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1

Axial Distribution of Void Fraction in Subcooled Boiling.  

National Technical Information Service (NTIS)

A theoretical approach to the axial distribution of liquid temperature, vapor quality, and void fraction in subcooled boiling is presented. The model is based on the temperature distribution of the thermal boundary layer which can be considered as a measu...

L. Maroti

1975-01-01

2

Bubble behavior and mean diameter in subcooled flow boiling  

SciTech Connect

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

Zeitoun, O. [Alexandria Univ. (Egypt); Shoukri, M. [McMaster Univ., Hamilton (Canada)

1996-02-01

3

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

Microsoft Academic Search

The critical heat fluxes (CHFs) of subcooled water flow boiling for the test tube inner diameters (d=3 and 6mm) and the heated lengths (L=67, 120 and 150mm) are systematically measured for the flow velocities (u=4.0 to 13.3m\\/s), the inlet subcoolings (DeltaTsub, in=48 to 148K), the outlet subcoolings (DeltaTsub, out=10.5 to 95.1K), the inlet pressure (Pin=753 to 995kPa) and the outlet

Koichi Hata; Hirokazu Komori; Masahiro Shiotsu; Nobuaki Noda

2004-01-01

4

Prediction of critical heat flux for subcooled flow boiling  

Microsoft Academic Search

A theoretical critical heat flux (CHF) prediction model is developed for the subcooled flow boiling based on the liquid sublayer dryout mechanism. The model is tested over a large data bank (about 2482 points), which is characterized by covering almost the entire physics scope, showing a general good accuracy. Parametric trends of the CHF in terms of mass flux, pressure,

W. Liu; H. Nariai; F. Inasaka

2000-01-01

5

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

6

Stabilization of freon 113 subcooled boiling in forced convection  

SciTech Connect

A simple electronic feedback system allowing to perform tests in subcooled boiling of Freon 113 in the transition region, where systems directly heated by Joule effect are unstable, is presented. A short, electrically heated tube is used where the current is controlled by the measure of the wall temperature. First experiments highlight a hysteresis phenomenon depending on whether the temperature difference between the wall and the boiling liquid is increased or decreased, and the influence of surface conditions on the shape of the boiling curve.

Gentile, D.; Benejean, R.; Llory, M.

1985-09-01

7

Variation of Film Boiling Modes in He II from Strongly to Weakly Subcooled States  

SciTech Connect

Film boiling modes in both subcooled and saturated superfluid helium (He II) were experimentally investigated. The visual observation and the transient pressure and temperature measurements were performed to extract some characteristics of each boiling mode. The classification of all four film boiling modes, strongly subcooled and weakly subcooled modes in subcooled He II (He IIp) and noisy and silent film boiling modes in saturated He II (He IIs), was drawn on the boiling mode map. It was found from the heater temperature measurement that the boiling heat transfer is enhanced in the weakly subcooled mode compared with in the strongly subcooled mode. In the weakly subcooled mode, the vapor behavior is much activated by the instability in vapor-liquid interface. The boundary region between the strongly and the weakly subcooled modes becomes thick as the rise of He II temperature or the increase of the heat flux. The noisy film boiling does not occur at the pressure above 9 kPa, though it appears at the pressure above p{lambda}. It is found that in the region adjacent to the lambda line He I film boiling mode occurs even in He II.

Nozawa, M.; Murakami, M.; Takada, S. [Graduate School of Systems and Information Engineering, University of Tsukuba, Tennodai 1-1-1, Tsukuba, 305-8573 (Japan); Kimura, N. [Cryogenics Science Center, Applied Research Laboratory, High Energy Accelerator Research Organization, Oho 1-1, Tsukuba, 305-0801 (Japan)

2006-04-27

8

Prediction of the critical heat flux in water subcooled flow boiling using a new mechanistic approach  

Microsoft Academic Search

A thorough examination of the results of existing models based on the liquid sublayer dryout theory suggested the need to postulate a new mechanism to predict the CHF in subcooled water flow boiling. Considering that we have local boiling with bulk subcooled conditions, there will be a distance from the wall at which the fluid temperature is equal to the

G. P. Celata; M. Cumo; Y. Katto; A. Mariani

1999-01-01

9

Subcooled pool boiling on thin wire in microgravity  

NASA Astrophysics Data System (ADS)

A new set of experimental data of subcooled pool boiling on a thin wire in microgravity aboard the 22nd Chinese recoverable satellite is reported in the present paper. The temperature-controlled heating method is used. The results of the experiments in normal gravity before and after the flight experiment are also presented, and compared with those in microgravity. The working fluid is degassed R113 at 0.1 MPa and subcooled by 26C nominally. A thin platinum wire of 60?m in diameter and 30 mm in length is simultaneously used as heater and thermometer. It is found that the heat transfer of nucleate pool boiling is slightly enhanced in microgravity comparing with those in normal gravity. It is also found that the correlation of Lienhard and Dhir can predict the CHF with good agreement, although the range of the dimensionless radius is extended by three or more decades above the originally set limit. Three critical bubble diameters are observed in microgravity, which divide the observed vapor bubbles into four regimes with different sizes. Considering the Marangoni effect, a qualitative model is proposed to reveal the mechanism underlying the bubble departure processes, and a quantitative agreement can also be acquired.

Zhao, J. F.; Wan, S. X.; Liu, G.; Yan, N.; Hu, W. R.

2009-01-01

10

Heat Transfer Coefficient Measurement Study of Several Film Boiling Modes in Subcooled He II  

SciTech Connect

This study was carried out for more detailed information about film boiling heat transfer in subcooled superfluid helium (He II). A number of film boiling modes were experimentally investigated in a wide range of the pressure from the atmospheric pressure down to the saturated vapor pressure. A thin stainless steel foil heater was used to cause film boiling and as a temperature sensor to measure the heater surface temperature. The results drawn from the heat transfer coefficient measurement give a support to the previous conclusion reached by visualization and pressure measurement studies that two film boiling modes appear in subcooled He II, that is the strongly subcooled film boiling mode and the weakly subcooled film boiling mode. It is, however, found that the dependence of the heat transfer coefficient on pressure was much different from those of conventional fluids. The heat transfer coefficient weakly decrease with the pressure in the weakly subcooled film boiling, and on the other hand it is almost independent of the pressure in the strongly film boiling. The peak of heat transfer coefficient appears at about 8 kPa in the transition region between the weakly subcooled and the noisy film boiling modes.

Takada, S.; Murakami, M.; Nozawa, M. [Graduate School of Systems and Information Engineering, University of Tsukuba, Tennodai 1-1-1, Tsukuba 305-8573 (Japan); Kimura, N. [Cryogenics Science Center, Applied Research Laboratory, High energy Accelerator Research Organization, Oho 1-1, Tsukuba 305-0801 (Japan)

2006-04-27

11

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

Microsoft Academic Search

A phenomenological model of critical heat flux (CHF) applicable to both pool boiling and subcooled forced convection boiling is developed using the dry-spot model proposed recently and existing correlations for active site density, bubble departure diameter and heat transfer coefficient in nucleate boiling. For the active nucleation site density Kocamustafaogullari and Ishiis model is used including the concept of a

Sang Jun Ha; Hee Cheon No

2000-01-01

12

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

13

Geometry effects on critical heat flux for subcooled convective boiling from an array of heated elements  

Microsoft Academic Search

The critical heat flux (CHF) condition was experimentally determined for subcooled flow boiling from an array of simulated microelectronic devices on one wall of a vertical rectangular passage. A test apparatus was used in these experiments that allowed visual observation of the boiling process while simultaneously measuring the heat flux and surface temperature for ten heat-dissipating elements. Using R-113 as

W. R. McGillis; V. P. Carey; B. D. Strom

1991-01-01

14

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

15

Experimental and theoretical investigation of adiabatic bubbly flow and subcooled boiling flow in an annulus  

NASA Astrophysics Data System (ADS)

The two-fluid model is the most advanced thermal hydraulic model for the analysis of nuclear reactor systems. One of the closure relations for this model is the interfacial area transport equation. Subcooled boiling is of considerable interest to boiling water reactor safety. A robust mechanistic model does not exist yet for subcooled boiling. To develop a mechanistical constitutive relation for the subcooled boiling condition, a better understanding of the physical phenomenon and a solid, extensive database are essential. This thesis focuses on experimental and theoretical investigations on adiabatic bubbly flow and subcooled boiling flow in a BWR-scaled annular flow channel. A database of flow parameters and data sets of the liquid velocity are established for the adiabatic bubbly flow. Databases of flow parameters and boundary parameters, such as active nucleation site density, bubble lift-off diameter, and bubble lift-off frequency, are also obtained for subcooled convective boiling in the annular test section. The one-dimensional, one-group interfacial area transport equation is evaluated based on the experimental data in the adiabatic bubbly flow. The correlation of distribution parameter, drift velocity, and Sauter mean diameter are evaluated from data in both adiabatic bubbly flow and subcooled boiling flow. A bubble-layer thickness model is proposed to avoid various covariances in the cross-sectional area averaged interfacial area transport equation in the subcooled boiling flow. The newly-developed model can predict the bubble-layer thickness as well as the void fraction profile by assuming a square void peak in the bubble-layer region. In addition, the constitutive equation for the distribution parameter in the drift-flux model for boiling flow of an internally heated annulus is also developed based from the measured data. A constitutive relation for the bubble lift-off size is developed based on a force balance and turbulence analysis. The comparisons between the constitutive relation and the experimental data show good agreements. In addition, a preliminary constitutive relation of the bubble lift-off frequency is also obtained. The achievements will be used for the development of the interfacial area transport equation. This will provide a true, mechanistic model of the transfer mechanisms in subcooled convective boiling.

Situ, Rong

16

Liquid-solid contact during flow film boiling of subcooled freon-11  

Microsoft Academic Search

Liquid-solid contacts were measured for flow film boiling of subcooled Freon-11 over an electrically heated cylinder equipped with a surface microthermocouple probe. No systematic variation of the extent of liquid-solid contact with wall superheat, liquid subcooling, or velocity was detected. Only random small-scale contacts that contribute negligibly to overall heat transfer were detected when the surface was above the homogenous

K. H. Chang; L. C. Witte

1990-01-01

17

Nucleate pool boiling in subcooled liquid under microgravity: Results of TEXUS experimental investigations  

NASA Astrophysics Data System (ADS)

Experiments on subcooled nucleate pool boiling in microgravity were carried out to separate gravity driven effects on heat transfer within the boiling process. A ballistic trajectory by sounding rocket flight (TEXUS 5 and 10) achieved a gravity level of a/g = 0.0001 for 360 sec. For determination of geometrical effects on heat transport two different experimental configurations (platinum wire and flat plate) were employed. Boiling curves and bubble dynamics recorded by cinematography lead to gravity independent modelling of the boiling phenomena. The results ensure the applicability and high efficiency of nucleate pool boiling for heat exchangers in space laboratories.

Zell, M.; Straub, J.; Weinzierl, A.

1984-12-01

18

Liquid-solid contact during flow film boiling of subcooled freon-11  

SciTech Connect

Liquid-solid contacts were measured for flow film boiling of subcooled Freon-11 over an electrically heated cylinder equipped with a surface microthermocouple probe. No systematic variation of the extent of liquid-solid contact with wall superheat, liquid subcooling, or velocity was detected. Only random small-scale contacts that contribute negligibly to overall heat transfer were detected when the surface was above the homogenous nucleation temperature of the Freon-11. When large-scale contacts were detected, they led to an unexpected intermediate transition from local film boiling to local transition boiling. An explanation is proposed for these unexpected transitions. A comparison of analytical results that used experimentally determined liquid-solid contact parameters to experimental heat fluxes did not show good agreement. It was concluded that the available model for heat transfer accounting for liquid-solid contact is not adequate for flow film boiling.

Chang, K.H.; Witte, L.C. (Univ. of Houston, TX (United States))

1990-05-01

19

Experimental investigation on drift-flux parameters for subcooled boiling in a vertical annulus  

Microsoft Academic Search

Drift-flux parameters were determined by direct measurements of distributions of local void fraction, vapor velocity and liquid velocity for the subcooled boiling of water in a vertical annulus with a heated inner tube at its center. Using the measured profiles, the drift-flux parameters were calculated based on the definitons, and then compared with those predicted by the existing correlations. The

G. C. Park

2001-01-01

20

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

Microsoft Academic Search

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

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

2006-01-01

21

Local nucleation propagation on heat transfer uniformity during subcooled convective boiling  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

22

Mathematical modelling of mixed salt precipitation during convective heat transfer and sub-cooled flow boiling  

Microsoft Academic Search

The main purpose of this investigation was to study the mechanisms of mixed salt crystallisation fouling on heat transfer surfaces during convective heat transfer and sub-cooled flow boiling conditions. In the present investigation, the effects of various operating parameters such as solution composition and hydrodynamics of the system, on crystallisation fouling of mixtures of calcium sulphate and calcium carbonate have

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

2005-01-01

23

Flow Structure of Subcooled Boiling Water Flow in a Subchannel of 3 3 Rod Bundles  

Microsoft Academic Search

In this paper, the interfacial flow structure of subcooled water boiling flow in a subchannel of 3 3 rod bundles is presented. The 9 rods are positioned in a quadrangular assembly with a rod diameter of 8.2mm and a pitch distance of 16.6 mm. Local void fraction, interfacial area concentration, interfacial velocity, Sauter mean diameter, and liquid velocity have

Byong-Jo YUN; Goon-Cherl PARK; J. Enrique JULIA; Takashi HIBIKI

2008-01-01

24

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

25

An experimental investigation of transition boiling in subcooled Freon-113 forced flow  

SciTech Connect

An experimental study of subcooled boiling in a Freon-113 forced flow is presented. The test section is a short tube (length 50 mm, inner diameter 8 mm, and wall thickness 0.3 mm) heated by the Joule effect. Wall temperature profiles along the tube are presented for different operating points and discussed in terms of the upstream propagation of a temperature front separating regions of nucleate and film boiling. This study emphasizes the effect of axial heat conduction on the boiling processes.

Passos, J.C. (Univ. Federal do Rio de Janeiro (Brazil)); Gentile, D. (Ecole Nationale Superieure de Techniques, Palaiseau (France))

1991-05-01

26

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

Microsoft Academic Search

The subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3m\\/s), the inlet subcoolings (DeltaTsub, in=130 to 161K), the inlet pressure (Pin=812 to 1315kPa), the dissolved oxygen concentration (O2=5.88 and 7.34ppm) and the increasing heat input (Q0exp(t\\/tau), tau=38.1ms to 8.3s) are systematically measured by the experimental water loop installed the pressurizer. The SUS304 tube of test

Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

2006-01-01

27

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

Microsoft Academic Search

The steady state subcooled flow boiling critical heat flux (CHF) for the flow velocities (u=4.0 to 13.3 m\\/s), the inlet subcoolings (DeltaTsub,in=48.6 to 154.7 K), the inlet pressure (Pin=735.2 to 969.0 kPa) and the increasing heat input (Q0 exp(t\\/tau), tau=10, 20 and 33.3 s) are systematically measured with the experimental water loop. The 304 Stainless Steel (SUS304) test tube of

Koichi Hata; Masahiro Shiotsu; Nobuaki Noda

2007-01-01

28

The Characteristics of Steam Bubbles in Subcooled Boiling Flow  

SciTech Connect

In two-fluid modeling and three-fluid modeling, the accurate prediction of the interfacial area concentration, interfacial heat transfer and interfacial shear stress, were required. In this works, the axial profiles of void fraction, interfacial area concentration and interfacial heat transfer coefficient along the flow direction could be measured. For the steam bubbles whose diameter were less than 8 mm, the interfacial area concentration and the mean bubble diameter had a correlation with void fraction despite the variation of liquid flow rate and subcooling. In case the steam bubble collapse occurred due to an irregular bubble condensation and a turbulence of liquid flow, interfacial heat transfer coefficient with the bubble collapse was about twice of that without a bubble collapse. And the interfacial heat transfer coefficient without bubble collapse showed a good agreement with the correlation proposed by Akiyama. In addition, the supposed image processing method could be applied to the present experimental condition. (authors)

Takatoshi Takemoto; Asi Bunyajitradulya [Chulalongkom University, 254 Phyathai Road, Patumwan, Bangkok 10330 (Thailand); Mitsuo Matsuzaki; Hiroshige Kikura; Masanori Aritomi [Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152 (Japan)

2002-07-01

29

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

30

Modeling of low-pressure subcooled boiling flow of water via the homogeneous MUSIG approach  

Microsoft Academic Search

Applying a three-dimensional two-fluid model coupled with homogeneous multiple size group (MUSIG) approach, numerical simulations of upward subcooled boiling flow of water at low pressure were performed on the computational fluid dynamics (CFD) code CFX-10 with user defined FORTRAN program. A modified bubble departure diameter correlation based on the Unal's semi-mechanistic model and the empirical correlation of Tolubinski and Kostanchuk

Erfeng Chen; Yanzhong Li; Xianghua Cheng; Lei Wang

2009-01-01

31

Numerical simulation of subcooled boiling water at low pressure incorporating homogeneous MUSIG model  

Microsoft Academic Search

Applying a three-dimensional two-fluid model coupled with homogeneous MUSIG approach, numerical simulations of subcooled water at low pressure were performed on the computational fluid dynamics code CFX-10 with user defined FORTRAN program. A modified bubble departure diameter correlation based on the Unal semi-mechanism model was developed. The water boiling flow experiments at low pressure in vertical concentric annulus from reference

E. F. Chen; Y. Z. Li; X. H. Cheng; Lei Wang

2010-01-01

32

The prediction of the critical heat flux in water-subcooled flow boiling  

Microsoft Academic Search

The prediction of water-subcooled flow boiling critical heat flux (CHF) in peripherally non-uniform heated tubes with or without swirl flow promoters is accomplished using a model based on the liquid sublayer dryout mechanism recently proposed by the authors. Peripheral nonuniform heating and\\/or twisted-tape inserts are properly and simply accounted for in the model, originally developed for uniform heating and straight

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

1995-01-01

33

Void Fraction Measurement in Subcooled-Boiling Flow Using High-Frame-Rate Neutron Radiography  

SciTech Connect

A high-frame-rate neutron radiography (NR) technique was applied to measure the void fraction distribution in forced-convective subcooled-boiling flow. The focus was experimental technique and error estimation of the high-frame-rate NR. The results of void fraction measurement in the boiling flow were described. Measurement errors on instantaneous and time-averaged void fractions were evaluated experimentally and analytically. Measurement errors were within 18 and 2% for instantaneous void fraction (measurement time is 0.89 ms), and time-averaged void fraction, respectively. The void fraction distribution of subcooled boiling was measured using atmospheric-pressure water in rectangular channels with channel width 30 mm, heated length 100 mm, channel gap 3 and 5 mm, inlet water subcooling from 10 to 30 K, and mass velocity ranging from 240 to 2000 kg/(m{sup 2}.s). One side of the channel was heated homogeneously. Instantaneous void fraction and time-averaged void fraction distribution were measured parametrically. The effects of flow parameters on void fraction were investigated.

Kureta, Masatoshi [Japan Atomic Energy Research Institute (Japan); Akimoto, Hajime [Japan Atomic Energy Research Institute (Japan); Hibiki, Takashi [Kyoto University Research Reactor Institute (Japan); Mishima, Kaichiro [Kyoto University Research Reactor Institute (Japan)

2001-11-15

34

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

35

Bubble Behavior in Subcooled Pool Boiling of Water under Reduced Gravity  

NASA Astrophysics Data System (ADS)

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

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

2003-01-01

36

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

NASA Astrophysics Data System (ADS)

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

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

1994-01-01

37

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

38

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

SciTech Connect

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

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

1995-07-01

39

Heating surface materials 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

40

CRITICAL HEAT FLUX IN SUBCOOLED FLOW BOILING - AN ASSESSMENT OF CURRENT UNDERSTANDING AND FUTURE DIRECTIONS FOR RESEARCH  

Microsoft Academic Search

Critical Heat Flux, or CHF, is an important condition that defines the upper limit of safe operation of heat transfer equipment employing boiling heat transfer in heat flux controlled systems. Although significant research has been conducted in this field, a clear understanding of the basic mechanisms leading to the CHF condition is still lacking. The present article covers the subcooled

S. G. Kandlikar

41

Modeling and experiments for wall heat flux partitioning during subcooled flow boiling of water at low pressures  

Microsoft Academic Search

Void fraction during subcooled flow boiling depends on the amount of vapor generated at the wall and condensation in the bulk. Partitioning of heat flux at the wall is required to determine the fraction of the energy that is utilized for vapor production. The wall heat flux models currently available in the literature were developed for high-pressure applications and have

Nilanjana Basu

2003-01-01

42

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

NASA Astrophysics Data System (ADS)

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

Le Corre, Jean-Marie

43

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

44

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

SciTech Connect

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

V.K. Dhir

2003-04-28

45

Effects of heater surface orientation on the critical heat fluxI. An experimental evaluation of models for subcooled pool boiling  

Microsoft Academic Search

An experimental study of boiling at high heat fluxes in low-velocity subcooled forced convection boiling is presented, demonstrating the effects of subcooling and buoyancy orientation on the critical heat flux (CHF) and the bubble residence time. At the low velocity of 0.04 m s?1 used, the flow forces acting on the vapor are insignificant compared with buoyancy and the CHF

Herman Merte; Robert B. Keller; Brian J. Kirby

1997-01-01

46

Implementation of a Two-Phase Boiling Model into the RELAP5/MOD2 Computer Code to Predict Void Distribution in Low-Pressure Subcooled Boiling Flows  

SciTech Connect

This paper demonstrates that the empirical models developed for subcooled flow boiling in RELAP5/MOD2 at high pressures are not valid for applications at low pressures. Modifications carried out in RELAP5/MOD2 to include better correlations of the interphase heat transfer and mean bubble diameter, and the wall heat flux partition model are shown to yield substantial improvements in the predictions of the axial void fraction distribution. When compared against experimental data covering a wide range of heat fluxes and flow rates, predicted axial void fraction profiles follow closely the measured data. Predictions made by the default subcooled boiling model show, however, an unacceptable margin of error with the experimental data.

Yeoh, G.H.; Tu, J.Y. [Australian Nuclear Science Technology Organisation (Australia)

2002-02-15

47

A study of subcooled pool boiling of water: contact area of boiling bubbles with a heating surface during a heating process.  

PubMed

The contact area of bubbles with a transparent heating surface was optically measured during subcooled pool boiling of water on the ground. In the experiments, boiling bubbles were attached to the heating surface with a bubble holder and nearly reproduced the bubble behavior observed in low gravity. DC power was applied to the ITO heater and increased until the heater surface burned out. In quick heating, that is about 20 second until burnout and equal to the heating time during the low gravity period, the contact area was smaller than that for long time heating at the same heat flux. The experimental results suggest the reason why the critical heat flux in pool boiling is higher than the widely accepted predictions in microgravity. In a drop shaft experiment with constant heating, the contact area increased dramatically at the start of microgravity and became constant. Boiling bubbles coalesced and remained just over the heating surface. PMID:15644360

Suzuki, Koichi; Takahashi, Saika; Ohta, Haruhiko

2004-11-01

48

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

49

Effects of ultrasonic vibration on subcooled pool boiling critical heat flux  

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

50

An experimental investigation on the confined and elongated bubbles in subcooled flow boiling in a single microchannel  

NASA Astrophysics Data System (ADS)

The characteristics of the confined bubble and elongated bubble in subcooled flow boiling in a single horizontal rectangular microchannel with hydraulic diameter Dh=1mm are studied experimentally. The channel with 1 1mm cross section is fabricated in a thin copper plate whose confinement number is Co=2.8 and the degassed deionized water is used as the working fluid. Visualization on the confined and elongated bubbles inside the microchannel is carried out by employing a high-speed CCD camera with a microlens. The recorded images are carefully analyzed to illustrate the behaviors of the confinement and elongation processes of the bubble. The boiling number is used as an adjustable parameter to regulate the operating conditions which is eventually found to take a vital role in the bubble elongation process. Two formation patterns of the confined and elongated bubble are identified and the interactions between the neighboring confined and elongated bubbles are elucidated.

Yin, Liaofei; Jia, Li; Guan, Peng; Liu, Fuhao

2012-12-01

51

Numerical Simulation of Subcooled Boiling Inside High-Heat-Flux Component with Swirl Tube in Neutral Beam Injection System  

NASA Astrophysics Data System (ADS)

In order to realize steady-state operation of the neutral beam injection (NBI) system with high beam energy, an accurate thermal analysis and a prediction about working conditions of heat-removal structures inside high-heat-flux (HHF) components in the system are key issues. In this paper, taking the HHF ion dump with swirl tubes in NBI system as an example, an accurate thermal dynamic simulation method based on computational fluid dynamics (CFD) and the finite volume method is presented to predict performance of the HHF component. In this simulation method, the Eulerian multiphase method together with some empirical corrections about the inter-phase transfer model and the wall heat flux partitioning model are considered to describe the subcooled boiling. The reliability of the proposed method is validated by an experimental example with subcooled boiling inside swirl tube. The proposed method provides an important tool for the refined thermal and flow dynamic analysis of HHF components, and can be extended to study the thermal design of other complex HHF engineering structures in a straightforward way. The simulation results also verify that the swirl tube is a promising heat removing structure for the HHF components of the NBI system.

Tao, Ling; Hu, Chundong; Xie, Yuanlai

2014-05-01

52

An experimental study of subcooled film boiling on a vertical surface - Hydrodynamic aspects  

Microsoft Academic Search

The aim of the present study is: (1) To determine the physical characteristics of the interfacial waves for different wall superheats and liquid subcoolings. (2) To determine the velocity field adjacent to the interface at different locations along the interface. Interface and liquid velocities near the leading edge of a vertical wall 6.3 cm wide and 10.3 cm high were

R. Vijaykumar; V. K. Dhir

1992-01-01

53

Simulation of void fraction profile evolution in subcooled nucleate boiling flow in a vertical annulus using a bubble-tracking approach  

Microsoft Academic Search

A three-dimensional bubble-tracking model of subcooled nucleate boiling flow in a vertical channel at low-pressure conditions\\u000a is proposed with specific application to the case of boiling in an annulus with a central heating rod. Vapour is distributed\\u000a in the liquid in the form of individually tracked bubbles. The overall behaviour of the liquidvapour system results from\\u000a motion, interaction, coalescence and

Ivo Kljenak; Borut Mavko

2006-01-01

54

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

55

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

SciTech Connect

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

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

2006-10-20

56

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

National Technical Information Service (NTIS)

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 tempera...

J. Kim J. Benton R. Kucner

2000-01-01

57

A general correlation for pool film boiling heat transfer from a horizontal cylinder to subcooled liquid: Part 2 - Experimental data for various liquids and its correlation  

SciTech Connect

Experimental data of pool film boiling heat transfer from horizontal cylinders in various liquids such as water, ethanol, isopropanol, Freon-113, Freon-11, liquid nitrogen, and liquid argon for wide ranges of system pressure, liquid subcooling, surface superheat and cylinder diameter are reported. These experimental data are compared with a rigorous numerical solution and an approximate analytical solution derived from a theoretical model based on laminar boundary layer theory for pool film boiling heat transfer from horizontal cylinders including the effects of liquid subcooling and radiation from the cylinder. A new correlation was developed by slightly modifying the approximate analytical solution to agree better with the experimental data. The values calculated from the correlation agree with the authors data within {plus minus} 10%, and also with other researchers data for various liquids including those with large radiation effects, though these other data were obtained mainly under saturated conditions at atmospheric pressure.

Sakurai, A.; Shiotsu, M.; Hata, K. (Kyoto Univ. (Japan))

1990-05-01

58

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

59

Heat transfer and bubble detachment in subcooled pool boiling from a downward-facing microheater array in a nonuniform electric field.  

PubMed

The effects of a nonuniform electric field on vapor bubble detachment and heat transfer in subcooled pool boiling from a microheater array are investigated. The heater array faced downward to simulate a -1 g gravity condition and to eliminate the dominant masking effect of the buoyancy force. Experiments were conducted at different subcooling levels for various wall temperatures and electric field magnitudes. A dielectric fluid, FC-72, was used as the working fluid at ambient pressure. The array of 3 x 3 independently controlled microheaters was maintained at constant temperature and the rate of heat transfer from each heater was measured. Bubble images were recorded using a high-speed camera. The electric field was applied between the horizontal downward-facing microheater array, which was grounded, and a spherical, off-axis electrode beneath it. Boiling heat transfer results with and without the electric field are presented in this study. In the absence of the nonuniform electric field, compared to the same bulk fluid temperature and wall superheat settings in the +1 g situation, a much larger primary bubble was formed on the heater array, due to the coalescence of the secondary bubbles that nucleated on the heater array. The vapor bubble remained on the heater array surface and no bubble detachment was observed. With the nonuniform electric field applied, bubbles were lifted and sheared off from the heater array surface. The electric field was able to break up the primary bubble into several smaller bubbles--considerably greater heat transfer enhancement was measured than under similar conditions in +1 g. PMID:19426316

Liu, Zan; Herman, Cila; Kim, Jungho

2009-04-01

60

A hydrodynamic model for subcooled liquid jet impingement at the Leidenfrost condition  

Microsoft Academic Search

Stable film boiling occurs in the stagnation region of an impinging subcooled liquid jet during quenching of very hot steel plates. During film boiling the liquid is separated from the surface of the plate by a continuous vapor layer. The minimum surface temperature required to support film boiling is referred to as the Leidenfrost temperature. The present work is devoted

Nitin Karwa; Tatiana Gambaryan-Roisman; Peter Stephan; Cam Tropea

2011-01-01

61

Transient pool boiling in microgravity  

Microsoft Academic Search

Transient nucleate pool boiling experiments using R113 are conducted for short times in microgravity and in earth gravity with different heater surface orientations and subcoolings. The heating surface is a transparent gold film sputtered on a quartz substrate, which simultaneously provides surface temperature measurements and permits viewing of the boiling process from beneath. For the microgravity experiments, which have uniform

J. S. Ervin; H. Merte Jr.; R. B. Keller; K. Kirk

1992-01-01

62

Critical heat flux of water subcooled flow in one-side heated swirl tubes  

Microsoft Academic Search

This paper reports an investigation of the critical heat flux (CHF) in the subcooled flow boiling regime. Hardened copper tube is heated on one side of its external rectangular section like for fusion reactor plasma facing components. It is cooled by a subcooled water flowing in a circular channel equipped with an inserted twisted tape. During experiments, CHF is detected

J. Boscary; J. Fabre; J. Schlosser

1999-01-01

63

Transient pool boiling in microgravity  

NASA Technical Reports Server (NTRS)

Transient nucleate pool boiling experiments using R113 are conducted for short times in microgravity and in earth gravity with different heater surface orientations and subcoolings. The heating surface is a transparent gold film sputtered on a quartz substrate, which simultaneously provides surface temperature measurements and permits viewing of the boiling process from beneath. For the microgravity experiments, which have uniform initial temperatures and no fluid motion, the temperature distribution in the R 113 at the moment of boiling inception is known. High speed cameras with views both across and through the heating surface record the boiling spread across the heater surface, which is classified into six distinct categories.

Ervin, J. S.; Merte, H., Jr.; Keller, R. B.; Kirk, K.

1992-01-01

64

Transient pool boiling in microgravity  

NASA Astrophysics Data System (ADS)

Transient nucleate pool boiling experiments using R113 are conducted for short times in microgravity and in earth gravity with different heater surface orientations and subcoolings. The heating surface is a transparent gold film sputtered on a quartz substrate, which simultaneously provides surface temperature measurements and permits viewing of the boiling process from beneath. For the microgravity experiments, which have uniform initial temperatures and no fluid motion, the temperature distribution in the R 113 at the moment of boiling inception is known. High speed cameras with views both across and through the heating surface record the boiling spread across the heater surface, which is classified into six distinct categories.

Ervin, J. S.; Merte, H., Jr.; Keller, R. B.; Kirk, K.

1992-03-01

65

Integrating artificial neural networks and empirical correlations for the prediction of water-subcooled critical heat flux  

Microsoft Academic Search

The critical heat flux (CHF) is an important parameter for the design of nuclear reactors, heat exchangers and other boiling heat transfer units. Recently, the CHF in water-subcooled flow boiling at high mass flux and subcooling has been thoroughly studied in relation to the cooling of high-heat-flux components in thermonuclear fusion reactors. Due to the specific thermal-hydraulic situation, very few

Alessandro Mazzola

1997-01-01

66

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

67

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

68

Low velocity nucleate flow boiling at various orientations  

Microsoft Academic Search

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

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

1992-01-01

69

Local jet impingement boiling heat transfer with R113  

Microsoft Academic Search

An experimental study was performed to characterize the boiling heat transfer of impinging circular submerged jets on simulated microelectronic chips with a nominal area of 5 mm 5 mm. The heat transfer modes included natural convection, partially developed nucleate boiling, fully developed nucleate boiling and critical heat flux. The study included the effects of jet parameters and fluid subcooling

D. W. Zhou; C. F. Ma

2004-01-01

70

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

71

High heat flux cooling by microbubble emission boiling.  

PubMed

In subcooled flow boiling of water in a horizontal rectangular channel, microbubble emission boiling occurred at higher subcooling of liquid in transition boiling, and the heat flux increased more than the critical heat flux. The maximum heat flux reached 10 MW/m(2) for a channel with 12 mm x 14mm cross-section at 40K liquid subcooling and 0.5 m/sec liquid velocity. For smaller rectangular channels with 14 mm x 5mm, 14mm x 3mm, and 14mm x 1mm cross-sections, the maximum heat flux was 7 MW/m(2)-more than 20 times the cooling limit of a present day CPU. Microbubble emission boiling is expected to realize high heat flux cooling for electronic devices. In convection boiling with subcooled water jet, the same boiling regime and heat flux were obtained for a downward heating surface and an upward heating surface. In subcooled flow boiling with strong convection, the hydrodynamic force is predominant for vapor-liquid exchange. Accordingly, microbubble emission boiling is expected for high heat flux cooling or high heat flux heat transfer in microgravity. PMID:12446336

Suzuki, Koichi; Saitoh, Hiroshi; Matsumoto, Kazuaki

2002-10-01

72

Subseafloor Boiling Within the PACMANUS Hydrothermal System Indicated by Anhydrite-Hosted Fluid Inclusions from ODP Leg 193 Cores  

NASA Astrophysics Data System (ADS)

Drilling during Leg 193 was in an area of active hydrothermal venting from dacitic rocks on Pual Ridge in the Manus Basin. All the cored rocks underlying the fresh surficial volcanic rocks are intensively hydrothermally altered. Primary fluid inclusions preserved in anhydrite veins provide unique fluid samples that provide direct evidence on the chemical and physical properties of hydrothermal fluids present beneath the seafloor. Site 1188 is located on Snowcap Knoll, an area of diffuse warm venting at a water depth of ~1645 m. Fluid inclusions have been studied from a coarse anhydrite +/- pyrite vein from ~123 m below the seafloor. The ambient hydrostatic pressure for this sample is calculated to be ~180 bars. The ambient temperature is unknown, but the T measured after 8 days of thermal rebound at a depth of 360 m in this hole was 313 C. Primary fluid inclusions measuring up to 100 ? m across are dominantly two-phase L + V inclusions, yet fluid inclusions with up to three daughter crystals are also observed. The largest daughter crystal is halite, commonly accompanied by a small transparent granular daughter crystal and an even smaller granular opaque crystal. Consequently, optical inspection alone demonstrates the co-occurrence of both hypersaline, multicomponent brines and less saline aqueous fluids. Ice melting temperatures for L+V inclusions vary from -0.1 to -14.5 C, with a strong mode at -2 C, corresponding to a seawater-like salinity. However, the range in Tm(ice) indicates that a significant number contain quite fresh water, and others contain quite saline water. Ice melting temperatures from the multiphase inclusions, measured in the presence of hydrohalite, range from -29.5 to -39.9 C, confirming their hypersaline composition. These data, as well as measured halite dissolution temperatures ranging from 125 to 257 C, indicate salinities of ~30+/-3 wt.% NaCl equivalent. Most two-phase inclusions homogenize to liquid between 191 C and 351 C. Two very low-salinity inclusions homogenize by critical behavior at 372 C and 385 C. A small subset of inclusions was crushed in oil, whereupon the vapor phase expanded, indicating an internal pressure >1 atm. This indicates the presence of a yet-to-be determined compressible gas component such as CO2 or CH4. During the formation of the anhydrite vein, primary fluid inclusions trapped samples of seawater-like fluid, saline brines, very low-salinity fluid, and mixtures between these three groups. The brines and very low-salinity fluids resulted from fluid phase separation at P>180 bars and T>=380 C.

Vanko, D. A.; Bach, W.; Scott, S. D.; Yeats, C.; Roberts, S.; Beaudoin, Y.

2001-12-01

73

Evaluation of subcooled critical heat flux correlations for tubes with and without internal twisted tapes  

Microsoft Academic Search

Eleven correlations and models for critical heat flux (CHF) of subcooled flow boiling in water were evaluated. Both a direct substitution method (DSM) and a heat balance condition method (HBM) were compared in the evaluations. The HBM was recommended as a better prediction method in the present study. For straight tubes under uniform heating conditions, the correlations of the Gunther,

F. Inasaka; H. Nariai

1996-01-01

74

Control Dewar Subcooler Heat Exchanger Calculations.  

National Technical Information Service (NTIS)

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...

R. Rucinski

1993-01-01

75

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

Microsoft Academic Search

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

C. Liu; T. G. Theofanous

2000-01-01

76

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

Microsoft Academic Search

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

C. Liu; T. G. Theofanous

1994-01-01

77

Control Dewar Subcooler Heat Exchanger Calculations  

SciTech Connect

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 design described in the 'Design Report of the 2 Tesla Superconducting Solenoid for the Fermilab D0 Detector Upgrade' is the final design proposed. A short description of this design follows. The subcooler is constructed of 0.50-inch OD copper tubing with 1.0-inch diameter fins. It has ten and one half spirals at a 11.375-inch centerline diameter to provide 31 feet of tubing length. The liquid helium supply for the solenoid flows through the subcooler and then is expanded through a J-T valve. The subcooler spirals are immersed in the return two phase helium process stream. The return stream is directed over the finned tubing by an annulus created by a 10-inch pipe inside a 12-inch pipe. The transfer line from the refrigerator to the control dewar is constructed such that the liquid helium supply tube is in the refrigerator return stream, thereby subcooling the liquid up to the point where the u-tubes connect the transfer line to the control dewar. The subcooler within the control dewar will remove the heat picked up in the helium supply u-tube/bayonets. The attached subcooler/heat exchanger calculations were done neglecting any subcooling in the transfer line. All heat picked up in the transfer line from the refrigerator storage dewar to the control dewar is absorbed by the supply stream. The subcooler was sized such that the two phase supply fluid is subcooled at 1.7 atm pressure and when expanded through a JT valve to 1.45 atm pressure it is at a saturated liquid state. The calculations apply during steady state operation and at a flow rate of 16 g/s. The analysis of the heat exchanger was broken into two parts relating to the heat transfer mode taking place. The first part is considered the condensing part in which the helium supply stream is changed from two phase fluid to one phase liquid. The second part is the subcooling part where the liquid temperature is lowered, i.e.. subcooled. A summary of the calculations and results appears on the next page. The raw calculations follow the summary.

Rucinski, R.; /Fermilab

1993-10-04

78

1D plane numerical model for boiling liquid expanding vapor explosion (BLEVE)  

Microsoft Academic Search

The depressurization of a vessel containing saturated or subcooled liquid may occur in a variety of industrial processes and often poses a potentially hazardous situation. A 1D plane numerical model was developed for estimating the thermodynamic and the dynamic state of the boiling liquid during a boiling liquid expanding vapor explosion (BLEVE) event. Based on the choice of the initial

G. A. Pinhasi; A. Ullmann; A. Dayan

2007-01-01

79

A Separate-Effect-Based New Appraisal of Convective Boiling and its Suppression  

Microsoft Academic Search

The development of convective boiling heat transfer correlations and analytical models has been based almost exclusively on the knowledge of global heat transfer coefficients, while the predictive capabilities of the correlation constituting components (typically additive convection and boiling) have remained usually elusive. This becomes important when, for example, developing a mechanistic subcooled void model based on wall heat flux partitioning,

Yacine AOUNALLAH

2008-01-01

80

Boiling hysteresis of impinging circular submerged jets with highly wetting liquids  

Microsoft Academic Search

An experimental study was carried out to characterize the boiling hysteresis of impinging circular submerged jets with highly wetting liquids. The effects of noncondensable gases and surface aging on boiling curves were considered. The present study focused on the effects of jet parameters (jet exit velocity, radial distance from the stagnation point and nozzle diameter) and fluid subcooling on incipient

D. W. Zhou; C. F. Ma; J. Yu

2004-01-01

81

Production of Boiling-Stable Granular Resistant Starch by Partial Acid Hydrolysis and Hydrothermal Treatments of High-Amylose Maize Starch  

Microsoft Academic Search

Cereal Chem. 78(6):680-689 The purpose of the present work was to examine whether partial acid hydrolysis (PAH) of a high-amylose maize starch (ae-VII) would enhance the effects of hydrothermal treatments to produce granular resistant starch (RS) that is stable to further heat treatment at atmospheric pres- sure. PAH ae-VII starches were prepared by heating 35% (w\\/v) suspen- sions with 1%

Jorge O. Brumovsky; Donald B. Thompson

2001-01-01

82

Boiling enhancement coating  

US Patent & Trademark Office Database

A coating composition comprising a glue, a particulate material and a solvent, which imparts a surface microstructure to a coated object (29) is disclosed. The particulate material projects above the glue line (28) of the coated object creating the microstructure which provides boiling heat transfer enhancement. A horizontally oriented, rectangular surface immersed in FC-72, indicates up to an 85% decrease in incipient superheat, a 70% to 80% reduction in nucleate boiling superheats, and a .about.109% increase in the critical heat flux (CHF), beyond that of the non-painted surface. The enhanced surface heat transfer coefficients are four to nine times higher than those from the reference surface. The coatings are applicable to electronic component surfaces. A coated silicon test chip tested at subcooled (45.degree. C. conditions using FC-72 had heat dissipation rates of .about.100 W/cm.sup.2 at junction temperatures of .about.85.degree. C., and the highest CHF observed was 159 W/cm.sup.2, 224% higher than that from the untreated chip surface at saturated conditions.

1998-09-29

83

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

NASA Astrophysics Data System (ADS)

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

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

1998-01-01

84

Study of liquid column oscillation and vapour bubble oscillation resulting from film boiling in He  

Microsoft Academic Search

The pressure oscillations during different film boiling modes in He II are studied in this paper. In the sub-cooled film boiling state, a flame-shaped vapour bubble can be seen to be quivering on the planar heater accompanied by a little audible noise, and the pressure oscillation, resulting from both vapour bubble oscillation and liquid column oscillation of bulk He II

P. Zhang; M. Murakami; R. Z. Wang

2001-01-01

85

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

86

The unsteady motion of a long vapour bubble between superheated or subcooled parallel plates  

NASA Astrophysics Data System (ADS)

Motivated by the growth and collapse of a vapour bubble in nucleate boiling this work investigates the unsteady motion of a two-dimensional vapour bubble confined between superheated or subcooled parallel plates whose motion is driven by mass-transfer effects due to evaporation from the liquid to the vapour and condensation from the vapour to the liquid. Unlike in the isothermal problem studied by Bretherton, the thin films attached to the plates are now neither spatially nor temporally uniform and may dry out locally, possibly breaking up into disconnected patches of liquid. Furthermore, there is a complicated nonlinear coupling with a delay character between the profiles of the thin films and the overall expansion or contraction of the bubble which means that the velocity with which the bubble expands or contracts is typically not monotonic. When both plates are superheated the bubble expands, and this expansion may either continue indefinitely or stop in a finite time. When both plates are subcooled the bubble contracts. When one plate is superheated and the other subcooled the bubble may either expand or contract initially, but eventually contracts.

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

1998-11-01

87

Transient Heat Transport in Subcooled He II Associated with JT Effect  

NASA Astrophysics Data System (ADS)

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.

2004-06-01

88

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

89

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 40C) 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

90

Boiling Experiment Facility for Heat Transfer Studies in Microgravity  

NASA Technical Reports Server (NTRS)

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

Delombard, Richard; McQuillen, John; Chao, David

2008-01-01

91

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

92

The Relative Stability of Boiling and Pressurized Light Water Moderated Reactors  

Microsoft Academic Search

This paper compares the stability of a given heterogeneous core when operated with a pressurized or subcooled water cooling system in which the power is removed by boiling. In order to provide a basis for comparison the following assumptions are made: 1) reactor power is the same in both cases, 2) the core geometry is the same in both cases,

John Macphee

1957-01-01

93

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

USGS Publications Warehouse

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

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

2009-01-01

94

Film boiling heat transfer from a sphere in natural and forced convection of freon-113  

SciTech Connect

Boiling heat transfer fluxes were measured on a 3.84-cm hollow copper sphere, in both forced convection and pool boiling, as a function of angular position in Freon 113. This paper reports on forced-convection tests run at speeds of 0.5 to 1.9 m/s. These tests were conducted in the stable film boiling region of the boiling curve. Significant heat transfer rates were measured in the vapor wake region of the sphere for flow film boiling. Video observations of the boiling process revealed that the flow film boiling vapor removal mechanism consisted of periodic formation and detachment of a vapor wake in the rear of the sphere. For pool boiling it was found that the heated surface had a uniform rate of energy dissipation in the stable film boiling regime, whereas in forced convection the film boiling rate was dependent on angular position. Pool film boiling tests also showed multiple humps (more than one maximum heat flux) in the boiling curve when the liquid was subcooled.

Dix, D.; Orozco, J. (Illinois Univ., Chicago, IL (USA))

1990-01-01

95

Boiling driven mixed convection in a L-shaped slab geometry  

NASA Astrophysics Data System (ADS)

The behaviour of a two-phase mixed convection loop with subcooled boiling has been investigated in order to design a passive cooling system. In a test facility with a L-shaped slab geometry subcooled water is pumped into the horizontal lower duct and heated up by the hot bottom plate. Vapour bubbles generated at the heated wall establish a disperse two-phase region with considerable void, measured by a gamma densitometer. The structure and stability of the two-phase mixed convection can be characterised by the Phase Change Number and the Subcooling Number. Operation regimes with flashing induced instabilities in the chimney are indicated in the stability diagram. For the numerical simulation the Eulerian two-fluid-model in the commercial software package CFX4 has been used. The two-fluid-model had to be extended with physical models for bubble generation under subcooled boiling in the lower duct and for water-bubble interfacial forces in the chimney, which have been validated by data of a bubbly flow experiment and of a boiling experiment.

Janssens-Maenhout, G.; Daubner, M.; Knebel, J. U.; Mller, U.

96

Hydrothermal Processing  

SciTech Connect

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

Elliott, Douglas C.

2011-03-11

97

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

98

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

99

On subcooler design for integrated two-temperature supermarket refrigeration system  

Microsoft Academic Search

The energy saving opportunity of supermarket refrigeration systems using subcooler between the medium-temperature (MT) refrigeration system and the low-temperature (LT) refrigeration system has been identified in the previous work. This paper presents a model-based comprehensive analysis on the subcooler design. The optimal subcooling control is discussed as well. With optimal subcooler size and subcooling control, the maximum energy savings of

Liang Yang; Chun-Lu Zhang

2011-01-01

100

Subcooler assembly for SSC single magnet test program  

SciTech Connect

A subcooler assembly has been designed, constructed and installed in the MAGCOOL magnet test area at Brookhaven National Laboratory. Since July 1989, it has been used for testing SSC magnets. This subcooler assembly and cryogenic system are the first of its kind ever built. Today, with more than 5000 hours of operating time, the subcooler has proved to be a reliable unit with individual components meeting design expectations. The lowest temperatures achieved with one SSC dipole are 3.0 K at the suction of the cold vacuum pump and 3.2 K at the return of the magnet. The system performs well in both steady state operation and during magnet quench, subcooling, cooldown and warmup. 4 refs., 7 figs.

Wu, K.C.; Brown, D.P.; Sondericker, J.H.; Farah, Y.; Zantopp, D.; Nicoletti, A.

1991-01-01

101

Method for sub-cooling a normally gaseous hydrocarbon mixture  

Microsoft Academic Search

A method for sub-cooling a normally gaseous hydrocarbon product stream is described which comprises: (a) expanding a liquid phase, sub-cooled, built component, normally gaseous, hydrocarbon stream into a low-pressure, adiabatic gas\\/liquid separation zone; (b) recovering a gaseous refrigerant stream containing portions of a least two of the lightest components of the multi-component, normally gaseous, hydrocarbon stream from the low-pressure, adiabatic

Durr

1988-01-01

102

Low velocity nucleate flow boiling at various orientations  

NASA Astrophysics Data System (ADS)

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.

103

Observational study of pool boiling under microgravity  

NASA Astrophysics Data System (ADS)

Pool boiling experiments under microgravity were conducted, utilizing parabolic flight maneuvers with a CNES Caravelle 6R aircraft. The experimental apparatus taken aboard the aircraft was constructed to enable simultaneous recording, by a video camera, of the side view of vapor bubbles generated on Joule-heated titanium foil immersed in a pool of n-pentane liquid, and the color pattern exhibited by a liquid-crystal layer, which was plated on the backside of the foil. This apparatus successfully recorded observations of behaviors of vapor bubbles, at various liquid subcoolings (7-32 K) and heat fluxes (1.1-42 kW/sq m), and spatial color variation of the crystal layer, possibly reflecting microlayer dynamics beneath the individual bubbles. In spite of the great difference in size and population of the bubbles, between microgravity and terrestrial conditions, no more than a moderate difference was found in overall heat transfer between the two conditions.

Oka, Toshiharu; Abe, Yoshiyuki; Tanaka, Kotaro; Mori, Yasuhiko H.; Nagashima, Akira

1992-05-01

104

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

105

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

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

106

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

107

Critical heat flux of liquid helium (I) in forced convective boiling  

Microsoft Academic Search

For liquid helium (I) flowing through a uniformly heated vertical tube of 1 mm i.d., critical heat flux (CHF) of forced convective boiling has been measured under the conditions of a pressure of 0.199 MPa with vapor-to-liquid density ratio, of 0.409, length-to-diameter ratios from 25 to 200, mass velocities from 11 to 108 kg m⁻²s⁻¹, and inlet subcooling enthalpy from

Y. Katto; S. Yokoya

1984-01-01

108

Nucleate Boiling Heat Transfer Studied Under Reduced-Gravity Conditions  

NASA Technical Reports Server (NTRS)

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

Chao, David F.; Hasan, Mohammad M.

2000-01-01

109

Numerical Analysis of Lead-Bismuth-Water Direct Contact Boiling Heat Transfer  

NASA Astrophysics Data System (ADS)

Direct contact boiling heat transfer of sub-cooled water with lead-bismuth eutectic (Pb-Bi) was investigated for the evaluation of the performance of steam generation in direct contact of feed water with primary Pb-Bi coolant in upper plenum above the core in Pb-Bi-cooled direct contact boiling water fast reactor. An analytical two-fluid model was developed to estimate the heat transfer numerically. Numerical results were compared with experimental ones for verification of the model. The overall volumetric heat transfer coefficient was calculated from heat exchange rate in the chimney. It was confirmed that the calculated results agreed well with the experimental result.

Yamada, Yumi; Takahashi, Minoru

110

Large-scale boiling experiments of the flooded cavity concept for in-vessel core retention  

SciTech Connect

This paper presents results of ex-vessel boiling experiments performed in the CYBL (CYlindrical BoiLing) facility. CYBL is a reactor-scale facility for confirmatory research of the flooded cavity concept for accident management. CYBL has a tank-within-a-tank design; the inner tank simulates the reactor vessel and the outer tank simulates the reactor cavity. Experiments with uniform and edge-peaked heat flux distributions up to 20 W/cm{sup 2} across the vessel bottom were performed. Boiling outside the reactor vessel was found to be subcooled nucleate boiling. The subcooling is mainly due to the gravity head which results from flooding the sides of the reactor vessel. The boiling process exhibits a cyclic pattern with four distinct phases: direct liquid/solid contact, bubble nucleation and growth, coalescence, and vapor mass dispersion (ejection). The results suggest that under prototypic heat load and heat flux distributions, the flooded cavity in a passive pressurized water reactor like the AP-600 should be capable of cooling the reactor pressure vessel in the central region of the lower head that is addressed by these tests.

Chu, T.Y.; Slezak, S.E.; Bentz, J.H. [Sandia National Labs., Albuquerque, NM (United States)] [Sandia National Labs., Albuquerque, NM (United States); Pasedag, W.F. [USDOE, Washington, DC (United States)] [USDOE, Washington, DC (United States)

1994-03-01

111

Stabilization of flow boiling in microchannel heat sinks with a diverging cross-section design  

NASA Astrophysics Data System (ADS)

This paper explores experimentally stabilizing flow boiling water in ten parallel microchannel heat sinks with a diverging cross-section design. Each diverging microchannel has a mean hydraulic diameter of 120 m and a diverging angle of 0.5 while the channel depth is uniform at 76 m. Flow visualization shows that heat flux and mass flux significantly affect the stability of flow boiling in the parallel microchannels. The extent of pressure drop oscillations may be regarded as an index for the onset of flow boiling instability. The stability boundary is plotted on the plane of the subcooling number (Nsub) against the phase change number (Npch) and compared with microchannels with a uniform cross-section design in the literature. The present study confirms that, in terms of stability performance, the flow boiling in the parallel microchannel heat sinks with a diverging cross-section design is superior to a uniform cross-section design.

Lu, Chun Ting; Pan, Chin

2008-07-01

112

Local Heat Transfer and CHF for Subcooled Flow Boiling. 1996 Annual Report.  

National Technical Information Service (NTIS)

For the past decade, efforts have been growing in the development of high heat flux (HHF) components for many applications, including fusion and fission reactor components, advanced electronic components, synchrotrons and optical components, and other adv...

R. D. Boyd

1996-01-01

113

Local Heat Transfer and CHF for Subcooled Flow Boiling - Annual Report 1996  

SciTech Connect

For the past decade, efforts have been growing in the development of high heat flux (HHF) components for many applications, including fusion and fission reactor components, advanced electronic components, synchrotrons and optical components, and other advanced HHF engineering applications. From a thermal prospective, work in the fusion reactor development arena has been underway in a number of areas including: (1) Plasma thermal, and electro-magnetics, and particle transport, (2) Fusion material, rheology, development, and expansion and selection; (3) High heat flux removal; and (4) Energy production and efficiency.

Dr. Ronald D. Boyd

2000-07-01

114

Applying mechanical subcooling to ejector refrigeration cycle for improving the coefficient of performance  

Microsoft Academic Search

This paper describes a new ejector refrigeration system with mechanical subcooling which uses an auxiliary liquidgas ejector to enhance subcooling for the refrigerant from condenser. The new system can have larger subcooling degree when circulating pump consumes a little more power compared with conventional ejector refrigeration system. Based on the built mathematical model, the performance of the new ejector refrigeration

Jianlin Yu; Yunfeng Ren; Hua Chen; Yanzhong Li

2007-01-01

115

The unsteady expansion and contraction of a long two-dimensional vapour bubble between superheated or subcooled parallel plates  

NASA Astrophysics Data System (ADS)

In an attempt to model the growth and collapse of a vapour bubble in nucleate boiling this paper investigates the unsteady expansion and contraction of a long two-dimensional vapour bubble confined between superheated or subcooled parallel plates whose motion is driven by mass-transfer effects due to evaporation from the liquid to the vapour and condensation from the vapour to the liquid. It is shown that in the asymptotic limit of strong surface tension (small capillary number) the solution consists of two capillary-statics regions (in which the bubble interface is semicircular at leading order) and two thin films attached to the plates, connected by appropriate transition regions. This generalization of the steady and isothermal problem addressed by Bretherton (1961) has a number of interesting physical and mathematical features. Unlike in Bretherton's problem, the bubble does not translate but can change in size. Furthermore, the thin films are neither spatially nor temporally uniform and may dry out locally, possibly breaking up into disconnected patches of liquid. Furthermore, there is a complicated nonlinear coupling with a delay character between the profiles of the thin films and the overall expansion or contraction of the bubble which means that the velocity with which the bubble expands or contracts is typically not monotonic. This coupling is investigated for three different combinations of thermal boundary conditions and two simple initial thin-film profiles. It is found that when both plates are superheated equally the bubble always expands, and depending on the details of the initial thin-film profiles, this expansion may either continue indefinitely or stop in a finite time. When both plates are subcooled equally the bubble always contracts, and the length of the thin-film region always approaches zero asymptotically. When one plate is superheated and the other subcooled with equal magnitude the bubble may either expand or contract initially, but eventually the bubble always contracts just as in the pure-condensation case.

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

1999-07-01

116

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

117

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

118

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

119

Evaporation, Boiling and Bubbles  

ERIC Educational Resources Information Center

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

Goodwin, Alan

2012-01-01

120

A simple boiling module  

Microsoft Academic Search

Recent efforts to visually capture the phenomena of boiling have proposed monolithic approaches that extend the basic techniques underlying existing fluid solvers. In this work, we show that if we instead treat boiling as a sep- arate computational module to be loosely coupled to an existing solver, a very easy to implement, highly efficient algorithm can be designed that produces

Theodore Kim; Mark Carlson

2007-01-01

121

Transient nucleate pool boiling in microgravity: Some initial results  

NASA Technical Reports Server (NTRS)

Variable gravity provides an opportunity to test the understanding of phenomena which are considered to depend on buoyancy, such as nucleate pool boiling. The active fundamental research in nucleate boiling has sought to determine the mechanisms or physical processes responsible for its high effectiveness, manifested by the high heat flux levels possible with relatively low temperature differences. Earlier research on nucleate pool boiling at high gravity levels under steady conditions demonstrated quantitatively that the heat transfer is degraded as the buoyancy normal to the heater surfaced increases. Correspondingly, it was later shown, qualitatively for short periods of time only, that nucleate boiling heat transfer is enhanced as the buoyancy normal to the heater surface is reduced. It can be deduced that nucleate pool boiling can be sustained as a quasi-steady process provided that some means is available to remove the vapor generated from the immediate vicinity of the heater surface. One of the objectives of the research, the initial results of which are presented here, is to quantify the heat transfer associated with boiling in microgravity. Some quantitative results of nucleate pool boiling in high quality microgravity (a/g approximately 10(exp -5)) of 5s duration, obtained in an evacuated drop tower, are presented here. These experiments were conducted as precursors of longer term space experiments. A transient heating technique is used, in which the heater surface is a transparent gold film sputtered on a qua rtz substrate, simultaneously providing the mean surface temperature from resistance thermometry and viewing of the boiling process both from beneath and across the surface. The measurement of the transient mean heater surface temperature permits the computation, by numerical means, of the transient mean heat transfer coefficient. The preliminary data obtained demonstrates that a quasi-steady boiling process can occur in microgravity if the bulk liquid subcooling is sufficiently high and if the imposed heat flux is sufficiently low. This is attributed to suface tension effects at the liquid-vapor-solid junction causing rewetting to take place, sustaining the nucleate boiling. Otherwise, dryout at the heater surface will occur, as observed.

Merte, Herman, Jr.; Lee, H. S.; Ervin, J. S.

1994-01-01

122

Transient nucleate pool boiling in microgravity: Some initial results  

NASA Astrophysics Data System (ADS)

Variable gravity provides an opportunity to test the understanding of phenomena which are considered to depend on buoyancy, such as nucleate pool boiling. The active fundamental research in nucleate boiling has sought to determine the mechanisms or physical processes responsible for its high effectiveness, manifested by the high heat flux levels possible with relatively low temperature differences. Earlier research on nucleate pool boiling at high gravity levels under steady conditions demonstrated quantitatively that the heat transfer is degraded as the buoyancy normal to the heater surfaced increases. Correspondingly, it was later shown, qualitatively for short periods of time only, that nucleate boiling heat transfer is enhanced as the buoyancy normal to the heater surface is reduced. It can be deduced that nucleate pool boiling can be sustained as a quasi-steady process provided that some means is available to remove the vapor generated from the immediate vicinity of the heater surface. One of the objectives of the research, the initial results of which are presented here, is to quantify the heat transfer associated with boiling in microgravity. Some quantitative results of nucleate pool boiling in high quality microgravity (a/g approximately 10(exp -5)) of 5s duration, obtained in an evacuated drop tower, are presented here. These experiments were conducted as precursors of longer term space experiments. A transient heating technique is used, in which the heater surface is a transparent gold film sputtered on a qua rtz substrate, simultaneously providing the mean surface temperature from resistance thermometry and viewing of the boiling process both from beneath and across the surface. The measurement of the transient mean heater surface temperature permits the computation, by numerical means, of the transient mean heat transfer coefficient. The preliminary data obtained demonstrates that a quasi-steady boiling process can occur in microgravity if the bulk liquid subcooling is sufficiently high and if the imposed heat flux is sufficiently low. This is attributed to suface tension effects at the liquid-vapor-solid junction causing rewetting to take place, sustaining the nucleate boiling. Otherwise, dryout at the heater surface will occur, as observed.

Merte, Herman, Jr.; Lee, H. S.; Ervin, J. S.

1994-07-01

123

A model for stationary and dynamic impression of undercooled boiling in coupled thermohydraulic and neutron physics calculations of nuclear reactors  

NASA Astrophysics Data System (ADS)

In order to account for subcooled boiling in calculations of neutron physics and thermal hydraulics of light water reactors (where vapor bubbles strongly influence the nuclear chain reaction), a dynamic model is derived from the time-dependent conservation equations. It contains methods for the time-dependent determination of evaporation and condensation heat flow and for the heat transfer coefficient in subcooled boiling. It enables the complete two-phase flow region to be treated consistently. The calculation model was verified using measured data of experiments covering a wide range of thermodynamic boundary conditions. In all cases very good agreement is reached. The results from the coupling of the new calculation model with a neutron kinetics program proves its suitability for the steady-state and transient calculation of reactor cores.

Mueller, Roland Guenther

1987-06-01

124

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

125

Development of Three-Dimensional One-way Bubble Tracking Method for Boiling Flow  

NASA Astrophysics Data System (ADS)

A three-dimensional one-way bubble tracking method is a promising numerical method for calculation of time-spatial evolution of gas-liquid interfacial configuration with use of a little computing resource. Since the method has been applied to only an adiabatic air-water bubble flow, the method is developed for the analysis of a boiling flow in this study. One-dimensional Eulerian equation of energy conservation for a continuous liquid phase and an interface heat transfer equation for dispersed bubbles are introduced. Then, radial liquid temperature distribution, wall heat transfer between a heated wall and subcooled liquid, bubble generation on a heated wall and expansion or condensation of bubbles are taken into account. The developed method is applied to the boiling flow experiment and radial void fraction distribution is compared. It is confirmed that the method can give good prediction of tendency of the void fraction distribution in the boiling flow.

Tamai, Hidesada; Tomiyama, Akio

126

Boiling from small cylinders.  

NASA Technical Reports Server (NTRS)

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

Bakhru, N.; Lienhard, J. H.

1972-01-01

127

Explosive boiling incipience on a thin wire  

NASA Astrophysics Data System (ADS)

When a metastable liquid is superheated above its saturation temperature, a phase transition occurs via a nucleation process leading to the creation of at least one vapor bubble that grows rapidly. If the surrounding liquid is subcooled, the bubble will eventually undergo a violent collapse. A further characterization of the thermodynamic properties of this explosive phase change, (temperature at the onset of nucleation as well as pressure inside the first nuclei), together with the following bubble dynamics, is necessary for a better comprehension of boiling phenomena. Thanks to dedicated experiments in which a platinum micrometer--size wire is heated in a liquid at ambient pressure and temperature, we will report that the onset temperature is close to the spinodal temperature but slightly depends on the heating rate. Using high--speed video imaging of the bubble dynamics together with the Rayleigh--Plesset equation, we will show how the heating rate, as well as the heater size governs the nucleation process (bubble lifetime, maximum radius reached, expansion velocity and cooling of the wire at the onset).

Nardin, Jean--Charles; Poulain, Cdric; Duplat, Jrme

2010-11-01

128

The hydrothermal system of Nevado del Ruiz volcano, Colombia  

Microsoft Academic Search

Hot springs and steam vents on the slopes of Nevado del Ruiz volcano provide evidence regarding the nature of hydrothermal activity within the summit and flanks of the volcano. At elevations below 3000 m, alkali-chloride water is discharged from two groups of boiling springs and several isolated warm springs on the western slope of Nevado del Ruiz. Chemical and isotopic

Neil C. Sturchio; Stanley N. Williams; Nestor P. Garcia; Adela C. Londono

1988-01-01

129

Enhanced Natural Convection in a Metal Layer Cooled by Boiling Water  

SciTech Connect

An experimental study is performed to investigate the natural convection heat transfer characteristics and the solidification of the molten metal pool concurrently with forced convective boiling of the overlying coolant to simulate a severe accident in a nuclear power plant. The relationship between the Nusselt number (Nu) and the Rayleigh number (Ra) in the molten metal pool region is determined and compared with the correlations in the literature and experimental data with subcooled water. Given the same Ra condition, the present experimental results for Nu of the liquid metal pool with coolant boiling are found to be higher than those predicted by the existing correlations or measured from the experiment with subcooled boiling. To quantify the observed effect of the external cooling on the natural convection heat transfer rate from the molten pool, it is proposed to include an additional dimensionless group characterizing the temperature gradients in the molten pool and in the external coolant region. Starting from the Globe and Dropkin correlation, engineering correlations are developed for the enhancement of heat transfer in the molten metal pool when cooled by an overlying coolant. The new correlations for predicting natural convection heat transfer are applicable to low-Prandtl-number (Pr) materials that are heated from below and solidified by the external coolant above. Results from this study may be used to modify the current model in severe accident analysis codes.

Cho, Jae-Seon [Seoul National University (Korea, Republic of); Suh, Kune Y. [Seoul National University (Korea, Republic of); Chung, Chang-Hyun [Seoul National University (Korea, Republic of); Park, Rae-Joon [Korea Atomic Energy Research Institute (Korea, Republic of); Kim, Sang-Baik [Korea Atomic Energy Research Institute (Korea, Republic of)

2004-12-15

130

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

131

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

132

Critical flashing flows in nozzles with subcooled inlet conditions  

NASA Astrophysics Data System (ADS)

A unified theory is presented for the calculation of critical mass flow rates through converging-diverging nozzles with subcooled inlets. It is shown that the correlation of flashing inception leads to the determination that flashing onset occurs virtually at the throat (plane of minimum flow area) in nozzles. It is also shown how this observation, coupled with an accurate prediction for the under-pressure at inception based on Alagmir and Lienhard (1979), leads directly to an accurate computation of the critical discharge rates in nozzles. The mass fluxes predicted on the basis of the proposed theory are within 5 percent of the measurements.

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

1983-05-01

133

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

134

Electrical Breakdown Characteristics of Superconducting Magnet System in Sub-Cooled Liquid Nitrogen  

Microsoft Academic Search

Dielectric characteristics of gaseous helium (GHe) injected into the cooling system to make sub-cooled nitrogen condition with constant pressure is found to be extraordinarily weak in dielectric strength by H. Mitsuii (1998). In high voltage superconducting machines using the sub-cooled nitrogen cooling system, the current lead part in GHe environment could be electrical weak points rather than the superconducting magnet

Hyoungku Kang; Chanjoo Lee; Tae Kuk Ko; Bok-Yeol Seok

2007-01-01

135

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

136

Microheater Array Boiling Experiment  

NASA Technical Reports Server (NTRS)

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

Kim, Jungho; McQuillen, John; Balombin, Joe

2002-01-01

137

Subcooled choked flow through steam generator tube cracks  

NASA Astrophysics Data System (ADS)

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

Wolf, Brian J.

138

Development, implementation, and assessment of specific closure laws for inverted-annular film-boiling in a two-fluid model  

Microsoft Academic Search

Inverted-Annular Film-Boiling (IAFB) is one of the post-burnout heat transfer modes taking place during the reflooding phase of the loss-of-coolant accident, when the liquid at the quench front is subcooled. Under IAFB conditions, a continuous liquid core is separated from the wall by a superheated vapour film. The heat transfer rate in IAFB is influenced by the flooding rate, liquid

Chachard; F. de

1996-01-01

139

Study of film boiling in He II by pressure and temperature oscillation measurements  

NASA Astrophysics Data System (ADS)

In the present study, the discussion on film boiling states in He II is presented on the basis of some new experimental results. Experiments were conducted under various thermal conditions, e.g., different bath temperature, immersion depth and heat flux. In subcooled film boiling state, a flame-shaped vapor bubble is seen to be quivering on a planar heater accompanied with a little audible noise, and the pressure oscillation is detected, which results from both vapor bubble oscillation and liquid column oscillation of bulk He II in a cryostat. In noisy boiling state in saturated He II, a big vapor bubble grows and erupts repeatedly on a planar heater accompanied with a large acoustic noise, and the pressure oscillation is mainly caused in accordance with vapor bubble crush and formation. A three-dimensional boundary map indicating different boiling states is constructed by taking account of effects of the bath temperature and the heat flux as well as the hydrostatic pressure. Temperature oscillation during noisy film boiling is also measured by the aid of superconductor temperature sensors. It is found that the large temperature rise is caused by both the passage of thermal boundary layer and repeated expansion and crush of a vapor bubble on the planar heater.

Zhang, P.; Murakami, M.; Wang, R. Z.; Inaba, H.

1999-11-01

140

A composite heat-transfer model of the film-boiling regime  

SciTech Connect

An approximate set of coupled ordinary differential equations developed describe the temporal evolution of the vapor domes and film over a flat-plate heater surface during film boiling for the general case of a subcooled bulk liquid. A phenomenological model is then developed to describe the intermittent surface-wetting process observed to occur in the film-boiling regime. Assuming that the heater surface has been locally wetted, equations are developed to predict the time-dependent heat flux during contact and the subsequent duration of the liquid dryout period. Additionally, assuming that liquid propagation along the surface is terminated at the inception of nucleat boiling, an expression is developed to predict the wetted area of contact at a given node site. The hydrodynamic and surface interaction results are then combined to obtain an expression for the composite heat flux in the film-boiling regime. A comparison of the local liquid-solid contact model with experimental data available indicates that the model adequately predicts the wetted area fraction in a large neighborhood of the minimum film boiling point for an aluminum-water system. The model slightly underpredicts the wetted area fraction for methanol on the same surface.

Farmer, M.T.

1988-01-01

141

Study of liquid column oscillation and vapour bubble oscillation resulting from film boiling in He II  

NASA Astrophysics Data System (ADS)

The pressure oscillations during different film boiling modes in He II are studied in this paper. In the sub-cooled film boiling state, a flame-shaped vapour bubble can be seen to be quivering on the planar heater accompanied by a little audible noise, and the pressure oscillation, resulting from both vapour bubble oscillation and liquid column oscillation of bulk He II in a cryostat, is detected. In the noisy film boiling state in saturated He II, a big vapour bubble expands and crushes repeatedly on the planar heater accompanied by a loud acoustic noise, and the pressure oscillation is mainly caused by the crushing and formation of the vapour bubble. There are two possibilities for the occurrence of transition boiling. A theoretical analysis of the pressure oscillation was also carried out, which agreed well with the experimental results.

Zhang, P.; Murakami, M.; Wang, R. Z.

2001-11-01

142

Criteria for approximating certain microgravity flow boiling characteristics in Earth gravity.  

PubMed

The forces governing flow boiling, aside from system pressure, are buoyancy, liquid momentum, interfacial surface tensions, and liquid viscosity. Guidance for approximating certain aspects of the flow boiling process in microgravity can be obtained in Earth gravity research by the imposition of a liquid velocity parallel to a flat heater surface in the inverted position, horizontal, or nearly horizontal, by having buoyancy hold the heated liquid and vapor formed close to the heater surface. Bounds on the velocities of interest are obtained from several dimensionless numbers: a two-phase Richardson number, a two-phase Weber number, and a Bond number. For the fluid used in the experimental work here, liquid velocities in the range U = 5-10cm/sec are judged to be critical for changes in behavior of the flow boiling process. Experimental results are presented for flow boiling heat transfer, concentrating on orientations that provide the largest reductions in buoyancy parallel to the heater surface, varying +/-5 degrees from facing horizontal downward. Results are presented for velocity, orientation, and subcooling effects on nucleation, dryout, and heat transfer. Two different heater surfaces were used: a thin gold film on a polished quartz substrate, acting as a heater and resistance thermometer, and a gold-plated copper heater. Both transient and steady measurements of surface heat flux and superheat were made with the quartz heater; only steady measurements were possible with the copper heater. R-113 was the fluid used; the velocity varied over the interval 4-16cm/sec; bulk liquid subcooling varied over 2-20 degrees C; heat flux varied over 4-8W/cm(2). PMID:12446343

Merte, Herman; Park, Jaeseok; Shultz, William W; Keller, Robert B

2002-10-01

143

Critical two-phase flow in pipes for subcooled stagnation states with cavity flooding incipient flashing model  

SciTech Connect

Analysis of loss of coolant accident (LOCA) scenarios in nuclear reactor safety evaluation depends on knowledge of many complex phenomena. A primary phenomenon controlling the sequence of events, by determining the residual coolant mass inventory within the primary system, is the critical flow process. Critical flow of a flashing liquid is complicated by marked departure from thermal equilbrium. Several complex models have been proposed to represent the non-equilibrium effects, including six-equation two-fluid models. In the present paper a new cavity flooding model is used for the evaluation of pressure undershoot at flashing inception. This model is similar to the one developed by Fabic (1964) for the evaluation of liquid superheat required for boiling on a surface subjected to transient heating. The model contains an experimentally deduced factor, which is correlated against stagnation subcooling using the experimental data of Amos and Schrock (1983, 1984), Jeandey et al. (1981), and the Marviken tests (Anon., 1979). The model was then tested against seven additional data sets and shown to be very accurate in predicted mass flux (standard deviation of 10.9% for all data). The cavity flooding model is thought to represent the true physics more correctly than does the earlier model, which had its origin in molecular fluctuation theory.

Lee, S.Y. (Westinghouse Savannah River Co., GA (USA)); Schrock, V.E. (Univ. of California, Berkeley (USA))

1990-11-01

144

Stability of a NbTi forced-cooled superconducting coil by subcooled supercritical helium  

Microsoft Academic Search

The stability and quench characteristics of a NbTi forced-cooled superconducting coil at the subcooled condition were investigated. The test coil was wound in a one-layer solenoid from a cable-in-conduit-type conductor of 1.5 kA at 7 T, whose total length was 34 m. It was installed in a background coil and tested between the subcooled condition below 4.5 K and the

Y. Wachi; M. Shimada; T. Hamajima; M. Yamaguchi

1992-01-01

145

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.

2014-03-01

146

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 40C 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 0.5C in the majority of cases.

Norman, Timothy Linhurst

147

Quantification of Data Needs, Data Collection and Charactization to Support Validation and Calibration of Subcooled Flow Boiling Model.  

National Technical Information Service (NTIS)

Further to the development of a model analysis framework suitable for calibration and validation of complex multivariate multiphysics models detailed in this report presents an approach to data collection and characterization which can work in parallel wi...

A. Bui N. Dinh

2013-01-01

148

Low pressure boiling lithium experiments  

Microsoft Academic Search

A series of low pressure boiling lithium tests have been run to determine wall superheat. These tests were run primarily to identify the possibility of using boiling lithium as a first wall coolant in fusion devices. One of the major disadvantages of using liquid metals in a magnetically contained fusion machine is the large pump energy expended to force the

Wadkins

1984-01-01

149

Boiling Suppression in Convective Flow  

Microsoft Academic Search

The development of convective boiling heat transfer correlations and analytical models has almost exclusively been based on measurements of the total heat flux, and therefore on the overall two-phase heat transfer coefficient, when the well-known heat transfer correlations have often assumed additive mechanisms, one for each mode of heat transfer, convection and boiling. While the global performance of such correlations

Aounallah

2004-01-01

150

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

151

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

NASA Technical Reports Server (NTRS)

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

Ling, Jerri S.; Laubenthal, James R.

1990-01-01

152

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

153

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

154

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

155

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

156

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...

157

D0 Silicon Upgrade: Liquid Nitrogen Subcooler Coil Sizing for D-Zero Upgrade  

SciTech Connect

The raw calculations are attached as Appendix A. The calculations provide the analysis of the heat transferred while the LN{sub 2} subcooler is in use. In order to achieve an acceptable conclusion, the assumption of a fully developed thermal boundary layer was made. The hot fluid or the fluid condensing on the inside surface will determine the rate of heat transfer because A{sub o} = A{sub i} and h{sub o}A{sub o} >> h{sub i}A{sub i}. The conclusion drawn is to use a 1/2-inch OD copper tube wound approximately 8 times about an 8-inch diameter circle. There are also calculations concerning the size of the nitrogen supply and subcooler vent. The maximum mass flow rate was determined as 52.5 g/s and the sizing of the nitrogen supply and subcooler vent should be chosen accordingly.

Kuwazaki, Andrew; Leicht, Todd; /Fermilab

1995-10-03

158

Operation and Control of Helium Subcooling System of LHD Helical Coils During Change of Rotational Speed of Cold Compressors  

Microsoft Academic Search

Helical coils of the Large Helical Device (LHD) are large scale superconducting magnets for fusion plasma experiments. The cooling system was upgraded in 2006 to improve the cryogenic stability of the coils by subcooling supplied helium. After the upgrade, the subcooled helium of designed mass flow rate of 50 g\\/s at designed temperature of 3.2 K has been supplied to

Shinji Hamaguchi; Tetsuji Okamura; Shinsaku Imagawa; Tetsuhiro Obana; Nagato Yanagi; Koki Oba; Sadatomo Moriuchi; Haruo Sekiguchi; Toshiyuki Mito

2010-01-01

159

Visualisation of flow boiling heat transfer in a microtube  

NASA Astrophysics Data System (ADS)

This paper presents the results of the flow boiling patterns and heat transfer coefficients of FC-72 in a small tube. The internal diameter of the tube is 0.48 mm, with a heated length of 73 mm. The mass flow rate varies from 50 to 3,000 kg/m2-s. The microtube is made of Pyrex in order to obtain the visualisation of the flow pattern along the heated channel. Different types of flow pattern have been observed: bubbly flow, deformed bubbly flow, bubbly/slug flow, slug flow, slug/annular flow, and annular flow. The experiments show the presence of flow instabilities in a large portion of the tests at low mass flow rates and low subcooling. Flow patterns in presence of flow instabilities are mainly characterized by bubbly/slug flow and slug/annular flow. Heat transfer rates have been studied in all flow pattern conditions. The two groups of results, with flow instabilities and without flow instabilities, show similar heat transfer behaviour. The heat transfer characteristics of the pipes have been studied in comparison with mass flux and vapour quality.

Celata, G. P.; Cumo, M.; Dossevi, D.; Jilisen, R. T. M.; Saha, S. K.; Zummo, G.

2011-08-01

160

Experimental investigation of film boiling on spheres using high-speed video  

NASA Astrophysics Data System (ADS)

The experimental investigation of saturated Freon-113 film boiling on spheres with different diameters at atmospheric pressure under conditions of free convection is executed. It was found that with increasing diameter of the sphere and the temperature difference is changing the wave motion of the vapor film with two-dimensional to three-dimensional mode. Also, found that in a range of regime parameters at which observed a three-dimensional interface motion, the destruction method of two-dimensional wave is similar to a series of three or more waves. I.e. was some system memory. When the temperature difference close to critical after the passage of a wave are possible the local contacts of liquid with a heated surface of the sphere. However, these contacts do not lead to degradation of the wave motion of the interface, and the film boiling crisis of saturated Freon-113 occurs smoothly in contrast to the crisis at boiling of saturated and subcooled water.

Agaltsov, Andrey; Fedoseenko, Ivan

2012-04-01

161

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

NASA Astrophysics Data System (ADS)

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

Das, Kausik S.; Wilson, Stephen K.

2010-04-01

162

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

PubMed

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

Das, Kausik S; Wilson, Stephen K

2010-04-01

163

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

NASA Technical Reports Server (NTRS)

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

Simoneau, R. J.

1974-01-01

164

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

165

Direct Numerical Simulations of Boiling  

NASA Astrophysics Data System (ADS)

For flow problem of practical interest it is frequently necessary to account for phase change between liquid and vapor. Boiling, in particular, is one of the most efficient ways of removing heat from a solid surface. It is therefore commonly used in energy generation and refrigeration. The large volume change and the high temperatures involved can make the consequences of design or operational errors catastrophic and accurate predictions are highly desirable. For numerical simulations of boiling it is necessary to solve the energy equation, in addition to conservation equations for mass and momentum, and to account for the release/absorption of latent heat at the phase boundary. We describe a numerical method for direct numerical simulations of boiling and show results from simulations of explosive boiling of a vapor bubble in an initially superheated liquids. As the vapor bubble grows, its surface becomes unstable, developing wrinkles that increase the surface area significantly. The increased surface area does, however, have relatively little impact on the growth rate for the parameters examined due to a relatively thick thermal boundary layer. We have also examined film boiling and find relatively good agreement with experimental correlations. Research supported by NASA.

Tryggvason, Gretar; Esmaeeli, Asghar

2003-11-01

166

Microgravity experiments on boiling and applications: research activity of advanced high heat flux cooling technology for electronic devices in Japan.  

PubMed

Research and development on advanced high heat flux cooling technology for electronic devices has been carried out as the Project of Fundamental Technology Development for Energy Conservation, promoted by the New Energy and Industrial Technology Development Organization of Japan (NEDO). Based on the microgravity experiments on boiling heat transfer, the following useful results have obtained for the cooling of electronic devices. In subcooled flow boiling in a small channel, heat flux increases considerably more than the ordinary critical heat flux with microbubble emission in transition boiling, and dry out of the heating surface is disturbed. Successful enhancement of heat transfer is achieved by a capillary effect from grooved surface dual subchannels on the liquid supply. The critical heat flux increases 30-40 percent more than for ordinary subchannels. A self-wetting mechanism has been proposed, following investigation of bubble behavior in pool boiling of binary mixtures under microgravity. Ideas and a new concept have been proposed for the design of future cooling system in power electronics. PMID:15644356

Suzuki, Koichi; Kawamura, Hiroshi

2004-11-01

167

CFD simulation of steam jet-induced thermal mixing in subcooled water pool  

Microsoft Academic Search

This study examined the IRWST thermal mixing phenomena induced by a steam jet in a subcooled water pool. Due to the limitation of the current CFD code to simulate condensation, the steam condensation region model was developed to evaluate the thermal mixing phenomena. Within this region, all the steam was condensed into water, and the steam mass and energy inputs

Young-Tae Moon; Hee-Do Lee; Goon-Cherl Park

2009-01-01

168

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

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

169

Analysis of Infiltration, Solidification, and Remelting of a Pure Metal in Subcooled Porous Preform  

Microsoft Academic Search

The parts fabricated by selective laser sintering of metal powders are usually not fully densified and have porous structure. Fully densified parts can be obtained by infiltrating liquid metal into the porous structure and solidifying the liquid metal. When the liquid metal is infiltrated into the subcooled porous structure, the liquid metal can be partially solidified. Remelting of the partially

Yuwen Zhang; Piyasak Damronglerd; Mo Yang

2010-01-01

170

Initiation of water hammer in horizontal or nearly-horizontal pipes containing steam and subcooled water  

NASA Astrophysics Data System (ADS)

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

1983-02-01

171

Transient Heat Transport in Subcooled He II Associated with JT Effect  

Microsoft Academic Search

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

R. Maekawa; A. Iwamoto; S. Hamaguchi

2004-01-01

172

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

SciTech Connect

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

Kuwazaki, Andrew; Leicht, Todd; /Fermilab

1995-10-04

173

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

Microsoft Academic Search

Melting and resolidification of a subcooled spherical metal powder particle subjected to nanosecond laser heating are investigated analytically. The problem is divided into three stages: preheating, melting and resolidification, and thermalization. The temperature distributions in the liquid and solid regions and the location of the solidliquid interface are obtained using an integral approximate method. The effects of the laser intensity

Chad Konrad; Yuwen Zhang; Yu Shi

2007-01-01

174

Pool Boiling of Hydrocarbon Mixtures on Water.  

National Technical Information Service (NTIS)

In maritime transport of liquefied natural gas (LNG) there is a risk of spilling cryogenic liquid onto water. The present doctoral thesis discusses transient boiling experiments in which liquid hydrocarbons were poured onto water and left to boil off. Com...

R. Boee

1996-01-01

175

Variability in the microbial communities and hydrothermal fluid chemistry at the newly discovered Mariner hydrothermal field, southern Lau Basin  

NASA Astrophysics Data System (ADS)

A newly discovered hydrothermal field called the Mariner field on the Valu Fa Ridge in the southern Lau Basin was explored and characterized with geochemical and microbiological analyses. The hydrothermal fluid discharging from the most vigorous vent (Snow Chimney, maximum discharge temperature 365C) was boiling at the seafloor at a depth of 1908 m, and two distinct end-member hydrothermal fluids were identified. The fluid chemistry of the typical Cl-enriched and Cl-depleted hydrothermal fluids was analyzed, as was the mineralogy of the host chimney structures. The variability in the fluid chemistry was potentially controlled by the subseafloor phase-separation (vapor loss process) and the microbial community activities. Microbial community structures in three chimney structures were investigated using culture-dependent and -independent techniques. The small subunit (SSU) rRNA gene clone analysis revealed that both bacterial and archaeal rRNA gene communities on the chimney surfaces differed among three chimneys. Cultivation analysis demonstrated significant variation in the culturability of various microbial components among the chimneys, particularly of thermophilic H2-oxidizing (and S-oxidizing) chemolithoautotrophs such as the genera Aquifex and Persephonella. The physical and chemical environments of chimney surface habitats are still unresolved and do not directly extrapolate the environments of possible subseafloor habitats. However, the variability in microbial community found in the chimneys also provides an insight into the different biogeochemical interactions potentially affected by the phase separation of the hydrothermal fluids in the subseafloor hydrothermal habitats. In addition, comparison with other deep-sea hydrothermal systems revealed that the Mariner field microbial communities have unusual characteristics.

Takai, Ken; Nunoura, Takuro; Ishibashi, Jun-Ichiro; Lupton, John; Suzuki, Ryohei; Hamasaki, Hiroshi; Ueno, Yuichiro; Kawagucci, Shinsuke; Gamo, Toshitaka; Suzuki, Yohey; Hirayama, Hisako; Horikoshi, Koki

2008-06-01

176

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

177

Nucleate Boiling and the Chen Correlation for Flow Boiling Heat Transfer  

Microsoft Academic Search

In flow boiling experiments on water in a vertical tube, the Chen correlation predicted the convective heat transfer coefficient satisfactorily but overpredicted the nucleate boiling contribution. The tube material had rather low densities of bubble nucleation sites, measured by observation in boiling and by gas bubble nucleation: the methods agreed only if the gas measurements were made after boiling, which

Y. Aounallah; D. B. R. Kenning

1987-01-01

178

"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

179

Film boiling chemical vapor infiltration  

Microsoft Academic Search

Several chemical vapor infiltration (CVI) processes have been developed to increase both the carbon yield and the densification rate for a controlled type of pyrocarbon deposit. Recently, the film boiling technique (so-called Kalamazoo) has been successfully developed for making in particular C\\/C composite materials. To get a better insight on this process, we have built up two small laboratory reactors

D Rovillain; M Trinquecoste; E Bruneton; A Derr; P David; P Delhas

2001-01-01

180

Boiling in variable gravity under the action of an electric field: results of parabolic flight experiments  

NASA Astrophysics Data System (ADS)

Results from the variable gravity pool boiling experiments performed during the 52nd ESA parabolic flight campaign are reported in this paper. During a typical parabola, the gravity acceleration changes from 1.8gE (high gravity) to ~0gE (low gravity) and finally back to 1.8gE. The two high gravity periods and the microgravity period are each roughly maintained for 20 seconds while the transition from high gravity to low gravity and vice versa occurs over a period of 3-5 seconds. Use of the high feedback frequency microheater array allowed quasi-steady boiling data over the continuous range of gravity levels (0gE-1.8gE). The experimental apparatus consisted of a boiling chamber with a 77 mm2 microheater array in a 1010 configuration. Each heater in the array was individually controlled to maintain a constant temperature. The array could be operated in a full configuration or a selectively powered reduced set of 33 heaters. Experiments were performed with FC-72 as the test fluid, the pressure was maintained at a constant value between 1 and 1.13 atm and the subcooling ranged from 27 to 11 K. An external electric field was imposed over the boiling surface by means of a grid consisting of 4 rods, laid parallel to the surface; voltages up to 10 kV were applied. The electric field was effective in reducing the size of the detaching bubbles, and increasing the heat transfer compared to the values in low-g, although its effectiveness decayed as the heat flux/superheat increased. The current results compared well with previous results obtained in the ARIEL apparatus that was operated in orbital flight.

Di Marco, P.; Raj, R.; Kim, J.

2011-12-01

181

A study of flow boiling phenomena using real time neutron radiography  

NASA Astrophysics Data System (ADS)

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

Novog, David Raymond

182

Submarine hydrothermal fossils confirmed  

NASA Astrophysics Data System (ADS)

Researchers from Princeton University (D. Crerrar et al, Econ. Geol., May 1982) have documented, in considerable detail, evidence for the formation of some of the 800 or more manganiferous chert deposits occurring in the central belt of the Fransiscan formation in northwestern California. They confirm the surprisingly old conclusion o f Tiaferro and Hudson (Cal. Div. Mines Bull., 125, 217-276, 1943) that the Fransiscan chert deposits probably represent the fossil remains of submarine hydrothermal vents.The deposits resemble recently discovered hydrothermal mounds near the Galapagos rift, the Gulf of Aden, and the Mid-Atlantic Ridge. As the Princeton investigators point out, there are important implications of the existence of deep hydrothermal circulation systems at oceanic spreading centers throughout geologic time. They note that the calculated annual flow of hydrothermal fluids in such processes is about 1017 g, which implies that the entire volume of the oceans could circulate completely every 10 million years. With such circulation, the hydrothermal processes along midocean ridges could control the composition of seawater and strongly influence the geochemical flux of elements in the marine environment.

Bell, Peter M.

183

Hydrothermal Synthesis of Ceramic Powders.  

National Technical Information Service (NTIS)

The history of the hydrothermal synthesis is summarized and an appropriate definition of hydrothermal processing and its associated conditions is described. The chronological development of the present large scale process as it is now in operation in the ...

P. Krijgsman

1992-01-01

184

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

185

The hydrothermal system of the Calabozos caldera, central Chilean Andes  

USGS Publications Warehouse

Active thermal springs associated with the late Pleistocene Calabozos caldera complex occur in two groups: the Colorado group which issues along structures related to caldera collapse and resurgence, and the Puesto Calabozos group, a nearby cluster that is chemically distinct and probably unrelated to the Colorado springs. Most of the Colorado group can be related to a hypothetical parent water containing ???400 ppm Cl at ???250??C by dilution with ???50% of cold meteoric water. The thermal springs in the most deeply eroded part of the caldera were derived from the same parent water by boiling. The hydrothermal system has probably been active for at least as long as 300,000 years, based on geologic evidence and calculations of paleo-heat flow. There is no evidence for economic mineralization at shallow depth. The Calabozos hydrothermal system would be an attractive geothermal prospect were its location not so remote. ?? 1987.

Grunder, A. L.; Thompson, J. M.; Hildreth, W.

1987-01-01

186

The effect of refrigerant combinations on performance of a vapor compression refrigeration system with dedicated mechanical sub-cooling  

Microsoft Academic Search

Performance characteristics due to use of different refrigerant combinations in vapor compression cycles with dedicated mechanical sub-cooling are investigated. For scratch designs, R134a used in both cycles produced the best results in terms of COP, COP gain and relative compressor sizing. In retrofit cases, considering the high sensitivity of COP to the relative size of heat exchangers in the sub-cooler

Bilal Ahmed Qureshi; Syed M. Zubair

187

On optimum interstage pressure for two-stage and mechanical-subcooling vapor-compression refrigeration cycles  

SciTech Connect

The objective of the present study is to demonstrate that the optimum interstage pressure for a two-stage refrigeration system can be approximated by the saturation pressure corresponding to the arithmetic mean of the condensing and evaporating temperatures. It is also shown that the optimum performance of a refrigeration system with mechanical sub-cooling occurred when the subcooler compressor (saturation suction) temperature corresponds to the arithmetic mean of the condensing and evaporating temperatures.

Zubair, S.M.; Khan, S.H. [King Fahd Univ. of Petroleum and Minerals, Dhahran (Saudi Arabia). Dept. of Mechanical Engineering

1995-02-01

188

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

Microsoft Academic Search

The 1982 eruption of El Chichn 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

189

Maximum two-phase flow rates of subcooled nitrogen through a sharp-edged orifice  

NASA Technical Reports Server (NTRS)

Data are presented of an experiment in which subcooled liquid nitrogen was discharged through a sharp-edged orifice at flow rates near the maximum. The data covered a range of inlet stagnation pressures from slightly above saturation to twice the thermodynamic critical pressure. The data were taken along five separate inlet stagnation isotherms ranging from 0.75 to 1.035 times the thermodynamic critical temperature. The results indicate that subcooled liquids do not choke or approach maximum flow in an asymptotic manner even though the back pressure is well below saturation; and orifice flow coefficients are not constant as is frequently assumed. A metastable jet appears to exist which breaks down if the difference between back pressure and saturation pressure is large enough.

Simoneau, R. J.

1975-01-01

190

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.

191

Analysis on energy saving potential of integrated supermarket HVAC and refrigeration systems using multiple subcoolers  

Microsoft Academic Search

The paper presents a model-based analysis on the energy saving potential of supermarket HVAC (heating, ventilating, and air-conditioning) and refrigeration systems using multiple subcoolers among the high-temperature HVAC system, the medium-temperature refrigeration system, and the low-temperature refrigeration system. The principle of energy reduction is to have the higher COP (coefficient of performance) system generate more cooling capacity to increase the

Liang Yang; Chun-Lu Zhang

2010-01-01

192

Stability characteristics of a cable-in-conduit conductor by subcooled supercritical helium  

Microsoft Academic Search

The stability and limiting current of a NbTi forced-cooled superconducting coil have been investigated experimentally and analytically at the subcooled condition below 4.5 K. The test coil was wound in a one layer solenoid from a cable-in-conduit type conductor of critical current of 5.1 kA at 4.2 K and 6.5 T, whose total length was 10 m. It was installed

Y. Wachi; S. Hanawa; M. Ono; M. Shimada; T. Hamajima; H. Takano; H. Shinohara; K. Takahata; J. Yamamoto; O. Motojima

1994-01-01

193

Cryostat for electron irradiation experiments in subcooled superfluid helium at 1.8K  

Microsoft Academic Search

A cryostat for irradiation of solids with 3 MeV electrons at 1.8K is described. Highcooling power and optimized heat transfer between sample and cryoliquid are provided by using a constant volume subcooled superfluid helium bath. Refrigeration to 1.8K is performed by precooling the helium in a heat exchanger and subsequent expansion in a Joule-Thomson valve in connection with a 2000m3\\/h

K.-H. Greubel; E. Gmelin; M. Kienhfer; J. Major

1994-01-01

194

Performance of Heat Exchanger for Subcooling Liquid Nitrogen with a GM Cryocooler  

NASA Astrophysics Data System (ADS)

A heat exchanger to continuously supply subcooled liquid nitrogen at 65~70 K in thermal contact with a Gifford-McMahon (GM) cryocooler is experimentally investigated. This study is motivated by HTS power applications, where liquid nitrogen is circulated in subcooled state by forced convection and a regenerative cryocooler is used for continuous refrigeration. Since the coldhead of the cooler has a very limited surface area, a cylindrical ``cup'' made of copper is attached to the coldhead to serve as extended surface. A copper tube for liquid nitrogen flow is spirally wound and silver-brazed on the exterior surface of cylinder. In order to examine the effect of physical dimensions on the cooling performance, different sizes of heat exchangers are fabricated and tested with a commercial GM cooler to subcool liquid nitrogen from 78 K to 65~70 K. It is clearly shown that there exists an optimal size of heat exchanger cylinder to achieve a maximum cooling of liquid nitrogen. The reason for poor performance with a smaller size is that the cooling surface is not enough, and the reason for poor performance with a larger size is that the effectiveness of extended surface is lower and the heat leak from surroundings is greater.

Chang, H. M.; Ryu, S. H.; Kim, M. J.

2010-04-01

195

An experimental study of subcooled choked flow through steam generator tube cracks  

NASA Astrophysics Data System (ADS)

The Work conducted in this Research involved the simulation of Pressurized Water Reactor Conditions of Steam Generators to study the complex phenomenon of Subcooled Choked Flow or two-phase critical flow that occurs when water leaks from the primary side of a steam generator into the secondary side, thus making it highly relevant to Reactor Safety and Probabilistic Risk assessment methods. Slits of small L/D ratio were manufactured and tested on the Facility for Leak Rate Testing at pressures (6.89 MPa) and high temperatures (280C) relevant to Pressurized Water Reactors over a range of subcooling. Small flow channel length was used (1.3mm) equivalent to steam generator tube thickness with the study of a variety of geometries with differences in surface roughness. Unique to literature, the samples had very small L/Ds and the study was a controlled parametric study of choked flow. The effect of L/D was examined, compared to recent studies conducted at Purdue University by Wolf and Revankar while contrasting with others in literature. Analytical models were applied highlighting the importance of non-equilibrium effects and contrasted with other studies of different L/Ds. RELAP5, a well developed code widely utilized in industry was studied to analyze its predictive capabilities and conditions for best estimate. L/D effects on mass fluxes were studied and it was observed that mass fluxes were affected to a very small degree by subcooling.

Vadlamani, Ram Anand

196

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

197

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

198

Hydrothermal pretreatment of coal  

SciTech Connect

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

Loo, Bock; Ross, D.S.

1990-08-14

199

Hydrothermal Reactivity of Amines  

NASA Astrophysics Data System (ADS)

The reactivity of aqueous amines depends on temperature, pH, and redox state [1], all of which are highly variable in hydrothermal systems. Temperature and pH affect the ratio of protonated to unprotonated amines (R-NH2 + H+ = R-NH3+), which act as nucleophiles and electrophiles, respectively. We hypothesize that this dual nature can explain the pH dependence of reaction rates, and predict that rates will approach a maximum at pH = pKa where the ratio of protonated and unprotonated amines approaches one and the two compounds are poised to react with one another. Higher temperatures in hydrothermal systems allow for more rapid reaction rates, readily reversible reactions, and unique carbon-nitrogen chemistry in which water acts as a reagent in addition to being the solvent. In this study, aqueous benzylamine was used as a model compound to explore the reaction mechanisms, kinetics, and equilibria of amines under hydrothermal conditions. Experiments were carried out in anoxic silica glass tubes at 250C (Psat) using phosphate-buffered solutions to observe changes in reaction rates and product distributions as a function of pH. The rate of decomposition of benzylamine was much faster at pH 4 than at pH 9, consistent with the prediction that benzylamine acts as both nucleophile and an electrophile, and our estimate that the pKa of benzylamine is ~5 at 250C and Psat. Accordingly, dibenzylamine is the primary product of the reaction of two benzylamine molecules, and this reaction is readily reversible under hydrothermal conditions. Extremely acidic or basic pH can be used to suppress dibenzylamine production, which also suppresses the formation of all other major products, including toluene, benzyl alcohol, dibenzylimine, and tribenzylamine. This suggests that dibenzylamine is the lone primary product that then itself reacts as a precursor to produce the above compounds. Analog experiments performed with ring-substituted benzylamine derivatives and chiral methylbenzylamine suggest an SN2 mechanism for the formation of dibenzylamine. These results show the interdependence of pH and speciation with amine reaction rates. We predict the distribution of primary, secondary, tertiary, and quaternary amines in hydrothermal solutions can be used to solve for the pH of subsurface reaction zones in hydrothermal systems. [1] McCollom, T.M. (2013) The influence of minerals on decomposition of the n-alkyl-?-amino acid norvaline under hydrothermal conditions. Geochim. Cosmochim. Acta, 104, 330-357.

Robinson, K.; Shock, E.; Hartnett, H. E.; Williams, L. B.; Gould, I.

2013-12-01

200

EHD enhancement of nucleate boiling. [Electrohydrodynamic  

SciTech Connect

This paper describes: (a) an experimental investigation into the effect of an electric field applied to pool boiling of Freon (R114) on a finned tube and (b) a theoretical model of electrically enhanced nucleate boiling applicable to simple surfaces only. Experimental results have shown electrohydrodynamic (EHD) enhancement of heat transfer to be manifest in two ways: (1) elimination of boiling hysteresis, (2) augmentation of nulceate boiling heat transfer coefficients by up to an order of magnitude. These effects were also observed in electrically enhanced boiling of Freon/oil mixtures. A new analytical model is described whereby EHD nucleate boiling data from previous studies (employing simple apparatus comprising heated wires with concentric cylinder electrodes) have been correlated for the first time using the concept of an electrical influence number. This dimensionless parameter is based upon the relationship between applied electric field intensity and changes in bubble departure diameter at a heat transfer surface.

Cooper, P. (Univ. of Wollongong, New South Wales (Australia))

1990-05-01

201

Boiling on a cryogenically cooled pulsed conductor  

NASA Astrophysics Data System (ADS)

Active cryogenic cooling of pulsed conductors in high power systems offers greatly reduced resistive energy losses. This paper presents unique boiling data for pulsed power inputs at repetition rates of 5 Hz and heating pulses of 2 to 20 ms duration. An initial analytical model is developed for the transient boiling behavior during pulsed heating and cooldown cycles based in part on a quasi-steady extension of existing correlations and data for steady boiling in the nucleate, transition, and film boiling regimes. Both pool and forced flow boiling are treated. This model includes the concept of a mixed microlayer for treatment of enhanced heat flux to the coolant during rapid heating transients in boiling. Investigated test conditions include those where the power input to the conductor exceeds the value at steady-state critical heat flux by several times.

Crowley, Christopher J.; Kang, Sukhvinder S.; Rothe, Paul H.

202

Boiling/evaporative heat transfer from spheres in packed-bed thermal energy storage units  

NASA Astrophysics Data System (ADS)

An experimental study was conducted to study boiling/evaporative heat transfer from heated spheres in vertical packed beds with downward liquid vapor flow of Refrigerant-113. Surface superheats of 1 to 50 C; mass flow rates of 1.7, 2.7, and 5.6 kg/min; sphere diameters of 1.59 and 2.54 cm; quality (i.e., mass fraction of vapor) of the inlet flow of 2 to 100 percent; and two surface roughness conditions were considered. To determine heat transfer coefficients, smooth and roughened aluminum spheres of the same diameter as the other spheres in the bed were instrumented with two thermocouples each for measuring the surface temperatures and a tiny electrical resistance heater for input power. The heat transfer measurements were made under steady-state conditions. Heat transfer coefficients were independently determined for each sphere at three values of surface superheat. The quantitative results are represented as a correlation for the boiling heat transfer coefficients in terms of a homogeneous model. The equation correlates very effectively with the dimensionless temperature difference. The correlation may be used in the development of numerical models to simulate the transient thermal performance of a packed-bed thermal energy storage unit while operating as an evaporator. The boiling of the liquid vapor flow around the spheres in the packed bed was visually observed with a fiber optic boroscope and recorded on a video tape. The visualization results showed qualitatively the presence of our four distinct flow regimes. One of these occurs under subcooled regime. The other three occur under saturated inlet conditions and are referred to as the low-quality, medium-quality, and high-quality regimes. The regimes are discussed in detail.

Arimilli, R. V.; Moy, C. A.

1990-05-01

203

Correlation of pool boiling curves for the homogeous group freons  

Microsoft Academic Search

A knowledge of the complete boiling curve q verses T for a liquid, including the regimes of nucleate boiling, transition boiling, and a film boiling is needed for the design and operation of various types of heat transfer equipment. No general method exists for predicting the complete curve. Most difficult is the prediction of the nucleate boiling curve, the transition

J. W. Westwater; J. C. Zinn; K. J. Brodbeck

1989-01-01

204

Hydrothermal synthesis of hydroxyapatite  

NASA Astrophysics Data System (ADS)

A hydrothermal method of synthesizing hydroxyapatite by heating a precipitate, formed by mixing Ca(NO3)2bold dot4H2O and (NH4)2HPO4 with distilled water, in a hydrothermal reactor at 200 C for 24-72 hrs is described. A treatment time of 24 hrs produced single phase (as shown by XRD) hydroxyapatite powder, however for longer treatment times XRD patterns were indicative of the presence of a secondary phase, monetite (CaHPO4). SEM examination of the treated powders displayed particles of rod-like morphology with dimensions 100-500 nm in length and 10-60 nm in diameter. Preliminary results on the use of the particles for the infiltration of dentine tubules are presented.

Earl, J. S.; Wood, D. J.; Milne, S. J.

2006-02-01

205

Core boiling during midloop operation  

SciTech Connect

The reactor coolant system (RCS) water level is reduced during each refueling at some plants. Decreasing the level below the top of the loop piping (midloop operation) may be necessary to work on unisolable RCS loop components. A loss of residual heat removal (RHR) under these conditions can be serious due to the reduced water inventory, air in the RCS, and openings in the RCS loops. Under certain conditions, a loss of RHR could lead to rapid core uncovery and potential fuel damage. Core boiling due to a loss of RHR during midloop operation has received little attention until recently. The transient involves complex phenomena induced by core boiling, such as inventory loss from RCS openings and differences between the downcomer and upper plenum water levels, with the reactor vessel acting like a manometer. These phenomena cannot be easily evaluated without a versatile thermal-hydraulic computer code such as RETRAN. This paper provides an analysis of these phenomena which reveals that the time to core uncovery is shortened by the loss of coolant through RCS openings and the manometer behavior of the reactor vessel water level. This analysis points out some limitations in applying the RETRAN code to this transient.

Fujita, N.; Rice, D.A. (Yankee Atomic Electric Co., Bolton, MA (US))

1991-01-01

206

Hydrothermal reactivity of saponite.  

USGS Publications Warehouse

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

Whitney, G.

1983-01-01

207

21 CFR 872.6710 - Boiling water sterilizer.  

Code of Federal Regulations, 2012 CFR

...2014-04-01 2014-04-01 false Boiling water sterilizer. 872.6710 Section 872...Miscellaneous Devices § 872.6710 Boiling water sterilizer. (a) Identification. A boiling water sterilizer is an AC-powered device...

2014-04-01

208

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

209

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

210

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

211

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

212

AN ATOMIZATION MODEL FOR FLASH BOILING SPRAYS  

Microsoft Academic Search

This paper presents an atomization model for sprays under flash boiling conditions. The automization is represented by the secondary breakup of a bubble\\/droplet system, and the breakup is considered as the result of two competing mechanisms: aerodynamic force and bubble growth. The model was applied to predict the atomization of a hollow-cone spray from a pintle injector under flash boiling

YANGBING ZENG; CHIA-FON F. LEE

2001-01-01

213

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

214

Spray cooling heat-transfer with subcooled trichlorotrifluoroethane (Freon-113) for vertical constant heat flux surfaces  

SciTech Connect

Experiments were done using subcooled Freon-113 sprayed vertically downward. Local and average heat transfers were investigated fro Freon-113 sprays with 40 C subcooling, droplet sizes 200-1250{mu}m, and droplet breakup velocities 5-29 m/s. Full-cone type nozzles were used to generate the spray. Test assemblies consisted of 1 to 6 7.62 cm vertical constant heat flux surfaces parallel with each other and aligned horizontally. Distance between heated surfaces was varied from 6.35 to 76.2 mm. Steady state heat fluxes as high as 13 W/cm{sup 2} were achieved. Dependence on the surface distance from axial centerline of the spray was found. For surfaces sufficiently removed from centerline, local and average heat transfers were identical and correlated by a power relation of the form seen for normal-impact sprays which involves the Weber number, a nondimensionalized temperature difference, and a mass flux parameter. For surfaces closer to centerline, the local heat transfer depended on vertical location on the surface while the average heat transfer was described by a semi-log correlation involving the same parameters. The heat transfer was independent of the distance (gap) between the heated surfaces for the gaps investigated.

Kendall, C.M. [Lawrence Livermore National Lab., CA (United States); Holman, J.P. [Southern Methodist Univ., Dallas, TX (United States). Dept. of Mechanical Engineering

1996-06-06

215

Cody hydrothermal system  

SciTech Connect

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

Heasler, H.P.

1982-01-01

216

Dynamics of explosive boiling of a droplet  

SciTech Connect

The dynamical behavior of the unstable explosive boiling of single droplets (1--2 mm diam) of diethyl ether, pentane, and isopentane at the superheat limit has been exhibited in detail. A+high ambient pressures, boiling consists of normal stable growth of a smooth bubble. At intermediate pressures a transitional regime of stability occurs in which a drop initially vaporizes stably for several milliseconds while incipient instability waves develop on the evaporating interface, then increased heat flux from the host liquid initiates violent boiling near the edge of the remnant volatile liquid. Direct evidence has been obtained that during violently unstable boiling, fine liquid particles are torn from the liquid--vapor interface, generating a mass flux orders of magnitude greater than that characteristic of ordinary boiling. In this regime of transitional stability, one of a number of different possible kinds of disturbances could externally trigger a breakdown to violent instability. After the evaporative instability becomes nonlinear and saturates, the boiling appears quasisteady, with the evaporative front moving into the volatile liquid at a roughly constant velocity. Results obtained by modeling the evaporation wave as a Chapman--Jouguet deflagration show that the temperature at the unstably boiling interface is substantially above the saturated value.

Frost, D.L.

1988-09-01

217

SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities  

SciTech Connect

Graphical abstract: Novel SiC-dopped MCM-41 materials were synthesized by adding silicon carbide suspension in the molecular sieve precursor solvent followed by in situ hydrothermal synthesis. The dopped materials have a wormhole-like mesoporous structure and exhibit enhanced thermal and hydrothermal stabilities. Highlights: {yields} SiC-dopped MCM-41 was synthesized by in situ hydrothermal synthesis of molecular sieve precursor combined with SiC. {yields} The dopped MCM-41 materials show a wormhole-like mesoporous structure. {yields} The thermal stability of the dopped materials have an increment of almost 100 {sup o}C compared with the pure MCM-41. {yields} The hydrothermal stability of the dopped materials is also better than that of the pure MCM-41. -- Abstract: SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N{sub 2} physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 {sup o}C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.

Wang, Yingyong; Jin, Guoqiang; Tong, Xili [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China)] [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China); Guo, Xiangyun, E-mail: xyguo@sxicc.ac.cn [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China)] [State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Taiyuan 030001 (China)

2011-11-15

218

Boiling incipience and nucleate boiling heat transfer of highly-wetting dielectric fluids from electronic materials  

Microsoft Academic Search

An experimental study of pool boiling was conducted using cylindrical heater surfaces of platinum, silicon, silicon dioxide, and aluminum oxide. They were immersed in FC-72 and R-113, saturated at 1-a.t.m. pressure. The effects of fluid and surface material on boiling incipience and on the nucleate boiling curve was investigated. A probabilistic representation was used to present the incipience wall superheat

S. M. You; A. BarCohen; T. W. Simon

1990-01-01

219

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

220

Parable of the Boiled System Safety Professional: Drift to Failure.  

National Technical Information Service (NTIS)

Recall from the Parable of the Boiled Frog, that tossing a frog into boiling water causes the frog to jump out and hop away while placing a frog in suitable temperature water and slowly bringing the water to a boil results in the frog boiling due to not b...

C. H. Shivers

2011-01-01

221

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...

222

Compatibility of Refractory Materials with Boiling Sodium.  

National Technical Information Service (NTIS)

The program employed to determine the compatibility of commercially available refractories with boiling sodium is described. The effects of impurities contained within the refractory material, and their relations with the refractory's physical stability a...

S. A. Meacham

1976-01-01

223

PIV measurements of turbulent jet and pool mixing produced by a steam jet discharge in a subcooled water pool  

Microsoft Academic Search

This experimental research is on the fluid-dynamic features produced by a steam injection into a subcooled water pool. The relevant phenomena could often be encountered in water cooled nuclear power plants. Two major topics, a turbulent jet and the internal circulation produced by a steam injection, were investigated separately using a particle image velocimetry (PIV) as a non-intrusive optical measurement

Yeon Jun Choo; Chul-Hwa Song

2010-01-01

224

Boiling liquid engine cooling system  

SciTech Connect

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 by the radiator into the coolant jacket; an electric fan positioned adjacent the radiator for, upon energization, producing a radiator cooling air flow to promote a condensation function of the radiator; and control means for energizing the electric fan when the temperature of the coolant in the coolant jacket is higher than a predetermined temperature, for controlling the rotation speed of the electric fan by gradually increasing the rotation speed from a low level at the beginning of the fan rotation to a normal level as time proceeds and for deenergizing the electric fan when the temperature of the coolant in the coolant jacket is lower than the predetermined temperature.

Miura, N.; Hayashi, Y.

1987-04-21

225

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

226

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

NASA Astrophysics Data System (ADS)

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

Woo, Kyoungsuk

227

High-boiling benzene radiolysis products  

Microsoft Academic Search

High-boiling (HB) radiolysis products are defined as a mixture of compounds whose boiling point exceeds that of a substance with double the molecular weight of the original molecule. We used cp benzene further purified to remove trace impurities and thoroughly dehydrated. The irradiation was provided by a ⁶°Co \\/gamma\\/ emitter with a dose rate of 4 Gy\\/sec at room temperature.

Zatonskii

1988-01-01

228

En Echelon Hydrothermal Systems  

NASA Astrophysics Data System (ADS)

En echelon hydrothermal systems develop within the porous rocks that surround, in three-dimensions, their distinctive plan-form and cross-sectional basaltic intrusion geometry. Examples that span several (self-similar) spatial scales include the en echelon off-set area of the East Rift Zone of Kilauea Volcano, Hawaii; the Northeast Rift Zone of Mauna Loa Volcano; the intrusive-eruptive fissures of the Krafla Central Volcano, Northeast Iceland; the ensemble of the three Icelandic central volcanoes Theistarekir-Krafla-Fremrinamur; major segments of the East Pacific Rise and the Mid-Atlantic Ridge; and several paleo-hydrothermal systems of the Mesozoic basins of eastern North America, including the Culpeper Basin. An en echelon hydrothermal system comprises two or more en echelon--arranged magma-filled fractures enclosed in a fluid-saturated porous matrix. Blocks of country rock between individual offset fracture segments are similarly porous and fluid-saturated. In 3-D, the system resembles the fan blades of a turbine rotor, with blades (dikes) emanating from a deep "master" fracture and turning smoothly in response to the local variations in the least compressive regional stress component. The primary geometric, hydrologic and thermal attributes of the system (on a horizontal plane) include dike thickness, dike-to-dike offset and overlap, the (initial) intrusion temperature, duration of magma flow, dike widths and lengths, the mean seepage velocity of regional subsurface aqueous fluid flow, and the mean flow azimuth in relationship to the plan-form geometry of the en echelon array. Finite element single phase models in horizontal cross-section have been developed for dike widths of 100 m, dike lengths of 1,500 m, overlaps of 500 m, dike-to-dike offsets of 500 m, intrusion temperatures of 1,200 C, horizontal seepage fluxes imposed at the sides of ~ 1,000 g cm-2 yr-1, and a matrix permeability of 10-14 m2. The regional flow field has been parameterized in dike-orthogonal, dike-parallel, and 45 degree angles of attack with respect to the major axes of the individual dikes within the en echelon array. Depending on the magnitudes and geometric arrangement of key system attributes, an en echelon hydrothermal system may either act as an efficient thermal radiator, effectively shedding heat to the surroundings, or may it act as an effective heater, thermally enhancing the environment between neighboring dikes in 3-D. Conditions that promote the efficient loss of heat include thin dikes of short length, large dike-to-dike offset, high matrix fluid velocities, and regional flow azimuths that are orthogonal to the individual dikes. Conditions that promote differential heating between the dikes include wide dikes with maximal overlap and minimal offset, low regional flow velocities and "angles of attack" of the regional flow field that provide for maximum hydrodynamic "shelter" for individual dikes within the interior of the en echelon array.

Ryan, M. P.; Carr, P. M.; Daniels, D. L.; Sutphin, D. M.

2005-12-01

229

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

230

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

NASA Astrophysics Data System (ADS)

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

Revellin, R.; Thome, J. R.

2007-04-01

231

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

232

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; Stefnsson, Andri

2011-05-01

233

Cryogenic Boil-Off Reduction System  

NASA Astrophysics Data System (ADS)

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

Plachta, David W.; Guzik, Monica C.

2014-03-01

234

S, Sr, and Pb isotopic systematics of hydrothermal chimney precipitates from the Eastern Manus Basin, western Pacific: Evaluation of magmatic contribution to hydrothermal system  

NASA Astrophysics Data System (ADS)

Sulfur, strontium, and lead isotopic analyses were performed on chimneys from the hydrothermal vent fields (the PACMANUS and Susu knolls) in the eastern Manus back arc basin. Lead isotope composition varies in a narrow range (206Pb/204Pb = 18.75-18.78, 207Pb/204Pb = 15.51-15.54, and 208Pb/204Pb = 38.31-38.40). Strontium isotopic ratios (87Sr/86Sr) of sulfate minerals vary from 0.7051 to 0.7077, falling between those of seawater (0.7090) and the hydrothermal fluid end-member (0.7050). The ?34S values of the chimneys are -8.0 to -3.9 for the Susu knolls sulfide, +1.0 to +4.3 for the PACMANUS sulfides, and +7.4 to +20.6 for sulfate. The Susu knolls sulfides have the lowest values so far reported for volcanic-hosted massive sulfides from modern seafloor. The low ?34S values of sulfates and sulfides cannot be explained by a simple seawater circulation model without an additional source of light sulfur. This is also supported by the presence of sulfate in hydrothermal end-member fluid indicated by sulfur and strontium isotopic ratios in chimney sulfates. Biogenic sulfur and/or oxidation of H2S after boiling are excluded from the possible sources of light sulfur because of the lack of sediment cover and nonequilibrium in isotopic fractionation by boiling at seafloor. Disproportionation of magmatic SO2, introduced into hydrothermal system through preeruptive degassing, is the most plausible mechanism for the observed low ?34S values. The lighter ?34S values and more radiogenic lead isotope compositions of the Susu knolls samples indicate that magmatic degassing was more vigorous at the Susu knolls than PACMANUS.

Kim, Jonguk; Lee, Insung; Lee, Kyeong-Yong

2004-12-01

235

A review of film boiling at cryogenic temperatures.  

NASA Technical Reports Server (NTRS)

Film boiling occurs in the quenching of metals, the chilling of biological species, the regenerative cooling of rockets, and the cooling down of a cryogenic fuel tank. Occasionally film boiling is also found in a nuclear reactor or in a cryomagnet. Aspects of film boiling involving an unconstrained liquid mass are considered, giving attention to the evaporation time, the Leidenfrost temperature, solid-liquid contacts, the thermal properties of the solid, effects of coating or scale, wettability, the metastable condition, and the velocity effect on drops. Developments discussed with regard to pool boiling are related to vertical surfaces, film boiling from horizontal surfaces, film boiling from a horizontal cylinder, film boiling from a sphere, and film boiling of helium. Processes of film boiling in a channel are also analyzed.

Hsu, Y. Y.

1972-01-01

236

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

237

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

USGS Publications Warehouse

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

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

1992-01-01

238

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

239

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.

Brown, Joseph; Sobsey, Mark D.

2012-01-01

240

Boiling as household water treatment in Cambodia: a longitudinal study of boiling practice and microbiological effectiveness.  

PubMed

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

2012-09-01

241

The boiling point of stratospheric aerosols.  

NASA Technical Reports Server (NTRS)

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

Rosen, J. M.

1971-01-01

242

Nucleate pool boiling of hydrocarbon mixtures  

SciTech Connect

The Schlunder method can be correctly used to predict boiling heat transfer coefficient of multicomponent hydrocarbon mixtures. The method was tested against experimental mixtures containing up to five components. The Stephan-Abdelsalam correlation can be used to calculate a ''pseudo-single component'' boiling heat transfer coefficient for a mixture using weighted properties. The effective temperature driving force term and the high mass flux correction term in the Schlunder formulation are empirically adjusted to improve the accuracy of prediction. Predictions of the Schlunder method are sensitive to the VLE calculations. The UNIFAC method is used in this study for reasons discussed in the paper.

Sardesai, R.G.; Palen, J.W.; Thome, J.

1986-01-01

243

CFD analysis for thermal mixing in a subcooled water tank under a high steam mass flux discharge condition  

Microsoft Academic Search

A Computational Fluid Dynamics (CFD) analysis for a thermal mixing test was performed for 30s to develop the methodology for a numerical analysis of the thermal mixing between steam and subcooled water and to apply it to Advanced Power Reactor 1400MWe (APR1400). In the CFD analysis, the steam condensation phenomenon by a direct contact was simulated by the so-called condensation

Hyung Seok Kang; Chul Hwa Song

2008-01-01

244

Hydrothermal Industrialization: Direct Heat Development. Final Report.  

National Technical Information Service (NTIS)

A description of hydrothermal resources suitable for direct applications, their associated temperatures, geographic distribution and developable capacity are given. An overview of the hydrothermal direct-heat development infrastructure is presented. Devel...

1982-01-01

245

21 CFR 872.6710 - Boiling water sterilizer.  

Code of Federal Regulations, 2010 CFR

...HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710...boiling water. The device is intended to sterilize dental and surgical instruments by submersion in the boiling water in the...

2010-04-01

246

21 CFR 872.6710 - Boiling water sterilizer.  

Code of Federal Regulations, 2010 CFR

...HUMAN SERVICES (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Miscellaneous Devices § 872.6710...boiling water. The device is intended to sterilize dental and surgical instruments by submersion in the boiling water in the...

2009-04-01

247

Nucleate Pool Boiling of Nitrogen from Artificial Cavities.  

National Technical Information Service (NTIS)

Pool boiling heat transfer of nitrogen from artificial cavities was investigated. Boiling was from circular, one-inch diameter horizontal mirror finished copper plates. The single artificial cavity surfaces investigated were: a drilled 0.0043 inch diamete...

J. A. Moulson

1967-01-01

248

Strength analysis of CARR-CNS with crescent-shape moderator cell and helium sub-cooling jacket covering cell  

NASA Astrophysics Data System (ADS)

The new type of the moderator cell was developed for the cold neutron source (CNS) of the China Advanced Research Reactor (CARR) which is now being constructed at the China Institute of Atomic Energy in Beijing. A crescent-shape moderator cell covered by the helium sub-cooling jacket is adopted. The structure of the moderator cell is optimized by the stress FEM analysis. A crescent-shape would help to increase the volume of the moderator cell for fitting it to the four cold neutron guide tubes, even if liquid hydrogen, not liquid deuterium, was used as a cold moderator. The helium sub-cooling jacket covering the moderator cell removes the nuclear heating of the outer shell wall of the cell. It contributes to reduce the void fraction of liquid hydrogen in the outer shell of the moderator cell. Such a type of a moderator cell is suitable for the CNS with higher nuclear heating. The cold helium gas flows down first into the helium sub-cooling jacket and then flows up to the condenser. The theory of the self-regulation suitable to the thermo-siphon type of the CNS is also applicable and validated.

Yu, Qingfeng; Feng, Quanke; Kawai, Takeshi; Shen, Feng; Yuan, Luzheng; Cheng, Liang

2005-12-01

249

Submarine Hydrothermal Systems: Insights from 3D and Multiphase Simulations  

NASA Astrophysics Data System (ADS)

In this talk we present some new insights into black smoker hydrothermal systems using a state-of-the-art finite element-finite volume fluid flow simulator, recently developed in our group at ETH. First of all, we present fully-transient multi-phase simulations of mid-ocean ridge hydrothermal systems that include the full complexity of the H2O-NaCl phase diagram. A series of 2D simulations were performed to study the influence of permeability and ocean depth on flow patterns and spatial and transient evolution of venting fluids. Although geometrically simple, our simulations accurately predict the range of salinities observed in natural systems. In addition, they reveal new dynamical features of the denser brine phase. In low-pressure systems at sim1500m water-depth, phase-separation occurs in boiling zones stretching from the bottom of the hydrothermal cell to the seafloor. Low-salinity vapors and high-salinity brines can vent simultaneously, and transient variations in vent-fluid salinities can be rapid. In high-pressure systems at roughly sim3500m water-depth, phase-separation occurs by brine condensation and is limited to the region close to the underlying magma chamber. Vent fluids consist of a low-salinity vapor mixed with a seawater-like fluid. Therefore, vent salinities from these systems are much more uniform in time and always below seawater salinity as long as phase-separation occurs in the subseafloor. Only by shutting down the heat source can, in the high pressure case, the brine be mined, resulting in larger than seawater salinities. These results are in good agreement with long-term observations from shallow and deep natural systems. Our results show that whether phase-separation occurs by boiling or by condensation is a first-order control on vent-fluid salinity, and especially its variation in space and time. Next to these 2D simulations, we present results from 3D simulations, which became computationally feasible by parallelizing the code. In 3D, convection self-organizes into pipe-like upflow surrounded by narrow and relatively warm downflow zones. We show that this configuration optimizes the heat output of the system. In this talk, we will present new results from simulations using different geologic structures, including a high-permeability axial plane, a highly permeable basaltic layer and mid-ocean ridge normal faults.

Coumou, D.; Driesner, T.; Weis, P.; Heinrich, C. A.

2009-04-01

250

Sediment volcanoes and hydrothermal vent complexes in pierced sedimentary basins  

NASA Astrophysics Data System (ADS)

Sedimentary basins with a considerable amount of piercement structures can be classified as pierced basins. Piercement structures include hydrothermal vent complexes and mud volcanoes. The need to distinguish between sedimentary basins with and without significant amounts of piercement structures arise when considering the importance of these structures for the basin hydrology. We have studied sedimentary basins in South Africa (the Karoo basin), in Azerbaijan (the South Caspian basin), and in the Norwegian Sea (the Vring and Mre basins) to characterize and constrain the effect of piercing processes. Our approach integrates seismic data, fieldwork, well studies, petrography, geochemistry, and numerical modelling. We have mapped and studied several hundred hydrothermal vent complexes in the Karoo, Vring and Mre basins. These piercement structures were formed as a consequence of intrusions of magmatic melt in sills and dikes. Numerical modelling suggest that creation of hydrothermal vent complexes may partly be related to overpressure generation as a consequence of boiling of pore fluids and hydrofracturing on a very short timescale after sill emplacement (10's of years). Seep carbonates, veins with petroleum, and mounds above the vent complexes suggest that the structures act as permeability zones after their formation. Several hundred active mud volcanoes are located in Azerbaijan. The tectonics in this region is very dynamic, with extreme sediment accumulation (5 km in 5 Ma). The mud volcanoes are commonly located on anticlines and are associated with petroleum reservoirs. The formation of these piercement structures is related to overpressure generated by teconic forces and maturation. In summary, piercement structures are present both in volcanic and non-volcanic sedimentary basins. However, the composition of the piercement structures is similar in both basin settings, suggesting that they are formed by similar physical processes. Boiling of pore fluids is important in volcanic basins, as the volcanic intrusions heat the pore fluids in the sedimentary strata, whereas the piercing process is controlled by overpressure resulting from factors such as rapid burial of clays, decomposition of organic material, and tectonic compression in non-volcanic basins.

Planke, S.; Svensen, H.; Jamtveit, B.

2003-04-01

251

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

252

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

253

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

254

Structure of a seafloor hydrothermal system in volcanic sediment: distribution of hydrothermal clay minerals, at the Iheya North Knoll, Okinawa Trough  

NASA Astrophysics Data System (ADS)

Detailed investigation of clay minerals in hydrothermal fields provides fundamental information for understanding the physical and geochemical conditions within a hydrothermal system. Moreover, stable isotope geochemistry of clay minerals provides constraints on formation temperature. We investigated the distribution of clay minerals by XRD and TEM-EDS in a seafloor hydrothermal field at Iheya North Knoll in the Okinawa Trough, using cored sediment obtained from the Integrated Ocean Drilling Program (IODP) Expedition 331. The chemical composition and isotope values of the representative clay minerals were analyzed to obtain information on the hydrothermal system beneath the seafloor. Vertically, two different clay mineral facies are present. The boundary between the facies was identified at 6 mbsf (meters below the seafloor) at Site C0013 (100 m east of hydrothermal mound) and at 23 mbsf at Site C0014 (450 m east of the mound). In the lower facies (6 - 28 mbsf and 45 mbsf at Site C0013, 23 - 114 mbsf at Site C0014), Mg-chlorite and/or Mg-chlorite-smectite mixed layer minerals are dominant. They are associated with sericite in deeper parts (45 mbsf at Site C0013 and 38 - 114 mbsf at Site C0014). The ?18O values of the clays range from +1.5 to +4.7 (VSMOW) and the formation temperatures of the Mg-chlorite are estimated to be 230 - 300 C, assuming a value from 0 to +1.5 for ?18Owater. The original sediment in the Iheya North Knoll is considered to have been volcanic of felsic chemical composition, so alteration to Mg-rich chlorite would require supply of substantial amount of Mg. Abundant formation of Mg-chlorite is attributed to mixing of hydrothermal fluid and seawater. In the upper facies at both sites, Al-rich clay minerals (kaolinite and montmorillonite) dominate. The ?18O values of clays range between +9.6 and +13.3 and formation temperatures are estimated to range between 120 - 160 C. As kaolinite formation is favorable under acidic conditions, the kaolinite may be related to the vapor phase component enriched in CO2 and H2S, which would be generated by boiling of the hydrothermal fluid below the seafloor. In summary, occurrence of different facies of hydrothermal clay minerals reflects substantial variation in both temperature and chemical conditions between the upper and lower sediment layer. This difference may be related to discrete fluid flow within these sediment layers.

Miyoshi, Y.; Ishibashi, J.; Faure, K.; Uehara, S.

2012-12-01

255

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

256

Big Bubbles in Boiling Liquids: Students' Views  

ERIC Educational Resources Information Center

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

Costu, Bayram

2008-01-01

257

Boiling crisis as a critical phenomenon.  

PubMed

We present the first experimental study of intermittency and avalanche distribution during a boiling crisis. To understand the emergence of power law statistics we propose a simple spin model capturing the measured critical exponent. The model suggests that behind the critical heat flux is a percolation phenomenon involving drying-rewetting competition close to the hot surface. PMID:23003280

Lloveras, P; Salvat-Pujol, F; Truskinovsky, L; Vives, E

2012-05-25

258

Pressure balance under hydrothermal conditions  

NASA Astrophysics Data System (ADS)

Low pressure, low temperature growth of potassium titanyl phosphate (KTP) crystals, the material of choice for certain kinds of laser eye surgery apparatus and other applications, requires hydrothermal growth in pressure balance noble metal cans. This paper discusses the problem of pressure balancing the Au cans used for hydrothermal KTP growth. The P-V-T behavior of the pressure balance medium (H2O) and the growth medium (KTP saturated K2HPO4) are described and the source of the 'dimples' in growth cans is explained and remediation strategies are suggested.

Laudise, R. A.; Bridenbaugh, P. M.; Iradi, T.

1994-06-01

259

Hydrothermal scheduling based Lagrangian relaxation approach to hydrothermal coordination  

Microsoft Academic Search

This paper presents an improved Lagrangian relaxation based hydrothermal coordination algorithm. By using Lagrangian multipliers to relax system-wide demand and reserve requirements, the problem is decomposed into thermal and hydro subproblems. The thermal subproblem is solved by using dynamic programming without discretizing generation levels. Instead of solving the hydro subproblems independently as done in the standard Lagrangian relaxation formulation, the

M. S. Salam; K. M. Nor; A. R. Hamdam

1998-01-01

260

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

261

Hydrothermal synthesis of perovskite nanotubes.  

PubMed

A low-temperature hydrothermal reaction has been utilized to generate crystalline barium titanate and strontium titanate nanotubes, which have been characterized by means of X-ray diffraction and transmission electron microscopy, coupled with energy dispersive X-ray analysis. PMID:12613636

Mao, Yuanbing; Banerjee, Sarbajit; Wong, Stanislaus S

2003-02-01

262

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 385C to 150C. 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

263

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.

Grounds, Alex; Still, Richard; Takashina, Kei

2012-01-01

264

Enhanced droplet control by transition boiling.  

PubMed

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

265

Enhanced Droplet Control by Transition Boiling  

NASA Astrophysics Data System (ADS)

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.

Grounds, Alex; Still, Richard; Takashina, Kei

2012-10-01

266

Nanowires for enhanced boiling heat transfer.  

PubMed

Boiling is a common mechanism for liquid-vapor phase transition and is widely exploited in power generation and refrigeration devices and systems. The efficacy of boiling heat transfer is characterized by two parameters: (a) heat transfer coefficient (HTC) or the thermal conductance; (b) the critical heat flux (CHF) limit that demarcates the transition from high HTC to very low HTC. While increasing the CHF and the HTC has significant impact on system-level energy efficiency, safety, and cost, their values for water and other heat transfer fluids have essentially remained unchanged for many decades. Here we report that the high surface tension forces offered by liquids in nanowire arrays made of Si and Cu can be exploited to increase both the CHF and the HTC by more than 100%. PMID:19152275

Chen, Renkun; Lu, Ming-Chang; Srinivasan, Vinod; Wang, Zhijie; Cho, Hyung Hee; Majumdar, Arun

2009-02-01

267

Hydrothermal brecciation in the Jemez fault zone, Valles Caldera, New Mexico: Results from continental Scientific Drilling Program core hole VC-1  

NASA Astrophysics Data System (ADS)

An unusual breccia sequence penetrated in the lower 30 m of Continental Scientific Drilling Program core hole VC-1 (total depth 856 m) records a complex hydrothermal history culminating in hydraulic rock rupture and associated alteration at the edge of the Quaternary Valles caldera. The breccias, both tectonic and hydrothermal in origin, were formed in the Jemez fault zone, near the intersection of this major regional structure with the caldera's ring-fracture margin. Tectonic breccias in the sequence are contorted, crushed, and sheared. Coexisting hydrothermal breccias lack such frictional textures but display matrix flow foliation and prominent clast rounding, features characteristic of fluidization. These hydrothermal breccias were intensely altered, during at least five major stages, to quartz-illite-phengite-pyrite aggregates; traces of molybdenite occur locally. This assemblage indicates interaction with hydrothermal fluid at temperatures in excess of 200C. The extrapolated present maximum temperature of 184C in the breccia zone therefore represents considerable cooling since these phases were formed. Fluid inclusions in the breccias also preserve evidence of the prior passage of hotter fluids. The inclusions are principally two phase, liquid rich, secondary in origin, and concentrated in hydrothermal quartz. Older, high-salinity inclusions, unrelated to brecciation, homogenize in the temperature range 189-246C. Younger inclusions, in part of interbreccia origin, are low-salinity and homogenize in the temperature range 230-283C; locally coexisting liquid- and vapor-rich inclusions document periodic boiling of the dilute fluids. These fluid-inclusion data, along with the probable age of the hydrothermal breccias (<1.5 Ma), the assumed depth at which they developed (about 515 m), and the contemporaneous state of stress (extensional) can be combined to model hydrothermal brecciation at the VC-1 site. The minimum fluid pressure (Pfr) required to hydrofracture these rocks was probably about 7.5 MPa (0.0146 MPa/m). A boiling point versus depth curve based on these Pfr values graphically defines the physical conditions prevailing when the breccias were formed. When fluid pressure at the assumed depth of brecciation exceeded that curve, in response to rapid release of confining pressure possibly augmented by renewed heating, flashing hydrothermal fluid fractured the enclosing rock. Large overpressures, most likely induced by sudden seismic cracking of a hydrothermally sealed portion of the Jemez fault zone, led to local fluidization of the resulting breccias. Late quartz veining, hydrothermal alteration, and molybdenite mineralization were probably produced by the fluids responsible for brecciation.

Hulen, Jeffrey B.; Nielson, Dennis L.

1988-06-01

268

Explosive Boiling of a Depressurized Volatile Liquid  

Microsoft Academic Search

\\u000a The explosive boiling that occurs when a pressure-liquefied gas is suddenly vented to the atmosphere has been investigated\\u000a experimentally at small scale. The test liquid (refrigerant-22), initially in equilibrium with its vapor, is suddenly depressurized\\u000a by bursting a foil diaphragm. The competition between the rates of vaporization and venting can lead to substantial repressurization\\u000a within the vessel. The influence of

R. Barbone; D. L. Frost; A. Makris; J Nerenberg

269

Fundamental Boiling and RP-1 Freezing Experiments  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

270

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

271

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

272

Stability monitoring for boiling water reactors  

NASA Astrophysics Data System (ADS)

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

Cecenas-Falcon, Miguel

1999-11-01

273

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

SciTech Connect

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

Liu, Hong, E-mail: liuhong@shu.edu.c [Department of Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai 200444 (China); Wang, Mengyang [Department of Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai 200444 (China); Hu, Hongjiu [College of Science, Shanghai University, 149 Yanchang Road, Shanghai 200072 (China); Liang, Yuguang; Wang, Yong; Cao, Weiran [Department of Chemical Engineering, Shanghai University, 99 Shangda Road, Shanghai 200444 (China); Wang, Xiaohong [Institute of Nano Micro Energy, Shanghai University, 99 Shangda Road, Shanghai 200444 (China)

2011-03-15

274

Diversity of Archaeal Consortia in an Arsenic-Rich Hydrothermal System  

NASA Astrophysics Data System (ADS)

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 (85C), arsenic concentrations at 0.5 mM, and inorganic carbon concentrations as low as 0.02mM. Yet many of El Tatio's hundred plus hydrothermal features are associated with extensive microbial mat communities. Recent work has shown phylogenetic variation in the communities that correlates to variations in water chemistry between features. MPN analysis indicates variations in metabolic function between hydrothermal features, such as the ability of the community to fix nitrogen, and the presence of methanogens within the community. Methanogenic archaea, which are typical of hydrothermal environments, are found in very few of the sampled hydrothermal features at El Tatio. MPN enumeration shows that nonspecific microbial mat samples from sites with dissolved methane contain 106 cells of methanogenic archaea per gram while non-specific samples from sites lacking dissolved methane contain 100 cells per gram or less. An acetylene assay showed evidence for nitrogen fixation in a sample associated with methanogenesis, but microbial transformation of acetylene to ethylene did not occur in non-methanogenic sites. More specific sampling of microbial mats indicates that methanogenic archaea are dominated by microorganisms within the genus Methanospirillum and Methanobrevibacter. These microbes are associated with a number of unclassified archaea in the class Thermoplasmata Halobacteriales, and unclassifiec Crenarchaeota. In addition, preliminary results include an unclassified Thaumarchaeota clone, a member of the recently proposed third archaeal phylum Thaumarchaeota. Nonspecific microbial mat sample from a non- methanogenic site included only Crenarchaeal clones within the Desulfurococcales order of Thermoprotei.

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

2008-12-01

275

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- 300C) 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 (150-400C). 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

276

Hydrothermal synthesis of zirconia nanomaterials  

Microsoft Academic Search

Yttria-stabilised zirconia powders and films have been obtained from Zr(IV) peroxides by hydrothermal crystallisation at temperatures in the range 125200C. The thermodynamic evaluation evidenced that formation of Zr(OH)5? in H2O2 solutions increases solubility of Zr (IV) hydrated species and improves the kinetics of the new phase formation by the solubilisation-reprecipitation process. Powders with crystallite sizes in the range 622 nm

R. R Piticescu; C Monty; D Taloi; A Motoc; S Axinte

2001-01-01

277

A review on boiling heat transfer enhancement with nanofluids  

PubMed Central

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.

2011-01-01

278

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

279

Effect of surface particle interactions during pool boiling of nanofluids  

Microsoft Academic Search

The pool boiling characteristics of nanofluids is affected by the relative magnitudes of the average surface roughness and the average particle diameter. In the present work, an attempt has been made to study the interactions between the nanoparticles and the heater surface. The experimental methodology accounts for the transient nature of the boiling phenomena. The boiling curves of electro-stabilized Al2O3

G. Harish; V. Emlin; V. Sajith

2011-01-01

280

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

281

Experimental Study of Heat Transfer from Stainless Steel Foil in He II during Film Boiling State  

SciTech Connect

He II film boiling is of both academic and applied interests. However, the information about film boiling heat transfer in He II is still insufficient and needs further investigation. In the present study, a thin stainless steel foil heater (10 {mu} m thick) is used to cause boiling in He II. The heater temperature is measured to evaluate the heat transfer performance of He II film boiling under different thermal conditions. The pressure and the heater surface temperature oscillations induced by the film boiling are also simultaneously measured. The heat transfer coefficients of three kinds of boiling states: noisy film boiling, transition boiling and silent film boiling, are obtained in the present study.

Zhang, P. [Institute of Engineering Mechanics and Systems, University of Tsukuba, Tsukuba, 305-8573 (Japan); Institute of Refrigeration and Cryogenics, Shanghai Jiao Tong University, Shanghai, 200030 (China); Murakami, M. [Institute of Engineering Mechanics and Systems, University of Tsukuba, Tsukuba, 305-8573 (Japan)

2004-06-23

282

Low-pressure transient flow film boiling in vertically oriented rod bundles  

Microsoft Academic Search

Flow film boiling heat transfer data from Semiscale Mod-3 gravity feed reflood experiments have been compared to existing film boiling correlations. The existing film boiling correlations were found to be inadequate for calculating Semiscale rod bundle results in the low void fraction region. Therefore, a new correlation for flow film boiling was developed. The new correlation is applicable for boiling

G. G. Loomis; R. W. Shumway

1983-01-01

283

Nonlinear dynamics of boiling water reactors  

SciTech Connect

Recent stability tests in Boiling Water Reactors (BWRs) have indicated that these reactors can exhibit the special nonlinear behavior of following a closed trajectory called limit cycle. The existence of a limit cycle corresponds to an oscillation of fixed amplitude and period. During these tests, such oscillations had their amplitudes limited to about +- 15% of the operating power. Since limit cycles are fairly insensitive to parameter variations, it is possible to operate a BWR under conditions that sustain a limit cycle (of fixed amplitude and period) over a finite range of reactor parameters.

March-Leuba, J.; Cacuci, D.G.; Perez, R.B.

1983-01-01

284

Understanding the boiling water reactor limit cycle  

SciTech Connect

This paper presents an interpretation of the physical mechanisms involved in the development of limit cycle oscillations in boiling water reactors (BWRs). Based on this interpretation, approximate correlations for some oscillation parameters are developed and shown to be largely independent of the particular reactor operating condition. The stability of the limit cycle is also studied in this paper. It is shown that the BWR limit cycle may become unstable and bifurcate. The bifurcation process leads to aperiodic (chaotic) behavior of the reactor power and causes the peak oscillation powers to be larger than those from a nonbifurcated limit cycle. 7 refs., 6 figs., 1 tab.

March-Leuba, J.

1989-01-01

285

Uniform Mems Chip Temperatures in the Nucleate Boiling Heat Transfer Region by Selecting Suitable, Medium Boiling Number Range  

Microsoft Academic Search

The not only lower but also uniform MEMS chip temperatures can be reached by selecting suitable boiling number range that ensures the nucleate boiling heat transfer. In this article, boiling heat transfer experiments in 10 silicon triangular microchannels with the hydraulic diameter of 155.4 ?m were performed using acetone as the working fluid, having the inlet liquid temperatures of 2440C,

J. L. Xu; Y. H. Gan

2007-01-01

286

Large-scale in situ heater tests for hydrothermal characterization at Yucca Mountain  

SciTech Connect

To safely and permanently store high-level nuclear waste, the potential Yucca Mountain repository site must mitigate the release and transport of radionuclides for tens of thousands of years. In the failure scenario of greatest concern, water would contact a waste package, accelerate its failure rate, and eventually transport radionuclides to the water table. Our analyses indicate that the ambient hydrological system will be dominated by repository-heat-driven hydrothermal flow for tens of thousands of years. In situ heater tests are required to provide an understanding of coupled geomechanical-hydrothermal-geochemical behavior in the engineered and natural barriers under repository thermal loading conditions. In situ heater tests have been included in the Site Characterization Plan in response to regulatory requirements for site characterization and to support the validation of process models required to assess the total systems performance at the site. Because of limited time, some of the in situ tests will have to be accelerated relative to actual thermal loading conditions. We examine the trade-offs between the limited test duration and generating hydrothermal conditions applicable to repository performance during the entire thermal loading cycle, including heating (boiling and dry-out) and cooldown (re-wetting). For in situ heater tests to be applicable to actual repository conditions, a minimum heater test duration of 6-7 yr (including 4 yr of full-power heating) is required.

Buscheck, T.A.; Wilder, D.G.; Nitao, J.J.

1993-01-01

287

Hydrothermal alteration in the Reykjanes geothermal system: Insights from Iceland deep drilling program well RN-17  

NASA Astrophysics Data System (ADS)

The Reykjanes geothermal system is a seawater-recharged hydrothermal system that appears to be analogous to seafloor hydrothermal systems in terms of host rock type and low water/rock alteration. The similarities make the Reykjanes system a useful proxy for seafloor vents. At some time during the Pleistocene, the system was dominated by meteoric water recharge, and fluid composition at Reykjanes has evolved through time as a result of changing proportions of meteoric water influx as well as differing pressure and temperature conditions. The purpose of this study is to characterize secondary mineralization, degree of metasomatic alteration, and bulk composition of cuttings from well RN-17 from the Reykjanes geothermal system. The basaltic host rock includes hyaloclastite, breccia, tuff, extrusive basalt, diabase, as well as a marine sedimentary sequence. The progressive hydrothermal alteration sequence observed with increasing depth results from reaction of geothermal fluids with the basaltic host rock. An assemblage of greenschist facies alteration minerals, including actinolite, prehnite, epidote and garnet, occurs at depths as shallow as 350 m; these minerals are commonly found in Icelandic geothermal systems at temperatures above 250 C (Bird and Spieler, 2004). This requires hydrostatic pressures that exceed the present-day depth to boiling point curve, and therefore must record alteration at higher fluid pressures, perhaps as a result of Pleistocene glaciation. Major, minor, and trace element profiles of the cuttings indicate transitional MORB to OIB composition with limited metasomatic shifts in easily mobilized elements. Changes in MgO, K 2O and loss on ignition indicate that metasomatism is strongly correlated with protolith properties. The textures of alteration minerals reveal alteration style to be strongly dependent on protolith as well. Hyaloclastites are intensely altered with calc-silicate alteration assemblages comprising calcic hydrothermal plagioclase, grandite garnet, prehnite, epidote, hydrothermal clinopyroxene, and titanite. In contrast, crystalline basalts and intrusive rocks display a range in alteration intensity from essentially unaltered to pervasive and nearly complete albitization of igneous feldspar and uralitization of clinopyroxene. Hydrothermal anorthite (An92-An98) occurs in veins in the most altered basalt cuttings and is significantly more calcic than igneous feldspar (An48-An79). Amphibole compositions change from actinolite to hornblende at depth. Hydrothermal clinopyroxene, which occurs in veins, has greater variation in Fe content and is systematically more calcic than igneous pyroxene and also lacks uralitic textures. Solid solutions of prehnite, epidote, and garnet indicate evolving equilibria with respect to aluminum and ferric iron.

Marks, Naomi; Schiffman, Peter; Zierenberg, Robert A.; Franzson, Hjalti; Fridleifsson, Gudmundur .

2010-01-01

288

(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

289

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

290

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.

291

Numerical modeling of oceanic crustal hydrothermal systems  

Microsoft Academic Search

The oceanic crust is a complex rock-mineral formation which extends up to several kilometers below the sea floor and covers laterally about two thirds of the planet. Hydrothermal circulation within the crust is driven by magmatic sources and carried by the fluid residing in pores and cracks. Hydrothermal advection transfers about one quarter of the Earth's total heat power from

Konstantin Latychev

2000-01-01

292

EFFECTS OF EXTRATERRESTRIAL HYDROTHERMAL PROCESSES IN CHONDRITES  

Microsoft Academic Search

Hydrothermal reactions in terrestrial geological processes may be defined in a simplified form as those that cause numerous alterations of earlier formed rocks and minerals due to the action of hot aqueous solutions, usually in a postmagmatic stage. Under extraterrestrial conditions hydrothermal processes should occur probably less often because of the lack of the environments rich in such solutions. Only

Andrzej MANECK

293

Hydrothermal epitaxy of perovskite thin films  

Microsoft Academic Search

This work details the discovery and study of a new process for the growth of epitaxial single crystal thin films which we call hydrothermal epitaxy. Hydrothermal epitaxy is a low temperature solution route for producing heteroepitaxial thin films through the use of solution chemistry and structurally similar substrates. The application of this synthesis route has led to the growth of

Allen T. Chien

1998-01-01

294

TUNABLE HYDROTHERMAL SYNTHESIS OF BAMNO3 NANOCRYSTALS  

Microsoft Academic Search

Although synthesis of nanooxides has been attempted by many different and innovative chemical approaches, further research is still needed to develop inexpensive and mass- production methods capable to provide pure products and thus make nanocrystals' technological applications viable. Hydrothermal synthesis matches these requirements. Under hydrothermal conditions, where an aqueous reaction mixture is heated above 100 C in a sealed reaction

Ana Querejeta; Marina Parras; Aurea Varela; Jose Gonzlez-Calbet

295

Transient nucleate pool boiling in microgravity: Some initial results  

Microsoft Academic Search

Variable gravity provides an opportunity to test the understanding of phenomena which are considered to depend on buoyancy, such as nucleate pool boiling. The active fundamental research in nucleate boiling has sought to determine the mechanisms or physical processes responsible for its high effectiveness, manifested by the high heat flux levels possible with relatively low temperature differences. Earlier research on

Herman Merte Jr.; H. S. Lee; J. S. Ervin

1994-01-01

296

Main Results of NaK Alloy Boiling Investigation  

Microsoft Academic Search

Boiling experiments on eutectic sodium-potassium alloy in the model of fast reactor subassembly under conditions of low-velocity circulation carried out at the IPPE call for further investigations into numerical modeling of the process. The paper presents analysis of pin bundle liquid metal boiling, stages of the process, its characteristics (wall temperature, coolant temperature, flow rate. pressure void fraction and others),

G. A. Sorokin; G. P. Bogoslovskaya; E. F. Ivanov; A. P. Sorokin

2002-01-01

297

Explosive vaporization of superheated liquids by boiling fronts  

Microsoft Academic Search

Up to 2 l of metastable propane, butane, refrigerant R-134a and water were released from glass receptacles without nucleation sites and expanded to atmospheric pressure over a range of initial superheats created by the sudden depressurization. Above a certain superheat threshold, vaporization occurred only in a thin surface zone of intense boiling and liquid fragmentation. This boiling front traveled from

P Reinke; G Yadigaroglu

2001-01-01

298

a New Analytical Model for Heat Transfer in Pool Boiling  

Microsoft Academic Search

In this paper, dependence of active nucleation site density on boiling surfaces are developed. For pool boiling heat transfer, a mathematical model is derived based on statistical treatment using the probability density function of the cavity mouth radius and existing correlation for active nucleation site density, the volume of single bubble at departure, the bubble departure diameter and the bubble

Boqi Xiao

2010-01-01

299

Thermoelectric generator utilizing boiling-condensation (experiment and modeling)  

Microsoft Academic Search

A thermoelectric generator utilizing boiling and condensation of thermal medium circulating between a boiler and condensers was proposed in this study. Fuluorinert (FC5312) was used as the thermal medium (working fluid). A vertical tube type boiler with an outside forced convective heat transfer and an inside natural convective boiling was chosen. In order to increase the hot side temperature of

Ren Cai Chu; Kanichi KADOTANI; Toshiya SHINTANI; Toshinobu TANIMURA; Tsutomu HATANAKA; S. Nishio

2003-01-01

300

Boiling treatment of ABS and PS plastics for flotation separation.  

PubMed

A new physical method, namely boiling treatment, was developed to aid flotation separation of acrylonitrile-butadiene-styrene (ABS) and polystyrene (PS) plastics. Boiling treatment was shown to be effective in producing a hydrophilic surface on ABS plastic. Fourier Transform Infrared analysis was conducted to investigate the mechanism of boiling treatment of ABS. Surface rearrangement of polymer may be responsible for surface change of boiling treated ABS, and the selective influence of boiling treatment on the floatability of boiling treated plastics may be attributed to the difference in the molecular mobility of polymer chains. The effects of flotation time, frother concentration and particle size on flotation behavior of simple plastic were investigated. Based on flotation behavior of simple plastic, flotation separation of boiling treatment ABS and PS with different particle sizes was achieved efficiently. The purity of ABS and PS was up to 99.78% and 95.80%, respectively; the recovery of ABS and PS was up to 95.81% and 99.82%, respectively. Boiling treatment promotes the industrial application of plastics flotation and facilitates plastic recycling. PMID:24602834

Wang, Chong-Qing; Wang, Hui; Wu, Bao-Xin; Liu, Qun

2014-07-01

301

Recent application trends for enhanced boiling surface tubing  

Microsoft Academic Search

Heat exchangers utilizing enhanced nucleate boiling surfaces, such as HIGH FLUX surfaces have been in operation in the Chemical process industries for about 15 years. A number of previous papers have described the experience with these surfaces in olefins plants, petroleum refining, and in reboilers for light hydrocarbon separations - many using heat pumped distillation columns. Enhanced boiling surface heat

P. S. ONeill; E. G. Ragi

1986-01-01

302

Effect of Lubricant on R410A Horizontal Flow Boiling.  

National Technical Information Service (NTIS)

This paper experimentally determines the effect of lubricant on R410A horizontal flow boiling. A baseline was established by measuring the convective boiling heat transfer performance of pure R410A. In addition, the heat transfer performance of an R410A/l...

J. S. Brown M. A. Kedzierski N. N. Sawant

2007-01-01

303

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

304

Heating surface thermal stabilization for pool boiling on porous coverings  

NASA Astrophysics Data System (ADS)

The paper presents the results of comprehensive research of boiling on heating surfaces covered with copper fibrous capillary-porous structures (CPSs) used as fillings in heat pipes. The studies involved experimental and theoretical investigations, including development of technologies related to lab-scale manufacturing of sintered structures. Application-related problems such as the use of boiling in heat transfer control were also taken into account. Experiments were carried out for pool boiling of distilled water, ethanol, R-113 and R-123 on coverings of porosity of 40, 70 and 85%. The scope of the paper includes the description of the experimental setup, the methods used and the study results for pool boiling with various hysteresis types. In addition, possible applications of boiling on CPSs porous coverings to heating surface temperature stabilization are proposed.

Wjcik, T. M.; Poniewski, M. E.

2012-11-01

305

The onset of boiling of the liquid alkali metals  

SciTech Connect

Studies pertinent to the liquid superheat required to initiate boiling and the subsequent behavior of the two-phase fluid have been conducted for many years. Knowledge of the incipient-boiling superheats is important because of the proposed use of liquid metals as reactor coolants, Rankine cycle working fluids, and heat-rejection fluids in space energy-conversion systems. Some of the parameters that have been postulated to influence the incipient boiling superheats and the subsequent two-phase flow behavior of the alkali metals include the system pressure, the pressure-temperature-time history, heat flux, liquid purity, dissolved gas content, surface condition, nuclear radiation, heating method, length of time of operation (for example, aging), liquid velocity, and the approach to boiling. The prediction of incipient-boiling superheats is complex, and the influence of some of these parameters needs additional clarification. 6 refs., 3 figs.

Holtz, R.E.; Lottes, P.A.

1989-01-01

306

Microbiological effectiveness of disinfecting water by boiling in rural Guatemala.  

PubMed

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

2010-03-01

307

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 (110 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.

Rosa, Ghislaine; Miller, Laura; Clasen, Thomas

2010-01-01

308

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

309

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

PubMed

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

Winthrop, K L; Homestead, N

2012-03-01

310

The Physics of Boiling at Burnout  

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

311

Geochemistry of hydrothermal plume in the Suiyo Seamount Caldera  

Microsoft Academic Search

Chemical compounds of the hot basalt origin are discharged into the deep ocean via hydrothermal plume by the deep-sea hydrothermal activity. The hydrothermal plume is widely diffused to the ocean by mixing with ambient seawater. Chemical reactions and interactions with microorganisms in the diffusion process of the hydrothermal plume are important to comprehend the oceanic geochemical cycles. Recently, it has

K. Shitashima; Y. Maeda

2002-01-01

312

The Effect of Subcooling on the Flow and Heat Transfer Characteristics in a Two-Phase Loop Thermosyphon  

NASA Astrophysics Data System (ADS)

A two-phase loop thermosyphon is used as a heat transfer device in an energy-saving heat transportation system and so forth, because it transports thermal energy without any external power supply such as a pump under a body force field. We previously performed a fundamental study on the flow and heat transfer characteristics in a two-phase loop thermosyphon installed with a single heated tube evaporator both experimentally and theoretically which was made under the condition of near saturation temperature of liquid in a reservoir. In the present study, the effects of liquid subcooling and the heat input on the circulation mass flow rates, pressure and temperature distributions, and heat transfer coefficients in the evaporator were examined experimentally using water, ethanol, benzene and Freon 113 as the working fluids. On the other hand, the circulation mass flow rates, pressure and temperature distributions were theoretically calculated and compared with the experimental results.

Imura, Hideaki; Takeshita, Kazuhiro; Doi, Kyoji; Noda, Ken-Ichi

313

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

314

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

NASA Technical Reports Server (NTRS)

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

Simoneau, R. J.

1975-01-01

315

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 (250100 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

316

Transition boiling heat transfer and the film transition regime  

NASA Technical Reports Server (NTRS)

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.

1987-01-01

317

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

318

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

319

Hydrothermal Occurrences in Gusev Crater  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

320

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

2003-07-01

321

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

2002-01-01

322

Vision in hydrothermal vent shrimp.  

PubMed

Bresiliid shrimp from hydrothermal vents on the Mid-Atlantic Ridge have non-imaging eyes adapted for photodetection in light environments of very low intensity. Comparison of retinal structures between both vent shrimp and surface-dwelling shrimp with imaging eyes, and between juvenile and adult vent shrimp, suggests that vent shrimp have evolved from ancestors that lived in a light environment with bright cyclic lighting. Whether the vent shrimp live in swarms and have large dorsal eyes or live in sparse groupings and have large anterior eyes, the basic retinal adaptations are the same across species. Retinal adaptations in adult vent shrimp include the loss of dioptrics, enlargement of both the rhabdomeral segment of the photoreceptors and the light-sensitive rhabdomere therein, attenuation of the arhabdomeral segment of the photoreceptors, reduction of black screening pigment, development of a white diffusing layer behind the photoreceptors, and the loss of rhabdom turnover. PMID:11079388

Chamberlain, S C

2000-09-29

323

Vision in hydrothermal vent shrimp.  

PubMed Central

Bresiliid shrimp from hydrothermal vents on the Mid-Atlantic Ridge have non-imaging eyes adapted for photodetection in light environments of very low intensity. Comparison of retinal structures between both vent shrimp and surface-dwelling shrimp with imaging eyes, and between juvenile and adult vent shrimp, suggests that vent shrimp have evolved from ancestors that lived in a light environment with bright cyclic lighting. Whether the vent shrimp live in swarms and have large dorsal eyes or live in sparse groupings and have large anterior eyes, the basic retinal adaptations are the same across species. Retinal adaptations in adult vent shrimp include the loss of dioptrics, enlargement of both the rhabdomeral segment of the photoreceptors and the light-sensitive rhabdomere therein, attenuation of the arhabdomeral segment of the photoreceptors, reduction of black screening pigment, development of a white diffusing layer behind the photoreceptors, and the loss of rhabdom turnover.

Chamberlain, S C

2000-01-01

324

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

325

``Boiling'' in the water evaporating meniscus induced by Marangoni flow  

NASA Astrophysics Data System (ADS)

A counterintuitive phenomenon, ``boiling,'' was directly observed near the contact line of the pure water meniscus formed in a ball and disk configuration, when the ball temperature was far lower than the saturation temperature of water. The number of the emerging bubbles due to ``boiling'' increased with ball temperature rising; each bubble would expanse initially and then collapse. When two surfaces were heated to the same temperature, ``boiling'' disappeared. It was proposed that the temperature gradient between the two surfaces initiated Marangoni flow, which hindered flow toward the film, resulting in the negative pressure and cavitation in the liquid film.

Liu, Xiang; Guo, Dan; Xie, Guoxin; Liu, Shuhai; Luo, Jianbin

2012-11-01

326

Development of potential ecological niches in impact-induced hydrothermal systems: The small-to-medium size impacts  

NASA Astrophysics Data System (ADS)

Effect of meteorite impact on the biological evolution is usually considered by its catastrophic consequences. However, the impacts can create opportunity for other organisms and the structures themselves can serve as suitable ecological niches (oases) for life. In this contribution we present results of modeling of an impact-induced hydrothermal (IHT) system in a small-to-medium sized impact crater, where the development of zones habitable for primitive hydrothermal thermophilic and hypethermophilic microorganisms was studied. The impact and geothermal modeling was verified against the 4-km diameter Krdla complex structure, Hiiumaa Island, Estonia. If there is an sufficient amount of water present in the target (e.g., sea cover, groundwater or permafrost resources) then the differential temperature fields created by the impact initiate a hydrothermal circulation system within the crater. The results of transient fluid flow and heat transfer simulations in Krdla suggest that immediately after impact the temperatures in the central area, which contains the most hydrothermal alteration, were well above the boiling point. However, due to efficient heat loss at the groundwater vaporization front, the vapor-dominated area disappears within a few decades. In the central uplift area, the conditions favorable for thermophilic microorganisms (temperatures <100 C) were reached in 500-1000 years after the impact. The overall cooling to ambient temperatures in the deeper parts of the central uplift lasted for thousands of years. In the crater depression and rim area the initial temperatures, suggested by the impact modeling, were much lower - from 150 C to ambient temperatures, except locally in fracture zones and suevite pockets. Our data suggest that in small-to-medium size impact craters with insignificant melting, the suitable conditions for hydrothermal microbial communities are established shortly (tens to few hundreds of years as maximum) after the impact in most parts of the crater. In the central uplift area the microbial colonization is inhibited for about a thousand years. However, this is the area, which afterwards retains the optimum temperatures (45-120 C) needed for hydrothermal microorganisms for the longest period. Geochemical and mineralogical data suggest, in general, neutral pH 7(1) fluid of the IHT system, which is, when compared to volcanic hydrotherms, richer in dissolved oxygen and poor in reduced compounds. This suggests the preference for sulfur-reducing microorganisms in the possible impact-induced hydrothermal communities.

Versh, Evelin; Kirsime, Kalle; Jeleht, Argo

2006-12-01

327

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

328

Hydrothermal industrialization: direct heat development. Final report  

SciTech Connect

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

Not Available

1982-05-01

329

Hydrothermal vents: a novel theory of illumination  

Microsoft Academic Search

There are many theories revolving around the source of non-thermally based visible light emissions from deep-sea hydrothermal vents. Although many of these theories have been proven possible in a controlled laboratory environment, none have been directly linked to hydrothermal vents through on-site experimentation and evaluation. Nor have any of them conclusively lain to rest the unanswerable and unpredictable source and

D. J. Bogorff

2005-01-01

330

Hydrothermal processings to produce magnetic particulates  

Microsoft Academic Search

?-Fe2O3, ?-Fe2O3 , and ?-FeOOH powders were used as starting materials to prepare barium hexaferrite hydrothermally. Since strontium hexaferrite and lanthanum-doped calcium hexaferrite have coercivities similar to that of barium ferrite, the hydrothermal synthesis of strontium hexaferrite and lanthanum-doped calcium hexaferrite were also explored. The reaction products obtained with the various starting materials are described. Electron micrographs showed that ?-Fe2O3,

C. H. Lin; Z. W. Shih; T. S. Chin; M. L. Wang; Y. C. Yu

1990-01-01

331

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

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

2009-04-01

332

Esterification of fatty acid catalyzed by hydrothermally stable propylsulfonic acid-functionalized mesoporous silica SBA-15.  

PubMed

Propylsulfonic acid-functionalized mesoporous silica SBA-15 has been synthesized via one-step strategy at 130C based on the co-condensation of TEOS and MPTMS in the presence of Pluronic 123 polymer and H?O? in HCl aqueous solution. The synthesized solid exhibited hydrothermal stability in boiling water without significant change in textural properties. The catalytic performance of the synthesized solid was studied in the esterification of oleic acid with methanol. The experimental results revealed that the large mesopore structures of SBA-15-PrSO?H solid synthesized at 130C could favor a facile access of oleic acid to the acid sites, making the comparable activity to that of phenyl ethyl sulfonic acid functionalized silica and higher than that of dry amberlyst-15. PMID:23728335

Mar, Win Win; Somsook, Ekasith

2013-01-01

333

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

334

Hydrothermal mineralization along submarine rift zones, Hawaii  

USGS Publications Warehouse

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

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

1996-01-01

335

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

NASA Astrophysics Data System (ADS)

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

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

2003-12-01

336

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

337

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

338

Oxidation of molten fuel simulant drops under film boiling conditions.  

National Technical Information Service (NTIS)

The degree of oxidation of drops of aluminum metal was investigated parametrically for a range of melt diameters, relative melt-water velocities, melt temperatures, water temperatures, and ambient pressures using a combined film boiling-metal oxidation mo...

M. F. Young L. S. Nelson

1991-01-01

339

Boiling Heat Transfer in Falling Film Evaporators with Corrugated Surfaces.  

National Technical Information Service (NTIS)

Boiling heat transfer coefficients were determined for falling film evaporation on corrugated surfaces. The local coefficients varied much more from peak to valley with deionized water than with saline water, probably becuase of poorer wetting by deionize...

G. Jansen P. C. Owzarski

1971-01-01

340

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

341

Boiling local heat transfer enhancement in minichannels using nanofluids  

PubMed Central

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.

2013-01-01

342

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

343

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

344

A microgravity boiling and convective condensation experiment  

NASA Astrophysics Data System (ADS)

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

1987-12-01

345

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

NASA Astrophysics Data System (ADS)

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 C) and major element compositions, low dissolved CO 2 concentrations (4.4 mmol/kg) and high measured pH (4.2-4.9 at 25 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 C) fluid. All PACMANUS fluids are characterized by negative ?DO values, in contrast to positive values at Vienna Woods, suggesting substantial magmatic water input to circulating fluids at Pual Ridge. Low measured pH (25 C) values (2.6-2.7), high endmember CO 2 (up to 274 mmol/kg) and negative ?34SS values (down to -2.7) in some vent fluids are also consistent with degassing of acid-volatile species from evolved magma. Dissolved CO 2 at PACMANUS is more enriched in 13C (-4.1 to -2.3) than Vienna Woods (-5.2 to -5.7), 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 SO 4 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 (?80 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

2011-02-01

346

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

347

Reliquefaction of boil-off from liquefied natural gas  

Microsoft Academic Search

This patent describes a process for liquifying boil-off gas resulting from the evaporation of liquified natural gas contained in a storage vessel, the boil-off gas being cooled and liquified in a closed-loop nitrogen refrigeration system and then returned to the storage vessel. The closed loop refrigeration system comprises the following steps: compressing nitrogen as a working fluid in a multi-stage

W. G. Stuber; K. W. Kovak

1989-01-01

348

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

349

Taylor stability of viscous fluids with application to film boiling  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

350

Characteristics of slush and boiling methane and methane mixtures  

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

351

Validation of IVA Computer Code for Flow Boiling Stability Analysis  

Microsoft Academic Search

IVA is a computer code for modeling of transient multiphase, multi-component, non-equilibrium flows in arbitrary geometry including flow boiling in 3D nuclear reactors. This work presents part of the verification procedure of the code. We analyze the stability of flow boiling in natural circulation loop. Experimental results collected on the AREVA\\/FANP KATHY loop regarding frequencies, mass flows and decay ratio

Ivanov Kolev; Nikolay

2006-01-01

352

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

353

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

354

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.

2011-01-01

355

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 (100-400C), 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

356

Structure of two hydrothermal megaplumes  

SciTech Connect

The dynamic signatures of two megaplumes above the Juan de Fuca Ridge are analyzed. The chemical properties of these two lenslike masses of water were described by Baker at al. (1989) and clearly indicate that they were generated by massive and rapid ventings of hot hydrothermal fluid from the ridge. Both are nearly circular with radii of about 6.5 km. The isopycnals bow upward around these cores of anomalous water, leading to an anticyclonic circulation. A cyclogeostrophic balance gives maximum currents at the edge of the core of 0.11 m/s for the first megaplume (MP1) and 0.07 m/s for the second megaplume (MP2). Currents extend beyond the core to a radius of 12-15 km. The centers of the cores are in nearly solid body rotation with relative vorticities of -0.5f (MP2) and potential vorticity anomalies, expressed in units of equivalent relative vorticity, of -0.8f (MP1) and -0.6f (MP2), where f is the Coriolis frequency. The aspect ratio of each megaplume gives a Burger number of 0.22. In terms of these nondimensional numbers, the megaplumes are very similar to eddies of Mediterranean water found in the eastern Atlantic (meddies), despite their very different origin.

D`asaro, E.; Walker, S.; Baker, E. [Washington Univ., Seattle, WA (United States)]|[NOAA, Seattle, WA (United States)

1994-10-01

357

Seismicity and fluid geochemistry at Lassen Volcanic National Park, California: Evidence for two circulation cells in the hydrothermal system  

NASA Astrophysics Data System (ADS)

Seismic analysis and geochemical interpretations provide evidence that two separate hydrothermal cells circulate within the greater Lassen hydrothermal system. One cell originates south to SW of Lassen Peak and within the Brokeoff Volcano depression where it forms a reservoir of hot fluid (235-270 C) that boils to feed steam to the high-temperature fumarolic areas, and has a plume of degassed reservoir liquid that flows southward to emerge at Growler and Morgan Hot Springs. The second cell originates SSE to SE of Lassen Peak and flows southeastward along inferred faults of the Walker Lane belt (WLB) where it forms a reservoir of hot fluid (220-240 C) that boils beneath Devils Kitchen and Boiling Springs Lake, and has an outflow plume of degassed liquid that boils again beneath Terminal Geyser. Three distinct seismogenic zones (identified as the West, Middle, and East seismic clusters) occur at shallow depths (< 6 km) in Lassen Volcanic National Park, SW to SSE of Lassen Peak and adjacent to areas of high-temperature (? 161 C) fumarolic activity (Sulphur Works, Pilot Pinnacle, Little Hot Springs Valley, and Bumpass Hell) and an area of cold, weak gas emissions (Cold Boiling Lake). The three zones are located within the inferred Rockland caldera in response to interactions between deeply circulating meteoric water and hot brittle rock that overlies residual magma associated with the Lassen Volcanic Center. Earthquake focal mechanisms and stress inversions indicate primarily N-S oriented normal faulting and E-W extension, with some oblique faulting and right lateral shear in the East cluster. The different focal mechanisms as well as spatial and temporal earthquake patterns for the East cluster indicate a greater influence by regional tectonics and inferred faults within the WLB. A fourth, deeper (5-10 km) seismogenic zone (the Devils Kitchen seismic cluster) occurs SE of the East cluster and trends NNW from Sifford Mountain toward the Devils Kitchen thermal area where fumarolic temperatures are ? 123 C. Lassen fumaroles discharge geothermal gases that indicate mixing between a N 2-rich, arc-type component and gases derived from air-saturated meteoric recharge water. Most gases have relatively weak isotopic indicators of upper mantle or volcanic components, except for gas from Sulphur Works where ?13C-CO 2, ?34S-H 2S, and ?15N-N 2 values indicate a contribution from the mantle and a subducted sediment source in an arc volcanic setting.

Janik, Cathy J.; McLaren, Marcia K.

2010-01-01

358

VLA Shows "Boiling" in Atmosphere of Betelgeuse  

NASA Astrophysics Data System (ADS)

A team of astronomers says that observations with the National Science Foundation's Very Large Array (VLA) radio telescope show that a neighboring bloated star has giant convective plumes propelling gas from its surface (photosphere) up into the star's atmosphere. This new information contradicts long-held ideas that such stellar atmospheres are more uniform, and may resolve questions about how the star's atmosphere attains its enormous size as well as how dust and gas is driven away from the star. Jeremy Lim of the Academia Sinica Institute of Astronomy & Astrophysics in Taiwan; Chris Carilli, Anthony Beasley, and Ralph Marson of the National Radio Astronomy Observatory (NRAO) in Socorro, NM; and Stephen White of the University of Maryland studied the red-supergiant star Betelgeuse, about 430 light-years away in the constellation Orion. They reported their findings in the April 9 issue of the scientific journal Nature. "These radio-telescope images confirm that Betelgeuse -- already more than 600 times larger than our Sun -- has a dense atmosphere that extends to many times larger still than the star itself," said Lim. "The highest-resolution image shows the star's atmosphere to have a remarkably complex structure." "To our surprise," added White, "the images also show that most of the gas in the atmosphere is only about as hot as that on the surface. Previously, all of it was thought to be very much hotter." The astronomers used the VLA to make images of Betelgeuse at a variety of radio frequencies. The series of radio observations measured the temperature of the star's atmosphere at different heights. Previous observations with the Hubble Space Telescope (HST) at ultraviolet wavelengths showed that the star's atmosphere contains very hot gas at about twice the surface temperature. The VLA images showed that there also is lower-temperature gas throughout the atmosphere. This gas is near the surface temperature at low heights and decreases in temperature progressively outwards. Although its existence was not previously suspected, this lower-temperature gas turns out to be the most abundant constituent of Betelgeuse's atmosphere. "This alters our basic understanding of red-supergiant star atmospheres," explains Lim. "Instead of the star's atmosphere expanding uniformly because of gas heated to very high temperatures near its surface, it now appears that several giant convection cells propel gas from the star's surface into its atmosphere. This creates the complex structure we observe for Betelgeuse's atmosphere." Betelgeuse can be likened to an enormous "boiling" ball of gas heated by the release of energy from nuclear fusion in its core. The circulating boiling pattern -- convection -- appears as large regions of hot upwelling gas on the star's surface. "The idea that red-supergiant stars have enormous convection cells is not new," noted Marson. "This was suggested by Martin Schwarzschild more than 20 years ago, and was seen in optical images of Betelgeuse's surface in 1990." The new picture of Betelgeuse's atmosphere also helps resolve the mystery of how massive amounts of dust and gas are expelled from red supergiant stars, an important source of enrichment for the interstellar medium. If their atmospheres were entirely very hot at lower levels, dust grains would not be able to condense there. Dust grains could possibly condense at higher levels, but there they would not get enough "push" from the star's radiation to explain their outward movement. In the new picture, the relatively cool environment at lower levels allows dust grains to condense effectively; here they can be strongly propelled by the more-intense starlight, carrying gas with them. Indeed, dust has previously been inferred to form sporadically near Betelgeuse's surface, but its presence there was difficult to reconcile with the old picture. "This method for propelling the mass outflows of red giant and supergiant stars was proposed by Sun Kwok i

1998-04-01

359

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

USGS Publications Warehouse

NorrisMammoth corridor is a complex subsidence structure that extends ?40 km northward from the 0.6 Ma Yellowstone caldera, and contains many hydrothermal features with high fluid discharges totaling ?1000 l/s. About 150250 l/s of hydrothermal water, which attains boiling temperature at surface and 360C at depth, discharge from the Norris Geyser Basin, adjacent to the caldera. The highest thermal water and gas discharges in the corridor are from Mammoth Hot Springs, where 500600 l/s thermal water with surface temperatures of up to 73C and calculated subsurface temperatures of ?100C issue from ?100 hot springs scattered over a score of step-like travertine terraces that range in age from ?0.4 Ma to recent. All the thermal water is meteoric, likely recharged in the Gallatin Range at 2.53.0 km elevations. The isotopic and chemical compositions of thermal waters and solutes can be interpreted to indicate a common magmatic source for heat and volatile solutes located near Norris. However, the chemical and isotopic compositions of gases, especially the 3He/4He ratios, provide strong evidence for a separate magmatic source for the Mammoth system.

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

2000-01-01

360

Synthesis of hydrothermally stable, hierarchically mesoporous aluminosilicate Al-SBA-1 and their catalytic properties.  

PubMed

Hydrothermally stable mesoporous aluminosilicates Al-SBA-1 with hierarchical pore structure have been successfully synthesized under alkaline condition at 120 C by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecyl pyridinium chloride (CPC)) as template. The Si/Al ratio could be as high as 5 and the incorporation of Al into the silica framework did not disturb the well-ordered cubic Pm ?3n mesostructure. Meanwhile, the incorporation of Al could greatly increase the specific surface area and pore volume of the samples. The Al-SBA-1 materials exhibited a high hydrothermal stability and remained stable even after being treated in boiling water for 10 days. The catalytic activity of the Al-SBA-1 materials was investigated by employing the Friedel-Crafts alkylation of toluene with benzyl alcohol as a model reaction and they exhibited excellent catalytic property due to the incorporated acid sites and the hierarchically mesoporous structure. PMID:22327221

Li, Na; Wang, Jin-Gui; Xu, Jian-Xiong; Liu, Jin-Yu; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

2012-03-21

361

Synthesis of hydrothermally stable, hierarchically mesoporous aluminosilicate Al-SBA-1 and their catalytic properties  

NASA Astrophysics Data System (ADS)

Hydrothermally stable mesoporous aluminosilicates Al-SBA-1 with hierarchical pore structure have been successfully synthesized under alkaline condition at 120 C by employing organic mesomorphous complexes of polyelectrolyte (poly(acrylic acid) (PAA)) and cationic surfactant (hexadecyl pyridinium chloride (CPC)) as template. The Si/Al ratio could be as high as 5 and the incorporation of Al into the silica framework did not disturb the well-ordered cubic Pm3&cmb.macr;n mesostructure. Meanwhile, the incorporation of Al could greatly increase the specific surface area and pore volume of the samples. The Al-SBA-1 materials exhibited a high hydrothermal stability and remained stable even after being treated in boiling water for 10 days. The catalytic activity of the Al-SBA-1 materials was investigated by employing the Friedel-Crafts alkylation of toluene with benzyl alcohol as a model reaction and they exhibited excellent catalytic property due to the incorporated acid sites and the hierarchically mesoporous structure.

Li, Na; Wang, Jin-Gui; Xu, Jian-Xiong; Liu, Jin-Yu; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

2012-03-01

362

Peptide synthesis in early earth hydrothermal systems  

USGS Publications Warehouse

We report here results from experiments and thermodynamic calculations that demonstrate a rapid, temperature-enhanced synthesis of oligopeptides from the condensation of aqueous glycine. Experiments were conducted in custom-made hydrothermal reactors, and organic compounds were characterized with ultraviolet-visible procedures. A comparison of peptide yields at 260??C with those obtained at more moderate temperatures (160??C) gives evidence of a significant (13 kJ ?? mol-1) exergonic shift. In contrast to previous hydrothermal studies, we demonstrate that peptide synthesis is favored in hydrothermal fluids and that rates of peptide hydrolysis are controlled by the stability of the parent amino acid, with a critical dependence on reactor surface composition. From our study, we predict that rapid recycling of product peptides from cool into near-supercritical fluids in mid-ocean ridge hydrothermal systems will enhance peptide chain elongation. It is anticipated that the abundant hydrothermal systems on early Earth could have provided a substantial source of biomolecules required for the origin of life. Astrobiology 9, 141-146. ?? 2009 Mary Ann Liebert, Inc. 2009.

Lemke, K. H.; Rosenbauer, R. J.; Bird, D. K.

2009-01-01

363

Organic sulfur metabolisms in hydrothermal environments.  

PubMed

Sulfur is central to the metabolisms of many organisms that inhabit extreme environments. While biotic and abiotic cycling of organic sulfur compounds has been well documented in low-temperature anaerobic environments, cycling of organic sulfur in hydrothermal environments has received less attention. Recently published thermodynamic data have been used to estimate aqueous alkyl thiol and sulfide activities in deep-sea hydrothermal systems. Here we use geochemical mixing models to predict fluid compositions that result from mixing end-member hydrothermal fluid from the East Pacific Rise with bottom seawater. These fluid compositions are combined with estimates of methanethiol and dimethylsulfide activities to evaluate energy yields for potential organic sulfur-based metabolisms under hydrothermal conditions. Aerobic respiration has the highest energy yields (over -240 kJ/mol e?) at lower temperature; however, oxygen is unlikely to persist at high temperatures, restricting aerobic respiration to mesophilic communities. Nitrite reduction to N? has the highest energy yields at higher temperatures (greater than ?40 C). Nitrate and nitrite reduction to ammonium also yield significant energy (up to -70 kJ/mol e?). Much lower, but still feasible energy yields are calculated for sulfate reduction, disproportionation, and reduction with H?. Organic compound family and the activity of methanethiol and dimethylsulfide were less important than metabolic strategy in determining overall energy yields. All metabolic strategies considered were exergonic within some portion of the mixing regime suggesting that organic sulfur-based metabolisms may be prevalent within deep-sea hydrothermal vent microbial communities. PMID:22469147

Rogers, Karyn L; Schulte, Mitchell D

2012-07-01

364

A new hydrothermal scenario for the 2006 Lusi eruption, Indonesia. Insights from gas geochemistry  

NASA Astrophysics Data System (ADS)

The 29th of May 2006 gas and mud eruptions suddenly appeared along the Watukosek fault in the north east of Java, Indonesia. Within a few weeks several villages were submerged by boiling mud. The most prominent eruption site was named Lusi. To date (November 2011) Lusi is still active and a ~ 7 km2 area is covered by the burst mud breccia. The mechanisms responsible for this devastating eruption remain elusive. While there is consensus about the origin of the erupted mud, the source of water is uncertain, the origin of the gas is unknown and the trigger of the eruption is still debated. In order to shed light on these unknowns, we acquired a wide set of data of molecular and isotopic composition of gas sampled in several Lusi vents, in the surrounding mud volcanoes, in the closest natural gas field (Wunut), and in the hydrothermal vents at the neighbouring volcanic complex in the period 2006-2011. The boiling fluids erupted in the crater zone are apparently CO2-dominated, while colder CH4-dominated and C2-C3 bearing fluids are identified at several sites around the crater zone. Gas genetic diagrams, maturity plots and gas generation modelling suggest that the hydrocarbons are thermogenic (?13C1 up to - 35; ?13C2 up to - 20), deriving from marine kerogen with maturity of at least 1.5%Ro, for instance in the ~ 4400 m deep Ngimbang source rocks. CO2 released from the crater and surrounding seeps is also thermogenic (?13C from - 15 to - 24) related to kerogen decarboxylation or thermal CH4 oxidation in deep rocks, although three vents just outside the crater showed an apparent inorganic signature (- 7.5 < ?13C = - 0.5) associated to mantle helium (R/Ra up to 6.5). High CO2-CH4 equilibrium temperatures (200-400 C) are typical of thermally altered hydrocarbons or organic matter. The data suggest mainly thermally altered organic sources for the erupted gases, deeper sourced than the mud and water (Upper Kalibeng shales). These results are consistent with a scenario of deep seated (> 4000 m) magmatic intrusions and hydrothermal fluids responsible for the enhanced heat that altered source rocks and/or gas reservoirs. The neighbouring magmatic Arjuno complex and its fluid-pressure system combined with high seismic activity could have played a key role in the Lusi genesis and evolution. Within this new model framework, Lusi is better understood as a sediment-hosted hydrothermal system rather than a mud volcano.

Mazzini, Adriano; Etiope, Giuseppe; Svensen, Henrik

2012-02-01

365

Hydrothermal processing of radioactive combustible waste  

SciTech Connect

Hydrothermal processing has been demonstrated for the treatment of radioactive combustible materials for the US Department of Energy. A hydrothermal processing system was designed, built and tested for operation in a plutonium glovebox. Presented here are results from the study of the hydrothermal oxidation of plutonium and americium contaminated organic wastes. Experiments show the destruction of the organic component to CO{sub 2} and H{sub 2}O, with 30 wt.% H{sub 2}O{sub 2} as an oxidant, at 540 C and 46.2 MPa. The majority of the actinide component forms insoluble products that are easily separated by filtration. A titanium liner in the reactor and heat exchanger provide corrosion resistance for the oxidation of chlorinated organics. The treatment of solid material is accomplished by particle size reduction and the addition of a viscosity enhancing agent to generate a homogeneous pumpable mixture.

Worl, L.A.; Buelow, S.J.; Harradine, D.; Le, L.; Padilla, D.D.; Roberts, J.H.

1998-09-01

366

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 represents an outstanding example of hydrothermal Nickel sulphide mineralization type. Avebury Ni deposit is a system of hydrothermal Ni ore bodies. It is 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 the mafic/ultramafic rocks in the area, and subsequent re-deposition in favourable structural traps. The mineralization is spatially 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 presents early Cambrian ultramafic-mafic complexes in the West. The Ferrar large igneous province (LIP) extends over to Antarctica and is related to the Karoo Province in southern Africa that comprises tholeiitic lava flows, sills, and dyke swarms. The Ferrar and Karoo provinces were associated with the same thermal anomaly that was involved in the break up of Gondwana. The presence of mafic/ultramafic rocks in favourable lithological packages and/or structural traps along the margins of the province, as well as several prospective reduced or reactive sedimentary packages within and around the Ferrar indicate that this LIP could represent a novel promising ground for Ni hydrothermal exploration. Based on this prospective geological background, a prospectivity analysis for hydrothermal Ni deposits was carried out on regional scale for the entire state of Tasmania. A conceptual model of hydrothermal nickel mineral system was used to identify the following as the most important exploration criteria for hydrothermal nickel deposits: (i) 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 komatiites/picrites/mafic-ultramafic rocks formed from magma with >7% MgO, large igneous province; major faults; crustal contamination, older sulphur bearing rock suites, 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-Alvalez, I.; Porwal, A.; McCuaig, T. C.

2009-04-01

367

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

368

Intra-field variability in microbial community associated with phase-separation-controlled hydrothermal fluid chemistry in the Mariner field, the southern Lau Basin  

NASA Astrophysics Data System (ADS)

A newly discovered hydrothermal field called the Mariner field at the northernmost central Valu Fa Ridge (VFR) in the Lau Basin was explored and characterized by geochemical and microbiological surveys. The hydrothermal fluid (max. 365 u^C) emitting from the most vigorous vent site (Snow chimney) was boiling just beneath the seafloor at a water depth of 1908 m and two end-members of hydrothermal fluid were identified. Mineral and fluid chemistry of typical brine-rich (Snow chimney and Monk chimney) and vapor-rich (Crab Restaurant chimney) hydrothermal fluids and the host chimney structures were analyzed. Microbial community structures in three chimney structures were also investigated by culture-dependent and - independent analyses. The 16S rRNA gene clone analysis revealed that both bacterial and archaeal rRNA gene communities at the chimney surface zones were different among three chimneys. The bacterial and archaeal rRNA gene communities of the Snow chimney surface were very similar with those in the dead chimneys, suggesting concurrence of metal sulfide deposition at the inside and weathering at the surface potentially due to its large structure and size. Cultivation analysis demonstrated the significant variation in culturability of various microbial components, particularly of thermophilic H2- and/or S-oxidizing chemolithoautotrophs such as the genera Aquifex and Persephonella, among the chimney sites. The culturability of these chemolithoautotrophs might be associated with the input of gaseous energy and carbon sources like H2S, H2 and CH4 from the hydrothermal fluids, and might be affected by phase-separation- controlled fluid chemistry. In addition, inter-fields comparison of microbial community structures determined by cultivation analysis revealed novel characteristics of the microbial communities in the Mariner field of the Lau Basin among the global deep-sea hydrothermal systems.

Takai, K.; Ishibashi, J.; Lupton, J.; Ueno, Y.; Nunoura, T.; Hirayama, H.; Horikoshi, K.; Suzuki, R.; Hamasaki, H.; Suzuki, Y.

2006-12-01

369

Raman Spectroscopy at Deep-Sea Hydrothermal Vents  

Microsoft Academic Search

In this presentation we will describe the development and optimization of a custom submersible Raman instrument that was successfully deployed in one of the harshest environments on the planet, hydrothermal vent systems. The primary objective of this project was to develop a multi-platform, broad spectral chemical sensor for investigating hydrothermal processes in the deep ocean. Mid-ocean ridge hydrothermal systems are

W. J. Thompson; B. J. Marquardt; M. D. Lilley

2008-01-01

370

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

PubMed

This study investigates the hydrodynamic characteristics of droplet impingement on heated surfaces and compares the effect of surface temperature when using water and a nanofluid on a polished and nanostructured surface. Results are obtained for an impact Reynolds number and Weber number of approximately 1700 and 25, respectively. Three discs are used: polished silicon, nanostructured porous silicon and gold-coated polished silicon. Seven surface temperatures, including single-phase (non-boiling) and two-phase (boiling) conditions, are included. Droplet impact velocity, transient spreading diameter and dynamic contact angle are measured. Results of water and a water-based single-wall carbon-nanotube nanofluid impinging on a polished silicon surface are compared to determine the effects of nanoparticles on impinging dynamics. The nanofluid results in larger spreading velocities, larger spreading diameters and an increase in early-stage dynamic contact angle. Results of water impinging on both polished silicon and nanostructured silicon show that the nanostructured surface enhances the heat transfer for evaporative cooling at lower surface temperatures, which is indicated by a shorter evaporation time. Using a nanofluid or a nanostructured surface can reduce the total evaporation time up to 20% and 37%, respectively. Experimental data are compared with models that predict dynamic contact angle and non-dimensional maximum spreading diameter. Results show that the molecular-kinetic theory's dynamic contact angle model agrees well with current experimental data for later times, but over-predicts at early times. Predictions of maximum spreading diameter based on surface energy analyses indicate that these models over-predict unless empirical coefficients are adjusted to fit the test conditions. This is a consequence of underestimates of the dissipative energy for the conditions studied. PMID:21715897

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

2009-11-18

371

Sonar images hydrothermal vents in seafloor observatory  

NASA Astrophysics Data System (ADS)

Hydrothermal plumes venting from black smokers and diffuse flow discharging from the surrounding area of the seafloor are important as agents of transfer of heat, chemicals, and biological material from the crust into the ocean in quantitatively significant amounts [Elderfield and Schultz, 1996]. An unprecedented time series of three-dimensional (3-D) volume images of plumes rising tens of meters from black smoker vents and of concurrent 2-D maps of diffuse flow discharging from surrounding areas of the seafloor illuminates the turbulent behavior of hydrothermal fluid transfer into the ocean (see Figure 1).

Rona, Peter; Light, Russ

2011-05-01

372

Hydrothermal Solidification of the Yellow River Sediments  

NASA Astrophysics Data System (ADS)

The properties of chemical and mineral compositions for the silts at upper (Yinchuan), middle (Tongguan) and lower (Zhengzhou) reaches were very similar, and moreover the heavy metals dissolved from those silts were low, below the regulatory levels for the environmental quality standards of China. The silts therefore could be used as raw materials readily and safely. A hydrothermal processing has been used to solidify the silt which is from middle reach and the results showed that during the hydrothermal process CSH gel and fine particle formation made matrix denser and thus gave an initial strength development, and tobermorite, transformed from the CSH gel, further promoted the strength development.

Jing, Z.; Zhou, L.; Ran, X.; Ishida, E. H.

2010-11-01

373

Hydrothermal synthesis of ytterbium silicate nanoparticles.  

PubMed

A simple, low-cost hydrothermal method was developed to synthesize 20-nm-diameter single-crystalline ytterbium silicate (Yb(2)Si(2)O(7) and Yb(2)SiO(5)) nanoparticles at 200 degrees C. This is nearly 1000 degrees C lower than that for the typical sol-gel route to ytterbium silicate powders. Obtained powders showed very low thermal conductivity, a suitable thermal expansion coefficient, and excellent thermal/structural stability, suggesting a potential application to environmental and thermal barrier coatings. Special focus was placed on assessing the hydrothermal reaction mechanism for particle formation. PMID:20085266

Chen, Hongfei; Gao, Yanfeng; Liu, Yun; Luo, Hongjie

2010-02-15

374

Numerical simulation of pool boiling of a Lennard-Jones liquid  

NASA Astrophysics Data System (ADS)

We performed a numerical simulation of pool boiling by a molecular dynamics model. In the simulation, a liquid composed of Lennard-Jones particles in a uniform gravitational field is heated by a heat source at the bottom of the system. The model successfully reproduces the change in regimes of boiling from nucleate boiling to film boiling with the increase of the heat source temperature. We present the pool boiling curve by the model, whose general behavior is consistent with those observed in experiments of pool boiling.

Inaoka, Hajime; Ito, Nobuyasu

2013-09-01

375

Boiling heat transfer enhancement in subsurface horizontal and vertical tunnels  

SciTech Connect

Complex experimental investigations of boiling heat transfer on structured surfaces covered with perforated foil were taken up. Experimental data were discussed for two kinds of enhanced surfaces formed by joined horizontal and vertical tunnels: tunnel structures (TS) and narrow tunnel structures (NTS). The experiments were carried out with water, ethanol and R-123 at atmospheric pressure. The TS and NTS surfaces were manufactured out of perforated copper foil of 0.05 mm thickness (hole diameters: 0.3, 0.4, 0.5 mm) sintered with the mini-fins, formed on the vertical side of the 5 mm high rectangular fins and horizontal inter-fin surface. The effects of hole (pore) diameters, tunnel pitch for TS and tunnel width for NTS on nucleate pool boiling were examined. Substantial enhancement of heat transfer coefficient was observed. The investigated surfaces showed boiling heat transfer coefficients similar to those of existing structures with subsurface tunnels, but at higher heat fluxes range. (author)

Pastuszko, Robert [Chair of Thermodynamics and Fluids Mechanics, The Kielce University of Technology, Al. Tysiaclecia P.P. 7, 25-314 Kielce (Poland)

2008-09-15

376

Atomic dynamics of explosive boiling of liquid-argon films  

NASA Astrophysics Data System (ADS)

Using molecular-dynamics simulation, we study the explosive boiling of thin liquid-argon films adsorbed on a metal surface. This process might be induced by heating the metal substrate by an ultra-fast laser. Upon sudden heating of the metal to temperatures well beyond the critical temperature of Ar, the film starts boiling. While thin films, with thickness below seven monolayers, fragment completely, in larger films only the near-surface Ar layers vaporize. The resulting vapor pressure drives the expansion of the remaining liquid overlayers. By monitoring the space and time dependence of the hydrodynamic variables density, pressure, and temperature, as well as the local thermodynamic state in the Ar sample, we obtain a detailed microscopic picture of the explosive boiling process. Finally, as a result of the fragmentation process, the abundance distribution of the clusters formed in the expansion follows a power-law distribution for cluster sizes m ? 10.

Gu, X.; Urbassek, H. M.

2005-09-01

377

Advances in Enhanced Boiling Heat Transfer From Electronic Components  

NASA Astrophysics Data System (ADS)

This paper reviews recent advances in enhancing boiling heat transfer from electronic components immersed in dielectric liquids by use of surface microstructures. The microstructures developed include rough surfaces produced by sanding, vapor blasting hard particles, sputtering of SiO2 followed by wet etching of the surface, chemical vapor deposition of SiO2 film etc., laser-drilled cavities, a brush-like structure (dendritic structure), reentrant and micro-reentrant cavities, microfins, and porous structures fabricated by alumina particle spraying and painting of silver flakes, diamond particles, aluminum particles and copper particles. Heat sink studs with drilled holes, microfins, multi-layered micro-channels and pores, and pin fins with and without microporous coating have also been developed. The height of microstructure ranges from 0 to 12mm. The primary issues discussed are the mitigation of temperature overshoot at boiling incipience, enhancement of nucleate boiling heat transfer and increasing the critical heat flux.

Honda, Hiroshi; Wei, Jinjia

378

Pool boiling on a large horizontal flat resistance heater  

SciTech Connect

Results are presented of experiments on n-pentane/Freon-113 system, carried out to investigate the film-transition boiling region where liquid-solid contacts contribute significantly to the local heat flux, using a large flat horizontal resistance heater mounted on a ceramic insulating substrate. After steady film boiling was reached, the heat flux was decreased and recorded simultaneously with the temperature measured by thermocouples attached to the lower side of the heater surface. It is shown that the observed data on the quasi-linear film boiling regime are better represented by Berenson's (1960) correlation than by Klimenko's (1981) correlation. Burnout values measured for Freon-113 compared reasonably well to available correlations for the flat plate geometry. 10 refs.

Reguillot, F.; Witte, L.; Lienhard, J.; Poniewski, M. (Houston, University, TX (United States) Kielce University of Technology, (Poland))

1992-08-01

379

a New Analytical Model for Heat Transfer in Pool Boiling  

NASA Astrophysics Data System (ADS)

In this paper, dependence of active nucleation site density on boiling surfaces are developed. For pool boiling heat transfer, a mathematical model is derived based on statistical treatment using the probability density function of the cavity mouth radius and existing correlation for active nucleation site density, the volume of single bubble at departure, the bubble departure diameter and the bubble departure frequency. The proposed model is expressed as a function of wall superheat, the contact angle, maximum and minimum active cavities, and physical properties of fluid. It is shown that the wall heat flux can be determined by the consideration of the variation of the cavity mouth radius. A good agreement between the proposed model predictions and experimental data is found for different contact angles. It also turns out that the present model explains well the mechanism on how wettability affects the pool boiling.

Xiao, Boqi

380

Boiling heat transfer on fins - experimental and numerical procedure  

NASA Astrophysics Data System (ADS)

The paper presents the research methodology, the test facility and the results of investigations into non-isothermal surfaces in water boiling at atmospheric pressure, together with a discussion of errors. The investigations were conducted for two aluminium samples with technically smooth surfaces and thickness of 4 mm and 10 mm, respectively. For the sample of lower thickness, on the basis of the surface temperature distribution measured with an infrared camera, the local heat flux and the heat transfer coefficient were determined and shown in the form of a boiling curve. For the thicker sample, for which 1-D model cannot be used, numerical calculations were conducted. They resulted in obtaining the values of the local heat flux on the surface the invisible to the infrared, camera i.e. on the side on which the boiling of the medium proceeds.

Orzechowski, T.; Tyburczyk, A.

2014-03-01

381

The chemistry of hydrothermal magnetite: a review  

USGS Publications Warehouse

Magnetite (Fe3O4) is a well-recognized petrogenetic indicator and is a common accessory mineral in many ore deposits and their host rocks. Recent years have seen an increased interest in the use of hydrothermal magnetite for provenance studies and as a pathfinder for mineral exploration. A number of studies have investigated how specific formation conditions are reflected in the composition of the respective magnetite. Two fundamental questions underlie these efforts (i) How can the composition of igneous and, more importantly, hydrothermal magnetite be used to discriminate mineralized areas from barren host rocks, and (ii) how can this assist exploration geologists to target ore deposits at greater and greater distances from the main mineralization? Similar to igneous magnetite, the most important factors that govern compositional variations in hydrothermal magnetite are (A) temperature, (B) fluid composition element availability, (C) oxygen and sulfur fugacity, (D) silicate and sulfide activity, (E) host rock buffering, (F) re-equilibration processes, and (G) intrinsic crystallographic controls such as ionic radius and charge balance. We discuss how specific formation conditions are reflected in the composition of magnetite and review studies that investigate the chemistry of hydrothermal and igneous magnetite from various mineral deposits and their host rocks. Furthermore, we discuss the redox-related alteration of magnetite (martitization and mushketovitization) and mineral inclusions in magnetite and their effect on chemical analyses. Our database includes published and previously unpublished magnetite minor and trace element data for magnetite from (1) banded iron formations (BIF) and related high-grade iron ore deposits in Western Australia, India, and Brazil, (2) AgPbZn veins of the Coeur d'Alene district, United States, (3) porphyry Cu(Au)(Mo) deposits and associated (4) calcic and magnesian skarn deposits in the southwestern United States and Indonesia, and (5) plutonic igneous rocks from the Henderson Climax-type Mo deposit, United States, and the un-mineralized Inner Zone Batholith granodiorite, Japan. These five settings represent a diverse suite of geological settings and cover a wide range of formation conditions. The main discriminator elements for magnetite are Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn, and Ga. These elements are commonly present at detectable levels (10 to > 1000 ppm) and display systematic variations. We propose a combination of Ni/(Cr + Mn) vs. Ti + V, Al + Mn vs. Ti + V, Ti/V and Sn/Ga discriminant plots and upper threshold concentrations to discriminate hydrothermal from igneous magnetite and to fingerprint different hydrothermal ore deposits. The overall trends in upper threshold values for the different settings can be summarized as follows: (I) BIF (hydrothermal) low Al, Ti, V, Cr, Mn, Co, Ni, Zn, Ga and Sn; (II) AgPbZn veins (hydrothermal) high Mn and low Ga and Sn; (III) Mg-skarn (hydrothermal) high Mg and Mn and low Al, Ti, Cr, Co, Ni and Ga; (IV) skarn (hydrothermal) high Mg, Al, Cr, Mn, Co, Ni and Zn and low Sn; (V) porphyry (hydrothermal) high Ti and V and low Sn; (VI) porphyry (igneous) high Ti, V and Cr and low Mg; and (VII) Climax-Mo (igneous) high Al, Ga and Sn and low Mg and Cr.

Nadoll, Patrick; Angerer, Thomas; Mauk, Jeffrey L.; French, David; Walshe, John

2014-01-01

382

Simultaneous neutron radiography and infrared thermography measurement of boiling processes  

SciTech Connect

Boiling of water at 1 to 15 bar flowing upward within a narrow duct and a round test section was observed using both neutron radiography and infrared (IR) thermography. The IR readings of the test section outer wall temperatures show the effects of both fluid temperature and wall heat transfer coefficient variations, producing a difference between liquid and two phase regions. The IR images, in fact, appear very similar to the neutron images; both show clear indications of spatial and temporal variations in the internal fluid conditions during the boiling process.

Murphy, J.H.; Glickstein, S.S.

1997-02-01

383

Microscale heat transfer to subcooled water: 200-6,000psia, 0-3,500W/cm2.  

PubMed

Exciting heat transfer phenomena have been discovered with a micron-sized heat transfer element operating in subcooled (20 degrees C) degassed, demineralized water over a wide pressure range (200-6,000psia) at heat fluxes up to 3,500W/cm2. The platinum heat transfer element (diameter 7.5 microns, length 1.14mm) is installed within a one-cm3 stainless steel chamber. Sealed electrical terminals penetrate the chamber to effect direct current heating of the platinum element. Pressure is applied pneumatically. The adiabatic heating rate of the element is 6 degrees C per microsecond at 3,700W/cm2; response is essentially instantaneous for the procedure described herein. The direct current voltage and current are measured from which the power and the resistance (temperature) are determined. The following procedure applies: (1) Pressurize the water-filled stainless steel chamber to 6,000psia. (2) Apply power at 3,000W/cm2. (3) Maintain constant heat flux as pressure is smoothly reduced from 6,000psia to 200psia over a period of 20 seconds. Record voltage, amperage, and pressure at 0.1 second intervals. Heat transfer phenomena thus discovered: (1) Element starting temperature of 370 degrees C at 6,000psia smoothly increased to 380 degrees as pressure was reduced to 3,970psia. (2) At 3,970psia the temperature abruptly stepped upward to 590 degrees C. (3) Temperature smoothly increased to 730 degrees C as pressure was reduced to 3,230psia. (4) In the vicinity of the critical pressure, the temperature turned around and began smoothly decreasing. (5) At 2,350psia, the temperature stepped down from 520 to 350 degrees C. (6) Temperature smoothly decreased to 230 degrees C at 190psia and power was then turned off. Bulk water temperature increased less than 4 degrees C. Controlled gravity (KC-135) tests are planned. PMID:12446329

Leyse, Robert H

2002-10-01

384

Garnet phosphors prepared via hydrothermal synthesis  

SciTech Connect

This project studied hydrothermal synthesis as a route to producing green-emitting cathodoluminescent phosphorus isostructural with yttrium aluminum garnet (Y{sub 3}Al{sub 5}O{sub 12}, or YAG). Aqueous precipitation of Y, Gd, Al, Ga, and Tb salts produced amorphous gels, which were heated with water at 600 C and 3,200 bar to produce crystalline YAG:Tb, Y{sub 3}Ga{sub 5}O{sub 12}:Tb, Y{sub 3}Al{sub 3}Ga{sub 2}O{sub 12}:Tb, and Gd{sub 3}Ga{sub 5}O{sub 12}:Tb powders. Process parameters were identified that yielded submicron YAG:Tb and Y{sub 3}Ga{sub 5}O{sub 12}:Tb powders without grinding. Cathodoluminescent efficiencies were measured as functions of power density at 600 V, using both the hydrothermal garnets and identical phosphor compositions synthesized at high temperatures. Saturation behavior was independent of synthetic technique, however, the hydrothermal phosphorus were less susceptible to damage (irreversible efficiency loss) at very high power densities (up to 0.1 W/cm{sup 2}). The fine grain sizes available with hydrothermal synthesis make it an attractive method for preparing garnet phosphorus for field emission, projection, and head-up displays.

Phillips, M.L.F.; Walko, R.J.; Shea, L.E.

1996-05-01

385

Hydrothermal load flow using functional analysis  

Microsoft Academic Search

The hydrothermal scheduling problem is discussed. Optimal load flow solutions are obtained such that both maximum economy and reliability of the system are achieved. The scheduling problem is solved by use of functional analysis, and in this case the minimum norm formulation is employed. It is emphasized that the optimal solution found here is guaranteed to be the unique optimal

M. E. El-Hawary; G. S. Christensen

1973-01-01

386

Hydrothermal Vent Animals: Distribution and Biology  

Microsoft Academic Search

Hydrothermal vent communities characterized by large clams, mussels, and vestimentiferan worms thrive on chemosynthetic microbial production. There are similarities in the animal distributions at vent communities from 20 degrees S to 46 degrees N on the Mid-Ocean Ridge in the Pacific Ocean and at cold sulfide seeps in the Gulf of Mexico. Vent communities, consisting of at least 16 previously

J. Frederick Grassle

1985-01-01

387

Light at deep sea hydrothermal vents  

Microsoft Academic Search

We usually think of the bottom of the sea as a dark environment, lit only by flashes of bioluminescent light. Discovery of light associated with geothermal processes at deep sea hydrothermal vents forces us to qualify our textbook descriptions of the seafloor as a uniformly dark environment. While a very dim glow emitted from high temperature (350) vents (black smokers)

Cindy Lee Van Dover; J. R. Cann; Colleen Cavanaugh; Steven Chamberlain; John R. Delaney; David Janecky; Johannes Imhoff; J. Anthony Tyson

1994-01-01

388

Physical balances in subseafloor hydrothermal convection cells  

NASA Astrophysics Data System (ADS)

We use a simplified model of convection in a porous medium to investigate the balances of mass and energy within a subseafloor hydrothermal convection cell. These balances control the steady state structure of the system and allow scalings for the height, permeability, and residence time of the "reaction zone" at the base of the cell to be calculated. The scalings are presented as functions of (1) the temperature TD of the heat source driving the convection and (2) the total power output ?U. The model is then used to illustrate how the nonlinear thermodynamic properties of water may impose the observed upper limit of 400C on vent temperatures. The properties of water at hydrothermal conditions are contrasted with those of a hypothetical "Boussinesq fluid" for which temperature variations in fluid properties are either linearized or ignored. At hydrothermal pressures, water transports a maximum amount of energy by buoyancy-driven advection at 400C. This maximum is a consequence of the nonlinear thermodynamic properties of water and does not arise for a simple Boussinesq fluid. Inspired by the "Malkus hypothesis" and by recent work on dissipative systems, we speculate that convection cells in porous media attain a steady state in which the upwelling temperature TU maximizes the total power output of the cell. If true, this principle would explain our observation (in previous numerical simulations) that water in hydrothermal convection cells upwells at TU 400C when driven by a heat source above 500C.

Jupp, Tim E.; Schultz, Adam

2004-05-01

389

The Discovery of Marine Hydrothermal Vents  

NSDL National Science Digital Library

As part of OceanLink, a website dedicated to ocean education, this site gives an overview of the discovery, geology and ecology of marine hydrothermal vents. The site also provides a menu of links to access other OceanLink pages for further ocean-related information.

Oceanlink

390

Fungal colonization of an Ordovician impact-induced hydrothermal system  

PubMed Central

Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown hydrothermal minerals from the 458?Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the hydrothermal activity and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that hydrothermal systems associated with impact structures can support colonization by microbial life.

Ivarsson, Magnus; Broman, Curt; Sturkell, Erik; Ormo, Jens; Siljestrom, Sandra; van Zuilen, Mark; Bengtson, Stefan

2013-01-01

391

Modern methods for hydrothermal synthesis of ZrO 2 -based nanocrystalline powders  

Microsoft Academic Search

Hydrothermal decomposition, hydrothermal crystallization, hydrothermal homogeneous precipitation, microwave hydrothermal synthesis,\\u000a ultrasonic-assisted hydrothermal synthesis, hydrothermal synthesis under supercritical conditions, which are used to produce\\u000a ZrO2-based nanocrystalline powders, are considered. It is established that the nucleation and particle growth can be controlled\\u000a in hydrothermal synthesis (through concentration change, increase or decrease in hydrolysis temperature, increase in hydrolysis\\u000a time, introduction of surface active

E. V. Dudnik

2009-01-01

392

Experimental constraints on hydrothermal activities in Enceladus  

NASA Astrophysics Data System (ADS)

One of the most remarkable findings by the Cassini-Huygens mission is perhaps water-rich plumes erupting from the south-pole region of Enceladus [1]. Given such geological activity and the detection of sodium salts in the plume, the interior of Enceladus is highly likely to contain an interior ocean interacting with the rock core [2]. A primary question regarding astrobiology and planetary science is whether Enceladus has (or had) hydrothermal activities in the interior ocean. Because N2 might be formed by thermal dissociation of primordial NH3 [3], the presence of N2 in the plume may be a possible indicator for the presence of hydrothermal activities in Enceladus. However, the Cassini UVIS revealed that the plumes do not contain large amounts of N2 [4]. Although these observations may not support the presence of hydrothermal activities, whether NH3 dissociation proceeds strongly depends on the kinetics of hydrothermal reactions and interactions with the rock components, which remain largely unknown. Furthermore, the Cassini CDA recently showed that small amounts of SiO2 might have been included in the plume dusts [5]. Formation of amorphous SiO2 usually occurs when high-temperature and/or high-pH solution with high concentrations of dissolved SiO2 cools and/or is neutralized. Thus, the presence of SiO2 in the plume dusts may suggest the presence of a temperature and/or pH gradient in the ocean. However, no laboratory experiments have investigated what processes control pH and SiO2 concentrations in hydrothermal fluids possibly existing in Enceladus. Here, we show the results of laboratory experiments simulating hydrothermal systems on Enceladus. As the initial conditions, we used both aqueous solution of high concentrations (0.01-2%) of NH3 and NaHCO3 and powdered olivine as an analog for the rock components. Our experimental results show that formation of N2 from NH3 is kinetically and thermodynamically inhibited even under high temperature conditions (< 400C). This is because NH3 decomposition proceeds inefficiently due to efficient H2 production via serpentinization. Our experimental results also suggest that SiO2 concentration dissolved in hydrothermal fluids simulating Enceladus' condition would be buffered by the serpentine-brucite system. The presence of NH3 in the hydrothermal conditions keeps pH of the solution high (pH 9-11). We suggest that under such conditions, SiO2 concentrations in the fluids would be 0.1 mmol/L or less for temperature < 350C. Given the SiO2 solubility of 1-10 mmol/L at 0C and pH 9-11, direct formation of amorphous SiO2 would not occur in Enceladus' hydrothermal systems. To produce amorphous SiO2, large-scale hydrothermal activities and subsequent concentration of dissolved SiO2 in the ocean (due to freezing and/or evaporation of liquid water) would be required, which is consistent with high concentrations of radiogenic Ar and sodium salts in the plume [2, 6]. [1] Porco et al., Science 311, 1393 (2006). [2] Postberg et al., Nature 459, 1098 (2009). [3] Matson et al., Icarus 187, 569 (2007). [4] Hansen t al., Geophs. Res. Lett. 38, L11202 (2011). [5] Hsu et al., EOS Trans. AGU, (2010). [6] Waite et al., Nature 460, 487 (2009).

Sekine, Y.; Shibuya, T.; Suzuki, K.; Kuwatani, T.

2012-12-01

393

78 FR 46378 - La Crosse Boiling Water Reactor, Environmental Assessment and Finding of No Significant Impact...  

Federal Register 2010, 2011, 2012, 2013

...NRC-2013-0168] La Crosse Boiling Water Reactor, Environmental Assessment and Finding of No Significant Impact Regarding an Exemption Request AGENCY...10 CFR) for the La Crosse Boiling Water Reactor (LACBWR) facility and...

2013-07-31

394

76 FR 61118 - Meeting of the ACRS Subcommittee on Advanced Boiling Water Reactor; Notice of Meeting  

Federal Register 2010, 2011, 2012, 2013

...REGULATORY COMMISSION Advisory Committee on Reactor Safeguards (ACRS) Meeting of the ACRS Subcommittee on Advanced Boiling Water Reactor; Notice of Meeting The ACRS Subcommittee on Advanced Boiling Water Reactor (ABWR) will hold a meeting on...

2011-10-03

395

46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.  

Code of Federal Regulations, 2010 CFR

...boil-off as fuel: Gas detection equipment. 154.709...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required under...in the wheelhouse if the methane concentration reaches...

2010-10-01

396

46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.  

Code of Federal Regulations, 2010 CFR

...boil-off as fuel: Gas detection equipment. 154.709...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required under...in the wheelhouse if the methane concentration reaches...

2009-10-01

397

46 CFR 154.709 - Cargo boil-off as fuel: Gas detection equipment.  

Code of Federal Regulations, 2013 CFR

...boil-off as fuel: Gas detection equipment. 154.709...boil-off as fuel: Gas detection equipment. (a) The continuous gas detection system required under...in the wheelhouse if the methane concentration reaches...

2013-10-01

398

Hydrothermal systems in small ocean planets.  

PubMed

We examine means for driving hydrothermal activity in extraterrestrial oceans on planets and satellites of less than one Earth mass, with implications for sustaining a low level of biological activity over geological timescales. Assuming ocean planets have olivine-dominated lithospheres, a model for cooling-induced thermal cracking shows how variation in planet size and internal thermal energy may drive variation in the dominant type of hydrothermal system-for example, high or low temperature system or chemically driven system. As radiogenic heating diminishes over time, progressive exposure of new rock continues to the current epoch. Where fluid-rock interactions propagate slowly into a deep brittle layer, thermal energy from serpentinization may be the primary cause of hydrothermal activity in small ocean planets. We show that the time-varying hydrostatic head of a tidally forced ice shell may drive hydrothermal fluid flow through the seafloor, which can generate moderate but potentially important heat through viscous interaction with the matrix of porous seafloor rock. Considering all presently known potential ocean planets-Mars, a number of icy satellites, Pluto, and other trans-neptunian objects-and applying Earth-like material properties and cooling rates, we find depths of circulation are more than an order of magnitude greater than in Earth. In Europa and Enceladus, tidal flexing may drive hydrothermal circulation and, in Europa, may generate heat on the same order as present-day radiogenic heat flux at Earth's surface. In all objects, progressive serpentinization generates heat on a globally averaged basis at a fraction of a percent of present-day radiogenic heating and hydrogen is produced at rates between 10(9) and 10(10) molecules cm(2) s(1). PMID:18163874

Vance, Steve; Harnmeijer, Jelte; Kimura, Jun; Hussmann, Hauke; Demartin, Brian; Brown, J Michael

2007-12-01

399

Geochemical and isotopic evidence for seawater contamination of the hydrothermal system of Taal Volcano, Luzon, the Philippines  

NASA Astrophysics Data System (ADS)

The hydrologic structure of Taal Volcano has favored development of an extensive hydrothermal system whose prominent feature is the acidic Main Crater Lake (pH<3) lying in the center of an active vent complex, which is surrounded by a slightly alkaline caldera lake (Lake Taal). This peculiar situation makes Taal prone to frequent, and sometimes catastrophic, hydrovolcanic eruptions. Fumaroles, hot springs, and lake waters were sampled in 1991, 1992, and 1995 in order to develop a geochemical model for the hydrothermal system. The low-temperature fumarole compositions indicate strong interaction of magmatic vapors with the hydrothermal system under relatively oxidizing conditions. The thermal waters consist of highly, moderately, and weakly mineralized solutions, but none of them corresponds to either water-rock equilibrium or rock dissolution. The concentrated discharges have high Na contents (>3500mg/kg) and low SO4/Cl ratios (<0.3). The Br/Cl ratio of most samples suggests incorporation of seawater into the hydrothermal system. Water and dissolved sulfate isotopic compositions reveal that the Main Crater Lake and spring discharges are derived from a deep parent fluid (T 300 C), which is a mixture of seawater, volcanic water, and Lake Taal water. The volcanic endmember is probably produced in the magmatic-hydrothermal environment during absorption of high-temperature gases into groundwater. Boiling and mixing of the parent water give rise to the range of chemical and isotopic characteristics observed in the thermal discharges. Incursion of seawater from the coastal region to the central part of the volcano is supported by the low water levels of the lakes and by the fact that Lake Taal was directly connected to the China sea until the sixteenth century. The depth to the seawater-meteoric water interface is calculated to be 80 and 160m for the Main Crater Lake and Lake Taal, respectively. Additional data are required to infer the hydrologic structure of Taal. Geochemical surveillance of the Main Crater Lake using the SO4/Cl, Na/K, or Mg/Cl ratio cannot be applied straightforwardly due to the presence of seawater in the hydrothermal system.

Delmelle, Pierre; Kusakabe, Minoru; Bernard, Alain; Fischer, Tobias; de Brouwer, Simon; del Mundo, Esfeca

400

Characteristic boiling curve of carbon nanotube nanofluid as determined by the transient calorimeter technique  

NASA Astrophysics Data System (ADS)

Nickel-plated copper sphere is employed as the transient calorimeter to explore the boiling heat transfer characteristics of carbon nanotube (CNT) nanofluid. As compared to water, aqueous gum arabic (GA) solution has an enhanced critical heat flux (CHF), transition boiling, and minimum heat flux in film boiling (Leidenfrost point). CNT nanofluid has higher CHF than GA solution. Better wettability and deposits on the heating surface distort the characteristic boiling curve.

Xue, H. S.; Fan, J. R.; Hong, R. H.; Hu, Y. C.

2007-04-01

401

Relict hydrothermal zones in the TAG Hydrothermal Field, Mid-Atlantic Ridge 26N, 45W  

NASA Astrophysics Data System (ADS)

Two relict hydrothermal zones were delineated between water depths of 3400 and 3500 m at the lower part of the east wall of the rift valley of the Mid-Atlantic Ridge in the TAG hydrothermal field using a deep-towed side scan sonar tow and a camera-temperature tow along the northern 3 km of the wall, and a submersible transect. Named the North and MIR relict zones, they are located about 4 km and 2 km northeast, respectively, of the known active high-temperature sulfide mound between water depths of 3625 and 3670 m on the rift valley floor near the base of the east wall. The North zone extends about 2 km along the northern end of the lower east wall. The zone includes two moundlike features up to 30 m high by 200 m in diameter imaged by side scan sonar within a 2-km-long line of discontinuous hydrothermal deposits comprising inactive toppled and standing chimneys, layered material, and patchy dark stains on sediment photographed by the camera-temperature tow. Several other moundlike features were imaged with the side scan sonar outside of the photographic coverage. The MIR relict hydrothermal zone 2 km south of the North zone, named after the MIR submersible used to investigate it, consists of three subzones: (1) a 200-m-wide area of diverse types of hydrothermal materials exposed by normal faulting at its western margin; (2) a 400-m-wide by 700-m-long central area of discrete groups of toppled and standing inactive sulfide chimneys up to 25 m high on a substrate of red metalliferous sediment and carbonate lutite; spires sampled on the highest chimneys are composed of coarse-grained, recrystallized sulfides dominated by pyrite and chalcopyrite which contain the first primary, free gold grains (2-3 ?m diameter) found at a hydrothermal site on a mid-ocean ridge; and (3) a 150-m-wide hummocky area of layered hydrothermal material with the appearance of low temperature precipitates and carbonate lutite with patchy dark stains at its eastern margin. The active sulfide mound, the North zone, and the MIR zone are each located on the fractured western margins of gentle, dome-shaped areas of pillow flows typically 500 m in diameter interpreted as summits of volcanic centers that may have supplied heat to drive adjacent hydrothermal activity. The distribution and size of the active and inactive hydrothermal zones of the TAG field, the chronology, and the characteristics of relict samples recovered indicate a history of at least 100 103 years of high-temperature hydrothermal episodes with multiple overprinting stages of mineralization accompanied by alteration.

Rona, Peter A.; Bogdanov, Yury A.; Gurvich, Evengy G.; Rimski-Korsakov, Nick A.; Sagalevitch, Anatoly M.; Hannington, Mark D.; Thompson, Geoffrey

1993-06-01

402

Experimental demonstration of contaminant removal from fractured rock by boiling.  

PubMed

This study was conducted to experimentally demonstrate removal of a chlorinated volatile organic compound from fractured rock by boiling. A Berea sandstone core was contaminated by injecting water containing dissolved 1,2-DCA (253 mg/L) and sodium bromide (144 mg/L). During heating, the core was sealed except for one end, which was open to the atmosphere to simulate an open fracture. A temperature gradient toward the outlet was observed when boiling occurred in the core. This indicates that steam was generated and a pressure gradient developed toward the outlet, pushing steam vapor and liquid water toward the outlet. As boiling occurred, the concentration of 1,2-DCA in the condensed effluent peaked up to 6.1 times higher than the injected concentration. When 38% of the pore volume of condensate was produced, essentially 100% of the 1,2-DCA was recovered. Nonvolatile bromide concentration in the condensate was used as an indicator of the produced steam quality (vapor mass fraction) because it can only be removed as a solute, and not as a vapor. A higher produced steam quality corresponds to more concentrated 1,2-DCA removal from the core, demonstrating that the chlorinated volatile compound is primarily removed by partitioning into vapor phase flow. This study has experimentally demonstrated that boiling is an effective mechanism for CVOC removal from the rock matrix. PMID:20666474

Chen, Fei; Liu, Xiaoling; Falta, Ronald W; Murdoch, Lawrence C

2010-08-15

403

Characterizing preferential groundwater discharge through boils using temperature  

NASA Astrophysics Data System (ADS)

Preferential seepage results in a surface water and groundwater temperature anomaly.Water with mean groundwater temperature is discharged to the surface water.Lines of equal groundwater temperature are distorted towards the boil.There are distinct differences between solute and heat transport.

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

2014-03-01

404

The hen's egg: Factors affecting shell splitting during boiling  

Microsoft Academic Search

Experiments are described from which it is concluded that the shell will split when an egg is boiled if thermal expansion of the egg's liquid or gaseous contents, which have a higher coefficient of expansion than the shell, is insufficiently relieved by escape through the membranes and pores. The probability of splitting was enhanced if the shell had low structural

T. G. Carter

1972-01-01

405

Current Status of the Post Boiling Transition Research in Japan  

Microsoft Academic Search

Development of rewetting correlation formula was the key to predict fuel-cladding temperature after Boiling Transition (BT). Japanese BWR utilities and vendors performed some tests of rewetting and made two rewetting correlation formulas. The effect on fuel integrity after BT depends on temperature of fuel rod and time of dryout. Main cause of losing fuel integrity during BWR's Anticipated Operational Occurrences

Takashi HARA; Shinya MIZOKAMI; Yoshiro KUDO; Seiichi KOMURA; Yoshifumi NAGATA; Shinichi MOROOKA

2003-01-01

406

Arrangement of boiling liquid cooling system of internal combustion engine  

Microsoft Academic Search

This patent describes a motor vehicle having an internal combustion engine mounted in an engine room of a vehicle body comprising: a boiling liquid cooling system associated with the engine for cooling the same by using a latent heat of coolant, which comprises: means for defining in the engine proper a coolant jacket which contains therein a liquid coolant leaving

Hayashi

1986-01-01

407

Research on radiation detectors, boiling transients, and organic lubricants  

NASA Technical Reports Server (NTRS)

The accomplishments of a space projects research facility are presented. The subjects discussed are: (1) a study of radiation resistant semiconductor devices, (2) synthesis of high temperature organic lubricants, (3) departure from phase equilibrium during boiling transients, (4) effects of neutron irradiation on defect state in tungsten, and (5) determination of photon response function of NE-213 liquid scintillation detectors.

1974-01-01

408

Boiling heat transfer and droplet spreading of nanofluids.  

PubMed

Nanofluids- a new class of heat transfer fluids have recently been a very attractive area of research due to their fascinating thermophysical properties and numerous potential benefits and applications in many important fields. However, there are many controversies and inconsistencies in reported arguments and experimental results on various thermal characteristics such as effective thermal conductivity, convective heat transfer coefficient and boiling heat transfer rate of nanofluids. As of today, researchers have mostly focused on anomalous thermal conductivity of nanofluids. Although investigations on boiling and droplet spreading are very important for practical application of nanofluids as advanced coolants, considerably fewer efforts have been made on these thermal features of nanofluids. In this paper, recent research and development in boiling heat transfer and droplet spreading of nanofluids are reviewed together with summarizing most related patents on nanofluids published in literature. Review reveals that despite some inconsistent results nanofluids exhibit significantly higher boiling heat transfer performance compared to their base fluids and show great promises to be used as advanced heat transfer fluids in numerous applications. However, there is a clear lack of in-depth understanding of heat transport mechanisms during phase change of nanofluids. It is also found that the nanofluids related patents are limited and among them most of the patents are based on thermal conductivity enhancement and synthesising processes of specific type of nanofluids. PMID:24330044

Murshed, S M Sohel; de Castro, C A Nieto

2013-11-01

409

Small circular- and rectangular-channel boiling with two refrigerants  

Microsoft Academic Search

Boiling heat transfer experiments were performed in a small circular channel (d = 2.46) and a small rectangular channel (dh = 2.40 mm) with Refrigerant 12. The channel sizes are representative of flow passages in compact evaporators. An experimental technique minimized test section end effects which can be appreciable relative to the heat transfer in these small channels. Local heat

T. N. Tran; M. W. Wambsganss; D. M. France

1996-01-01

410

Liquid resupply effects in macrolayer-controlled nucleate boiling.  

National Technical Information Service (NTIS)

Previous studies of the high-heat-flux nucleate boiling regime have made widely varying assumptions about the state of the macrolayer at the beginning of the hovering period of the mushroom bubbles overlying the macrolayer. The uncertainty in the initial ...

P. Sadasivan C. Unal R. A. Nelson

1993-01-01

411

Characterization of Convective Boiling in Branching Channel Heat Sinks.  

National Technical Information Service (NTIS)

Convective boiling and gas-liquid flows in branching microscale flow networks within disk-shaped heat sinks were studied experimentally. Void fraction and flow regime variations as a function of branch level were reported for gas-liquid flows and compared...

D. V. Pence J. A. Liburdy V. Narayanan

2009-01-01

412

Reduced Boiling and Cooling Times for the Waferboard Bending Test.  

National Technical Information Service (NTIS)

The boiling and cooling limits recommended by Canadian Waferboard Standard (CAN-0188.0-M78) are too long for efficient in-plant quality control. For this reason a systematic study has been conducted to determine whether test results obtained after reduced...

P.C.L. Gaudert T. Szabo

1980-01-01

413

Electrochemical study of aluminum corrosion in boiling high purity water  

NASA Technical Reports Server (NTRS)

Electrochemical study of aluminum corrosion in boiling high-purity water includes an equation relating current and electrochemical potential derived on the basis of a physical model of the corrosion process. The work involved an examination of the cathodic polarization behavior of 1100 aluminum during aqueous oxidation.

Draley, J. E.; Legault, R. A.

1969-01-01

414

Design Challenge: How to Keep Items Cool in Boiling Water?  

NSDL National Science Digital Library

This is a design challenge about heat transfer and insulation. Learners will apply the scientific method to design and build a container that will keep items cool when placed in boiling water. They will practice collaboration in team-building and in teamwork. This is lesson 4 of 4 at the Grade 9-12 range of the module, Staying Cool.

415

Isotope hydrology of El Chichn volcano-hydrothermal system; a coupled system of crater lake and hot springs  

NASA Astrophysics Data System (ADS)

The catastrophic 1982 eruption of El Chichn (>1.5 km3 of erupted material) opened the upper hundred meters of the existing volcano-hydrothermal system. In the new formed 200m-deep crater a large shallow crater lake and numerous hot springs were formed. The lake existence and its salinity depend on the precipitation (~4000 mm/y) as well as a group of geyser-like neutral saline springs (source of Cl and SO4) and hydrothermal steam vents discharging into the lake (source of SO4). The chemistry of these Soap Pool (SP) springs evolved from >13,000 ppm of Cl in 1995 to ~2000-3000 ppm of Cl in 2006. Since 2006, this Cl-concentration in SP waters is constant. Similar concentrations of Cl are observed in most flank hot springs located at altitudes of ~ 600 m asl, 2-3 km from the crater. Therefore, it can be suggested that the flank springs, crater lake and crater hot springs are manifestations of the upper, relatively shallow volcano-hydrothermal system developed beneath the crater in the volcano edifice. Water isotopic composition of all types of thermal and fresh waters including fumarolic steam condensates (>100 samples collected in 1995-2010) allow to classify and distinguish different processes of shallow mixing, boiling, evaporation and water-rock isotope exchange. All spring waters from the upper system have meteoric origin, with the isotopic composition plotting close to the meteoric water line. Crater waters are strongly evolved due to shallow boiling and loss of steam. Isotopic composition of water from the lower, deep hydrothermal system is characterized by a significant positive oxygen isotopic shift and a strong Cl-d18O linear correlation. Waters from numerous cold springs that drain pyroclastic deposits demonstrate a clear negative oxygen shift. Some problems related to water isotopic composition are still remain unresolved: (1) we cannot find any traces of the infiltrated isotopically heavy lake waters, i.e., the seepage from the lake at the volcano slopes; and (2) we cannot explain the constancy and independence of d18O values (-21 ) of SP springs from Cl concentration which varied from 13,000 to 2,000 ppm over the observation time.

Peiffer, L.; Taran, Y.; Rouwet, D.

2010-12-01

416

Nucleate pool boiling heat transfer in aqueous surfactant solutions  

NASA Astrophysics Data System (ADS)

Saturated, nucleate pool boiling in aqueous surfactant solutions is investigated experimentally. Also, the role of Marangoni convection, driven both by temperature and surfactant concentration gradients at the vapor-liquid interface of a nucleating bubble is computationally explored. Experimental measurements of dynamic and equilibrium sigma using the maximum bubble pressure method indicate dynamic sigma to be higher than the corresponding equilibrium value, both at room and elevated temperatures. Also, nonionic surfactants (Triton X-100, Triton X-305) show larger sigma depression than anionic surfactants (SDS, SLES), and a normalized representation of their dynamic adsorption isotherms is shown to be helpful in generalizing the surfactant effectiveness to reduce surface tension. The dynamic sigma has a primary role in the modification of bubble dynamics and associated heat transfer, and is dictated by the adsorption kinetics of the surfactant molecules at boiling temperatures. In general, an enhancement in heat transfer is observed, which is characterized by an early incipience and an optimum boiling performance at or around the critical micelle concentration of the surfactant. The optimum performances, typically in the fully developed boiling regime ( q''w > 100 kW/m2), show a reverse trend with respect to surfactant molecular weights M, i.e., higher molecular weight additives promote lower enhancement. Normalized boiling performance using the respective solution's dynamic sigma correlates heat transfer coefficient by M-0.5 for anionics and M 0 for nonionics. This has been shown to be brought about by the surfactant concentration and its interfacial activity in a concentration sublayer around the growing vapor bubble, which governs the bubble growth behavior through the mechanism of dynamic sigma. The ionic nature of the surfactant influences the thickness and molecular ma