mai, T.D.

    1994-12-31

    Cavitating venturis (CVs) were to be used to passively control the flow of liquid ammonia to the evaporators in the Space Station Freedom (SSF) two-phase active thermal control system (ATCS). Because the SSF ATCS CVs would have operated at a low value of inlet subcooling (on the order of 100 kPa or 15 psid) to conserve electrical power, an overflow phenomenon could have occurred. During overflow the mass flow rate is higher than the choked limit. Once overflow occurs, cavitation is reestablished only when the downstream pressure is decreased to a low value. To reduce or eliminate the occurrence of CV overflow in the SSF ATCS, several design solutions were developed, manufactured, and tested. Cavitating venturis with a backwards facing step immediately downstream of the throat were tested, as was a cavitating venturi with a threaded throat. Overflow recovery data were obtained for modified cavitating venturis and for unmodified CVs with identical throat sizes and geometry. In the present work, the rationale behind the CV modifications is outlined and the final designs are described. The test apparatus and test approach are summarized, and the experiment results are discussed for both the modified and unmodified CVs. The net effects of the modifications are reviewed, and recommendations are made for use of cavitating venturis at low inlet subcooling.

  5. Mineralogy, geochemistry and fluid evolution of a fossil hydrothermal system in the Paleogene Mendejin volcanic sequence, East Azarbaijan, Iran

    NASA Astrophysics Data System (ADS)

    Karimzadeh Somarin, A.; Lentz, D. R.

    2008-09-01

    The Mendejin area is one prominent hydrothermal alteration zone in association with Paleogene volcano-sedimentary sequences in NW Iran. The volcanic sequence at Mendejin ranges in composition from basalt to andesite, dacite and rhyolite. Sulfide mineralization and related hydrothermal alteration is associated with the late Mendejin pluton that discordantly intrudes into this cogenetic volcanic sequence. The common hypogene hydrothermal alteration types observed at Mendejin include; phyllic, propylitic, carbonatization, sulfidation, silicification (veins) and argillic types with locally abundant calcite, quartz, tourmaline, sericite, chlorite, kaolinite, illite, alunite, jarosite, and gypsum. Phyllic alteration (without calcite and epidote) is paragenetically early and it is followed by propylitic alteration (with epidote and little calcite) and carbonatization (with high calcite and no epidote) reflecting a gradual increase of CO2 in the hydrothermal system. Mass balance of the hydrothermal alteration within the various volcanic rocks indicates that most elements released during alteration were locally fixed in the low-temperature hydrothermal minerals. As a result, geochemical changes are not as prominent as mineralogical transformations. There is no net mass change during phyllic, argillic, silicic vein and carbonate alteration of andesite and basalt. However, propylitic alteration and carbonatization of dacite caused net mass additions of 8% and 17%, respectively. The high-field-strength elements (HFSE) like Ti, Zr, Hf, Th, Nd, Y, La, Ce, Sm and Lu were the immobile elements during hydrothermal alteration at Mendejin. However, the rare-earth elements (REE) were mobilized during carbonate alteration. Fluid inclusions in quartz and calcite from various assemblages show that hydrothermal minerals were deposited from a low salinity (0.35 to 4.34 wt% equivalent NaCl) hydrothermal solution at 385°C to 150°C. Fluid-wall rock reactions along with boiling of hydrothermal solution and mixing of relatively saline fluid (4.34 wt% equivalent NaCl) with a low-salinity groundwater (0.35 wt% equivalent NaCl) resulted in the extensive alteration of the volcanic country rocks and precipitation of hydrothermal assemblages at Mendejin.

  6. Prospective Primary School Teachers' Perceptions on Boiling and Freezing

    ERIC Educational Resources Information Center

    Senocak, Erdal

    2009-01-01

    The aim of this study was to investigate the perceptions of prospective primary school teachers on the physical state of water during the processes of boiling and freezing. There were three stages in the investigation: First, open-ended questions concerning the boiling and freezing of water were given to two groups of prospective primary school…

  7. Quality changes of shrimp during boiling in salt solution.

    PubMed

    Niamnuy, C; Devahastin, S; Soponronnarit, S

    2007-06-01

    Boiling shrimp in salt solution is an important step during the production of dried shrimp. In this study the effects of various boiling parameters, namely, concentration of salt solution (2, 3, and 4% w/v), mass ratio of shrimp to salt solution (1:2 and 1:3), boiling time (1, 3, 5, and 7 min), and shrimp size (small and large), on the various quality attributes of shrimp were investigated. The quality of boiled shrimp was evaluated in terms of its salt content, moisture content, which is in turn related to the other qualities, namely, protein content, colors, shrinkage, and texture (hardness and toughness), as well as microbiological quality. It was found that higher concentration of salt solution and longer boiling time and lower mass ratio of shrimp to salt solution led to higher salt content of shrimp but to lower levels of moisture and proteins, leading to higher values of hardness, toughness, shrinkage, and color changes of shrimp. However, the mass ratio of shrimp to salt solution alone did not significantly affect any qualities of boiled shrimp (P > 0.05). It was found that the minimum boiling time of 3 min was enough to reduce the number of microorganisms to a safe level and inactivate enzymes causing melanosis in boiled shrimp. PMID:17995744

  8. 17. RW Meyer Sugar Mill: 18761889. Boiling House, 1878. View: ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    17. RW Meyer Sugar Mill: 1876-1889. Boiling House, 1878. View: Southwest corner of boiling house. The amimal-powered cane mill is located in the undergrowth in the right foreground, - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  9. 18. RW Meyer Sugar Mill: 18761889. Boiling House Interior, 1878. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. RW Meyer Sugar Mill: 1876-1889. Boiling House Interior, 1878. View: Detail of floor with molasses pits below floor level. The remaining floor boards indicate the structure of the floor covering the entire inside of the boiling house. In the left background the base of the centrifugals are in view. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  10. Explosive Boiling at Very Low Heat Fluxes: A Microgravity Phenomenon

    NASA Technical Reports Server (NTRS)

    Hasan, M. M.; Lin, C. S.; Knoll, R. H.; Bentz, M. D.

    1993-01-01

    The paper presents experimental observations of explosive boiling from a large (relative to bubble sizes) flat heating surface at very low heat fluxes in microgravity. The explosive boiling is characterized as either a rapid growth of vapor mass over the entire heating surface due to the flashing of superheated liquid or a violent boiling spread following the appearance of single bubbles on the heating surface. Pool boiling data with saturated Freon 113 was obtained in the microgravity environment of the space shuttle. The unique features of the experimental results are the sustainability of high liquid superheat for long periods and the occurrence of explosive boiling at low heat fluxes (0.2 to 1.2 kW/sq m). For a heat flux of 1.0 kW/sq m a wall superheat of 17.9 degrees C was attained in ten minutes of heating. This was followed by an explosive boiling accompanied with a pressure spike and a violent bulk liquid motion. However, at this heat flux the vapor blanketing the heating surface could not be sustained. Stable nucleate boiling continued following the explosive boiling.

  11. Hydrothermal Monitoring in a Quiescent Volcanic Arc: Cascade Range, Northwestern United States

    NASA Astrophysics Data System (ADS)

    Gelwick, K.; Randolph-Flagg, N. G.; Crankshaw, I. M.; McCulloch, C. L.; Lundstrom, E. A.; Murveit, A. M.; Bergfeld, D.; Spicer, K.; Tucker, D.; Schmidt, M. E.; Mariner, R. H.; Evans, W.; Ingebritsen, S.

    2013-12-01

    Ongoing (1996-present) volcanic unrest near South Sister, Oregon, is accompanied by a striking set of hydrothermal anomalies, including elevated temperatures, elevated major-ion concentrations, and 3He/4He ratios as large as 8.6 RA in slightly thermal springs. These observations prompted the U.S. Geological Survey to begin a systematic hydrothermal-monitoring effort encompassing 25 sites and 10 of the highest-risk volcanoes in the Cascade Range volcanic arc, from Mount Baker near the Canadian border to Mount Lassen in northern California. A concerted effort was made to develop hourly records of temperature and (or) hydrothermal solute flux spanning multiple years, suitable for comparison with other continuous geophysical monitoring data. Monitored sites included summit-fumarole groups and springs/streams that show clear evidence of magmatic influence in the form of high 3He/4He ratios and (or) large fluxes of magmatic CO2 or heat. As of 2009-2012 measured summit-fumarole temperatures in the Cascade Range were generally near or below the local pure-water boiling point; the maximum observed superheat was <+2.5°C at Mount Baker. Temporal variability in ground-temperature records from the summit-fumarole sites is temperature-dependent, with the hottest sites tending to show less variability. Seasonal variability in the flux of hydrothermally sourced major anions from the springs varied from essentially undetectable to a factor of 5-10. This range of observed behavior owes mainly to the local climate regime, with strongly snowmelt-influenced springs and streams exhibiting more variability. As of the end of the 2012 field season, there had been 87 occurrences of local seismic energy densities ~>0.001 J/m3 during periods of hourly record. Hydrothermal responses to these small seismic stimuli were generally undetectable or ambiguous. Evaluation of multiyear to multi-decadal trends indicates that whereas the hydrothermal system at Mount St. Helens is still fast-evolving in response to the 1980-present eruptive cycle, there is no clear evidence of ongoing long-term trends in hydrothermal activity at other Cascade Range volcanoes that have been active or restless during the past century (Baker, South Sister, and Lassen). Experience gained during the Cascade Range hydrothermal-monitoring experiment informs ongoing efforts to capture entire unrest cycles at more active but generally less accessible volcanoes such as those in the Aleutian arc.

  12. Phreatic and Hydrothermal Explosions: A Laboratory Approach

    NASA Astrophysics Data System (ADS)

    Scheu, B.; Dingwell, D. B.

    2010-12-01

    Phreatic eruptions are amongst the most common eruption types on earth. They might be precursory to another type of volcanic eruption but often they stand on their one. Despite being the most common eruption type, they also are one of the most diverse eruptions, in appearance as well as on eruption mechanism. Yet steam is the common fuel behind all phreatic eruptions. The steam-driven explosions occur when water beneath the ground or on the surface is heated by magma, lava, hot rocks, or fresh volcanic deposits (such as ignimbrites, tephra and pyroclastic-flow deposits) and result in crater, tuff rings and debris avalanches. The intense heat of such material may cause water to boil and flash to steam, thereby generating an explosion of steam, water, ash, blocks, and bombs. Another wide and important field affected by phreatic explosions are hydrothermal areas; here phreatic explosions occur every few months creating explosion craters and resemble a significant hazard to hydrothermal power plants. Despite of their hazard potential, phreatic explosions have so far been overlooked by the field of experimental volcanology. A part of their hazard potential in owned by the fact that phreatic explosions are hardly predictable in occurrence time and size as they have manifold triggers (variances in groundwater and heat systems, earthquakes, material fatigue, water level, etc..) A new set of experiments has been designed to focus on this phreatic type of steam explosion, whereas classical phreatomagmatic experiments use molten fuel-coolant interaction (e.g., Zimanowski, et al., 1991). The violent transition of the superheated water to vapour adds another degree of explosivity to the dry magmatic fragmentation, driven mostly by vesicle bursting due to internal gas overpressure. At low water fractions the fragmentation is strongly enforced by the mixture of these two effects and a large fraction of fine pyroclasts are produced, whereas at high water fraction in the sample the fragmentation is less violent as its dry counterpart. The experimental conditions used it this study (varying degree of water saturation, moderate overpressure, 200- 300°C) applies e.g. to volcanic rocks as well as country rocks at depth of about 100-800 m in a conduit or dome bearing a fraction of ground water and being heated from magma rising beneath (150-400°C). The diversity of phreatic eruptions at a volcanic system (vent) arises from the variety of host rocks, ways to seal the conduit, and to alter this material depending on the composition of volcanic gases. Here, we assess the influence of rapid decompression of the supercritical water phase in the pore space of samples, on the fragmentation behaviour. This will enable us to elucidate the characteristics of the different “fuels” for explosive fragmentation (gas overpressure, steam flashing), as well as their interplay.

  13. Boron isotope systematics of hydrothermal fluids from submarine hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Yamaoka, K.; Hong, E.; Ishikawa, T.; Gamo, T.; Kawahata, H.

    2013-12-01

    Boron is highly mobile in submarine hydrothermal systems and useful to trace the process of water-rock reaction. In this study, we measured the boron content and isotopic composition of vent fluids collected from arc-backarc hydrothermal systems in the western Pacific. In sediment-starved hydrothermal systems (Manus Basin, Suiyo Seamount, and Mariana Trough), the boron content and isotopic composition of vent fluids are dependent on type of host rock. The end member fluids from MORB-like basalt-hosted Vienna Woods in the Manus Basin showed low boron content and high δ11B value (0.53 mM, 29.8‰), while dacite-hosted PACMANUS and the Suiyo Seamount showed high boron contents and low δ11B values (1.45 and 1.52 mM, 13.6 and 18.5‰, respectively). The Alice Springs and Forecast Vent field in the Mariana Trough showed values intermediate between them (0.72 and 0.63 mM, 19.9 and 24.0‰, respectively), reflecting reaction of seawater and basalt influenced by slab material. In phase separated hydrothermal systems (North Fiji Basin), boron content and isotopic composition of vent fluids (0.44-0.56 mM, 34.5-35.9‰) were similar to those in the Vienna Woods. Considering little fractionation of boron and boron isotope during phase separation demonstrated by the previous experimental studies, it is suggested that the host rock in the North Fiji Basin is MORB-like basalt. In sediment-hosted hydrothermal system (Okinawa Trough), the reaction with boron-enriched sediment following seawater-rock reaction resulted in significantly high boron contents and low δ11B values of vent fluids (4.4-5.9 mM, 1.5-2.6‰). The water-sediment ratio was estimated to be ~2. In spite of the different geological settings, the end member fuids from all vent fields are enriched in B relative to seawater (0.41 mM, 39.6‰) and the δ11B values are inversely propotional to the boron concentrations. It suggests that boron isotopic composition of vent fluid predominantly depends on the amount of boron originated from solid-phase.

  14. Turning bubbles on and off during boiling using charged surfactants

    NASA Astrophysics Data System (ADS)

    Cho, H. Jeremy; Mizerak, Jordan P.; Wang, Evelyn N.

    2015-10-01

    Boiling--a process that has powered industries since the steam age--is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles `on and off' independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications.

  15. Reliquefaction of boil-off from liquefied natural gas

    SciTech Connect

    Cook, P.J.

    1989-07-11

    This patent describes a process for liquifying boil-off gas resulting from the evaporation of liquified natural gas contained in a storage vessel. The boil-off gas is cooled and liquified in a closed-loop refrigeration system and then returned to the storage vessel wherein. The closed-loop refrigeration system comprises the steps: compressing nitrogen as a working fluid in a compressor system to form a compressed working fluid; splitting the compressed working fluid into a first and second stream; isenthalpically expanding the first stream to produce a cooled first stream, then warming against boil-off gas and compressed working fluid; and isentropically expanding the second stream to form a cooled expanded stream which is then warmed against boil-off gas to form at least partially condensed boil-off prior to warming against the working fluid and prior to return to the compressor system.

  16. Stability of electric heaters in the boiling heat transfer process

    SciTech Connect

    Loeffler, R.I.

    1991-01-01

    Boiling heat transfer from electrically heated wires and composite heaters was studied in the three boiling regimes; nucleate, transition, and film. The electrical input to the heaters was controlled by the heater temperature through the use of feedback control techniques. Particular attention was paid to the transition region of the boiling curve where the slope is negative and operation is unstable without proper control. Boiling curves produced by an x-ray plotter are presented for gold-plated tungsten wires and also for platinum wires. Stability conditions and transfer functions were developed for a complete composite heater system. Steady-state operation in the transition region of the boiling curve clearly demonstrates that there are two separate transition curves depending on whether the temperature is increasing or decreasing.

  17. Little low-power boiling never hurt anybody. [LMFBR

    SciTech Connect

    Dunn, F.E.

    1985-01-01

    Failures in the shutdown heat removal system of an LMFBR might lead to flow stagnation and coolant boiling in the reactor core. At normal operating power, the onset of sodium boiling will lead to film dryout and melting of the cladding and fuel within a few seconds. On the other hand, both calculations and currently available experimental data indicate that at heat fluxes corresponding to decay heat power levels, boiling leads to improved heat removal; and it limits the temperature rise in the fuel pins. Therefore, when setting safety criteria for decay heat removal systems, there is no reason to preclude sodium boiling per se because of heat removal considerations. As an example that illustrates the beneficial impact of coolant boiling, a case involving temporary loss of feedwater and staggered pump failures in a hypothetical, 1000-MWe loop-type reactor was run in the SASSYS-1 code.

  18. Conversion of direct process high-boiling residue to monosilanes

    DOEpatents

    Brinson, Jonathan Ashley; Crum, Bruce Robert; Jarvis, Jr., Robert Frank

    2000-01-01

    A process for the production of monosilanes from the high-boiling residue resulting from the reaction of hydrogen chloride with silicon metalloid in a process typically referred to as the "direct process." The process comprises contacting a high-boiling residue resulting from the reaction of hydrogen chloride and silicon metalloid, with hydrogen gas in the presence of a catalytic amount of aluminum trichloride effective in promoting conversion of the high-boiling residue to monosilanes. The present process results in conversion of the high-boiling residue to monosilanes. At least a portion of the aluminum trichloride catalyst required for conduct of the process may be formed in situ during conduct of the direct process and isolation of the high-boiling residue.

  19. Size-exclusion chromatography for the determination of the boiling point distribution of high-boiling petroleum fractions.

    PubMed

    Boczkaj, Grzegorz; Przyjazny, Andrzej; Kamiński, Marian

    2015-03-01

    The paper describes a new procedure for the determination of boiling point distribution of high-boiling petroleum fractions using size-exclusion chromatography with refractive index detection. Thus far, the determination of boiling range distribution by chromatography has been accomplished using simulated distillation with gas chromatography with flame ionization detection. This study revealed that in spite of substantial differences in the separation mechanism and the detection mode, the size-exclusion chromatography technique yields similar results for the determination of boiling point distribution compared with simulated distillation and novel empty column gas chromatography. The developed procedure using size-exclusion chromatography has a substantial applicability, especially for the determination of exact final boiling point values for high-boiling mixtures, for which a standard high-temperature simulated distillation would have to be used. In this case, the precision of final boiling point determination is low due to the high final temperatures of the gas chromatograph oven and an insufficient thermal stability of both the gas chromatography stationary phase and the sample. Additionally, the use of high-performance liquid chromatography detectors more sensitive than refractive index detection allows a lower detection limit for high-molar-mass aromatic compounds, and thus increases the sensitivity of final boiling point determination. PMID:25545251

  20. The initiation of boiling during pressure transients. [water boiling on metal surfaces

    NASA Technical Reports Server (NTRS)

    Weisman, J.; Bussell, G.; Jashnani, I. L.; Hsieh, T.

    1973-01-01

    The initiation of boiling of water on metal surfaces during pressure transients has been investigated. The data were obtained by a new technique in which light beam fluctuations and a pressure signal were simultaneously recorded on a dual beam oscilloscope. The results obtained agreed with those obtained using high speed photography. It was found that, for water temperatures between 90-150 C, the wall superheat required to initiate boiling during a rapid pressure transient was significantly higher than required when the pressure was slowly reduced. This result is explained by assuming that a finite time is necessary for vapor to fill the cavity at which the bubble originates. Experimental measurements of this time are in reasonably good agreement with calculations based on the proposed theory. The theory includes a new procedure for estimating the coefficient of vaporization.

  1. High level disinfection of a home care device; to boil or not to boil?

    PubMed

    Winthrop, K L; Homestead, N

    2012-03-01

    We developed a percutaneous electrical transducer for home therapy of chronic pain, a device that requires high level disinfection between uses. The utility of boiling water to provide high level disinfection was evaluated by inoculating transducer pads with potential skin pathogens (Staphylococcus aureus, Mycobacterium terrae, Pseudomonas aeruginosa, Candida albicans) and subjecting them to full immersion in water boiling at 4200 feet elevation (95 °C). Log10 reductions in colony-forming units (cfu) at 10 min were 7.1, >6.3 and >5.5 for S. aureus, P. aeruginosa and C. albicans, respectively, but only 4.6 for M. terrae. At 15 min the reductions had increased to 7.5, >6.8, >6.6 and >7.5 cfu, respectively. PMID:22277192

  2. Enhanced boiling heat transfer using radial fins

    NASA Astrophysics Data System (ADS)

    Razelos, P.; Das, S.; Krikkis, R. N.

    2008-04-01

    A numerical bifurcation analysis is carried out in order to determine the solution structure of radial fins subjected to multi-boiling heat transfer mode. One-dimensional conduction is employed throughout the thermal analysis. The fluid heat transfer coefficient is temperature dependent on the three regimes of phase-change of the fluid. Six fin profiles, defined in the text, are considered. Multiplicity structure is obtained to determine different types of bifurcation diagrams, which describe the dependence of a state variable of the system like the temperature or the heat dissipation on the fin design parameters, conduction convection parameter (CCP) or base temperature difference (Δ T). Specifically, the effects of Δ T, CCP and Biot number are analyzed. The results are presented graphically, showing the significant behavioral features of the heat rejection mechanism.

  3. The Physics of Boiling at Burnout

    NASA Technical Reports Server (NTRS)

    Theofanous, T. G.; Tu, J. P.; Dinh, T. N.; Salmassi, T.; Dinh, A. T.; Gasljevic, K.

    2000-01-01

    The basic elements of a new experimental approach for the investigation of burnout in pool boiling are presented. The approach consists of the combined use of ultrathin (nano-scale) heaters and high speed infrared imaging of the heater temperature pattern as a whole, in conjunction with highly detailed control and characterization of heater morphology at the nano and micron scales. It is shown that the burnout phenomenon can be resolved in both space and time. Ultrathin heaters capable of dissipating power levels, at steady-state, of over 1 MW/square m are demonstrated. A separation of scales is identified and it is used to transfer the focus of attention from the complexity of the two-phase mixing layer in the vicinity of the heater to a micron-scaled microlayer and nucleation and associated film-disruption processes within it.

  4. High-temperature synthesis of highly hydrothermal stable mesoporous silica and Fe-SiO{sub 2} using ionic liquid as a template

    SciTech Connect

    Liu, Hong; Wang, Mengyang; Hu, Hongjiu; Liang, Yuguang; Wang, Yong; Cao, Weiran; Wang, Xiaohong

    2011-03-15

    Mesoporous silicas and Fe-SiO{sub 2} with worm-like structures have been synthesized using a room temperature ionic liquid, 1-hexadecane-3-methylimidazolium bromide, as a template at a high aging temperature (150-190 {sup o}C) with the assistance of NaF. The hydrothermal stability of mesoporous silica was effectively improved by increasing the aging temperature and adding NaF to the synthesis gel. High hydrothermally stable mesoporous silica was obtained after being aged at 190 {sup o}C in the presence of NaF, which endured the hydrothermal treatment in boiling water at least for 10 d or steam treatment at 600 {sup o}C for 6 h. The ultra hydrothermal stability could be attributed to its high degree of polymerization of silicate. Furthermore, highly hydrothermal stable mesoporous Fe-SiO{sub 2} has been synthesized, which still remained its mesostructure after being hydrothermally treated at 100 {sup o}C for 12 d or steam-treated at 600 {sup o}C for 6 h. -- Graphical abstract: Worm-like mesoporous silica and Fe-SiO{sub 2} with high hydrothermal stability have been synthesized using ionic liquid 1-hexadecane-3-methylimidazolium bromide as a template under the assistance of NaF at high temperature. Display Omitted Research highlights: {yields} Increasing aging temperature improved the hydrothermal stability of materials. {yields}Addition of NaF enhanced the polymerization degree of silicates. {yields} Mesoporous SiO{sub 2} and Fe-SiO{sub 2} obtained have remarkable hydrothermal stability.

  5. Densities of liquids and vapors in boiling NaCl-H2O solutions: a PVTx summary from 300° to 500°C

    USGS Publications Warehouse

    Bischoff, James L.

    1991-01-01

    Experimental data for densities of liquids and vapors on the two-phase surface of the system NaCl-H2O were compiled and evaluated to provide a complete summary between 300° and 500°C. The results are added to a previously published PTx summary compiled in the same manner to provide a PVTx summary of the present state of knowledge. Results are in table form of use to the understanding of two-phase behaviour in boiling hydrothermal systems and to theoretical modeling of this important system. 

  6. Where are the large hydrothermal sulphide deposits in the oceans?

    NASA Astrophysics Data System (ADS)

    Fouquet, Y.

    Large sulphide deposits have been identified on slow and fast spreading ridges and back-arc basins. Their formation is controlled by a combination of several conditions, each of which alone is often only compatible with the formation of small and unstable deposits. The geological control of deposits has to be considered both at the regional and local scales. The convective system is dependent on the morphology of the heat source (magma chamber) and the magma supply. Major sites are controlled by regional topographic highs that are the locus of the highest magma and heat supply along the ridge. On slow spreading ridges the flow of hydrothermal fluids can also be controlled by major regional rift valley faults. The discharge within a field is controlled by the local near surface permeability related to faulting or permeability of rocks. Recent discoveries considerably enlarge the potential locations of hydrothermal activity. On slow spreading ridges we have now to consider the base and top of the rift valley walls and the non-transform offsets, in addition to the relatively well documented control by volcanic topographic highs. Known sites also demonstrate that slow spreading ridges are more favourable for the formation of extensive mineralization. On fast spreading ridges, deposits are numerous and very small because the upflow zone is relatively narrow and subject to perturbation by frequent tectonic and volcanic activity. However, near fast spreading ridges, first order sulphide deposits can be formed on off-axial seamounts. Geological and physical conditions are key parameters controlling the morphology and potential size of deposits. Among these parameters, boiling, mixing within the crust, or precipitation under an impermeable cap rock, can enhance the formation of extensive subsurface mineralization within the oceanic crust. However, the knowledge of these deposits requires further investigation in the vertical dimension.

  7. Chemical and biochemical transformations in hydrothermal plumes

    NASA Astrophysics Data System (ADS)

    Lilley, Marvin D.; Feely, Richard A.; Trefry, John H.

    Hydrothermal plumes integrate the heat and mass flux originating at seafloor hydrothermal vents thereby providing both a means of detecting hydrothermal activity and estimating hydrothermal fluxes. Many chemical species are introduced into the deep sea via hydrothermal plumes (Figure 1) in concentrations many orders of magnitude higher than that existing in background seawater (e.g. H2, CH4 3He, Mn, Fe) while others are scavenged from seawater by hydrothermal particles (e.g. PO4-3, V, As, rare earth elements, Th). Dilution by entrainment of background seawater in the buoyant portion of the plume is very rapid (see chapters by Lupton and McDuff, this volume) such that the hydrothermal component in the near-field portion of the neutrally buoyant plume represents only about 0.01% of the mixture. Nevertheless, chemical tracers such as 3He, CH4, and Mn are widely utilized in addition to temperature, salinity, and light transmission anomalies to detect hydrothermal venting and to draw inferences about the nature of the underlying geochemistry of the hydrothermal system. Many other chemical tracers can be utilized during plume studies to provide additional information about the nature of the venting. These include particles, H2, Al, and radioisotopes, among others.

  8. Reliquefaction of boil-off from liquefied natural gas

    SciTech Connect

    Stuber, W.G.; Kovak, K.W.

    1989-07-04

    This patent describes a process for liquifying boil-off gas resulting from the evaporation of liquified natural gas contained in a storage vessel, the boil-off gas being cooled and liquified in a closed-loop nitrogen refrigeration system and then returned to the storage vessel. The closed loop refrigeration system comprises the following steps: compressing nitrogen as a working fluid in a multi-stage compressor system having an initial and final stage to form a compressed working fluid; splitting the compressed working fluid into a first and second stream; isenthalpically expanding the first stream to produce a cooled first stream, then warming against recycle compressed working fluid and boil-off gas; isentropically expanding the second stream to form a cooled expanded stream which is then warmed against boil-off gas and working fluid prior to return to the compressor system; the improvement for reliquefying a boil-off gas containing from about 0 to 10% nitrogen by volume. It comprises: effecting isenthalpic expansion of the first stream under conditions such that at least a liquid fraction is generated; separating any vapor fraction, if generated, from the liquid fraction; warming the vapor fraction, if generated, against boil-off gas and recycle compressed working fluid; pressurizing the liquid fraction formed by pumping; warming the pressurized liquid fraction first against boil-off gas and then in parallel with the warming of the isentropically expanded second stream.

  9. Transition boiling heat transfer and the film transition regime

    NASA Technical Reports Server (NTRS)

    Ramilison, J. M.; Lienhard, J. H.

    1987-01-01

    The Berenson (1960) flat-plate transition-boiling experiment has been recreated with a reduced thermal resistance in the heater, and an improved access to those portions of the transition boiling regime that have a steep negative slope. Tests have been made in Freon-113, acetone, benzene, and n-pentane boiling on horizontal flat copper heaters that have been mirror-polished, 'roughened', or teflon-coated. The resulting data reproduce and clarify certain features observed by Berenson: the modest surface finish dependence of boiling burnout, and the influence of surface chemistry on both the minimum heat flux and the mode of transition boiling, for example. A rational scheme of correlation yields a prediction of the heat flux in what Witte and Lienhard (1982) previously identified as the 'film-transition boiling' region. It is also shown how to calculate the heat flux at the boundary between the pure-film, and the film-transition, boiling regimes, as a function of the advancing contact angle.

  10. A Fundamental Study of Nucleate Pool Boiling Under Microgravity

    NASA Technical Reports Server (NTRS)

    Ervin, Jamie S.; Merte, Herman, Jr.

    1996-01-01

    An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal-resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- 1 experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, the bulk liquid temperatures. High speed photography (up to 1,000 frames per second) was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface, some observed here for the first time, are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels (on the order of 5 W/cm(exp 2)) is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

  11. A fundamental study of nucleate pool boiling under microgravity

    NASA Technical Reports Server (NTRS)

    Ervin, Jamie S.; Merte, Herman, Jr.

    1991-01-01

    An experimental study of incipient boiling in short-term microgravity and with a/g = +/- 1 for pool boiling was performed. Calibrated thin gold films sputtered on a smoothly polished quartz surface were used simultaneously for thermal resistance measurements and heating of the boiling surface. The gold films were used for both transient and quasi-steady heating surface temperature measurements. Two test vessels were constructed for precise measurement and control of fluid temperature and pressure: a laboratory pool boiling vessel for the a/g = +/- experiments and a pool boiling vessel designed for the 131 m free-fall in the NASA Lewis Research Center Microgravity Research Facility for the microgravity tests. Measurements included the heater surface temperature, the pressure near the heating surface, and the bulk liquid temperatures. High speed photography was used in the experiments. With high quality microgravity and the measured initial temperature of the quiescent test fluid, R113, the temperature distribution in the liquid at the moment of boiling inception resulting from an imposed step in heat flux is known with a certainty not possible previously. The types of boiling propagation across the large flat heating surface are categorized; the conditions necessary for their occurrence are described. Explosive boiling propagation with a striking pattern of small scale protuberances over the entire vapor mass periphery not observed previously at low heat flux levels is described. For the heater surface with a/g = -1, a step in the heater surface temperature of short duration was imposed. The resulting liquid temperature distribution at the moment of boiling inception was different from that obtained with a step in heat flux.

  12. Conditions leading to a recent small hydrothermal explosion at Yellowstone National Park

    USGS Publications Warehouse

    Fournier, R.O.; Thompson, J.M.; Cunningham, C.G.; Hutchinson, R.A.

    1991-01-01

    Porkchop Geyser, in Yellowstone National Park, was the site of a small hydrothermal explosion on September 5, 1989. The geyser column suddenly rose to a height of 20-30 m, followed immediately by the explosive ejection of sinter blocks up to 1.88 m in maximum dimension and formation of an irregular crater 13.9 m long and 11.7 m wide. The ejected blocks show a variety of siliceous deposits indicative of changing environments of deposition with time, and possibly of prior hydrothermal explosive activity at this site. Water samples from Porkchop were collected and analyzed once in the 1920s, again in 1951, ten times between 1960 and mid-1989, and once in January 1990 after the explosion. It is hypothesized that a sudden breaking loose of the constriction at the exit of the geyser tube, likely triggered by a seasonal increase in subsurface boiling throughout Norris Basin, allowed water and steam to be discharged from Porkchop much more rapidly than previously. This resulted in a drop in pressure within the geyser tube, causing water in adjacent connected chambers to become superheated. An ensuing rapid flashing of superheated water to steam within relatively confined spaces resulted in the hydrothermal explosion. -after Authors

  13. Experiments and homogeneous turbulence model of boiling flowin narrow channels

    NASA Astrophysics Data System (ADS)

    Shunyu, Su; Huang, Su-Yi; Wang, Xiao-Mo

    2005-07-01

    The boiling heat transfer experiments have been carried out in vertical narrow annular channels with pure water. A two-dimensional homogeneous turbulence model of boiling flow has been developed and solved numerically to yield pressure gradient, and velocity, thermal and turbulence fields, together with local heat transfer coefficient along the length of the tube. Predictions are compared with the data of experiments and agreed well with it. The model results show that the heat transfer coefficient increases as the gap size decreases in annular channels. This model can be used to predict heat transfer of boiling flow in narrow channels.

  14. Pool and flow boiling in variable and microgravity

    NASA Technical Reports Server (NTRS)

    Merte, Herman, Jr.

    1994-01-01

    As is well known, boiling is an effective mode of heat transfer in that high heat flux levels are possible with relatively small temperature differences. Its optimal application requires that the process be adequately understood. A measure of the understanding of any physical event lies in the ability to predict its behavior in terms of the relevant parameters. Despite many years of research the predictability of boiling is currently possible only for quite specialized circumstances, e.g., the critical heat flux and film boiling for the pool boiling case, and then only with special geometries. Variable gravity down to microgravity provides the opportunity to test this understanding, but possibly more important, by changing the dimensional and time scales involved permits more detailed observations of elements involved in the boiling process, and perhaps discloses phenomena heretofore unknown. The focus here is on nucleate boiling although, as will be demonstrated below, under but certain circumstances in microgravity it can take place concurrently with the dryout process. In the presence of earth gravity or forced convection effects, the latter process is usually referred to as film boiling. However, no vapor film as such forms with pool boiling in microgravity, only dryout. Initial results are presented here for pool boiling in microgravity, and were made possible at such an early date by the availability of the Get-Away-Specials (GAS). Also presented here are some results of ground testing of a flow loop for the study of low velocity boiling, eventually to take place also in microgravity. In the interim, variable buoyancy normal to the heater surface is achieved by rotation of the entire loop relative to earth gravity. Of course, this is at the expense of varying the buoyancy parallel to the heater surface. Two questions which must be resolved early in the study of flow boiling in microgravity are (1) the lower limits of liquid flow velocity where buoyancy effects become significant to the boiling process (2) the effect of lower liquid flow velocities on the Critical Heat Flux when buoyancy is removed. Results of initial efforts in these directions are presented, albeit restricted currently to the ever present earth gravity.

  15. Pressure distribution in a converging-diverging nozzle during two-phase choked flow of subcooled nitrogen

    NASA Technical Reports Server (NTRS)

    Simoneau, R. J.

    1975-01-01

    Choked flow rates and axial pressure distributions were measured for subcooled nitrogen in a converging-diverging nozzle with a constant area section in the throat region. Stagnation pressures ranged from slightly above saturation to twice the thermodynamic critical pressure. Stagnation temperatures ranged from 0.75 to 1.03 times the thermodynamic critical temperature. The choking plane is at the divergence end of the constant area throat section. At high stagnation pressures the fluid stays liquid well into the constant area throat region; at near saturation stagnation pressures it appears that vaporization occurs at or before the entrance to the constant area throat region. The throat-to-stagnation pressure ratio data exhibits an anomalous flat region, and this anomaly is related to the two-phase process. The fluid is metastably all liquid below the saturation pressure.

  16. Characteristics of Subcooled Liquid Methane During Passage Through a Spray-Bar Joule-Thompson Thermodynamic Vent System

    NASA Technical Reports Server (NTRS)

    Hastings, L. J.; Bolshinskiy, L. G.; Hedayat, A.; Schnell, A.

    2011-01-01

    NASA s Marshall Space Flight Center (MSFC) conducted liquid methane (LCH4) testing in November 2006 using the multipurpose hydrogen test bed (MHTB) outfitted with a spray-bar thermodynamic vent system (TVS). The basic objective was to identify any unusual or unique thermodynamic characteristics associated with subcooled LCH4 that should be considered in the design of space-based TVSs. Thirteen days of testing were performed with total tank heat loads ranging from 720 W to 420 W at a fill level of approximately 90%. During an updated evaluation of the data, it was noted that as the fluid passed through the Joule Thompson expansion, thermodynamic conditions consistent with the pervasive presence of metastability were indicated. This paper describes the observed thermodynamic conditions that correspond with metastability and effects on TVS performance.

  17. Critical Current Properties of HTS Twisted Stacked-Tape Cable in Subcooled- and Pressurized-Liquid Nitrogen

    NASA Astrophysics Data System (ADS)

    Tomita, M.; Suzuki, K.; Fukumoto, Y.; Ishihara, A.; Akasaka, T.; Kobayashi, Y.; Maeda, A.; Takayasu, M.

    2015-12-01

    A 2 m length Twisted Stacked-Tape Cable (TSTC) conductor which was fabricated by 32-YBCO-tapes (4 mm width) with a 200 mm twist pitch was investigated at various temperatures near 77 K in subcooled- and pressurized-liquid nitrogen. The critical current of the TSTC cable which was 1.45 kA at 77 K measured from 64 K to 85 K by controlling the equilibrium vapor pressure of nitrogen bath and were varied from 3.65 kA at 64 K to 0.42 kA at 85 K. The temperature dependence of cables’ critical current agrees with that of the 4 mm width YBCO tape. These results are encouraging for applications of a compact Twisted Stacked-Tape Cable application in railway systems.

  18. Hydrothermal Solute Flux from Ebeko Volcanic Center, Paramushir, Kuril Islands

    NASA Astrophysics Data System (ADS)

    Taran, Y.; Kalacheva, E.; Kotenko, T.; Chaplygin, I.

    2014-12-01

    Ebeko volcano on the northern part of Paramushir Island, Northern Kurils, is characterized by frequent phreatic eruptions, a strong low-temperature fumarolic activity at the summit and was the object of comprehensive volcanological and geochemical studies during the last half a century. The volcanic center is composed of several Pleistocene volcanic structures aadjacent to Ebeko and hosts a hydrothermal system with a high outflow rate of hot SO4-Cl acidic water (Upper Yurieva springs) with the current maximum temperature of ~85oC, pH 1.3 and TDS ~ 10 g/L. All discharging thermal waters are drained by the Yurieva River to the Sea of Okhotsk. The hot springs have been changing in time, generally decreasing their activity from near boiling in 1960s, with TDS ~ 20 g/L and the presence of a small steaming field at the upper part of the ~ 700 m long discharging area, to a much lower discharge rate of main vents, lower temperature and the absence of the steaming ground. The spring chemistry did not react to the Ebeko volcanic activity (14 strong phreato-magmatic events during the last 60 years).The total measured outputs of chloride and sulfur from the system last time (2006-2010) were estimated on average as 730 g/s and 980 g/s, respectively, which corresponds to the equivalent fluxes of 64 t/d of HCl and 169 t/d of SO2. These values are higher than the fumarolic volatile output from Ebeko. The estimated discharge rate of hot (85oC) water from the system with ~ 3500 ppm of chloride is about 0.3 m3/s which is much higher than the thermal water discharge from El Chichon or Copahue volcano-hydrothermal systems and among the highest hot water natural outputs ever measured for a volcano-hydrothermal system. We also report the chemical composition (major and ~ 60 trace elements including REE) of water from the main hot spring vents and the Yurieva river mouth.

  19. Critical boiling phenomena observed in microgravity

    NASA Astrophysics Data System (ADS)

    Garrabos, Y.; Chabot, C.; Wunenburger, R.; Delville, J.-P.; Beysens, D.

    1999-06-01

    We report experimental observations of the critical boiling when co-existing gas and liquid phases of pure fluid are heated under weigthlessness through the critical point. We find that when the system's temperature T is being increased to the critical temperature Tc so that it's slightly out of equilibrium, the apparent contact angle becomes very large (up to 110 circ). The gas appears to "web" the solid surface. In addition, we detect large temperature gradients between the (hot) gas phase and the (cold) liquid phase in the interferometric cell. These unexpected results are robust: they are observed either under continuous heating (ramping) or stepping by positive temperature quenches, for various morphologies of the gas bubble and in different fluids (SF6 and CO2). The difference in isentropic thermal responses of gas and liquid during heating, due to the adiabatic heating by the "Piston Effect", is responsible for the temperature non-homogeneities. The vapour recoil force due to liquid evaporation, which is involved in the boiling crisis in heat exchangers, is presumably at the origin of the interface deformation. Nous rapportons les observations expérimentales obtenues en chaffant un fluide pur diphasique gaz-liquide en coexistence au cours de la traversée de son point critique en absence de pesanteur. Lorsque la température du système diphasique hors d'équilibre est augmentée vers la température critique, nous observons en transmission un angle de contact apparent de la vapeur très important (atteignant 110 circ), le gaz semblant "mouiller" la surface solide. De plus, d'importants gradients de température entre la phase gaz chaude et la phase liquide froide sont mesurés dans les cellules observées par interférométrie. Ces résultats inattendus sont observés pour un chauffage continu (rampe) et par trempe positive (échelon), pour différents rapports d'aspect du système diphasique, pour des cellules de CO2 et de SF6, démontrant ainsi une grande robustesse. Les réponses isentropiques différentes du gaz et du liquide lors du chauffage par effet piston sont certainement responsables des inhomogénéités de température. La force de recul de la vapeur due à l'évaporation pourrait être la cause dominante de la déformation de l'interface liquide-vapeur à l'approche de la température de transition.

  20. Hydrothermal upgrading of algae paste in a continuous flow reactor.

    PubMed

    Patel, Bhavish; Hellgardt, Klaus

    2015-09-01

    This investigation demonstrates the utility of a novel laboratory scale continuous plug flow reactor for fast Hydrothermal Liquefaction (HTL) of microalgae in a quartz lined chamber. Reactions were carried out between 300 and 380 °C and residence times of 0.5-4 min. Cyclohexane was used as a co-solvent to enhance extraction and prevent char formation. Highest biocrude yield of 38 wt.% was achieved at 380 °C and 30 s as well as Water Soluble Fraction containing up to 60 wt.% matter recovered. Analysis of the biocrude showed that the extent of deoxygenation and denitrogenation after HTL varied and is dependent on the reaction conditions, Fourier Transform Infrared Spectroscopy analysis showed that biocrude contains similar functional moieties with only a small difference observed at different reaction conditions. Conversely, the Simulated Distillation and Size Exclusion Chromatography data showed that harsher conditions produced marginally better biocrude with improved boiling point profile and lower molecular weight compounds, respectively which was confirmed using Gas Chromatography-Mass Spectrometry. PMID:25908412

  1. Hydrothermal surface alteration in the Copahue Geothermal Field (Argentina)

    SciTech Connect

    Mas, G.R.; Bengochea, L.; Mas, L.C.

    1996-12-31

    In the area of the Copahue Geothermal Field, there are five active geothermal manifestations, which mainly consist of fumaroles, hot springs and mud pots. Four of these manifestations are located in Argentina: Las Maquinas, Tennas de Copahue, Las Maquinitas and El Anfiteatro, and the fifth on the Chilean side: Chancho Co. All of them present a strong acid sulfate country rock alteration, characterized by the assemblage alunite + kaolinite + quartz + cristobalite + pyrite + sulfur + jarosite, as the result of the base leaching by fluids concentrated in H{sub 2}SO{sub 4}, by atmospheric oxidation at the water table in a steam heated environment of H{sub 2}S released by deeper boiling fluids. Another alteration zone in this area, called COP-2, is a fossil geothermal manifestation which shows characteristics of neutral to alkaline alteration represented mainly by the siliceous sinter superimposed over the acid alteration. The mineralogy and zoning of these alteration zones, and their relation with the hydrothermal solutions and the major structures of the area are analyzed.

  2. Whole Algae Hydrothermal Liquefaction Technology Pathway

    SciTech Connect

    Biddy, M.; Davis, R.; Jones, S.

    2013-03-01

    This technology pathway case investigates the feasibility of using whole wet microalgae as a feedstock for conversion via hydrothermal liquefaction. Technical barriers and key research needs have been assessed in order for the hydrothermal liquefaction of microalgae to be competitive with petroleum-derived gasoline-, diesel-, and jet-range hydrocarbon blendstocks.

  3. An Analytical Approach for Relating Boiling Points of Monofunctional Organic Compounds to Intermolecular Forces

    ERIC Educational Resources Information Center

    Struyf, Jef

    2011-01-01

    The boiling point of a monofunctional organic compound is expressed as the sum of two parts: a contribution to the boiling point due to the R group and a contribution due to the functional group. The boiling point in absolute temperature of the corresponding RH hydrocarbon is chosen for the contribution to the boiling point of the R group and is a…

  4. An Analytical Approach for Relating Boiling Points of Monofunctional Organic Compounds to Intermolecular Forces

    ERIC Educational Resources Information Center

    Struyf, Jef

    2011-01-01

    The boiling point of a monofunctional organic compound is expressed as the sum of two parts: a contribution to the boiling point due to the R group and a contribution due to the functional group. The boiling point in absolute temperature of the corresponding RH hydrocarbon is chosen for the contribution to the boiling point of the R group and is a

  5. BOILING HOUSE, GROUND FLOOR. WAREHOUSE TO LEFT REAR, MASSECUITTE HEATERS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, GROUND FLOOR. WAREHOUSE TO LEFT REAR, MASSECUITTE HEATERS ABOVE RIGHT, LOW GRADE CENTRIFUGALS BELOW. CRYSTALLIZER HOT WATER TANK TO REAR. VIEW FROM NORTHEAST - Lihue Plantation Company, Sugar Mill Building, Haleko Road, Lihue, Kauai County, HI

  6. BOILING HOUSE, INTERIOR, SECOND FLOOR, SYRUP TANKS IN RIGHT FOREGROUND, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, INTERIOR, SECOND FLOOR, SYRUP TANKS IN RIGHT FOREGROUND, HIGH GRADE VACUUM PANS BEYOND THE SYRUP TANKS. VIEW FROM THE SOUTH - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

  7. BOILING HOUSE, GROUND FLOOR, ABANDONED SUGAR BIN IN CENTER. IN ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, GROUND FLOOR, ABANDONED SUGAR BIN IN CENTER. IN BACKGROUND, THE ELEVATOR AND STAIRS GOING UP. VIEW FROM SOUTHWEST - Lihue Plantation Company, Sugar Mill Building, Haleko Road, Lihue, Kauai County, HI

  8. Boiling local heat transfer enhancement in minichannels using nanofluids

    PubMed Central

    2013-01-01

    This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 μm hydraulic diameter. Experiments are conducted with pure water and silver nanoparticles suspended in water base fluid. Two small volume fractions of silver nanoparticles suspended in water are tested: 0.000237% and 0.000475%. The experimental results show that the local heat transfer coefficient, local heat flux, and local wall temperature are affected by silver nanoparticle concentration in water base fluid. In addition, different correlations established for boiling flow heat transfer in minichannels or macrochannels are evaluated. It is found that the correlation of Kandlikar and Balasubramanian is the closest to the water boiling heat transfer results. The boiling local heat transfer enhancement by adding silver nanoparticles in base fluid is not uniform along the channel flow. Better performances and highest effect of nanoparticle concentration on the heat transfer are obtained at the minichannels entrance. PMID:23506445

  9. Effect of boiling surface vibration on heat transfer

    NASA Astrophysics Data System (ADS)

    Alangar, Sathyabhama

    2016-03-01

    Experimental investigation of effect of forced vertical surface vibration on nucleate pool boiling heat transfer of saturated water at atmospheric pressure is presented in this paper. Vertical vibration was induced externally to the circular copper test surface on which boiling took place, using a vibration exciter. Frequency was varied in the range 0-25 Hz and amplitude of vibration was varied in the range 0-5 mm. Boiling takes place at much lower superheats for the same heat flux, slope of boiling curve decreases remarkably, when the surface is given external excitation. High frequency and high amplitude oscillations lead to more intensive heat transfer. There are some combinations of frequency and vibration amplitude, which cause up to two times increase in heat transfer coefficients.

  10. Method for estimating boiling temperatures of crude oils

    SciTech Connect

    Jones, R.K.

    1996-08-01

    Evaporation is often the dominant mechanism for mass loss during the first few days following an oil spill. The initial boiling point of the oil and the rate at which the boiling point changes as the oil evaporates are needed to initialize some computer models used in spill response. The lack of available boiling point data often limits the usefulness of these models in actual emergency situations. A new computational method was developed to estimate the temperature at which a crude oil boils as a function of the fraction evaporated using only standard distillation data, which are commonly available. This method employs established thermodynamic rules and approximations, and was designed to be used with automated spill-response models. Comparisons with measurements show a strong correlation between results obtained with this method and measured values.

  11. 20. RW Meyer Sugar Mill: 18761889. Boiling House Interior, 1878. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    20. RW Meyer Sugar Mill: 1876-1889. Boiling House Interior, 1878. View: Remains of south wall. The molasses storage pits are below the floor in the foreground. The remaining piece of floor indicates the form of the entire floor. The sorghum pan and boiling range flue slope from left to right (east to west) and permitted batches of cane juice to flow through the boiling pan by gravity. The beams, joists, truss work are built of northwest pine. The sides and floor boards are built of redwood. The boiling range flue is built of fire-brick, masonry, and portland cement. The corrugated roof appears to be a later addition, not contemporary with mill operation. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  12. Turning bubbles on and off during boiling using charged surfactants

    PubMed Central

    Cho, H. Jeremy; Mizerak, Jordan P.; Wang, Evelyn N.

    2015-01-01

    Boiling—a process that has powered industries since the steam age—is governed by bubble formation. State-of-the-art boiling surfaces often increase bubble nucleation via roughness and/or wettability modification to increase performance. However, without active in situ control of bubbles, temperature or steam generation cannot be adjusted for a given heat input. Here we report the ability to turn bubbles ‘on and off' independent of heat input during boiling both temporally and spatially via molecular manipulation of the boiling surface. As a result, we can rapidly and reversibly alter heat transfer performance up to an order of magnitude. Our experiments show that this active control is achieved by electrostatically adsorbing and desorbing charged surfactants to alter the wettability of the surface, thereby affecting nucleation. This approach can improve performance and flexibility in existing boiling technologies as well as enable emerging or unprecedented energy applications. PMID:26486275

  13. Modeling of Fragmentation of Melt Droplets Triggered by Boiling Effect

    NASA Astrophysics Data System (ADS)

    Lin, Qian; Wang, Zhe; Cao, Xuewu

    The thermal fragmentation process of melt droplets in an energetic fuel coolant interaction is investigated. Boling effect is considered to be the triggering event, during the transition of heat transfer mode from film boiling to nucleate boiling and coolant periodically contacting with the droplet surface. The vapor bubble around droplet becomes unstable and collapses toward the surface of the droplet which induces the fragmentation of melt droplets. The vapor bubble collapse is modeled by writing a momentum equation for vapor bubble dynamics, an energy equation for each region of the droplet, coolant vapor and liquid and linking each region by the appropriate boundary conditions. And then a thermal fragmentation model triggered by boiling effect is developed and verified. By using the developed model, the fragmented mass of the droplet triggered by boiling effect is calculated. The result shows that the fragmentation rate is larger than that given by hydrodynamic model.

  14. BOILING HOUSE, INTERIOR, SECOND FLOOR, CLARIFIERS, SIEP TO THE LEFT, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, INTERIOR, SECOND FLOOR, CLARIFIERS, SIEP TO THE LEFT, WITH CLARIFIER FLASH TANK ABOVE, SAMPLING STATION TO THE LEFT. VIEW FROM THE SOUTHEAST - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

  15. BOILING HOUSE, INTERIOR, SECOND FLOOR, GARVER CLARIFIER IN FOREGROUND, TOPS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    BOILING HOUSE, INTERIOR, SECOND FLOOR, GARVER CLARIFIER IN FOREGROUND, TOPS OF LONG TUBE EVAPORATORS IN BACKGROUND. VIEW FROM NORTHWEST - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

  16. Why Is NASA Boiling Fluids in Space? - Duration: 59 seconds.

    NASA Video Gallery

    Convection and buoyancy work differently in space than on Earth. Learn how NASA uses this information and applies it to everyday life. Boiling fluids in space is easier than it is on Earth. Learn m...

  17. Flow Boiling and Condensation Experiment - Duration: 21 seconds.

    NASA Video Gallery

    The Flow Boiling and Condensation Experiment is another investigation that examines the flow of a mixture of liquids and the vapors they produce when in contact with hot space system equipment. Coo...

  18. A microgravity boiling and convective condensation experiment

    NASA Technical Reports Server (NTRS)

    Kachnik, Leo; Lee, Doojeong; Best, Frederick; Faget, Nanette

    1987-01-01

    A boiling and condensing test article consisting of two straight tube boilers, one quartz and one stainless steel, and two 1.5 m long glass-in-glass heat exchangers, on 6 mm ID and one 10 mm ID, was flown on the NASA KC-135 0-G aircraft. Using water as the working fluid, the 5 kw boiler produces two phase mixtures of varying quality for mass flow rates between 0.005 and 0.1 kg/sec. The test section is instrumented at eight locations with absolute and differential pressure transducers and thermocouples. A gamma densitometer is used to measure void fraction, and high speed photography records the flow regimes. A three axis accelerometer provides aircraft acceleration data (+ or - 0.01G). Data are collected via an analog-to-digital conversion and data acquisition system. Bubbly, annular, and slug flow regimes were observed in the test section under microgravity conditions. Flow oscillations were observed for some operating conditions and the effect of the 2-G pullout prior to the 0-G period was observed by continuously recording data throughout the parabolas. A total fo 300 parabolas was flown.

  19. Optimal boiling temperature for ORC installation

    NASA Astrophysics Data System (ADS)

    Mikielewicz, Jarosław; Mikielewicz, Dariusz

    2012-09-01

    In the paper a research on cost-effective optimum design boiling temperature for Organic Rankine Cycle utilizing low-temperature heat sources is presented. The ratio of the heat exchanger area of the boiler to the power output is used as the objective function. Analytical relations for heat transfer area as well power of the cycle are formulated. Evaporation temperature and inlet temperature of the heat source medium as well its mass flow rate are varied in the optimization method. The optimization is carried out for three working fluids, i.e. R 134a, water and ethanol. The objective function (economics profitability, thermodynamic efficiency) leads to different optimal working conditions in terms of evaporating temperature. Maximum power generation in the near-critical conditions of subcritical ORC is the highest. The choice of the working fluid can greatly affect the objective function which is a measure of power plant cost. Ethanol exhibits a minimum objective function but not necessarily the maximum cycle efficiency.

  20. A microgravity boiling and convective condensation experiment

    NASA Astrophysics Data System (ADS)

    Kachnik, Leo; Lee, Doojeong; Best, Frederick; Faget, Nanette

    1987-12-01

    A boiling and condensing test article consisting of two straight tube boilers, one quartz and one stainless steel, and two 1.5 m long glass-in-glass heat exchangers, on 6 mm ID and one 10 mm ID, was flown on the NASA KC-135 0-G aircraft. Using water as the working fluid, the 5 kw boiler produces two phase mixtures of varying quality for mass flow rates between 0.005 and 0.1 kg/sec. The test section is instrumented at eight locations with absolute and differential pressure transducers and thermocouples. A gamma densitometer is used to measure void fraction, and high speed photography records the flow regimes. A three axis accelerometer provides aircraft acceleration data (+ or - 0.01G). Data are collected via an analog-to-digital conversion and data acquisition system. Bubbly, annular, and slug flow regimes were observed in the test section under microgravity conditions. Flow oscillations were observed for some operating conditions and the effect of the 2-G pullout prior to the 0-G period was observed by continuously recording data throughout the parabolas. A total fo 300 parabolas was flown.

  1. Ongoing hydrothermal activities within Enceladus.

    PubMed

    Hsu, Hsiang-Wen; Postberg, Frank; Sekine, Yasuhito; Shibuya, Takazo; Kempf, Sascha; Horányi, Mihály; Juhász, Antal; Altobelli, Nicolas; Suzuki, Katsuhiko; Masaki, Yuka; Kuwatani, Tatsu; Tachibana, Shogo; Sirono, Sin-iti; Moragas-Klostermeyer, Georg; Srama, Ralf

    2015-03-12

    Detection of sodium-salt-rich ice grains emitted from the plume of the Saturnian moon Enceladus suggests that the grains formed as frozen droplets from a liquid water reservoir that is, or has been, in contact with rock. Gravitational field measurements suggest a regional south polar subsurface ocean of about 10 kilometres thickness located beneath an ice crust 30 to 40 kilometres thick. These findings imply rock-water interactions in regions surrounding the core of Enceladus. The resulting chemical 'footprints' are expected to be preserved in the liquid and subsequently transported upwards to the near-surface plume sources, where they eventually would be ejected and could be measured by a spacecraft. Here we report an analysis of silicon-rich, nanometre-sized dust particles (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn. We interpret these grains as nanometre-sized SiO2 (silica) particles, initially embedded in icy grains emitted from Enceladus' subsurface waters and released by sputter erosion in Saturn's E ring. The composition and the limited size range (2 to 8 nanometres in radius) of stream particles indicate ongoing high-temperature (>90 °C) hydrothermal reactions associated with global-scale geothermal activity that quickly transports hydrothermal products from the ocean floor at a depth of at least 40 kilometres up to the plume of Enceladus. PMID:25762281

  2. Ongoing hydrothermal activities within Enceladus

    NASA Astrophysics Data System (ADS)

    Hsu, Hsiang-Wen; Postberg, Frank; Sekine, Yasuhito; Shibuya, Takazo; Kempf, Sascha; Hornyi, Mihly; Juhsz, Antal; Altobelli, Nicolas; Suzuki, Katsuhiko; Masaki, Yuka; Kuwatani, Tatsu; Tachibana, Shogo; Sirono, Sin-Iti; Moragas-Klostermeyer, Georg; Srama, Ralf

    2015-03-01

    Detection of sodium-salt-rich ice grains emitted from the plume of the Saturnian moon Enceladus suggests that the grains formed as frozen droplets from a liquid water reservoir that is, or has been, in contact with rock. Gravitational field measurements suggest a regional south polar subsurface ocean of about 10 kilometres thickness located beneath an ice crust 30 to 40 kilometres thick. These findings imply rock-water interactions in regions surrounding the core of Enceladus. The resulting chemical `footprints' are expected to be preserved in the liquid and subsequently transported upwards to the near-surface plume sources, where they eventually would be ejected and could be measured by a spacecraft. Here we report an analysis of silicon-rich, nanometre-sized dust particles (so-called stream particles) that stand out from the water-ice-dominated objects characteristic of Saturn. We interpret these grains as nanometre-sized SiO2 (silica) particles, initially embedded in icy grains emitted from Enceladus' subsurface waters and released by sputter erosion in Saturn's E ring. The composition and the limited size range (2 to 8 nanometres in radius) of stream particles indicate ongoing high-temperature (>90 C) hydrothermal reactions associated with global-scale geothermal activity that quickly transports hydrothermal products from the ocean floor at a depth of at least 40 kilometres up to the plume of Enceladus.

  3. Irreversible change of the Rotomahana-Waimangu hydrothermal system (New Zealand) as a consequence of a volcanic eruption

    SciTech Connect

    Simmons, S.F.; Keywood, M.; Keam, R.F. ); Scott, B.J. )

    1993-07-01

    The hydrology of the long-lived Rotomabana-Waimangu hydrothermal system of New Zealand was changed irreversibly by the brief 1886 Tarawera Rift basalt eruption. The nature of the pre-1886 surface thermal activity indicates that boiling conditions prevailed in the upflow zone beneath the vicinity of the then-existing shallow Lake Rotomahana. On June 10, 1886, magma erupted through this part of the system, triggering violent volcanic and hydrothermal explosions that led to the formation of new fluid conduits and a large crater that filled to form the present Lake Rotomahana. Several years after the eruption, hot springs broke out along the line of 1886 craters southwest of Lake Rotomahana. The evolution of these features has been punctuated by spectacular geysers from 1900 to 1904 and a substantial hydrothermal eruption in 1917. The main effect of the 1886 volcanic eruption on the hydrothermal system was the perturbation of pressure gradients, causing abrupt near-surface cooling followed by gradual reheating. 23 refs., 4 figs.

  4. Characteristics of slush and boiling methane and methane mixtures

    NASA Technical Reports Server (NTRS)

    Sindt, C. F.; Ludtke, P. R.

    1973-01-01

    Review of investigation results on the characteristics of slush (i.e., mixtures of liquid and solid) and boiling methane, and of binary mixtures of methane and other natural gas constituents, intended for use as fuels for high performance aircraft, rocket engines, and motor vehicles. The investigation extends to the characterization of slush prepared from pure methane and binary mixtures of methane with nitrogen, ethane, and propane, and the boiling properties of these mixtures.

  5. Taylor stability of viscous fluids with application to film boiling

    NASA Technical Reports Server (NTRS)

    Dhir, V. K.; Lienhard, J. H.

    1973-01-01

    The dispersion relation is evaluated numerically for Taylor waves in a viscous unstable interface with surface tension. The solution takes account of transverse curvature and the numerical evaluations apply to horizontal cylindrical, as well as to plane, interfaces. The result is verified with frequency and wavelength data obtained during film boiling on horizontal wires. A very general empirical correlation is given, en passant, for the vapor blanket thickness during film boiling.

  6. 16. RW Meyer Sugar Mill: 18761889. Boiling House Interior, 1878. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    16. RW Meyer Sugar Mill: 1876-1889. Boiling House Interior, 1878. View: Looking from west to east through boiling house. The sorghum pan is on the right. The beams; joists, and trusses are of northwest pine; side boards are of redwood. A foundation line of a loading dock and smokestack are in the foreground. Both end walls have deteriorated completely. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  7. Study of He II boiling flow field around a heater

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Takada, S.; Nozawa, M.

    2015-12-01

    We studied boiling phenomena in He II based on the flow velocity measurement data by using a PIV (Particle Image Velocimeter). Noisy and silent film boiling modes together with non-boiling state were generated on/around a horizontal planar or a cylindrical heater. For PIV tracer particles, we used H2-D2 solid particles that were neutrally buoyant in He II. Video images showing the development and collapse of vapour bubble or film and the motions of tracer particles were PIV-analysed. We found the PIV velocity field was composed of AC and DC velocity components of the normal fluid. The AC component follows the dynamic behaviour of vapour, and the DC results primarily from the thermal counter flow and secondarily is induced by the asymmetric vapour bubble motion. We also investigated unsteady velocity component. The objective of this series of study is to compare the characteristic features of the flow field of He II film boiling states and peculiar He I boiling state in He II and to make clear the difference in the heat transfer performance of each boiling mode.

  8. Infrared thermometry study of nanofluid pool boiling phenomena

    PubMed Central

    2011-01-01

    Infrared thermometry was used to obtain first-of-a-kind, time- and space-resolved data for pool boiling phenomena in water-based nanofluids with diamond and silica nanoparticles at low concentration (<0.1 vol.%). In addition to macroscopic parameters like the average heat transfer coefficient and critical heat flux [CHF] value, more fundamental parameters such as the bubble departure diameter and frequency, growth and wait times, and nucleation site density [NSD] were directly measured for a thin, resistively heated, indium-tin-oxide surface deposited onto a sapphire substrate. Consistent with other nanofluid studies, the nanoparticles caused deterioration in the nucleate boiling heat transfer (by as much as 50%) and an increase in the CHF (by as much as 100%). The bubble departure frequency and NSD were found to be lower in nanofluids compared with water for the same wall superheat. Furthermore, it was found that a porous layer of nanoparticles built up on the heater surface during nucleate boiling, which improved surface wettability compared with the water-boiled surfaces. Using the prevalent nucleate boiling models, it was possible to correlate this improved surface wettability to the experimentally observed reductions in the bubble departure frequency, NSD, and ultimately to the deterioration in the nucleate boiling heat transfer and the CHF enhancement. PMID:21711754

  9. Hydrothermal synthesis, structural determination, and property characterization of transition metal sulfosalts and phosphates

    NASA Astrophysics Data System (ADS)

    Korzenski, Michael Burt

    Supercritical fluids are fascinating media for the synthesis of inorganic compounds. This is due in part to the tremendous versatility of these fluids, especially in providing access to unusual and kinetically stabilized solid phases. It is well understood that the ideal critical point of a solvent in a real solution has little meaning, and a gradual onset of critical properties with increasing temperature is normally observed, rather than a dramatic change in behavior at the magic critical point. In aqueous phases, the term hydrothermal is used for any reaction done in water above it sea level boiling point of 100°C while any reactions done above the critical point of 374°C are said to be supercritical. Hydrothermal synthesis has been used extensively over the past 150 years for the growth of large, high quality, single crystals of many known compounds, and has attained considerable significance over the last 50 years in industry for the growth of electronically important materials such as alpha-quartz and potassium titanyl phosphate (KTP). However, over the past two decades, many chemists have exploited the extraordinary solvating power of hydrothermal fluids for preparative inorganic synthesis, particularly for the preparation of zeolite-type materials. Much of this work was undertaken in the temperature range of 115 to 250°C, and thus work near the supercritical parameters of water (Tc = 374°C Pc = 221 bar) has been largely ignored due to the technological demands of aqueous systems at elevated temperatures and pressures. Therefore, we have decided to explore hydrothermal routes to both novel and known solid-state compounds which possess interesting physical properties. We have chosen to investigate a class of chalcopnictides and phosphates because of their structural diversity which promotes the preparation of chains, sheets and three-dimensional networks.

  10. Dynamics of the Yellowstone hydrothermal system

    USGS Publications Warehouse

    Hurwitz, Shaul; Lowenstern, Jacob B.

    2014-01-01

    The Yellowstone Plateau Volcanic Field is characterized by extensive seismicity, episodes of uplift and subsidence, and a hydrothermal system that comprises more than 10,000 thermal features, including geysers, fumaroles, mud pots, thermal springs, and hydrothermal explosion craters. The diverse chemical and isotopic compositions of waters and gases derive from mantle, crustal, and meteoric sources and extensive water-gas-rock interaction at variable pressures and temperatures. The thermal features are host to all domains of life that utilize diverse inorganic sources of energy for metabolism. The unique and exceptional features of the hydrothermal system have attracted numerous researchers to Yellowstone beginning with the Washburn and Hayden expeditions in the 1870s. Since a seminal review published a quarter of a century ago, research in many fields has greatly advanced our understanding of the many coupled processes operating in and on the hydrothermal system. Specific advances include more refined geophysical images of the magmatic system, better constraints on the time scale of magmatic processes, characterization of fluid sources and water-rock interactions, quantitative estimates of heat and magmatic volatile fluxes, discovering and quantifying the role of thermophile microorganisms in the geochemical cycle, defining the chronology of hydrothermal explosions and their relation to glacial cycles, defining possible links between hydrothermal activity, deformation, and seismicity; quantifying geyser dynamics; and the discovery of extensive hydrothermal activity in Yellowstone Lake. Discussion of these many advances forms the basis of this review.

  11. Dynamics of the Yellowstone hydrothermal system

    NASA Astrophysics Data System (ADS)

    Hurwitz, Shaul; Lowenstern, Jacob B.

    2014-09-01

    The Yellowstone Plateau Volcanic Field is characterized by extensive seismicity, episodes of uplift and subsidence, and a hydrothermal system that comprises more than 10,000 thermal features, including geysers, fumaroles, mud pots, thermal springs, and hydrothermal explosion craters. The diverse chemical and isotopic compositions of waters and gases derive from mantle, crustal, and meteoric sources and extensive water-gas-rock interaction at variable pressures and temperatures. The thermal features are host to all domains of life that utilize diverse inorganic sources of energy for metabolism. The unique and exceptional features of the hydrothermal system have attracted numerous researchers to Yellowstone beginning with the Washburn and Hayden expeditions in the 1870s. Since a seminal review published a quarter of a century ago, research in many fields has greatly advanced our understanding of the many coupled processes operating in and on the hydrothermal system. Specific advances include more refined geophysical images of the magmatic system, better constraints on the time scale of magmatic processes, characterization of fluid sources and water-rock interactions, quantitative estimates of heat and magmatic volatile fluxes, discovering and quantifying the role of thermophile microorganisms in the geochemical cycle, defining the chronology of hydrothermal explosions and their relation to glacial cycles, defining possible links between hydrothermal activity, deformation, and seismicity; quantifying geyser dynamics; and the discovery of extensive hydrothermal activity in Yellowstone Lake. Discussion of these many advances forms the basis of this review.

  12. Hydrothermal carbonization of lignocellulosic biomass.

    PubMed

    Xiao, Ling-Ping; Shi, Zheng-Jun; Xu, Feng; Sun, Run-Cang

    2012-08-01

    Hydrothermal carbonization (HTC) is a novel thermochemical conversion process to convert lignocellulosic biomass into value-added products. HTC processes were studied using two different biomass feedstocks: corn stalk and Tamarix ramosissima. The treatment brought an increase of the higher heating values up to 29.2 and 28.4 MJ/kg for corn stalk and T. ramosissima, respectively, corresponding to an increase of 66.8% and 58.3% as compared to those for the raw materials. The resulting lignite-like solid products contained mainly lignin with a high degree of aromatization and a large amount of oxygen-containing groups. Liquid products extracted with ethyl acetate were analyzed by gas chromatography-mass spectrometry. The identified degradation products were phenolic compounds and furan derivatives, which may be desirable feedstocks for biodiesel and chemical production. Based on these results, HTC is considered to be a potential treatment in a lignocellulosic biomass refinery. PMID:22698445

  13. Hyperbaric Hydrothermal Atomic Force Microscope

    DOEpatents

    Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

    2003-07-01

    A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

  14. Hyperbaric hydrothermal atomic force microscope

    DOEpatents

    Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

    2002-01-01

    A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

  15. Catalytic Hydrothermal Gasification of Biomass

    SciTech Connect

    Elliott, Douglas C.

    2008-05-06

    A recent development in biomass gasification is the use of a pressurized water processing environment in order that drying of the biomass can be avoided. This paper reviews the research undertaken developing this new option for biomass gasification. This review does not cover wet oxidation or near-atmospheric-pressure steam-gasification of biomass. Laboratory research on hydrothermal gasification of biomass focusing on the use of catalysts is reviewed here, and a companion review focuses on non-catalytic processing. Research includes liquid-phase, sub-critical processing as well as super-critical water processing. The use of heterogeneous catalysts in such a system allows effective operation at lower temperatures, and the issues around the use of catalysts are presented. This review attempts to show the potential of this new processing concept by comparing the various options under development and the results of the research.

  16. Hydrothermal Occurrences in Gusev Crater

    NASA Astrophysics Data System (ADS)

    Ruff, S. W.; Farmer, J. D.; Milliken, R.; Mills, V. W.; Shock, E.

    2011-12-01

    Exploration of the Gusev crater landing site by the Spirit rover has revealed for the first time, in situ evidence of hydrothermal activity on Mars. Most compelling are eroded outcrops of opaline silica found adjacent to "Home Plate" [1], an eroded stack of volcaniclastic deposits stratigraphically overlain by a vesicular basalt unit [2]. Recent work [3] demonstrates that the silica outcrops occur in a stratiform unit that possibly surrounds Home Plate. The outcrops are dominated by opal-A with no evidence for diagenesis to other silica phases. No other hydrous or alteration phases have been identified within the outcrops; most notable is a lack of sulfur phases. The outcrops have porous and in some cases, brecciated microtextures. Taken together, these observations support the interpretation that the opaline silica outcrops were produced in a hot spring or perhaps geyser environment. In this context, they are silica sinter deposits precipitated from silica-rich hydrothermal fluids, possibly related to the volcanism that produced the Home Plate volcanic rocks. On Earth, debris aprons in which sinter is brecciated, reworked, and cemented, are common features of hot springs and geysers and are good analogs for the Martian deposits. An alternative hypothesis is that the silica resulted from acid-sulfate leaching of precursor rocks by fumarolic steam condensates. But stratigraphic, textural, and chemical observations tend to diminish this possibility [3]. We are conducting extensive laboratory and field investigations of silica from both hot spring/geyser and fumarole environments to understand the full range of mineralogical, chemical, textural, and morphological variations that accompany its production, in order to shed more light on the Home Plate occurrence. The recent discovery of abundant Mg-Fe carbonate (16-34 wt%) in outcrops named Comanche provides possible evidence for additional hydrothermal activity in Gusev [4]. However, the carbonate is hosted by olivine-rich (~40 wt%) volcaniclastic rocks that show no other phases indicative of significant alteration, such as phyllosilicates. Even the presence of so much olivine in the outcrops attests to minimal alteration. This suggests that the carbonate was not derived from hydrothermal alteration of the local rock. Instead, carbonate-bearing solutions sourced from elsewhere in the region may have precipitated carbonate as cement within the olivine-rich host rock [4]. An alternative hypothesis by [5] suggests that Comanche carbonate resulted from direct precipitation of evaporating brine, perhaps related to the putative ancient lake in Gusev crater, which infiltrated the host rock. In either case, the presence of outcrops of abundant carbonate and opaline silica demonstrates a rich and varied aqueous history in Gusev crater. [1] Squyres, S. W., et al. (2008), Science, 320, 1063-1067. [2] Squyres, S. W., et al. (2007), Science, 316, 738-742. [3] Ruff, S. W., et al. (2011), J. Geophys. Res., 116, E00F23, 10.1029/2010JE003767. [4] Morris, R. V., et al. (2010), Science, 329, 5990, 421-424, 10.1126/science.1189667. [5] Ruff, S. W. (2011), Lunar Planet. Sci., XLII, abstract #2708.

  17. Boiling and vertical mineralization zoning: a case study from the Apacheta low-sulfidation epithermal gold-silver deposit, southern Peru

    NASA Astrophysics Data System (ADS)

    André-Mayer, Anne-Sylvie; Leroy, Jacques; Bailly, Laurent; Chauvet, Alain; Marcoux, Eric; Grancea, Luminita; Llosa, Fernando; Rosas, Juan

    2002-06-01

    The Au-Ag (±Pb-Zn) Apacheta deposit is located in the Shila district, 600 km southeast of Lima in the Cordillera Occidental of Arequipa Province, southern Peru. The vein mineralization is found in Early to Middle Miocene calc-alkaline lava flows and volcanic breccias. Both gangue and sulfide mineralization express a typical low-sulfidation system; assay data show element zoning with base metals enriched at depth and higher concentrations of precious metals in the upper part of the veins. Three main deposition stages are observed: (1) early pyrite and base-metal sulfides with minor electrum 1 and acanthite; (2) brecciation of this mineral assemblage and cross-cutting veinlets with subhedral quartz crystals, Mn-bearing calcite and rhombic adularia crystals; and finally (3) veinlets and geodal filling of an assemblage of tennantite/tetrahedrite + colorless sphalerite 2 + galena + chalcopyrite + electrum 2. Fluid inclusions in the mineralized veins display two distinct types: aqueous-carbonic liquid-rich Lw-c inclusions, and aqueous-carbonic vapor-rich Vw-c inclusions. Microthermometric data indicate that the ore minerals were deposited between 300 and 225 °C from relatively dilute hydrothermal fluids (0.6-3.4 wt% NaCl). The physical and chemical characteristics of the hydrothermal fluids show a vertical evolution, with in particular a drop in temperature and a loss of H2S. The presence of adularia and platy calcite and of co-existing liquid-rich and vapor-rich inclusions in the ore-stage indicates a boiling event. Strong H2S enrichment in the Vw-c inclusions observed at -200 m, the abundance of platy calcite, and the occurrence of hydrothermal breccia at this level may indicate a zone of intense boiling. The vertical element zoning observed in the Apacheta deposit thus seems to be directly related to the vertical evolution of hydrothermal-fluid characteristics. Precious-metal deposition mainly occurred above the 200-m level below the present-day surface, in response to a liquid/vapor phase separation due to an upward boiling front.

  18. Hydrothermal Synthesis of Loessial Mesoporous Materials

    NASA Astrophysics Data System (ADS)

    Lu, L.; Jing, Z.; Wang, Z.; Pan, X.; Ishida, E. H.

    2010-11-01

    In order to sustain the inherent porous properties of loess, hydrothermal synthesis of mesoporous materials from loess was carried out under saturated steam pressure at 100-200 °C for up to 24h. The experimental results showed that the curing temperature and time exerted a positive influence on the strength development, which was believed to be due to tobermorite formation. Moreover, during the hydrothermal process, a huge number of new mesopores could be formed within the matrix. Therefore a tough and mesoporous material could be produced from loess hydrothermally, which is expected to provide a good humidity regulating property.

  19. Relationships between lava types, seafloor morphology, and the occurrence of hydrothermal venting in the ASHES vent field of Axial Volcano. [Axial Seamount Hydrothermal Emission Study

    SciTech Connect

    Hammond, S.R. )

    1990-08-10

    Deep-towed and submersible photographic surveys within the caldera of Axial Volcano have been integrated with high-resolution bathmetry to produce a geological map of the most active vent field in the caldera. Locations for over 2,000 photographs in and near the vent field were determined using a seafloor transponder network. Then each photograph was described utilizing a classification system which provides detailed information concerning lava type, hydrothermal activity, sediment cover, geological structure, and biology. Resulting data were entered into a digital data base, and computer-generated maps were created that portray spatial relationships between selected geological variables. In general, the entire ASHES field is characterized by pervasive low-temperature venting. The most vigorous venting is concentrated in an approximately 80 m {times} 80 m area where there are several high-temperature vents including some which are producing high-temperature vapor-phase fluids derived from a boiling hydrothermal system. Lava types within the ASHES vent field are grouped into three distinct morphologies: (1) smooth (flat-surfaced, ropy, and whorled) sheet flows, (2) lobate flows, and (3) jumbled-sheet flows. The most intense hydrothermal venting is concentrated in the smooth sheet flows and the lobate flows. The location of the ASHES field is mainly attributable to faulting which defines the southwest caldera wall, but the concentration of intense venting appears to be related also to the spatial distribution of lava types in the vent field and their contrasting permeabilities. Other structural trends of faults and fissures within the field also influence the location of individual events.

  20. Thermo-chemical variations of the hydrothermal fluids in the Berlin geothermal field (El Salvador)

    NASA Astrophysics Data System (ADS)

    Ruggieri, G.; Dallai, L.; Nardini, I.; Torio Henriquez, E.

    2009-04-01

    The liquid-dominated Berlin geothermal field is located about 110 km ESE of San Salvador, on the northern slope of the Berlin-Tecapa volcanic complex. The geothermal reservoir occurs within andesitic to basaltic lavas and tuffs. Measured temperatures in the production zones are in the 280-300˚ C range, while in the reinjection zones are 245-250˚ C. The reservoir fluids are NaCl waters with total dissolved solids of about 6000-10000 mg/kg and CO2 partial pressures of 0.049-0.460 MPa. A recent exploration project has been carried out by Enel GreenPower and LaGeo at the southern part of the field. A fluid inclusion studies have been carried out on core-samples from the recently explored area and from the production zone in order to obtain information on the thermo-chemical evolution of the geothermal fluids. In addition, isotopic data on hydrothermal epidote allowed to better constrain the sources of the water that circulated in the geothermal reservoir. The examined samples are mainly composed of volcanic rocks and breccias affected by hydrothermal alteration. The secondary minerals (mostly epidote, chlorite, quartz, adularia, albite, prehnite, calcite) occur either as replacement of primary minerals or within micro-fracture and voids. Fluid inclusions microthermometry has been performed on fluid inclusions found in hydrothermal and igneous quartz, albite, adularia, calcite, anhydrite and prehnite. Most of the observed inclusions are aqueous, two-phase liquid-rich inclusions; rare vapor-rich inclusions also occur in some samples. Fluid inclusion homogenization temperatures range is 191-344˚ C; the inclusions with the highest homogenization values at each sampling depths were trapped at or close to boiling condition. A cooling process is recorded by the wide ranges of homogenization temperatures and is also evidenced by the comparison of present-day temperature at the sampling depths and fluid inclusion homogenization temperatures. In particular, a significant temperature decrease (up to 100˚ C) occurred from the trapping of hottest fluid in the recently explored area to present-day condition at depths > 1.5 km below the ground level. Apparent salinities of many fluid inclusions are comparable to those of present-day fluids; however there are also fluid inclusions showing higher and lower salinities than present-day fluids. Low values of apparent salinity (down to 0.2 wt. % NaCl equiv.) can be related to the circulation of liquid water formed from steam condensation and/or in part to a decrease of the CO2 content in the geothermal fluid due to boiling processes. Whereas, the occurrence of inclusions in deep samples showing significantly high salinities (up to 21.2 wt.% NaCl equiv.) can be related to two processes: 1) open system fluid boiling with steam lost, or 2) injection of a high-salinity fluid in the system. The relatively high ^D values (up to -42 per mil) of the H2O in equilibrium with epidote is coherent with the sporadic input of saline fluids of magmatic derivation that mixed with geothermal fluid of meteoric origin in the deep part of the hydrothermal system. On the other hand, prolonged open system boiling processes at the temperatures indicated by fluid inclusions are not compatible with these isotopic values.

  1. Density measurements of subcooled water in the temperature range of (243 and 283) K and for pressures up to 400 MPa.

    PubMed

    Romeo, Raffaella; Giuliano Albo, P Alberto; Lorefice, Salvatore; Lago, Simona

    2016-02-21

    In this work, accurate density measurements of subcooled water (freshly double-distilled water) were performed along eight constant-mass curves in the temperature range of (243 to 283) K and in the pressure range of (140 to 400) MPa, by a pseudo-isochoric method. The experimental apparatus mainly consisted of a high pressure vessel, especially designed for this experiment, of known volume as a function of temperature and pressure, used to perform measurements in the T-p range under study. The density of subcooled water was obtained by measuring the equilibrium pressure at different temperatures, keeping the mass constant. All terms contributing to the uncertainty of subcooled water density measurements were considered; the estimated relative uncertainty, in the investigated temperature and pressure range, is about 0.07%. The experimental results were compared with the literature densities. In particular, the trend of density versus temperature for a constant mass of sample observed experimentally differs from the trend calculated by the equation provided by the International Association for Properties of Water and Steam (IAPWS-95) outside the range of validity, i.e., in the metastable region. PMID:26896989

  2. Development of cooling system for 66/6.9kV-20MVA REBCO superconducting transformers with Ne turbo-Brayton refrigerator and subcooled liquid nitrogen

    NASA Astrophysics Data System (ADS)

    Iwakuma, M.; Adachi, K.; Yun, K.; Yoshida, K.; Sato, S.; Suzuki, Y.; Umeno, T.; Konno, M.; Hayashi, H.; Eguchi, T.; Izumi, T.; Shiohara, Y.

    2015-12-01

    We developed a turbo-Brayton refrigerator with Ne gas as a working fluid for a 3 ϕ- 66/6.9kV-2MVA superconducting transformer with coated conductors which was bath-cooled with subcooled LN2. The two-stage compressor and expansion turbine had non-contact magnetic bearings for a long maintenance interval. In the future, we intend to directly install a heat exchanger into the Glass-Fiber-Reinforced-Plastics cryostat of a transformer and make a heat exchange between the working fluid gas and subcooled LN2. In this paper we investigate the behaviour of subcooled LN2 in a test cryostat, in which heater coils were arranged side by side with a flat plate finned-tube heat exchanger. Here a He turbo-Brayton refrigerator was used as a substitute for a Ne turbo-Brayton one. The pressure at the surface of LN2 in the cryostat was one atmosphere. Just under the LN2 surface, a stationary layer of LN2 was created over the depth of 20 cm and temperature dropped from 77 K to 65 K with depth while, in the lower level than that, a natural convection flow of LN2 was formed and temperature was almost uniform over 1 m depth. The boundary plane between the stationary layer and the natural convection region was visible.

  3. Density measurements of subcooled water in the temperature range of (243 and 283) K and for pressures up to 400 MPa

    NASA Astrophysics Data System (ADS)

    Romeo, Raffaella; Giuliano Albo, P. Alberto; Lorefice, Salvatore; Lago, Simona

    2016-02-01

    In this work, accurate density measurements of subcooled water (freshly double-distilled water) were performed along eight constant-mass curves in the temperature range of (243 to 283) K and in the pressure range of (140 to 400) MPa, by a pseudo-isochoric method. The experimental apparatus mainly consisted of a high pressure vessel, especially designed for this experiment, of known volume as a function of temperature and pressure, used to perform measurements in the T-p range under study. The density of subcooled water was obtained by measuring the equilibrium pressure at different temperatures, keeping the mass constant. All terms contributing to the uncertainty of subcooled water density measurements were considered; the estimated relative uncertainty, in the investigated temperature and pressure range, is about 0.07%. The experimental results were compared with the literature densities. In particular, the trend of density versus temperature for a constant mass of sample observed experimentally differs from the trend calculated by the equation provided by the International Association for Properties of Water and Steam (IAPWS-95) outside the range of validity, i.e., in the metastable region.

  4. Hydrothermal disturbances at the Norris Geyser Basin, Yellowstone National Park (USA) in 2003

    NASA Astrophysics Data System (ADS)

    Lowenstern, J. B.; Heasler, H.; Smith, R. B.

    2003-12-01

    The Norris Geyser Basin in north-central Yellowstone National Park (YNP) experienced a series of notable changes during 2003, including formation of new hot springs and fumaroles, renewed activity of dormant geysers and elevated ground temperatures. This abstract provides a short synopsis of the new hydrothermal activity. In 2000, Yellowstone's tallest geyser, Steamboat, erupted after a dormant period of nearly 9 years. It erupted twice in 2002 and then again on 26 March and 27 April 2003. Surges in flux of thermal water preceding the eruptions (preplay) were recorded by a couplet of temperature data loggers placed in the outlet stream. The data indicated pulses of water flow with 1 and ~3 day intervals. On 10 July 2003, a new thermal feature was reported just west of Nymph Lake, ~ 3.5 km northwest of the Norris Museum. A linear series of vigorous fumaroles, about 75 m long had formed in a forested area, ~ 200 m up a hill on the lake's west shore. Fine particles of rock and mineral fragments coated nearby vegetation. Fumarole temperatures were around the local boiling temperature of water (92° C). After two months, somewhat reduced steam emission was accompanied by discharge of ~ 3-10 gallons per minute of near-neutral thermal water. Trees within 4 meters of the lineament were dead and were being slowly combusted. Porkchop Geyser in Norris' Back Basin had been dormant since it exploded in 1989, littering the nearby area with boulders up to over 1 m in diameter. Since that time, its water had remained well below the boiling temperature of water. From 1 April through 1 July `03, the temperature of waters in Porkchop's vent increased continuously from 67° to 88° C. Each Summer, Norris' Back Basin experiences an "annual disturbance" where individual hot springs and geysers typically show anomalous boiling, and have measurable increases in turbidity, acidity and SO4/Cl ratios. The disturbance has been linked to depressurization of the hydrothermal system as the hydrostatic pressure of the snowmelt-fed groundwater table wanes each summer. This year, the "Norris disturbance" is estimated to have begun on 11 July 2003,when pronounced changes were noted, including thermal pools that were boiled to dryness (e.g., Pearl Geyser), creating fumaroles. Porkchop Geyser erupted for the first time since 1989 on 16 July. New mud pots formed along the Back Basin Trail and increased ground temperatures were noted over an 500 x 300 m area. Park staff noted temperatures up to 94° C at 1 cm beneath the ground surface in areas that were previously cool. Vegetation in the area immediately died and began to break down due to the high temperatures. Yellowstone National Park closed the Back Basin Trail to all visitor travel on 22 July 2003. During the first week of August 2003, the Yellowstone Volcano Observatory installed a temporary monitoring network in the Norris Geyser Basin. University of Utah staff, with equipment and personnel made available by IRIS, UNAVCO, USGS and YNP, installed seven broadband seismometers and five continuous GPS receivers. In addition, YNP deployed a series of temperature data-loggers to record changes in flow from thermal features within the Norris Back Basin. The network is intended to identify ground motions associated with fluid flow within the geyser basin that may accompany eruptions of geysers, boiling episodes or events precursory to hydrothermal explosions. The monitoring network will remain operational for between four and twelve weeks.

  5. Enhanced boiling heat transfer in horizontal test bundles

    SciTech Connect

    Trewin, R.R.; Jensen, M.K.; Bergles, A.E.

    1994-08-01

    Two-phase flow boiling from bundles of horizontal tubes with smooth and enhanced surfaces has been investigated. Experiments were conducted in pure refrigerant R-113, pure R-11, and mixtures of R-11 and R-113 of approximately 25, 50, and 75% of R-113 by mass. Tests were conducted in two staggered tube bundles consisting of fifteen rows and five columns laid out in equilateral triangular arrays with pitch-to-diameter ratios of 1.17 and 1.5. The enhanced surfaces tested included a knurled surface (Wolverine`s Turbo-B) and a porous surface (Linde`s High Flux). Pool boiling tests were conducted for each surface so that reference values of the heat transfer coefficient could be obtained. Boiling heat transfer experiments in the tube bundles were conducted at pressures of 2 and 6 bar, heat flux values from 5 to 80 kW/m{sup 2}s, and qualities from 0% to 80%, Values of the heat transfer coefficients for the enhanced surfaces were significantly larger than for the smooth tubes and were comparable to the values obtained in pool boiling. It was found that the performance of the enhanced tubes could be predicted using the pool boiling results. The degradation in the smooth tube heat transfer coefficients obtained in fluid mixtures was found to depend on the difference between the molar concentration in the liquid and vapor.

  6. Gravity and Heater Size Effects on Pool Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; Raj, Rishi

    2014-01-01

    The current work is based on observations of boiling heat transfer over a continuous range of gravity levels between 0g to 1.8g and varying heater sizes with a fluorinert as the test liquid (FC-72/n-perfluorohexane). Variable gravity pool boiling heat transfer measurements over a wide range of gravity levels were made during parabolic flight campaigns as well as onboard the International Space Station. For large heaters and-or higher gravity conditions, buoyancy dominated boiling and heat transfer results were heater size independent. The power law coefficient for gravity in the heat transfer equation was found to be a function of wall temperature under these conditions. Under low gravity conditions and-or for smaller heaters, surface tension forces dominated and heat transfer results were heater size dependent. A pool boiling regime map differentiating buoyancy and surface tension dominated regimes was developed along with a unified framework that allowed for scaling of pool boiling over a wide range of gravity levels and heater sizes. The scaling laws developed in this study are expected to allow performance quantification of phase change based technologies under variable gravity environments eventually leading to their implementation in space based applications.

  7. Magmatic intrusions and hydrothermal systems on Mars

    NASA Technical Reports Server (NTRS)

    Gulick, V. C.

    1992-01-01

    We are continuing our investigation of Martian hydrothermal systems and the formation of fluvial valleys on Mars. Here we present our initial numerical modeling results of hydrothermal systems associated with magmatic intrusions on Mars. To model such hydrothermal systems, we consider single, cylindrical intrusions of 4 km height 2 km below the surface. Our preliminary results of modeling hydrothermal systems associated with magmatic intrusions in the Martian environment suggest that such systems, if associated with intrusions of several 10(exp 2) km(exp 3) or larger, in the presence of permeable, water-rich subsurface should be able to provide adequate discharges of water over the time periods needed to form fluvial valleys. However, it is important to note that the amount of water ultimately available for erosion also depends on the surface and subsurface lithology.

  8. Droplet impingement dynamics: effect of surface temperature during boiling and non-boiling conditions

    NASA Astrophysics Data System (ADS)

    Shen, Jian; Liburdy, James A.; Pence, Deborah V.; Narayanan, Vinod

    2009-11-01

    This study investigates the hydrodynamic characteristics of droplet impingement on heated surfaces and compares the effect of surface temperature when using water and a nanofluid on a polished and nanostructured surface. Results are obtained for an impact Reynolds number and Weber number of approximately 1700 and 25, respectively. Three discs are used: polished silicon, nanostructured porous silicon and gold-coated polished silicon. Seven surface temperatures, including single-phase (non-boiling) and two-phase (boiling) conditions, are included. Droplet impact velocity, transient spreading diameter and dynamic contact angle are measured. Results of water and a water-based single-wall carbon-nanotube nanofluid impinging on a polished silicon surface are compared to determine the effects of nanoparticles on impinging dynamics. The nanofluid results in larger spreading velocities, larger spreading diameters and an increase in early-stage dynamic contact angle. Results of water impinging on both polished silicon and nanostructured silicon show that the nanostructured surface enhances the heat transfer for evaporative cooling at lower surface temperatures, which is indicated by a shorter evaporation time. Using a nanofluid or a nanostructured surface can reduce the total evaporation time up to 20% and 37%, respectively. Experimental data are compared with models that predict dynamic contact angle and non-dimensional maximum spreading diameter. Results show that the molecular-kinetic theory's dynamic contact angle model agrees well with current experimental data for later times, but over-predicts at early times. Predictions of maximum spreading diameter based on surface energy analyses indicate that these models over-predict unless empirical coefficients are adjusted to fit the test conditions. This is a consequence of underestimates of the dissipative energy for the conditions studied.

  9. Chemical environments of submarine hydrothermal systems

    NASA Technical Reports Server (NTRS)

    Shock, Everett L.

    1992-01-01

    Perhaps because black-smoker chimneys make tremendous subjects for magazine covers, the proposal that submarine hydrothermal systems were involved in the origin of life has caused many investigators to focus on the eye-catching hydrothermal vents. In much the same way that tourists rush to watch the spectacular eruptions of Old Faithful geyser with little regard for the hydrology of the Yellowstone basin, attention is focused on the spectacular, high-temperature hydrothermal vents to the near exclusion of the enormous underlying hydrothermal systems. Nevertheless, the magnitude and complexity of geologic structures, heat flow, and hydrologic parameters which characterize the geyser basins at Yellowstone also characterize submarine hydrothermal systems. However, in the submarine systems the scale can be considerably more vast. Like Old Faithful, submarine hydrothermal vents have a spectacular quality, but they are only one fascinating aspect of enormous geologic systems operating at seafloor spreading centers throughout all of the ocean basins. A critical study of the possible role of hydrothermal processes in the origin of life should include the full spectrum of probable environments. The goals of this chapter are to synthesize diverse information about the inorganic geochemistry of submarine hydrothermal systems, assemble a description of the fundamental physical and chemical attributes of these systems, and consider the implications of high-temperature, fluid-driven processes for organic synthesis. Information about submarine hydrothermal systems comes from many directions. Measurements made directly on venting fluids provide useful, but remarkably limited, clues about processes operating at depth. The oceanic crust has been drilled to approximately 2.0 km depth providing many other pieces of information, but drilling technology has not allowed the bore holes and core samples to reach the maximum depths to which aqueous fluids circulate in oceanic crust. Such determinations rely on studies of pieces of deep oceanic crust uplifted by tectonic forces such as along the Southwest Indian Ridge, or more complete sections of oceanic crust called ophiolite sequences which are presently exposed on continents owing to tectonic emplacement. Much of what is thought to happen in submarine hydrothermal systems is inferred from studies of ophiolite sequences, and especially from the better-exposed ophiolites in Oman, Cyprus and North America. The focus of much that follows is on a few general features: pressure, temperature, oxidation states, fluid composition and mineral alteration, because these features will control whether organic synthesis can occur in hydrothermal systems.

  10. Hydrothermal industrialization: direct heat development. Final report

    SciTech Connect

    Not Available

    1982-05-01

    A description of hydrothermal resources suitable for direct applications, their associated temperatures, geographic distribution and developable capacity are given. An overview of the hydrothermal direct-heat development infrastructure is presented. Development activity is highlighted by examining known and planned geothermal direct-use applications. Underlying assumptions and results for three studies conducted to determine direct-use market penetration of geothermal energy are discussed.

  11. Specific features of explosive boiling of liquids on a film microheater

    NASA Astrophysics Data System (ADS)

    Varlamov, Yu. D.; Meshcheryakov, Yu. P.; Predtechenskii, M. P.; Lezhnin, S. I.; Ul'Yankin, S. N.

    2007-03-01

    Explosive boiling of liquids on film heaters under the action of pulsed heat fluxes q = 108 109 W/m 2 is considered. A technique of stroboscopic visualization of boiling stages with a time resolution of 100 nsec is used. Numerous scenarios of evolution of explosive boiling are demonstrated. Conditions of the thermal effect (magnitude of the heat flux, duration and repetition frequency of heat pulses) are found, which ensure single and repeated boiling, intermittent boiling, and boiling with formation of complicated multi-bubble structures. It is noted that homogeneous nucleation is a dominating mechanism of incipience of examined liquids for q > 108 W/m 2.

  12. Hydrothermal mineralization along submarine rift zones, Hawaii

    USGS Publications Warehouse

    Hein, J.R.; Gibbs, A.E.; Clague, D.A.; Torresan, M.

    1996-01-01

    Describes mineralization of midplate submarine rift zones and hydrothermal manganese oxide mineralization of midplate volcanic edifices. Hydrothermal Mn oxides were recovered from submarine extensions of two Hawaiian rift zones, along Haleakala and Puna Ridges. These Mn oxides form two types of deposits, metallic stratiform layers in volcaniclastic rocks and cement for clastic rocks; both deposit types are composed of todorokite and birnessite. Unlike most other hydrothermal Mn oxide deposits, those from Hawaiian rift zones are enriched in the trace metals Zn, Co, Ba, Mo, Sr, V, and especially Ni. Metals are derived from three sources: mafic and ultramafic rocks leached by circulating hydrothermal fluids, clastic material (in Mn-cemented sandstone), and seawater that mixed with the hydrothermal fluids. Precipitation of Mn oxide below the seafloor is indicated by its occurrence as cement, growth textures that show mineralizing fluids were introduced from below, and pervasive replacement of original matrix of clastic rocks.Hydrothermal Mn oxides were recovered from submarine extensions of two Hawaiian rift zones, along Haleakala and Puna Ridges. These Mn oxides form two types of deposits, metallic stratiform layers in volcaniclastic rocks and cement for clastic rocks. Both deposit types are composed of todorokite and birnessite. This article describes in detail the specific characteristics of these Mn oxides.

  13. Pressure distribution in a converging-diverging nozzle during two-phase choked flow of subcooled nitrogen

    NASA Technical Reports Server (NTRS)

    Simoneau, R. J.

    1975-01-01

    Choked flow rates and axial pressure distributions were measured for subcooled nitrogen in a converging-diverging nozzle with a constant area section in the throat region. Stagnation pressures ranged from slightly above saturation to twice the thermodynamic critical pressure. Stagnation temperatures ranged from 0.75 to 1.03 times the thermodynamic critical temperature. The choking plane appears to be at the divergence end of the constant area throat section. At high stagnation pressures the fluid appears to stay liquid well into the constant area throat region; however, at near saturation stagnation pressures it appears that vaporization occurs at or before the entrance to the constant area throat region. The throat-to-stagnation pressure ratio data exhibits an anomalous flat region. This anomaly appears to be fundamentally related to the two-phase process and not merely to the present specific nozzle geometry. The fluid appears to be metastably all liquid below the saturation pressure. The data are compared to various flow models. No model adequately describes the whole range of the experiment.

  14. Continuous Carbon Nanotube-Ultrathin Graphite Hybrid Foams for Increased Thermal Conductivity and Suppressed Subcooling in Composite Phase Change Materials.

    PubMed

    Kholmanov, Iskandar; Kim, Jaehyun; Ou, Eric; Ruoff, Rodney S; Shi, Li

    2015-12-22

    Continuous ultrathin graphite foams (UGFs) have been actively researched recently to obtain composite materials with increased thermal conductivities. However, the large pore size of these graphitic foams has resulted in large thermal resistance values for heat conduction from inside the pore to the high thermal conductivity graphitic struts. Here, we demonstrate that the effective thermal conductivity of these UGF composites can be increased further by growing long CNT networks directly from the graphite struts of UGFs into the pore space. When erythritol, a phase change material for thermal energy storage, is used to fill the pores of UGF-CNT hybrids, the thermal conductivity of the UGF-CNT/erythritol composite was found to increase by as much as a factor of 1.8 compared to that of a UGF/erythritol composite, whereas breaking the UGF-CNT bonding in the hybrid composite resulted in a drop in the effective room-temperature thermal conductivity from about 4.1 ± 0.3 W m(-1) K(-1) to about 2.9 ± 0.2 W m(-1) K(-1) for the same UGF and CNT loadings of about 1.8 and 0.8 wt %, respectively. Moreover, we discovered that the hybrid structure strongly suppresses subcooling of erythritol due to the heterogeneous nucleation of erythritol at interfaces with the graphitic structures. PMID:26529570

  15. Geochemistry of hydrothermal fluids from the PACMANUS, Northeast Pual and Vienna Woods hydrothermal fields, Manus Basin, Papua New Guinea

    USGS Publications Warehouse

    Reeves, Eoghan P.; Seewald, Jeffrey S.; Saccocia, Peter; Bach, Wolfgang; Craddock, Paul R.; Shanks, Wayne C.; Sylva, Sean P.; Walsh, Emily; Pichler, Thomas; Rosner, Martin

    2011-01-01

    Processes controlling the composition of seafloor hydrothermal fluids in silicic back-arc or near-arc crustal settings remain poorly constrained despite growing evidence for extensive magmatic-hydrothermal activity in such environments. We conducted a survey of vent fluid compositions from two contrasting sites in the Manus back-arc basin, Papua New Guinea, to examine the influence of variations in host rock composition and magmatic inputs (both a function of arc proximity) on hydrothermal fluid chemistry. Fluid samples were collected from felsic-hosted hydrothermal vent fields located on Pual Ridge (PACMANUS and Northeast (NE) Pual) near the active New Britain Arc and a basalt-hosted vent field (Vienna Woods) located farther from the arc on the Manus Spreading Center. Vienna Woods fluids were characterized by relatively uniform endmember temperatures (273-285 degrees C) and major element compositions, low dissolved CO2 concentrations (4.4 mmol/kg) and high measured pH (4.2-4.9 at 25 degrees C). Temperatures and compositions were highly variable at PACMANUS/NE Pual and a large, newly discovered vent area (Fenway) was observed to be vigorously venting boiling (358 degrees C) fluid. All PACMANUS fluids are characterized by negative delta DH2O values, in contrast to positive values at Vienna Woods, suggesting substantial magmatic water input to circulating fluids at Pual Ridge. Low measured pH (25 degrees C) values (~2.6-2.7), high endmember CO2 (up to 274 mmol/kg) and negative delta 34SH2S values (down to -2.7 permille) in some vent fluids are also consistent with degassing of acid-volatile species from evolved magma. Dissolved CO2 at PACMANUS is more enriched in 13C (-4.1 permille to -2.3 permille) than Vienna Woods (-5.2 permille to -5.7 permille), suggesting a contribution of slab-derived carbon. The mobile elements (e.g. Li, K, Rb, Cs and B) are also greatly enriched in PACMANUS fluids reflecting increased abundances in the crust there relative to the Manus Spreading Center. Variations in alkali and dissolved gas abundances with Cl at PACMANUS and NE Pual suggest that phase separation has affected fluid chemistry despite the low temperatures of many vents. In further contrast to Vienna Woods, substantial modification of PACMANUS/NE Pual fluids has taken place as a result of seawater ingress into the upflow zone. Consistently high measured Mg concentrations as well as trends of increasingly non-conservative SO4 behavior, decreasing endmember Ca/Cl and Sr/Cl ratios with increased Mg indicate extensive subsurface anhydrite deposition is occurring as a result of subsurface seawater entrainment. Decreased pH and endmember Fe/Mn ratios in higher Mg fluids indicate that the associated mixing/cooling gives rise to sulfide deposition and secondary acidity production. Several low temperature (< or = 80 degrees C) fluids at PACMANUS/NE Pual also show evidence for anhydrite dissolution and water-rock interaction (fixation of B) subsequent to seawater entrainment. Hence, the evolution of fluid compositions at Pual Ridge reflects the cumulative effects of water/rock interaction, admixing and reaction of fluids exsolved from silicic magma, phase separation/segregation and seawater ingress into upflow zones.

  16. Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels

    SciTech Connect

    Pastuszko, Robert

    2008-09-15

    Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were taken up. Experimental data were discussed for two kinds of enhanced surfaces formed by joined horizontal and vertical tunnels: tunnel structures (TS) and narrow tunnel structures (NTS). The experiments were carried out with water, ethanol and R-123 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil of 0.05 mm thickness (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 mm high rectangular fins and horizontal inter-fin surface. The effects of hole (pore) diameters, tunnel pitch for TS and tunnel width for NTS on nucleate pool boiling were examined. Substantial enhancement of heat transfer coefficient was observed. The investigated surfaces showed boiling heat transfer coefficients similar to those of existing structures with subsurface tunnels, but at higher heat fluxes range. (author)

  17. Boiling heat transfer on fins - experimental and numerical procedure

    NASA Astrophysics Data System (ADS)

    Orzechowski, T.; Tyburczyk, A.

    2014-03-01

    The paper presents the research methodology, the test facility and the results of investigations into non-isothermal surfaces in water boiling at atmospheric pressure, together with a discussion of errors. The investigations were conducted for two aluminium samples with technically smooth surfaces and thickness of 4 mm and 10 mm, respectively. For the sample of lower thickness, on the basis of the surface temperature distribution measured with an infrared camera, the local heat flux and the heat transfer coefficient were determined and shown in the form of a boiling curve. For the thicker sample, for which 1-D model cannot be used, numerical calculations were conducted. They resulted in obtaining the values of the local heat flux on the surface the invisible to the infrared, camera i.e. on the side on which the boiling of the medium proceeds.

  18. Visualization of pool boiling from complex surfaces with internal tunnels

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert

    2012-04-01

    The paper presents experimental investigations of boiling heat transfer for a system of connected narrow horizontal and vertical tunnels. These extended surfaces, named narrow tunnel structure (NTS), can be applied to electronic element cooling. The experiments were carried out with ethanol at atmospheric pressure. The tunnel external covers were manufactured out of 0.1 mm thick perforated copper foil (hole diameters 0.5 mm), sintered with the mini-fins, formed on the vertical side of the 10 mm high rectangular fins and horizontal inter-fin surface. Visualization studies were conducted with a transparent structured model of joined narrow tunnels limited with the perforated foil. The visualization investigations aimed to formulate assumptions for the boiling model through distinguishing boiling types and defining all phases of bubble growth.

  19. 3. RW Meyer Sugar Mill: 18761889. Sorghum pan and boiling ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    3. RW Meyer Sugar Mill: 1876-1889. Sorghum pan and boiling range flue. Manufactured by John Nott & Co., Honolulu, Hawaii, 1878. View: South side of sorghum pan and boiling range flue. In the sorghum pan heat was applied to the cane juice to clarify it, evaporate its water content, and concentrate the sugar crystals. Hot gasses moved through the flue underneath the entire copper bottom of the sorghum pan from the furnace (east) end to the smokestack (west) end of the boiling range. The sorghum pan sides are of redwood. The flue is built of fire-brick, masonry, and portland cement. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  20. Seismicity and fluid geochemistry at Lassen Volcanic National Park, California: Evidence for two circulation cells in the hydrothermal system

    NASA Astrophysics Data System (ADS)

    Janik, Cathy J.; McLaren, Marcia K.

    2010-01-01

    Seismic analysis and geochemical interpretations provide evidence that two separate hydrothermal cells circulate within the greater Lassen hydrothermal system. One cell originates south to SW of Lassen Peak and within the Brokeoff Volcano depression where it forms a reservoir of hot fluid (235-270 °C) that boils to feed steam to the high-temperature fumarolic areas, and has a plume of degassed reservoir liquid that flows southward to emerge at Growler and Morgan Hot Springs. The second cell originates SSE to SE of Lassen Peak and flows southeastward along inferred faults of the Walker Lane belt (WLB) where it forms a reservoir of hot fluid (220-240 °C) that boils beneath Devils Kitchen and Boiling Springs Lake, and has an outflow plume of degassed liquid that boils again beneath Terminal Geyser. Three distinct seismogenic zones (identified as the West, Middle, and East seismic clusters) occur at shallow depths (< 6 km) in Lassen Volcanic National Park, SW to SSE of Lassen Peak and adjacent to areas of high-temperature (≤ 161 °C) fumarolic activity (Sulphur Works, Pilot Pinnacle, Little Hot Springs Valley, and Bumpass Hell) and an area of cold, weak gas emissions (Cold Boiling Lake). The three zones are located within the inferred Rockland caldera in response to interactions between deeply circulating meteoric water and hot brittle rock that overlies residual magma associated with the Lassen Volcanic Center. Earthquake focal mechanisms and stress inversions indicate primarily N-S oriented normal faulting and E-W extension, with some oblique faulting and right lateral shear in the East cluster. The different focal mechanisms as well as spatial and temporal earthquake patterns for the East cluster indicate a greater influence by regional tectonics and inferred faults within the WLB. A fourth, deeper (5-10 km) seismogenic zone (the Devils Kitchen seismic cluster) occurs SE of the East cluster and trends NNW from Sifford Mountain toward the Devils Kitchen thermal area where fumarolic temperatures are ≤ 123 °C. Lassen fumaroles discharge geothermal gases that indicate mixing between a N 2-rich, arc-type component and gases derived from air-saturated meteoric recharge water. Most gases have relatively weak isotopic indicators of upper mantle or volcanic components, except for gas from Sulphur Works where δ13C-CO 2, δ34S-H 2S, and δ15N-N 2 values indicate a contribution from the mantle and a subducted sediment source in an arc volcanic setting.

  1. Nucleate pool boiling from a horizontal wire in viscoelastic fluids

    SciTech Connect

    Hu, Y.R.

    1989-01-01

    The nucleate pool boiling behavior of viscoelastic aqueous polymer solutions has been studied experimentally and compared with results for pure water. The polymers used in this study were a polyacrylamide (Separan AP-30) and a hydroxyethyl cellulose (Natrosol 250HHR). The conventional q{double prime} vs {Delta}T boiling curves were measured using an electrically heated horizontal platinum wire of diameter 0.0254 cm submerged in a saturated pool of liquid at atmospheric pressure. The steady shear viscosity of each polymer solution was measured carefully over the shear rate range of 10{sup {minus}1} to 10{sup 5} sec{sup {minus}1} both before and after boiling to ensure that the rheological properties were stable during the boiling process. It was found that the water boiling data are in good agreement with Kutateladze's correlation, with Rohsenow's earlier correlation proposed in 1952 and in fair agreement with Nishikawa's correlation. All of the Separan solutions, over the experimental heat flux range of 2.2 to 55 W/cm{sup 2}, demonstrated a heat transfer reduction as compared to the water performance. In the case of the Natrosol solutions, the lowest concentration of 500 wppm gave results which were about the same as found for water. However, at concentrations of 1,500 wppm and above, dramatically different behavior was observed. At lower heat flux values the magnitude of AT increased as q{double prime} increased, as anticipated. However, at approximately 13 W/cm{sup 2} a maximum {delta}T was reached and as q{double prime} was increased above 13 W/cm{sup 2} the value of {Delta}T decreased. A series of photographic studies taken with a regular home video camera and a high speed video camera provided additional insight into the boiling process for all the solutions.

  2. Hysteresis of boiling for different tunnel-pore surfaces

    NASA Astrophysics Data System (ADS)

    Pastuszko, Robert; Piasecka, Magdalena

    2015-05-01

    Analysis of boiling hysteresis on structured surfaces covered with perforated foil is proposed. Hysteresis is an adverse phenomenon, preventing high heat flux systems from thermal stabilization, characterized by a boiling curve variation at an increase and decrease of heat flux density. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS), narrow tunnel structures (NTS) and mini-fins covered with the copper wire net (NTS-L). The experiments were carried out with water, R-123 and FC-72 at atmospheric pressure. A detailed analysis of the measurement results identified several cases of type I, II and III for TS, NTS and NTS-L surfaces.

  3. 23. RW Meyer Sugar Mill: 18761889. Boiling House Interior, 1878. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. RW Meyer Sugar Mill: 1876-1889. Boiling House Interior, 1878. View: North Wall of boiling house. In the original structure the three windows on the right admitted light and air from the outside. A shed occupied the left side of the wall outside (hence no windows). in 1881 the construction of the cooling shed closed in the right three windows. The sorghum is in the foreground. The centrifugals are in the left rear. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  4. Heat Transfer in Boiling Dilute Emulsion with Strong Buoyancy

    NASA Astrophysics Data System (ADS)

    Freeburg, Eric Thomas

    Little attention has been given to the boiling of emulsions compared to that of boiling in pure liquids. The advantages of using emulsions as a heat transfer agent were first discovered in the 1970s and several interesting features have since been studied by few researchers. Early research focuses primarily on pool and flow boiling and looks to determine a mechanism by which the boiling process occurs. This thesis looks at the boiling of dilute emulsions in fluids with strong buoyant forces. The boiling of dilute emulsions presents many favorable characteristics that make it an ideal agent for heat transfer. High heat flux electronics, such as those seen in avionics equipment, produce high heat fluxes of 100 W/cm2 or more, but must be maintained at low temperatures. So far, research on single phase convection and flow boiling in small diameter channels have yet to provide an adequate solution. Emulsions allow the engineer to tailor the solution to the specific problem. The fluid can be customized to retain the high thermal conductivity and specific heat capacity of the continuous phase while enhancing the heat transfer coefficient through boiling of the dispersed phase component. Heat transfer experiments were carried out with FC-72 in water emulsions. FC-72 has a saturation temperature of 56 °C, far below that of water. The parameters were varied as follows: 0% ≤ epsilon ≤ 1% and 1.82 x 1012 ≤ RaH ≤ 4.42 x 1012. Surface temperatures along the heated surface reached temperature that were 20 °C in excess of the dispersed phase saturation temperature. An increase of ˜20% was seen in the average Nusselt numbers at the highest Rayleigh numbers. Holography was used to obtain images of individual and multiple FC-72 droplets in the boundary layer next to the heated surface. The droplet diameters ranged from 0.5 mm to 1.3 mm. The Magnus effect was observed when larger individual droplets were injected into the boundary layer, causing the droplets to be pushed outside the boundary layer. Vaporization of FC-72 droplets in the boundary layer next to the heated surface was not observed.

  5. On Boiling of Crude Oil under Elevated Pressure

    NASA Astrophysics Data System (ADS)

    Pimenova, Anastasiya V.; Goldobin, Denis S.

    2016-02-01

    We construct a thermodynamic model for theoretical calculation of the boiling process of multicomponent mixtures of hydrocarbons (e.g., crude oil). The model governs kinetics of the mixture composition in the course of the distillation process along with the boiling temperature increase. The model heavily relies on the theory of dilute solutions of gases in liquids. Importantly, our results are applicable for modelling the process under elevated pressure (while the empiric models for oil cracking are not scalable to the case of extreme pressure), such as in an oil field heated by lava intrusions.

  6. Simultaneous neutron radiography and infrared thermography measurement of boiling processes

    SciTech Connect

    Murphy, J.H.; Glickstein, S.S.

    1997-02-01

    Boiling of water at 1 to 15 bar flowing upward within a narrow duct and a round test section was observed using both neutron radiography and infrared (IR) thermography. The IR readings of the test section outer wall temperatures show the effects of both fluid temperature and wall heat transfer coefficient variations, producing a difference between liquid and two phase regions. The IR images, in fact, appear very similar to the neutron images; both show clear indications of spatial and temporal variations in the internal fluid conditions during the boiling process.

  7. Simultaneous neutron radiography and infrared thermography measurement of boiling processes

    SciTech Connect

    Murphy, J.H.; Glickstein, S.S.

    1996-12-31

    Boiling of water at 1 to 15 bar flowing upward within a narrow duct and a round test section was observed using both neutron radiography and infrared (IR) thermography. The IR readings of the test section outer wall temperatures show the effects of both fluid temperature and wall heat transfer coefficient variations, producing a difference between liquid and two phase regions. The IR images, in fact, appear very similar to the neutron images; both show clear indications of spatial and temporal variations in the internal fluid conditions during the boiling process.

  8. Study of hydrothermal channels based on near-bottom magnetic prospecting: Application to Longqi hydrothermal area

    NASA Astrophysics Data System (ADS)

    Tao, W.; Tao, C.; Li, H.; Zhaocai, W.; Jinhui, Z.; Qinzhu, C.; Shili, L.

    2014-12-01

    Mid-ocean ridges, largely present far from the continental plates, are characterized by complex geological structures and numerous hydrothermal systems with complex controlling factors. Exploring seafloor sulfide resources for industrial and scientific applications is a challenge. With the advent of geophysical surveys for seabed investigation, near-bottom magnetic prospecting, which yields shallow geological structure, is an efficient method for investigating active and inactive hydrothermal fields and for researching the structure of hydrothermal systems (Tivey et al., 1993, 1996;German et al., 2008). We collected near-bottom magnetic data in the Longqi hydrothermal area, located in the southwest Indian ridge (49.6° E; Zhu et al., 2010; Tao et al., 2014), using the autonomous benthic explorer, an autonomous underwater vehicle, during the second leg of the Chinese cruise DY115-19 on board R/V DaYangYiHao. Based on the results of the intensity of the spatial differential vector method (Seaman et al., 1993), we outline the hydrothermal alternation zone. By building models, we subsequently infer a fault along the discovered hydrothermal vents; this fault line may be connected to a detachment fault (Zhao et al., 2013). In addition, we discuss the channels of the hydrothermal circulation system (Figure 1), and presume that heat was conducted to the sea subsurface by the detachment fault; the aqueous fluid that infiltrated the fault is heated and conveyed to the seafloor, promoting the circulation of the hydrothermal system.

  9. Length Scale and Gravity Effects on Microgravity Boiling Heat Transfer

    NASA Technical Reports Server (NTRS)

    Kim, Jungho; McQuillen, John; Balombin, Joe

    2002-01-01

    Boiling is a complex phenomenon where hydrodynamics, heat transfer, mass transfer, and interfacial phenomena are tightly interwoven. An understanding of boiling and critical heat flux in microgravity environments is of importance to space based hardware and processes such as heat exchange, cryogenic fuel storage and transportation, electronic cooling, and material processing due to the large amounts of heat that can be removed with relatively little increase in temperature. Although research in this area has been performed in the past four decades, the mechanisms by which heat is removed from surfaces in microgravity are still unclear. In earth gravity, buoyancy is an important parameter that affects boiling heat transfer through the rate at which bubbles are removed from the surface. A simple model describing the bubble departure size based on a quasistatic force balance between buoyancy and surface tension is given by the Fritz [I] relation: Bo(exp 1/2) = 0.0208 theta where Bo is the ratio between buoyancy and surface tension forces. For small, rapidly growing bubbles, inertia associated with the induced liquid motion can also cause bubble departure. In microgravity, the magnitude of effects related to natural convection and buoyancy are small and physical mechanisms normally masked by natural convection in earth gravity such as Marangoni convection can substantially influence the boiling and vapor bubble dynamics. CHF (critical heat transfer) is also substantially affected by microgravity. In 1 g environments, Bo has been used as a correlating parameter for CHF. Zuber's CHF model for an infinite horizontal surface assumes that vapor columns formed by the merger of bubbles become unstable due to a Helmholtz instability blocking the supply of liquid to the surface. The jets are spaced lambda(sub D) apart, where lambda(sub D) = 2pi square root of 3[(sigma)/(g(rho(sub l) - rho(sub v)](exp 1/2) = 2pi square root of 3 L Bo(exp -1/2) = square root of 3 lambda(sub c) and is the wavelength that amplifies most rapidly. The critical wavelength, lambda(sub c), is the wavelength below which a vapor layer underneath a liquid layer is stable. For heaters with Bo smaller than about 3 (heaters smaller than lambda(sub D)), the above model is not applicable, and surface tension effects dominate. Bubble coalescence is thought to be the mechanism for CHF under these conditions. Small Bo can result by decreasing the size of a heater in earth gravity, or by operating a large heater in a lower gravity environment. In the microgravity of space, even large heaters can have low Bo, and models based on Helmholtz instability should not be applicable. The macrolayer model of Haramura and Katto is dimensionally equivalent to Zuber's model and has the same dependence on gravity, so it should not be applicable as well. The goal of this work is to determine how boiling heat transfer mechanisms in a low-g environment are altered from those at higher gravity levels. Boiling data using a microheater array was obtained under gravity environments ranging from 1.8 g to 0.02 g with heater sizes ranging from 2.7 mm to 1 mm. The boiling behavior for 2.7 mm at 0.02 g looked quite similar to boiling on the 1 mm heater at 1 g-the formation of a large primary bubble surrounded by smaller satellite bubbles was observed under both conditions. The similarity suggests that for heaters smaller than some fraction of I(sub c), coalescence and surface tension dominate boiling heat transfer. It also suggests that microgravity boiling can be studied by studying boiling on very small heaters.

  10. Hydrothermal origin of halogens at Home Plate, Gusev Crater

    NASA Astrophysics Data System (ADS)

    Schmidt, Mariek E.; Ruff, Steven W.; McCoy, Timothy J.; Farrand, William H.; Johnson, Jeffrey R.; Gellert, Ralf; Ming, Douglas W.; Morris, Richard V.; Cabrol, Nathalie; Lewis, Kevin W.; Schroeder, Christian

    2008-06-01

    In the Inner Basin of the Columbia Hills, Gusev Crater is Home Plate, an 80 m platform of layered clastic rocks of the Barnhill class with microscopic and macroscopic textures, including a bomb sag, suggestive of a phreatomagmatic origin. We present data acquired by the Spirit Mars Exploration Rover by Alpha Particle X-Ray Spectrometer (APXS), Mössbauer Spectrometer, Miniature Thermal Emission Spectrometer (Mini-TES), and Panoramic Camera (Pancam) for the Barnhill class rocks and nearby vesicular Irvine class basalts. In major element concentrations (e.g., SiO2, Al2O3, MgO, and FeO*), the two rock classes are similar, suggesting that they are derived from a similar magmatic source. The Barnhill class, however, has higher abundances of Cl, Br, Zn, and Ge with comparable SO3 to the Irvine basalts. Nanophase ferric oxide (np ox) and volcanic glass were detected in the Barnhill class rocks by Mössbauer and Mini-TES, respectively, and imply greater alteration and cooling rates in the Barnhill than in the Irvine class rocks. The high volatile elements in the Barnhill class agree with volcanic textures that imply interaction with a briny groundwater during eruption and (or) by later alteration. Differences in composition between the Barnhill and Irvine classes allow the fingerprinting of a Na-Mg-Zn-Ge-Cl-Br (+/-Fe +/- Ca +/- CO2) brine with low S. Nearby sulfate salt soils of fumarolic origin may reflect fractionation of an acidic S-rich vapor during boiling of a hydrothermal brine at depth. Persistent groundwater was likely present during and after the formation of Home Plate.

  11. Hydrothermal origin of halogens at Home Plate, Gusev Crater

    USGS Publications Warehouse

    Schmidt, M.E.; Ruff, S.W.; McCoy, T.J.; Farrand, W. H.; Johnson, J. R.; Gellert, Ralf; Ming, D. W.; Morris, R.V.; Cabrol, N.; Lewis, K.W.; Schroeder, C.

    2008-01-01

    In the Inner Basin of the Columbia Hills, Gusev Crater is Home Plate, an 80 m platform of layered elastic rocks of the Barnhill class with microscopic and macroscopic textures, including a bomb sag, suggestive of a phreatomagmatic origin. We present data acquired by the Spirit Mars Exploration Rover by Alpha Particle X-Ray Spectrometer (APXS), Mo??ssbauer Spectrometer, Miniature Thermal Emission Spectrometer (Mini-TES), and Panoramic Camera (Pancam) for the Barnhill class rocks and nearby vesicular Irvine class basalts. In major element concentrations (e.g., SiO2, Al2O3, MgO, and FeO*), the two rock classes are similar, suggesting that they are derived from a similar magmatic source. The Barnhill class, however, has higher abundances of Cl, Br, Zn, and Ge with comparable SO3 to the Irvine basalts. Nanophase ferric oxide (np ox) and volcanic glass were detected in the Barnhill class rocks by Mo??ssbauer and Mini-TES, respectively, and imply greater alteration and cooling rates in the Barnhill than in the Irvine class rocks. The high volatile elements in the Barnhill class agree with volcanic textures that imply interaction with a briny groundwater during eruption and (or) by later alteration. Differences in composition between the Barnhill and Irvine classes allow the fingerprinting of a Na-Mg-Zn-Ge-Cl-Br (??Fe ?? Ca ?? CO2) brine with low S. Nearby sulfate salt soils of fumarolic origin may reflect fractionation of an acidic S-rich vapor during boiling of a hydrothermal brine at depth. Persistent groundwater was likely present during and after the formation of Home Plate. Copyright 2008 by the American Geophysical Union.

  12. 76 FR 61118 - Meeting of the ACRS Subcommittee on Advanced Boiling Water Reactor; Notice of Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-03

    ... published in the Federal Register on October 21, 2010, (75 FR 65038-65039). Detailed meeting agendas and... Boiling Water Reactor; Notice of Meeting The ACRS Subcommittee on Advanced Boiling Water Reactor...

  13. 77 FR 3009 - Knowledge and Abilities Catalog for Nuclear Power Plant Operators: Advanced Boiling Water Reactors

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-20

    ... COMMISSION Knowledge and Abilities Catalog for Nuclear Power Plant Operators: Advanced Boiling Water Reactors..., ``Knowledge and Abilities Catalog for Nuclear Power Plant Operators: Advanced Boiling Water Reactors.'' DATES... Rockville Pike, Rockville, Maryland 20852. NRC's Agencywide Documents Access and Management System...

  14. Hydrothermal alteration in the EPF replacement wells, Olkaria Geothermal field, Kenya

    SciTech Connect

    Mungania, J.

    1996-12-31

    Olkaria Geothermal area is located in the central sector of the Kenya, Rift Valley. A 45MW Geothermal power station has been operational at Olkaria since 1985 supplied by 22 of the 26 wells drilled in the Eastern production field (EPF). Between 1988 and 1993, eight more wells referred to as {open_quote}replacement wells{close_quote} were drilled in the same field to boost steam supply to the station. Petrographic analyses of the drill cuttings is usually done to determine detail stratigraphy of the field, extends of hydrothermal activity, subsurface structures and other parameters which may influence production potential of a well. Analyses of the drill cuttings from the EPF wells show that: Variations in the whole rock alteration intensities correlate with differences in rocktypes. Permeable horizons, especially the productive feeder zones are well marked by enhanced hydrothermal minerals depositions, mainly quartz, calcite, pyrite and epidote. Other aspects of state of reservoir like boiling are signified by presence of bladed calcite.

  15. Large-scale hydrothermal fluid discharges in the Norris-Mammoth corridor, Yellowstone National Park, USA

    USGS Publications Warehouse

    Kharaka, Y.K.; Sorey, M.L.; Thordsen, J.J.

    2000-01-01

    Norris–Mammoth corridor is a complex subsidence structure that extends ∼40 km northward from the 0.6 Ma Yellowstone caldera, and contains many hydrothermal features with high fluid discharges totaling ∼1000 l/s. About 150–250 l/s of hydrothermal water, which attains boiling temperature at surface and 360°C at depth, discharge from the Norris Geyser Basin, adjacent to the caldera. The highest thermal water and gas discharges in the corridor are from Mammoth Hot Springs, where 500–600 l/s thermal water with surface temperatures of up to 73°C and calculated subsurface temperatures of ∼100°C issue from ∼100 hot springs scattered over a score of step-like travertine terraces that range in age from ∼0.4 Ma to recent. All the thermal water is meteoric, likely recharged in the Gallatin Range at 2.5–3.0 km elevations. The isotopic and chemical compositions of thermal waters and solutes can be interpreted to indicate a common magmatic source for heat and volatile solutes located near Norris. However, the chemical and isotopic compositions of gases, especially the 3He/4He ratios, provide strong evidence for a separate magmatic source for the Mammoth system.

  16. Phase separation, brine formation, and salinity variation at Black Smoker hydrothermal systems

    NASA Astrophysics Data System (ADS)

    Coumou, D.; Driesner, T.; Weis, P.; Heinrich, C. A.

    2009-03-01

    We present the first fully transient 2-D numerical simulations of black smoker hydrothermal systems using realistic fluid properties and allowing for all phase transitions possible in the system H2O-NaCl, including phase separation of convecting seawater into a low-salinity vapor and high-salinity brine. We investigate convection, multiphase flow, and phase segregation at pressures below, near, and above the critical point of seawater. Our simulations accurately predict the range in vent salinities, from 0.05 to 2.5 times seawater salinity measured at natural systems. In low-pressure systems at 1500 m water depth, phase separation occurs in boiling zones stretching from the bottom of the hydrothermal cell to the seafloor. Low-salinity vapors and high-salinity brines can vent simultaneously, and transient variations in vent fluid salinities can be rapid. In high-pressure systems at roughly 3500 m water depth, phase separation is limited to the region close to the underlying magma chamber, and vent fluids consist of a low-salinity vapor mixed with a seawater-like fluid. Therefore, vent salinities from these systems are much more uniform in time and always below seawater salinity as long as phase separation occurs in the subseafloor. Only by shutting down the heat source can, in the high-pressure case, the brine be mined, resulting in larger than seawater salinities. These numerical results are in good agreement with long-term observations from several natural black smoker systems.

  17. Understanding the structural features of high-amylose maize starch through hydrothermal treatment.

    PubMed

    Yang, Jianing; Xie, Fengwei; Wen, Wenqiang; Chen, Ling; Shang, Xiaoqin; Liu, Peng

    2016-03-01

    In this study, high-amylose starches were hydrothermally-treated and the structural changes were monitored with time (up to 12h) using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), small-angle X-ray scattering (SAXS), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). When high-amylose starches were treated in boiling water, half-shell-like granules were observed by SEM, which could be due to the first hydrolysis of the granule inner region (CLSM). This initial hydrolysis could also immediately (0.5h) disrupt the semi-crystalline lamellar regularity (SAXS) and dramatically reduce the crystallinity (XRD); but with prolonged time of hydrothermal treatment (≥2h), might allow the perfection or formation of amylose single helices, resulting in slightly increased crystallinity (XRD and DSC). These results show that the inner region of granules is composed of mainly loosely-packed amylopectin growth rings with semi-crystalline lamellae, which are vulnerable under gelatinization or hydrolysis. In contrast, the periphery is demonstrated to be more compact, possibly composed of amylose and amylopectin helices intertwined with amylose molecules, which require greater energy input (higher temperature) for disintegration. PMID:26708428

  18. Hydrothermal flow regime and magmatic heat source of the Cerro Prieto geothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Schiffman, P.; Williams, A.E.

    1984-01-01

    This detailed three-dimensional model of the natural flow regime of the Cerro Prieto geothermal field, before steam production began, is based on patterns of hydrothermal mineral zones and light stable isotopic ratios observed in rock samples from more than 50 deep wells, together with temperature gradients, wireline logs and other data. At the level so far penetrated by drilling, this hydrothermal system was heated by a thermal plume of water close to boiling, inclined at 45/sup 0/, rising from the northeast and discharging to the west. To the east a zone of cold water recharge overlies the inclined thermal plume. Fission track annealing studies show the reservoir reached 170/sup 0/C only 10/sup 4/ years ago. Oxygen isotope exchange data indicate that a 12 km/sup 3/ volume of rock subsequently reacted with three times its volume of water hotter than 200/sup 0/C. Averaged over the duration of the heating event this would require a flow velocity through a typical cross-section of the reservoir of about 6 m/year. The heat in storage in that part of the reservoir hotter than 200/sup 0/C and shallower than 3 km depth is equivalent to that which would be released by the cooling of about 1 or 2 km/sup 3/ of basalt or gabbro magma.

  19. Synthesis of hydrothermally stable, hierarchically mesoporous aluminosilicate Al-SBA-1 and their catalytic properties

    NASA Astrophysics Data System (ADS)

    Li, Na; Wang, Jin-Gui; Xu, Jian-Xiong; Liu, Jin-Yu; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

    2012-03-01

    Hydrothermally stable mesoporous aluminosilicates Al-SBA-1 with hierarchical pore structure have been successfully synthesized under alkaline condition at 120 C by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecyl pyridinium chloride (CPC)) as template. The Si/Al ratio could be as high as 5 and the incorporation of Al into the silica framework did not disturb the well-ordered cubic Pm3&cmb.macr;n mesostructure. Meanwhile, the incorporation of Al could greatly increase the specific surface area and pore volume of the samples. The Al-SBA-1 materials exhibited a high hydrothermal stability and remained stable even after being treated in boiling water for 10 days. The catalytic activity of the Al-SBA-1 materials was investigated by employing the Friedel-Crafts alkylation of toluene with benzyl alcohol as a model reaction and they exhibited excellent catalytic property due to the incorporated acid sites and the hierarchically mesoporous structure.

  20. Synthesis of hydrothermally stable, hierarchically mesoporous aluminosilicate Al-SBA-1 and their catalytic properties.

    PubMed

    Li, Na; Wang, Jin-Gui; Xu, Jian-Xiong; Liu, Jin-Yu; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

    2012-03-21

    Hydrothermally stable mesoporous aluminosilicates Al-SBA-1 with hierarchical pore structure have been successfully synthesized under alkaline condition at 120 C by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecyl pyridinium chloride (CPC)) as template. The Si/Al ratio could be as high as 5 and the incorporation of Al into the silica framework did not disturb the well-ordered cubic Pm ?3n mesostructure. Meanwhile, the incorporation of Al could greatly increase the specific surface area and pore volume of the samples. The Al-SBA-1 materials exhibited a high hydrothermal stability and remained stable even after being treated in boiling water for 10 days. The catalytic activity of the Al-SBA-1 materials was investigated by employing the Friedel-Crafts alkylation of toluene with benzyl alcohol as a model reaction and they exhibited excellent catalytic property due to the incorporated acid sites and the hierarchically mesoporous structure. PMID:22327221

  1. Permeability Reduction in Passively Degassing Seawater-dominated Volcanic-hydrothermal systems: Processes and Perils on Raoul Island, Kermadecs (NZ)

    NASA Astrophysics Data System (ADS)

    Christenson, B. W.; Reyes, A. G.

    2014-12-01

    The 2006 eruption from Raoul Island occurred apparently in response to local tectonic swarm activity, but without any precursory indication of volcanic unrest within the hydrothermal system on the island. The eruption released some 200 T of SO2, implicating the involvement of a deep magmatic vapor input into the system during/prior to the event. In the absence of any recognized juvenile material in the eruption products, previous explanations for this eruptive event focused on this vapor being a driving force for the eruption. In 2004, at least 80 T/d of CO2 was escaping from the hydrothermal system, but mainly through areas that did not correspond to the 2006 eruption vents. The lack of a pre-eruptive hydrothermal system response related to the seismic event in 2006 can be explained by the presence of a hydrothermal mineralogic seal in the vent area of the volcano. Evidence for the existence of such a seal was found in eruption deposits in the form of massive fracture fillings of aragonite, calcite and anhydrite. Fluid inclusion homogenization temperatures in these phases range from ca. 140 °C to 220 °C which, for pure water indicate boiling point depths of between 40 and 230 m assuming a cold hydrostatic pressure constraint. Elevated pressures behind this seal are consistent with the occurrence of CO2 clathrates in some inclusion fluids, indicating CO2 concentrations approaching 1 molal in the parent fluids. Reactive transport modeling of magmatic volatile inputs into what is effectively a seawater-dominated hydrothermal system provide valuable insights into seal formation. Carbonate mineral phases ultimately come to saturation along this flow path, but we suggest that focused deposition of the observed massive carbonate seal is facilitated by near-surface boiling of these CO2-enriched altered seawaters, leading to large degrees of supersaturation which are required for the formation of aragonite. As the seal grew and permeability declined, pore pressures increased until a state of critical stress was achieved. The eruption of 2006 was probably triggered by further deep release of magmatic volatiles brought about by intense shaking of the local tectonic swarm event, and the addition of these gases further increased pore pressures, and ultimately led to the failure of the already critically stressed seal.

  2. Hydrothermal convection and mordenite precipitation in the cooling Bishop Tuff, California, USA

    NASA Astrophysics Data System (ADS)

    Randolph-Flagg, N. G.; Breen, S. J.; Hernandez, A.; Self, S.; Manga, M.

    2014-12-01

    We present field observations of erosional columns in the Bishop Tuff and then use laboratory results and numerical models to argue that these columns are evidence of relict convection in a cooling ignimbrite. Many square kilometers of the Bishop Tuff have evenly-spaced, vertical to semi-vertical erosional columns, a result of hydrothermal alteration. These altered regions are more competent than the surrounding tuff, are 0.1-0.7 m in diameter, are separated by ~ 1 m, and in some cases are more than 8 m in height. JE Bailey (U. of Hawaii, dissertation, 2005) suggested that similar columns in the Bandelier Tuff were formed when slumping allowed water to pool at the surface of the still-cooling ignimbrite. As water percolated downward it boiled generating evenly spaced convection cells similar to heat pipes. We quantify this conceptual model and apply it the Bishop Tuff to understand the physics within ignimbrite-borne hydrothermal systems. We use thin sections to measure changing porosity and use scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses to show that pore spaces in the columns are cemented by the mineral mordenite, a low temperature zeolite that precipitates between 120-200 oC (Bish et al., 1982), also found in the Bandelier Tuff example. We then use scaling to show 1) that water percolating into the cooling Bishop Tuff would convect and 2) that the geometry and spacing of the columns is predicted by the ignimbrite temperature and permeability. We use the computer program HYDROTHERM (Hayba and Ingebritsen, 1994; Kipp et al., 2008) to model 2-phase convection in the Bishop Tuff. By systematically changing permeability, initial temperature, and topography we can identify the pattern of flows that develop when the ignimbrite is cooled by water from above. Hydrothermally altered columns in ignimbrite are the natural product of coupled heat, mass, and chemical transport and have similarities to other geothermal systems, economic ore deposits, and mid-ocean ridge hydrothermal systems. The columns allow direct observation to constrain complex models of multiphase convection, reactive transport, and permeability. Our results also have paleoclimate implications, implying a large and stable source of water in the SE/SSE Long Valley area immediately after the ~760,000 ka caldera-forming eruption.

  3. Experimental study on bubble departure frequency for pool boiling of water/NaCl solutions

    NASA Astrophysics Data System (ADS)

    Hamzekhani, Samane; Falahieh, Majedeh Maniavi; Kamalizadeh, Mohammad Rasoul; Nazari, Zahra

    2015-09-01

    Nucleate pool boiling experiments were conducted for water and water/NaCl solutions at atmospheric pressure. Many analyses of boiling heat transfer include the terms bubble frequency in their expressions for nucleate boiling heat flux. Experimental results show that the bubble frequency increases with increasing boiling heat flux and decreases with increasing NaCl concentration at same conditions. A new model for the prediction of bubble departure frequency is proposed, which predicts the experimental data with a satisfactory accuracy.

  4. Acoustic emission feedback control for control of boiling in a microwave oven

    DOEpatents

    White, Terry L.

    1991-01-01

    An acoustic emission based feedback system for controlling the boiling level of a liquid medium in a microwave oven is provided. The acoustic emissions from the medium correlated with surface boiling is used to generate a feedback control signal proportional to the level of boiling of the medium. This signal is applied to a power controller to automatically and continuoulsly vary the power applied to the oven to control the boiling at a selected level.

  5. Electrochemical study of aluminum corrosion in boiling high purity water

    NASA Technical Reports Server (NTRS)

    Draley, J. E.; Legault, R. A.

    1969-01-01

    Electrochemical study of aluminum corrosion in boiling high-purity water includes an equation relating current and electrochemical potential derived on the basis of a physical model of the corrosion process. The work involved an examination of the cathodic polarization behavior of 1100 aluminum during aqueous oxidation.

  6. Experimental demonstration of contaminant removal from fractured rock by boiling.

    PubMed

    Chen, Fei; Liu, Xiaoling; Falta, Ronald W; Murdoch, Lawrence C

    2010-08-15

    This study was conducted to experimentally demonstrate removal of a chlorinated volatile organic compound from fractured rock by boiling. A Berea sandstone core was contaminated by injecting water containing dissolved 1,2-DCA (253 mg/L) and sodium bromide (144 mg/L). During heating, the core was sealed except for one end, which was open to the atmosphere to simulate an open fracture. A temperature gradient toward the outlet was observed when boiling occurred in the core. This indicates that steam was generated and a pressure gradient developed toward the outlet, pushing steam vapor and liquid water toward the outlet. As boiling occurred, the concentration of 1,2-DCA in the condensed effluent peaked up to 6.1 times higher than the injected concentration. When 38% of the pore volume of condensate was produced, essentially 100% of the 1,2-DCA was recovered. Nonvolatile bromide concentration in the condensate was used as an indicator of the produced steam quality (vapor mass fraction) because it can only be removed as a solute, and not as a vapor. A higher produced steam quality corresponds to more concentrated 1,2-DCA removal from the core, demonstrating that the chlorinated volatile compound is primarily removed by partitioning into vapor phase flow. This study has experimentally demonstrated that boiling is an effective mechanism for CVOC removal from the rock matrix. PMID:20666474

  7. Single Bubble Dynamics on Superhydrophilic Micropillar Arrays during Flow Boiling

    NASA Astrophysics Data System (ADS)

    Feng, Jiansheng; Chen, Siyu; Zhang, Tiejun; Wang, Evelyn; Device Research Laboratory Team

    2013-11-01

    Micro/nanoengineered surfaces have received recent interest for high heat flux thermal management solutions. In particular, micropillar arrays promise opportunities to enhance flow boiling performance, but an increasing understanding of the role of these structures are still needed. In this study, we used superhydrophilic micropillar arrays with well-defined geometries to investigate bubble growth and departure dynamics during boiling. These structures were individually tested in a closed-loop flow boiling setup. A combined side-view microscopy and high-speed videography technique was utilized to obtain images of bubble growth and departure. We demonstrated that by increasing the solid fraction of the microstructures, bubble departure can occur at smaller sizes and at higher frequencies comparing to that on a flat hydrophilic surface. Meanwhile, we observed that bubble sliding stage between departing from the nucleation site and detaching from the heated surface, which is present under a wide range of conditions during flow boiling on flat surfaces, was highly suppressed on some of the microstructured surfaces. In addition, we used a surface energy based model to explain the confinement effect of the liquid-vapor interface by the micropillar arrays, and to support our experimental findings that solid fraction is a key parameter dictating bubble dynamics. This work is supported by the Masdar Institute of Science and Technology.

  8. Nucleate boiling of water from plain and structured surfaces

    SciTech Connect

    Das, A.K.; Das, P.K.; Saha, P.

    2007-08-15

    Heat transfer from plain surface and from surfaces with distinct nucleation sites has been investigated under saturated pool boiling condition. Surfaces have been prepared with regular array of discrete nucleation sites formed by micro-drilling. Distilled water has been used as the boiling liquid. Out of various available correlations, Rohsenow correlation [W.M. Rohsenow, A method of correlating heat transfer data for surface boiling of liquids, Trans. ASME 74 (1952) 969-976] gives best agreement with the experimental data from plain surface at low degree of superheat. A mechanistic model also provides a good trend matching with the same experimental data. With the introduction of artificial nucleation sites substantial augmentation in heat transfer for distilled water compared to the plane surface has been noted. Continuous increase in nucleation site density increases the rate of heat transfer with a diminishing trend of enhancement. A correlation similar to that of Yamagata et al. [K. Yamagata, F. Hirano, K. Nishiwaka, H. Matsouka, Nucleate boiling of water on the horizontal heating surface, Mem. Fac. Eng. Kyushu 15 (1955) 98] has been developed to fit the experimental data of plane surface. Modification of the same correlation to take care of the nucleation site density has been developed and used to predict the experimental data from augmented surfaces. (author)

  9. Flow Boiling Critical Heat Flux in Reduced Gravity

    NASA Technical Reports Server (NTRS)

    Mudawar, Issam; Zhang, Hui; Hasan, Mohammad M.

    2004-01-01

    This study provides systematic method for reducing power consumption in reduced gravity systems by adopting minimum velocity required to provide adequate CHF and preclude detrimental effects of reduced gravity . This study proves it is possible to use existing 1 ge flow boiling and CHF correlations and models to design reduced gravity systems provided minimum velocity criteria are met

  10. Research on radiation detectors, boiling transients, and organic lubricants

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The accomplishments of a space projects research facility are presented. The subjects discussed are: (1) a study of radiation resistant semiconductor devices, (2) synthesis of high temperature organic lubricants, (3) departure from phase equilibrium during boiling transients, (4) effects of neutron irradiation on defect state in tungsten, and (5) determination of photon response function of NE-213 liquid scintillation detectors.

  11. Teachers College Students' Conceptions about Evaporation, Condensation, and Boiling.

    ERIC Educational Resources Information Center

    Chang, Jin-Yi

    1999-01-01

    An open-ended, written test was administered to 364 students divided into four groups according to their scientific learning background at a teachers college. Results indicate that although the science-major students performed better than nonscience majors, their understanding of condensation and boiling concepts still needed to be enhanced.…

  12. Treatment of cork boiling wastewater using chemical oxidation and biodegradation.

    PubMed

    Dias-Machado, Manuela; Madeira, Luis M; Nogales, Balbina; Nunes, Olga C; Manaia, Clia M

    2006-06-01

    Three cultures were enriched from cork boiling wastewater using tannic acid as the selective carbon substrate, at 25 degrees C and pH 7.2, 25 degrees C and pH 4.7 and 50 degrees C and pH 4.7. The enrichment culture obtained at neutral pH was composed of five culturable isolates, whereas from each acidic enrichment two bacterial strains were isolated. Mesophilic isolates were Gram negative bacteria belonging to the genera Klebsiella, Pseudomonas, Stenotrophomonas and Burkholderia. Thermophilic isolates were members of the genus Bacillus. Despite the capability of the enrichment cultures to use tannic acid as single carbon and energy source, those cultures were unable to reduce the total polyphenols or the total organic carbon content of cork boiling wastewater. In order to increase the bioavailability of the organic carbon in cork boiling wastewater, biodegradation was preceded by Fenton oxidation. It was demonstrated that the combined process, using small amounts of Fenton reagents and biodegradative inoculum added almost simultaneously to cork boiling wastewater, leads to TOC reductions of more than 90%. PMID:16414098

  13. Teachers College Students' Conceptions about Evaporation, Condensation, and Boiling.

    ERIC Educational Resources Information Center

    Chang, Jin-Yi

    1999-01-01

    An open-ended, written test was administered to 364 students divided into four groups according to their scientific learning background at a teachers college. Results indicate that although the science-major students performed better than nonscience majors, their understanding of condensation and boiling concepts still needed to be enhanced.

  14. Marine diagenesis of hydrothermal sulfide

    SciTech Connect

    Moammar, M.O.

    1985-01-01

    An attempt is made to discuss the artificial and natural oxidation and hydrolysis of hydrothermal sulfide upon interaction with normal seawater. Synthetic and natural ferrosphalerite particles used in kinetic oxidation and hydrolysis studies in seawater develop dense, crystalline coatings consisting of ordered and ferrimagnetic delta-(Fe, Zn)OOH. Due to the formation of this reactive diffusion barrier, the release of Zn into solution decreases rapidly, and sulfide oxidation is reduced to a low rate determined by the diffusion of oxygen through the oxyhydroxide film. This also acts as an efficient solvent for ions such as Zn/sup 2 +/, Ca/sup 2 +/, and possibly Cd/sup 2 +/, which contribute to the stabilization of the delta-FeOOH structure. The oxidation of sulfide occurs in many seafloor spreading areas, such as 21/sup 0/N on the East Pacific Ridge. In these areas the old surface of the sulfide chimneys are found to be covered by an orange stain, and sediment near the base of nonactive vents is also found to consist of what has been referred to as amorphous iron oxide and hydroxide. This thesis also discusses the exceedingly low solubility of zinc in seawater, from delta-(Fe, Zn)OOH and the analogous phase (zinc-ferrihydroxide) and the zinc exchange minerals, 10-A manganate and montmorillonite. The concentrations of all four are of the same magnitude (16, 36.4, and 12 nM, respectively) as the zinc concentration in deep ocean water (approx. 10 nM), which suggests that manganates and montmorillonite with iron oxyhydroxides control zinc concentration in the deep ocean.

  15. The hydrothermal power of oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Grose, C. J.; Afonso, J. C.

    2015-03-01

    We have estimated the power of ventilated hydrothermal heat transport, and its spatial distribution, using a set of recently developed plate models which highlight the effects of hydrothermal circulation and thermal insulation by oceanic crust. Testing lithospheric cooling models with these two effects, we estimate that global advective heat transport is about 6.6 TW, significantly lower than previous estimates, and that the fraction of that extracted by vigorous circulation on the ridge axes (<1 Ma) is about 50% of the total, significantly higher than previous estimates. This low hydrothermal power estimate originates from the thermally insulating properties of oceanic crust in relation to the mantle. Since the crust is relatively insulating, the effective properties of the lithosphere are "crust dominated" near ridge axes (yielding lower heat flow), and gradually approach mantle values over time. Thus, cooling models with crustal insulation predict low heat flow over young seafloor, implying that the difference of modeled and measured heat flow is due to the heat transport properties of the lithosphere, in addition to ventilated hydrothermal circulation as generally accepted. These estimates may bear on important problems in the physics and chemistry of the Earth because the magnitude of hydrothermal power affects chemical exchanges between the oceans and the lithosphere, thereby affecting both thermal and chemical budgets in the oceanic crust and lithosphere, the subduction factory, and convective mantle.

  16. Ancient Hydrothermal Springs in Arabia Terra, Mars

    NASA Technical Reports Server (NTRS)

    Oehler, Dorothy Z.; Allen, Carlton C.

    2008-01-01

    Hydrothermal springs are important astrobiological sites for several reasons: 1) On Earth, molecular phylogeny suggests that many of the most primitive organisms are hyperthermophiles, implying that life on this planet may have arisen in hydrothermal settings; 2) on Mars, similar settings would have supplied energy- and nutrient-rich waters in which early martian life may have evolved; 3) such regions on Mars would have constituted oases of continued habitability providing warm, liquid water to primitive life forms as the planet became colder and drier; and 4) mineralization associated with hydrothermal settings could have preserved biosignatures from those martian life forms. Accordingly, if life ever developed on Mars, then hydrothermal spring deposits would be excellent localities in which to search for morphological or chemical remnants of that life. Previous attempts to identify martian spring deposits from orbit have been general or limited by resolution of available data. However, new satellite imagery from HiRISE has a resolution of 28 cm/pixel which allows detailed analysis of geologic structure and geomorphology. Based on these new data, we report several features in Vernal Crater, Arabia Terra that we interpret as ancient hydrothermal springs.

  17. Peptide synthesis in early earth hydrothermal systems

    USGS Publications Warehouse

    Lemke, K.H.; Rosenbauer, R.J.; Bird, D.K.

    2009-01-01

    We report here results from experiments and thermodynamic calculations that demonstrate a rapid, temperature-enhanced synthesis of oligopeptides from the condensation of aqueous glycine. Experiments were conducted in custom-made hydrothermal reactors, and organic compounds were characterized with ultraviolet-visible procedures. A comparison of peptide yields at 260??C with those obtained at more moderate temperatures (160??C) gives evidence of a significant (13 kJ ?? mol-1) exergonic shift. In contrast to previous hydrothermal studies, we demonstrate that peptide synthesis is favored in hydrothermal fluids and that rates of peptide hydrolysis are controlled by the stability of the parent amino acid, with a critical dependence on reactor surface composition. From our study, we predict that rapid recycling of product peptides from cool into near-supercritical fluids in mid-ocean ridge hydrothermal systems will enhance peptide chain elongation. It is anticipated that the abundant hydrothermal systems on early Earth could have provided a substantial source of biomolecules required for the origin of life. Astrobiology 9, 141-146. ?? 2009 Mary Ann Liebert, Inc. 2009.

  18. Sample Return from Ancient Hydrothermal Springs

    NASA Technical Reports Server (NTRS)

    Allen, Carlton C.; Oehler, Dorothy Z.

    2008-01-01

    Hydrothermal spring deposits on Mars would make excellent candidates for sample return. Molecular phylogeny suggests that that life on Earth may have arisen in hydrothermal settings [1-3], and on Mars, such settings not only would have supplied energy-rich waters in which martian life may have evolved [4-7] but also would have provided warm, liquid water to martian life forms as the climate became colder and drier [8]. Since silica, sulfates, and clays associated with hydrothermal settings are known to preserve geochemical and morphological remains of ancient terrestrial life [9-11], such settings on Mars might similarly preserve evidence of martian life. Finally, because formation of hydrothermal springs includes surface and subsurface processes, martian spring deposits would offer the potential to assess astrobiological potential and hydrological history in a variety of settings, including surface mineralized terraces, associated stream deposits, and subsurface environments where organic remains may have been well protected from oxidation. Previous attempts to identify martian spring deposits from orbit have been general or limited by resolution of available data [12-14]. However, new satellite imagery from HiRISE has a resolution of 28 cm/pixel, and based on these new data, we have interpreted several features in Vernal Crater, Arabia Terra as ancient hydrothermal springs [15, 16].

  19. Lander Detection and Identification of Hydrothermal Deposits

    NASA Astrophysics Data System (ADS)

    Urquhart, M. L.; Gulick, V.

    2001-01-01

    The role of hydrothermal activity on Mars in altering crustal materials and sequestering volatiles is a critical component in understanding the interactions between the atmosphere, surface, and hydrosphere of Mars. In turn, these interactions are key elements in understanding the martian climate history, surface geology, and potential for past life on Mars. Identification of hydrothermal deposits at the surface of Mars, especially within a region in which the geologic context is clear (e.g. a volcanic region such as a Apollinarius Patera), would provide valuable information about the geologic history of the planet, and would be indicative of a potential site for the search for evidence of life on Mars. Specific hydrothermal mineral assemblages will be dependent on the environmental conditions under which the country rock was altered. Mini-TES, however, has the capacity to identify a wide range of alteration products, and Mossbauer Spectrometer will be able to identify both altered and unaltered iron-bearing bearing minerals, and will yield information on the environment in which iron oxidation has occurred. The instruments on the 2003 rover will have the capability to identify hydrothermal deposits present at the surface of the landing site, potentially yielding information about the nature of the environment in which hydrothermal alteration occurred.

  20. Nucleate pool boiling heat transfer in aqueous surfactant solutions

    NASA Astrophysics Data System (ADS)

    Wasekar, Vivek Mahadeorao

    Saturated, nucleate pool boiling in aqueous surfactant solutions is investigated experimentally. Also, the role of Marangoni convection, driven both by temperature and surfactant concentration gradients at the vapor-liquid interface of a nucleating bubble is computationally explored. Experimental measurements of dynamic and equilibrium sigma using the maximum bubble pressure method indicate dynamic sigma to be higher than the corresponding equilibrium value, both at room and elevated temperatures. Also, nonionic surfactants (Triton X-100, Triton X-305) show larger sigma depression than anionic surfactants (SDS, SLES), and a normalized representation of their dynamic adsorption isotherms is shown to be helpful in generalizing the surfactant effectiveness to reduce surface tension. The dynamic sigma has a primary role in the modification of bubble dynamics and associated heat transfer, and is dictated by the adsorption kinetics of the surfactant molecules at boiling temperatures. In general, an enhancement in heat transfer is observed, which is characterized by an early incipience and an optimum boiling performance at or around the critical micelle concentration of the surfactant. The optimum performances, typically in the fully developed boiling regime ( q''w > 100 kW/m2), show a reverse trend with respect to surfactant molecular weights M, i.e., higher molecular weight additives promote lower enhancement. Normalized boiling performance using the respective solution's dynamic sigma correlates heat transfer coefficient by M-0.5 for anionics and M 0 for nonionics. This has been shown to be brought about by the surfactant concentration and its interfacial activity in a concentration sublayer around the growing vapor bubble, which governs the bubble growth behavior through the mechanism of dynamic sigma. The ionic nature of the surfactant influences the thickness and molecular makeup of the enveloping sublayer, thereby affecting the bubble dynamics and boiling heat transfer. Finally, the computational modeling of Marangoni convection for boiling nuclei at short time transients shows similarity solutions for pure water, and reduced convection with a peak in circulation strength in the presence of surfactants. The peaking corresponds to the characteristic surfactant adsorption time, which has been shown to depend solely upon the surfactant bulk concentration. For the absence of surfactant surface convection, an enhancement in Marangoni convection is observed. Furthermore, for the investigated range of parameters and time scales, the surfactant adsorption at the interface is not characterized by the presence of a stagnant cap. (Abstract shortened by UMI.)

  1. How Does Boiling in the Earth's Crust Influence Metal Speciation and Transport?

    NASA Astrophysics Data System (ADS)

    Kam, K.; Lemke, K.

    2014-12-01

    The presence of large quantities of precious metals, such as gold and copper, near the Earth's surface (upper crust) is commonly attributed to transport in aqueous solution and precipitation upon variations in temperature and pressure. As a consequence, gold exploration is closely linked to solution chemistry, i.e. hydrothermal processes involving aqueous fluids with densities of around unity. However, as crustal fluids buoyantly ascend, boiling produces a coexisting low-density aqueous liquid with fundamentally different physical and chemical properties, and a, most importantly, a high affinity for coinage metals (Heinrich et al., Econ Geol., 1992, 87, 1566). From recent experimental studies of Au (Hurtig and Williams-Jones, 2014, Geochim. Cosmochim. Acta,, 127, 304), we know that metal speciation in this low-density phase differs fundamentally from that observed in bulk solution, clearly, with important implications for Au, and metal speciation in general, transport and ore concentrations processes (these processes would also be operable in industrial geothermal plants given the quite special solvent properties of steam). In brief, this study focuses on the speciation of select metal halides in bulk solution as well as in water vapor, and is driven by our need to understand the solvent properties of around 2.0x109 cubic kilometers of free water (or 2,500 times as much water as stored in all lakes and rivers) present in the Earth's crust. The scope of this study has particular applications in the geothermal and oil industries, as both deal with high temperature low-density aqueous fluids. Understanding how metal halide species behave upon boiling can also provide insight into how metals, such as copper and silver, coat turbine equipment and steam piping in geothermal plants, ultimately rendering these components inoperable. This study will also provide preliminary results from mass spectrometric experiments of transition metal halides, and will be augmented with results from molecular simulations of metal halides that are aimed at characterizing the nature (i.e. relativistic structures and energies) of metal clusters in water vapor.

  2. A new hydrothermal scenario for the 2006 Lusi eruption, Indonesia. Insights from gas geochemistry

    NASA Astrophysics Data System (ADS)

    Mazzini, Adriano; Etiope, Giuseppe; Svensen, Henrik

    2012-02-01

    The 29th of May 2006 gas and mud eruptions suddenly appeared along the Watukosek fault in the north east of Java, Indonesia. Within a few weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. To date (November 2011) Lusi is still active and a ~ 7 km2 area is covered by the burst mud breccia. The mechanisms responsible for this devastating eruption remain elusive. While there is consensus about the origin of the erupted mud, the source of water is uncertain, the origin of the gas is unknown and the trigger of the eruption is still debated. In order to shed light on these unknowns, we acquired a wide set of data of molecular and isotopic composition of gas sampled in several Lusi vents, in the surrounding mud volcanoes, in the closest natural gas field (Wunut), and in the hydrothermal vents at the neighbouring volcanic complex in the period 2006-2011. The boiling fluids erupted in the crater zone are apparently CO2-dominated, while colder CH4-dominated and C2-C3 bearing fluids are identified at several sites around the crater zone. Gas genetic diagrams, maturity plots and gas generation modelling suggest that the hydrocarbons are thermogenic (δ13C1 up to - 35‰; δ13C2 up to - 20‰), deriving from marine kerogen with maturity of at least 1.5%Ro, for instance in the ~ 4400 m deep Ngimbang source rocks. CO2 released from the crater and surrounding seeps is also thermogenic (δ13C from - 15 to - 24‰) related to kerogen decarboxylation or thermal CH4 oxidation in deep rocks, although three vents just outside the crater showed an apparent inorganic signature (- 7.5‰ < δ13C = - 0.5‰) associated to mantle helium (R/Ra up to 6.5). High CO2-CH4 equilibrium temperatures (200-400 °C) are typical of thermally altered hydrocarbons or organic matter. The data suggest mainly thermally altered organic sources for the erupted gases, deeper sourced than the mud and water (Upper Kalibeng shales). These results are consistent with a scenario of deep seated (> 4000 m) magmatic intrusions and hydrothermal fluids responsible for the enhanced heat that altered source rocks and/or gas reservoirs. The neighbouring magmatic Arjuno complex and its fluid-pressure system combined with high seismic activity could have played a key role in the Lusi genesis and evolution. Within this new model framework, Lusi is better understood as a sediment-hosted hydrothermal system rather than a mud volcano.

  3. Hydrothermal Venting at Kick'Em Jenny Submarine Volcano (West Indies)

    NASA Astrophysics Data System (ADS)

    Carey, S.; Croff Bell, K. L.; Dondin, F. J. Y.; Roman, C.; Smart, C.; Lilley, M. D.; Lupton, J. E.; Ballard, R. D.

    2014-12-01

    Kick'em Jenny is a frequently-erupting, shallow submarine volcano located ~8 km off the northwest coast of Grenada in the West Indies. The last eruption took place in 2001 but did not breach the sea surface. Focused and diffuse hydrothermal venting is taking place mainly within a small (~100 x 100 m) depression within the 300 m diameter crater of the volcano at depths of about 265 meters. Near the center of the depression clear fluids are being discharged from a focused mound-like vent at a maximum temperature of 180o C with the simultaneous discharge of numerous bubble streams. The gas consists of 93-96% CO2 with trace amounts of methane and hydrogen. A sulfur component likely contributes 1-4% of the gas total. Gas flux measurements on individual bubble streams ranged from 10 to 100 kg of CO2 per day. Diffuse venting with temperatures 5 to 35o C above ambient occurs throughout the depression and over large areas of the main crater. These zones are extensively colonized by reddish-yellow bacterial mats with the production of loose Fe-oxyhydroxides largely as a surface coating and in some cases, as fragile spires up to several meters in height. A high-resolution photo mosaic of the crater depression was constructed using the remotely operated vehicle Hercules on cruise NA039 of the E/V Nautilus. The image revealed prominent fluid flow patterns descending the sides of the depression towards the base. We speculate that the negatively buoyant fluid flow may be the result of second boiling of hydrothermal fluids at Kick'em Jenny generating a dense saline component that does not rise despite its elevated temperature. Increased density may also be the result of high dissolved CO2 content of the fluids, although we were not able to measure this directly. The low amount of sulphide mineralization on the crater floor suggests that deposition may be occurring mostly subsurface, in accord with models of second boiling mineralization from other hydrothermal vent systems.

  4. Numerical Investigation of Microgravity Tank Pressure Rise Due to Boiling

    NASA Technical Reports Server (NTRS)

    Hylton, Sonya; Ibrahim, Mounir; Kartuzova, Olga; Kassemi, Mohammad

    2015-01-01

    The ability to control self-pressurization in cryogenic storage tanks is essential for NASAs long-term space exploration missions. Predictions of the tank pressure rise in Space are needed in order to inform the microgravity design and optimization process. Due to the fact that natural convection is very weak in microgravity, heat leaks into the tank can create superheated regions in the liquid. The superheated regions can instigate microgravity boiling, giving rise to pressure spikes during self-pressurization. In this work, a CFD model is developed to predict the magnitude and duration of the microgravity pressure spikes. The model uses the Schrage equation to calculate the mass transfer, with a different accommodation coefficient for evaporation at the interface, condensation at the interface, and boiling in the bulk liquid. The implicit VOF model was used to account for the moving interface, with bounded second order time discretization. Validation of the models predictions was carried out using microgravity data from the Tank Pressure Control Experiment, which flew aboard the Space Shuttle Mission STS-52. Although this experiment was meant to study pressurization and pressure control, it underwent boiling during several tests. The pressure rise predicted by the CFD model compared well with the experimental data. The ZBOT microgravity experiment is scheduled to fly on February 2016 aboard the ISS. The CFD model was also used to perform simulations for setting parametric limits for the Zero-Boil-Off Tank (ZBOT) Experiments Test Matrix in an attempt to avoid boiling in the majority of the test runs that are aimed to study pressure increase rates during self-pressurization. *Supported in part by NASA ISS Physical Sciences Research Program, NASA HQ, USA

  5. Modeling acid-gas generation from boiling chloride brines

    PubMed Central

    2009-01-01

    Background This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Results Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150°C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. Conclusion The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC) processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual and modeled distillation experiments do not represent expected conditions in an emplacement drift, but nevertheless illustrate the potential for acid-gas generation at moderate temperatures (<150°C). PMID:19917082

  6. Phase relations and adiabats in boiling seafloor geothermal systems

    USGS Publications Warehouse

    Bischoff, J.L.; Pitzer, Kenneth S.

    1985-01-01

    Observations of large salinity variations and vent temperatures in the range of 380-400??C suggest that boiling or two-phase separation may be occurring in some seafloor geothermal systems. Consideration of flow rates and the relatively small differences in density between vapors and liquids at the supercritical pressures at depth in these systems suggests that boiling is occurring under closed-system conditions. Salinity and temperature of boiling vents can be used to estimate the pressure-temperature point in the subsurface at which liquid seawater first reached the two-phase boundary. Data are reviewed to construct phase diagrams of coexisting brines and vapors in the two-phase region at pressures corresponding to those of the seafloor geothermal systems. A method is developed for calculating the enthalpy and entropy of the coexisting mixtures, and results are used to construct adiabats from the seafloor to the P-T two-phase boundary. Results for seafloor vents discharging at 2300 m below sea level indicate that a 385??C vent is composed of a brine (7% NaCl equivalent) in equilibrium with a vapor (0.1% NaCl). Brine constitutes 45% by weight of the mixture, and the fluid first boiled at approximately 1 km below the seafloor at 415??C, 330 bar. A 400??C vent is primarily vapor (88 wt.%, 0.044% NaCl) with a small amount of brine (26% NaCl) and first boiled at 2.9 km below the seafloor at 500??C, 520 bar. These results show that adiabatic decompression in the two-phase region results in dramatic cooling of the fluid mixture when there is a large fraction of vapor. ?? 1985.

  7. Modeling acid-gas generation from boiling chloride brines

    SciTech Connect

    Zhang, Guoxiang; Spycher, Nicolas; Sonnenthal, Eric; Steefel, Carl

    2009-11-16

    This study investigates the generation of HCl and other acid gases from boiling calcium chloride dominated waters at atmospheric pressure, primarily using numerical modeling. The main focus of this investigation relates to the long-term geologic disposal of nuclear waste at Yucca Mountain, Nevada, where pore waters around waste-emplacement tunnels are expected to undergo boiling and evaporative concentration as a result of the heat released by spent nuclear fuel. Processes that are modeled include boiling of highly concentrated solutions, gas transport, and gas condensation accompanied by the dissociation of acid gases, causing low-pH condensate. Simple calculations are first carried out to evaluate condensate pH as a function of HCl gas fugacity and condensed water fraction for a vapor equilibrated with saturated calcium chloride brine at 50-150 C and 1 bar. The distillation of a calcium-chloride-dominated brine is then simulated with a reactive transport model using a brine composition representative of partially evaporated calcium-rich pore waters at Yucca Mountain. Results show a significant increase in boiling temperature from evaporative concentration, as well as low pH in condensates, particularly for dynamic systems where partial condensation takes place, which result in enrichment of HCl in condensates. These results are in qualitative agreement with experimental data from other studies. The combination of reactive transport with multicomponent brine chemistry to study evaporation, boiling, and the potential for acid gas generation at the proposed Yucca Mountain repository is seen as an improvement relative to previously applied simpler batch evaporation models. This approach allows the evaluation of thermal, hydrological, and chemical (THC) processes in a coupled manner, and modeling of settings much more relevant to actual field conditions than the distillation experiment considered. The actual and modeled distillation experiments do not represent expected conditions in an emplacement drift, but nevertheless illustrate the potential for acid-gas generation at moderate temperatures (<150 C).

  8. The 2006 Eruption of Raoul Volcano (Kermadecs): A Phreato-magmatic Event From a Hydrothermally-Sealed Volcanic Conduit System.

    NASA Astrophysics Data System (ADS)

    Christenson, B. W.; Reyes, A. G.; Werner, C. A.

    2006-12-01

    The March 17, 2006 eruption from Raoul volcano (Kermadec Islands, NZ), which tragically claimed the life of NZ Department of Conservation staff member Mark Kearney, is being interpreted as a magmatic-hydrothermal event triggered by shaking associated with regional earthquake swarm activity. Although the eruption released ca. 200 T of SO2, thus confirming its magmatic nature, it occurred without significant precursory volcanic seismicity, and without any of the precursory responses of the volcanic hydrothermal system which were observed prior to the last eruption in 1964. Raoul Island has a long and varied eruption history dating back > 1.4 ma, and has been hydrothermally active throughout historic time. Present day fumarolic and hotspring discharges within Raoul caldera point to the existence of a small but well established, mixed meteoric - seawater hydrothermal system within the volcano. Magmatic signatures are apparent in fumarolic gas discharges, but are heavily masked by their interaction with hydrothermal system fluids (eg. near complete scrubbing of sulphur and halogen gases from the boiling point fumarolic discharges). A diffuse degassing study conducted in 2004 revealed that ca. 80 T/d CO2 is passively discharged from the volcano, suggesting that ongoing (albeit low level) convective degassing of magma occurs at depth. Interestingly, vent locations from the 2006 eruption correspond to areas of relatively low CO2 discharge on the crater floor in 2004. This, in conjunction with the preliminary findings of abundant hydrothermal mineralisation (calcite, anhydrite, quartz) in eruption ejecta, suggests that the main volcanic conduits had become effectively sealed during the interval since the last eruption. Calcite-hosted fluid inclusions are CO2 clathrate-bearing, and have relatively low homogenisation temperatures (165-180 °C), suggesting that the seal environment was both gas-charged and shallowly seated (< 200 m). Shaking associated with the regional earthquake swarm activity which commenced on March 12th is thought to have released magmatic volatiles through the plastic-brittle transition zone surrounding the magma conduit at depth. Over the subsequent 5 days, these gases migrated upward to become trapped behind the hydrothermal seal, leading to growth of a vapour-static gas cap beneath the seal, and its eventual failure through elevated pore pressures.

  9. Hydrothermal mineralization at seafloor spreading centers

    NASA Astrophysics Data System (ADS)

    Rona, Peter A.

    1984-01-01

    The recent recognition that metallic mineral deposits are concentrated by hydrothermal processes at seafloor spreading centers constitutes a scientific breakthrough that opens active sites at seafloor spreading centers as natural laboratories to investigate ore-forming processes of such economically useful deposits as massive sulfides in volcanogenic rocks on land, and that enhances the metallic mineral potential of oceanic crust covering two-thirds of the Earth both beneath ocean basins and exposed on land in ophiolite belts. This paper reviews our knowledge of processes of hydrothermal mineralization and the occurrence and distribution of hydrothermal mineral deposits at the global oceanic ridge-rift system. Sub-seafloor hydrothermal convection involving circulation of seawater through fractured rocks of oceanic crust driven by heat supplied by generation of new lithosphere is nearly ubiquitous at seafloor spreading centers. However, ore-forming hydrothermal systems are extremely localized where conditions of anomalously high thermal gradients and permeability increase hydrothermal activity from the ubiquitous low-intensity background level (? 200C) to high-intensity characterized by high temperatures ( > 200-c.400C), and a rate and volume of flow sufficient to sustain chemical reactions that produce acid, reducing, metal-rich primary hydrothermal solutions. A series of mineral phases with sulfides and oxides as high- and low-temperature end members, respectively, are precipitated along the upwelling limb and in the discharge zone of single-phase systems as a function of increasing admixture of normal seawater. The occurrence of hydrothermal mineral deposits is considered in terms of spatial and temporal frames of reference. Spatial frames of reference comprise structural features along-axis (linear sections that are the loci of seafloor spreading alternating with transform faults) and perpendicular to axis (axial zone of volcanic extrusion and marginal zones of active extension) common to all spreading centers, regional tectonic setting determined by stage (early, advanced), and rate (slow, intermediate-to-fast) of opening of an ocean basin about a spreading center, and local tectonic sub-setting that incorporates anomalous structural and thermal conditions conducive to mineral concentration (thermal gradient, permeability, system geometry, leaky versus tight hydrothermal systems). Temporal frames of reference comprise the relation between mineral concentration and timing of regional plutonic, volcanic and tectonic cycles and of episodic local physical and chemical events (transient stress, fluctuating heat transfer, intrusion-extrusion, fracturing, sealing, etc.). Types of hydrothermal deposits are not uniquely associated with specific tectonic settings and subsettings. Similar types of hydrothermal deposits may occur in different tectonic settings as a consequence of convergence of physical and chemical processes of concentration. Local tectonic sub-settings with conditions conducive to hydrothermal mineralization at slow-spreading centers (half rate ? 2cm y -1; length c. 28,000 km), characterized by an estimated average convective heat transfer of 15.110 8 cal. cm -2, deep-level ( > 3 km), relative narrow (< 5 km wide at base) magma chambers, and high topographic relief (1-5 km) are: (1) basins along linear sections of the axial zone of volcanic extrusion near transform faults at an early stage of opening, represented by a large stratiform sulfide deposit (estimated 32.510 6 metric tons) of the Atlantis II Deep of the Red Sea; (2) the wall along linear sections of the rift valley in the marginal zone of active extension at an advanced stage of opening, represented by encrustations and layered deposits of manganese and iron oxides, hydroxides and silicates inferred to be underlain by stockwork sulfides at the TAG Hydrothermal Field at latitude 26C on the Mid-Atlantic Ridge; (3) transform faults, especially those with large ridge-ridge offset ( > 30 km), at an advanced stage of opening, represented by stockwork sulfides exposed in the walls of equatorial fracture zones of the Atlantic Ocean and Indian Ocean; (4) the axial zone of volcanic extrusion at an advanced stage of opening. Local tectonic sub-settings with conditions conducive to hydrothermal mineralization at intermediate- to fast-spreading centers (half rate > 2cm y -1; length c. 22,000 km) characterized by an estimated average convective heat transfer of 11.510 8 cal. cm -2, relatively wide (up to 20 km at base), shallow-level (c. 1-3 km) magma chambers, and low topographic relief (< 1 km), are: (1) basins along linear sections of the axial zone of volcanic extrusion at an early stage of opening, represented by massive sulfide deposits of the Guaymas Basin of the Gulf of California; (2) the axial zone of volcanic extrusion at an advanced stage of opening, represented by individually small (c. 110 3 metric tons), massive sulfide mounds surmounted by chimneys of the East Pacific Rise at latitude 21N; (3) the marginal zone of active extension at an advanced stage of opening represented by a large, massive sulfide deposit (preliminary tentative estimate c.1010 6 metric tons) at a double-rifted section of the Galapagos Spreading Center; (4) transform faults, especially those with large ridge-ridge offset ( > 50 km) represented by manganese encrustations in a transform fault at the Galapagos Spreading Center; (5) volcanic seamounts related to persistent hot spots at spreading centers, represented by oxide and sulfide deposits on seamounts off the axis of the East Pacific Rise; (6) portions of spreading centers with anomalous configurations such as multiple, bent or extended rifts, represented by massive sulfide deposits at a double-rifted section of the Galapagos Spreading Center, suggesting the operation of a thermal-structural feedback mechanism indicative of the presence of hydrothermal mineralization; (7) discrete spreading centers in back-arc basins represented by hydrothermal deposits at sites in marginal seas of the western Pacific. Ore-forming processes appear to be least efficient in the axial zone of volcanic extrusion of oceanic ridges at an advanced stage of opening irrespective of spreading rate, where tight hydrothermal systems dissipate a major portion of contained metals by precipitation and dispersion in particulate form from "black smokers" that discharge into the water column. Ore-forming processes appear to be most efficient at sites in basins at linear sections of the axial zone of volcanic extrusion near transform faults during an early stage of opening, and at marginal zones of active extension along linear sections of a spreading center during an advanced stage of opening, irrespective of spreading rate, where both tight and leaky hydrothermal systems may conserve their contained metals to concentrate large sulfide deposits. Resemblances in mineralization between stockwork sulfides at seafloor spreading centers and porphyry copper-type deposits in volcanogenic rocks on land suggest the possibility for the occurrence of large tonnage, low-grade porphyry copper-like deposits concentrated by leaky hydrothermal systems at spreading centers. Systematic application of composite exploration procedures is leading to the discovery of numerous additional deposits. It is inferred from the limited data base available that the occurrence of hydrothermal mineral deposits is more frequent at intermediate-to-fast-than at slow-spreading centers, but the potential for the accumulation of large hydrothermal mineral deposits is greater at slow-spreading centers. Current knowledge of the distribution of hydrothermal mineral deposits at seafloor spreading centers is limited to about 55 sites at this early stage of exploration. Estimates of the distribution of either fields of hydrothermal mineral deposits or high-intensity ore-forming hydrothermal systems at seafloor spreading centers, deduced from various considerations, range from one such occurrence between 15 and 265 km along slow-spreading centers, and 1 and 100 km along intermediate- to fast-spreading centers. However, the distribution of sizable deposits will remain sporadic owing to the special structural and thermal conditions necessary to sustain and to retain high-intensity ore-forming hydrothermal systems.

  10. Calibrated Hydrothermal Parameters, Barrow, Alaska, 2013

    DOE Data Explorer

    Atchley, Adam; Painter, Scott; Harp, Dylan; Coon, Ethan; Wilson, Cathy; Liljedahl, Anna; Romanovsky, Vladimir

    2015-01-29

    A model-observation-experiment process (ModEx) is used to generate three 1D models of characteristic micro-topographical land-formations, which are capable of simulating present active thaw layer (ALT) from current climate conditions. Each column was used in a coupled calibration to identify moss, peat and mineral soil hydrothermal properties to be used in up-scaled simulations. Observational soil temperature data from a tundra site located near Barrow, AK (Area C) is used to calibrate thermal properties of moss, peat, and sandy loam soil to be used in the multiphysics Advanced Terrestrial Simulator (ATS) models. Simulation results are a list of calibrated hydrothermal parameters for moss, peat, and mineral soil hydrothermal parameters.

  11. Thermodynamics of Strecker synthesis in hydrothermal systems

    NASA Technical Reports Server (NTRS)

    Schulte, Mitchell; Shock, Everett

    1995-01-01

    Submarine hydrothermal systems on the early Earth may have been the sites from which life emerged. The potential for Strecker synthesis to produce biomolecules (amino and hydroxy acids) from starting compounds (ketones, aldehydes, HCN and ammonia) in such environments is evaluated quantitatively using thermodynamic data and parameters for the revised Helgeson-Kirkham-Flowers (HKF) equation of state. Although there is an overwhelming thermodynamic drive to form biomolecules by the Strecker synthesis at hydrothermal conditions, the availability and concentration of starting compounds limit the efficiency and productivity of Strecker reactions. Mechanisms for concentrating reactant compounds could help overcome this problem, but other mechanisms for production of biomolecules may have been required to produce the required compounds on the early Earth. Geochemical constraints imposed by hydrothermal systems provide important clues for determining the potential of these and other systems as sites for the emergence of life.

  12. Characterization of advanced preprocessed materials (Hydrothermal)

    SciTech Connect

    Rachel Emerson; Garold Gresham

    2012-09-01

    The initial hydrothermal treatment parameters did not achieve the proposed objective of this effort; the reduction of intrinsic ash in the corn stover. However, liquid fractions from the 170°C treatments was indicative that some of the elements routinely found in the ash that negatively impact the biochemical conversion processes had been removed. After reviewing other options for facilitating ash removal, sodium-citrate (chelating agent) was included in the hydrothermal treatment process, resulting in a 69% reduction in the physiological ash. These results indicated that chelation –hydrothermal treatment is one possible approach that can be utilized to reduce the overall ash content of feedstock materials and having a positive impact on conversion performance.

  13. Hydrothermal pretreatment of bamboo and cellulose degradation.

    PubMed

    Ma, X J; Cao, S L; Lin, L; Luo, X L; Hu, H C; Chen, L H; Huang, L L

    2013-11-01

    A systematic hydrothermal pretreatment of bamboo chips had been conducted with an aim to trace the cellulose degradation. The results showed that cellulose chain cleavage basically occurred when the temperature exceeded 150C. A slightly higher DP (degree of polymerization) than starting material had been observed at low temperature pretreatment. Treatment at higher temperature (? 170C) caused severe cleavage of cellulose and therefore gave rise to low DP with more soluble species. DP of cellulose declined drastically without additional hemicelluloses dissolution when hemicelluloses removal reached to the limit level. Cellulose degradation under hydrothermal pretreatment generally followed the zero reaction kinetics with the activity energy of 121.0 kJ/mol. Besides, the increase of cellulose crystalline index and the conversion of I?-I? had also observed at the hydrothermal pretreatment. PMID:24077149

  14. Hydrothermal processing of radioactive combustible waste

    SciTech Connect

    Worl, L.A.; Buelow, S.J.; Harradine, D.; Le, L.; Padilla, D.D.; Roberts, J.H.

    1998-09-01

    Hydrothermal processing has been demonstrated for the treatment of radioactive combustible materials for the US Department of Energy. A hydrothermal processing system was designed, built and tested for operation in a plutonium glovebox. Presented here are results from the study of the hydrothermal oxidation of plutonium and americium contaminated organic wastes. Experiments show the destruction of the organic component to CO{sub 2} and H{sub 2}O, with 30 wt.% H{sub 2}O{sub 2} as an oxidant, at 540 C and 46.2 MPa. The majority of the actinide component forms insoluble products that are easily separated by filtration. A titanium liner in the reactor and heat exchanger provide corrosion resistance for the oxidation of chlorinated organics. The treatment of solid material is accomplished by particle size reduction and the addition of a viscosity enhancing agent to generate a homogeneous pumpable mixture.

  15. Hydrothermally reduced graphene oxide as a supercapacitor

    NASA Astrophysics Data System (ADS)

    Johra, Fatima Tuz; Jung, Woo-Gwang

    2015-12-01

    The supercapacitance behavior of hydrothermally reduced graphene oxide (RGO) was investigated for the first time. The capacitive behavior of RGO was characterized by using cyclic voltammetry and galvanostatic charge-discharge methods. The specific capacitance of hydrothermally reduced RGO at 1 A/g was 367 F/g in 1 M H2SO4 electrolyte, which was higher than that of RGO synthesized via the hydrazine reduction method. The RGO-modified glassy carbon electrode showed excellent stability. After 1000 cycles, the supercapacitance was 107.7% of that achieved in the 1st cycle, which suggests that RGO has excellent electrochemical stability as a supercapacitor electrode material. The energy density of hydrothermal RGO reached 44.4 W h/kg at a power density of 40 kW/kg.

  16. Hydrothermal treatment of electric arc furnace dust.

    PubMed

    Yu, Bing-Sheng; Wang, Yuh-Ruey; Chang, Tien-Chin

    2011-06-15

    In this study, ZnO crystals were fabricated from electric arc furnace dust (EAFD) after alkaline leaching, purification and hydrothermal treatment. The effects of temperature, duration, pH, and solid/liquid ratio on ZnO crystal morphology and size were investigated. Results show a high reaction temperature capable of accelerating the dissolution of ZnO precursor, expediting the growth of 1D ZnO, and increasing the L/D ratio in the temperature range of 100-200°C. ZnO crystals with high purity can also be obtained, using the one-step hydrothermal treatment with a baffle that depends on the different solubility of zincite and franklinite in the hydrothermal conditions. PMID:21497436

  17. Hydrothermal synthesis of ytterbium silicate nanoparticles.

    PubMed

    Chen, Hongfei; Gao, Yanfeng; Liu, Yun; Luo, Hongjie

    2010-02-15

    A simple, low-cost hydrothermal method was developed to synthesize 20-nm-diameter single-crystalline ytterbium silicate (Yb(2)Si(2)O(7) and Yb(2)SiO(5)) nanoparticles at 200 degrees C. This is nearly 1000 degrees C lower than that for the typical sol-gel route to ytterbium silicate powders. Obtained powders showed very low thermal conductivity, a suitable thermal expansion coefficient, and excellent thermal/structural stability, suggesting a potential application to environmental and thermal barrier coatings. Special focus was placed on assessing the hydrothermal reaction mechanism for particle formation. PMID:20085266

  18. Hydrothermal Solidification of the Yellow River Sediments

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Zhou, L.; Ran, X.; Ishida, E. H.

    2010-11-01

    The properties of chemical and mineral compositions for the silts at upper (Yinchuan), middle (Tongguan) and lower (Zhengzhou) reaches were very similar, and moreover the heavy metals dissolved from those silts were low, below the regulatory levels for the environmental quality standards of China. The silts therefore could be used as raw materials readily and safely. A hydrothermal processing has been used to solidify the silt which is from middle reach and the results showed that during the hydrothermal process CSH gel and fine particle formation made matrix denser and thus gave an initial strength development, and tobermorite, transformed from the CSH gel, further promoted the strength development.

  19. Geothermal reservoirs in hydrothermal convection systems

    SciTech Connect

    Sorey, M.L.

    1982-01-01

    Geothermal reservoirs commonly exist in hydrothermal convection systems involving fluid circulation downward in areas of recharge and upwards in areas of discharge. Because such reservoirs are not isolated from their surroundings, the nature of thermal and hydrologic connections with the rest of the system may have significant effects on the natural state of the reservoir and on its response to development. Conditions observed at numerous developed and undeveloped geothermal fields are discussed with respect to a basic model of the discharge portion of an active hydrothermal convection system. Effects of reservoir development on surficial discharge of thermal fluid are also delineated.

  20. Zero Boil Off Cryogen Storage for Future Launchers

    NASA Technical Reports Server (NTRS)

    Valentian, D.; Plachta, D.; Kittel, P.; Hastings, L. J.; Salerno, Louis J.; Arnold, James O. (Technical Monitor)

    2001-01-01

    Zero boil off (ZBO) cryogen storage using both cryocoolers and passive insulation technologies will enable long-term exploration missions by allowing designers to optimize tankage without the need for excess cryogen storage to account for boil off. Studies of ZBO (zero boil off) have been on-going in the USA for several years. More recently, a review of the needs of advanced space propulsion took place in Europe. This showed the interest of the European community in cryogenic propulsion for planetary missions as well as the use of liquid hydrogen for large power electric propulsion (manned Mars missions). Although natural boiling could be acceptable for single leg missions, passive insulation techniques yield roughly a I% per month cryogen loss and this would not be cost effective for robotic planetary missions involving storage times greater than one year. To make economic sense, long-term exploration missions require lower tank capacity and longer storage times. Recent advances in cryocooler technology, resulting in vast improvements in both cooler efficiency and reliability, make ZBO is a clear choice for planetary exploration missions. Other, more near term applications of ZBO include boil-off reduction or elimination applied to first and upper stages of future earth-to-orbit (ETO) launchers. This would extend launch windows and reduce infrastructure costs. Successors to vehicles like Ariane 5 could greatly benefit by implementing ZBO. Zero Boil Off will only be successful in ETO launcher applications if it makes economic sense to implement. The energy cost is only a fraction of the total cost of buying liquid cryogen, the rest being transportation and other overhead. Because of this, higher boiling point cryogens will benefit more from on-board liquefaction, thus reducing the infrastructure costs. Since hydrogen requires a liquefier with at least a 17% efficiency just to break even from a cost standpoint, one approach for implementing ZBO in upper stages would be to actively cool the shield in the hydrogen tank to reduce the parasitic losses. This would allow the use of less expensive, presently available coolers (80 K vs. 20 K) and potentially simplify the system by requiring only a single compressor on the pad amd a single disconnect line. The compressor could be a hefty commercial unit, with only the cold head requiring expensive flight development and qualification. While this is actually a reduced boil off configuration rather than a zero-boil off case, if the cryogen loss could be cut significantly, the increase in hold time and reduced need for draining and refilling the propellant tanks could meet the vehicle operations needs in the majority of instances.Bearing in mind the potential benefits of ZBO, NASA AMES and SNECMA Moteurs decided to exchange their technical views on the subject. This paper will present a preliminary analysis for a multi-mission module using a fairly low thrust cryogenic engine and ZBO during cruise. Initial mass is 5.5. tons (in ETO). The cryogenic engine will be used near each periapsis in order to minimize the AV requirement. The payload obtained by this propulsion system is compared to a classical storable bipropellant propulsion system for several cases (e. g. Mars lander, Jupiter orbiter, Saturn orbiter). For the Jupiter and Saturn cases, the power source could be an RTG or a large parabolic mirror illuminating a solar panel. It is shown -that - due to its much larger specific impulse - the cryogenic ZBO solution provides much higher payloads, especially for exploration missions involving landing on planets, asteroids, comets, or other celestial bodies.

  1. Intra-field variability in microbial community associated with phase-separation-controlled hydrothermal fluid chemistry in the Mariner field, the southern Lau Basin

    NASA Astrophysics Data System (ADS)

    Takai, K.; Ishibashi, J.; Lupton, J.; Ueno, Y.; Nunoura, T.; Hirayama, H.; Horikoshi, K.; Suzuki, R.; Hamasaki, H.; Suzuki, Y.

    2006-12-01

    A newly discovered hydrothermal field called the Mariner field at the northernmost central Valu Fa Ridge (VFR) in the Lau Basin was explored and characterized by geochemical and microbiological surveys. The hydrothermal fluid (max. 365 u^C) emitting from the most vigorous vent site (Snow chimney) was boiling just beneath the seafloor at a water depth of 1908 m and two end-members of hydrothermal fluid were identified. Mineral and fluid chemistry of typical brine-rich (Snow chimney and Monk chimney) and vapor-rich (Crab Restaurant chimney) hydrothermal fluids and the host chimney structures were analyzed. Microbial community structures in three chimney structures were also investigated by culture-dependent and - independent analyses. The 16S rRNA gene clone analysis revealed that both bacterial and archaeal rRNA gene communities at the chimney surface zones were different among three chimneys. The bacterial and archaeal rRNA gene communities of the Snow chimney surface were very similar with those in the dead chimneys, suggesting concurrence of metal sulfide deposition at the inside and weathering at the surface potentially due to its large structure and size. Cultivation analysis demonstrated the significant variation in culturability of various microbial components, particularly of thermophilic H2- and/or S-oxidizing chemolithoautotrophs such as the genera Aquifex and Persephonella, among the chimney sites. The culturability of these chemolithoautotrophs might be associated with the input of gaseous energy and carbon sources like H2S, H2 and CH4 from the hydrothermal fluids, and might be affected by phase-separation- controlled fluid chemistry. In addition, inter-fields comparison of microbial community structures determined by cultivation analysis revealed novel characteristics of the microbial communities in the Mariner field of the Lau Basin among the global deep-sea hydrothermal systems.

  2. Hydrothermal brecciation in the Jemez Fault zone, Valles Caldera, New Mexico: Results from CSDP (Continental Scientific Drilling Program) corehole VC-1

    SciTech Connect

    Hulen, J.B.; Nielson, D.L.

    1987-06-01

    Paleozoic and Precambrian rocks intersected deep in Continental Scientific Drilling Program corehole VC-1, adjacent to the late Cenozoic Valles caldera complex, have been disrupted to form a spectacular breccia sequence. The breccias are of both tectonic and hydrothermal origin, and probably formed in the Jemez fault zone, a major regional structure with only normal displacement since mid-Miocene. Tectonic breccias are contorted, crushed, sheared, and granulated; slickensides are commmon. Hydrothermal breccias, by contrast, lack these frictional textures, but arej commonly characterized by fluidized matrix foliation and prominent clast rounding. Fluid inclusions in the hydrothermal breccias are dominantly two-phase, liquid-rich at room temperature, principally secondary, and form two distinctly different compositional groups. Older inclusions, unrelated to brecciation, are highly saline and homogenize to the liquid phase in the temperature range 189 to 246/sup 0/C. Younger inclusions, in part of interbreccia origin, are low-salinity and homogenize (also to liquid) in the range 230 to 283/sup 0/C. Vapor-rich inclusions locally trapped along with these dilute liquid-rich inclusions document periodic boiling. These fluid-inclusion data, together with alteration assemblages and textures as well as the local geologic history, have been combined to model hydrothermal brecciation at the VC-1 site.

  3. Biogeochemistry of hydrothermally and adjacent non-altered soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    As a field/lab project, students in the Soil Biogeochemistry class of the University of Nevada, Reno described and characterized seven pedons, developed in hydrothermally and adjacent non-hydrothermally altered andesitic parent material near Reno, NV. Hydrothermally altered soils had considerably lo...

  4. The chemistry of hydrothermal magnetite: a review

    USGS Publications Warehouse

    Nadoll, Patrick; Angerer, Thomas; Mauk, Jeffrey L.; French, David; Walshe, John

    2014-01-01

    Magnetite (Fe3O4) is a well-recognized petrogenetic indicator and is a common accessory mineral in many ore deposits and their host rocks. Recent years have seen an increased interest in the use of hydrothermal magnetite for provenance studies and as a pathfinder for mineral exploration. A number of studies have investigated how specific formation conditions are reflected in the composition of the respective magnetite. Two fundamental questions underlie these efforts — (i) How can the composition of igneous and, more importantly, hydrothermal magnetite be used to discriminate mineralized areas from barren host rocks, and (ii) how can this assist exploration geologists to target ore deposits at greater and greater distances from the main mineralization? Similar to igneous magnetite, the most important factors that govern compositional variations in hydrothermal magnetite are (A) temperature, (B) fluid composition — element availability, (C) oxygen and sulfur fugacity, (D) silicate and sulfide activity, (E) host rock buffering, (F) re-equilibration processes, and (G) intrinsic crystallographic controls such as ionic radius and charge balance. We discuss how specific formation conditions are reflected in the composition of magnetite and review studies that investigate the chemistry of hydrothermal and igneous magnetite from various mineral deposits and their host rocks. Furthermore, we discuss the redox-related alteration of magnetite (martitization and mushketovitization) and mineral inclusions in magnetite and their effect on chemical analyses. Our database includes published and previously unpublished magnetite minor and trace element data for magnetite from (1) banded iron formations (BIF) and related high-grade iron ore deposits in Western Australia, India, and Brazil, (2) Ag–Pb–Zn veins of the Coeur d'Alene district, United States, (3) porphyry Cu–(Au)–(Mo) deposits and associated (4) calcic and magnesian skarn deposits in the southwestern United States and Indonesia, and (5) plutonic igneous rocks from the Henderson Climax-type Mo deposit, United States, and the un-mineralized Inner Zone Batholith granodiorite, Japan. These five settings represent a diverse suite of geological settings and cover a wide range of formation conditions. The main discriminator elements for magnetite are Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn, and Ga. These elements are commonly present at detectable levels (10 to > 1000 ppm) and display systematic variations. We propose a combination of Ni/(Cr + Mn) vs. Ti + V, Al + Mn vs. Ti + V, Ti/V and Sn/Ga discriminant plots and upper threshold concentrations to discriminate hydrothermal from igneous magnetite and to fingerprint different hydrothermal ore deposits. The overall trends in upper threshold values for the different settings can be summarized as follows: (I) BIF (hydrothermal) — low Al, Ti, V, Cr, Mn, Co, Ni, Zn, Ga and Sn; (II) Ag–Pb–Zn veins (hydrothermal) — high Mn and low Ga and Sn; (III) Mg-skarn (hydrothermal) — high Mg and Mn and low Al, Ti, Cr, Co, Ni and Ga; (IV) skarn (hydrothermal) — high Mg, Al, Cr, Mn, Co, Ni and Zn and low Sn; (V) porphyry (hydrothermal) — high Ti and V and low Sn; (VI) porphyry (igneous) — high Ti, V and Cr and low Mg; and (VII) Climax-Mo (igneous) — high Al, Ga and Sn and low Mg and Cr.

  5. A New Theory of Nucleate Pool Boiling in Arbitrary Gravity

    NASA Technical Reports Server (NTRS)

    Buyevich, Y. A.; Webbon, Bruce W.

    1995-01-01

    Heat transfer rates specific to nucleate pool boiling under various conditions are determined by the dynamics of vapour bubbles that are originated and grow at nucleation sites of a superheated surface. A new dynamic theory of these bubbles has been recently developed on the basis of the thermodynamics of irreversible processes. In contrast to other existing models based on empirically postulated equations for bubble growth and motion, this theory does not contain unwarrantable assumptions, and both the equations are rigorously derived within the framework of a unified approach. The conclusions of the theory are drastically different from those of the conventional models. The bubbles are shown to detach themselves under combined action of buoyancy and a surface tension force that is proven to add to buoyancy in bubble detachment, but not the other way round as is commonly presumed. The theory ensures a sound understanding of a number of so far unexplained phenomena, such as effect caused by gravity level and surface tension on the bubble growth rate and dependence of the bubble characteristics at detachment on the liquid thermophysical parameters and relevant temperature differences. The theoretical predictions are shown to be in a satisfactory qualitative and quantitative agreement with observations. When being applied to heat transfer at nucleate pool boiling, this bubble dynamic theory offers an opportunity to considerably improve the main formulae that are generally used to correlate experimental findings and to design boiling heat removal in various industrial applications. Moreover, the theory makes possible to pose and study a great deal of new problems of essential impact in practice. Two such problems are considered in detail. One problem concerns the development of a principally novel physical model for the first crisis of boiling. This model allows for evaluating critical boiling heat fluxes under various conditions, and in particular at different gravity levels, with a good agreement with experimental evidence. The other problem bears upon equilibrium shapes of a detached bubble near a heated surface in exceedingly low gravity. In low gravity or in weightlessness, the bubble can remain in the close vicinity of the surface for a long time, and its shape is greatly affected by the Marangoni effect due to both temperature and possible surfactant concentration being nonuniform along the interface. The bubble performs at these conditions like a heat pipe, with evaporation at the bubble lower boundary and condensation at its upper boundary, and ultimately ensures a substantial increase in heat removal as compared with that in normal gravity. Some other problems relevant to nucleate pool and forced convection boiling heat transfer are also discussed.

  6. Boiling, colloid nucleation and aggregation, and the genesis of bonanza Au-Ag ores of the sleeper deposit, Nevada

    NASA Astrophysics Data System (ADS)

    Saunders, J. A.; Schoenly, P. A.

    1995-06-01

    A deep “parent” composition for bonanza oreforming fluids at the Sleeper deposit was calculated by the computer program SOLVEQ using fluid-inclusion microthermometric and gas data, and by assuming equilibrium with the following minerals present in vein samples below the bonanza zones: gold, chalcedony, adularia, pyrite, chalcopyrite, and acanthite. The calculated dissolved gold content of 295 ppb is approximately 2 orders of magnitude higher than that assumed for typical geothermal systems. Thus, a gold-enriched fluid appears to have been a principal factor in the genesis of bonanza Au-Ag ores at the Sleeper deposit. Geochemical modelling of possible ore-forming processes using the computer program CHILLER, with the reconstructed ore-forming solution as a starting composition, indicates that boiling most closely reproduces observed minerals and their relative abundances in bonanza ores. The constraint imposed by the association of amorphous silica with gold precludes all of the mixing scenarios modelled, such as mixing with cold and steam-heated groundwaters (acid-sulfate, CO2-rich). Modelling indicates that boiling of a gold-rich deep solution leads to rapid gold precipitation, and that the amount of gold precipitated initially is large relative to other minerals. These factors apparently led to nucleation of colloidal gold particles instead of in-situ gold deposition or coprecipitation with other phases. Gold colloids apparently were entrained in the upward-flowing hydrothermal solutions and grew as they travelled. Upon reaching a critical size (10 100 nm?), they were deposited due to orthokinetic aggregation at an elevation and temperature at which amorphous silica was nucleating and aggregating.

  7. Seismological evidence for an along-axis hydrothermal flow at the Lucky Strike hydrothermal vents site

    NASA Astrophysics Data System (ADS)

    Rai, A.; Wang, H.; Singh, S. C.; Crawford, W. C.; Escartin, J.; Cannat, M.

    2010-12-01

    Hydrothermal circulation at ocean spreading centres plays fundamental role in crustal accretion process, heat extraction from the earth and helps to maintain very rich ecosystem in deep Ocean. Recently, it has been suggested that hydrothermal circulation is mainly along the ridge axis at fast spreading centres above along axis melt lens (AMC). Using a combination of micro-earthquake and seismic reflection data, we show that the hydrothermal circulation at the Lucky Strike segment of slow spreading Mid-Atlantic Ridge is also along axis in a narrow (~1 km) zone above a wide (2-3 km) AMC. We find that the seismicity mainly lies above the seismically imaged 3 km wide 7 km long melt lens at 3.2 km depth. We observe a vertical plume of seismicity above a weak AMC reflection just north of the hydrothermal vent fields that initiates just above the AMC and continues to the seafloor. This zone is collocated with active rifting of the seafloor in the neo-volcanic zone. Beneath the hydrothermal vents sites, where a strong melt lens is imaged, the seismicity initiates at 500 m above the AMC and continues to the seafloor. Just south of the hydrothermal field, where the AMC is widest and strongest, the seismicity band lies 500 m above the melt lens in a 800 m thick zone, which does not continue to the seafloor. The presence the weak melt lens reflection could be due to a cooled and crystallised AMC (mush) that permits the penetration of hydrothermal fluids down to the top of the AMC indicated by seismicity plume and might be the in-flow zone for hydrothermal circulation. The strong AMC reflection could be due to fresh supply of melt in the AMC (pure melt), which has pushed the cracking front 500 m above the AMC. Beneath the hydrothermal fields, the strong AMC reflection and seismicity 500 above the AMC to the seafloor could represent cracking along the up-flow zone. The 800 m thick zone of seismicity above the pure melt zone could be the zone of hydrothermal cracking zone. We do not observe any seismicity along the main bounding faults. These results suggest that the hydrothermal flow is mainly along the ridge axis in a narrow zone above the AMC, even when the AMC only 7 km long.

  8. The hydrothermal power of oceanic lithosphere

    NASA Astrophysics Data System (ADS)

    Grose, C. J.; Afonso, J. C.

    2015-10-01

    We have estimated the power of ventilated hydrothermal heat transport, and its spatial distribution, using a set of recently developed plate models which highlight the effects of axial hydrothermal circulation and thermal insulation by oceanic crust. Testing lithospheric cooling models with these two effects, we estimate that global advective heat transport is about 6.6 TW, significantly lower than most previous estimates, and that the fraction of that extracted by vigorous circulation on the ridge axes (< 1 My old) is about 50 % of the total, significantly higher than previous estimates. These new estimates originate from the thermally insulating properties of oceanic crust in relation to the mantle. Since the crust is relatively insulating, the effective properties of the lithosphere are "crust dominated" near ridge axes (a thermal blanketing effect yielding lower heat flow) and gradually approach mantle values over time. Thus, cooling models with crustal insulation predict low heat flow over young seafloor, implying that the difference of modeled and measured heat flow is due to the heat transport properties of the lithosphere, in addition to ventilated hydrothermal circulation as generally accepted. These estimates may bear on important problems in the physics and chemistry of the Earth because the magnitude of ventilated hydrothermal power affects chemical exchanges between the oceans and the lithosphere, thereby affecting both thermal and chemical budgets in the oceanic crust and lithosphere, the subduction factory, and the convective mantle.

  9. Hydrothermal carbonization of municipal waste streams

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydrothermal carbonization (HTC) is a novel thermal conversion process that can be used to convert municipal waste streams into sterilized, value-added hydrochar. HTC has been mostly applied and studied on a limited number of feedstocks, ranging from pure substances to slightly more complex biomass ...

  10. Hydrothermal systems and the emergence of life

    NASA Technical Reports Server (NTRS)

    Shock, E. L.

    1994-01-01

    The author reviews current thought about life originating in hyperthermophilic microorganisms. Hyperthermophiles obtain food from chemosynthesis of sulfur and have an RNA nucleotide sequence different from bacteria and eucarya. It is postulated that a hyperthermophile may be the common ancestor of all life. Current research efforts focus on the synthesis of organic compounds in hydrothermal systems.

  11. Hydrothermal exploration with the Autonomous Benthic Explorer

    NASA Astrophysics Data System (ADS)

    German, Christopher R.; Yoerger, Dana R.; Jakuba, Michael; Shank, Timothy M.; Langmuir, Charles H.; Nakamura, Ko-ichi

    We describe a three-phase use of the Woods Hole Oceanographic Institution's Autonomous Benthic Explorer ( ABE), to locate, map and photograph previously undiscovered fields of high temperature submarine hydrothermal vents. Our approach represents both a complement to and a significant advance beyond the prior state of the art. Previously, hydrothermal exploration relied upon deep-tow instruments equipped with sensors that could locate sites of active "black smoker" venting to within a few kilometers. Follow-on CTD tow-yos could then resolve the sites of seafloor venting to length scales of less than a kilometer but rarely to better than a few hundreds of meters. In our new approach ABE: (i) uses sensors to locate the center of a dispersing non-buoyant hydrothermal plume 100-400 m above the seabed; (ii) makes high-resolution maps of the seafloor beneath the plume center whilst simultaneously detecting interception of any rising, buoyant hydrothermal plumes; and (iii) dives to the seafloor to take photographs in and around any new vent site to characterize its geologic setting and reveal the nature of any chemosynthetic ecosystems it may host. By conducting all of the above under long-baseline navigation, precise sites of venting can be determined to within 5 m. Our approach can be used both to address important scientific issues in their own right and to ensure much more efficient use of other deep-submergence assets such as human occupied vehicles (HOVs) and remotely operated vehicles (ROVs) during follow-on studies.

  12. Cooling Unit for Computer Chip by using Boiling Heat Transfer

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Kiyoshi; Terao, Tadayoshi; Kobayashi, Kazuo

    In recent years, the heating value of CPU has been increasing rapidly in proportion to the improvement of computer performance. Therefore computer industry is requiring the new cooling unit having high cooling performance for CPU adaptable to high heating value and high heat flux. In the past the cooling unit for CPU is used with air-cooling aluminum fin, but it can not be adaptable to high heating value. We have developed a new compact boiling refrigerant type cooling unit for CPU having high cooling performance in comparing with air-cooling aluminum fin. This paper described the cooling performance and pressure drop characteristics of the boiling refrigerant type cooling unit for CPU. The characteristics were clarified by testing the cooling unit under various test conditions, which were different Reynolds number, various sizes of cooling unit and various inclination angles. Furthermore the equations to predict cooling performance and pressure drop which are necessary on design of the cooling unit were proposed.

  13. (Severe accident technology of BWR (Boiling Water Reactor) reactors)

    SciTech Connect

    Ott, L.J.

    1989-10-23

    The traveler attended the 1989 CORA Workshop at KfK, FRG. Participation included the presentation included the presentation of three papers on work performed by the Boiling Water Reactor Severe Accident Technology (BWRSAT) program at Oak Ridge National Laboratory (ORNL) in Boiling Water Reactor (BWR) severe accident analyses. The Statement of Work (June 1989) for the BWRSAT Program provides for code analyses of the BWR CORA experiments performed at KfK. Additionally, it is intended that BWRSAT personnel participate in the planning process for future CORA BWR experiments. For these purposes, meetings were held with KfK staff to arrange for acquisition of detailed CORA facility drawings, experimental data, and related engineering. 17 refs.

  14. Numerical analysis of contaminant removal from fractured rock during boiling.

    PubMed

    Chen, Fei; Falta, Ronald W; Murdoch, Lawrence C

    2012-06-01

    A multiphase heat transfer numerical model is used to simulate a laboratory experiment of contaminant removal at boiling temperatures from a rock core representing the matrix adjacent to a fracture. The simulated temperature, condensate production, contaminant and bromide concentrations are similar to experimental data. A key observation from the experiment and simulation is that boiling out approximately 1/2 pore volume (50 mL) of water results in the removal of essentially 100% of the dissolved volatile contaminant (1,2-DCA). A field-scale simulation using the multiple interacting continua (MINC) discretization approach is conducted to illustrate possible applications of thermal remediation of fractured geologic media, assuming uniform heating. The results show that after 28% of the pore water (including both steam vapor and liquid water) was extracted, and essentially all the 1,2-DCA mass (more than 99%) was removed. PMID:22579665

  15. Critical heat flux maxima during boiling crisis on textured surfaces

    PubMed Central

    Dhillon, Navdeep Singh; Buongiorno, Jacopo; Varanasi, Kripa K.

    2015-01-01

    Enhancing the critical heat flux (CHF) of industrial boilers by surface texturing can lead to substantial energy savings and global reduction in greenhouse gas emissions, but fundamentally this phenomenon is not well understood. Prior studies on boiling crisis indicate that CHF monotonically increases with increasing texture density. Here we report on the existence of maxima in CHF enhancement at intermediate texture density using measurements on parametrically designed plain and nano-textured micropillar surfaces. Using high-speed optical and infrared imaging, we study the dynamics of dry spot heating and rewetting phenomena and reveal that the dry spot heating timescale is of the same order as that of the gravity and liquid imbibition-induced dry spot rewetting timescale. Based on these insights, we develop a coupled thermal-hydraulic model that relates CHF enhancement to rewetting of a hot dry spot on the boiling surface, thereby revealing the mechanism governing the hitherto unknown CHF enhancement maxima. PMID:26346098

  16. Characteristics of Pool Boiling on Graphite-Copper Composite Surfaces

    NASA Technical Reports Server (NTRS)

    Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

    2002-01-01

    Nucleate pool boiling performance of different liquids on graphite-copper composite (Gr-Cu) surfaces has been experimentally studied and modeled. Both highly wetting fluids, such as freon-113 and pentane, and a moderately wetting fluid (water) were tested on the Gr-Cu surfaces with different graphite-fiber volume fractions to reveal the enhancement effects of the composite surfaces on the nucleate pool boiling. Results of the experiments show that the graphite-fiber volume fraction has an optimum value. The Gr-Cu composite surface with 25 percent graphite-fiber volume (f=0.25) has a maximum enhancement effect on the nucleate boiling heat transfer comparing to the pure copper surface. For the highly wetting fluid, the nucleate boiling heat transfer is generally enhanced on the Gr- Cu composite surfaces by 3 to 6 times shown. In the low heat flux region, the enhancement is over 6 times, but in the high heat flux region, the enhancement is reduced to about 40%. For the moderately wetting fluid (water), stronger enhancement of nucleate boiling heat transfer is achieved on the composite surface. It shown the experimental results in which one observes the nucleate boiling heat transfer enhancement of 5 to 10 times in the low heat flux region and an enhancement of 3 to 5 times in the high heat flux region. Photographs of bubble departure during the initial stage of nucleate boiling indicate that the bubbles detached from the composite surface are much smaller in diameter than those detached from the pure copper surface. Typical photographs are presented.It shows that the bubbles departed from the composite surface have diameters of only O(0.1) mm, while those departed from the pure copper surface have diameters of O(1) mm. It is also found that the bubbles depart from the composite surface at a much higher frequency, thus forming vapor columns. These two phenomena combined with high thermal conductivity of the graphite fiber are considered the mechanisms for such a significant augmentation in nucleate boiling heat transfer on the composite surfaces. A physical model is developed to describe the phenomenon of bubble departure from the composite surface: The preferred site of bubble nucleation is the fiber tip because of higher tip temperature than the surrounding copper base and poor wettability of the graphite tip compared with that of the base material (copper). The high evaporation rate near the contact line produces the vapor cutback due to the vapor recoil pushing the three-phase line outwards from the fiber tip, and so a neck of the bubble is formed near the bubble bottom. Evaporation and surface tension accelerate the necking process and finally result in the bubble departure while a new small bubble is formed at the tip when the surface tension pushes the three-phase line back to the tip. The process is schematically shown. The proposed model is based on and confirmed by experimental results.

  17. Critical heat flux maxima during boiling crisis on textured surfaces.

    PubMed

    Dhillon, Navdeep Singh; Buongiorno, Jacopo; Varanasi, Kripa K

    2015-01-01

    Enhancing the critical heat flux (CHF) of industrial boilers by surface texturing can lead to substantial energy savings and global reduction in greenhouse gas emissions, but fundamentally this phenomenon is not well understood. Prior studies on boiling crisis indicate that CHF monotonically increases with increasing texture density. Here we report on the existence of maxima in CHF enhancement at intermediate texture density using measurements on parametrically designed plain and nano-textured micropillar surfaces. Using high-speed optical and infrared imaging, we study the dynamics of dry spot heating and rewetting phenomena and reveal that the dry spot heating timescale is of the same order as that of the gravity and liquid imbibition-induced dry spot rewetting timescale. Based on these insights, we develop a coupled thermal-hydraulic model that relates CHF enhancement to rewetting of a hot dry spot on the boiling surface, thereby revealing the mechanism governing the hitherto unknown CHF enhancement maxima. PMID:26346098

  18. Critical heat flux maxima during boiling crisis on textured surfaces

    NASA Astrophysics Data System (ADS)

    Dhillon, Navdeep Singh; Buongiorno, Jacopo; Varanasi, Kripa K.

    2015-09-01

    Enhancing the critical heat flux (CHF) of industrial boilers by surface texturing can lead to substantial energy savings and global reduction in greenhouse gas emissions, but fundamentally this phenomenon is not well understood. Prior studies on boiling crisis indicate that CHF monotonically increases with increasing texture density. Here we report on the existence of maxima in CHF enhancement at intermediate texture density using measurements on parametrically designed plain and nano-textured micropillar surfaces. Using high-speed optical and infrared imaging, we study the dynamics of dry spot heating and rewetting phenomena and reveal that the dry spot heating timescale is of the same order as that of the gravity and liquid imbibition-induced dry spot rewetting timescale. Based on these insights, we develop a coupled thermal-hydraulic model that relates CHF enhancement to rewetting of a hot dry spot on the boiling surface, thereby revealing the mechanism governing the hitherto unknown CHF enhancement maxima.

  19. 15. RW Meyer Sugar Mill: 18761889. Sorghum pan and boiling ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    15. RW Meyer Sugar Mill: 1876-1889. Sorghum pan and boiling range flue. Manufactured by John Nott & Co., Honolulu, Hawaii, 1878. View: North side of sorghum pan and boiling range flue, with furnace-end in background. In the sorghum pan heat was applied to the cane juice to clarify it, evaporate its water content, and concentrate the sugar crystals. Hot gasses moved through the flue underneath the entire copper bottom of the sorghum pan from the furnace end (in background) to the smokestack end (in foreground). After the hot cane juice moved through the separate compartments until it reached the final compartment (now missing two sides) where it was drawn out from the copper lip in the corner. - R. W. Meyer Sugar Mill, State Route 47, Kualapuu, Maui County, HI

  20. Acoustic measurement of boiling instabilities in a solar receiver

    SciTech Connect

    Beattie, A. G.

    1980-11-01

    An acoustic technique was developed and used to search for boiling instabilities in the prototype receiver for the Barstow 10 MW Solar Thermal Pilot Plant. Instabilities, consisting of movements of the transition zone between regions of nucleate and film boiling, were observed. The periods of these fluctuations ranged between three and fifteen seconds with no indications of preferred frequencies. The peak to peak amplitudes of the fluctuations averaged 0.4 meters under steady state conditions at absorbed power levels between 2.0 and 3.2 MW. Transient fluctuations with amplitudes up to 2.0 meters were also seen. These transients usually lasted between 30 and 300 seconds. It was not possible to pinpoint the causes of these transients.

  1. Numerical analysis of contaminant removal from fractured rock during boiling

    NASA Astrophysics Data System (ADS)

    Chen, Fei; Falta, Ronald W.; Murdoch, Lawrence C.

    2012-06-01

    A multiphase heat transfer numerical model is used to simulate a laboratory experiment of contaminant removal at boiling temperatures from a rock core representing the matrix adjacent to a fracture. The simulated temperature, condensate production, contaminant and bromide concentrations are similar to experimental data. A key observation from the experiment and simulation is that boiling out approximately 1/2 pore volume (50 mL) of water results in the removal of essentially 100% of the dissolved volatile contaminant (1,2-DCA). A field-scale simulation using the multiple interacting continua (MINC) discretization approach is conducted to illustrate possible applications of thermal remediation of fractured geologic media, assuming uniform heating. The results show that after 28% of the pore water (including both steam vapor and liquid water) was extracted, and essentially all the 1,2-DCA mass (more than 99%) was removed.

  2. The Biogeochemistry of Sulfur in Hydrothermal Systems

    NASA Technical Reports Server (NTRS)

    Schulte, Mitchell; Rogers, K. L.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. The incorporation of sulfur into many biomolecules likely dates back to the development of the earliest metabolic strategies. Sulfur is common in enzymes and co-enzymes and is an indispensable structural component in many peptides and proteins. Early metabolism may have been heavily influenced by the abundance of sulfide minerals in hydrothermal systems. Understanding how sulfur became prevalent in biochemical processes and many biomolecules requires knowledge of the reaction properties of sulfur-bearing compounds. We have previously estimated thermodynamic data for thiols, the simplest organic sulfur compounds, at elevated temperatures and pressures. If life began in hydrothermal environments, it is especially important to understand reactions at elevated temperatures among sulfur-bearing compounds and other organic molecules essential for the origin and persistence of life. Here we examine reactions that may have formed amino acids with thiols as reaction intermediates in hypothetical early Earth hydrothermal environments. (There are two amino acids, cysteine and methionine, that contain sulfur.) Our calculations suggest that significant amounts of some amino acids were produced in early Earth hydrothermal fluids, given reasonable concentrations H2, NH3, H2S and CO. For example, preliminary results indicate that glycine activities as high as 1 mmol can be reached in these systems at 100 C. Alanine formation from propanethiol is also a favorable reaction. On the other hand, the calculated equilibrium log activities of cysteine and serine from propanethiol are -21 and -19, respectively, at 100 C. These results indicate that while amino acid formation with thiols as intermediates is favored in some cases, other mechanisms may have been necessary to produce significant amounts of other amino acids. Coupled with our previous results for thiols, these studies imply that sulfur may have been easily incorporated into the organic geochemistry of early Earth hydrothermal systems, leading to its widespread use in biomolecules. Formation of more complex biomolecules in hydrothermal systems may have required sulfur-bearing organic compounds as reaction intermediates.

  3. A review on saturated boiling of liquids on tube bundles

    NASA Astrophysics Data System (ADS)

    Swain, Abhilas; Das, Mihir Kumar

    2014-05-01

    A review of recent investigation on boiling of saturated liquids over plain and enhanced tube bundles has been carried out taking the earlier review works as reference point. The experimental observations of various geometry and performance parameters studied by researchers are analyzed keeping current demand of industries in design and development of compact, efficient heat exchanging devices. The study shows that tube spacing plays an important role in determination of compactness of the heat exchanger.

  4. Characteristics of slush and boiling methane and methane mixtures.

    NASA Technical Reports Server (NTRS)

    Sindt, C. F.; Ludtke, P. R.

    1971-01-01

    Methane gas of two purities, 99.97% and 99%, was condensed to study the characteristics of the boiling liquid and the slush. In addition, binary mixtures of nitrogen and methane, and those of ethane and methane, and propane and methane, were also studied. Potential advantages of these gases when employed as fuels for high-performance aircraft, rocket engines, and motor vehicles are emphasized.

  5. Evaluation of boiled potato peel as a wound dressing.

    PubMed

    Dattatreya, R M; Nuijen, S; van Swaaij, A C; Klopper, P J

    1991-08-01

    In a series of experiments full thickness skin defects in 68 rats were covered with dressings made of boiled potato peels according to the method developed in Bombay. The wounds closed within 14 days and histologically complete repair of epidermis was found. The cork layer of the potato peel prevents dehydration of the wound and protects against exogenous agents. Experiments with homogenates revealed that a complete structure of the peel is necessary. Steroidal glycosides may have contributed to the favourable results. PMID:1930669

  6. Effect of Running Parameters on Flow Boiling Instabilities in Microchannels.

    PubMed

    Zong, Lu-Xiang; Xu, Jin-Liang; Liu, Guo-Hua

    2015-04-01

    Flow boiling instability (FBI) in microchannels is undesirable because they can induce the mechanical vibrations and disturb the heat transfer characteristics. In this study, the synchronous optical visualization experimental system was set up. The pure acetone liquid was used as the working fluid, and the parallel triangle silicon microchannel heat sink was designed as the experimental section. With the heat flux ranging from 0-450 kW/m2 the microchannel demand average pressure drop-heater length (Δp(ave)L) curve for constant low mass flux, and the demand pressure drop-mass flux (Δp(ave)G) curve for constant length on main heater surface were obtained and studied. The effect of heat flux (q = 188.28, 256.00, and 299.87 kW/m2), length of main heater surface (L = 4.5, 6.25, and 8.00 mm), and mass flux (G = 188.97, 283.45, and 377.94 kg/m2s) on pressure drops (Ap) and temperatures at the central point of the main heater surface (Twc) were experimentally studied. The results showed that, heat flux, length of the main heater surface, and mass flux were identified as the important parameters to the boiling instability process. The boiling incipience (TBI) and critical heat flux (CHF) were early induced for the lower mass flux or the main heater surface with longer length. With heat flux increasing, the pressure drops were linearly and slightly decreased in the single liquid region but increased sharply in the two phase flow region, in which the flow boiling instabilities with apparent amplitude and long period were more easily triggered at high heat flux. Moreover, the system pressure was increased with the increase of the heat flux. PMID:26353523

  7. The Isolated Bubble Regime in Pool Nucleate Boiling

    NASA Technical Reports Server (NTRS)

    Buyevich, Y. A.; Webbon, Bruce W.; Callaway, Robert (Technical Monitor)

    1995-01-01

    We consider an isolated bubble boiling regime in which vapour bubbles are intermittently produced at a prearranged set of nucleation site on an upward facing overheated wall plane. In this boiling regime, the bubbles depart from the wall and move as separate entities. Except in the matter of rise velocity, the bubbles do not interfere and are independent of one another. However, the rise velocity is dependent on bubble volume concentration in the bulk. Heat transfer properties specific to this regime cannot be described without bubble detachment size, and we apply our previously developed dynamic theory of vapour bubble growth and detachment to determine this size. Bubble growth is presumed to be thermally controlled. Two limiting cases of bubble evolution are considered: the one in which buoyancy prevails in promoting bubble detachment and the one in which surface tension prevails. We prove termination of the isolated regime of pool nucleate boiling to result from one of the four possible causes, depending on relevant parameters values. The first cause consists in the fact that the upward flow of rising bubbles hampers the downward liquid flow, and under certain conditions, prevents the liquid from coming to the wall in an amount that would be sufficient to compensate for vapour removal from the wall. The second cause is due to the lateral coalescence of growing bubbles that are attached to their corresponding nucleation sites, with ensuing generation of larger bubbles and extended vapour patches near the wall. The other two causes involve longitudinal coalescence either 1) immediately in the wall vicinity, accompanied by the establishment of the multiple bubble boiling regime, or 2) in the bulk, with the formation of vapour columns. The longitudinal coalescence in the bulk is shown to be the most important cause. The critical wall temperature and the heat flux density associated with isolated bubble regime termination are found to be functions of the physical and operating parameters and are discussed in detail.

  8. Hydrothermal systems in small ocean planets.

    PubMed

    Vance, Steve; Harnmeijer, Jelte; Kimura, Jun; Hussmann, Hauke; Demartin, Brian; Brown, J Michael

    2007-12-01

    We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system-for example, high or low temperature system or chemically driven system. As radiogenic heating diminishes over time, progressive exposure of new rock continues to the current epoch. Where fluid-rock interactions propagate slowly into a deep brittle layer, thermal energy from serpentinization may be the primary cause of hydrothermal activity in small ocean planets. We show that the time-varying hydrostatic head of a tidally forced ice shell may drive hydrothermal fluid flow through the seafloor, which can generate moderate but potentially important heat through viscous interaction with the matrix of porous seafloor rock. Considering all presently known potential ocean planets-Mars, a number of icy satellites, Pluto, and other trans-neptunian objects-and applying Earth-like material properties and cooling rates, we find depths of circulation are more than an order of magnitude greater than in Earth. In Europa and Enceladus, tidal flexing may drive hydrothermal circulation and, in Europa, may generate heat on the same order as present-day radiogenic heat flux at Earth's surface. In all objects, progressive serpentinization generates heat on a globally averaged basis at a fraction of a percent of present-day radiogenic heating and hydrogen is produced at rates between 10(9) and 10(10) molecules cm(2) s(1). PMID:18163874

  9. Wire deposition by a laser-induced boiling front

    NASA Astrophysics Data System (ADS)

    Torkamany, Mohammad Javad; Kaplan, Alexander F. H.; Ghaini, F. Malek; Vänskä, Mikko; Salminen, Antti; Fahlström, Karl; Hedegård, Joakim

    2015-06-01

    In laser materials processing the addition of material by wire is an option for techniques like laser welding, laser cladding or rapid prototyping. The stability of the wire deposition is strongly dependent on the wire interaction with the laser beam. For leading position wire feeding, high speed imaging was applied to study the melt transfer from the wire tip to the workpiece during keyhole welding. The observations revealed that a very stable concave processing front forms at the wire tip. A boiling front is established as an extension of the keyhole and the melt film at the front is sheared downwards by the ablation pressure of boiling. The deposition of the molten wire into the weld zone is smooth and controllable. Various wire front geometries and melt transitions are compared for different parameters. The option of laterally oscillating the laser beam is investigated and the interaction mechanism involved is discussed. Wire deposition by inducing a boiling front is explained here for the first time, which should promote future applications use of this very promising technique.

  10. Transient boiling in two-phase helium natural circulation loops

    NASA Astrophysics Data System (ADS)

    Furci, H.; Baudouy, B.; Four, A.; Meuris, C.

    2014-01-01

    Two-phase helium natural circulation loops are used for cooling large superconducting magnets, as CMS for LHC. During normal operation or in the case of incidents, transients are exerted on the cooling system. Here a cooling system of this type is studied experimentally. Sudden power changes are operated on a vertical-heated-section natural convection loop, simulating a fast increase of heat deposition on magnet cooling pipes. Mass flow rate, heated section wall temperature and pressure drop variations are measured as a function of time, to assess the time behavior concerning the boiling regime according to the values of power injected on the heated section. The boiling curves and critical heat flux (CHF) values have been obtained in steady state. Temperature evolution has been observed in order to explore the operating ranges where heat transfer is deteriorated. Premature film boiling has been observed during transients on the heated section in some power ranges, even at appreciably lower values than the CHF. A way of attenuating these undesired temperature excursions has been identified through the application of high enough initial heating power.

  11. Electrical control and enhancement of boiling heat transfer during quenching

    NASA Astrophysics Data System (ADS)

    Shahriari, Arjang; Hermes, Mark; Bahadur, Vaibhav

    2016-02-01

    Heat transfer associated with boiling degrades at elevated temperatures due to the formation of an insulating vapor layer at the solid-liquid interface (Leidenfrost effect). Interfacial electrowetting (EW) fields can disrupt this vapor layer to promote liquid-surface wetting. We experimentally analyze EW-induced disruption of the vapor layer and measure the resulting enhanced cooling during the process of quenching. Imaging is employed to visualize the fluid-surface interactions and understand boiling patterns in the presence of an electrical voltage. It is seen that EW fields fundamentally change the boiling pattern, wherein a stable vapor layer is replaced by intermittent wetting of the surface. Heat conduction across the vapor gap is thus replaced with transient convection. This fundamental switch in the heat transfer mode significantly accelerates cooling during quenching. An order of magnitude increase in the cooling rate is observed, with the heat transfer seen approaching saturation at higher voltages. An analytical model is developed to extract voltage dependent heat transfer rates from the measured cooling curve. The results show that electric fields can alter and tune the traditional cooling curve. Overall, this study presents an ultralow power consumption concept to control the mechanical properties and metallurgy, by electrically tuning the cooling rate during quenching.

  12. Increasing Boiling Heat Transfer using Low Conductivity Materials

    PubMed Central

    Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew

    2015-01-01

    We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches. PMID:26281890

  13. Pool Boiling Enhancement on Textured Surfaces using Acoustic Actuation

    NASA Astrophysics Data System (ADS)

    Boziuk, Thomas; Smith, Marc; Glezer, Ari

    2015-11-01

    Boiling heat transfer on submerged textured heated surfaces is enhanced using ultrasound actuation. The heated surface is textured using an array of open microchannels that advantageously separate the nucleation sites on the surface and inhibit the transition to film boiling, which significantly increases the critical heat flux compared to a smooth surface of the same planform dimensions. The present investigation shows that the formation and evolution of vapor bubbles on the heated surface can be substantially altered by a highly directional ultrasound (1.7 MHz) beam, and leads to significant enhancement in heat transfer, including reduced surface superheat and increased critical heat flux (exceeding 55%). The effects of the beam incidence and azimuthal angle on vapor formation, advection, and resulting effect on surface superheat are investigated experimentally in a liquid test cell. Heat transfer enhancement characterized by changes in the boiling curve (i.e., superheat and CHF) varies with surface texturing and is also dependent on acoustic beam orientation relative to the surface texture pattern.

  14. Increasing Boiling Heat Transfer using Low Conductivity Materials

    NASA Astrophysics Data System (ADS)

    Mahamudur Rahman, Md; Pollack, Jordan; McCarthy, Matthew

    2015-08-01

    We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches.

  15. Fungal colonization of an Ordovician impact-induced hydrothermal system

    NASA Astrophysics Data System (ADS)

    Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan

    2013-12-01

    Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown hydrothermal minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the hydrothermal activity and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that hydrothermal systems associated with impact structures can support colonization by microbial life.

  16. Fungal colonization of an Ordovician impact-induced hydrothermal system

    PubMed Central

    Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan

    2013-01-01

    Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown hydrothermal minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the hydrothermal activity and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that hydrothermal systems associated with impact structures can support colonization by microbial life. PMID:24336641

  17. Fungal colonization of an Ordovician impact-induced hydrothermal system.

    PubMed

    Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormö, Jens; Siljeström, Sandra; van Zuilen, Mark; Bengtson, Stefan

    2013-01-01

    Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown hydrothermal minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the hydrothermal activity and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that hydrothermal systems associated with impact structures can support colonization by microbial life. PMID:24336641

  18. Cinnabar, arsenian pyrite and thallium-enrichment in active shallow submarine hydrothermal vents at Paleochori Bay, Milos Island, Greece

    NASA Astrophysics Data System (ADS)

    Kati, Marianna; Voudouris, Panagiotis; Valsami-Jones, Eugenia; Magganas, Andreas; Baltatzis, Emmanouil; Kanellopoulos, Christos; Mavrogonatos, Constantinos

    2015-04-01

    We herein report the discovery of active cinnabar-depositing hydrothermal vents in a submarine setting at Paleochori Bay, within the offshore southeastern extension of the Milos Island Geothermal Field, South Aegean Active Volcanic Arc. Active, low temperature (up to 115 °C) hydrothermal venting through volcaniclastic material has led to a varied assemblage of sulfide and alteration mineral phases in an area of approximately 1 km2. Our samples recovered from Paleochori Bay are hydrothermal edifices composed of volcaniclastic detrital material cemented by pyrite, or pure sulfide (mainly massive pyrite) mounts. Besides pyrite and minor marcasite, the hydrothermal minerals include cinnabar, amorphous silica, hydrous ferric oxides, carbonates (aragonite and calcite), alunite-jarosite solid solution and Sr-rich barite. Among others, growth textures, sieve-textured pyrite associated with barite, alunite-jarosite solid solution and hydrous ferric oxides rims colloform-banded pyrite layers. Overgrowths of arsenian pyrite layers (up to 3.2 wt. % As and/or up to 1.1 wt. % Mn) onto As-free pyrite indicate fluctuation in As content of the hydrothermal fluid. Mercury, in the form of cinnabar, occurs in up to 5 μm grains within arsenian pyrite layers, usually forming distinct cinnabar-enriched micro-layers. Hydrothermal Sr-rich barite (barite-celestine solid solution), pseudocubic alunite-jarosite solid solution and Mn- and Sr-enriched carbonates occur in various amounts and closely associated with pyrite and/or hydrous ferric oxides. Thallium-bearing sulfides and/or sulfosalts were not detected during our study; however, hydrous ferric oxides show thallium content of up to 0.5 wt. % Tl. The following scenarios may have played a role in pyrite precipitation at Paleochori: (a) H2S originally dissolved in the deep fluid but separated upon boiling could have reacted with oxygenated seawater under production of sulphuric acid, thus causing leaching and dissolution of primary iron-rich grains from the volcaniclastic components of the sediments and resulting in precipitation of pyrite; (b) the iron may also have been derived by the near-neutral reduced hydrothermal brines and precipitate metal sulfides as a result of cooling, mixing with seawaters; the necessary iron content to form sulfides is mostly derived from primary iron-rich components of the basement; (c) biological activity may have resulted in pyrite deposition (e.g. sulfur is provided by a biogenic reduction of marine sulphate). The mineralogy of hydrothermal precipitates considered in the present study resemble hydrothermal products from other shallow water venting areas elsewhere: Lihir and Ambitle Islands, Papua New Guinea, Kraternaya Bight, Kuriles, Russia, Punta Mita and Bahía Concepción, Mexico and Punta Banda at Baja California. The Paleochori vents contain the first documented occurrence of cinnabar on the sea floor in the Aegean area and provide an important link between offshore hydrothermal activity and the mercury-depositing mineralizing system on Milos Island. An interplay between bacterial activity, pH, Eh, temperature, precipitation rate and iron concentration resulted in precipitation of As-pyrite with interlayered cinnabar, hydrous ferric oxides enriched in thallium, alunite-jarosite solid solution and carbonates.

  19. Hydrothermal Activity on ultraslow Spreading Ridge: new hydrothermal fields found on the Southwest Indian ridge

    NASA Astrophysics Data System (ADS)

    Tao, C.; Li, H.; Deng, X.; Lei, J.; Wang, Y.; Zhang, K.; Zhou, J.; Liu, W.

    2014-12-01

    Ultraslow spreading ridge makes up about 25% of global mid-ocean ridge length. Previous studies believed that hydrothermal activity is not widespread on the ultraslow spreading ridge owing to lower magma supply. Southwest Indian ridge (SWIR) with the spreading rate between 1.2cm/a to 1.4cm/a, represents the ultraslow spreading ridge. In 2007, Chinese Cruise (CC) 19th discovered the Dragon Flag deposit (DFD) on the SWIR, which is the first active hydrothermal field found on the ultraslow spreading ridge. In recent years, over 10 hydrothermal fields have been found on the SWIR between Indomed and Gallieni transform faults by the Chinese team. Tao et al. (2012) implied that the segment sections with excess heat from enhanced magmatism and suitable crustal permeability along slow and ultraslow ridges might be the most promising areas for searching for hydrothermal activities. In 2014, CC 30thdiscovered five hydrothermal fields and several hydrothermal anomalies on the SWIR. Dragon Horn Area (DHA). The DHA is located on the southern of segment 27 SWIR, with an area of about 400 km2. The geophysical studies indicated that the DHA belongs to the oceanic core complex (OCC), which is widespread on the slow spreading ridges (Zhao et al., 2013). The rocks, such as gabbro, serpentinized peridotite, and consolidated carbonate were collected in the DHA, which provide the direct evidence with the existence of the OCC. However, all rock samples gathered by three TV-grab stations are basalts on the top of the OCC. A hydrothermal anomaly area, centered at 49.66°E,37.80° S with a range of several kms, is detected in the DHA. It is probably comprised of several hydrothermal fields and controlled by a NW fault. New discovery of hydrothermal fields. From January to April 2014, five hydrothermal fields were discovered on the SWIR between 48°E to 50°E during the leg 2&3 of the CC 30th, which are the Su Causeway field (48.6°E, 38.1°S), Bai Causeway field (48.8°E, 37.9 °S), Dragon Well West field (49.6°E, 37.8°S), Dragon Well East field (49.8°E, 37.8°S), and Landing Stage field (51.0°E, 37.5°S), respectively.

  20. Rheological properties and structural changes in different sections of boiled abalone meat

    NASA Astrophysics Data System (ADS)

    Xin, Gao; Zhixu, Tang; Zhaohui, Zhang; Hiroo, Ogawa

    2003-04-01

    Changes in tissue structures, rheological properties of cross- and vertical section boiled abalone meat were studied in relation to boiling time. The adductor muscle of abalone Haliotis discus which was removed from the shell, was boiled for 1, 2, and 3 h, respectively. Then it was cut up and separated into cross- and vertical section meat. When observed by a light microscope and a scanning electron microscope, structural changes in the myofibrils were greatest in the cross section meat compared with the vertical section meat. When boiling time was increased from 1 h to 3 h, the instantaneous modulus E 0 and rupture strength of both section meat decreased gradually with increased boiling time, and no significant differences were observed between these two section meat for the same boiling time. When boiled for 1 h, the relaxation time of cross section meat was much longer than that of vertical section meat. There were no significant changes in the relaxation time of vertical section for different boiling time, but the relaxation time of cross section meat was reduced gradually with increasing boiling time. These results confirmed that the difference in rheological properties between the cross- and vertical section meat was mainly due to the denaturation level of myofibrils when heated for 1 h, as well as due to the changes in the amount of denatured proteins, and the manner in which the inner denatured protein components were exchanged after boiling time was increased from 1 h to 3 h.

  1. Hydrothermal Convection in Europa's Silicate Mantle

    NASA Astrophysics Data System (ADS)

    Palguta, J.; Travis, B. J.; Schubert, G.

    2007-12-01

    Observations by the Galileo spacecraft have shown that Europa likely possesses a liquid water ocean beneath a solid icy outer shell although the depth to the top of the ocean and its thickness remain unknown. The ice shell thickness has important implications for the formation of chaotic terrain and the accessibility of the ocean to future exploration. Hydrothermal plumes have been suggested as a possible mechanism for thinning the ice shell and facilitating the formation of chaotic terrain. The plumes could transport heat from Europa's silicate mantle to the ice shell and possibly melt through the ice. We present new numerical simulations of hydrothermal circulation in the silicate mantle and ocean of Europa that allow us to quantify its impact on overall heat transport and the global ice shell thickness. The processes in our models are hydrothermal convection in the mantle and ocean, thermal diffusion in the core and mantle, parameterized thermal diffusion to account for enhanced heat transfer in the ocean and ice layer, radiogenic heating in the rocky mantle, latent heat of melting/freezing, and tidal heating in the ice shell. Our models start with a differentiated Europa. We select a reasonable value of 750 km for the radius of Europa's metallic core. The silicate mantle extends from the top of the metallic core to a radius of 1465 km. The ocean is approximately 100 km thick and is surrounded by a thin ice shell. The metallic core and silicate mantle have an initial conductive temperature profile appropriate for Europa immediately after differentiation. Our model assumes that tidal heating starts much later than hydrothermal convection. Consequently, hydrothermal convection is not initially aided by tidal heating. The convective pattern is established within a few tens of million years; thereafter a fairly steady state is reached for a few billion years. During this time the ocean thickness is reduced to roughly 50-60 km. However, as a consequence of hydrothermal convection, heating at the base of the ice is spatially heterogeneous and variations in ice shell thickness that directly correlate with the hydrothermal plumes are maintained. Tidal dissipative heating starts around 4 Gyr when the Laplace resonance between Io, Europa, and Ganymede likely formed. The ice shell thins to about 20 km, corresponding to an ocean thickness of 80 km. This process is complete in 20-30 Myr. Additionally, the topographic variations initially present in the ice shell decrease and the ice becomes much more uniform once tidal heating starts. Over time, there is a gradual loss of energy, but the interior is very warm and has high heat content, so the overall dynamical activity decreases only very gradually. Our model indicates that it would be difficult to completely melt through the ice shell. However, even without tidal heating, hydrothermal convection is able to maintain an ocean through most of Europa's history. Additionally, hydrothermal convection promotes the transport of salt from the silicate mantle to the ice shell. The transport of salt through convective flow leads to the formation of a brine layer at the bottom of the ice shell due to exclusion of salt upon freezing. The average salt concentration at the base of the ice is significantly higher than in the bulk of the ocean. Convection within the ice shell will likely be affected by the presence of a brine layer at its base.

  2. Boiling and Evaporation on Micro/nanoengineered Surfaces

    NASA Astrophysics Data System (ADS)

    Dai, Xianming

    Two-phase transport is widely used in energy conversion and storage, energy efficiency and thermal management. Surface roughness and interfacial wettability are two major impact factors for two-phase transport. Micro/nanostructures play important roles in varying the surface roughness and improving interfacial wettability. In this doctoral study, five types of micro/nanoengineered surfaces were developed to systematically study the impacts of interfacial wettability and flow structures on nucleate boiling and capillary evaporation. These surfaces include: 1) superhydrophilic atomic layer deposition (ALD) coatings; 2) partially hydrophobic and partially hydrophilic composite interfaces; 3) micromembrane-enhanced hybrid wicks; 4) superhydrophilic micromembrane-enhnaced hybrid wicks, and 5) functionalized carbon nanotube coated micromembrane-enhnaced hybrid wicks. Type 1 and 2 surfaces were developed to investigate the impacts of intrinsic superhydrophilicity and hydrophobic-hydrophilic composite wettability on nucleate boiling. Superhydrophilicity was achieved by depositing nano-thick ALD TiO 2 coatings, which were used to enable intrinsically superhydrophilic boiling surfaces on the microscale copper woven meshes. Critical heat flux (CHF) was substantially increased because of the superwetting property and delayed local dryout. Carbon nanotube (CNT) enabled partially hydrophobic and partially hydrophilic interfaces were developed to form ideal cavities for nucleate boiling. The hydrophobic-hydrophilic composite interfaces were synthesized from functionalized multiwall carbon nanotubes (FMWCNTs) by introducing hydrophilic functional groups on the surfaces of pristine MWCNTs. The nanoscale FMWCNTs with heterogeneous wettabilities were coated on the micromeshes to form hierarchical surfaces, which effectively increase the heat transfer coefficient (HTC) and CHF of pool boiling. To enhance capillary evaporation, micromembrane-enhanced capillary evaporating surfaces, i.e., type 3 surfaces, were developed to separate liquid flows and capillary pressure generation. This new type of surfaces consists of a microchannel array and a micromembrane made from a single layer of micromesh. The capillary evaporation CHF were substantially increased because of the increased capillary pressure provided by micromeshes and the reduced friction drag resulted from microchannels. Based on this newly developed hybrid wick, the effect of interfacial wettability on capillary evaporation was systematically studied. Firstly, superhydrophilic ALD SiO2 was deposited on this type of hybrid wick to create intrinsically superhydrophilic interfaces, i.e., type 4 surfaces, resulting in significantly increased HTC because of the enhanced thin film evaporation on micromeshes. Secondly, CNT-enabled hydrophobic-hydrophilic composite interfaces were deposited on the hybrid wicks to increase the nucleate site density, bubble departure frequency and reduce friction drag. Both nucleate boiling and thin film evaporation were improved, resulting in enhanced HTC and CHF. In conclusion, the interfacial wettability of micro/nanoengineered surfaces can significantly alter bubble dynamics such as nucleation site density, bubble departure diameter and frequency. Superhydrophilic surface can substantially increase the boiling CHF because of the superwetting property. In addition, more hydrophobic surfaces yield higher HTC, while more hydrophilic surfaces result in higher CHF. The partially hydrophobic and partially hydrophilic surfaces perform better than both superhydrphobic and superhydrophilic surfaces. The separation of liquid flow and capillary pressure generation can be achieved using micromembranes, resulting in dramatically increased CHF. Improved wettability can result in better wettings and enhanced thin film evaporation. Hydrophobic and hydrophilic nanoporous coatings can improve the wetting and reduce the friction, resulting in enhanced HTC and CHF simultaneously.

  3. Hydrothermal pretreatment of coal. [Heat and hydrothermal treatment at 350 degrees C

    SciTech Connect

    Ross, D.S.

    1990-05-30

    We recently examined Argonne supplied Wyodak coal under both thermal (no added water, under N{sub 2}) and hydrothermal (liquid water present, under N{sub 2}) conditions at 350{degrees}C for periods of 30 min. and 5 hr. We found that the coal produces a tar that is deposited on the reactor insert walls solely at hydrothermal conditions. The shift from 30 min. to 5 hr. yields a tar that is more volatile and has a slightly increased molecular weight. The coals recovered from thermal and hydrothermal treatments are different by pyrolysis-field ionization mass spectrometry (py-FIMS). Specifically, the hydrothermal condition yields py-FIMS volatiles with a higher weight average molecular weight and greater volatility. They are thus less polar, a conclusion consistent with other py-FIMS data showing that the volatiles from the hydrothermally treated coal are lower in phenolics. Our results show that the phenols and catechols in the coal behave very differently. Our data are consistent with a scheme in which the catechol units in the coal engage in condensation at thermal conditions, probably through a catalyzed process related to acidic sites on the mineral matter. The phenols in contrast are unreactive. At hydrothermal conditions, on the other hand, both are released hydrolytically. Thus it appears that the presence of added water decreases or eliminates thermally promoted crosslinking tied to catechol condensation. Unexpectedly, we see acetone and other simple ketones in the Wyodak pyrolysate from both the thermal and hydrothermal treatment. Acetone in some cases is the single most prominent product. These ketones are not seen, however, in the unconfined py-FIMS heating. The difference between confined and unconfined heating suggest that water evolved from the coal itself in confined heating acts in some hydrolytic fashion to liberate the ketones.

  4. Using Hydrothermal Plumes and Their Chemical Composition to Identify and Understand Hydrothermal Activity at Explorer Ridge

    NASA Astrophysics Data System (ADS)

    Resing, J.; Lebon, G.; Baker, E.; Walker, S.; Nakamura, K.; Silvers, B.

    2002-12-01

    During June and July, 2002, an extensive survey of the hydrothermal systems of the Explorer Ridge was made aboard the R/V Thomas Thompson. This survey employed hydrocasts and the Autonomous Benthic Explorer (ABE) to locate and map hydrothermal vent fields. A total of 28 hydrocasts (17 verticals and 11 tow-yos) were used to search for hydrothermal activity from 49.5°N to 50.3°N on the Explorer Ridge. During the hydrocasts continuous measurements were made of conductivity, temperature, pressure, light backscatter, eH, Fe, Mn, and pH. Discrete samples were collected for total dissolved Fe and Mn, methane, pH, total CO2, and particulate matter. Most of the strong hydrothermal venting was near the Magic Mountain area of the Explorer Ridge at ~49.76° N, 130.26° W, where strong particulate backscatter signals (~0.130 NTUs) and moderate temperature anomalies (~ 0.05 °C) were detected. The particulate matter causing the backscatter was made up primarily of volatile particulate sulfur (PS) with little to no hydrothermal PFe. PS:PFe ratios exceeded 25 in the areas of most intense venting, . These PFe and PS data suggest that the hydrothermal Fe, if any, is deposited as sulfide minerals beneath the sea floor and that S is far in excess of Fe in the hydrothermal fluids. In the most intense plumes,total dissolvable Fe and Mn were between 20 and 30 nM, pH anomalies exceeded 0.025 pH units (indicating an increase of ~10uM CO2), and methane reached 16nM. These results suggest that the fluids exiting the sea floor are metal-poor and moderately gas-rich.

  5. Evidence for Hydrothermal Vents as "Biogeobatteries" (Invited)

    NASA Astrophysics Data System (ADS)

    Nielsen, M. E.; Girguis, P. R.

    2010-12-01

    Hydrothermal vents are unique systems that play an important role in oceanic biogeochemical cycles. As chemically reduced hydrothermal fluid mixes with cold oxic seawater, minerals precipitate out of solution resulting in chimney structures composed largely of metal sulfides and anhydrite. Pyrite, which is a natural semi-conductor, is the primary sulfide mineral, but other minerals within chimneys are also conductive (e.g. chalcopyrite, wurtzite, and some iron oxides). Sulfide chimneys are also known to host an extensive endolithic microbial community. Accordingly, submarine hydrothermal systems appear to be examples of biogeobatteries, wherein conductive mineral assemblages span naturally occuring redox gradients and enable anaerobic microbes to access oxygen as an oxidant via extracellular electron transfer (or EET). To test this hypothesis, we ran a series of electrochemical laboratory experiments in which pyrite was used as an anode (in a vessel flushed with hydrothermal-like fluid). When placed in continuity with a carbon fiber cathode, pyrite was found to accept and conduct electrons from both abiotic and biological processes (microbial EET). Specifically, electrical current increased 4-fold (5 nA/m2 to 20 nA/m2) in response to inoculation with a slurry prepared from a hydrothermal vent sample. Inspection of the pyrite anode with SEM revealed ubiquitous coverage by microbes. DNA was extracted from the anodes and the inoculum, and was subjected to pyrosequencing to examine prokaryotic diversity. These data suggest that key microbial phylotypes were enriched upon the pyrite, implicating them in EET. In addition, we deployed an in situ experiment based on microbial fuel cell architecture with a graphite anode inserted into a vent wall coupled to a carbon fiber cathode outside the vent. We observed current production over the course of one year, implying microbial EET in situ. Via pyrosequencing, we observed that the microbial community on the anode was significantly enriched in gammaproteobacteria (with respect to the community on an inert substrate deployed in the same vent, which was dominated by epsilonproteobacteria). The observation of electrical current and the enrichment of distinct microbial communities in both laboratory and in situ experiments provide evidence that hydrothermal vents enable microbes capable of EET to access molecular oxygen in the surrounding seawater as an oxidant. This geochemical and microbial phenomenon may influence the chemistry and mineralogy of vent systems, resulting in localized variations in pH that can influence metal mobilization on a global scale.

  6. A Novel Role of Three Dimensional Graphene Foam to Prevent Heater Failure during Boiling

    NASA Astrophysics Data System (ADS)

    Ahn, Ho Seon; Kim, Ji Min; Park, Chibeom; Jang, Ji-Wook; Lee, Jae Sung; Kim, Hyungdae; Kaviany, Massoud; Kim, Moo Hwan

    2013-06-01

    We report a novel boiling heat transfer (NBHT) in reduced graphene oxide (RGO) suspended in water (RGO colloid) near critical heat flux (CHF), which is traditionally the dangerous limitation of nucleate boiling heat transfer because of heater failure. When the heat flux reaches the maximum value (CHF) in RGO colloid pool boiling, the wall temperature increases gradually and slowly with an almost constant heat flux, contrary to the rapid wall temperature increase found during water pool boiling. The gained time by NBHT would provide the safer margin of the heat transfer and the amazing impact on the thermal system as the first report of graphene application. In addition, the CHF and boiling heat transfer performance also increase. This novel boiling phenomenon can effectively prevent heater failure because of the role played by the self-assembled three-dimensional foam-like graphene network (SFG).

  7. Whole Algae Hydrothermal Liquefaction Technology Pathway

    SciTech Connect

    Biddy, Mary J.; Davis, Ryan; Jones, Susanne B.; Zhu, Yunhua

    2013-03-31

    In support of the Bioenergy Technologies Office, the National Renewable Energy Laboratory (NREL) and the Pacific Northwest National Laboratory (PNNL) are undertaking studies of biomass conversion technologies to hydrocarbon fuels to identify barriers and target research toward reducing conversion costs. Process designs and preliminary economic estimates for each of these pathway cases were developed using rigorous modeling tools (Aspen Plus and Chemcad). These analyses incorporated the best information available at the time of development, including data from recent pilot and bench-scale demonstrations, collaborative industrial and academic partners, and published literature and patents. This pathway case investigates the feasibility of using whole wet microalgae as a feedstock for conversion via hydrothermal liquefaction. Technical barriers and key research needs have been assessed in order for the hydrothermal liquefaction of microalgae to be competitive with petroleum-derived gasoline, diesel and jet range blendstocks.

  8. Iridium material for hydrothermal oxidation environments

    DOEpatents

    Hong, Glenn T.; Zilberstein, Vladimir A.

    1996-01-01

    A process for hydrothermal oxidation of combustible materials in which, during at least a part of the oxidation, corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises iridium, iridium oxide, an iridium alloy, or a base metal overlaid with an iridium coating. Iridium has been found to be highly resistant to environments encountered in the process of hydrothermal oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 800.degree. C.

  9. Hydrothermal gold mineralization in the Witwatersrand basin

    NASA Astrophysics Data System (ADS)

    Barnicoat, A. C.; Henderson, I. H. C.; Knipe, R. J.; Yardley, B. W. D.; Napier, R. W.; Fox, N. P. C.; Kenyon, A. K.; Muntingh, D. J.; Strydom, D.; Winkler, K. S.; Lawrence, S. R.; Cornford, C.

    1997-04-01

    The origin of the gold mineralization in the Witwaterstrand basin of South Africa-the largest known gold province-has been controversial for decades, with arguments favouring detrital1,2 (placer), modified placer3,4 and hydrothermal5,6 origins. Here we present the results of an extensive geological study of Witwatersrand rocks which show that the gold (and associated uranium) mineralization is hydrothermal in origin and postdates a regional high-temperature alteration event. Alteration processes identified on a small scale can be mapped out regionally as roughly strata-bound zones of acid metasomatism extending far into the basin: the fluid flow responsible for this alteration was concentrated in small-scale structures localized along lithological boundaries. We find that the gold precipitated as a consequence of interactions of the fluid with shale-derived hydrocarbons present within the basin.

  10. Hydrothermal phase transformation of hematite to magnetite

    PubMed Central

    2014-01-01

    Different phases of iron oxide were obtained by hydrothermal treatment of ferric solution at 200°C with the addition of either KOH, ethylenediamine (EDA), or KOH and EDA into the reaction system. As usually observed, the α-Fe2O3 hexagonal plates and hexagonal bipyramids were obtained for reaction with KOH and EDA, respectively. When both KOH and EDA were added into the reaction system, we observed an interesting phase transformation from α-Fe2O3 to Fe3O4 at low-temperature hydrothermal conditions. The phase transformation involves the formation of α-Fe2O3 hexagonal plates, the dissolution of the α-Fe2O3 hexagonal plates, the reduction of Fe3+ to Fe2+, and the nucleation and growth of new Fe3O4 polyhedral particles. PMID:24940172

  11. Colorado's hydrothermal resource base: an assessment

    SciTech Connect

    Pearl, R.H.

    1981-01-01

    As part of its effort to more accurately describe the nations geothrmal resource potential, the US Department of Energy/Division of Geothermal Energy contracted with the Colorado Geological survey to appraise the hydrothermal (hot water) geothermal resources of Colorado. Part of this effort required that the amount of energy that could possibly be contained in the various hydrothermal systems in Colorado be estimated. The findings of that assessment are presented. To make these estimates the geothermometer reservoir temperatures estimated by Barrett and Pearl (1978) were used. In addition, the possible reservoir size and extent were estimated and used. This assessment shows that the total energy content of the thermal systems in Colorado could range from 4.872 x 10{sup 15} BTU's to 13.2386 x 10{sup 15} BTU's.

  12. Effluent from diffuse hydrothermal venting. 1: A simple model of plumes from diffuse hydrothermal sources

    SciTech Connect

    Trivett, D.A.

    1994-09-01

    This paper focuses on modeling the fate of effluent from diffuse seafloor hydrothermal activity after it has been vented into the water column. The model was formulated using a number of simplifying assumptions which permit direct application of this model to field measurements. I have limited the configurations to those where the hydrothermal outflow velocities are smaller than horizontal current. I assume that the entrainment of ambient seawater into the plume is constant over the length of the plume. This permits formulation of a first-order relation for the rise height and dilution in a diffuse hydrothermal plume as a function of downstream distance. The analytic model is compared with a simple laboratory simulation of the hydrothermal flow. The results suggest that diffuse hydrothermal effluent will penetrate to a height in the water column that is proportional to the overall dimension of the diffuse vent patch, multiplied by a dimensionless plume intensity parameter. I also ahow relations for plume dilution which will be compared with field data in part 2 of this work.