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1

Aspects of subcooled boiling  

SciTech Connect

Subcooled boiling boiling refers to boiling from a solid surface where the bulk liquid temperature is below the saturation temperature (subcooled). Two classes are considered: (1) nucleate boiling, where, for large subcoolings, individual bubbles grow and collapse while remaining attached to the solid wall, and (2) film boiling, where a continuous vapor film separates the solid from the bulk liquid. One mechanism by which subcooled nucleate boiling results in very large surface heat transfer coefficient is thought to be latent heat transport within the bubble, resulting from simultaneous evaporation from a thin residual liquid layer at the bubble base, and condensation at the polar bubble cap. Another is the increased liquid microconvection around the oscillating bubble. Two related problems have been attacked. One is the rupture of a thin liquid film subject to attractive and repulsive dispersion forces, leading to the formation of mesoscopic drops, which then coalesce and evaporate. Another is the liquid motion in the vicinity of an oscillating contact line, where the bubble wall is idealized as a wedge of constant angle sliding on the solid wall. The subcooled film boiling problem has been attacked by deriving a general long-range nonlinear evolution equation for the local thickness of the vapor layer. Linear and weakly-nonlinear stability results have been obtained. A number of other related problems have been attacked.

Bankoff, S.G. [Northwestern Univ., Evanston, IL (United States)

1997-12-31

2

Subcooled Flow Boiling and Condensation  

Microsoft Academic Search

Fundamental problems in two different flow regimes; subcooled water-steam bubbly condensing flow and subcooled flow boiling, in vertical conduits under low pressure and mass flux conditions, were investigated.\\u000aFor subcooled water-steam condensing bubbly flow, experiments were carried out to obtain a data base for the axial distribution of area-averaged void fraction, interfacial area concentration, interfacial condensation heat transfer and bubble

Obida M. Zeitoun

1994-01-01

3

Subcooled flow boiling and condensation  

Microsoft Academic Search

Fundamental problems in two different flow regimes, subcooled water-steam bubbly condensing flow and subcooled flow boiling, in vertical conduits under low pressure and mass flux conditions, were investigated.^ For subcooled water-steam condensing bubbly flow, experiments were carried out to obtain a database for the axial distribution of area-averaged void fraction, interfacial area concentration, interfacial condensation heat transfer and bubble relative

Obida M Zeitoun

1995-01-01

4

Subcooled flow boiling of fluorocarbons  

E-print Network

A study was conducted of heat transfer and hydrodynamic behavior for subcooled flow boiling of Freon-113, one of a group of fluorocarbons suitable for use in cooling of high-power-density electronic components. Problems ...

Murphy, Richard Walter

1971-01-01

5

Investigation of Subcooled Hydrothermal Boiling in Ground Water Flow Channels as a Source of Harmonic Tremors: Annual Report.  

National Technical Information Service (NTIS)

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...

1989-01-01

6

Local subcooled flow boiling model development  

SciTech Connect

Several existing heat transfer models for uniformly heated channels were examined to accurately represent the boiling curve and to characterize 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. Because the slope of the boiling curve in this region is important to ensure 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 overall percent standard deviations with respect to the data were 19 and 3%, respectively, for the high-velocity water data. 14 refs., 3 figs., 3 tabs.

Boyd, R.D.; Meng, X. [Prairie View A& M Univ., TX (United States)

1996-07-01

7

Calcium sulphate scale formation during subcooled flow boiling  

Microsoft Academic Search

Fouling of heat transfer surfaces during subcooled flow boiling is a frequent engineering problem in process industries. Nevertheless, only few experimental and theoretical investigations on this subject can be found in the literature. In this investigation the effect of operating parameters on the deposition of calcium sulphate on heat transfer surface during subcooled flow boiling was studied. A large number

S. H. Najibi; H. Müller-Steinhagen; M. Jamialahmadi

1997-01-01

8

Heat Transfer For Subcooled Flow Boiling In Hypervapotron Configuration  

SciTech Connect

This work reports on experimental studies that examine subcooled boiling on the enhanced heat transfer surface of hypervapotron structures. The use of simulant fluid (refrigerant R134a) instead of prototypic water allows examination of a full range of subcooled boiling, including up to critical heat flux (CHF). The experimental results are compared to Bjorge's model and Kandlikar's heat transfer correlation in the subcooled boiling region. It is found that the fully developed boiling curve has a slope of about 2.96 (q{sup {approx}} {delta}{sub sat} {sup 2}.{sup 96}), which shows good agreement with Bjorge's recognition for flat surface channels. In addition, Kandlikar's correlation is also able to predict the heat transfer coefficient for the range from net vapor generation (NVG) to the fully developed boiling region with acceptable accuracy. However, the heat transfer curve shows a significant deviation when subcooled boiling approaches CHF. (authors)

Chena, Peipei; Wua, Wen; Jonesa, Barclay G. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana Champaign Urbana, IL, 61801 (United States); Newell, Ty A [Mechanical and Industrial Engineering, University of Illinois at Urbana Champaign Urbana, IL, 61801 (United States)

2006-07-01

9

Subcooled Boiling Near a Heated Wall  

Microsoft Academic Search

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

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

2000-01-01

10

On the mechanism of forced-convection subcooled nucleate boiling  

Microsoft Academic Search

In highly subcooled nucleate boiling the bubbles grow and collapse while sliding along the heated surface, so that there is no net vapor transport away from the surface. A long-standing question exists as to whether conduction and convection between the bubbles, or latent heat transport through the bubbles, is the dominant heat transfer mechanism. It is shown here by simple

G. Tsung-Chang; S. G. Bankoff

1990-01-01

11

The origin of thermocapillary convection in subcooled nucleate pool boiling  

Microsoft Academic Search

The significance of noncondensibles as the origin of thermocapillary convection in subcooled pool boiling is demonstrated in this paper. The temperature gradients along the bubble interface inducing thermocapillary convection are caused by saturation pressure gradients due to a nonuniform accumulation of noncondensable gas along the interface. On the vapour side, the noncondensable gas inhibits the condensation of vapour. The corresponding

R. Marek; J. Straub

2001-01-01

12

Subcooled Boiling Near a Heated Wall  

SciTech Connect

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.

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

2000-10-27

13

Effects of turbulence and secondary flows on subcooled flow boiling  

NASA Astrophysics Data System (ADS)

Experiments are conducted on the influence of turbulence and longitudinal vortices on subcooled flow boiling in a vertical, rectangular channel. Different flow inserts are used to create turbulence and vortices in the channel. Studied boiling regimes range from the onset of nucleate boiling over the critical heat flux up to fully developed film boiling. A wide range of measuring techniques is applied: time averaged particle image velocimetry (PIV) is used in cold flows for the evaluation of the effects the inserts have on the flow, high speed PIV and photography are used to determine the effects on the fluid and vapor movement in boiling experiments. Digital Holographic Interferometry is used for the evaluation of temperature distributions in the boiling flow. Furthermore, optical microprobes are used to obtain pointwise measurements in areas inaccessible to the imaging techniques. The experiments show that the flow inserts can have considerable impact on the heat fluxes and the distribution of vapor and temperature along the channel. All used inserts lead to an increase in critical heat flux, which is more pronounced for stronger turbulence and higher flow rates and fluid subcoolings. The measuring techniques reveal both a better transport of vapor from the heater surface as well as an increase in mixing in the liquid phase with flow inserts.

Bloch, Gregor; Sattelmayer, Thomas

2014-03-01

14

Subcooled nucleate boiling heat transfer from a large diameter tube  

SciTech Connect

Nucleate boiling heat transfer from the outside of large-diameter tubes has not been well studied. There are many large-diameter horizontal tubes in the core of a CANDU{reg_sign} nuclear reactor, and it is important to quantify the different modes of heat transfer from the tubes (known as calandria tubes) to the heavy water moderator. This paper describes a series of experiments performed to study nucleate boiling heat transfer from the outside surface of a horizontal calandria tube to subcooled and pressurized light water. When the circulating pump was on, it caused an upflow of water in the vicinity of the tube, estimated to be an average of 0.3 m/s. The flow cooled the tube and increased the surface temperature fluctuations, in contrast to the relatively steady temperatures observed by Dowlati and Byrne (1995) in a test section of similar diameter, but made from a solid copper block. The cooling effect of the pumped flow was the greatest for high subcooling, low heat flux and high pressure. The magnitudes of these fluctuations are explained in terms of transient heat conduction when the surface alternates between nucleation and cooling by the cold liquid. The heat transfer from the bottom of the tube was modelled by a combination of pool boiling, global single-phase natural convection and stagnation-point single-phase forced-convection correlations. The experiments showed that Rohsenow`s pool boiling correlation (with a single-phase free convection component) successfully modelled the outer surface temperatures on the large-diameter horizontal tube when the circulating pump was off. Even at high water subcooling (60 C) and low heat flux (200 kW/m{sup 2}), nucleate boiling dominated the heat transfer.

Brown, M.J. [Atomic Energy of Canada Limited, Whiteshell, Manitoba (Canada). Whiteshell Labs.; Fung, K.K. [Ontario Hydro Nuclear, Toronto, Ontario (Canada); Byrne, T.P. [Ontario Hydro Technologies, Toronto, Ontario (Canada)

1996-12-31

15

A dry-spot model of critical heat flux applicable to both pool boiling and subcooled forced convection boiling  

SciTech Connect

A study has been performed to predict CHF in pool boiling and subcooled forced convection boiling using the dry-spot model presented by the authors and existing correlations for heat transfer coefficient, active site density and bubble departure diameter in nucleate boiling. Comparisons of the model predictions with experimental data for pool boiling of water and subcooled upward forced convection boiling of water in vertical, uniformly-heated round tubes have been performed and the parametric trends of CHF have been investigated. The results of the present study strongly support the validity of physical feature of the present model on the CHF mechanism in pool boiling and subcooled forced convection boiling. To improve the prediction capability of the present model, further works on active site density, bubble departure diameter and suppression factor in subcooled boiling are needed.

Ha, S.J.; No, H.C.

1999-07-01

16

Experimental data on the mechanism of subcooled water boiling: high-speed video shooting  

NASA Astrophysics Data System (ADS)

The article provides statistical data on the characteristics of subcooled liquid boiling and behavior of vapor and air bubbles resulted from high-speed shooting. The authors have described a number of new phenomena going along with water boiling.

Zeigarnik, Yu. A.; Khodakov, K. A.; Shekhter, Yu. L.

2014-06-01

17

Void fraction predictions in forced convective subcooled boiling of water between 10 and 18 MPa  

Microsoft Academic Search

Forced convective subcooled boiling is of interest for many industrial applications, especially as a possible heat transfer regime in the core of pressurized water reactors (PWR). Due to practical interest, R12 was used as a testing fluid to simulate water between 10 and 18 MPa. This article presents a study of the forced convective subcooled boiling of R12 based on

J. M. Delhaye; F. Maugin; J. M. Ochterbeck

2004-01-01

18

Wall heat flux partitioning during subcooled forced flow film boiling of water on a vertical surface  

Microsoft Academic Search

Subcooled flow film boiling experiments were conducted on a vertical flat plate, 30.5cm in height, and 3.175cm wide with forced convective upflow of subcooled water at atmospheric pressure. Data have been obtained for mass fluxes ranging from 0 to 700kg\\/m2s, inlet subcoolings ranging from 0 to 25°C and wall superheats ranging from 200 to 400°C. Correlations for wall heat transfer

Phani K. Meduri; Gopinath R. Warrier; Vijay K. Dhir

2009-01-01

19

Thermal interaction effect on nucleation site distribution in subcooled boiling  

SciTech Connect

An experimental work on subcooled boiling of refrigerant, R134a, to examine nucleation site distributions on both copper and stainless steel heating surfaces was performed. In order to obtain high fidelity active nucleation site density and distribution data, a high-speed digital camera was utilized to record bubble emission images from a view normal to heating surfaces. Statistical analyses on nucleation site data were done and their statistical distributions were obtained. Those experimentally observed nucleation site distributions were compared to the random spatial Poisson distribution. The comparisons showed that, rather than purely random, active nucleation site distributions on boiling surfaces are relatively more uniform. Experimental results also showed that on the copper heating surface, nucleation site distributions are slightly more uniform than on the stainless steel surface. This was concluded as the results of thermal interactions between nucleation sites with different solid thermal conductivities. A two dimensional thermal interaction model was then developed to quantitatively examine the thermal interactions between nucleation sites. The results give a reasonable explanation to the experimental observation on nucleation site distributions.

Ling Zou; Barclay Joned

2012-05-01

20

Assessment of RETRAN-3D Boiling Models Against Experimental Subcooled Boiling Tube Data  

SciTech Connect

Subcooled and saturated nucleate boiling are important physical processes in boiling water reactors (BWRs) under operating and transient conditions and in pressurized water reactors (PWRs) under transient conditions. Good predictions of such processes by system codes such as RETRAN-3D are, therefore, important from a safety and operational point of view.For this reason, and continuing the validation efforts carried out in the STARS Project at Paul Scherrer Institute, data from experiments in a uniformly heated tube carried out by Bartolomey et al. have been used to assess the subcooled and saturated nucleate boiling models in RETRAN-3D. These experiments were performed at high ({approx}15-MPa) and medium ({approx}7-, 4-, and 3-MPa) pressures. The heat flux (2210 to 420 kW/m{sup 2}) and mass flux (2123 to 405 kg/s m{sup 2}) were selected to cover a range of values spanning operating and transient situations in both BWRs and PWRs.This paper reports on the results obtained with both the four- and five-equation RETRAN-3D flow models. The results show that both models used in RETRAN-3D provide good estimates of subcooled and saturated nucleate boiling in heated tubes. The four-equation model, which makes use of the Electric Power Research Institute void fraction profile fitting model for the reactivity feedback only, shows the best performance for high mass fluxes, whereas the five-equation model, which directly computes the vaporization rate, performs better at low mass fluxes and relatively high heat fluxes.In addition to the results from RETRAN-3D, results obtained with the system code RELAP-5 are included in the plots and used to support the conclusions and to perform a comparative analysis of the methods used by the codes.

Macian, Rafael; Coddington, Paul; Stangroom, Paul [Paul Scherrer Institute (Switzerland)

2003-04-15

21

Numerical simulation of bubble departure in subcooled pool boiling based on non-empirical boiling and condensation model  

NASA Astrophysics Data System (ADS)

In this study, in order to clarify the heat transfer characteristics of the subcooled boiling phenomena and to discuss on their mechanism, a non-empirical boiling and condensation model for numerical simulation has been adopted. This model consists of an improved phase-change model and a consideration of a relaxation time based on the quasithermal equilibrium hypothesis. The transient three-dimensional numerical simulations based on the MARS (Multiinterface 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 subcooled bubble behaviors, such as the growth process of the nucleate bubble on the heating surface, the condensation process and the extinction behaviors after departing from the heating surface were investigated, respectively. In this paper, the bubble departing behavior from the heating surface was discussed in detail. The overall numerical results showed in very good agreement with the experimental results.

Ose, Y.; Kunugi, T.

2013-07-01

22

Highly subcooled pool boiling heat transfer at various gravity levels Jungho Kim a,*, John F. Benton b  

E-print Network

Highly subcooled pool boiling heat transfer at various gravity levels Jungho Kim a,*, John F camera was used to provide subcooled pool boiling heat transfer measurements at gravity levels ranging- ronments, respectively. The data indicate that there is little effect of gravity on boiling heat transfer

Kim, Jungho

23

Heater size and heater aspect ratio effects on subcooled pool boiling heat transfer in low-g  

E-print Network

little to no effect on heat transfer during nucleate boiling in earth gravity [6]. Subcooling effectsHeater size and heater aspect ratio effects on subcooled pool boiling heat transfer in low University, New Brunswick, NJ 08901-8520, USA Abstract Pool boiling heat transfer measurements using heaters

Kim, Jungho

24

Uniform temperature, ultrahigh flux heat sinks using curved surface subcooled nucleate boiling  

Microsoft Academic Search

A novel type of heat exchange process is described for use in semiconductor heat sinks. It involves the use of subcooled, nucleate boiling at concave curved surfaces where radial acceleration can be used to develop significant and beneficial buoyancy forces. This system provides a heat transfer surface with a uniform temperature, i.e. the boiling point of the fluid, and requires

Arthur H. Iversen; Stephen Whitaker

1989-01-01

25

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

NASA Astrophysics Data System (ADS)

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.

Ose, Yasuo; Kunugi, Tomoaki

2014-06-01

26

Manual for Subcooled Flow Boiling Code SCB-2  

SciTech Connect

This manual has been written to give the user the basic instructions for using the code. The SCB-2 Code has been written to help engineers in the design of cooling systems required to handle high nonuniform axial heat fluxes. The code provides outputs of the pressure drop, pumping power required and the critical heat flux along with additional details of the flow. This latest version of the code is based on the code SCB-1A. However, significant changes have had to be made to SCB-1A in order to incorporate the logic needed to handle axially nonuniform heat fluxes. These changes generally result in pressure drop predictions for uniform axial heat fluxes which differ by +5% to 10% from of SCB-1A. As a result, it is strongly recommended that code SCB-1A be used for all cases with uniform axial heat flux, since that code has been validated over a specific range of parameters. The SCB-2A code has not been validated since we have found no data for subcooled boiling pressure drops with nonuniform axial heat fluxes. The code starts from the specified inlet flow conditions and integrates down the tube to find the local pressure drop at each point and the local flow conditions. The code uses the local coolant properties at each step. The code also calculates the CHF at each step based on the Gambill correlation to indicate how close to burnout the tube is. Some modifications to this correlation which we have incorporated into the code will be discussed.

Hoffman, M.A.

1990-09-01

27

Bubble behavior in subcooled flow boiling of water at low pressures and low flow rates  

Microsoft Academic Search

This study presents experimental data for subcooled flow boiling of water at pressures from 1.05 to 3 bar, bulk liquid velocities ranging from 0.08 to 0.8 m\\/s, and subcooling from 10 to 30 K. Experiments were carried out on a vertical, annular test section with inner heating surface and upward water flow. High-speed photography at rates of 6000–8000 frames\\/s captured

V Prodanovic; D Fraser; M Salcudean

2002-01-01

28

Numerical Simulation of Subcooled Nucleate Boiling by Coupling Level-Set Method with Moving-Mesh Method  

Microsoft Academic Search

A new numerical procedure coupling the level-set method with the moving-mesh method to simulate subcooled nucleate pool boiling is proposed. Numerical test problems have vali- dated this new method. The simulation of bubble dynamics during nucleate boiling under liquid subcooling shows that this novel adaptive method is more accurate in determining interfacial heat transfer than a computational method based on

Jinfeng Wu; Vijay K. Dhir; Jianliang Qian

2007-01-01

29

Subcooled and saturated water flow boiling pressure drop in small diameter helical coils at low pressure  

SciTech Connect

Experimental pressure drop results on boiling water flow through three helical coils of tube inner diameter of 4.03 mm and 4.98 mm and coil diameter to tube diameter ratio of 26.1, 64.1 and 93.3 are presented. Both subcooled and saturated flow boiling are investigated, covering operating pressures from 120 to 660 kPa, mass fluxes from 290 to 690 kg m{sup -2} s{sup -1} and heat fluxes from 50 to 440 kW m{sup -2}. Existing correlations for subcooled flow pressure drop are found not capable to fit the present subcooled database, while the measurements in saturated flow conditions are successfully reproduced by existing correlations for both straight and coiled pipe two-phase flow. The experimental database is included in tabular form. (author)

Cioncolini, Andrea; Santini, Lorenzo; Ricotti, Marco E. [Department of Nuclear Engineering, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy)

2008-05-15

30

Local flow characteristics of subcooled boiling flow of water in a vertical concentric annulus  

Microsoft Academic Search

The radial profiles of local void fraction and velocities of both phases were measured in subcooled boiling flow of water in a vertical concentric annulus with a heated inner tube. A two-conductivity probe technique was used for the measurements of local void fraction and vapor velocity and a Pitot tube method was applied to measure the local liquid velocity. Measurements

T. H. Lee; G. C. Park; D. J. Lee

2002-01-01

31

Microscale heat transfer measurements during pool boiling of FC-72: effect of subcooling  

E-print Network

reserved. doi:10.1016/j.ijheatmasstransfer.2004.02.008 International Journal of Heat and Mass Transfer 47Microscale heat transfer measurements during pool boiling of FC-72: effect of subcooling Fatih in revised form 6 February 2004 Available online 19 March 2004 Abstract Heat transfer under nucleating

Kim, Jungho

32

Pool boiling heat transfer on small heaters: effect of gravity and subcooling  

E-print Network

in International Journal of Heat and Mass Transfer 45 (2002) 3919­3932 www hydrody- namics, heat transfer, mass transfer, and interfacial phenomena are tightly interwovenPool boiling heat transfer on small heaters: effect of gravity and subcooling Jungho Kim a,*, John

Kim, Jungho

33

Predictions of void fraction in convective subcooled boiling channels using a one-dimensional two-fluid model  

SciTech Connect

Subcooled nucleate boiling under forced convective conditions is of considerable interest for many disciplines, such as nuclear reactor technology and other energy conversion systems, due to its high heat transfer capability. For such applications, the liquid entering the heating channel is usually in a subcooled state and nucleate boiling is initiated at some distance from the entrance. Further downstream from the boiling incipient point, the bubbles may depart from the heating wall. The point of first bubble departure is called the net vapor generation (NVG) point, because after this point, significant void is present in the subcooled liquid and the void fraction rises very rapidly even though the bulk liquid may still be in a highly subcooled state. The presence of vapor bubbles, which are at a temperature near the saturation temperature, in a subcooled liquid shows the existence of thermal nonequilibrium, which complicates the analysis of this boiling regime. 13 refs., 4 figs.

Hu, Lin-Wen; Pan, Chin [National Tsing Hua Univ., Hsinchu (Taiwan, Province of China)

1995-08-01

34

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

SciTech Connect

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.

Dr. Ronald D. Boyd

2000-07-01

35

Steady-state subcooled nucleate boiling on a downward facing hemispherical surface  

SciTech Connect

Steady-state nucleate boiling heat transfer experiments in saturated and subcooled water were conducted. The heating surface was a 0.305 m hemispherical aluminum vessel heated from the inside with water boiling on the outside. It was found that subcooling had very little effect on the nucleate boiling curve in the high heat flux regime where latent heat transport dominated. On the other hand, a relatively large effect of subcooling was observed in the low heat flux regime where sensible heat transport was important. Photographic records of the boiling phenomenon and the bubble dynamics indicated that in the high heat flux regime, boiling in the bottom center region of the vessel was cyclic in nature with a liquid heating phase, a bubble nucleation and growth phase, a bubble coalescence phase, and a large vapor mass ejection phase. At the same heat flux level, the size of the vapor masses was found to decrease from the bottom center toward the upper edge of the vessel, which was consistent with the observed increase in the critical heat flux in the flow direction along the curved heating surface.

Haddad, K.H.; Cheung, F.B. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering

1996-12-31

36

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

SciTech Connect

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)

Wen Wu; Peipei Chen; Jones, Barclay G.; Newell, Ty A. [University of Illinois at Urbana-Champaign, Urbana, IL, 61801 (United States)

2006-07-01

37

Subcooled pool boiling heat transfer in fractal nanofluids: A novel analytical model  

NASA Astrophysics Data System (ADS)

A novel analytical model to determine the heat flux of subcooled pool boiling in fractal nanofluids is developed. The model considers the fractal character of nanofluids in terms of the fractal dimension of nanoparticles and the fractal dimension of active cavities on the heated surfaces; it also takes into account the effect of the Brownian motion of nanoparticles, which has no empirical constant but has parameters with physical meanings. The proposed model is expressed as a function of the subcooling of fluids and the wall superheat. The fractal analytical model is verified by a reasonable agreement with the experimental data and the results obtained from existing models.

Xiao, Bo-Qi; Yang, Yi; Xu, Xiao-Fu

2014-02-01

38

Experimental investigation of micro-scale temperature transients in sub-cooled flow boiling on a horizontal heater  

E-print Network

Experimental investigation of micro-scale temperature transients in sub-cooled flow boiling: Flow boiling Thin film thermocouple Microfabrication Nanofabrication Fast Fourier transform a b s t r a c t Surface temperature fluctuations that occur locally underneath departing bubbles in pool boiling

Banerjee, Debjyoti

39

A study of the effects of heater size, subcooling, and gravity level on pool boiling heat transfer  

E-print Network

A study of the effects of heater size, subcooling, and gravity level on pool boiling heat transfer Martin Hill, College Park, MD 20742, USA Abstract Pool boiling heat transfer measurements from different. Boiling on three heaters of different size (0.65, 2.62, 7.29 mm2 ) was studied. Control circuitry was used

Kim, Jungho

40

The dynamics of a vapour bubble growth under the boiling of a subcooled liquid in low volumes  

NASA Astrophysics Data System (ADS)

This paper presents an experimental study of the dynamics of a vapour bubble growth under the boiling of a subcooled liquid in low volumes. The influence of the mode parameters (heat flux and subcooling to the saturation temperature) on the geometric characteristics of the vapour bubble (base diameter and height) has been found.

Orlova, Evgenija; Kuznetsova, Geniy; Feoktistovb, Dmitriy

2014-08-01

41

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

SciTech Connect

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.

Chou, X.S.; Sankaran, S.; Witte, L.C. (Univ. of Houston, TX (United States))

1995-02-01

42

Subcooled pool boiling of water on a downward-facing stainless steel disk in a gap  

Microsoft Academic Search

Pool boiling is experimentally studied on a relatively large downward-facing surface with heated stainless steel disk diameters of D=100 and 300mm in confined space at atmospheric pressure using water as the working fluid. The bulk working fluid is subcooled. The gap size s can be adjusted to 10, 15 and 20mm for D=100mm and 0.9–77mm for D=300mm. We found that

G. H. Su; Y. W. Wu; K. Sugiyama

2008-01-01

43

Assessment of Effect of Bubble Departure Frequency in Forced Convection Subcooled Boiling  

Microsoft Academic Search

Bubble departure frequency is one of the important parameters for the prediction of subcooled flow boiling. This present work aims at an assessment of bubble departure frequency by investigating the physical mechanisms of three- dimensional two-fluid model coupled with the population balance equation. The CFX MUltiple-SIze-Group (MUSIG) model is used to predict bubbly flows with the presence of heat and

R. Situ; G. H. Yeoh; T. Hibiki

44

The effect of the radiative heat transfer on subcooled film boiling  

NASA Astrophysics Data System (ADS)

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.

Nilsuwankosit, Sunchai

45

Study of the initiation of subcooled boiling during power transients  

Microsoft Academic Search

An experimental investigation of boiling initiation during power transients has been conducted for horizontal-cylinder heating elements in degassed distilled water. Platinum elements, 0.127 and 0.250 mm in diameter, were internally heated electrically at a controlled superficial heat flux (power applied divided by surface area) increasing linearly with time at rates of 0.035 and 0.35 MW\\/m²s and corresponding test durations of

VanVleet

1985-01-01

46

An experimental investigation of critical heat flux performance of hypervapotron in subcooled boiling  

NASA Astrophysics Data System (ADS)

The successful use of subcooled flow boiling for high heat flux components requires that the critical heat flux (CHF), i.e., a fast reduction in the boiling heat transfer, must be avoided. Among the many techniques available to enhance CHF, particular attention has been focused on the hypervapotron concept. In this study, the CHF characteristics of the hypervapotron were experimentally investigated using a simulant fluid, R134a, which has been found to be an effective modeling fluid to simulate CHF in water-cooled environments. An experimental and modeling study of the subcooled boiling heat transfer on plain surface and hypervapotron has been conduced. A test facility was designed and constructed to perform required boiling heat transfer experiments. A high speed visualization system was utilized to give details of bubble formation and departure and of nucleation site density. Surface measurements of various specimens were performed to investigate the relationship between nucleation sites and surface microstructure. Full characterization of the hypervapotron effect as a function of fluid thermal hydraulic conditions was accomplished. A non-dimensional CHF correlation for smooth rectangular channels and the hypervapotron channel was developed and compared with experimental data in this work. In addition, a hot-spot model was developed to give predictions of critical heat flux on both plain and hypervapotron surfaces. It was developed on observations of bubble formation, departure and coalescence, and on the confirmation of nucleation structure on the heating surface. Finally, a numerical code was successfully developed to give CHF predictions for hypervapotron configurations. The simulation indicates that the better performance of CHF in hypervapotron configurations is a result of high conductivity material with augmented heating surfaces in subcooled boiling environment. Different fin dimensions were also tested numerically to compare the experimental results, and suggestions are provided with respect to the combination of performance and economy.

Chen, Peipei

47

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

SciTech Connect

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.

Chou, X.S.; Witte, L.C. (Univ. of Houston, TX (United States))

1995-02-01

48

Stability of vapor film in subcooled film boiling on a horizontal wire  

SciTech Connect

Linear stability analysis of a thin vapor film in subcooled film boiling on a horizontal cylinder was presented. The effects of liquid inertia, vapor viscosity and compressibility, and heat transfer were taken into account. Theoretical predictions of the heat transfer coefficient at the critical vapor film thickness was compared with experimental data at the minimum-heat-flux point that was obtained during the rapid quenching of thin horizontal wires in water and ethanol. At high liquid subcoolings, the measured value was about 63% of the theoretical predictions irrespective of the wire diameter and quenching liquid. This difference was considered to be due to the non-uniformity of vapor film thickness that was neglected in the theoretical analysis.

Takamatsu, Hiroshi; Yamashiro, Hikaru; Honda, Hiroshi [Kyushu Univ., Kasuga, Fukuoka (Japan). Inst. of Advanced Material Study

1996-12-31

49

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

NASA Astrophysics Data System (ADS)

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.

Zou, Ling

50

An experimental study of subcooled flow film boiling across horizontal cylinders  

NASA Astrophysics Data System (ADS)

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.

Warrier, Gopinath Rama

51

Heating surface material’s effect on subcooled flow boiling heat transfer of R134a  

SciTech Connect

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.

Ling Zou; Barclay G. Jones

2012-11-01

52

Ultrahigh critical heat flux (CHF) for subcooled water flow boiling—II: high-CHF database and design equations  

Microsoft Academic Search

A high-CHF (critical heat flux) database for subcooled flow boiling of water in tubes was compiled from the world literature. The bulk of the database is for high mass velocity flow (G ?5000 kg m?2 s?1) in small diameter tubes (D ? 3 mm) . Over half of the 1596 valid data points in the database had CHF values in

David D. Hall; Issam Mudawar

1999-01-01

53

A computer code for calculating subcooled boiling pressure drop in forced convective tube flows  

SciTech Connect

A calculation procedure, embodied in a computer code, was developed to calculate the convective subcooled boiling (SCB) pressure drop of water flowing in small diameter vertical or horizontal tubes under the condition of high heat fluxes. The present investigation is an extension of previous work performed by C.T. Kline in 1985. The computer code, presented then and now, numerically integrates the single-phase and separated-flow-model pressure drop equations from the inlet to the outlet of a heated tube. Efforts in this study were concentrated on identifying weaknesses in Kline's best code version and investigating his recommendations for future work. The calculation procedures for each flow regime in the tube were modified to give better overall results. New work focused primarily on the partially-developed boiling (PDB) and fully-developed boiling (FDB) regimes. The pressure drop predictions from each code version were compared to the experimental pressure drop results from the experimental investigations of Dormer/Bergles, Owens/Schrock, and Reynolds. 33 refs., 55 figs., 2 tabs.

Wong, Christopher F.

1988-12-01

54

Statistical modeling support for calibration of a multiphysics model of subcooled boiling flows  

SciTech Connect

Nuclear reactor system analyses rely on multiple complex models which describe the physics of reactor neutronics, thermal hydraulics, structural mechanics, coolant physico-chemistry, etc. Such coupled multiphysics models require extensive calibration and validation before they can be used in practical system safety study and/or design/technology optimization. This paper presents an application of statistical modeling and Bayesian inference in calibrating an example multiphysics model of subcooled boiling flows which is widely used in reactor thermal hydraulic analysis. The presence of complex coupling of physics in such a model together with the large number of model inputs, parameters and multidimensional outputs poses significant challenge to the model calibration method. However, the method proposed in this work is shown to be able to overcome these difficulties while allowing data (observation) uncertainty and model inadequacy to be taken into consideration. (authors)

Bui, A. V.; Dinh, N. T.; Nourgaliev, R. R. [Idaho National Laboratory, MS-3870, PO Box 1625, Idaho Falls, ID, 83415 (United States); Williams, B. J. [Los Alamos National Laboratory, MS-F600, PO Box 1663, Los Alamos, NM, 87545 (United States)

2013-07-01

55

Experimental measurements and CFD simulation of convective boiling during subcooled developing flow of R-11 within vertical annulus  

NASA Astrophysics Data System (ADS)

In this paper a convective flow boiling of refrigerant R-11 in a vertical annular channel has been investigated. Measurements were performed under various conditions of mass flux, heat flux, and inlet subcooling, which enabled to study the influence of different boundary conditions on the development of local flow parameters. Also, some measurements have been compared to the predictions by the three-dimensional two-fluid model of subcooled boiling flow carried out with the computer code ANSYS-CFX-13. Simulation results successfully predict the main experimental tendencies associated with the heat flux and Reynolds number variation. A sensitivity analysis of several modelling parameters on the radial distribution of flow quantities has highlighted the importance of correct description of the boiling boundary layer. In general a good quantitative and qualitative agreement with experimental data was obtained.

Bouaichaoui, Y.; Kibboua, R.; Matkovi?, M.

2014-10-01

56

Enhancement of critical heat flux in subcooled flow boiling of water by use of a volatile additive  

SciTech Connect

The present investigation considers the effect of a 1-pentanol additive in water on the critical heat flux (CHF) and pressure drop in forced subcooled boiling. A small quantity of 1-pentanol was added to distilled water with the objective of getting an approximate 2% by weight mixture, which had been found to give superior performance in previous studies of pool and flow boiling. Experiments were performed using stainless steel tubes with internal diameters of 4.4 and 6.1 mm. Tests were conducted with mass fluxes of 4,400 kg/m{sup 2}s, exit pressures of 9 bar, length-to-diameter ratios of 25, and exit subcoolings from 65 to 90 C. Test sections were heated directly by DC power, and critical heat flux data were inferred from test-section burnout. The alcohol concentration was periodically checked by draining off a sample and performing a Proton Nuclear Magnetic Resonance scan on the mixture. At high subcoolings, the mixture exhibited an increase in the critical heat flux over that of pure water. However at low subcoolings there is a decrease in the critical heat flux. The increases in critical heat flux noted with the 1-pentanol mixture in this experiment were not as large as would be expected from saturated pool boiling results published by Van Stralen (1959). Pressure drop data for both the mixture and the pure water also were recorded. The 1-pentanol mixture, in general, exhibited larger pressure drops for the same conditions. Subcooled flow boiling has a wide array of commercial cooling applications, including blades in gas turbines, high power laser optics, plasma-facing components in fusion reactors, supercomputers, etc.

Pabisz, R.A. Jr.; Bergles, A.E. [Rensselaer Polytechnic Inst., Troy, NY (United States). Heat Transfer Lab.

1996-12-31

57

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

SciTech Connect

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)

Hayato Kubota; Tatsuhiro Ishida; Tomio Okawa; Isao Kataoka [Osaka University, 1-1, Yamadaoka, Suita-shi, Osaka (Japan); Michitsugu Mori [Tokyo Electric Power Company (Japan)

2006-07-01

58

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

SciTech Connect

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)

Hwang, J. S.; Park, I. U.; Park, M. Y.; Park, G. C. [Dept. of Energy Systems Engineering, Seoul National Univ., 599 Gwanak-Ro, Gwanak-Gu, Seoul, 151-744 (Korea, Republic of)

2012-07-01

59

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

SciTech Connect

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)

Wu, Wen; Chen, Peipei; Jones, Barclay G. [Department of Nuclear, Plasma, and Radiological Engineering, University of Illinois at Urbana-Champaign Urbana, IL 61801 (United States); Newell, Ty A. [Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign Urbana, IL 61801 (United States)

2006-07-01

60

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

SciTech Connect

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)

Heo, S.; Koshizuka, S.; Oka, Y. [Nuclear Engineering Research Laboratory, The University of Tokyo, 2-22 Shirane, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1188 (Japan)

2002-07-01

61

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

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.

Barclay Jones

2005-06-27

62

Chemical evolution and mineral deposition in boiling hydrothermal systems  

Microsoft Academic Search

A thermodynamic model of boiling hydrothermal solutions is developed and applied over a wide range of physical and chemical conditions. Vaporization of only a few percent of a solution can decrease the proton concentration by several orders of magnitude when the COâ\\/H..mu.. and COâ\\/..sigma..SOâ concentration ratios are initially high. The relationship between the proton, COâ, and ..sigma..SOâ concentrations prior to

S. E. Drummond; H. Ohmoto

1985-01-01

63

Development of a flow boiling map for subcooled and saturated flow boiling of different fluids inside circular tubes  

Microsoft Academic Search

The thermal behavior of a flow boiling system is represented by a flow boiling map to illustrate visually the relationships among various system parameter. An earlier flow boiling map by Collier (1981) does not include the effect of mass flux and is specific to water at low pressures. For other fluids, significant departures from the parametric trends displayed in Collier's

S. G. Kandlikar

1991-01-01

64

Effects of dissolved air on subcooled and saturated flow boiling of water in a small diameter tube at low pressure  

SciTech Connect

Experimental results on flow boiling of air saturated water flowing through a tube of inner diameter d{sub i} = 4.03 mm are presented. Both subcooled and saturated flow boiling are investigated, covering pressures from 177 to 519 kPa, mass fluxes from 478 to 839 kg m{sup -2} s{sup -1} and heat fluxes from 210 to 736 kW m{sup -2}. By comparing the measured results with existing prediction methods derived for degassed liquids the study concludes that the presence of dissolved air in the testing fluid can be regarded as a second order effect, and no special attention to dissolved air appears required. (author)

Cioncolini, Andrea; Santini, Lorenzo; Ricotti, Marco E. [Department of Nuclear Engineering, Politecnico di Milano, via Ponzio 34/3, 20133 Milano (Italy)

2007-10-15

65

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

SciTech Connect

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.

Anh Bui; Nam Dinh; Brian Williams

2013-09-01

66

On the Influence of Heating Surface Structure on Bubble Detachment in Sub-Cooled Nucleate Boiling Flows  

SciTech Connect

This research examines the influence of heating surface structure on bubble detachment, which includes bubble departure and bubble lift-off, under sub-cooled nucleate boiling condition, in order to obtain better understanding to the bubble dynamics on horizontal flat heat exchangers. 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. Experiments were run with varying experimental parameters e.g. pressure, inlet sub-cooled level, and flow rate, etc. High speed digital images at frame rates up to 4000 frames/s were obtained, showing characteristics of bubble movement. Bubble radius and center coordinates were calculated via Canny's algorithm for edge detection and Fitzgibbon's algorithm for ellipse fitting. Results were compared against the model proposed by Klausner et al. for prediction of bubble detachment sizes. Good overall agreement was shown, with several minor modifications and suggestions made to the assumptions of the model. (authors)

Wen Wu; Peipei Chen; Jones, Barclay G.; Newell, Ty A. [University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States)

2006-07-01

67

Alumina Nanoparticle Pre-coated Tubing Ehancing Subcooled Flow Boiling Cricital Heat Flux  

E-print Network

Nanofluids are engineered colloidal dispersions of nano-sized particle in common base fluids. Previous pool boiling studies have shown that nanofluids can improve critical heat flux (CHF) up to 200% for pool boiling and ...

Truong, Bao H.

68

Bubble sweeping and jet flows during nucleate boiling of subcooled liquids  

Microsoft Academic Search

An experimental investigation was conducted to investigate nucleate boiling on a very fine heating wire. By using zoom routine and CCD camera system, the dynamical process of nucleate boiling was visually observed. Sweeping bubbles and several modes of jet flows were described and discussed. For some cases, big bubbles, small bubbles, sweeping bubbles and jet flows coexisted in boiling system,

H. Wang; X. F. Peng; B. X. Wang; D. J. Lee

2003-01-01

69

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

70

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

SciTech Connect

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)

In Cheol Bang; Soon Heung Chang [Korea Advanced Institute of Science and Technology, 373-1, Guseung-dong, Yuseong-ku, Daejeon, 305-701 (Korea, Republic of); Won-Pil Baek [Korea Atomic Energy Research Institute, 150, Dukjin-Dong, Yusong-Gu, Taejon 305-353 (Korea, Republic of)

2002-07-01

71

A study of system-induced instabilities in forced-convection flows with subcooled boiling  

E-print Network

A combined analytical and experimental program was carried out to investigate the problem of hydrodynamic stability of forcedconvection flows with boiling. The study was restricted to the flow of water in small channels ...

Maulbetsch, John S.

1965-01-01

72

Bubble behavior in subcooled flow boiling on surfaces of variable wettability  

E-print Network

Flow boiling is important in energy conversion and thermal management due to its potential for very high heat fluxes. By improving understanding of the conditions leading to bubble departure, surfaces can be designed that ...

Tow, Emily W

2012-01-01

73

Simulation of subcooled boiling at low pressure conditions with RELAP5-3D computer program  

E-print Network

or no effect on the surface temperature. Jens and Lottes (1951) obtained a relationship between AT?r and P for water, which was further modified by Thorn et al. (1965). The correlation is given by: P AT~r =22. 65$"e " ATs~r is in C tl is in MW/m2 and P... ') Unal specified the range for which this correlation fits the experimental data: Pressure: 0. 1-17. 7 Mpa, heat flux: 0. 47-10. 64 MW/m, bulk liquid velocity: 0. 08-9. 15 m/s, subcooling: 3-86 K maximum bubble diameter: 0. 08-1. 24 mm and maximum...

Reza, S.M. Mohsin

2012-06-07

74

Effect of pressure, subcooling, and dissolved gas on pool boiling heat transfer from microporous, square pin-finned surfaces in FC72  

Microsoft Academic Search

The present research is an experimental study of the effects of pressure, subcooling, and non-condensable gas (air) on the pool nucleate boiling heat transfer performance of microporous enhanced finned surfaces. The test surfaces, solid copper blocks with 1-cm2 bases and 5×5 square pin-fin arrays of 2, 4 and 8 mm fin lengths, were immersed in FC-72. The test conditions included

K. N Rainey; S. M You; S Lee

2003-01-01

75

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

SciTech Connect

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.

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

1995-12-31

76

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

NASA Technical Reports Server (NTRS)

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.

Kim, Jungho; Benton, John; Kucner, Robert

2000-01-01

77

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)

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.

Bloch, Gregor; Kuczaty, Julian; Sattelmayer, Thomas

2014-02-01

78

Non-linear dynamical analyses of transient surface temperature fluctuations during subcooled pool boiling on a horizontal disk  

E-print Network

-nearest neighbors, recurrence plots and space�time separation plots are obtained using the TISEAN package.7 in film boiling. False-nearest neighbor estimates and recurrence plots show that nucleate boiling may

Banerjee, Debjyoti

79

Subcooled flow boiling heat transfer and critical heat flux in water-based nanofluids at low pressure  

E-print Network

A nanofluid is a colloidal suspension of nano-scale particles in water, or other base fluids. Previous pool boiling studies have shown that nanofluids can improve the critical heat flux (CHF) by as much as 200%. In this ...

Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology

2009-01-01

80

A New Facility for Measurements of Three-Dimensional, Local Subcooled Flow Boiling Heat Flux and Related Critical Heat Flux for PFCs  

SciTech Connect

In the development of plasma-facing components for fusion reactors and high-heat-flux heat sinks (or components) for electronic applications, the components are usually subjected to a peripherally nonuniform heat flux. Even if the applied heat flux is uniform in the axial direction (which is unlikely), both intuition and recent investigations have clearly shown that both the local heat flux and the eventual critical heat flux (CHF) in this three-dimensional (3-D) case will differ significantly from similar quantities found in the voluminous body of data for uniformly heated flow channels. Although this latter case has been used in the past as an estimate for the former case, more study has become necessary to examine the 3-D temperature and heat flux distributions and related CHF. Work thus far has shown that the nonuniform peripheral heat flux condition enhances CHF in some cases.To avoid the excess costs associated with using electron or ion beams to produce the nonuniform heat flux, a new facility was developed that will allow 3-D conjugate heat transfer measurements and two-dimensional, local subcooled flow boiling heat flux and related CHF measurements.The configurations under study for this work consist of (a) a nonuniformly heated cylinder-like test section with a circular coolant channel bored through the center and (b) a monoblock that is a square cross-section parallelepiped with a circular drilled flow channel along the channel centerline. The theoretical or ideal cylinder-like test section would be a circular cylinder with half (-90 to 90 deg) of its outside boundary subjected to a uniform heat flux and the remaining half insulated. For the monoblock, a uniform heat flux is applied to one of the outside surfaces, and the remaining surfaces are insulated. The outside diameter of the cylinder-like test section is 30.0 mm, and its length is 200.0 mm. The monoblock square is 30.0 mm long. The inside diameter of the flow channel for both types of test sections is 10.0 mm. Water is the coolant. The inlet water temperature can be set at any level in the range from 26.0 to 130.0 deg. C, and the exit pressure can be set at any level in the range from 0.4 to 4.0 MPa. Thermocouples were placed at 48 locations inside the solid cylinder-like or monoblock test section to obtain 3-D wall temperature variations and related local heat flux. Finally, the mass velocity can be set at any level in the range from 0.4 to 10.0 Mg/m{sup 2}.s for the 10.0-mm-diam channel.

Boyd, Ronald D. Sr.; Cofie, Penrose; Li Qingyuan; Ekhlassi, Ali A

2002-01-15

81

CONVECTIVE HEAT TRANSFER OF BINARY MIXTURES UNDER FLOW BOILING CONDITIONS  

E-print Network

CONVECTIVE HEAT TRANSFER OF BINARY MIXTURES UNDER FLOW BOILING CONDITIONS E. V. McAssey Jr results are presented for the heat transfer coefficient under flow boiling conditions for water-phase non-boiling region through the fully developed subcooled flow boiling region to saturated boiling

Kandlikar, Satish

82

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

Microsoft Academic Search

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 (â¼ 60 m in diameter). Compositions range from a 300C, gas-enriched (285 mmol\\/kg COâ), low-chlorinity (â¼ 33% of seawater) fluid to a 328C, relatively gas-depleted (50 mmol\\/kg COâ), high-chlorinity (â¼ 116% of seawater) fluid. The

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

1990-01-01

83

CFD simulation of refrigerant boiling in vertical annulus  

Microsoft Academic Search

In this paper a forced convective boiling of Refrigerant R-113 in a vertical annular channel has been simulated by the CFX-5 code. The employed subcooled boiling model uses a special treatment of the wall boiling boundary, which assures the grid invariant solution. The simulation results have been validated against the published experimental data (1). In general a good agreement with

Eckhard Krepper

84

CFD SIMULATION OF FORCED CONVECTIVE BOILING IN HEATED CHANNELS  

Microsoft Academic Search

In this paper a forced convective boiling of Refrigerant R-113 in a vertical annular channel has been simulated by a custom version of the CFX-5 code. The employed subcooled boiling model uses a special treatment of the wall boiling boundary, which assures the grid invariant solution. The simulation results have been validated against the published experimental data (1). In general

Eckhard Krepper

85

Control Dewar Subcooler Heat Exchanger Calculations  

Microsoft Academic Search

The calculations done to size the control dewar subcooler were done to obtain a sufficient subcooler size based on some conservative assumptions. The final subcooler design proposed in the design report will work even better because (1) It has more tubing length, and (2) will have already subcooled liquid at the inlet due to the transfer line design. The subcooler

R. Rucinski

1993-01-01

86

Subcooling for Long Duration In-Space Cryogenic Propellant Storage  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

87

Condensation on a noncollapsing vapor bubble in a subcooled liquid  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

88

Condensation on a noncollapsing vapor bubble in a subcooled liquid  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

89

A model for correlating flow boiling heat transfer in augmented tubes and compact evaporators  

Microsoft Academic Search

The additive model for the convective and nucleate boiling components originally suggested by Bergles and Rohsenow (1964) for subcooled and low-quality regions was employed in the Kandlikar correlation (1990a) for flow boiling in smooth tubes. It is now extended to augmented tubes and compact evaporators. Two separate factors are introduced in the convective boiling and the nucleate boiling terms to

S. G. Kandlikar

1991-01-01

90

High flux film and transition boiling  

SciTech Connect

An investigation was conducted on the potential for altering the boiling curve through effects of high velocity and high subcooling. Experiments using water and Freon-113 flowing over cylindrical electrical heaters in crossflow were made to see how velocity and subcooling affect the boiling curve, especially the film and transition boiling regions. We sought subcooling levels down to near the freezing points of these two liquids to prove the concept that the critical heat flux and the minimum heat flux could be brought together, thereby averting the transition region altogether. Another emphasis was to gain insight into how the various boiling regions could be represented mathematically on various parts of heating surface. Motivation for the research grew out of a realization that the effects of very high subcooling and velocity might be to avert the transition boiling altogether so that the unstable part of the boiling curve would not limit the application of high flux devices to temperatures less than the burnout temperatures. Summaries of results from the study are described. It shows that the potential for averting, the transition region is good, and points the way to further research that is needed to demonstrate the potential.

Witte, L.C.

1993-02-01

91

Microjet array single-phase and flow boiling heat transfer with R134a Eric A. Browne a  

E-print Network

Microjet array single-phase and flow boiling heat transfer with R134a Eric A. Browne a , Gregory J boiling a b s t r a c t An experimental study of single-phase and flow boiling heat transfer:6 6 Nud 6 128. Boiling experiments were conducted with liquid subcoolings of 10, 20, and 30 °C at jet

Peles, Yoav

92

156 IEEE TRANSACTIONS ON COMPONENTS AND PACKAGING TECHNOLOGIES, VOL. 32, NO. 1, MARCH 2009 Pool Boiling Experiments on  

E-print Network

Boiling Experiments on a Nano-Structured Surface Hee Seok Ahn, Vijaykumar Sathyamurthi, and Debjyoti Banerjee Abstract--The effect of nano-structured surfaces on pool boiling was investigated. Saturated and subcooled pool boiling experi- ments were performed on a horizontal heater surface coated with vertically

Banerjee, Debjyoti

93

Pool boiling studies on nanotextured surfaces under highly subcooled conditions  

E-print Network

......................................................... 1 1.2 Carbon Nanotubes............................................................... 3 1.3 Nanofluids........................................................................... 4 1.4 Motivation for Study.... There is still disagreement with regard to the nature of variation of thermal conductivity of CNT with temperature in available literature [21-24]. 1.3 Nanofluids Whilst CNT have garnered a lot of attention in the past decade, nanofluids are beginning...

Sathyamurthi, Vijaykumar

2009-05-15

94

Fluid inclusion evidence for boiling at approx. 370/sup 0/C in the stockwork of the Lasail ophiolitic hydrothermal massive sulfide deposit, Oman  

SciTech Connect

Four samples of stockwork material from DDHnumber9 through the Lasail ophiolitic massive sulfide deposit in Oman were found to contain satisfactory densities of primary fluid inclusion. Primary fluid inclusions in the latter three samples show evidence typical of boiling: (i) variable phase rations, and (ii) inclusions which homogenize into the liquid or vapor phases over the same temperature interval (360/sup 0/C-400/sup 0/C). The pooled data show two salinity populations: one with a modal composition near that of seawater, (3.5 wt.%TDS), and the other characterized by the bulk of the data concentrated between 4.9 and 6.4 equiv. wt.% NaCl (x 1.4-1.8 seawater) with values as high as 8.6 (x 2.5 seawater). The latter high salinities are interpreted to have been produced by the boiling process. For boiling conditions, fluid inclusion homogenization temperatures = trapping temperatures, with some perturbations. Hence, the mode (372/sup 0/C) and range (360/sup 0/C-400/sup 0/C) of the homogenization temperatures for the high salinity population are estimates of the fluid temperatures during ore deposition. The values are at the upper end of the measured range for black smokers. The pressure given by these boiling temperatures is approx. 230 bars, giving an estimate for original seawater depth of approx. 2-2 1/2 km; figures typical of active spreading ridges. The sample from immediately below massive ore (OM2064) shows a lower hom. T range of 330/sup 0/C-350/sup 0/C, no high salinity population, and no evidence for boiling. These observations are interpreted to reflect high level mixing with cold seawater immediately below the original sea floor.

Spooner, E.T.C.; Bray, C.J.

1985-01-01

95

Enhancement of natural convection and pool boiling heat transfer via ultrasonic vibration  

E-print Network

on the heat transfer regime and the amount of dissolved gas. In the natural convection and subcooled boiling streaming are major factors enhancing heat transfer rate. The highest enhancement ratio is obtained] and Bonekamp and Bier [6] studied the influence of ultrasound on nucleate boiling heat transfer, to find

Kim, Ho-Young

96

Forced convection heat transfer of subcooled liquid hydrogen in horizontal tubes  

NASA Astrophysics Data System (ADS)

Forced flow heat transfers of liquid hydrogen through horizontally-mounted tubes with the diameter of 3.0 mm and 6.0 mm were measured at the pressure of 0.7 MPa for various inlet temperatures and flow velocities. The measured non-boiling heat transfer coefficients agree with those by the Dittus-Boelter correlation. The heat fluxes at the onset of nucleate boiling and the departure from nucleate boiling (DNB) heat fluxes, where the heat transfer continuously changes to film boiling regime, are higher for higher flow velocity, larger subcooling and larger tube diameter. The DNB heat fluxes for the horizontally-mounted tube are slightly lower than those for the vertically-mounted tube, although the effect of the tube attitude direction disappears for a small tube diameter. The measured DNB heat fluxes agree with the correlation for vertically-mounted tubes.

Tatsumoto, Hideki; Shirai, Yasuyuki; Shiotsu, Masahiro; Hata, Koichi; Naruo, Yoshihiro; Kobayashi, Hiroyuki; Inatani, Yoshifumi; Kinoshita, K.

2012-06-01

97

Calculation of pH and mineral equilibria in hydrothermal waters with application to geothermometry and studies of boiling and dilution  

NASA Astrophysics Data System (ADS)

Using chemical analyses and 25° pH measurements of quenched high-temperature waters, we calculate in situ pH and distribution of aqueous species at high temperature. This is accomplished by solving simultaneous mass action equations for complexes and redox equilibria and mass balance equations, on all components, including a H + equation with as many as 60 terms (depending on water composition). This calculation provides accurate values for the activities of aqueous ions in a given water at high temperature, which are used to calculate an ion activity product ( Q) for each of more than 100 minerals. The value of log( Q/ K) for each mineral, where K is the equilibrium constant, provides a measure of proximity of the aqueous solution to equilibrium with the mineral. By plotting log Q/ Kvs. T for natural waters, it is possible to determine: a) whether the water was in equilibrium with a host rock mineral assemblage, b) probable minerals in the equilibrium assemblage and c) the temperature of equilibrium. In cases where the fluid departs from equilibrium with a host rock assemblage, it is possible to determine whether this may result from boiling or dilution, and an estimate of amount of lost gas or diluting water can be determined. The calculation is illustrated by application to geothermal waters from Iceland, Broadlands, and Sulphur Bank, hot spring waters from Jemez, Yellowstone and Blackfoot Reservoir (Idaho) and fluid inclusions from the Sunnyside Mine, Colorado. It is shown that most geothermal waters approach equilibrium with a subsurface mineral assemblage at a temperature close to measured temperatures and that some hot springs also approach equilibrium with the host rock at temperatures above outlet temperatures but commonly below the Na-K-Ca temperatures. The log Q/ K plots show that some discrepancies between Na-K-Ca temperatures on spring waters and actual temperatures result from a failure of alkali feldspars to equilibrate with the fluid and with each other. Calculations on Sulphur Bank fluids show that boiling probably caused cinnabar precipitation near 150°C and that the boiled fluids equilibrated with secondary minerals near 150° even though temperatures up to 185° have been measured at depth. For the fluid inclusions, the measured bubble temperatures are close to those calculated for equilibration of the fluid with the observed sulfide mineral assemblage. New estimates of stability constants for aluminum hydroxide complexes are included at the end of the paper.

Reed, Mark; Spycher, Nicolas

1984-07-01

98

Simulation of Boiling Flow Experiments close to CHF with the NEPTUNE-CFD code  

Microsoft Academic Search

A three-dimensional two-fluid code NEPTUNE_CFD has been validated against the ASU (Arizona State University) (1) and DEBORA (2, 3) boiling flow experiments. Nucleate boiling processes in the subcooled flow boiling regime have been studied on ASU experiments. Within this scope a new wall function is implemented in the NEPTUNE_CFD V1.0.6 code to improve the prediction of flow parameters in the

Katarina Mramor

99

Pool boiling  

SciTech Connect

Heat transfer between a wall and a stagnant boiling liquid is reviewed in this paper. The effect of different parameters on the boiling curve is pointed out on the basis of experimental data from the literature. Augmentation of heat transfer by enhanced surfaces is described briefly. The available correlations for prediction of heat transfer coefficients are given for the entire boiling curve, i.e., nucleate, transitional, and film boiling, and critical points. These correlations are useful for the design and operation of various heat-exchange systems.

Lallemand, M. [Lab. d`Energetique et d`Automatique, Villeurbanne (France). Centre de Thermique

1993-10-01

100

Bizarre Boiling  

NSDL National Science Digital Library

This NASA website has QuickTime videos that compare boiling water on Earth and in space. A photo shows the bubble that forms in space once some of the water is boiled. Text provides background information and explains how the experiments were performed.

2007-07-01

101

High flux film and transition boiling. Final report, April 1988--January 1993  

SciTech Connect

An investigation was conducted on the potential for altering the boiling curve through effects of high velocity and high subcooling. Experiments using water and Freon-113 flowing over cylindrical electrical heaters in crossflow were made to see how velocity and subcooling affect the boiling curve, especially the film and transition boiling regions. We sought subcooling levels down to near the freezing points of these two liquids to prove the concept that the critical heat flux and the minimum heat flux could be brought together, thereby averting the transition region altogether. Another emphasis was to gain insight into how the various boiling regions could be represented mathematically on various parts of heating surface. Motivation for the research grew out of a realization that the effects of very high subcooling and velocity might be to avert the transition boiling altogether so that the unstable part of the boiling curve would not limit the application of high flux devices to temperatures less than the burnout temperatures. Summaries of results from the study are described. It shows that the potential for averting, the transition region is good, and points the way to further research that is needed to demonstrate the potential.

Witte, L.C.

1993-02-01

102

NATURAL CONVECTION OF SUBCOOLED LIQUID NITROGEN IN A VERTICAL CAVITY  

E-print Network

NATURAL CONVECTION OF SUBCOOLED LIQUID NITROGEN IN A VERTICAL CAVITY Yeon SukChoi \\ Steven W. Van to measure the natural convection of subcooled liquid nitrogen between two vertical plates has been performed power transformer cooled by natural convection of subcooled liquid nitrogen. A liquid nitrogen bath

Chang, Ho-Myung

103

Hydrothermal Biogeochemistry  

NASA Astrophysics Data System (ADS)

Life in hot spring ecosystems is confronted with diverse challenges, and the responses to those challenges have dynamic biogeochemical consequences over narrow spatial and temporal scales. Within meters along hot spring outflow channels at Yellowstone, temperatures drop from boiling, and the near-boiling conditions of hot chemolithotrophic communities, to those that permit photosynthesis and on down to conditions where nematodes and insects graze on the edges of photosynthetic mats. Many major and trace element concentrations change only mildly in the water that flows through the entire ecosystem, while concentrations of other dissolved constituents (oxygen, sulfide, ammonia, total organic carbon) increase or decrease dramatically. Concentrations of metals and micronutrients range from toxic to inadequate for enzyme synthesis depending on the choice of hot spring. Precipitation of minerals may provide continuous growth of microbial niches, while dissolution and turbulent flow sweeps them away. Consequently, microbial communities change at the meter scale, and even more abruptly at the photosynthetic fringe. Isotopic compositions of carbon and nitrogen in microbial biomass reflect dramatic and continuous changes in metabolic strategies throughout the system. Chemical energy sources that support chemolithotrophic communities can persist at abundant or useless levels, or change dramatically owing to microbial activity. The rate of temporal change depends on the selection of hot spring systems for study. Some have changed little since our studies began in 1999. Others have shifted by two or more units in pH over several years, with corresponding changes in other chemical constituents. Some go through daily or seasonal desiccation cycles, and still others exhibit pulses of changing temperature (up to 40°C) within minutes. Taken together, hydrothermal ecosystems provide highly manageable opportunities for testing how biogeochemical processes respond to the scale of temporal, spatial, and compositional changes.

Shock, E.; Havig, J.; Windman, T.; Meyer-Dombard, D.; Michaud, A.; Hartnett, H.

2006-12-01

104

Boiling incipience in a reboiler tube  

SciTech Connect

This heating surface and liquid temperature distributions were experimentally obtained to identify the boiling incipience conditions in a single vertical tube thermosiphon reboiler with water, acetone, ethanol, and ethylene glycol as test liquids. The test section was an electrically heated stainless steel tube of 25.56-mm i.d. and 1900 mm long. The uniform heat flux values were used in the range of 3800--40 000 W/m{sup 2}, while inlet liquid subcooling were varied from 0.2 to 45.5{degrees} C. The liquid submergence was maintained around 100, 75, 50 and 30%. All the data were generated at 1-atm pressure. The maximum superheats attained around boiling incipience were taken from the wall temperature distributions and correlated with heat flux and physical properties of liquids using the expression of Yin and Abdelmessih. The heated sections required for onset of fully developed boiling with net vapor generation were determined assuming a thermal equilibrium model. In this paper a dimensionless correlation relating these values with heat flux, liquid subcooling, and submergence is proposed.

Ali, H.; Alam, S.S. (Dept. of Chemical Engineering, Aligarh Muslim Univ., Aligarh 202 002 (IN))

1991-03-01

105

Pool boiling from rotating and stationary spheres in liquid nitrogen  

NASA Technical Reports Server (NTRS)

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.

Cuan, Winston M.; Schwartz, Sidney H.

1988-01-01

106

Transient Heat Transport in Subcooled He II Associated with JT Effect  

SciTech Connect

Transient heat transport in subcooled He II has been investigated in a 1 m long rectangular channel with distributed contractions: one-closed end has a heater, while the other end is open to the He II bath. Experiments were conducted applying heat pulses and recording the temperature profile with seven Allan Bradley resistors placed along the channel. Cernox sensor was indium soldered on the heater surface to monitor the onset of film boiling. As the onset of heat pulse, the pressure at the heater surface increased because of phase change from subcooled He II to He I. Further increasing of heat pulse leads to coexistence of triple-phase, He I vapor layer, He I and subcooled He II, at the vicinity of heater surface. These effects induced instantaneous He II temperature drop along the channel, which is caused by Joule-Thomson (JT) effect. A simple model gives an approximate mechanism of pressure increase in the channel. The paper describes transient heat transport mechanism in the channel and discusses JT effect within the channel.

Maekawa, R.; Iwamoto, A.; Hamaguchi, S. [National Institute for Fusion Science, Toki, Gifu 509-5292 (Japan)

2004-06-23

107

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

SciTech Connect

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.

Martin-Dominguez, I.R. [Inst. Politecnico Nacional-CIIDIR Unidad Durango, Durango City (Mexico); McDonald, T.W. [Univ. of Windsor, Ontario (Canada)

1997-12-31

108

An experimental research on microbubble emission boiling  

NASA Astrophysics Data System (ADS)

In the near future, heat transfer technology with higher performance surely has more application in the field of thermal engineering, such as electrical chip cooling, power regulating system, etc. Microbubble emission boiling (MEB) is getting more attentions by many researchers due to its extremely high heat dissipation capacity and potential application in the areas mentioned above. Despite that much work has been done to MEB, heat transfer characteristics and occurrence condition as well as formation mechanism involved MEB are not illustrated clearly by far. An experimental setup is built up to study MEB visually. The heating element is a cone copper block with its upper part of a 10mm diameter cylinder which is insulated from the water by a ceramic thimble. The different liquid subcooling is obtained by a water cooler combined with an electric heater. A high-speed video camera (Photron: Fastcam SA5) is employed for recording the scenario of MEB. Our experimental results are very similar to that from other researchers, and the maximum heat flux is about 9 MW/m2 at 60K subcooling. The presence of noncondensable gas in the vapor film and the liquid subcooling has obviously impact on MEB. Moreover, numerical simulation results show that marangoni convection is perhaps one of the reasons inducing the occurrence of MEB.

Tang, Jiguo; Zhu, Guangyu; Sun, Licheng; Cao, Xiaxin

2013-07-01

109

AN EXPERIMENTAL INVESTIGATION ON FLOW BOILING OF ETHYLENE-GLYCOL/WATER MIXTURE  

E-print Network

AN EXPERIMENTAL INVESTIGATION ON FLOW BOILING OF ETHYLENE-GLYCOL/WATER MIXTURE Satish G. Kandlikar Phone: 716-475-6728 Fax: 716-475-7710 SGKEME@RIT.EDU ABSTRACT Mixtures of ethylene glycol and water, the mixture is subcooled in the radiator before entering the engine block. Heat transfer is therefore

Kandlikar, Satish

110

Boiling heat transfer in reduced gravity during quenching of a hot surface with R-113  

SciTech Connect

An experimental study of the flow boiling heat transfer characteristics under microgravity conditions is presented. The experiments were conducted using R-113 by rewetting a heated bottom plate of a rectangular channel, 40 mm wide, 5 mm high and 200 mm long, aboard the KC-135 parabolic aircraft. The local surface heat flux and temperature were measured by a 2-{micro}m thick micro sensor directly fabricated on the surface of the heated plate. The film boiling heat transfer coefficients in microgravity were 70% to 80% of the values in normal gravity, and the results in both gravity conditions showed reasonable agreement with the predictions of Bromley (1953) correlation. Under microgravity, the flow rate had less effect but subcooling had a significant effect on nucleate boiling heat transfer. The effect of microgravity is similar to that due to the absence of subcooling in normal gravity, because both result in a thicker and more stable vapor layer. Also, the nucleate boiling regime covered a wider range of wall superheat below the maximum heat flux in the absence of gravity or subcooling than in the case of high subcooling and normal gravity.

Xu, J.J.; Adham-Khodaparast, K.; Kawaji, M. [Univ. of Toronto, Ontario (Canada). Dept. of Chemical Engineering and Applied Chemistry

1995-12-31

111

Experimental study and modeling of nucleate boiling during free planar liquid jet impingement  

Microsoft Academic Search

Determination of boiling heat transfer rate during liquid jet impingement cooling (LJIC) depends on the intensity of bubble generation that is dependent on many flow and surface conditions such as jet velocity, liquid temperature, and surface superheat. Many empirical correlations have been developed previously to determine the total wall heat flux under various LJIC flow velocity, subcooling and surface superheat.

Ahmed M. T Omar

2010-01-01

112

Some parameter boundaries governing microgravity pool boiling modes.  

PubMed

Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a matrix of three levels of imposed heat flux and three levels of initial bulk liquid subcooling. In many of the total of 45 experiments, steady nucleate boiling was observed from 16-mm movie films, where a large vapor bubble formed and remained slightly removed from the heater surface, with small vapor bubbles growing on the heater surface, and on contact coalescing with the large bubble. Computations of the forces associated with the momentum transfer in this process, which counters the Marangoni convection effects tending to impel the large bubble toward the heater surface, have been completed for all cases where applicable. The modes of pool boiling observed with successive increases in levels of heat flux in microgravity are categorized as: (i) minimum or incipient nucleate boiling; (ii) nucleate boiling with vigorous motion of the bubbles adjacent and parallel to the heater surface, impelled by Marangoni convection effects; (iii) nucleate boiling followed by coalescence with a neighboring large vapor bubble; (iv) partial dryout of the heater surface, in parallel with nucleate boiling; (v) complete dryout. The boundaries between these modes are delineated graphically as a function of the imposed heat flux and initial bulk liquid subcooling, together with the levels of the forces holding the large bubbles, acting as vapor reservoirs, away from the heater surface for the steady nucleate boiling mode. PMID:17124149

Merte, Herman

2006-09-01

113

Boiling heat transfer of impacting liquid sprays on solid surfaces  

SciTech Connect

The nucleate spray boiling region and the film spray boiling region were investigated. In the nucleate regime, an exploratory experimental investigation was carried out with a unique spray generator which allowed independent control over the spray parameters. The liquids used in the study were water and FC-72,a dielectric fluid, and the surface was copper. Parametric studies revealed that the liquid mass flux and the liquid subcooling were the main parameters which affect nucleate spray boiling, while droplet parameters had little effect. Even under peak heat flux conditions, a large fraction of the sprayed liquid remained unvaporized. However, peak heat fluxes obtained were much higher than those for pool boiling and seem to be of the same order as free impinging jet boiling. The problem of temperature overshoot at boiling incipience was carefully checked for impacting liquid sprays. No evidence of it was found. For the film boiling region of impacting sprays, analysis of this complex heat transfer process was attempted by separating the region into dilute and dense sprays. The heat transfer of an impacting dilute spray was analyzed by dividing the process into three identified subprocesses-drop contact heat transfer, bulk air convective heat transfer and radiative heat transfer. Since the dense spray film boiling region is complicated tremendously by the presence of interaction, the approach found successful was to identify, analyze and predict the asymptotic conditions.

Deb, S.

1988-01-01

114

Multi-mode methanol flow boiling under atmospheric and subatmospheric pressures  

SciTech Connect

This is a continuation work of Lin and Lee (1996 National Heat Transfer Conference, Houston) while reporting the experimental results of multi-mode methanol flow boiling under atmospheric and subatmospheric pressures. An axial (discrete) heat flux distribution with neutral stability at which nucleate and film boiling can coexist steadily is identified under various system pressures and crossflow rates. Below this heat flux distribution, nucleate boiling mode is more stable. Above this distribution, film boiling becomes the more stable mode. An equal-area criterion based on the difference between bottom heat flux and surface boiling heat flux, and the wall superheat temperature relationship is employed for interpreting the experimental data. Effects of system pressure, mass flowrate, liquid subcooling and bottom heat flux on the relative stability of nucleate and film boiling modes are discussed.

Lin, W.W.; Liao, Y.C.; Lee, D.J. [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Chemical Engineering

1996-12-31

115

Mechanisms of steady-state nucleate pool boiling in microgravity.  

PubMed

Research on nucleate pool boiling in microgravity using R-113 as a working fluid was conducted using a five-second drop tower and five space flights at a/g approximately 10(-4). A 19 x 38-mm flat gold film heater was used that allowed cine camera viewing both from the side and the bottom of the heater. It was concluded that for both subcooled and saturated liquids long-term steady-state pool boiling can take place in reduced gravity, but the effectiveness of the boiling heat transfer appears to depend on the heater geometry and on the size and the properties of fluids. Heat transfer is enhanced at lower heat flux levels and the CHF increases as the subcooling increases. It was found that several mechanisms are responsible for the steady-state nucleate pool boiling in the absence of buoyancy. The mechanisms considered here are defined and summarized as bubble removal, bubble coalescence, thermocapillary flow, bubble migration, and latent heat transport. PMID:12446341

Lee, Ho Sung

2002-10-01

116

Boil, Boil, Toil and Trouble: The International Boiling Point Project  

NSDL National Science Digital Library

People from all over the world boil water at different elevations and post data to discover which factor in the experiment (room temperature, elevation, volume of water, or heating device) has the greatest influence on boiling point. Anyone can boil water, record information, and send it in for inclusion in the database of results. Students can analyze all the data to answer the question: What causes a pot of water to boil? Participation is invited at any time during the project's three-month span. Developed and managed by the Center for Improved Engineering and Science Education (CIESE) at Stevens Institute of Technology in Hoboken, NJ.

Forum, Math; Center for Improved Engineering and Science Education (CIESE)

2001-01-01

117

Dive and Discover's Deeper Discovery: Hydrothermal Vents  

NSDL National Science Digital Library

Dive and Discover is an interactive distance learning web site designed to immerse you in the excitement of discovery and exploration of the deep seafloor. On this particular website, Dive and Discover takes you on a deeper discovery of hydrothermal vents. This site features an introduction to hydrothermal vent systems, including vent basics, vents around the world, chemistry, boiling points, interactive diagrams, videos, a quiz, and links to selected Dive and Discover hydrothermal vent-related seafloor expeditions. This web page also provides links to other Deeper Discovery topics, Dive and Discover seafloor expeditions, a teacher's page, and further Dive and Discover information.

2010-04-12

118

A model for correlating flow boiling heat transfer in augmented tubes and compact evaporators  

SciTech Connect

The additive model for the convective and nucleate boiling components originally suggested by Bergles and Rohsenow (1964) for subcooled and low-quality regions was employed in the Kandlikar correlation (1990a) for flow boiling in smooth tubes. It is now extended to augmented tubes and compact evaporators. Two separate factors are introduced in the convective boiling and the nucleate boiling terms to account for the augmentation effects due to the respective mechanisms. The fin efficiency effects in the compact evaporator geometry are included through a reduction in the nucleate boiling component over the fins due to a lower fin surface temperature. The agreement between the model predictions and the data reported in the literature is within the uncertainty bounds of the experimental measurements.

Kandlikar, S.G. (Massachusetts Inst. of Tech., Cambridge (United States))

1991-11-01

119

Thermal subcoolers for low-thrust chemical orbital transfer vehicles  

NASA Technical Reports Server (NTRS)

A system alternative to pressurization for providing net positive suction pressure (NPSP) to the main engine of a low-thrust cryogenic stage has been conceptually designed and analyzed. Thermal subcoolers (heat exchangers) provide required NPSP levels by using throttled vent fluid to subcool propellant delivered to the engine. The study analyzed and sized subcoolers that provide NPSP levels of 0.5 to 12.0 psi for liquid oxygen, liquid hydrogen, and liquid methane propellants. The study was part of an overall investigation to compare pressurization and other methods of providing NPSP for low-thrust vehicles.

Pleasant, R. L.; Aydelott, J. C.

1981-01-01

120

Hydrothermal Processes  

Microsoft Academic Search

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

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

2003-01-01

121

A Study of Nucleate Boiling with Forced Convection in Microgravity  

NASA Technical Reports Server (NTRS)

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 p

Merte, Herman, Jr.

1999-01-01

122

Low velocity nucleate flow boiling at various orientations  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

123

The Effect of vapor subcooling on film condensation of metals  

E-print Network

This work presents an analysis of the interfacial "vapor-condensate" temperature distribution, which includes the effect of subcooling (supersaturation) in the vapor. Experimental data from previous investigators for ...

Fedorovich, Eugene D.

1968-01-01

124

The mechanism of void formation in initially subcooled systems  

E-print Network

When an initially subcooled, water filled system undergoes a transient in heat flux or pressure such that bubbles form, the most important variable which determines the volume of the resulting void is the number of bubbles ...

Griffith, P.

1963-01-01

125

Two-phase structure above hot surfaces in jet impingement boiling  

NASA Astrophysics Data System (ADS)

Jet impingement boiling is very efficient in cooling of hot surfaces as a part of the impinging liquid evaporates. Several studies have been carried out to measure and correlate the heat transfer to impinging jets as a function of global parameters such as jet subcooling, jet velocity, nozzle size and distance to the surface, etc. If physically based mechanistic models are to be developed, studies on the fundamentals of two-phase dynamics near the hot surface are required. In the present study the vapor-liquid structures underneath a subcooled (20 K) planar (1 mm × 9 mm) water jet, impinging the heated plate vertically with a velocity of 0.4 m/s, were analyzed by means of a miniaturized optical probe. It has a tip diameter of app. 1.5 ?m and is moved toward the plate by a micrometer device. The temperature controlled experimental technique enabled steady-state experiments in all boiling regimes. The optical probe data provides information about the void fraction, the contact frequencies and the distribution of the vapor and liquid contact times as a function of the distance to the surface. The measured contact frequencies range from 40 Hz at the onset of nucleate boiling to nearly 20,000 Hz at the end of the transition boiling regime. Due to condensation in the subcooled jet vapor disappears at a distance to the surface of app. 1.2 mm in nucleate boiling. This vapor layer becomes smaller with increasing wall superheat. In film boiling a vapor film thickness of 8 ± 2 ?m was found.

Bogdanic, L.; Auracher, H.; Ziegler, F.

2009-05-01

126

PII S0016-7037(99)00441-X Sub sea floor boiling of Red Sea Brines: New indication from noble gas data  

E-print Network

PII S0016-7037(99)00441-X Sub sea floor boiling of Red Sea Brines: New indication from noble gas boiling during the hydrothermal circulation and subsequent phase separation is shown to be a consistent, where it becomes enriched in HeMORB and ArMORB, the ascending fluid boils, and the residual liquid

Winckler, Gisela

127

Experimental Two-Phase Flow Characterization of Subcooled Boiling in a Rectangular Channel  

E-print Network

channel with one heated wall. Measurements were performed at liquid Reynolds numbers of 3309, 9929 and 16549 over a wall heat flux range of 0.0 to 64.0 kW=m 2. From the PTV measurements, liquid two dimensional turbulence statistics are available, such as...

Estrada Perez, Carlos E.

2010-01-16

128

Study of Mechanism of Initial Crud Formation on Fuel Cladding in Subcooled Boiling Region in PWR  

SciTech Connect

A hemispherical vapor bubble model has been constructed, and thermo-capillary flow driven by surface tension gradient, due to temperature difference, around bubble attached to a plane heated surface, and it has been examined using numerical methods. LiOH solute concentration distribution around the bubble has been obtained. Some parameters under PWR operating conditions have been discussed: bubble size, mass diffusion coefficient and vapor heat transfer coefficient. Effects of some important parameters, such as heat flux and bubble size, have been examined. The study shows that the thermo-capillary flow around a static hemispherical vapor bubble can not generate sufficient solute concentrations to initialize crud formation under PWR operating condition. (authors)

Rao, Qinyang; Jones, Barclay G. [University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

2002-07-01

129

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

SciTech Connect

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)

Wu, Wen; Jones, Barclay G. [University of Illinois at Urbana-Champaign, 104 South Wright Street, Urbana, IL 61801 (United States)

2002-07-01

130

Experimental verification of subcooled flow boiling for tokamak pump limiter designs  

Microsoft Academic Search

In fusion energy research devices such as tokamaks, limiters are used to define the plasma boundary, and may serve the additional functions of plasma density and impurity control by removing neutralized particles from the plasma edge region. Because the devices must operate in the plasma edge or ''scrape-off-layer,'' they are subject to high heat fluxes. In this paper, experimental studies

J. A. Koski; A. G. Beattie; J. B. Whitley; C. D. Croessmann

1987-01-01

131

Effects of ultrasonic waves on the heat transfer enhancement in subcooled boiling  

Microsoft Academic Search

This work represents an experimental basic research aimed to investigate the influence on the heat transfer rate of the ultrasounds, in free convection and in presence of liquid. In fact the ultrasonic waves induce, thanks to vibrations, turbulence on the dynamic field, and so an increase of the convection coefficient. The heater is a circular cylinder, immersed in distilled water,

Carlo Bartoli; Federica Baffigi

2011-01-01

132

Microchannel cooling with subcooled boiling: Executive summary of first year's results  

SciTech Connect

During the first year's effort, we started with we felt to be the most critical problem: namely, the prediction of the point of bubble departure, BD (also referred to as the point of onset of significant net vapor generation, OSNVG). Mr. Stetson started work on the project in January 1990, when the funding was officially received, and spend some time becoming acquainted with the SCB-1A code. Then he examined the models of Saha Zuber, Levy and Staub for the location of the BD point and the models of Rohani, Levy and Staub for the size of the bubble at the BD point. (1) At the present time, the best model to use to predict the ONSVG point for sub-millimeter diameter tubes appears to be the Saha-Zuber correlation. Data in channels with hydraulic diameters from about 24 mm down to about 1 mm agree with the correlation to within about {plus minus}25%. (2) It is not at all clear which is the best correlation to use to predict the average bubble diameter at the OSNVG point in sub-millimeter diameter tubes. We have decided to retain the modified Rouhani correlation in the code for the time being, recognizing that it is probably inadequate. We will also compare predictions of the heat transfer performance in small sub-millimeter diameter tubes using the bubble departure diameters from the modified Rouhani correlation to those using modified Staub model. 16 refs., 24 figs.

Hoffman, M.A.

1990-09-01

133

Performance of extended surface from a cryocooler for subcooling liquid nitrogen by natural convection  

E-print Network

May 2005; accepted 25 May 2005 Abstract Natural convection of subcooled liquid nitrogen under that subcooled liquid may generate cellular flow by natural convection. The temperature distributions and efficient cooling systems by natural convection of subcooled liquid nitrogen have been reported [3�5]. Chang

Chang, Ho-Myung

134

A study of forced convection boiling under reduced gravity  

NASA Technical Reports Server (NTRS)

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?

Merte, Herman, Jr.

1992-01-01

135

Rapid vaporization of subcooled liquid in a capillary structure  

E-print Network

for rapid vaporization of subcooled liquid in a capillary structure. The process consists of a low-thermal thermal conductivity of the capillary structure and the presence of the extremely steep temperature therapy, steam cooking, steam hair setting, steam irons, presses and wallpaper strippers and the like

Zhao, Tianshou

136

Boiling Time and Temperature  

NSDL National Science Digital Library

The purpose of this assessment probe is to elicit students' ideas about the characteristic property of boiling point. The probe is used to find out whether students recognize that the temperature of a boiling liquid stays constant no matter how long heat is applied.

Eberle, Francis; Tugel, Joyce; Keeley, Page

2007-01-01

137

Suppression of bubbles in subcooled liquid nitrogen under heat impulse Kwanwoo Nam a,*, Bok-Yeol Seok a  

E-print Network

Suppression of bubbles in subcooled liquid nitrogen under heat impulse Kwanwoo Nam a,*, Bok investigation to verify that subcooling of liquid nitrogen can suppress bubbles when an impul- sive heat is that the generation of bubbles is less active in subcooled state than in saturated state. The subcooling of liquid

Chang, Ho-Myung

138

Saturated flow boiling of water in a narrow channel: time-averaged heat transfer coefficients and correlations  

Microsoft Academic Search

Time-averaged local heat transfer coefficients were measured during flow boiling of water at atmospheric pressure in a vertical channel of rectangular cross-section 2 mm by 1 mm for ranges of mass flux 57–211 kg\\/m2s, heat flux 27–160 kW\\/m2, thermodynamic quality 0–0.3 and inlet subcooling 1–12 K. The heat transfer coefficients were found to increase nearly with the square root of

D. S. Wen; Youyou Yan; D. B. R. Kenning

2004-01-01

139

Hydrothermal Processes  

NASA Astrophysics Data System (ADS)

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 Atlanti

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

2003-12-01

140

International Boiling Point Project  

NSDL National Science Digital Library

The purpose of this project is to discover which factor in the experiment (room temperature, elevation, volume of water, or heating device) has the greatest influence on boiling point. Anyone can participate in this year's project. All you have to do is boil a bit of water, record a bit of information, and send it along to the website to have your results included in the database of results. Then, students can analyze all of the data to reach an answer to the question: What causes a pot of water to boil?

2009-01-01

141

Upgrading of high boiling hydrocarbons  

SciTech Connect

A process is described for upgrading a high boiling hydrocarbon, comprising: deasphalting the high boiling hydrocarbon to recover as separate fractions, deasphalted oil, resin and pitch; upgrading the resin fraction to produce an effluent containing upgraded product and high boiling components; recovering high boiling components from the effluent; subjecting the deasphalting at least a portion of the recovered high boiling components to reject coke precursors in the (pitch fraction) high boiling components portion prior to recycle thereof to the upgrading with the resin fraction; and thereafter recycling the high boiling components portion with the resin fraction to the upgrading.

Van Driesen, R.P.; Friday, J.R.

1987-08-11

142

SATURATED-SUBCOOLED STRATIFIED FLOW IN HORIZONTAL PIPES  

SciTech Connect

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.

Richard Schultz

2010-08-01

143

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

NASA Technical Reports Server (NTRS)

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.

Kugler, Scott Lee

1997-01-01

144

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

145

Nucleate pool boiling in the long duration low gravity environment of the space shuttle  

NASA Technical Reports Server (NTRS)

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/so 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/so m. The wall superheat at the inception of boiling varied between 2 to 13 C.

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

1993-01-01

146

Boiling of multicomponent liquid mixtures  

SciTech Connect

This article reviews the significant advances in the understanding of the boiling process germane to mixtures. The scope of this review is limited to miscible systems. The effects of impurities (such as lubricating oils in refrigerants), surfactants, soluble salts, and dissolved gases are excluded from consideration. Both pool and convective boiling are addressed. The ultimate goals of the study of boiling of liquid mixtures are: to predict the superheat required for the inception of boiling, to predict their heat transfer coefficients with a reasonable degree of accuracy, and to predict the variation in the peak nucleate and dry out heat fluxes with composition. These goals are closer to being met for pool boiling than they are for convective boiling. The topics discussed in this survey are presented in much the same order as when an increasing heat flux is applied to a surface to cause boiling. Thus bubble nucleation or boiling incipience is considered first, since this defines the criteria required for boiling to commence. Then the growth of the vapor bubbles from vapor nuclei up to and including their departure from the surface is discussed. This is followed by a survey of the heat transfer mechanisms, resulting from the vaporization process, which affect the nucleate pool boiling curve, and this leads to a discussion of equations for predicting nucleate pool boiling heat transfer coefficients. The peak nucleate heat flux in pool boiling is examined prior to a description of film boiling. Several aspects of convective boiling are then presented.

Thome, J.R.; Shock, R.A.W.

1984-01-01

147

Flow boiling of water on nanocoated surfaces in a microchannel  

E-print Network

Experiments were performed to study the effects of surface wettability on flow boiling of water at atmospheric pressure. The test channel is a single rectangular channel 0.5 mm high, 5 mm wide and 180 mm long. The mass flux was set at 100 kg/m2 s and the base heat flux varied from 30 to 80 kW/m2. Water enters the test channel under subcooled conditions. The samples are silicone oxide (SiOx), titanium (Ti), diamond-like carbon (DLC) and carbon-doped silicon oxide (SiOC) surfaces with static contact angles of 26{\\deg}, 49{\\deg}, 63{\\deg} and 103{\\deg}, respectively. The results show significant impacts of surface wettability on heat transfer coefficient.

Phan, Hai Trieu; Marty, Philippe; Colasson, Stéphane; Gavillet, Jérôme

2010-01-01

148

Controlling fuel assembly stability in a boiling water reactor  

SciTech Connect

A method is described for controlling the stability of the fuel assemblies in a boiling water reactor core comprising the steps of: (a) monitoring on an on-line basis the values of selected reactor parameters including, flow, inlet subcooling, control rod position, and pressure; (b) determining on a real time basis from the selected reactor parameters, the power generated in, and the axial power distribution for, each fuel assembly; (c) selecting fuel assemblies with axial power peaking occurring below a predetermined location as determined from the axial power distributions, and with a power level above a selected value; (d) calculating on-line in a digital computer a stability index only for the selected fuel assemblies; and (e) generating a human readable representation of the stability indexes in real time for the selected fuel assemblies.

Taleyarkhan, R.P.

1988-09-13

149

Momentum effects in steady nucleate pool boiling during microgravity.  

PubMed

Pool boiling experiments were conducted in microgravity on five space shuttle flights, using a flat plate heater consisting of a semitransparent thin gold film deposited on a quartz substrate that also acted as a resistance thermometer. The test fluid was R-113, and the vapor bubble behavior at the heater surface was photographed from beneath as well as from the side. Each flight consisted of a matrix of three levels of heat flux and three levels of subcooling. In 26 of the total of 45 experiments conditions of steady-state pool boiling were achieved under certain combinations of heat flux and liquid subcooling. In many of the 26 cases, it was observed from the 16-mm movie films that a large vapor bubble formed, remaining slightly removed from the heater surface, and that subsequent vapor bubbles nucleate and grow on the heater surface. Coalescence occurs upon making contact with the large bubble, which thus acts as a vapor reservoir. Recently, measurements of the frequencies and sizes of the small vapor bubbles as they coalesced with the large bubble permitted computation of the associated momentum transfer. The transient forces obtained are presented here. Where these arise from the conversion of the surface energy in the small vapor bubble to kinetic energy acting away from the solid heater surface, they counter the Marangoni convection due to the temperature gradients normal to the heater surface. This Marangoni convection would otherwise impel the large vapor bubble toward the heater surface and result in dryout and unsteady heat transfer. PMID:15644357

Merte, Herman

2004-11-01

150

Physical interpretation of geysering phenomena and periodic boiling instability at low flows  

SciTech Connect

Over 30 years ago, Griffith showed that unstable and periodic initial boiling occurred in stagnant liquids in heated pipes coupled to a cooler or condensing plenum volume. This was called ``geysering``, and is a similar phenomenon to the rapid nucleation and voiding observed in tubes filled with superheated liquid. It is also called ``bumping`` when non-uniformly heated water or a chemical suddenly boils in laboratory glassware. In engineering, the stability and predictability has importance to the onset of bulk boiling in a natural and forced circulation loops. The latest available data show the observed stability and periodicity of the onset of boiling flow when there is a plenum, multiple heated channels, and a sustained subcooling in a circulating loop. We examine the available data, both old and new, and develop a new theory to illustrate the simple physics causing the observed periodicity of the flow. We examine the validity of the theory by comparison to all the geysering data, and develop a useful and simple correlation. We illustrate the equivalence of the onset of geysering to the onset of static instability in subcooled boiling. We also derive the stability boundary for geysering, utilizing turbulent transport analysis to determine the effects of pressure and other key parameters. This new result explains the greater stability region observed at higher pressures. The paper builds on the 30 years of quite independent thermal hydraulic work that is still fresh and useful today. We discuss the physical interpretation of geysering onset with a consistent theory, and show where refinements would be useful to the data correlations.

Duffey, R.B.; Rohatgi, U.S.

1996-03-01

151

Sand boils without earthquakes  

USGS Publications Warehouse

Sedimentary deformation caused by liquefaction has become a popular means for inferring prehistoric strong earthquakes. This report describes a new mechanism for generating such features in the absence of earthquakes. Sand boils and a 180-m-long sand dike formed in Fremont Valley, California, when sediment-laden surface runoff was intercepted along the upslope part of a 500-m-long preexisting ground crack, flowed subhorizonally in the crack, and then flowed upward in the downslope part of the crack where it discharged as sand boils on the land surface. If the sand boils and their feeder dike were stratigraphically preserved, they could be misinterpreted as evidence for earthquake-induced liquefaction. -Authors

Holzer, T. L.; Clark, M. M.

1993-01-01

152

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

NASA Technical Reports Server (NTRS)

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.

Cuan, Winston M.; Schwartz, Sidney H.

1988-01-01

153

Pool film boiling from rotating and stationary spheres in liquid nitrogen  

NASA Astrophysics Data System (ADS)

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.

Cuan, Winston M.; Schwartz, Sidney H.

1988-07-01

154

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

SciTech Connect

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.

Amos, C N; Schrock, V E

1983-09-01

155

Is subcooling the right driving force for testing low-dosage hydrate inhibitors?  

Microsoft Academic Search

The degree of subcooling is usually used as the driving force for hydrate formation; however, it does not encompass the effect of pressure. A comprehensive driving force for hydrate formation is a function of pressure, temperature, and gas composition; however, its calculation is not as simple as that of subcooling. In this work, by application of the two latest driving

Mosayyeb Arjmandi; Bahman Tohidi; Ali Danesh; Adrian C. Todd

2005-01-01

156

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

157

Mercury isotope fractionation in fossil hydrothermal systems  

NASA Astrophysics Data System (ADS)

The Hg isotopic compositions of samples throughout the vertical extent of two fossil hydrothermal systems were analyzed by multicollector inductively coupled plasma mass spectrometry. Results show >5‰ (?202Hg/198Hg; relative to NIST 3133) fractionation, more than 50 times greater than the 0.1‰ (2?) external reproducibility of the analyses. The Hg isotope compositions from both hydrothermal systems can be grouped by dominant mineralogy and position; ?202Hg/198Hg values at the tops of the systems are -3.5‰ to -0.4‰ in cinnabar-dominant sinter and -0.2‰ to +2.1‰ in metacinnabar-dominant sinter, and the underlying veins have ?202Hg/198Hg values of -1.4‰ to +1.3‰. These differences probably resulted from the combination of boiling of the hydrothermal fluid, oxidation near the surface, and kinetic effects associated with mineral precipitation. The natural variation in Hg isotopic compositions observed in this study is higher than that expected from the trend of decreasing mass-dependent fractionation with increasing mass extrapolated from stable isotope systems up to Z = 26 (Fe), confirming that even the heaviest elements undergo significant stable isotope fractionation in hydrothermal systems.

Smith, Christopher N.; Kesler, Stephen E.; Klaue, Björn; Blum, Joel D.

2005-10-01

158

Diversity of Archaeal Consortia in an Arsenic-Rich Hydrothermal System  

Microsoft Academic Search

Characterizing microbial communities within their geochemical environment is essential to understanding microbial distribution and microbial adaptations to extreme physical and chemical conditions. The hydrothermal waters at El Tatio geyser field demonstrate extreme conditions, with water at local boiling (85°C), arsenic concentrations at 0.5 mM, and inorganic carbon concentrations as low as 0.02mM. Yet many of El Tatio's hundred plus hydrothermal

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

2008-01-01

159

Large-scale hydrothermal fluid discharges in the Norris–Mammoth corridor, Yellowstone National Park, USA  

Microsoft Academic Search

Norris–Mammoth corridor is a complex subsidence structure that extends ?40km northward from the 0.6Ma Yellowstone caldera, and contains many hydrothermal features with high fluid discharges totaling ?1000l\\/s. About 150–250l\\/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

Y. K. Kharaka; M. L. Sorey; J. J. Thordsen

2000-01-01

160

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

NASA Astrophysics Data System (ADS)

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.

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

2006-12-01

161

Sedimentation and convective boiling heat transfer of CuO-water/ethylene glycol nanofluids  

NASA Astrophysics Data System (ADS)

The convective boiling characteristics of dilute dispersions of CuO nanoparticles in water/ethylene glycol as a base fluid were studied at different operating conditions of (heat fluxes up to 174 kW m-2, mass fluxes range of 353-1,059 kg m-2 s-1 and sub-cooling level of 343, 353 and 363 K) inside the annular duct. The convective boiling heat transfer coefficients of nanofluids in different concentrations (vol%) of nanoparticles (0.5, 1, and 1.5) were also experimentally quantified. Results demonstrated the significant augmentation of heat transfer coefficient inside the region with forced convection dominant mechanism and deterioration of heat transfer coefficient in region with nucleate boiling dominant heat transfer mechanism. Due to the scale formation around the heating section, fouling resistance was also experimentally measured. Experimental data showed that with increasing the heat and mass fluxes, the heat transfer coefficient and fouling resistance dramatically increase and rate of bubble formation clearly increases. Obtained results were then compared to some well-known correlations. Results of these comparisons demonstrated that experimental results represent the good agreement with those of obtained by the correlations. Consequently, Chen correlation is recommended for estimating the convective flow boiling heat transfer coefficient of dilute CuO-water/ethylene glycol based nanofluids.

Sarafraz, M. M.; Hormozi, F.; Kamalgharibi, M.

2014-09-01

162

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

SciTech Connect

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)

Bang, In Cheol; Chang, Soon Heung [Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong, Yuseong-gu, Daejeon, 305-701 (Korea, Republic of); Baek, Won-Pil [Korea Atomic Energy Research Institute, 150, Dukjin-dong, Yuseong-gu, Daejeon, 305-353 (Korea, Republic of)

2002-07-01

163

Initiation of Water Hammer in Horizontal or Nearly-Horizontal Pipes Containing Steam and Subcooled Water.  

National Technical Information Service (NTIS)

Water slug formation in a stratified countercurrent flow of steam and subcooled water in a horizontal or nearly horizontal pipe traps a large steam bubble, which then collapses rapidly and causes a water hammer. This water hammer initiating mechanism has ...

R. W. Bjorge

1983-01-01

164

METEORIC-HYDROTHERMAL SYSTEMS.  

USGS Publications Warehouse

This paper summarizes the salient characteristics of meteoric-hydrothermal systems, emphasing the isotopic systematics. Discussions of permeable-medium fluid dynamics and the geology and geochemistry of modern geothermal systems are also provided, because they are essential to any understanding of hydrothermal circulation. The main focus of the paper is on regions of ancient meteoric-hydrothermal activity, which give us information about the presently inaccessible, deep-level parts of modern geothermal systems. It is shown oxygen and hydrogen isotopes provide a powerful method to discover and map fossil hydrothermal systems and to investigate diverse associated aspects of rock alteration and ore deposition.

Criss, Robert, E.; Taylor, Jr. , Hugh, P.

1986-01-01

165

A study of electrowetting-assisted boiling  

E-print Network

The classical theory of boiling heat transfer based on bubble dynamics is explained and includes a full derivation of the Rohsenow boiling correlation. An alternative, more accurate correlation for determining boiling heat ...

Bralower, Harrison L. (Harrison Louis)

2011-01-01

166

Boiling Fluids Behave Quite Differently in Space  

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...

167

Boiling liquid cauldron status report  

SciTech Connect

The progress made over the past year in assessing the feasibility of the high-temperature, boiling cauldron blanket concept for the tanden mirror reactor is reviewed. The status of the proposed experiments and recently revised estimates of the vapor void fraction in the boiling pool are discussed.

Hoffman, M.A.

1980-12-28

168

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

SciTech Connect

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.

Aksan, S.N.; Stierli, F.; Analytis, G.T. [Paul Scherrer Inst. (PSI), Villigen (Switzerland). Lab. for Thermal-Hydraulics

1992-03-01

169

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

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.

Yu, W.; France, D. M.; Routbort, J. L. (Energy Systems)

2011-01-19

170

Steam-air mixture condensation in a subcooled water pool  

NASA Astrophysics Data System (ADS)

In any conceptual reactor design under postulated accidental conditions, one parameter that is considered as being highly ranked in determining the thermal-hydraulic conditions of the reactor safety components is the system pressure. To obtain a satisfactory prediction of steam partial pressure, within reasonable uncertainty in the gas space of a confined SP (suppression pool) bounded to the steam source of the break flow, one must establish a means by which local phenomena associated with steam direct contact condensation in the subcooled water pool can be fully addressed to predict the global component thermal response. For this purpose a scaled down, reduced pressure, suppression pool was designed and built to study condensation and mixing phenomena. The scaled test facility represented an idealized trapezoidal cross section, 1/10 sector of the SP with scaled height ratio of 1/4.5 and volume ratio of 1/400. The design and test conditions were based on a hierarchical scaling principle that preserves the transfer of mass, momentum, energy and condensation phenomena. Distributed thermocouples within the pool provided a means to quantify the pool thermal response. The test loop was not only instrumented with thermocouples for monitoring pool stratification but also with high speed photography for flow visualization from which to build a comprehensive database to identify the regions of the pool that were thermally stratified or mixed. Data were obtained for different pool initial subcooling and steam/air mixture flow rates. Dimensionless boundary maps were plotted from several experimental runs of pure steam injection to determine conditions when the pool transits from being homogeneously mixed to being thermally stratified. Steam-air mixture injection cases for single horizontal venting indicated that above a pool temperature of 40°C with airmass flow rates below 0.1 g/s the pool can attain thermal stratification. Models of a single phase liquid-into-liquid buoyant jet and a two-phase vapor-into-liquid turbulent jet plume injected in horizontal orientation were developed from the Reynolds averaged Navier-Stokes equations in the cylindrical system for steady axisymmetric flow and incorporated the integral plume theory. The two-phase simplified model developed to predict the pool surface temperature to within less than 0.5°C in the majority of cases.

Norman, Timothy Linhurst

171

Acidic dissolution of plagioclase: in-situ observations by hydrothermal atomic force microscopy  

Microsoft Academic Search

Hydrothermal atomic force microscopy (HAFM) provides in situ access to the surfaces of dissolving crystals at temperatures above the ambient boiling point of water. Here, we applied HAFM to the (001) surfaces of labradorite and anorthite at temperatures up to 125°C. In HCl solutions (pH 2) we observed the formation of a rough and soft surface layer on both minerals.

Guntram Jordan; S TEVEN R. HIGGINS; CARRICK M. EGGLESTON; SUSAN M. SWAPP; DAWN E. JANNEY; KEVIN G. KNAUSS

1999-01-01

172

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

SciTech Connect

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.

Liu, C.; Theofanous, T. G.

2000-08-29

173

Film boiling of mercury droplets  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

174

Film boiling of mercury droplets  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

175

High flux film and transition boiling  

SciTech Connect

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.

Witte, L.C.

1990-01-01

176

Boiling Radial Flow in Fractures of Varying  

E-print Network

SGP-TR-166 Boiling Radial Flow in Fractures of Varying Wall Porosity Robb Allan Barnitt June 2000 and boiling convective heat transfer, with boiling flow in a rock fracture. A series of experiments observed. The experimental study involved boiling radial flow in a simulated fracture, bounded by a variety of materials

Stanford University

177

Jet flow phenomena during nucleate boiling  

Microsoft Academic Search

Boiling phenomena are with highly complex nonlinear and nonequilibrium characteristics, which cause diversity and complexity of boiling nucleation. In the present paper, an experimental investigation was conducted to investigate the nucleate boiling behavior on a very fine heating wire. Using zoom routine and CCD camera system, the dynamical process of nucleate boiling was visually observed and several modes of jet

H. Wang; X. F. Peng; B. X. Wang; D. J. Lee

2002-01-01

178

Flow Boiling and Condensation Experiment  

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...

179

Trends in Alkane Boiling Points  

NSDL National Science Digital Library

This activity is an investigation into the relationship between alkane length and boiling points. Students develop a mathematical model of this relationship and use it to make predictions and error analysis.

Woods, Paula

180

F-LE Boiling Water  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Below is a table showing the approximate boiling point of water at different elevations: Elevation (meters above sea level)Boiling Point (degrees Celsi...

181

Technical and QA plan: Boiling behavior during flow instability  

SciTech Connect

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 transient, 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 will proceed a flow excursion. These correlations rely on the steady state behavior of the coolant and are based on steady-state testing. There are two significant points which this project will try to identify. The first is when vapor first forms on the channel surface. This might be designated as the Nucleate Vapor Transition. (Steady state equivalent is ONB). The second is when the vapor formation rate is large enough to lead to flow instability and thermal excursion. This point might be designated as the Significant Vapor Transition. (Steady state equivalent is OSV). A correlation will be developed to relate established steady state relations with the behavior of transient systems.

Coutts, D.A.

1991-09-06

182

Forced convection boiling from a nonflush simulated electronic chip  

NASA Astrophysics Data System (ADS)

An experimental investigation has been undertaken to determine the effect of heated surface height on forced convective boiling. An inert fluorocarbon, FC-72 (3M Industrial Chemical Products Division) is circulated through a vertical rectangular channel at velocities of 1-4 m/s and subcoolings of 20 and 35 C. Results for five surface heights, as measured relative to the flow channel wall, were obtained. These were 0.127-mm recessed, 0.229-, 0.457-, and 0.635-mm protruded and flush with the flow channel wall. A reduction in critical heat flux (CHF) occurred at low velocities, while an increase occurred at higher velocities for the protruded cases. A reduction of CHF occurred at all velocities for the recessed condition. Additional results in the velocity range of 5-7 m/s are presented for the flush condition. This data shows that for velocities greater than 4 m/s, CHF becomes weakly dependent on the Weber number. Weak dependence on Weber number also implies a direct proportionality to velocity and a weak dependence on heated length.

Leland, J. E.; Chow, L. C.

1993-10-01

183

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

184

Hydrothermal activity Hydrothermal circulation at mid-ocean ridges  

E-print Network

#12;Hydrothermal activity #12;Hydrothermal circulation at mid-ocean ridges After sea water seeps metal-sulphide chimneys. #12;Hydrothermal circulation at mid-ocean ridges Black-smoker Schornsteine am;Distance (km) 10 105 50 2 4 6 8 Depth(km) Moho Transition zone Mush Gabbro Rift Valley · Slow ridges

Siebel, Wolfgang

185

Characteristics of Transient Boiling Heat Transfer  

SciTech Connect

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)

Liu, Wei; Monde, Masanori; Mitsutake, Y. [Saga University, 1 Honjo Saga City, Saga 840-8502 (Japan)

2002-07-01

186

Boiling on a straight pin fin  

SciTech Connect

In this study, Multimode boiling on a straight pin is theoretically investigated. Axial steady-state temperature distributions along the fin are numerically evaluated, as well as their linear stability characteristics. When film and transition boiling coexist on the fin surface, or only the transition boiling covers the entire fin, the operation remains stable only if the fin length is less than some critical value. When transition and nucleate boiling coexist on a fin, or the fin is in the three-mode boiling (film + transition + nucleate boiling), the entry of nucleate boiling at the fin tip stabilizes the boiling process. This study on base heat flow and fin efficiency with the stability criteria also suggests a new fin design methodology.

Lin, W.W.; Lee, D.J. [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Chemical Engineering] [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Chemical Engineering

1996-10-01

187

Cryogenic cooling system of HTS transformers by natural convection of subcooled liquid nitrogen  

E-print Network

Cryogenic cooling system of HTS transformers by natural convection of subcooled liquid nitrogen Ho-793, South Korea Abstract Heat transfer analysis on a newly proposed cryogenic cooling system is performed, and over-load operation. One of the key techniques to realize these advantages in practice is the cryogenic

Chang, Ho-Myung

188

Melting and resolidification of a subcooled metal powder particle subjected to nanosecond laser heating  

E-print Network

Melting and resolidification of a subcooled metal powder particle subjected to nanosecond laser were investigated. The Selective Laser Sintering (SLS) process for a pulsed laser can be simulated. Introduction Selective Laser Sintering (SLS) is an emerging technol- ogy that can build structurally

Zhang, Yuwen

189

Experimental study on sonic steam jet condensation in quiescent subcooled water  

Microsoft Academic Search

Condensation heat transfer of sonic steam jet in subcooled water was investigated experimentally over a wide range of steam mass flux and water temperature. Four different steam plume shapes were observed in present test conditions, and condensation regime map was given based on steam mass flux and water temperature. Maximum expansion ratio and dimensionless penetration length of the steam jet

Xin-Zhuang Wu; Jun-Jie Yan; Wen-Jun Li; Dong-Dong Pan; Dao-Tong Chong

2009-01-01

190

Reconstruction of local heat fluxes in pool boiling experiments along the entire boiling curve from high  

E-print Network

Reconstruction of local heat fluxes in pool boiling experiments along the entire boiling curve from conduction problem (IHCP) defined on an irregular three-dimensional (3D) domain in pool boiling experiments heating foil pressed to the bottom of the heater. The heat flux at the inaccessible boiling side

191

ON THE STABILITY OF BOILING HEAT TRANSFER  

Microsoft Academic Search

Boiling heat transfer in the nucleate region is reviewed. The ; transition film-boiling region is analyzed by considering the stability of a ; plane vortex sheet separating two inviscid fluids. Using the classical results ; of Helmholtz Kelvan and Rayleigh expressions have been derived that predict the ; maximum and minimum heat-transfer rates in the nucleate and the film-boiling ;

N. Zuber

1958-01-01

192

Geochemistry of the volcano-hydrothermal system of El Chichón Volcano, Chiapas, Mexico  

Microsoft Academic Search

The 1982 eruption of El Chichón volcano ejected more than 1?km3 of anhydrite-bearing trachyandesite pyroclastic material to form a new 1-km-wide and 300-m-deep crater and uncovered the\\u000a upper 500?m of an active volcano-hydrothermal system. Instead of the weak boiling-point temperature fumaroles of the former\\u000a lava dome, a vigorously boiling crater spring now discharges ?\\/?20?kg\\/s of Cl-rich (?15?000?mg\\/kg) and sulphur-poor (?\\/?200?mg\\/kg

Yuri Taran; Tobias P. Fischer; Boris Pokrovsky; Yuji Sano; Maria Aurora Armienta; Jose Luis Macias

1998-01-01

193

Boiling liquid engine cooling system  

Microsoft Academic Search

A boiling liquid cooling system is described for an engine, comprising: means defining in the engine a coolant jacket into which coolant is introduced in liquid state and from which coolant is discharged in gaseous state; a radiator into which gaseous coolant from the coolant jacket is introduced to be liquified; an electric pump for pumping the coolant thus liquified

N. Miura; Y. Hayashi

1987-01-01

194

"Sand Boil" on Bay Bridge  

USGS Multimedia Gallery

"Sand boil" or sand volcano measuring 2 m (6.6 ft) in length erupted in median of Interstate Highway 80 west of the Bay Bridge toll plaza when ground shaking transformed loose water-saturated deposit of subsurface sand into a sand-water slurry (liquefaction). Vented sand contains-marine shell f...

2009-01-26

195

Acoustically enhanced boiling heat transfer  

NASA Astrophysics Data System (ADS)

An acoustic field generated by a light-weight, low-power acoustic driver is shown to increase the critical heat flux during pool boiling by about 17%. It does this by facilitating the removal of vapor bubbles from the heated surface and suppressing the instability that leads to the transition to film boiling at the critical heat flux. Bubble removal is enhanced because the acoustic field induces capillary waves on the surface of a vapor bubble that interact with the bubble contact line on the heated surface causing the contact line to contract and detach the bubble from the surface. The acoustic field also produces a radiation pressure that helps to facilitate the bubble detachment process and also suppresses the transition to film boiling. The mechanisms associated with these interactions are explored using three different experimental setups with acoustic forcing: an air bubble on the underside of a horizontal surface, a single vapor bubble on the top side of a horizontal heated surface, and pool boiling from a horizontal heated surface. Measurements of the capillary waves induced on the bubbles, bubble motion, and heat transfer from the heated surface were performed to isolate and identify the dominant forces involved in these acoustically forced motions.

Douglas, Zachary; Boziuk, Thomas R.; Smith, Marc K.; Glezer, Ari

2012-05-01

196

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

SciTech Connect

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.

Ohmori, T.

1986-07-01

197

GEOCHEMISTRY OF HYDROTHERMAL DEPOSITS  

E-print Network

T. Mackenzie MichaelJ.Mottl #12;iv ABSTRACT Mineralogical composition,major, minor and rare earth elementchemistry,and uranium-seriesradionuclideswere determinedfor hydrothermaliron-rich depositsfrom five hydrothermal vent fields on the summit of Loihi Seamount,Hawai'i. The mineralogy and the major

Luther, Douglas S.

198

Computations of Boiling in Microgravity  

NASA Technical Reports Server (NTRS)

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.

Tryggvason, Gretar; Jacqmin, David

1999-01-01

199

The International Boiling Point Project  

NSDL National Science Digital Library

Between September 13 and December 10, 1999, the Center for Improved Engineering and Science Education (CIESE) at the Stevens Institute of Technology in Hoboken, New Jersey invites students and adults from all over the world to participate in The International Boiling Point Project. "The purpose of this project is to discover which factor in the experiment (room temperature, elevation, volume of water, or heating device) has the greatest influence on boiling point." Students, entire classes, or anyone else interested in participation must register beforehand via an online form. Data submitted online are posted at the site. The deadline for submitting data to be included in the final database is November 19, 1999. The project is an excellent forum for engaging students in the process of simple experimentation and data collection.

200

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park: IV Acid–sulfate waters  

Microsoft Academic Search

Many waters sampled in Yellowstone National Park, both high-temperature (30–94°C) and low-temperature (0–30°C), are acid–sulfate type with pH values of 1–5. Sulfuric acid is the dominant component, especially as pH values decrease below 3, and it forms from the oxidation of elemental S whose origin is H2S in hot gases derived from boiling of hydrothermal waters at depth. Four determinations

D. Kirk Nordstrom; R. Blaine McCleskey; James W. Ball

2009-01-01

201

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

Microsoft Academic Search

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

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

2009-01-01

202

Steam bubble condensation in sub-cooled water in case of co-current vertical pipe flow  

Microsoft Academic Search

The structure of a steam-water flow in a vertical pipe of 195.3mm inner diameter was studied using novel wire-mesh sensors for high-pressure\\/high-temperature operation (max 7MPa\\/286°C). Tests were carried out at pressures of 1 and 2MPa under nearly adiabatic conditions as well as with slightly sub-cooled water (6K at max). Steam was injected into sub-cooled water and condensed during the upwards

Dirk Lucas; Horst-Michael Prasser

2007-01-01

203

A phenomenological model of the thermal hydraulics of convective boiling during the quenching of hot rod bundles  

SciTech Connect

In this paper, a phenomenological model of the thermal hydraulics of convective boiling in the post-critical-heat-flux (post-CHF) regime is developed and discussed. The model was implemented in the TRAC-PF1/MOD2 computer code (an advanced best-estimate computer program written for the analysis of pressurized water reactor systems). The model was built around the determination of flow regimes downstream of the quench front. The regimes were determined from the flow-regime map suggested by Ishii and his coworkers. Heat transfer in the transition boiling region was formulated as a position-dependent model. The propagation of the CHF point was strongly dependent on the length of the transition boiling region. Wall-to-fluid film boiling heat transfer was considered to consist of two components: first, a wall-to-vapor convective heat-transfer portion and, second, a wall-to-liquid heat transfer representing near-wall effects. Each contribution was considered separately in each of the inverted annular flow (IAF) regimes. The interfacial heat transfer was also formulated as flow-regime dependent. The interfacial drag coefficient model upstream of the CHF point was considered to be similar to flow through a roughened pipe. A free-stream contribution was calculated using Ishii's bubbly flow model for either fully developed subcooled or saturated nucleate boiling. For the drag in the smooth IAF region, a simple smooth-tube correlation for the interfacial friction factor was used. The drag coefficient for the rough-wavy IAF was formulated in the same way as for the smooth IAF model except that the roughness parameter was assumed to be proportional to liquid droplet diameter entrained from the wavy interface. The drag coefficient in the highly dispersed flow regime considered the combined effects of the liquid droplets within the channel and a liquid film on wet unheated walls. 431 refs., 6 figs., 4 tabs.

Nelson, R.A.; Unal, C.

1991-01-01

204

Models and Stability Analysis of Boiling Water Reactors  

SciTech Connect

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.

John Dorning

2002-04-15

205

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

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

206

Analysis and measurement of thermal conductivity of polypropylene laminated paper impregnated with subcooled liquid nitrogen  

NASA Astrophysics Data System (ADS)

We measured the thermal conductivity of polypropylene laminated paper (PPLP) impregnated with subcooled liquid nitrogen. PPLP is widely used for the electrical insulation of high-Tc superconducting (HTS) power transmission cables. Although the thermal conductivity of PPLP is an important factor in the design of HTS cables, there has been very limited work on its measurement in subcooled liquid nitrogen. We prepared PPLP samples and symmetrically stacked them on both sides of a heater. The stacked samples were immersed in liquid nitrogen in an open cryostat. A cryocooler mounted on the cryostat was used to maintain the subcooled temperature of the liquid nitrogen. The thermal conductivity of the stacked PPLPs was measured by the steady state method at a bath temperature of 65-75 K and was found to be 0.23-0.26 W/m K, which is about five times that measured in a vacuum as presented in available literature. We also discuss possible mechanisms for boosting the thermal conductivity of PPLP by liquid nitrogen impregnation.

Furuse, Mitsuho; Fuchino, Shuichiro

2014-09-01

207

Stability analysis of NbTi-Ta-based high field conductor cooled by pool boiling below 4 K  

SciTech Connect

Stability analysis has been performed for cabled NbTi-Ta-based superconductors intended for the high field (12 T) toroidal field coils for a large scale tokamak device such as ETF. Ternary NbTi-Ta was selected as the superconductor because of its superior critical current density at high field as compared to the binary alloy NbTi. The operating temperature was chosen to be 2.5 K or below to optimize the performance of the superconductor. A cabled conductor was selected to minimize the pulsed field losses. The conductor is cooled by pool boiling in a subcooled (approx. 2.5 K, 0.25 atm) bath, or in a superfluid helium (He-II) bath (approx. 1.8 K, 0.02 atm). The analysis was based on numerically simulating the evolution of a normal zone in the conductor. Appropriate superconductor properties and heat transfer characteristics were utilized in the simulation.

Chen, W.Y.; Alcorn, J.S.; Hsu, Y.H.; Purcell, J.R.

1980-09-01

208

Pool boiling on nano-finned surfaces  

E-print Network

to the surface of the liquid pool. Thus, there is a constant pumping action which is the principle of operation of these “ virtual thermosyphons” [4]. The advantage of pool boiling over flow boiling systems is that no external pumping source is required... to the surface of the liquid pool. Thus, there is a constant pumping action which is the principle of operation of these “ virtual thermosyphons” [4]. The advantage of pool boiling over flow boiling systems is that no external pumping source is required...

Sriraman, Sharan Ram

2008-10-10

209

Pool boiling on nano-finned surfaces  

E-print Network

to the surface of the liquid pool. Thus, there is a constant pumping action which is the principle of operation of these ? virtual thermosyphons? [4]. The advantage of pool boiling over flow boiling systems is that no external pumping source is required... to the surface of the liquid pool. Thus, there is a constant pumping action which is the principle of operation of these ? virtual thermosyphons? [4]. The advantage of pool boiling over flow boiling systems is that no external pumping source is required...

Sriraman, Sharan Ram

2009-05-15

210

Nucleate pool-boiling heat transfer. I: review of parametric effects of boiling surface  

Microsoft Academic Search

The objective of this paper is to assess the state-of-the-art of heat transfer in nucleate pool-boiling. Therefore, the paper consists of two parts: part I reviews and examines the effects of major boiling surface parameters affecting nucleate-boiling heat transfer, and part II reviews and examines the existing prediction methods to calculate the nucleate pool-boiling heat transfer coefficient (HTC).A literature review

I. L. Pioro; W. Rohsenow; S. S. Doerffer

2004-01-01

211

Life at Hydrothermal Vents  

NSDL National Science Digital Library

The first Web site is a NOVA Online Adventure from PBS (1). Into the Abyss decribes the "pitch darkness, poison gas, heavy metals, extreme acidity, and enormous pressure" found at hydrothermal vents, and offers a look at bizarre and fascinating creatures found in this environment. The next Web site from Exploring Earth, an online earth sciences text book, contains video clips taken during research expeditions along the Juan de Fuca Ridge (2). Ocean AdVENTure, a ThinkQuest Web site, offers a comprehensive and well-designed introduction to hydothermal vents from research tools to fauna to unsolved mysteries and more (3). Visitors can choose their own scientific adVENTure to explore hydrothermal vents in this interactive feature from the University of Washington School of Oceonagraphy Exploraquarium (4). Dive and Discover is "an interactive distance learning Web site designed to immerse you in the excitement of discovery and exploration of the deep seafloor." This Web site (5) extends a virtual invitation to join scientists aboard research cruises to the depth of the Pacific and Indian Oceans, providing daily logs, video, and other features for each expedition. The next Web site from the University of California-Berkeley offer a closer look at the "strange tube-dwelling worm" phylum found only near hydrothermal vents (6). Creature Features, provided by the University of Delaware Graduate College of Marine Science, contains descriptions and video clips of tubeworms, vent crabs, Pompeii crabs, and ancient bacteria found at deep sea vents (7). The last Web site (8) is a transcript of a June 1997 PBS NewsHour interview with science writer William Broad. Broad discusses his book The Universe Below: Discovering the Secrets of the Deep Sea, and relates the exciting opportunities for scientific exploration of the sea floor made possible by the end of the Cold War.

Sohmer, Rachel.

2002-01-01

212

Hydrothermal Liquefaction of Biomass  

SciTech Connect

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

Elliott, Douglas C.

2010-12-10

213

Hydrothermal reactions under mechanochemical treating  

Microsoft Academic Search

The mechanochemical treating of solids containing some amount of free or chemically bound water in high-energetic activators enable the hydrothermal processes (as in autoclaves). Estimations of the optimal value of the water content were carried out. The data on the investigation of the mechanochemical reaction between calcium hydroxide and hydrated silica are presented as the experimental confirmation of the hydrothermal

N. V. Kosova; A. Kh. Khabibullin; V. V. Boldyrev

1997-01-01

214

Biocatalytic transformations of hydrothermal fluids  

NASA Astrophysics Data System (ADS)

The occurrence of copious animal populations at deep-sea vents indicates an effective microbial chemosynthetic biocatalysis of hydrothermal fluids on their emission into oxygenated ambient seawater. The large metabolic and physiological diversity of microbes found at these sites, including anaerobic and aerobic hyperthermophiles, reflects an even higher variety of biocatalytic or enzymatic reactions that greatly influence deep-sea hydrothermal geochemistry.

Jannasch, H. W.

215

21 CFR 872.6710 - Boiling water sterilizer.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Boiling water sterilizer. 872.6710 Section... Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered...

2011-04-01

216

21 CFR 872.6710 - Boiling water sterilizer.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2010-04-01 false Boiling water sterilizer. 872.6710 Section... Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered...

2010-04-01

217

Boiling nucleation during liquid flow in microchannels  

Microsoft Academic Search

The boiling of liquids in microchannels\\/microstructures is currently of great interest due to its very unusual phenomena and its many potential applications in a wide variety of advanced technologies. The thermodynamic aspects of phase transformations of liquids in microchannels was analyzed to further understand the boiling characteristics and to determine the conditions under which a portion of such liquids is

X. F. Peng; H. Y. Hu; B. X. Wang

1998-01-01

218

Pool Boiling Experiment Has Successful Flights  

NASA Technical Reports Server (NTRS)

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.

1996-01-01

219

Pool Boiling Experiment Has Five Successful Flights  

NASA Technical Reports Server (NTRS)

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.

Chiaramonte, Fran

1997-01-01

220

Nanofluid boiling: The effect of surface wettability  

Microsoft Academic Search

Nanofluid boiling has shown potential to increase boiling heat transfer, but the mechanisms responsible are poorly understood. One likely mechanism for nanofluid enhancement is an improvement in surface wettability. This study is targeted towards investigating whether or not nanofluids improve the critical heat flux (CHF) by altering the surface energy as has been observed for pure fluids. The surface of

Johnathan S. Coursey; Jungho Kim

2008-01-01

221

Onset of nucleate boiling in minichannels  

Microsoft Academic Search

Heat transfer characteristics during flow boiling in a minichannel were studied. For these investigations a thermographic measuring method was used. The axial distribution of the external wall temperature was measured, from which the internal wall temperatures and the local heat transfer coefficient are calculable. Detailed investigations were carried out in particular for the onset of nucleate boiling. The results of

Ingo Hapke; Hartwig Boye; Jürgen Schmidt

2000-01-01

222

Heat transfer in pool boiling under microgravity  

Microsoft Academic Search

Results are presented on parabolic-flight experiments performed on board ballistic rockets, designed to investigate the effect of system acceleration on the pool boiling curves for Freon 2. Measurements were carried out for a wide range of temperatures and pressures, and boiling curves were constructed for elevated gravity, earth gravity, and reduced gravity. It is demonstrated that, under reduced gravity conditions,

M. Zeii; J. Straub; B. Vogel

1990-01-01

223

Boiling of the Interface between Two Immiscible Liquids below the Bulk Boiling Temperatures of Both Components  

E-print Network

We consider the problem of boiling of the direct contact of two immiscible liquids. An intense vapour formation at such a direct contact is possible below the bulk boiling points of both components, meaning an effective decrease of the boiling temperature of the system. Although the phenomenon is known in science and widely employed in technology, the direct contact boiling process was thoroughly studied (both experimentally and theoretically) only for the case where one of liquids is becoming heated above its bulk boiling point. On the contrary, we address the case where both liquids remain below their bulk boiling points. In this paper we construct the theoretical description of the boiling process and discuss the actualisation of the case we consider for real systems.

Pimenova, Anastasiya V

2014-01-01

224

Boiling of the Interface between Two Immiscible Liquids below the Bulk Boiling Temperatures of Both Components  

E-print Network

We consider the problem of boiling of the direct contact of two immiscible liquids. An intense vapour formation at such a direct contact is possible below the bulk boiling points of both components, meaning an effective decrease of the boiling temperature of the system. Although the phenomenon is known in science and widely employed in technology, the direct contact boiling process was thoroughly studied (both experimentally and theoretically) only for the case where one of liquids is becoming heated above its bulk boiling point. On the contrary, we address the case where both liquids remain below their bulk boiling points. In this paper we construct the theoretical description of the boiling process and discuss the actualisation of the case we consider for real systems.

Anastasiya V. Pimenova; Denis S. Goldobin

2014-07-17

225

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)

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.

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

1998-01-01

226

Computations of Boiling in Microgravity  

NASA Technical Reports Server (NTRS)

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.

Tryggvason, G.; Jacqmin, Dave

2000-01-01

227

Acoustically Enhanced Boiling Heat Transfer  

E-print Network

An acoustic field is used to increase the critical heat flux (CHF) of a flat-boiling-heat-transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid-heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flatboiling surface for better study of an individual vapor bubble's reaction to the acoustic field. Work also includes application of the results from the single-bubble heater to a calibrated-copper heater used for quantifying the improvements in CHF.

Z. W. Douglas; M. K. Smith; A. Glezer

2008-01-07

228

LWR fuel rod post-subcooled blowdown scoping analysis. Technical report  

SciTech Connect

Thermal transients which occur during the post-subcooled blowdown regime of a postulated loss-of-coolant accident (LOCA) can cause significant changes in light water reactor (LWR) fuel rod material properties and geometry. The effects of these structural changes must be assessed to insure that a coolable geometry of the fuel system is maintained. An overall assessment of the fuel rod structural integrity has been made by considering the degraded structural properties of the fuel rod in conjunction with safe-shutdown earthquake (SSE) mechanical loadings and employing conventional stress analysis and fracture mechanics techniques.

Grubb, R.L.

1980-08-01

229

An Experimental Study on Thermal Energy Storage Based Reverse Cycle Defrosting Method Using Subcooling Energy of Refrigerant for Air Source Heat Pump: Characteristics of Thermal Energy Storage Operation  

Microsoft Academic Search

the introduction introduction of the the system of thermal energy storage torage (TES) based reverse cycle defrosting method using sub-cooling energy of refrigerant for air Source heat eat p pump (ASHP) is given firstly. And And then the the characteristic of TES TES using sub-cooling energy of refrigerant in in heating is experimentally researched. The results results show that that

Dong Jiankai; Qu Minglu; Jiang Yiqiang; Yao Yang; Deng Shiming; Wang Honglei

2011-01-01

230

CASE STUDIES OF FLUID TRANSIENTS IN SUBCOOLED Anton Bergant, Litostroj E.I. d.o.o., Slovenia, anton.bergant@litostroj-ei.si  

E-print Network

CASE STUDIES OF FLUID TRANSIENTS IN SUBCOOLED PIPE FLOW Anton Bergant, Litostroj E.I. d.s.tijsseling@tue.nl Alan E. Vardy, University of Dundee, United Kingdom, a.e.vardy@dundee.ac.uk Key words: subcooled pipe of the piping system and damage the system components. This paper presents authors' case studies of typical

Eindhoven, Technische Universiteit

231

Transient behavior of superheated water jets boiling  

NASA Astrophysics Data System (ADS)

Superheated water flowing out from high-pressure chamber through short cylindrical and slot channel has been studied experimentally. Relation of vaporization mechanisms in superheated liquid (boiling in single, not interacting centers, intense heterogeneous vaporization, and homogeneous fluctuating nucleation) and respective forms of superheated water jets has been determined. Temperature intervals with transient behavior of boiling have been determined. It is shown that at transient behavior of boiling the amplitude of pulsations of jet parameters increases, and in the spectra of pulsation power, the low-frequency component 1/ f appears.

Reshetnikov, A. V.; Busov, K. A.; Mazheiko, N. A.; Skokov, V. N.; Koverda, V. P.

2012-06-01

232

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

USGS Publications Warehouse

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.

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

1990-01-01

233

Sulfur speciation in natural hydrothermal waters, Iceland  

NASA Astrophysics Data System (ADS)

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 ?mol kg -1, respectively. Thiosulfate was detected in 49 samples of the 73 analyzed with concentrations in the range of <1-394 ?mol kg -1 (S-equivalents). Sulfite was detected in few samples with concentrations in the range of <1-3 ?mol 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 ?mol 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.

Kaasalainen, Hanna; Stefánsson, Andri

2011-05-01

234

Characteristics of nucleate pool boiling from porous metallic coatings  

Microsoft Academic Search

A study of pool boiling from a commercial porous metallic matrix surface is reported. The excellent steady boiling characteristics of this type of surface are confirmed; however, high wall superheats are required in most cases to initate boiling. The resultant boiling curve hysteresis does not appear to have been previously reported in the literature. This effect is indicated in recent

A. E. Bergles; M. C. Chyu

1982-01-01

235

Nucleate pool boiling enhancement by means of surfactant additives  

Microsoft Academic Search

While certain surfactant additives are well known to significantly enhance boiling heat transfer, the enhancement mechanism is still not so clear for the present. In order that more conclusive information of fundamental boiling phenomena in surfactant solutions can be collected, surfactant effects on interfacial properties at gas\\/liquid interface, nucleate boiling heat transfer, boiling incipience, and single vapor bubble growth dynamics

Wuu-Tsann Wu; Yu-Min Yang; Jer-Ru Maa

1998-01-01

236

Performance of the MAGCOOL-subcooler cryogenic system after SSC quadrupole quenches  

SciTech Connect

The subcooler assembly installed in the MAGCOOL magnet test area at Brookhaven National Laboratory has been used for testing SSC dipoles, quadrupoles and a spool piece since 1989. A detailed description of the system, its steady state capacity and the performance after quenches of a 50 mm SSC dipole were given. Subsequent studies on low current quenches of the SSC dipoles and quenches of the RHIC dipoles were also carried out. In this paper, the performance of the subcooler after quenches of the SSC quadrupole QCC404 is presented. Pressures, temperatures and flow rates in the magnet cooling loop after magnet quenches are given as a function of time. The cooling rates and total energy removed by cooling during quench recovery have been calculated for quench currents between 2000 and 7952 amperes. Because the inductance of the quadrupole is about one tenth that of a SSC dipole, the stored energy released is small and the impact on the system is mild. The cooling loop pressure never exceeds 12 atmospheres and the cryogenic system recovers in less than 15 minutes. As in all past studies, the peak pressure and temperature in the magnet cooling loop are linearly proportional to the energy released during a quench and excellent agreement between the total cooling provided and the magnetic stored energy is found.

Wu, K.C.

1993-06-01

237

Performance of the MAGCOOL-subcooler cryogenic system after SSC quadrupole quenches  

SciTech Connect

The subcooler assembly installed in the MAGCOOL magnet test area at Brookhaven National Laboratory has been used for testing SSC dipoles, quadrupoles and a spool piece since 1989. A detailed description of the system, its steady state capacity and the performance after quenches of a 50 mm SSC dipole were given. Subsequent studies on low current quenches of the SSC dipoles and quenches of the RHIC dipoles were also carried out. In this paper, the performance of the subcooler after quenches of the SSC quadrupole QCC404 is presented. Pressures, temperatures and flow rates in the magnet cooling loop after magnet quenches are given as a function of time. The cooling rates and total energy removed by cooling during quench recovery have been calculated for quench currents between 2000 and 7952 amperes. Because the inductance of the quadrupole is about one tenth that of a SSC dipole, the stored energy released is small and the impact on the system is mild. The cooling loop pressure never exceeds 12 atmospheres and the cryogenic system recovers in less than 15 minutes. As in all past studies, the peak pressure and temperature in the magnet cooling loop are linearly proportional to the energy released during a quench and excellent agreement between the total cooling provided and the magnetic stored energy is found.

Wu, K.C.

1993-01-01

238

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

USGS Publications Warehouse

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.

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, W. C.

2014-01-01

239

The plumbing of Old Faithful Geyser revealed by hydrothermal tremor  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

240

Nuclear fuel performance in boiling water reactors  

SciTech Connect

A major development program is described to improve the performance of Boiling Water Reactor fuel. This sustained program is described in four parts: 1) performance monitoring, 2) fuel design changes, 3) plant operating recommendations, and 4) advanced fuel programs.

Elkins, R.B.; Baily, W.E.; Proebstle, R.A.; Armijo, J.S.; Klepfer, H.H.

1981-08-01

241

Why Is NASA Boiling Fluids in Space?  

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...

242

Pool boiling heat transfer characteristics of nanofluids  

E-print Network

Nanofluids are engineered colloidal suspensions of nanoparticles in water, and exhibit a very significant enhancement (up to 200%) of the boiling Critical Heat Flux (CHF) at modest nanoparticle concentrations (50.1% by ...

Kim, Sung Joong, Ph. D. Massachusetts Institute of Technology

2007-01-01

243

Nucleate boiling bubble growth and departure  

E-print Network

The vapor bubble formation on the heating surface during pool boiling has been studied experimentally. Experiments were made at the atmospheric pressure 28 psi and 40 psi, using degassed distilled water and ethanol. The ...

Staniszewski, Bogumil E.

1959-01-01

244

A Mechanistic Study of Nucleate Boiling Heat Transfer Under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

245

Boiling of Water Droplets Containing Dissolved Salts  

Microsoft Academic Search

We conducted experiments on the effect of dissolving three different salts (sodium chloride, sodium sulphate and magnesium sulphate) in water droplets boiling on a hot stainless steel surface. Substrate temperatures were varied from 100^oC to 300^oC. We photographed droplets as they evaporated, and recorded their evaporation time. At surface temperatures that were too low to initiate nucleate boiling, all three

Qiang Cui; Sanjeev Chandra; Susan McCahan

2000-01-01

246

Numerical modeling of a nucleate boiling surface  

SciTech Connect

A computer program developed to analyze nucleate boiling over a heated surface is described. The model solves the three-dimensional transient conduction equation within the heater. The conduction solution is coupled with closure relationships to mimic the bubble dynamics and the associated heat transfer coefficients. Sample problems are run using a copper surface subject to partial nucleate boiling in saturated water at atmospheric pressure. The results are shown to be in good qualitative agreement with the pertinent experimental observations.

Pasamehmetoglu, K.O. (Los Alamos National Lab., NM (United States). Nuclear Technology and Engineering Division)

1994-06-01

247

Boiling heat transfer in a vertical microchannel: Local estimation during flow boiling with a non intrusive method  

E-print Network

Boiling heat transfer in a vertical microchannel: Local estimation during flow boiling with a non the results of experimental and numerical studies concerning boiling heat transfer inside vertical of boiling flows in microscale's geometry, it is vital to quantify these transfers. To achieve this goal

248

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

NASA Technical Reports Server (NTRS)

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

Herman, Cila

1999-01-01

249

Phenomenology of boiling: A coupled map lattice model.  

PubMed

A minimal model for boiling is proposed. With increasing temperature of a bottom plate, the model shows three successive phases; conduction, nucleate, and film boiling. In the nucleate regime the heat flux increases with the temperature of the bottom plate, while it decreases in the film boiling regime. In the boiling phase, the maximum Lyapunov exponent is positive, implying that the boiling phenomena are spatiotemporally chaotic. PMID:12779984

Yanagita, Tatsuo

1992-07-01

250

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

SciTech Connect

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.

Chow, J.S. (Boston Univ., MA (United States). Geology Dept.)

1993-03-01

251

Report on Pool Boiling Experiment Flown on STS-47 (PBE-IA), STS-57 (PBE-IB), and STS-60 (PBE-IC). Final report  

SciTech Connect

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. Transient measurements of the heater surface and fluid temperatures near the surface are made, noting in particular 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 acquisitions are completely automated and self-contained. A total of nine tests were conducted at three levels of heat flux and three levels of subcooling under three essentially identical circumstances in three space experiments designated as PBE-IA, -IB, -IC on the STS-47, -57, -60, respectively. Minor differences in lengths of various components of the experiments were programmed in the three flights. Two of the flights (STS-47, -60) took place with the same physical hardware, while the other (STS-57) used an identically fabricated hardware. The basic mechanisms of pool boiling are reviewed, with particular emphasis on the roles of buoyancy, and the experimental concepts and parameters used are given. The hardware and operating procedures followed are described in some detail. The experimental results for each of the nine runs in each of the space flights, along with those from several post-flight ground tests, are given in sufficient detail that the derived parameters and conclusions can be independently obtained, if desired. Sample images are provided for each run, following digitizing from the 16 mm film. The absence of buoyancy permitted the onset of boiling at low heat flux levels, with what is deemed as homogeneous nucleation taking place.

Merte, H. Jr.; Lee, H.S.; Keller, R.B.

1996-03-01

252

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

SciTech Connect

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)

Ong, Chin L.; Thome, John R. [Laboratory of Heat and Mass Transfer (LTCM), Ecole Polytechnique Federale de Lausanne (EPFL), ME G0 520 ME Station 9, Lausanne CH 1015 (Switzerland)

2009-04-15

253

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

SciTech Connect

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)

Daniels, Brian J.; Liburdy, James A.; Pence, Deborah V. [Mechanical Engineering, Oregon State University, Corvallis, OR 97330 (United States)

2011-01-15

254

Forced convection boiling from a non-flush simulated electric chip  

NASA Astrophysics Data System (ADS)

An experimental investigation is undertaken to determine the effect of heated-surface height on forced convecting boiling. An inert fluorocarbon is circulated through a vertical rectangular channel at velocities of 1 to 4 m/s and subcoolings of 20 and 35 C. Results for five surface heights, as measured relative to the flow channel wall, were obtained. These were 0.127 mm recessed, 0.229, 0.457, and 0.635 mm protruded and flush with the flow-channel wall. A reduction in critical heat flux (CHF) occurred at low velocities while an increase occurred at higher velocities for the protruded cases. A reduction of CHF occurred at all velocities for the recessed condition. Additional results in the velocity range of 5-7 m/s are presented for the flush condition. The data show that for velocities greater than 4 m/s, CHF becomes weakly dependent on the Weber number. The weak dependence on Weber number also implies a direct proportionality to velocity and a weak dependence on heated length.

Leland, J. E.; Chow, L. C.

1992-01-01

255

Silica Transport and Distribution in Saline, Immiscible Fluids: Application to Subseafloor Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

Quartz is a nearly ubiquitous gangue mineral in hydrothermal mineral deposits, most often constituting the bulk of hydrothermal mineralization. The dissolution, transport and precipitation of quartz is controlled by the solubility of silica; in particular, in hot hydrothermal fluids in contact with quartz, silica saturation can generally be assumed, as rates of dissolution and precipitation are generally much faster than fluid flow rates. The solubility of silica in aqueous fluids can be used to understand the evolution of hydrothermal systems by tracing the silica distribution in these systems through time. The solubility of quartz in an aqueous fluid is dependent upon the pressure, temperature and composition (PTX) of the fluid. Silica solubility in pure water as a function of pressure and temperature is well understood. However, natural fluids contain variable amounts of dissolved ionic species, thus it is necessary to include the effects of salinity on silica solubility to accurately predict quartz distribution in hydrothermal systems. In particular, addition of NaCl results in enhanced quartz solubility over a wide range of PT conditions. Furthermore, if phase separation occurs in saline fluids, silica is preferentially partitioned into the higher salinity brine phase; if vapor is removed from the system, the bulk salinity in the system evolves towards the brine end member, and overall silica solubility is enhanced. There is abundant evidence from natural fluid inclusions for fluid immiscibility in hydrothermal ore deposits. Additionally, recent hydrothermal models that include fluid phase equilibria effects predict that phase separation may be an important control on the distribution of dissolved components in seafloor hydrothermal systems. An empirical equation describing the solubility of silica in salt-bearing hydrothermal solutions over a wide range of PTX conditions has been incorporated into a multiphase fluid flow model for seafloor hydrothermal systems to predict the evolution of silica distribution in time and space in these systems. Preliminary runs illustrate a significant effect of salinity in the evolving and boiling system on silica solubility. The model predicts that silica solubility is progressively enhanced in the two-phase liquid-plus-vapor region as brine is concentrated by the preferential loss of vapor. The model also predicts that there is a narrow region of intense quartz deposition in the deep part of the upflow zone, where the fluid reenters the one-phase field. The model currently treats the wallrock as an infinite quartz reservoir, but future work will fully couple the quartz solubility and fluid flow models, to allow porosity adjustment and resultant permeability evolution by quartz dissolution and precipitation. This work was supported in part by the Institute for Critical Technology and Applied Sciences (ICTAS) at Virginia Tech

Steele-Macinnis, M.; Bodnar, R. J.; Lowell, R.; Rimstidt, J. D.

2009-05-01

256

Anomaly Geochemical Fields in Siberian Hydrothermal Gold Deposits  

NASA Astrophysics Data System (ADS)

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.

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

2014-08-01

257

Hydrothermal pretreatment of coal  

SciTech Connect

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.

Ross, D.S.

1989-12-21

258

Hydrothermal synthesis of ammonium illite  

USGS Publications Warehouse

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.

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

1998-01-01

259

Exploration strategies for hydrothermal deposits.  

PubMed

With unlimited money the most certain strategy for finding most hydrothermal metal deposits would be by drilling to 5000 m at 50 m spacing. However, the cost would far outweigh the benefit of the discoveries. Geological knowledge and exploration techniques may be used to obtain the greatest benefit for minimum cost, and to concentrate human and material resources in the most economic way in areas with the highest probability of discovery. This paper reviews the economic theory of exploration based on expected value, and the application of geological concepts and exploration techniques to exploration for hydrothermal deposits. Exploration techniques for hydrothermal-systems on Mars would include geochemistry and particularly passive geophysical methods. PMID:9243019

Horn, R A

1996-01-01

260

On the evolution of convection in magmatic-hydrothermal systems  

NASA Astrophysics Data System (ADS)

Convective fluid circulation in continental magmatic-hydrothermal systems plays a fundamental role for the formation of ore deposits and geothermal systems. Two competing processes drive convection in continental magmatic-hydrothermal systems: gradients in temperature, which decrease the density of the fluid, and gradients in salinity, which increase the density of the fluid. While heat diffuses more rapidly than salt, salt is advected faster than heat and as a result, double-diffusive and double-advective instabilities can form which may lead to chaotic convection. Continental magmatic-hydrothermal systems can cover a wide PTX range (0 to 800 C, 0 to 500 MPa, and 0 to 1 XNaCl). Under these condition, the presence of salt in the fluid increases the PT regime during which boiling and phase-separation into a highly compressible, low-salinity vapour phase and a slightly compressible, high-salinity brine phase take place. This process of phase-separation is thought to have a profound effect on the evolution of convection cells in continental magmatic-hydrothermal systems but has not yet been studied. In order to understand the effect of double-advective, double-diffusive convection and phase separation in continental magmatic-hydrothermal, we have combined a higher order finite element-finite volume algorithm and a new equation of state for the system H2O-NaCl which provides a realistic thermodynamic representation of the fluid properties including the wide PTX range of liquid + vapour coexistence for the highly saline fluids. This allows us to realistically model multi-phase fluid flow, energy and component transport in continental magmatic-hydrothermal systems, including fluid and rock properties that vary over many orders of magnitude and the geometric complexities of such systems. We have conducted several simulations of a continental magmatic-hydrothermal systems in which a hot, saline magmatic fluid exsolves from a crystallizing magma and is injected into the surrounding rock. In the simulations, we have successively varied the following input parameters: Depth of intrusion, rate of magmatic fluid production, temperature of magmatic fluid, salinity of magmatic fluid, and permeability structure. First results show that the combination of the rate at which magmatic fluid is produced and the permeability structure of the system have the most profound effect on the evolution of convection in continental magmatic-hydrothermal systems. High permeabilities in combination with relatively low fluid production rates (long lived fluid production) lead to an effective cooling mechanism during which temperatures rarely exceed 150 C. Only if the permeabilities are sufficiently low and the fluid production rate is sufficiently fast (short lived fluid production), convection cells can form that produce temperatures where phase separation can take place and ore deposits can form.

Geiger, S.; Driesner, T.; Heinrich, C.; Matthai, S. K.

2003-04-01

261

Enhancements of Nucleate Boiling Under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

262

Experimental study on multi-mode methanol flow boiling  

SciTech Connect

Flow boiling of methanol over a nonuniform, indirect conduction heating surface is investigated experimentally. An axial (discrete) heat flux distribution corresponding to a neutral stability region where nucleate and film boiling can coexist steadily is identified. Below such a heat flux distribution, nucleate boiling mode is more stable. Above this distribution, film boiling mode becomes more stable. An equal-area criterion based on difference between bottom heat flux and surface boiling heat flux and the surface temperature data is employed for interpreting the experimental data, and reasonable agreement is obtained. The differences between average and real transition boiling curves are discussed as well.

Lin, W.W.; Lee, D.J. [National Taiwan Univ., Taipei (Taiwan, Province of China). Dept. of Chemical Engineering

1996-12-31

263

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

USGS Publications Warehouse

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.

Bargar, Keith E.; Beeson, Melvin H.

1985-01-01

264

Boiling as Household Water Treatment in Cambodia: A Longitudinal Study of Boiling Practice and Microbiological Effectiveness  

PubMed Central

This paper focuses on the consistency of use and microbiological effectiveness of boiling as it is practiced in one study site in peri-urban Cambodia. We followed 60 randomly selected households in Kandal Province over 6 months to collect longitudinal data on water boiling practices and effectiveness in reducing Escherichia coli in household drinking water. Despite > 90% of households reporting that they used boiling as a means of drinking water treatment, an average of only 31% of households had boiled water on hand at follow-up visits, suggesting that actual use may be lower than self-reported use. We collected 369 matched untreated and boiled water samples. Mean reduction of E. coli was 98.5%; 162 samples (44%) of boiled samples were free of E. coli (< 1 colony-forming unit [cfu]/100 mL), and 270 samples (73%) had < 10 cfu/100 mL. Storing boiled water in a covered container was associated with safer product water than storage in an uncovered container. PMID:22826487

Brown, Joseph; Sobsey, Mark D.

2012-01-01

265

Boiling on Microconfigured Composite Surfaces Enhanced  

NASA Technical Reports Server (NTRS)

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.

Chao, David F.

2000-01-01

266

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

ERIC Educational Resources Information Center

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)

Goodwin, Alan; Orlik, Yuri

2000-01-01

267

Transition boiling heat transfer from a horizontal surface  

E-print Network

An experiment, utilising a condensing fluid as the heat source, was performed to determine the heat flux vs. temperature difference curve for transition pool boiling from a horisontal surface. The boiling cure was determined ...

Berenson Paul Jerome

1960-01-01

268

The role of surface conditions in nucleate boiling  

E-print Network

Nucleation from a single cavity has been stuied indicating that cavity gemtry is aportant in two ways. The mouth diameter determines the superheat nmeded to initiate boiling and its shape determines its stability one boiling ...

Griffith, P.

1958-01-01

269

21 CFR 872.6710 - Boiling water sterilizer.  

Code of Federal Regulations, 2012 CFR

A boiling water sterilizer is an AC-powered device that consists of a container for boiling water. The device is intended to sterilize dental and surgical instruments by submersion in the boiling water in the container. (b) Classification. Class I (general controls). [55 FR 48439,...

2012-04-01

270

Fundamental issues related to flow boiling in minichannels and microchannels  

Microsoft Academic Search

Flow boiling in small hydraulic diameter channels is becoming increasingly important in many diverse applications. The previous studies addressing the effects of the channel size on the flow patterns, and heat transfer and pressure drop performance are reviewed in the present paper. The fundamental questions related to the presence of nucleate boiling and characteristics of flow boiling in microchannels and

Satish G. Kandlikar

2002-01-01

271

Boiling of nuclear liquid in the micro-canonical ensemble  

E-print Network

Boiling of nuclear liquid in the micro-canonical ensemble K. Miyazaki E-mail: miyazakiro@rio.odn.ne.jp Abstract New calculus of the liquid-gas phase transition is developed for the boiling of nuclear liquid-dependence of the nuclear symmetry energy and the critical temperature of 1 #12;Boiling of nuclear liquid in the micro

272

Boiling in microchannels: a review of experiment and theory  

Microsoft Academic Search

A summary of recent research on boiling in microchannels is presented. The review addresses the topics of macroscale versus microscale heat transfer, two-phase flow regimes, flow boiling heat transfer results for microchannels, heat transfer mechanisms in microchannels and flow boiling models for microchannels. In microchannels, the most dominant flow regime appears to be the elongated bubble mode that can persist

John R. Thome

2004-01-01

273

Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces  

E-print Network

Boiling heat transfer on superhydrophilic, superhydrophobic, and superbiphilic surfaces Amy Rachel Enhanced heat transfer Pool boiling Nucleation a b s t r a c t With recent advances in micro characterize pool boiling on surfaces with wettabilities varied from superhydrophobic to superhydrophilic

Attinger, Daniel

274

Nucleation characteristics and stability considerations during flow boiling in microchannels  

E-print Network

Nucleation characteristics and stability considerations during flow boiling in microchannels Satish; received in revised form 25 September 2005; accepted 3 October 2005 Abstract Flow boiling in microchannels in the flow boiling stability. To understand the role of local conditions on nucleation, the available

Kandlikar, Satish

275

ADVANCED POWER PLANT MODELING WITH APPLICATIONS TO THE ADVANCED BOILING  

E-print Network

ADVANCED POWER PLANT MODELING WITH APPLICATIONS TO THE ADVANCED BOILING WATER REACTOR AND THE HEAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Advanced Boiling Water Reactor - General Description . . . . . . . . . . . 3 2.1 Modifications-Dimensional Continuity Wave Equation for Boiling Mixtures . . 10 3.2.1 Derivation of Equation

Mitchell, John E.

276

EXPERIMENTAL INVESTIGATION OF BOILING HEAT CONVECTION IN A FRACTURE  

E-print Network

EXPERIMENTAL INVESTIGATION OF BOILING HEAT CONVECTION IN A FRACTURE A REPORT SUBMITTED between heat conduction and heat convection with boiling flow in a rock fracture. An experimental investigation attemped to analyze and quantify this coupling, which can be called a boiling convection

Stanford University

277

EFFECT OF SURFACE CHARACTERISTICS ON FLOW BOILING HEAT TRANSFER  

E-print Network

ABSTRACT It is well known that the surface structure affects the pool boiling heat transfer from a heater that the surface condition of the boiling surface affects the pool boiling heat transfer. Surface conditions and the overall heat flux. Enhancement techniques such as sintering and specially fabricated surface geometries

Kandlikar, Satish

278

Experimental study of surfactant effects on pool boiling heat transfer  

Microsoft Academic Search

In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is

Ying Liang Tzan; Yu Min Yang

1990-01-01

279

Boiling of Water Droplets Containing Dissolved Salts  

NASA Astrophysics Data System (ADS)

We conducted experiments on the effect of dissolving three different salts (sodium chloride, sodium sulphate and magnesium sulphate) in water droplets boiling on a hot stainless steel surface. Substrate temperatures were varied from 100^oC to 300^oC. We photographed droplets as they evaporated, and recorded their evaporation time. At surface temperatures that were too low to initiate nucleate boiling, all three salts were found to reduce the evaporation rate since they lower the vapor pressure of water. In the nucleate boiling regime, sodium sulphate and magnesium sulphate enhanced heat transfer because they prevented coalescence of vapor bubbles and produced foaming in the droplet, significantly reducing droplet lifetime. The ability of salts to prevent coalescence is linked to their ionic strength: electric charge accumulated on the surfaces of bubbles produces a repulsive force, preventing them from approaching each other. Sodium chloride, which has a low ionic strength, had little effect on droplet evaporation. Low concentrations (<0.3 mol/liter) of magnesium sulphate enhanced droplet boiling by promoting foaming. However high concentrations (>0.3 mol/liter) reduce droplet evaporation rates by increasing the vapour pressure of water.

Cui, Qiang; Chandra, Sanjeev; McCahan, Susan

2000-11-01

280

A new microstructure for pool boiling  

NASA Astrophysics Data System (ADS)

Combining electrocoating and etching processes, we have developed a new type of microstructure for nucleate boiling. The basic elements of the structure are cylindrically shaped; their density ranges up to 10 7 cm -2. To test the efficiency of the structure, the outer surface of a tube has been provided with such a structure and used in pool boiling experiments with the refrigerant R141b at atmospheric pressure. The results obtained show the heat flux to remain independent of the wall superheat in the fully developed boiling region. The behavior is novel. It is most probably associated with the density of active bubble nucleation sites. Activated at a certain wall superheat, the density of the sites generating bubbles remains apparently unaffected by raising the heat flux. Given that these preliminary results should be confirmed by further experiments, the microstructure developed will be suitable for nucleate boiling in general, but for keeping the heating surface largely isothermal, despite the variation of the heat flux, in particular.

Mitrovic, J.; Hartmann, F.

2004-03-01

281

Classic and Hard-Boiled Detective Fiction.  

ERIC Educational Resources Information Center

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…

Reilly, John M.

282

Pool boiling heat transfer to electrolyte solutions  

Microsoft Academic Search

Pool boiling heat transfer coefficients were measured for solutions of salts with positive solubility in water. The effect of the dissolved salts on nucleation site density, bubble departure diameter and bubble frequency was also investigated. The results show that at low heat fluxes heat transfer coefficients can be considerably lower than corresponding values for distilled water. At high heat fluxes

M. Jamialahmadi; A. Helalizadeh; H. Müller-Steinhagen

2004-01-01

283

A HYDRODYNAMIC MODEL FOR NUCLEATE POOL BOILING  

Microsoft Academic Search

A hydrodynamic model of stagnation flow is proposed for saturated ; nucleate boiling over a flat surface, Using analytical results from ; axisymmetrical stagnation flow, a relation between the heat-transfer coefficient ; and the thermal boundary-layer thickness induced by rising bubbles is obtained, ; and agreement with measured results in the low heat-flux region is indicated. ; The predicted heat-transfer

C Tien

1962-01-01

284

Mechanism of nucleate pool boiling heat transfer to sodium and the criterion for stable boiling  

E-print Network

A comparison between liquid metals and other common fluids, like water, is made as regards to the various stages of nucleate pool boiling. It is suggested that for liquid metals the stage of building the thermal layer plays ...

Shai, Isaac

1967-01-01

285

Transition from film boiling to nucleate boiling in forced convection vertical flow  

E-print Network

The mechanism of collapse of forced cnnvection annular vertical flow film boiling, with liquid core, is investigated using liquid nitrogen at low pressures. The report includes the effect of heat flux from the buss bar. ...

Iloeje, Onwuamaeze C.

1972-01-01

286

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

NASA Astrophysics Data System (ADS)

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.

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

2008-09-01

287

Boiling and acidification in epithermal systems: numerical modeling of transport and deposition of base, precious, and volatile metals  

SciTech Connect

Boiling and acidification of hydrothermal waters are important processes that lead to mineral precipitation in geothermal systems. In this study, numerical models of boiling and acidification are applied to a chemical system that contains base, precious and volatile metals. The numerical model incorporates simple newly-developed methods to account for heat balance and for the non-ideal behavior of gaseous H/sub 2/O, CO/sub 2/, CH/sub 4/, and H/sub 2/. Also, the stoichiometry and stability of arsenic and antimony thiosulfides at elevated temperature are evaluated, and included in an internally consistent set of thermodynamic data for arsenic and antimony aqueous species, minerals and gases. Equations derived from a quadratic virial equation in pressure are fitted to published P-V-T and solubility data to yield values of fugacity coefficients and enthalpies for several pure and mixed gases. The virial equation treatment and thermodynamic data for arsenic and antimony is used with existing software to simulate boiling and acidification of a Broadlands-type geothermal water that contains base, precious and volatile metals. The results indicate that the boiling leads to the precipitation of base metals, electrum and sulfosalts, and that acidification precipitates gold rich electrum or pure gold, along with sulfosalts and enargite at low temperatures. Below 100 C, acidification precipitates orpiment and stibnite. Upon boiling, mercury fractionates into the gas phase, but arsenic and antimony stay in the aqueous phase. In cooling of a dry gas phase, antimony stays in the gas down to 220 C where stibnite sublimates, and arsenic stays to 130 C where regular sublimates. Gas condensation below 100 C results in the precipitation of cinnabar.

Spycher, N.F.

1987-01-01

288

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

NASA Astrophysics Data System (ADS)

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.

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

289

SHF : "Ecoulements diphasiques", Grenoble, 8-9 septembre 2008-V. Nikolayev et al.-Physical modelling of the boiling crisis... PHYSICAL MODELLING OF THE BOILING CRISIS: THEORY  

E-print Network

.-Physical modelling of the boiling crisis... PHYSICAL MODELLING OF THE BOILING CRISIS: THEORY AND EXPERIMENT Mod.chatain@cea.fr In this presentation we describe a physical approach to the boiling crisis ("departure from nucleate boiling"). This approach is based on the hypothesis that the boiling crisis is triggered by spreading of individual vapor

Nikolayev, Vadim S.

290

Boron isotope systematics of hydrothermal fluids from submarine hydrothermal systems  

NASA Astrophysics Data System (ADS)

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 ?11B value (0.53 mM, 29.8‰), while dacite-hosted PACMANUS and the Suiyo Seamount showed high boron contents and low ?11B 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 ?11B 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 ?11B 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.

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

2013-12-01

291

Phreatic and Hydrothermal Explosions: A Laboratory Approach  

NASA Astrophysics Data System (ADS)

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.

Scheu, B.; Dingwell, D. B.

2010-12-01

292

A two-phase model for subcooled and superheated liquid jets  

SciTech Connect

This paper describes a two-phase jet model for predicting the liquid rainout (capture) and composition of subcooled and superheated HF/additive pressurized liquid releases. The parent droplets of the release mixture constitute the fist phase. The second phase can in general be a vapor-liquid fog. The drops are not in equilibrium with the fog phase with which they exchange mass and energy. The fog at any location is assumed to be in local equilibrium. Correlations are developed for predicting the initial drop size for hydrodynamic breakup of jets. Applications are discussed in this paper for HF/additive mixtures. The fog phase calculations account for HF oligomerization and HF-water complex formation in the vapor phase and equilibrium between the liquid and vapor in the fog. The model incorporates jet trajectory calculations and hence can predict the amount of liquid rained out (liquid capture) and the capture distance. The HF captures predicted by the model for various release conditions are in agreement with small and large scale release experiments.

Muralidhar, R.; Jersey, G.R.; Krambeck, F.J. [Mobil Research and Development Corp., Paulsboro, NJ (United States); Sundaresan, S. [Princeton Univ., NJ (United States). Dept. of Chemical Engineering

1995-12-31

293

Thermohydrodynamics of boiling in a van der Waals fluid.  

PubMed

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

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

2012-02-01

294

Numerical Simulations of Bubble Dynamics and Heat Transfer in Pool Boiling---Including the Effects of Conjugate Conduction, Level of Gravity, and Noncondensable Gas Dissolved in the Liquid  

NASA Astrophysics Data System (ADS)

Due to the complex nature of the subprocesses involved in nucleate boiling, it has not been possible to develop comprehensive models or correlations despite decades of accumulated data and analysis. Complications such as the presence of dissolved gas in the liquid further confound attempts at modeling nucleate boiling. Moreover, existing empirical correlations may not be suitable for new applications, especially with regards to varying gravity level. More recently, numerical simulations of the boiling process have proven to be capable of reliably predicting bubble dynamics and associated heat transfer by showing excellent agreement with experimental data. However, most simulations decouple the solid substrate by assuming constant wall temperature. In the present study complete numerical simulations of the boiling process are performed---including conjugate transient conduction in the solid substrate and the effects of dissolved gas in the liquid at different levels of gravity. Finite difference schemes are used to discretize the governing equations in the liquid, vapor, and solid phases. The interface between liquid and vapor phases is tracked by a level set method. An iterative procedure is used at the interface between the solid and fluid phases. Near the three-phase contact line, temperatures in the solid are observed to fluctuate significantly over short periods. The results show good agreement with the data available in the literature. The results also show that waiting and growth periods can be related directly to wall superheat. The functional relationship between waiting period and wall superheat is found to agree well with empirical correlations reported in the literature. For the case of a single bubble in subcooled nucleate boiling, the presence of dissolved gas in the liquid is found to cause noncondensables to accumulate at the top of the bubble where most condensation occurs. This results in reduced local saturation temperature and condensation rates. The numerical predictions show reasonable agreement with the results from experiments performed at microgravity. For nucleate boiling at microgravity the simulations predict a drastic change in vapor removal pattern when compared to Earth normal gravity. The predictions match well with experimental results. However, simulated heat transfer rates were significantly under-predicted.

Aktinol, Eduardo

295

Enhanced Droplet Control by Transition Boiling  

PubMed Central

A droplet of water on a heated surface can levitate over a film of gas produced by its own evaporation in the Leidenfrost effect. When the surface is prepared with ratchet-like saw-teeth topography, these droplets can self-propel and can even climb uphill. However, the extent to which the droplets can be controlled is limited by the physics of the Leidenfrost effect. Here, we show that transition boiling can be induced even at very high surface temperatures and provide additional control over the droplets. Ratchets with acute protrusions enable droplets to climb steeper inclines while ratchets with sub-structures enable their direction of motion to be controlled by varying the temperature of the surface. The droplets' departure from the Leidenfrost regime is assessed by analysing the sound produced by their boiling. We anticipate these techniques will enable the development of more sophisticated methods for controlling small droplets and heat transfer. PMID:23056912

Grounds, Alex; Still, Richard; Takashina, Kei

2012-01-01

296

Unorthodox bubbles when boiling in cold water  

NASA Astrophysics Data System (ADS)

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.

Parker, Scott; Granick, Steve

2014-01-01

297

Unorthodox bubbles when boiling in cold water.  

PubMed

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

Parker, Scott; Granick, Steve

2014-01-01

298

Self-propelled film-boiling liquids  

E-print Network

We report that liquids perform self-propelled motion when they are placed in contact with hot surfaces with asymmetric (ratchet-like) topology. The pumping effect is observed when the liquid is in the film-boiling regime, for many liquids and over a wide temperature range. We propose that liquid motion is driven by a viscous force exerted by vapor flow between the solid and the liquid.

H. Linke; B. J. Aleman; L. D. Melling; M. J. Taormina; M. J. Francis; C. C. Dow-Hygelund; V. Narayanan; R. P. Taylor; A. Stout

2005-12-27

299

Vapliq hydrothermal systems, and the vertical permeability of Los Azufres, Mexico, geothermal reservoir  

SciTech Connect

We identify a new category of natural hydrothermal systems intermediate between liquid- and vapor-dominated. This category is characterized by a “vapliq” vertical pressure profile, which is nearly vaporstatic in the shallower portion of the system, and nearly boiling-point-for-depth at depth. The prototype of these systems is the geothermal field of Los Azufres, Mexico. To explore the thermohydrological conditions conducent to this type of system, we propose a 1-D vertical scenario based on generally accepted conceptual models of liquid- and vapor-dominated geothermal reservoirs. We use the corresponding mass and thermal energy transport equations to establish that a necessary condition for the existence of 2-phase hydrothermal systems is that the absolute value of the vertical thermal flux must exceed Q{sub min}, a parameter that depends only on the values of the pressure and of the thermal conductivity at the boiling point of the system. The values of Q{sub min} are typically 1-4 times the average terrestrial flux. We also find that geothermal systems in which convective heat transport is accomplished by the well-known heat-pipe mechanism can exist only if the corresponding heat flux exceeds Q{sub min} and the permeability at the boiling point of the system is smaller than k{sub Bmax}, a parameter that depends only on the values of the pressure and of the thermal conductivity at the boiling point. Typical values of k{sub Bmax} are 1-3 {times} 10{sup -18} m{sup 2}, suggesting a reason for the fact that all vapor-dominated systems are associated with very-low matrix permeability formations. Applying these insights, and the mass and heat transport equations to Los Azufres, we conclude that a contrast of 1-3 orders of magnitude exists between the vertical permeability at the boiling point and that corresponding to the vapor-dominated portion of the system. We propose that similar permeability contrasts may be responsible for the characteristic composite pressure observed in other vapliq systems.

Iglesias, Eduardo R.; Arellano, Victor M.

1988-01-01

300

POOL BOILING OF HIGH-FREQUENCY CONDUCTORS  

SciTech Connect

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.

Wright, S. E. (Spencer E.); Konecni, S. (Snezana); Ammerman, C. N. (Curtt N.); Sims, J. R. (James R.)

2001-01-01

301

Flow boiling test of GDP replacement coolants  

SciTech Connect

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.

Park, S.H. [comp.

1995-08-01

302

Boiling radial flow in fractures of varying wall porosity  

SciTech Connect

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.

Barnitt, Robb Allan

2000-06-01

303

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

SciTech Connect

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)

Haas, C.; Miassoedov, A.; Schulenberg, T.; Wetzel, T. [Karlsruhe Inst. of Technology KIT, Inst. for Nuclear and Energy Technologies, Hermann-von-Helmholtzplatz 1, 76344 Eggenstein-Leopoldshafen (Germany)

2012-07-01

304

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

NASA Technical Reports Server (NTRS)

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.

Kassemi, Mohammad; Hylton, Sonya; Kartizova, Olga

2013-01-01

305

Boiling at the boundary of two immiscible liquids below the bulk boiling temperature of each component  

NASA Astrophysics Data System (ADS)

The problem of vapor formation in the system of two immiscible liquids is considered at the temperatures that are lower than the bulk boiling temperature of each component and higher than the temperature at which the sum of the saturated vapor pressures of the components is equal to atmospheric pressure. In this situation, boiling occurs at the surface of direct contact between the two components. The kinetics of the vapor layer at the contact boundary is theoretically described, and a solution is obtained for the idealized case where the properties of the two liquids are close to each other. The relation between the solution for the vapor layer kinetics and the integral boiling characteristics of the system is considered, and the problem of cooling the system in the absence of a heat inflow is solved.

Pimenova, A. V.; Goldobin, D. S.

2014-07-01

306

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

USGS Publications Warehouse

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

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

1991-01-01

307

D0 Silicon Upgrade: Vapor Pressure Thermometry System Near LN2 Subcooler  

SciTech Connect

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.

Kuwazaki, Andrew; /Fermilab

1996-07-01

308

Formation of transparent aluminum hydroxide film with mesoscopic surface roughness by hydrothermal treatment of incompletely-nitrided sputtered aluminum film  

NASA Astrophysics Data System (ADS)

Incompletely-nitrided Al films (Al-N film) are deposited on the glass substrate by rf sputtering with a metallic Al target and using Ar and N2 gas mixture. With increasing film thickness up to 300nm, the surface roughness increases. And the roughness is easily controlled. The size and the number density of surface protuberance are suitable to control diffusive optical properties in the visible and near infrared regions. The films become transparent with retained roughness by boiling in ultra pure water at 368K under atmospheric pressure. The films have been transformed from composite of Al and AlN to aluminum hydroxide (Boehmite). Total transmittance of the boiled specimens exceeded that of the glass substrate itself. These facts suggest that hydrothermally-treated Al-N films with the mesoscopic surface roughness have high potential to reduce the optical loss by reflection.

Hori, Toshiyuki; Qiu, Zhiyong; Ishiguro, Takashi

2010-06-01

309

Magmatic intrusions and hydrothermal systems  

NASA Astrophysics Data System (ADS)

This dissertation investigates the possible role of hydrothermally driven ground-water outflow in the formation of fluvial valleys on Mars. Although these landforms have often been cited as evidence for a past warmer climate and denser atmosphere, recent theoretical modeling precludes such climatic conditions on early Mars when most fluvial valleys formed. Because fluvial valleys continued to form throughout Mars' geological history and the most Earth-like stream valleys on Mars formed well after the decline of the early putative Earth-like climate, it may be unnecessary to invoke drastically different climatic conditions for the formation of the earliest stream valleys. The morphology of most Martian fluvial valleys indicates formation by ground-water sapping which is consistent with a subsurface origin. Additionally, many Martian fluvial valleys formed on volcanoes, impact craters, near fractures, or adjacent to terrains interpreted as igneous intrusions; all are possible locales of vigorous, geologically long-lived hydrothermal circulation. Comparison of Martian valley morphology to similar features on Earth constrains valley genesis scenarios. Volumes of measured Martian fluvial valleys range from 1010 to 1013 m3. Based on terrestrial analogs, total water volumes required to erode these valleys range from approximately 1010 to 1015 m3. The clustered distribution of Martian valleys within a given terrain type, the sapping dominated morphology, and the general lack of associated runoff valleys all indicate the importance of localized ground-water outflow in the formation of these fluvial systems. An analytic model of a conductively cooling cylindrical intrusion is coupled with the U.S. Geological Survey's numerical ground-water computer code SUTRA to evaluate the magnitude of ground-water outflow expected from magmatically-driven hydrothermal systems on Mars. Results indicate that magmatic intrusions of several 102 km3 or larger can provide sufficient ground-water outflow over periods (several 105 years) required to form Martian fluvial valleys. Therefore, a vastly different climate on early Mars may not be necessary to explain the formation of the observed valleys. Martian hydrothermal systems would have also produced long-lived sources of near-surface water; these localized regions may have provided oases for any microbial life that may have evolved on the planet.

Gulick, Virginia Claire

1993-01-01

310

Hydrothermal vents and the origin of life  

Microsoft Academic Search

Submarine hydrothermal vents are geochemically reactive habitats that harbour rich microbial communities. There are striking parallels between the chemistry of the H2–CO2 redox couple that is present in hydrothermal systems and the core energy metabolic reactions of some modern prokaryotic autotrophs. The biochemistry of these autotrophs might, in turn, harbour clues about the kinds of reactions that initiated the chemistry

John Baross; Deborah Kelley; Michael J. Russell; William Martin

2008-01-01

311

Whole Algae Hydrothermal Liquefaction Technology Pathway  

SciTech Connect

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.

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

2013-03-01

312

Hydrothermal Scheduling Using Benders Decomposition: Accelerating Techniques  

Microsoft Academic Search

A new decomposition method is presented that includes the network through ac modeling within the hydrothermal scheduling optimization process including the losses. In short-term hydrothermal scheduling, the transmission network is typically modeled with dc power flow techniques. Such modeling, however, can lead to impractical solutions when it is verified with ac power flow. Another proposal considers in thermal systems the

Wilfredo S. Sifuentes; Alberto Vargas

2007-01-01

313

Dispatch from the Deep: Hydrothermal Vent Formation  

NSDL National Science Digital Library

This dispatch from the research vessel Atlantis discusses how hydrothermal vents are formed and why scientists monitor minute temperature changes around them. It includes an account of preparing temperature probes to be deployed for a year-long study, an explanation of deep sea vents and their hydrothermal nature and an explanation of why deep sea vents seem to spew black smoke.

314

Hydrothermal studies in the Aegean Sea  

Microsoft Academic Search

The aims of the Aegean Hydrothermal Fluxes and Biological Production project were to estimate the fluxes of fluids, chemicals, heat and bacteria, from hydrothermal vents, establish the controls on venting dynamics, measure the productivity in the region of the vents and establish the effect of the vents on biodiversity of both prokaryotes and eukaryotes. This paper presents an initial synthesis

P. R. Dando; S. Aliani; H. Arab; C. N. Bianchi; M. Brehmer; S. Cocito; J GUNDERSEN; L HOOPER; R KOLBH

2000-01-01

315

Natural saltwater upconing by boils: field measurements and numerical modeling  

NASA Astrophysics Data System (ADS)

In this study, natural saltwater upconing by boils was investigated using field measurements and numerical simulations. As one-quarter of The Netherlands lies below mean sea level, the upward flow of saline groundwater leads to the salinization of surface waters for large areas, impacting on agriculture and aquatic ecosystems. The largest seepage fluxes are found in deep polders with surface water levels maintained as low as 6 to 8 m below sea level. Recent studies showed that preferential groundwater discharge through boils is the dominant salinization source in these deep polders. Boils occur as conduits in the upper aquitard that connect the underlying aquifer to the surface through which groundwater discharges at high velocities. Groundwater preferentially discharging through boils contains up to hundred times more salt than diffuse forms of groundwater discharge. The upconing of deep saline groundwater induced by the localized, high-velocity flow through boils is the mechanism that leads to the high boil water salinities. The local boil system and associated natural salt water upconing were explored in the field in three different hydrogeological settings. Measurements of the aquifer salinity distribution, temperature, boil discharge, boil salinity and aquifer heads showed that the preferential flow through boils creates localized and narrow saltwater upconing spikes. The possibility to seal the boil at its source vent as a measure to abate surface water salinization was explored in the field. Numerical modeling with the code SEAWAT was applied to investigate the upconing processes in more detail. The field measurements were largely reproduced by the numerical model. 56 different cases, which differ in aquifer properties, salinity distribution, boil discharge and lateral regional flow,were defined to determine the most important boil salinity controlling factors. For each upconing case the sources of boil water, i.e. the contribution to boil discharge from different aquifer depths, were derived from the model results. The contributing depth distributions showed a form opposite to the aquifer salinity distribution, with higher contributions from shallower and less saline groundwater. This illustrates the importance of the density distribution in the aquifer on the saltwater upconing mechanism. The numerical results showed that the most important factors controlling the contributing depths and boil salinity are boil discharge, the horizontal hydraulic conductivity of the aquifer, the depth of the interface and the salinity (and therefore density) contrast within the aquifer. Within a small area of clustered boils, boil salinity varies between individual boils and is determined by the combination of its discharge and its position within the boil area, whereas the total discharge of boil clusters is the principal factor that controls natural saltwater upconing and total salt loads. Regional lateral flow had a large impact on the upconing mechanism in terms of flow patterns but had a minor effect on both the contribution of saline and fresh groundwater to boil discharge and boil salinity. Both measurements and model results will be presented at the EGU.

de Louw, Perry; Vandenbohede, Alexander; Werner, Adrian; Oude Essink, Gualbert

2013-04-01

316

A review on boiling heat transfer enhancement with nanofluids.  

PubMed

There has been increasing interest of late in nanofluid boiling and its use in heat transfer enhancement. This article covers recent advances in the last decade by researchers in both pool boiling and convective boiling applications, with nanofluids as the working fluid. The available data in the literature is reviewed in terms of enhancements, and degradations in the nucleate boiling heat transfer and critical heat flux. Conflicting data have been presented in the literature on the effect that nanofluids have on the boiling heat-transfer coefficient; however, almost all researchers have noted an enhancement in the critical heat flux during nanofluid boiling. Several researchers have observed nanoparticle deposition at the heater surface, which they have related back to the critical heat flux enhancement. PMID:21711794

Barber, Jacqueline; Brutin, David; Tadrist, Lounes

2011-01-01

317

Heat transfer from aluminum surfaces to pool boiling He I  

SciTech Connect

Heat transfer measurements between different aluminum surfaces and pool boiling He I at 4.21 K are reported. The samples are contained in a channel configuration similar to what might be found in a large bath cooled superconducting magnet. Results include heat transfer coefficients in the nucleate and film boiling regimes as well as values for the peak nucleate and minimum film boiling heat flux. The effects of sample orientation and surface condition are also studied.

Huang, Y.; Van Sciver, S.W. [Florida State Univ., Tallahassee, FL (United States)

1996-12-31

318

Experimental study of the coalescence phenomenon during nucleate pool boiling  

Microsoft Academic Search

This work deals with the study of the coalescence phenomenon (merging of two or more bubbles into a single larger one) during pool boiling on a duraluminium (AU4G) vertical heated wall. Various boiling curves characterising boiling (with or without coalescence) from three artificial nucleation sites a variable distance apart are presented. The heat flux ranges from 100 to 900 W\\/cm2

Jocelyn Bonjour; Marc Clausse; Monique Lallemand

2000-01-01

319

hal-00163389,version1-17Jul2007 ECI International Conference on Boiling Heat Transfer  

E-print Network

hal-00163389,version1-17Jul2007 ECI International Conference on Boiling Heat Transfer Spoleto, 7 This paper deals with the triggering mechanism of the boiling crisis, a transition from nucleate to film boiling. We observe the boiling crisis in pool saturated boiling experimentally at nearly critical

Paris-Sud XI, Université de

320

ECI International Conference on Boiling Heat Transfer Spoleto, 7-12 May 2006  

E-print Network

ECI International Conference on Boiling Heat Transfer Spoleto, 7-12 May 2006 IS CHF TRIGGERED of the boiling crisis, a transition from nucleate to film boiling. We observe the boiling crisis in pool saturated boiling experimentally at nearly critical pressure to take advantage of the slowness of the bubble

Nikolayev, Vadim S.

321

Hydrothermal pretreatment of coal before molten caustic leaching  

SciTech Connect

A hydrothermal pretreatment of coal samples before caustic leaching results in efficient sulfur removal using reduced amounts of caustic and to recovery of a higher fraction of the energy content of the feed coal than caustic leaching without the pretreatment. Pretreating an Illinois No. 6 coal with boiling water followed by a float-sink separation using 50% aqueous NaOH as the heavy medium, and then leaching the floated coal with only the caustic adhering to the float portion (less than 1 part caustic to 1 part water to 1 part coal) at 390{degrees}C for 15 minutes led to the same residual levels of sulfur in the cleaned coal (0.5%) as was obtained performing the float-sink procedure and leaching procedures on a non-prewashed coal using 2.4 parts caustic to 1 part coal. When prewashed Illinois No. 6 coal was leached with lesser amounts of caustic, the energy recoveries in the cleaned coal were about 5--10% higher than when non-prewashed coal was leached with the larger amounts of caustic.

Akhtar, S.S.; Chriswell, C.D.

1993-10-01

322

Investigation Of Pool Boiling Heat Transfer With Nanofluids.  

E-print Network

??You, Seung Mun This investigation conducts pool boiling experiments under saturated conditions (Tsat=60°C) using nanofluids as coolants. Four different nanofluids were tested including zinc oxide… (more)

Moreno, Gilberto

2007-01-01

323

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

SciTech Connect

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.

Simmons, S.F.; Keywood, M.; Keam, R.F. (Univ. of Auckland (New Zealand)); Scott, B.J. (Wairakei Research Centre, Taupo (New Zealand))

1993-07-01

324

Boiling heat transfer in compact heat exchangers  

SciTech Connect

Small circular and noncircular channels are representative of flow passages in compact evaporators and condensers. This paper describes results of an experimental study on heat transfer to the flow boiling of refrigerant- 12 in a small circular tube of diameter = 2.46 mm. The objective of the study was to assess the effect of channel size on the heat transfer coefficient and to obtain additional insights relative to the heat transfer mechanisms. The flow channel was made of brass and had an overall length of 0.9 m. The channel wall was electrically heated, and temperatures were measured on the channel wall and in the bulk fluid stream. Voltage taps were located at the same axial locations as the stream thermocouples to allow testing over an exit quality range of 0.21 to 0.94 and a large range of mass flux (63 to 832 kg/m{sup 2}s) and heat flux (2.5 to 59 kW/m{sup 2}). Saturation pressure was nearly constant, averaging 0.82 MPa for most of the testing; a few test data were also taken at a constant lower pressure of 0.52 MPa. Local heat transfer coefficients were determined experimentally. Analysis provided additional support for the conclusion, arrived at from previous studies, that a nucleation mechanism dominates for flow boiling in small channels; nevertheless, a convective-dominant region was identified at very low values of wall superheat (<{approx}3{degrees}C). Previous flow boiling studies in small channels, that did not include wall superheats this low, did not encounter the convective dominant mechanism. Conversely, cryogenic studies at very low wall superheats ({approx}l{degree}C) did not encounter the nucleation dominant regime. The apparent discrepancy is explained by the results of this study.

Tran, T.N.; Wambsganss, M.W. [Argonne National Lab., IL (United States); France, D.M. [Illinois Univ., Chicago, IL (United States). Dept. of Mechanical Engineering

1994-12-31

325

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

USGS Publications Warehouse

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. -from Author

Bischoff, J.L.

1991-01-01

326

Hydrothermal dolomite—a product of poor definition and imagination  

Microsoft Academic Search

The latest dolomite bandwagon is the “hydrothermal dolomite model”. In its present form, this bandwagon is doomed or at least very much overstated for at least two reasons: (1) there are several definitions of hydrothermal, and hardly any author specifies which one s\\/he is using; (2) very few of the dolomites hitherto called hydrothermal have been demonstrated to be hydrothermal

Hans G Machel; Jeff Lonnee

2002-01-01

327

Fluid density control on vapor-liquid partitioning of metals in hydrothermal systems  

NASA Astrophysics Data System (ADS)

Hot aqueous fluids, both vapor and saline liquid, are primary transporting media for metals in hydrothermal-magmatic systems. Despite the growing geological evidence that the vapor phase, formed through boiling of magmatic ore-bearing fluids, can selectively concentrate and transport metals, the physical-chemical mechanisms that control the metal vapor-liquid fractionation remain poorly understood. We performed systematic experiments to investigate the metal vapor-liquid partitioning in model water-salt-gas systems H2O-NaCl-KCl-HCl at hydrothermal conditions. Measurements show that equilibrium vapor-liquid fractionation patterns of many metals are directly related to the densities of the coexisting vapor and liquid phases. Despite differences in the vapor-phase chemistry of various metals that form hydroxide, chloride, or sulfide gaseous molecules of contrasting volatile properties, water-solute interaction is a key factor that controls the metal transfer by vapor-like fluids in Earth's crust. These findings allow quantitative prediction of the vapor-liquid distribution patterns and vapor-phase metal transport in a wide range of conditions. Our density model accounts well for the vapor-brine distribution patterns of Na, Si, Fe, Zn, As, Sb, and Ag observed in fluid inclusions from magmatic-hydrothermal deposits. For Au and Cu, the partitioning in favor of the liquid phase, predicted in a sulfur-free system, contrasts with the copper and gold enrichment observed in natural vapor-like inclusions. The formation of stable complexes of Cu and Au with reduced sulfur may allow for their enhanced transport by sulfur-enriched magmatic-hydrothermal vapors.

Pokrovski, Gleb S.; Roux, Jacques; Harrichoury, Jean-Claude

2005-08-01

328

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

NASA Astrophysics Data System (ADS)

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.

Korzenski, Michael Burt

329

Dynamics of the Yellowstone hydrothermal system  

NASA Astrophysics Data System (ADS)

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.

Hurwitz, Shaul; Lowenstern, Jacob B.

2014-09-01

330

Dynamics of the Yellowstone hydrothermal system  

USGS Publications Warehouse

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.

Hurwitz, Shaul; Lowenstern, Jacob B.

2014-01-01

331

Seawater bicarbonate removal during hydrothermal circulation  

NASA Astrophysics Data System (ADS)

High temperature fluids sampled at hydrothermal vents represent a complex alteration product of water-rock reactions on a multi-component mixture of source fluids. Sources to high-temperature hydrothermal samples include the 'original' seawater present in the recharge limb of circulation, magmatically influenced fluids added at depth as well as any seawater entrained during sampling. High-temperature hydrothermal fluids are typically enriched in magmatic volatiles, with CO2 the dominant species, characterized by concentrations of 10's-100's of mmol/kg (1, 2). Typically, the high concentration of CO2 relative to background seawater bicarbonate concentrations (~2.3 mmol/kg) obscures a full analysis of the fate of seawater bicarbonate during high-temperature hydrothermal circulation. Here we present data from a suite of samples collected over the past 15 years from high-temperature hydrothermal vents at 9N, Endeavour, Lau Basin, and the MAR that have endmember CO2 concentrations less than 10 mmol/kg. Using stable and radiocarbon isotope measurements these samples provide a unique opportunity to examine the balance between 'original' seawater bicarbonate and CO2 added from magmatic sources. Multiple lines of evidence from multiple hydrothermal settings consistently points to the removal of ~80% of the 'original' 2.3 mmol/kg seawater bicarbonate. Assuming that this removal occurs in the low-temperature, 'recharge' limb of hydrothermal circulation, this removal process is widely occurring and has important contributions to the global carbon cycle over geologic time. 1. Lilley MD, Butterfield DA, Lupton JE, & Olson EJ (2003) Magmatic events can produce rapid changes in hydrothermal vent chemistry. Nature 422(6934):878-881. 2. Seewald J, Cruse A, & Saccocia P (2003) Aqueous volatiles in hydrothermal fluids from the Main Endeavour Field, northern Juan de Fuca Ridge: temporal variability following earthquake activity. Earth and Planetary Science Letters 216(4):575-590.

Proskurowski, G. K.; Seewald, J.; Sylva, S. P.; Reeves, E.; Lilley, M. D.

2013-12-01

332

(Boiling water reactor (BWR) CORA experiments)  

SciTech Connect

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.

Ott, L.J.

1990-10-16

333

77 FR 38338 - Dairyland Power Cooperative; La Crosse Boiling Water Reactor Exemption From Certain Security...  

Federal Register 2010, 2011, 2012, 2013

...Power Cooperative; La Crosse Boiling Water Reactor Exemption From Certain...1.0 Background The La Crosse Boiling Water Reactor (LACBWR) is owned and...forced-circulation, direct-cycle boiling water reactor as its heat source....

2012-06-27

334

77 FR 36014 - Initial Test Program of Emergency Core Cooling Systems for Boiling-Water Reactors  

Federal Register 2010, 2011, 2012, 2013

...Emergency Core Cooling Systems for Boiling-Water Reactors AGENCY: Nuclear Regulatory...Emergency Core Cooling Systems for Boiling- Water Reactors.'' This guide describes...cooling systems (ECCSs) for boiling-water reactors (BWRs). DATES:...

2012-06-15

335

77 FR 38339 - Dairyland Power Cooperative, La Crosse Boiling Water Reactor Exemption From Certain Security...  

Federal Register 2010, 2011, 2012, 2013

...Power Cooperative, La Crosse Boiling Water Reactor Exemption From Certain...1.0 Background The La Crosse Boiling Water Reactor (LACBWR) is owned and...forced-circulation, direct-cycle boiling water reactor as its heat source....

2012-06-27

336

A method of correlating heat transfer data for surface boiling of liquids  

E-print Network

A method based an a logical uxplanation of the meani of beat transfer associated with the boiling process is presented for correlating heat transfer data for nucleate boiling of liquids for the case of pool boiling. Tbe ...

Rohsenow, Warren M.

1951-01-01

337

Hydrothermal Synthesis of Loessial Mesoporous Materials  

NASA Astrophysics Data System (ADS)

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.

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

2010-11-01

338

What Defines a Separate Hydrothermal System  

SciTech Connect

Separate hydrothermal systems can be defined in a variety of ways. Criteria which have been applied include separation of heat source, upflow, economic resource and geophysical anomaly. Alternatively, connections have been defined by the effects of withdrawal of economically useful fluid and subsidence, effects of reinjection, changes in thermal features, or by a hydrological connection of groundwaters. It is proposed here that: ''A separate hydrothermal system is one that is fed by a separate convective upflow of fluid, at a depth above the brittle-ductile transition for the host rocks, while acknowledging that separate hydrothermal systems can be hydrologically interconnected at shallower levels''.

Lawless, J.V.; Bogie, I.; Bignall, G.

1995-01-01

339

Candy Chemosynthesis: Biochemistry of Hydrothermal Vents  

NSDL National Science Digital Library

In this activity, students will differentiate between requirements for life in extreme environments such as hydrothermal vents and other environments and will use soft candy as a model to create a visual image of chemicals involved in autotrophic nutrition. As they review the biochemistry of hydrothermal vents, they will discover what chemicals are used by autotrophs in extreme environments in the deep ocean and how these chemicals differ from those used by terrestrial autotrophs. They will also study a diagram showing how a hydrothermal vent (black smoker) acquires the elements and compounds that deep-sea autotrophs require.

340

Hydrothermal carbonization of lignocellulosic biomass.  

PubMed

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

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

2012-08-01

341

Hyperbaric Hydrothermal Atomic Force Microscope  

DOEpatents

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.

Knauss, Kevin G. (Livermore, CA); Boro, Carl O. (Milpitas, CA); Higgins, Steven R. (Laramie, WY); Eggleston, Carrick M. (Laramie, WY)

2003-07-01

342

Hyperbaric hydrothermal atomic force microscope  

DOEpatents

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.

Knauss, Kevin G. (Livermore, CA); Boro, Carl O. (Milpitas, CA); Higgins, Steven R. (Laramie, WY); Eggleston, Carrick M. (Laramie, WY)

2002-01-01

343

Explosive boiling at very low heat fluxes: A microgravity phenomenon  

SciTech Connect

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.

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

1993-11-01

344

Heat Transfer Mechanisms During Flow Boiling in Microchannels  

Microsoft Academic Search

The forces due to surface tension, inertia, and momentum change during evaporation in microchannel govern the two- phase flow patterns and the heat transfer characteristics during flow boiling. These forces are analyzed in this paper, and two new non-dimensional groups, K1 and K 2, relevant to flow boiling phenomenon are derived. These groups are able to represent some of the

Satish G. Kandlikar

2004-01-01

345

Bubble dynamics in boiling under high heat flux pulse heating  

Microsoft Academic Search

A new theoretical model of bubble behavior in boiling water under high heat flux pulse is presented. The essence of the model is nucleation in the superheated liquid followed by instantaneous formation of a vapor film, rapid bubble growth due to the pressure impulse, and cavitation bubble collapse. To check the model, boiling of methanol under 5 â¼ 50 MW

A. Asai

1991-01-01

346

Effects of water in film boiling over liquid metal melts  

SciTech Connect

Liquid-liquid boiling experiments have been performed with H/sub 2/O and liquid metal melts in the 100-series test matrix (Runs 121, 126, 127) and the VE test matrix. Some of the pre-explosion unstable film boiling data as well as observations from the explosive series have been previously reported.

Greene, G.A.; Finfrock, C.; Burson, S.B.

1986-01-01

347

Prospective Primary School Teachers' Perceptions on Boiling and Freezing  

ERIC Educational Resources Information Center

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…

Senocak, Erdal

2009-01-01

348

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

349

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

350

Investigation of Noises in Boiling on an Electrically Heated Wire  

Microsoft Academic Search

An experimental investigation of noises in boiling on an electrically heated wire in a water volume has been carried out. Its results point to the fact that the type of heating of the heat-exchange surface has a significant influence on the processes of boiling and the noises appearing as a result of them. It is shown that heating by a

A. V. Korolev; A. N. Litvin

2002-01-01

351

Explosive Boiling at Very Low Heat Fluxes: A Microgravity Phenomenon  

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

352

A nucleate boiling model for structured enhanced surfaces  

Microsoft Academic Search

Flow visualization experiments were used to establish the mechanism of boiling on enhanced surfaces having sub-surface tunnels with surface pores. Based on this mechanism, a semi-analytical model for nucleate boiling is proposed. The model is validated for data covering a range of tunnel and pore dimensions and supporting bubble dynamics data. The model assumes the tunnel is vapor filled, except

Liang-Han Chien; Ralph L. Webb

1998-01-01

353

Nucleate boiling of water in twisted-tape swirled flow  

SciTech Connect

This paper analyzes nucleate boiling in twisted-tape swirled water flow. The transverse flow velocity in the wall region, generated by the density gradient and acceleration, is estimated. It is concluded that the turbulence has a significant effect on the growth of vapor bubbles, decreasing the rate of nucleate boiling without simultaneously increasing the convective component to compensate for this effect.

Kudryavtsev, I.S.; Lekakh, B.M.; Paskar, B.L.; Fedorovich, Y.D. (Polzunov Boiler and Turbine Inst., Leningrad (SU))

1990-01-01

354

A transient micro-convection model of nucleate pool boiling  

Microsoft Academic Search

This work advances the fundamental understanding of nucleate pool boiling on plain surfaces. A model is developed for prediction of the nucleate boiling coefficient as a function of the bubble dynamics characteristics (nucleation site density, bubble departure diameter and bubble frequency). This work extends that of Mikic and Rohsenow, who developed a model based on transient conduction to the superheated

Ralph L. Webb

1997-01-01

355

Minerals produced during cooling and hydrothermal alteration of ash flow tuff from Yellowstone drill hole Y-5  

USGS Publications Warehouse

A rhyolitic ash-flow tuff in a hydrothermally active area within the Yellowstone caldera was drilled in 1967, and cores were studied to determine the nature and distribution of primary and secondary mineral phases. The rocks have undergone a complex history of crystallization and hydrothermal alteration since their emplacement 600,000 years ago. During cooling from magmatic temperatures, the glassy groundmass underwent either devitrification to alkali feldspar + ??-cristobalite ?? tridymite or granophyric crystallization to alkali feldspar + quartz. Associated with the zones of granophyric crystallization are prismatic quartz crystals in cavities similar to those termed miarolitic in plutonic rocks. Vapor-phase alkali feldspar, tridymite, magnetite, and sporadic ??-cristobalite were deposited in cavities and in void spaces of pumice fragments. Subsequently, some of the vapor-phase alkali feldspar crystals were replaced by microcrystalline quartz, and the vapor-phase minerals were frosted by a coating of saccharoidal quartz. Hydrothermal minerals occur primarily as linings and fillings of cavities and fractures and as altered mafic phenocrysts. Chalcedony is the dominant mineral related to the present hydrothermal regime and occurs as microcrystalline material mixed with various amounts of hematite and goethite. The chalcedony displays intricate layering and was apparently deposited as opal from silica-rich water. Hematite and goethite also replace both mafic phenocrysts and vapor-phase magnetite. Other conspicuous hydrothermal minerals include montmorillonite, pyrite, mordenite, calcite, and fluorite. Clinoptilolite, erionite, illite, kaolinite, and manganese oxides are sporadic. The hydrothermal minerals show little correlation with temperature, but bladed calcite is restricted to a zone of boiling in the tuff and clearly was deposited when CO2 was lost during boiling. Fractures and breccias filled with chalcedony are common throughout Y-5 and may have been produced by rapid disruption of rock caused by sudden decrease of fluid pressure in fractures, most likely a result of fracturing during resurgent doming in this part of the Yellowstone caldera. The chalcedony probably was deposited as opal or ??-cristobalite from a pre-existing silica floc that moved rapidly into the fractures and breccias immediately after the sudden pressure drop. ?? 1978.

Keith, T.E.C.; Muffler, L.J.P.

1978-01-01

356

Simulation of Submarine Hydrothermal Systems: IV. Fluid Flow in Active Arc-Related Volcanoes  

NASA Astrophysics Data System (ADS)

Fluid flow through submarine hydrothermal systems transports a major part of the Earth's heat to its surface and greatly impacts the chemistry of crust and overlying ocean. Seafloor high-temperature vent sites are manifestations of active ore-forming systems and can be regarded as modern analogues of massive sulfide deposits whose ancient equivalents have been exploited as world-class mines on land. Recent research cruises dedicated to seafloor hydrothermal activity along convergent plate boundaries, e.g. along the intra-oceanic Kermadec arc, have systematically surveyed and sampled numerous hydrothermal plumes. Follow-up submersible dives show venting that ranges from relatively high temperature (~300° C), metal-rich fluids to lower temperature, gas-rich and metal-poor fluids. Some of these vent sites show evidence for significant contributions from magmatic sources. The physics of such systems is complex because the seawater-derived hydrothermal fluid can mix with ambient seawater and phase-separate, either via boiling or condensation, into a low-salinity vapor and a high-salinity brine. In order to model the sub-seafloor hydrology with numerical transport simulation techniques, a newly developed pressure-enthalpy-salinity scheme has been used, which includes the full phase relations of the NaCl-H2O system up to 1000° C and accurately captures boiling, condensation, and salt precipitation. We have designed a new numerical model, based on observations in currently active arc-related systems, to assess the influence of first-order physical parameters (such as seafloor topography and the contribution of magmatic fluids) to fluid flow patterns, thermal structure, and phase-separation. Preliminary results of these simulations will be presented and compared with data recently obtained from simulations at mid-ocean ridge systems. In our ongoing project, we aim to predict the optimal conditions for which metal-rich magmatic vapor may cool and contract to an aqueous liquid, which in turn is likely to generate particularly Cu- and Au-rich mineralization on the seafloor.

Gruen, G.; Coumou, D.; Weis, P.; Driesner, T.; de Ronde, C.; Heinrich, C. A.

2008-12-01

357

Microbiological Effectiveness of Disinfecting Water by Boiling in Rural Guatemala  

PubMed Central

Boiling is the most common means of treating water in the home and the benchmark against which alternative point-of-use water treatment options must be compared. In a 5-week study in rural Guatemala among 45 households who claimed they always or almost always boiled their drinking water, boiling was associated with a 86.2% reduction in geometric mean thermotolerant coliforms (TTC) (N = 206, P < 0.0001). Despite consistent levels of fecal contamination in source water, 71.2% of stored water samples from self-reported boilers met the World Health Organization guidelines for safe drinking water (0 TTC/100 mL), and 10.7% fell within the commonly accepted low-risk category of (1–10 TTC/100 mL). As actually practiced in the study community, boiling significantly improved the microbiological quality of drinking water, though boiled and stored drinking water is not always free of fecal contaminations. PMID:20207876

Rosa, Ghislaine; Miller, Laura; Clasen, Thomas

2010-01-01

358

Conversion of direct process high-boiling residue to monosilanes  

DOEpatents

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.

Brinson, Jonathan Ashley (Vale of Glamorgan, GB); Crum, Bruce Robert (Madison, IN); Jarvis, Jr., Robert Frank (Midland, MI)

2000-01-01

359

Stability of electric heaters in the boiling heat transfer process  

SciTech Connect

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.

Loeffler, R.I.

1991-01-01

360

FEASIBILITY STUDY FOR THE CONCEPTUAL DESIGN OF ADUAL-CORE BOILING SUPERHEAT REACTOR.  

E-print Network

??For research concerning economical applications of high temperature reactortechnology, a novel approach for creating a Boiling Superheat Reactor (BSR) byaugmenting an Advanced Boiling Water Reactor… (more)

Ross, Jacob

2009-01-01

361

Boiled coffee and blood pressure. A 14-week controlled trial.  

PubMed

The question of whether long-term elimination of coffee from the diet lowers blood pressure has not been settled. Consumption of Scandinavian-style "boiled coffee" is associated with coronary heart disease. However, little is known about the effect of brewing method on the blood pressure-raising potential of coffee. We have studied the effects on blood pressure and heart rate of total elimination of coffee and tea in comparison with drinking boiled coffee consumed as such, or boiled coffee consumed after filtration through paper filter. Thirty-one women and 33 men first consumed 6 cups/day of boiled and filtered coffee for 17 days. Then they were randomly divided into three groups, which for the next 79 days received either unfiltered boiled coffee (caffeine content 860 mg/l), boiled-and-filtered coffee (887 mg caffeine/l), or no coffee, the latter being replaced by fruit juice and mineral water. Total elimination of coffee did not significantly affect blood pressure or heart rate relative to boiled-and-filtered coffee. In subjects who drank boiled coffee, mean ambulant systolic blood pressure rose significantly relative to those who consumed boiled-and-filtered coffee (mean difference +/- SEM, 3.1 +/- 1.1 mm Hg, p = 0.006). This response showed a tendency to be stronger for women (4.5 +/- 1.8 mm Hg) than for men (1.7 +/- 1.2 mm Hg). We conclude that elimination of filtered coffee has no substantial long-term effect on blood pressure, but consumption of unfiltered boiled coffee may cause a slight but significant rise in systolic blood pressure. PMID:1937663

van Dusseldorp, M; Smits, P; Lenders, J W; Thien, T; Katan, M B

1991-11-01

362

Magmatic intrusions and hydrothermal systems on Mars  

NASA Technical Reports Server (NTRS)

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.

Gulick, V. C.

1992-01-01

363

Biomass reforming processes in hydrothermal media  

E-print Network

While hydrothermal technologies offer distinct advantages in being able to process a wide variety of biomass feedstocks, the composition of the feedstock will have a large effect on the processing employed. This thesis ...

Peterson, Andrew A

2009-01-01

364

Analytical modeling of complete Nukiyama curves corresponding to expected low void fraction at high subcooling and flow rate  

SciTech Connect

On the basis of a new hypothesis of thermodynamic states (the superheated wall layer is not metastable but saturated at locally elevated pressure), an analytical estimation is presented of the whole boiling curve [except critical heat flux (CHF), but fixed at this point, known by experiments or correlation]. The curvature of the boiling curve (bubbly flow) is deduced from thermodynamics of irreversible processes. The wall temperature corresponding to departure from nucleate boiling is calculated from balances of momentum at the interfaces, based on the assumption that the speed of sound may be a limit for maximum evaporation mass flux and thereby heat flux, i.e., CHF. Heat flux during transition boiling is determined from balance of energy at the rewetting front. The Leidenfrost temperature, as well as wall temperature at CHF, can be calculated analytically without using empirical coefficients. Heat flux of bubbly flow and transition boiling can be matched at any empirical CHF point. All these results are determined from properties of state alone, i.e., the models can be verified for all fluids including water and liquid metals (so far at moderate heat fluxes). 52 refs., 11 figs., 2 tabs.

Schroeder-Richter, D. [Technische Universitaet Berlin (Germany)

1996-07-01

365

Studies on Sodium Boiling Accidents in a Large Fast Breeder Reactor, (II) Radial Propagation of Sodium Boiling by Reactivity Effect  

Microsoft Academic Search

A computer code BORE was developed, with which analyses were performed on channel plugging accidents that would occur on a 1,500 MWe LMFBR. The BORE code calculated the dynamic characteristics of coolant boiling and fuel failure propagation radially in the core, and the requirements of core instrumentation systems were also analyzed. The results show that coolant boiling and\\/or fuel failure

Kunio NAGASHIMA; Masaji TEZUKA

1971-01-01

366

Chemical environments of submarine hydrothermal systems  

NASA Technical Reports Server (NTRS)

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.

Shock, Everett L.

1992-01-01

367

Rare earth element systematics in hydrothermal fluids  

Microsoft Academic Search

Rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in Italy, Dominica, Valles Caldera, Salton Sea and the Mid-Atlantic Ridge. The measured abundances show that hydrothermal activity is not expected to affect the REE balance of either continental or oceanic rocks. The REE enrichment of the solutions increases when the pH decreases. High-temperature solutions (>230°C) percolating

Annie Michard

1989-01-01

368

Rare earth element systematics in hydrothermal fluids  

SciTech Connect

Rare earth element concentrations have been measured in hydrothermal solutions from geothermal fields in Italy, Dominica, Valles Caldera, Salton Sea and the Mid-Atlantic Ridge. The measured abundances show that hydrothermal activity is not expected to affect the REE balance of either continental or oceanic rocks. The REE enrichment of the solutions increases when the pH decreases. High-temperature solutions (> 230{degree}C) percolating through different rock types may show similar REE patterns.

Michard, A. (Centre de Recherches Petrographiques et Geochimiques, Vandoeuvre-les-Nancy (France))

1989-03-01

369

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

NASA Technical Reports Server (NTRS)

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.

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

1973-01-01

370

Hybrid modelling of a sugar boiling process  

E-print Network

The first and maybe the most important step in designing a model-based predictive controller is to develop a model that is as accurate as possible and that is valid under a wide range of operating conditions. The sugar boiling process is a strongly nonlinear and nonstationary process. The main process nonlinearities are represented by the crystal growth rate. This paper addresses the development of the crystal growth rate model according to two approaches. The first approach is classical and consists of determining the parameters of the empirical expressions of the growth rate through the use of a nonlinear programming optimization technique. The second is a novel modeling strategy that combines an artificial neural network (ANN) as an approximator of the growth rate with prior knowledge represented by the mass balance of sucrose crystals. The first results show that the first type of model performs local fitting while the second offers a greater flexibility. The two models were developed with industrial data...

Lauret, Alfred Jean Philippe; Gatina, Jean Claude

2012-01-01

371

Boiling water with ice: Effect of pressure on the boiling point of water  

NSDL National Science Digital Library

This guided inquiry activity, in which ice is used to boil water in a Florence flask, works well in the introductory class to a chemistry or physical science course. The students will learn the difference between observation and inference and apply this understanding to various other situations in which observations and inferences must be made. The students will also use outside sources to try to explain why the activity worked.

372

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

NASA Astrophysics Data System (ADS)

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 280-300Ë? C range, while in the reinjection zones are 245-250Ë? 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 191-344Ë? 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 100Ë? 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.

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

2009-04-01

373

Enceladus Plumes: A Boiling Liquid Model  

NASA Astrophysics Data System (ADS)

Following the discovery of H2O vapor and particle plumes from the tiger stripes at the south pole of Enceladus (Porco et al., 2006), observational and theoretical studies have been conducted to understand the plume mechanism (e.g., Schmidt et al., 2008; Kieffer et al., 2009; Ingersoll and Pankine, 2010). Although the “Ice Chamber Model”, which assumes that ice sublimation under the stripes causes the plumes, has successfully explained the plume mass flux (e.g., Nimmo et al., 2007; Ingersoll and Pankine, 2010), it cannot explain the high salinity in the plume (Postberg et al., 2009). Ice particles condensing from a vapor are relatively salt free, but ice particles derived from a salty liquid can have high salinity. Therefore we have investigated the “Boiling Liquid Model”, which assumes that liquid H2O under the stripes causes the plumes. With conservation of mass, momentum and energy, we built a simple atmospheric model that includes controlled boiling and gas-ice wall interaction. We first assumed that the heat radiated to space comes entirely from the heat generated by condensation of the gas onto the ice wall. We varied the width (0.1-1 m) and the height (5-4000 m) of the crack as parameters. We find that the escaping vapor flux can be relatively close to the observed value (250±100 kg/s, Hansen et al., 2006, 2008) but the radiated heat flux is only 1 GW, which is much less than the observed value (15.8 GW, Howett et al., 2011). Other models (Nimmo et al., 2007; Abramov and Spencer, 2009) also have the same difficulty accounting for the observed value. We then investigated the additional heat radiated by the particles after they come out of the crack. We built a simple model to estimate the size distributions of these condensed ice particles and their radiative properties.

Nakajima, Miki; Ingersoll, A. P.

2012-10-01

374

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

USGS Publications Warehouse

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.

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

375

Transition boiling heat transfer and the film transition regime  

NASA Astrophysics Data System (ADS)

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.

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

1987-08-01

376

Enhanced pool boiling heat transfer with surface attachment  

SciTech Connect

This paper reports on a pool boiling experiment with either water or Freon-113 that was conducted to investigate nucleate boiling from a heated wall with either a spherical or a cylindrical attachment. The result revealed that nucleate boiling can be enhanced by applying a horizontal cylindrical attachment to a vertical heated wall, owing to the favorable thermal environment characterized by a small-gradient liquid temperature profile within the restricted regions between the attachment and the heated wall. Nucleate boiling is enhanced in terms of a lower wall superheat required for incipient boiling and more bubbles generated than from an open heated wall. As a result of the enhanced nucleate boiling, heat transfer of the vertical heated wall above the attachment was improved due to excessive bubbles moving upward along the heated wall, causing removal of the thermal layer near the wall and evaporation of the thin liquid film between the bubbles and the wall. The boiling curve hysteresis with Freon-113 was significantly reduced as a result. The effects of diameter, length, and surface roughness of the cylindrical attachment were also investigated.

Chyu, M.C.; Mghamis, A.M. (Dept. of Mechanical Engineering, Texas Technical Univ., Lubbock, TX (US))

1992-01-01

377

Nucleate boiling in drag-reducing polymer solutions  

SciTech Connect

Two types of experiment have been done to study the effects of polymer additives in nucleate boiling for plates and wires. Here, boiling on a flat surface is simulated by placing a flat unheated surface immediately underneath an electrically heated platinum wire. Saturated nucleate pool boiling curves were measured for water and solutions of six different polymers at various concentrations. For a bare wire and a simulated flat surface, the nucleate boiling curves are qualitatively similar. For equal heat fluxes, the temperature difference increases as the relative viscosity increases, although the temperature difference for the simulated flat surface is less than that for the bare wire. The observed changes in the nucleate boiling curves for polymer solutions are in qualitative agreement with those predicted using the Rohsenow correlation to account for change in the solution viscosity. These results show that for both wires and simulated flat surfaces, drag-reducing additives will reduce the heat transfer rate in nucleate boiling. Bubble dynamics on the heated wire and simulated flat surface were also measured using a high speed movie camera for water and Separan AP-30 at a relative viscosity of 1.16. The data were used to determine the relative contribution to the boiling heat flux of latent heat transport by bubbles, natural convection heat transfer, and enhanced convection heat transfer.

Jeun, G.

1986-01-01

378

Calcium Isotope Fractionation in Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

We present measurements of stable Ca isotopes (?44/40Ca) from hydrothermal fluids (Long Valley, California) and epidote from fossil hydrothermal systems (Troodos and Betts Cove ophiolites). Hydrothermal fluids in Long Valley show a progressive increase in the heavy isotopes of Ca (?44/40Ca +0.56‰ relative to the initial thermal fluid) with decreasing temperature, Ca concentration, Ca/Sr and CO2 concentration. The increase in the ?44/40Ca along the hydrothermal fluid flow path is potentially consistent with the precipitation of hydrothermal calcite (which would be isotopically lighter) or mixing between the thermal fluid and meteoric water. We favor the former explanation because non-linear relationships between CO2 concentrations and noble gasses suggest that decreasing CO2 concentrations are primarily due to reservoir degassing, which would likely drive calcite precipitation (e.g. Arnorsson cont. min. pet, 1978). Epidote mineral separates from the Betts Cove (Newfoundland, early Ordovician) and Troodos (Cyprus, Cretaceous) ophiolites are isotopically light relative to bulk silicate earth (?44/40Ca ranges from -0.7 to 0.0‰). The epidote ?44/40Ca is not correlated with calculated fluid temperatures or 87Sr/86Sr measured in the epidote but is negatively correlated with the epidote Sr/Ca. Black smoker fluids, which are thought to be related to epidote formation in ophiolites, have ?44/40Ca of about 0-0.2‰, meaning that epidote Ca is consistently lighter than the inferred fluids from which they precipitate (Amini et al, GCA, 2008). To explain the complimentary Long Valley hydrothermal fluid and fossil epidote data there must be a mechanism for fractionating Ca isotopes at hydrothermal temperatures. Equilibrium fractionation of Ca isotopes should be close to 0‰ at high temperatures (100-400°C), implying that any Ca isotopic fractionation between fluid and hydrothermal minerals is likely a kinetic effect. Experimental data suggest that, for example, epidote equilibrium dissolution rates are about 0.3um/y (Wood and Walther, Science, 1983) while observations of epidote growth rates in geothermal systems are 73 um/y (Browne et al, Am Min, 1989). DePaolo (2009 Goldschmidt abstract) calculated that kinetic isotope fractionation between fluids and minerals should occur if net precipitation rates are greater than the equilibrium dissolution rate. If the estimates for dissolution and net precipitation rates for epidote are representative of most hydrothermal systems then epidote Ca should commonly have ?44/40Ca lighter than the associated fluid. Ocean ridge hydrothermal fluids should be slightly enriched in the heavy isotopes of Ca compared to oceanic crust as recently observed (Amini et al, GCA, 2008).

Brown, S. T.; Depaolo, D. J.; Turchyn, A. V.; Kennedy, B. M.; Alt, J.; Bedard, J. H.; Skulski, T.

2009-12-01

379

Characterizing preferential groundwater discharge through boils using temperature  

NASA Astrophysics Data System (ADS)

In The Netherlands, preferential groundwater discharge trough boils is a key process in the salinization of deep polders. Previous work showed that boils also influence the temperature in the subsurface and of surface water. This paper elaborates on this process combining field observations with numerical modeling. As is the case for salinity, a distinct anomaly in the subsurface and surface water temperature can be attributed to boils. Lines of equal temperature are distorted towards the boil, which can be considered as an upconing of the temperature profile by analogy of the upconing of a fresh-saltwater interface. The zone of this distortion is limited to the immediate vicinity of the boil, being about 5 m in the aquitard which holds the boil's conduit, or maximum a few dozens of meters in the underlying aquifer. In the aquitard, heat transport is conduction dominated whereas this is convection dominated in the aquifer. The temperature anomaly differs from the salinity anomaly by the smaller radius of influence and faster time to reach a new steady-state of the former. Boils discharge water with a temperature equal to the mean groundwater temperature. This influences the yearly and diurnal variation of ditch water temperature in the immediate vicinity of the boil importantly but also the temperature in the downstream direction. Temporary nature of the boil (e.g. stability of the conduit, discharge rate), uncertainty on the 3D construction of the conduit and heterogeneity of the subsoil make it unlikely that temperature measurements can be interpreted further than a qualitative level.

Vandenbohede, A.; de Louw, P. G. B.; Doornenbal, P. J.

2014-03-01

380

A Fundamental Study of Nucleate Pool Boiling Under Microgravity  

NASA Technical Reports Server (NTRS)

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.

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

1996-01-01

381

A fundamental study of nucleate pool boiling under microgravity  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

382

Hydrothermal carbonization of agricultural residues.  

PubMed

The work presented in this article addresses the application of hydrothermal carbonization (HTC) to produce a solid fuel named HTC-Biochar, whose characteristics are comparable to brown coal. Several batch HTC experiments were performed using agricultural residues (AR) as substrates, commonly treated in farm-based biogas plants in Germany. Different AR were used in different combinations with other biomass residues. The biogas potential from the resulting process water was also determined. The combination of different AR lead to the production of different qualities of HTC-Biochars as well as different mass and energy yields. Using more lignocellulosic residues lead to higher mass and energy yields for the HTC-Biochar produced. Whilst residues rich in carbohydrates of lower molecular weight such as corn silage and dough residues lead to the production of a HTC-Biochar of better quality and more similar to brown coal. Process water achieved a maximum of 16.3 L CH4/kg FM (fresh matter). PMID:23735795

Oliveira, Ivo; Blöhse, Dennis; Ramke, Hans-Günter

2013-08-01

383

Microbial interactions with hydrothermal fluids  

NASA Astrophysics Data System (ADS)

When copious populations of animals clustering around deep-sea hydrothermal vents were first observed [Lonsdale, 1977, Ballard, 1977; Corliss et al., 1979], the foremost question concerned the origin of these unexpectedly high quantities of biomass. The deep sea has long been known as a desert-like environment, the input of energy for the heterotrophic production of biomass in the absence of light being limited to the sedimenting of particulate organic matter from the photosynthetically productive surface waters to the bottom. The decomposition and mineralization of this organic carbon occurs largely in the upper 200-300 m layers of the world oceans averaging at about 95% of their total primary productivity. Of the renaming 5% only about one fifth reaches the sea floor at greater depths in particulate form [e.g. Honjo and Manganini, 1993]. The scant benthic deep-sea animal populations, their diversity and feeding strategies reflect this limited particulate food source [Sanders et al., 1972]. Some of this particulate organic matter is replenished from dissolved organic carbon by microbial growth, the so-called "microbial loop".

Jannasch, Holger W.

384

Pool and flow boiling in variable and microgravity  

NASA Technical Reports Server (NTRS)

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.

Merte, Herman, Jr.

1994-01-01

385

Spatio-temporal analysis of nucleate pool boiling: identi cation of nucleation sites using  

E-print Network

Spatio-temporal analysis of nucleate pool boiling: identi#12;cation of nucleation sites using non are often limited by the available techniques. These limitations are especially evident in nucleate boiling boiling experiment. Spatio-temporal data for the wall temperature in pool nu- cleate boiling of water

McSharry, Patrick E.

386

NUMERICAL SIMULATION OF POOL BOILING FOR STEADY STATE AND TRANSIENT HEATING  

E-print Network

1 NUMERICAL SIMULATION OF POOL BOILING FOR STEADY STATE AND TRANSIENT HEATING Ying He, Masahiro Simulation, Pool boiling, Transient boiling ABSTRACT It's believed that the macrolayer plays an important role in nucleate and transition boiling heat transfer at high heat flux. Many experiments have been

Maruyama, Shigeo

387

Scale effects on flow boiling heat transfer in microchannels: A fundamental perspective  

E-print Network

Scale effects on flow boiling heat transfer in microchannels: A fundamental perspective Satish G Accepted 25 December 2009 Available online 20 February 2010 Keywords: Flow boiling Boiling Microchannels Mechanisms Scale Scaling a b s t r a c t Flow boiling in microchannels has received considerable attention

Kandlikar, Satish

388

Hydrodynamics and heat transfer during flow boiling instabilities in a single microchannel  

E-print Network

Hydrodynamics and heat transfer during flow boiling instabilities in a single microchannel July 2008 Keywords: Boiling Microchannels Visualisation Flow boiling instabilities Heat transfer a b s t r a c t Boiling in microchannels is widely considered as one of the front runners in process

Aussillous, Pascale

389

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

ERIC Educational Resources Information Center

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…

Struyf, Jef

2011-01-01

390

Fluid Flow Simulations of an Active Arc-Related Submarine Hydrothermal System  

NASA Astrophysics Data System (ADS)

Active high-temperature vents at the seafloor greatly contribute to the heat transport system at the Earth's surface and significantly influence the chemistry of crust and overlying ocean. While mid-ocean ridge systems have been intensely studied in the last decades, hydrothermal activity along convergent plate boundaries has received deeper attention only in the last few years. Brothers volcano is the most hydrothermally active volcano situated along the intra-oceanic Kermadec arc, northeast of North Island, New Zealand. Recent detailed surveys of hydrothermal plumes at Brothers volcano picture several distinct vent sites at different localities within the volcanic edifice. Venting ranges from lower temperature, gas-rich and metal-poor fluids to relatively high temperature (~300 °C), metal-rich fluids. However, the sub-surface structure of these systems and the contribution of magmatic sources are not well understood yet. In order to model the sub-seafloor hydrodynamics of Brothers volcano, a numerical transport scheme has been applied, using a combined finite element - finite volume method which computes multi-phase fluid flow and describes heat transport on basis of enthalpy, pressure, and salinity. Our process code covers the full phase relations of the binary NaCl-H2O system up to 1000 °C and accurately captures boiling, condensation, and salt precipitation. Numerical simulations for varying first-order physical parameters such as water depth and seafloor topography, rock permeability, and a heat source with or without a deep magmatic fluid source have been conducted. Our results show that seafloor topography controls the spatial distribution of venting sites and the input of a magmatic fluid source affects the style of hydrothermal venting. In this ongoing project, by combining simulation results with real observations in Brothers volcano and other currently active arc-related submarine volcanoes, we aim to present a new understanding of the sub-surface hydrology, the interaction of seawater with magmatic fluids, and subsequently the conditions to generate particularly Cu- and Au-rich mineralization within such magmatic-hydrothermal systems.

Gruen, G.; de Ronde, C. E.; Driesner, T.; Heinrich, C. A.

2009-12-01

391

Hydrothermal origin of halogens at Home Plate, Gusev Crater  

NASA Astrophysics Data System (ADS)

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.

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

392

Hydrothermal origin of halogens at Home Plate, Gusev Crater  

USGS Publications Warehouse

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.

Schmidt, M. E.; Ruff, S. W.; McCoy, T. J.; Farrand, W. H.; Johnson, J. R.; Gellert, R.; Ming, D. W.; Morris, R. V.; Cabrol, N.; Lewis, K. W.; Schroeder, C.

2008-01-01

393

Hydrothermal flow regime and magmatic heat source of the Cerro Prieto geothermal system, Baja California, Mexico  

SciTech Connect

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.

Elders, W.A.; Bird, D.K.; Schiffman, P.; Williams, A.E.

1984-01-01

394

Hydrothermal alteration in the EPF replacement wells, Olkaria Geothermal field, Kenya  

SciTech Connect

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.

Mungania, J. [Kenya Power & Lighting Co. Ltd., Naivasha (Kenya)

1996-12-31

395

Peptide synthesis in early Earth hydrothermal systems.  

PubMed

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 degrees C with those obtained at more moderate temperatures (160 degrees 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. PMID:19371157

Lemke, Kono H; Rosenbauer, Robert J; Bird, Dennis K

2009-03-01

396

Thermal boundary layer development in dispersed flow film boiling  

E-print Network

Dispersed flow film boiling consists of a dispersion of droplets which are carried over a very hot surface by their vapor. This process occurs in cryogenic equipment and wet steam turbines. It is also of interest in the ...

Hull, Lawrence M.

1982-01-01

397

Effects of surface parameters on boiling heat transfer phenomena  

E-print Network

Nanofluids, engineered colloidal dispersions of nanoparticles in fluid, have been shown to enhance pool and flow boiling CHF. The CHF enhancement was due to nanoparticle deposited on the heater surface, which was verified ...

Truong, Bao H. (Bao Hoai)

2011-01-01

398

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

399

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

400

EAST ELEVATION OF THE ELECTRIC SHOP. BOILING HOUSE AND POWER ...  

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

EAST ELEVATION OF THE ELECTRIC SHOP. BOILING HOUSE AND POWER HOUSE WING IN THE BACKGROUND. VIEW FROM THE SOUTHEAST - Lihue Plantation Company, Sugar Mill Building, Haleko Road, Lihue, Kauai County, HI

401

Boiling of nuclear liquid in core-collapse supernova explosions  

E-print Network

We investigate the possibility of boiling instability of nuclear liquid in the inner core of the proto-neutron star formed in the core collapse of a type II supernova. We derive a simple criterion for boiling to occur. Using this criterion for one of best described equations of state of supernova matter, we find that boiling is quite possible under the conditions realized inside the proto-neutron star. We discuss consequences of this process such as the increase of heat transfer rate and pressure in the boiling region. We expect that taking this effect into account in the conventional neutrino-driven delayed-shock mechanism of type II supernova explosions can increase the explosion energy and reduce the mass of the neutron-star remnant.

Peter Fomin; Dmytro Iakubovskyi; Yuri Shtanov

2007-08-31

402

Dryout droplet distribution and dispersed flow film boiling  

E-print Network

Dispersed flow film boiling is characterized by liquid-phase droplets entrained in a continuous vapor-phase flow. In a previous work at MIT, a model of dispersed flow heat transfer was developed, called the Local Conditions ...

Hill, Wayne S.

1982-01-01

403

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

404

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

405

BOILING HOUSE, SECOND FLOOR, FROM TOP OF GARVER CLARIFIER, MUD ...  

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

BOILING HOUSE, SECOND FLOOR, FROM TOP OF GARVER CLARIFIER, MUD FILTERS AND CAUSTIC SODA TANKS TO THE LEFT. VIEW FROM THE EAST - Kekaha Sugar Company, Sugar Mill Building, 8315 Kekaha Road, Kekaha, Kauai County, HI

406

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

407

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

408

The effects of surface conditions on boiling characteristics  

E-print Network

A unified model relating surface variables to the nucleate pool boiling characteristics was developed. A simple vapor trapping mechanism was postulated and a geometrical model constructed for idealized conical cavities ...

Lorenz, J. J.

1972-01-01

409

Boiling local heat transfer enhancement in minichannels using nanofluids.  

PubMed

This paper reports an experimental study on nanofluid convective boiling heat transfer in parallel rectangular minichannels of 800 ?m 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

Chehade, Ali Ahmad; Gualous, Hasna Louahlia; Le Masson, Stephane; Fardoun, Farouk; Besq, Anthony

2013-01-01

410

Infrared thermometry study of nanofluid pool boiling phenomena  

E-print Network

Abstract 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.%). ...

Gerardi, Craig

411

Determination of pool boiling Critical Heat Flux enhancement in nanofluids  

E-print Network

Nanofluids are engineered colloids composed of nano-size particles dispersed in common fluids such as water or refrigerants. Using an electrically controlled wire heater, pool boiling Critical Heat Flux (CHF) of Alumina ...

Truong, Bao H. (Bao Hoai)

2007-01-01

412

Forced-convection, dispersed-flow film boiling  

E-print Network

This report presents the latest results of an investigation of the characteristics of dispersed flow film boiling. Heat transfer data are presented for vertical upflow of nitrogen in an electrically heated tube, 0.4 in. ...

Hynek, Scott Josef

1969-01-01

413

Pressure drop with surface boiling in small-diameter tubes  

E-print Network

Pressure drop for water flowing in small-diameter tubes under isothermal, nonboiling, and surface-boiling conditions was investigated. Experimental results for local pressure gradient and heattransfer coefficients are ...

Dr?mer, Thomas

1964-01-01

414

Experimental design for study of nucleate boiling in porous structures  

E-print Network

The superheat required to initiate nucleate boiling inside porous wicks is not well understood in practice. This thesis reports the design of an experimental setup for investigating the onset of vapor nucleation in sintered ...

Kelley, Mitchell Joseph

2011-01-01

415

The correlation of nucleate boiling burn-out data  

E-print Network

A dimensionless correlation is developed for nucleate boiling buzrnout data including the following ranges of variables. Fluids - Water Bensene n - Heptane n - Pentane Ethanol Pressure - 0.0045 to 0.96 of critical pressure ...

Griffith, P.

1957-01-01

416

Film Boiling on Downward Quenching Hemisphere of Varying Sizes  

SciTech Connect

Film boiling heat transfer coefficients for a downward-facing hemispherical surface are measured from the quenching tests in DELTA (Downward-boiling Experimental Laminar Transition Apparatus). Two test sections are made of copper to maintain low Biot numbers. The outer diameters of the hemispheres are 120 mm and 294 mm, respectively. The thickness of all the test sections is 30 mm. The effect of diameter on film boiling heat transfer is quantified utilizing results obtained from the test sections. The measured data are compared with the numerical predictions from laminar film boiling analysis. The measured heat transfer coefficients are found to be greater than those predicted by the conventional laminar flow theory on account of the interfacial wavy motion incurred by the Helmholtz instability. Incorporation of the wavy motion model considerably improves the agreement between the experimental and numerical results in terms of heat transfer coefficient. In addition, the interfacial wavy motion and the quenching process are visualized through a digital camera.

Chan S. Kim; Kune Y. Suh; Joy L. Rempe; Fan-Bill Cheung; Sang B. Kim

2004-04-01

417

Burnout in forced convection nucleate boiling of water  

E-print Network

Data are presented for burnout in forced coivection nucleate boiling of water at pressures above 500 psia. A dimensionless correlation is devised for. the M.I.T. data which is found to be valid for certain recent data ...

Reynolds John Mitchell

1957-01-01

418

Visual measurement technique for analysis of nucleate flow boiling  

SciTech Connect

This report provides a record of a visual measurement technique for the analysis of the bubbles formed by nucleate flow boiling. The purpose of measuring these bubbles is to extend the understanding of the boiling process. By studying the behavior of these vapor bubbles, a better understanding of the physics controlling boiling heat transfer will be gained. The boiling of refrigerants is simultaneously filmed with a high speed 16mm camera while heat transfer measurements are taken. These tests are performed over a range of heat fluxes and flow velocities in order to study the effect of these conditions on the bubble dynamics. The analysis of the 16mm films evolved from a manual to a computer assisted system, and finally to a digital image analysis system. The following is an overview of the filming apparatus and the bubble measurement schemes.

Kedzierski, M.A.; Crowder, J.M.; Jacobi, A.M.; Zhang, L.W.

1994-10-01

419

Zinc Oxide Nanowire Forest for Pool Boiling Heat Transfer  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanowire forest is applied for the electronics cooling by means of pool boiling heat transfer. The forest was composed of lengthwise grown backbone and branched nanowires, which were highly dense and tree-like hierarchical structures. The platinum heater and resistance temperature detector were fabricated by microfabrication on one side of silicon chips and nanowire forest was synthesized on the other side. The superheat and heat flux were evaluated at steady state while the voltage in the heater was increased gradually. The heat flux gradually increased linearly with superheat at the initial stage of heating due to convective heat transfer and abruptly increased once the coolant started to boil. It seemed that the nanowire forest played a role of increased bubble nucleation sites with superhydrophilic nature leading to enhancement of boiling heat transfer. This sheds light on application of nanostructured surface as an effective electronics cooling by boiling heat transfer.

Lee, Dongjin; Kim, Taehyun; Park, Sungsik; Lee, Seung Seob; Ko, Seung Hwan

2012-11-01

420

Visualization and measurements of periodic boiling in silicon microchannels  

Microsoft Academic Search

A simultaneous visualization and measurement investigation has been carried out on flow boiling of water in parallel silicon microchannels of trapezoidal cross-section. Two sets of parallel microchannels, having hydraulic diameters of 158.8 and 82.8 ?m, respectively, were used. The visualization study shows that once boiling heat transfer is established, two-phase flow and single-phase liquid flow appear alternatively with time in

H. Y. Wu; Ping Cheng

2003-01-01

421

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

422

Enhancement of nucleate boiling heat transfer using carbon nanotubes  

Microsoft Academic Search

The effect of carbon nanotubes (CNTs) on nucleate boiling heat transfer in R22 and water is investigated with the addition of 1.0vol% of CNTs. Test results showed that CNTs increase boiling heat transfer coefficients of these fluids. Especially, large enhancement up to 28.7% was observed at low heat fluxes of less than 30kW\\/m2. With increasing heat flux, however, the enhancement

Ki-Jung Park; Dongsoo Jung

2007-01-01

423

Nucleate and transition boiling in narrow horizontal spaces  

NASA Astrophysics Data System (ADS)

Nucleate and transition boiling are performed in a horizontal narrow space between a heated upward-facing copper disk and an unheated surface for saturated n-pentane. The heat flux and the wall temperature are determined by mean of an inverse heat conduction method. The influence of the confinement on the boiling curves and the flow patterns are analysed. Characteristic instabilities are observed at low heat flux and during the transition regime.

Stutz, Benoit; Lallemand, Monique; Raimbault, Fabien; Passos, Julio

2009-05-01

424

Pool boiling heat transfer of non-Newtonian nanofluids  

Microsoft Academic Search

This paper reports on the investigation of pool boiling heat transfer of ?-Al2O3\\/CMC non-Newtonian nanofluids. To prepare nanofluids, ?-Al2O3 nanoparticles were dispersed in CMC solution (carboxy methyl cellulose in water) using ultrasonic mixing and mechanical mixer. Different concentrations of CMC non-Newtonian fluids and ?-Al2O3\\/CMC non-Newtonian nanofluids were tested under nucleate pool boiling heat transfer conditions. Experiments were carried out at

S. Soltani; S. Gh. Etemad; J. Thibault

2010-01-01

425

Boiling heat transfer on meshed surfaces of different aperture  

NASA Astrophysics Data System (ADS)

The paper presents the results of investigations of the impact of mesh aperture on boiling heat transfer. The tests have been performed for distilled water and ethyl alcohol at ambient pressure. It was observed that the meshed surfaces performed much better than the smooth reference surface and that meshes of smaller aperture provided better results. The obtained results have been compared with selected models of boiling heat transfer from literature.

Orman, ?ukasz J.

2014-08-01

426

Hydrothermal vent complexes associated with sill intrusionsin sedimentarybasins  

E-print Network

Hydrothermal vent complexes associated with sill intrusionsin sedimentarybasins BJIbRNJAMTVEIT1 sedimentarybasinscause strongthermal perturbations and frequentlycause extensivehydrothermalactivity.Hydrothermal vent Carboniferous-Middle Jurassic Karoo Basin in South Africa. Distinct features include inward-dipping sedimentary

Podladchikov, Yuri

427

A microgravity boiling and convective condensation experiment  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

428

Infrared thermometry study of nanofluid pool boiling phenomena.  

PubMed

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

Gerardi, Craig; Buongiorno, Jacopo; Hu, Lin-Wen; McKrell, Thomas

2011-01-01

429

Film boiling of R-11 on liquid metal surfaces  

SciTech Connect

An interesting problem is the effect of an immiscible liquid heating surface on the process of film boiling. Such surfaces raise questions concerning interface stability to disturbances, effects of gas bubbling, and vapor explosions in layered systems. The specific motivation for this study was to investigate film boiling from a liquid surface with application to cooling of molten reactor core debris by an overlying pool of reactor coolant. To investigate this phenomenon, and apparatus consisting of a nominal six-inch diameter steel vessel to hold the liquid metal and boiling fluid was constructed; coolant reservoirs, heaters, controllers, and allied instrumentation were attached. A transient energy balance was performed on the liquid metal pool by a submerged assembly of microthermocouples in the liquid metal and an array of thermocouples on the wall of the test vessel. The thermocouple data were used to determine the boiling heat flux as well as the boiling superheat. On an average basis, the deviation between the prediction of the Berenson model and the experimental data was less than one percent when Berenson was corrected for thermal radiation effects. Evidence from visualization tests of R-11 in film boiling over molten metal pools to superheats in excess of 600 K supports this conclusion. 13 refs.

Greene, G.A.; Irvine, T.F. Jr.

1986-01-01

430

Pool boiling heat transfer enhancement by perforated plates  

SciTech Connect

Several recent studies have revealed that the boiling heat transfer may be considerably enhanced in a narrow restricted region. Thin liquid film underneath the elongated bubble quickly evaporates, and enhances the heat transfer. In this study, the narrow restricted region was formed by attaching a perforated plate on top of a boiling surface. Through systematic experiments, effects of the hole size, hole pattern, gap width between the perforated plate and the boiling surface were investigated using water or R-113. Results show that perforated plates considerably enhance the boiling of water or R-113. For water, especially, they have outperformed commercial enhanced tubes, which confirms that the possible boiling enhancement mechanism of the perforated plate (thin film evaporation underneath the elongated bubble) is very effective to the boiling of high surface tension liquids such as water. Optimum configuration was found -- 3.0 mm hole diameter, 15 mm x 15 mm hole pattern, 0.3--0.5 mm gap width for water, and 2.0 mm hole diameter, 3.5 mm x 3.5 mm hole pattern, 0.5 mm gap width for R-113. A correlation which correlates most of the data within {+-}30% was also developed.

Kim, N.H. [Univ. of Inchon (Korea, Republic of). Dept. of Mechanical Engineering

1996-12-31

431

Revisting the boiling of quark nuggets at nonzero chemical potential  

E-print Network

The boiling of possible quark nuggets during the quark-hadron phase transition of the Universe at nonzero chemical potential is revisited within the microscopic Brueckner-Hartree-Fock approach employed for the hadron phase, using two kinds of baryon interactions as fundamental inputs. To describe the deconfined phase of quark matter, we use a recently developed quark mass density-dependent model with a fully self-consistent thermodynamic treatment of confinement. We study the baryon number limit $A_{\\rm boil}$ (above which boiling may be important) with three typical values for the confinement parameter $D$. It is firstly found that the baryon interaction with a softer equation of state for the hadron phase would only lead to a small increase of $A_{\\rm boil}$. However, results depend sensitively on the confinement parameter in the quark model. Specifically, boiling might be important during the Universe cooling for a limited parameter range around $D^{1/2} = 170$ MeV, a value satisfying recent lattice QCD calculations of the vacuum chiral condensate, while for other choices of this parameter, boiling might not happen and cosmological quark nuggets of $10^2 < A < 10^{50}$ could survive.

Ang Li; Tong Liu; Philipp Gubler; Ren-Xin Xu

2013-12-13

432

Infrared thermometry study of nanofluid pool boiling phenomena  

NASA Astrophysics Data System (ADS)

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.

Gerardi, Craig; Buongiorno, Jacopo; Hu, Lin-Wen; McKrell, Thomas

2011-12-01

433

Infrared thermometry study of nanofluid pool boiling phenomena  

PubMed Central

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

2011-01-01

434

Experimental study of surfactant effects on pool boiling heat transfer  

SciTech Connect

In the first part of this work, nucleate boiling of aqueous solutions of sodium lauryl sulfate (SLS) over relatively wide ranges of concentration and heat flux was carried out in a pool boiling apparatus. The experimental results show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient h considerably higher, and that there is an optimum additive concentration for higher heat fluxes. Beyond this optimum point, further increase in additive concentration makes h lower. In the second part of this work, nucleate boiling heat transfer rate for n-propanol-water binary mixtures with various amounts of sodium lauryl sulfate were measured in the same pool boiling apparatus. The importance of the mass diffusion effect, which is caused by preferential evaporation of the more volatile component at the vapor-liquid interface on the boiling of the binary mixture, has been confirmed. However, it is shown that the effect exerted by the addition of a surfactant dominates over the mass diffusion effect in dilute binary mixtures.

Ying Liang Tzan; Yu Min Yang (National Cheng Kung Univ., Tainan (Taiwan))

1990-02-01

435

Characterization of advanced preprocessed materials (Hydrothermal)  

SciTech Connect

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.

Rachel Emerson; Garold Gresham

2012-09-01

436

The BGU/CERN solar hydrothermal reactor  

E-print Network

We describe a novel solar hydrothermal reactor (SHR) under development by Ben Gurion University (BGU) and the European Organization for Nuclear Research CERN. We describe in broad terms the several novel aspects of the device and, by extension, of the niche it occupies: in particular, enabling direct off-grid conversion of a range of organic feedstocks to sterile useable (solid, liquid) fuels, nutrients, products using only solar energy and water. We then provide a brief description of the high temperature high efficiency panels that provide process heat to the hydrothermal reactor, and review the basics of hydrothermal processes and conversion taking place in this. We conclude with a description of a simulation of the pilot system that will begin operation later this year.

Bertolucci, Sergio; Caspers, Fritz; Garb, Yaakov; Gross, Amit; Pauletta, Stefano

2014-01-01

437

Hydrothermal Ni Prospectivity Analysis of Tasmania, Australia  

NASA Astrophysics Data System (ADS)

Tasmania contains the largest hydrothermal Ni deposit in Australia: Avebury (118,000 Ni metal tonnes). This Devonian deposit was discovered in 1998 in the Dundas geological region, and consists of a system of hydrothermal Ni ore bodies. They are hosted by an intensely altered and serpentinized Cambrian ultramafic suite in close proximity to major structural features. The mineralization is considered to be the result of hydrothermal scavenging and remobilization of the original nickel content of mafic/ultramafic rocks in the area, and subsequent re-deposition in favourable structural traps. This is based on the low sulphur, low Cu and Platinum element content of the mineralization. The mineralization is spatially (at the edge) and temporally related to a large granitic intrusion, the Heemskirk Granite, which is considered to be the source of the hydrothermal fluids as well as the necessary thermal gradients for the circulation of the fluids. Tasmania is largely covered by the Jurassic Ferrar continental flood basalt province in the East and constrains a number of early Cambrian ultramafic-mafic complexes in the West. The Ferrar large igneous province (LIP) extends over to Antarctica and is temporally and genetically related to the Karoo igneous province in southern Africa that comprises tholeiitic lava flows, sills, and dyke swarms. The Ferrar and Karoo igneous provinces were associated with the same thermal anomaly that was responsible for the break up of eastern Gondwana at ca 180 Ma. Despite of timeframe differences between the Avebury Ni deposits and the Ferrar LIP emplacement, similar geological settings to the Avebury could be duplicated along the Ferrar LIP. The presence of mafic/ultramafic rocks in favourable lithological packages and/or structural traps along the margins of the province indicate that this LIP could represent a possible exploration target for Ni hydrothermal deposits. Based on this background, a prospectivity analysis for hydrothermal Ni deposits was carried out on a regional scale for the entire state of Tasmania to explore the prospectivity of for hydrothermal Ni deposits of this part of the Ferrar LIP for. A conceptual model of hydrothermal nickel mineral systems was used to identify the following as the most important exploration criteria for hydrothermal nickel deposits: (i) presence of potential nickel sources, (ii) heat and fluid sources, (iii) permeable transportation channels for circulating hydrothermal fluids, and (iv) prospective lithological and structural traps conducive for sulphur saturation and deposition of nickel sulphides. Available public domain exploration datasets were processed using GIS functionalities to derive a series of derivative GIS layers that could be used as proxies for each of the above exploration criteria. These included mafic-ultramafic rocks formed from magma with >7% MgO, large igneous province; major faults, and mineral alteration assemblages that could indicate redox gradients and/or reduced fluids highly concentrated in chloride etc. A two-pronged approach involving GIS-assisted manual prospectivity analysis and GIS-based (automated) prospectivity analysis was used for identifying the most prospective ground for hydrothermal nickel deposits in Tasmania. The manual analysis involved a conceptual review of all geological regions of the state, while the GIS-based automated approach used a spatial fuzzy model. The results of the two analyses were subsequently integrated and, after a detailed geological follow-up study, were used to generate a hydrothermal nickel prospectivity map of the state. The methodology developed in this study could be potentially applied to frontier exploration grounds with similar geological setting, such as Papua New Guinea.

Gonzalez-Alvarez, I.; Porwal, A.; McCuaig, T. C.; Maier, W.

2009-04-01

438

Hydrothermal Ni Prospectivity Analysis of Tasmania, Australia  

NASA Astrophysics Data System (ADS)

Tasmania contains the largest hydrothermal Ni deposit in Australia: Avebury (118,000 Ni metal