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1

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

2

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

3

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

4

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.

5

Method for calibrating copper-constantan thermocouples at negative temperatures by means of the boiling point of water  

Microsoft Academic Search

Conclusions 1.The suggested method for calibrating copper-constantan thermocouples is based on the linear relationship of corrections to the corresponding thermal emf evaluated at a single point.2.Temperatures in the negative range (0 to -200C) are calibrated by means of the boiling point of water with an error of 0.3C.3.The interpolation of the thermal emf in the range from zero to the

A. P. Bondareva

1969-01-01

6

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

7

Reorientational dynamics in molecular liquids as revealed by dynamic light scattering: from boiling point to glass transition temperature.  

PubMed

We determine the reorientational correlation time ? of a series of molecular liquids by performing depolarized light scattering experiments (double monochromator, Fabry-Perot interferometry, and photon correlation spectroscopy). Correlation times in the range 10(-12) s-100 s are compiled, i.e., the full temperature interval between the boiling point and the glass transition temperature T(g) is covered. We focus on low-T(g) liquids for which the high-temperature limit ? ? 10(-12) s is easily accessed by standard spectroscopic equipment (up to 440 K). Regarding the temperature dependence three interpolation formulae of ?(T) with three parameters each are tested: (i) Vogel-Fulcher-Tammann equation, (ii) the approach recently discussed by Mauro et al. [Proc. Natl. Acad. Sci. U.S.A. 106, 19780 (2009)], and (iii) our approach decomposing the activation energy E(T) in a constant high temperature value E? and a "cooperative part" E(coop)(T) depending exponentially on temperature [Schmidtke et al., Phys. Rev. E 86, 041507 (2012)]. On the basis of the present data, approaches (i) and (ii) are insufficient as they do not provide the correct crossover to the high-temperature Arrhenius law clearly identified in the experimental data while approach (iii) reproduces the salient features of ?(T). It allows to discuss the temperature dependence of the liquid's dynamics in terms of a E(coop)(T)/E? vs. T/E? plot and suggests that E? controls the energy scale of the glass transition phenomenon. PMID:24007015

Schmidtke, B; Petzold, N; Kahlau, R; Rssler, E A

2013-08-28

8

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

9

Excess Heat in Heavy WATER-Pd/C Catalyst Cathode Case-Type Electrolysis at the Temperature Near the Boiling Point  

NASA Astrophysics Data System (ADS)

At high temperatures, the Pd/C catalyst cathode (Case-type) electrolysis in heavy water might produce more excess heat than at room temperature. While the "excess heat" in Case-type experiment was apparently confirmed at the higher temperature, the method raised new problems with electrolysis near boiling temperatures.

Wei, Qing M.; Li, Xing Z.; Cui, Yan O.

2005-12-01

10

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

11

Life above the boiling point of water?  

Microsoft Academic Search

Summary Various extremely thermophilic archaebacteria exhibit optimum growth at above 80C.Pyrodictium is the most thermophilic of these organisms, growing at temperatures of up to 110C and exhibiting optimum growth at about 105C. All of these organisms grow by diverse types of anaerobic and aerobic metabolism.

K. O. Stetter; G. Fiala; R. Huber; G. Huber; A. Segerer

1986-01-01

12

Prediction of boiling points of organic compounds by QSPR tools.  

PubMed

The novel electro-negativity topological descriptors of YC, WC were derived from molecular structure by equilibrium electro-negativity of atom and relative bond length of molecule. The quantitative structure-property relationships (QSPR) between descriptors of YC, WC as well as path number parameter P3 and the normal boiling points of 80 alkanes, 65 unsaturated hydrocarbons and 70 alcohols were obtained separately. The high-quality prediction models were evidenced by coefficient of determination (R(2)), the standard error (S), average absolute errors (AAE) and predictive parameters (Qext(2),RCV(2),Rm(2)). According to the regression equations, the influences of the length of carbon backbone, the size, the degree of branching of a molecule and the role of functional groups on the normal boiling point were analyzed. Comparison results with reference models demonstrated that novel topological descriptors based on the equilibrium electro-negativity of atom and the relative bond length were useful molecular descriptors for predicting the normal boiling points of organic compounds. PMID:23792208

Dai, Yi-min; Zhu, Zhi-ping; Cao, Zhong; Zhang, Yue-fei; Zeng, Ju-lan; Li, Xun

2013-07-01

13

Smoothing strategies for surface temperatures measured during vigorous transient boiling  

SciTech Connect

A vertically oriented hollow nickel cylinder (0.15-m dia, 0.3-m height, 0.095-m wall thickness) has been quenched in cold (22 {degree}C) water from an initial temperature of 810{degree}C. During the quench, the output from surface-mounted intrinsic thermocouples was digitized and recorded at intervals of 0.004 s over a test period of 40 s. The output from one of these thermocouples is examined in detail. A procedure for smoothing and interpreting the output is developed. The raw thermocouple signals exhibit three distinct regimes, stable film boiling (surface temperatures of above 400{degree}C), unstable film boiling (400{degree} to 120-140{degree}C), and nucleate boiling. In the first and second regimes, the data show fluctuations of {plus minus}50{degree}C that are attributed to formation and collapse of bubbles on the vertical surface of the cylinder. Because the measurements are ultimately to be used to predict surface heat fluxes, the high-frequency fluctuations must be removed or averaged without destroying the transient character of the cooling curve. Three strategies are discussed: (1) Beck's Second Inverse Heat Conduction method, (2) a moving window with a linear least-mean-squares (LMS) fit to replace each point in turn, and (3) Fourier series with the highest frequencies deleted from the spectrum before reconstructing the signals. The experiments are summarized, the raw data are analyzed, the methods are explained, and results using each of the methods are presented and discussed. 13 refs., 10 figs.

Park, J.E.; Chu, W.; Ludtka, G.M.

1990-01-01

14

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

15

Design of Ultrasonically-Activatable Nanoparticles using Low Boiling Point Perfluorocarbons  

PubMed Central

Recently, an interest has developed in designing in biomaterials for medical ultrasonics that can provide the acoustic activity of microbubbles, but with improved stability in vivo and a smaller size distribution for extravascular interrogation. One proposed alternative is the phase-change contrast agent. Phase-change contrast agents (PCCAs) consist of perfluorocarbons (PFCs) that are initially in liquid form, but can then be vaporized with acoustic energy. Crucial parameters for PCCAs include their sensitivity to acoustic energy, their size distribution, and their stability, and this manuscript provides insight into the custom design of PCCAs for balancing these parameters. Specifically, the relationship between size, thermal stability and sensitivity to ultrasound as a function of PFC boiling point and ambient temperature is illustrated. Emulsion stability and sensitivity can be tuned by mixing PFCs in the gaseous state prior to condensation. Novel observations illustrate that stable droplets can be generated from PFCs with extremely low boiling points, such as octafluoropropane (b.p. ?36.7C), which can be vaporized with acoustic parameters lower than previously observed. Results demonstrate the potential for low boiling point PFCs as a useful new class of compounds for activatable agents, which can be tailored to the desired application.

Sheeran, Paul S.; Luois, Samantha; Mullin, Lee; Matsunaga, Terry O.

2012-01-01

16

Teaching Structure-Property Relationships: Investigating Molecular Structure and Boiling Point  

ERIC Educational Resources Information Center

A concise, well-organized table of the boiling points of 392 organic compounds has facilitated inquiry-based instruction in multiple scientific principles. Many individual or group learning activities can be derived from the tabulated data of molecular structure and boiling point based on the instructor's education objectives and the students'

Murphy, Peter M.

2007-01-01

17

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

18

TRANSPORT OF HIGH BOILING POINT FIRE SUPPRESSANTS IN A DROPLET-LADEN HOMOGENEOUS TURBULENT FLOW PAST A CYLINDER  

Microsoft Academic Search

Liquid agent transport was investigated around unheated and heated horizontal cylinders (to a near-surface temperature of approximately 423 K, i.e., well above the water boiling point) under ambient conditions. Experimental results are presented for a well-characterized, droplet-laden homogenous turbulent flow field, using water, methoxy-nonafluorobutane (i.e., HFE-7100, C4F9OCH3, with a boiling point of 334 K), and 1-methoxyheptafluoropropane (i.e., HFE-7000, C3F7OCH3, with

Cary Presser; C. T. Avedisian

2006-01-01

19

Observations of high temperature impinging-jet boiling phenomena  

Microsoft Academic Search

A high-speed video camera and microphone were used to capture the flow behavior and boiling sound of a free-surface water jet impinging on a high temperature surface during quench cooling. It was found that depending on the superheat of the surface considerably different flow patterns appeared. For cases where the initial surface temperature was above about 300C an almost explosive

Peter Lloyd Woodfield; Masanori Monde; Aloke Kumar Mozumder

2005-01-01

20

Characterization of the TIP4P-Ew water model: Vapor pressure and boiling point  

NASA Astrophysics Data System (ADS)

The liquid-vapor-phase equilibrium properties of the previously developed TIP4P-Ew water model have been studied using thermodynamic integration free-energy simulation techniques in the temperature range of 274-400 K. We stress that free-energy results from simulations need to be corrected in order to be compared to the experiment. This is due to the fact that the thermodynamic end states accessible through simulations correspond to fictitious substances (classical rigid liquids and classical rigid ideal gases) while experiments operate on real substances (liquids and real gases, with quantum effects). After applying analytical corrections the vapor pressure curve obtained from simulated free-energy changes is in excellent agreement with the experimental vapor pressure curve. The boiling point of TIP4P-Ew water under ambient pressure is found to be at 370.3+/-1.9 K, about 7 K higher than the boiling point of TIP4P water (363.7+/-5.1 K from simulations that employ finite range treatment of electrostatic and Lennard-Jones interactions). This is in contrast to the approximately +15 K by which the temperature of the density maximum and the melting temperature of TIP4P-Ew are shifted relative to TIP4P, indicating that the temperature range over which the liquid phase of TIP4P-Ew is stable is narrower than that of TIP4P and resembles more that of real water. The quality of the vapor pressure results highlights the success of TIP4P-Ew in describing the energetic and entropic aspects of intermolecular interactions in liquid water.

Horn, Hans W.; Swope, William C.; Pitera, Jed W.

2005-11-01

21

Characterization of the TIP4P-Ew water model: vapor pressure and boiling point.  

PubMed

The liquid-vapor-phase equilibrium properties of the previously developed TIP4P-Ew water model have been studied using thermodynamic integration free-energy simulation techniques in the temperature range of 274-400 K. We stress that free-energy results from simulations need to be corrected in order to be compared to the experiment. This is due to the fact that the thermodynamic end states accessible through simulations correspond to fictitious substances (classical rigid liquids and classical rigid ideal gases) while experiments operate on real substances (liquids and real gases, with quantum effects). After applying analytical corrections the vapor pressure curve obtained from simulated free-energy changes is in excellent agreement with the experimental vapor pressure curve. The boiling point of TIP4P-Ew water under ambient pressure is found to be at 370.3+/-1.9 K, about 7 K higher than the boiling point of TIP4P water (363.7+/-5.1 K; from simulations that employ finite range treatment of electrostatic and Lennard-Jones interactions). This is in contrast to the approximately +15 K by which the temperature of the density maximum and the melting temperature of TIP4P-Ew are shifted relative to TIP4P, indicating that the temperature range over which the liquid phase of TIP4P-Ew is stable is narrower than that of TIP4P and resembles more that of real water. The quality of the vapor pressure results highlights the success of TIP4P-Ew in describing the energetic and entropic aspects of intermolecular interactions in liquid water. PMID:16321097

Horn, Hans W; Swope, William C; Pitera, Jed W

2005-11-15

22

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

23

Rapid measurement of boiling points and vapor pressure of binary mixtures of short-chain triglycerides by TGA method  

Microsoft Academic Search

Thermogravimetric analysis (TGA), has been used to rapidly obtain data on the temperature dependence of vapor pressure (760, down to 20mmHg) and the boiling points for simple binary mixtures of tributyrin (C4:0), tricaproin (C6:0) and\\/or tricaprylin (C8:0). Vapor-pressure measurements were taken for binary mixtures of the aforementioned compounds as a function of mole fraction. Additional measurements of methyl esters of

J. W Goodrum; D. P Geller; S. A Lee

1998-01-01

24

What Is the Boiling Point and Heat of Vaporization of Sulfuric Acid?  

ERIC Educational Resources Information Center

Discusses the values presented in various handbooks for the boiling point and heat of vaporization of sulfuric acid, noting discrepencies. Analyzes various approaches to data presentation, discussing the data on sulfuric acid in light of the Trouton constant. Points out the need for a more critical use of tables. (JM)

Myers, R. Thomas

1983-01-01

25

Parabolic Behavior of Melting and Boiling Points versus Coulomb Potential in Ionic Substances  

Microsoft Academic Search

Melting points and boiling points of alkali fluorides, alkali chlorides, alkali bromides and alkali iodides, have been found to form parabolas as a function of Coulomb energy x{=}q2\\/(rc+ra). Melting points versus x for oxides of cations with rare gas-type outer electronic shells have been found to behave similarly. A primary explanation of such parabolic behaviors of melting points versus x

Tetsuro Nakamura; Yoshiki Takagi

1980-01-01

26

Boiling point determination using adiabatic Gibbs ensemble Monte Carlo simulations: Application to metals described by embedded-atom potentials  

NASA Astrophysics Data System (ADS)

The normal boiling points are obtained for a series of metals as described by the ``quantum-corrected Sutton Chen'' (qSC) potentials [S.-N. Luo, T. J. Ahrens, T. a??n, A. Strachan, W. A. Goddard III, and D. C. Swift, Phys. Rev. B 68, 134206 (2003)]. Instead of conventional Monte Carlo simulations in an isothermal or expanded ensemble, simulations were done in the constant-NPH adabatic variant of the Gibbs ensemble technique as proposed by Kristf and Liszi [Chem. Phys. Lett. 261, 620 (1996)]. This simulation technique is shown to be a precise tool for direct calculation of boiling temperatures in high-boiling fluids, with results that are almost completely insensitive to system size or other arbitrary parameters as long as the potential truncation is handled correctly. Results obtained were validated using conventional NVT-Gibbs ensemble Monte Carlo simulations. The qSC predictions for boiling temperatures are found to be reasonably accurate, but substantially underestimate the enthalpies of vaporization in all cases. This appears to be largely due to the systematic overestimation of dimer binding energies by this family of potentials, which leads to an unsatisfactory description of the vapor phase.

Gelb, Lev D.; Chakraborty, Somendra Nath

2011-12-01

27

THE MEASUREMENT OF RAPID SURFACE TEMPERATURE FLUCTUATIONS DURING NUCLEATE BOILING OF WATER  

Microsoft Academic Search

The surface temperature during nucleate boiling was measured with a ; special thermocouple so designed as to measure the temperature of a small area ; and to have an extremely rapid response time. The surface temperature was found ; to drop occasionally 20 to 30 deg F in about 2 msec during the boiling of water. ; This indicates a

Franklin D. Moore; Russell B. Mesler

1961-01-01

28

Comparative Biology and Chemistry of Boiling Point Fractions from Different Coal Liquefaction Processes.  

National Technical Information Service (NTIS)

Data on the chemical composition and toxicologic activity of narrow boiling point (bp) range distillate cuts from the non-catalytic solvent refined coal-I and -II processes, as well as from the catalytic H-Coal, EDS, and integrated two-stage liquefaction ...

C. W. Wright E. K. Chess D. L. Stewart D. D. Mahlum D. W. Later

1985-01-01

29

Flow boiling heat transfer characteristics of CO 2 at low temperatures  

Microsoft Academic Search

This paper presents an overview of the flow boiling heat transfer characteristics and the special thermo-physical properties of CO2 at low temperatures (down to ?30C). Subsequently, the boiling heat transfer of CO2 at low temperatures is experimentally investigated in a horizontal tube with inner diameter of 4.57mm. Due to the large surface tension, the boiling heat transfer coefficient of CO2

Xiumin Zhao; P. K. Bansal

2007-01-01

30

Experimental Investigation on Flow Boiling Heat Transfer of CO2 at Low Temperatures  

Microsoft Academic Search

There is a growing use of CO2 refrigeration to achieve low temperatures, particularly in the food industry; however, very limited information is available in the open literature on its boiling heat transfer characteristics below 30C. This paper investigates experimentally the flow boiling heat transfer of CO2 at low temperatures down to 40C. The experimental data were collected from a novel

Xiumin Zhao; Pradeep Bansal

2009-01-01

31

Dynamic analysis of multiple nuclear-coupled boiling channels based on a multi-point reactor model  

Microsoft Academic Search

This work investigates the non-linear dynamics and stabilities of a multiple nuclear-coupled boiling channel system based on a multi-point reactor model using the Galerkin nodal approximation method. The nodal approximation method for the multiple boiling channels developed by Lee and Pan [Lee, J.D., Pan, C., 1999. Dynamics of multiple parallel boiling channel systems with forced flows. Nucl. Eng. Des. 192,

Jin Der Lee; Chin Pan

2005-01-01

32

Boiling Point  

NASA Technical Reports Server (NTRS)

The author recounts his experiences he helped to investigate the accident which destroyed the Space Shuttle Challenger. The focus was on how he used novel approaches to investigate heat transfer in the shuttle's hydrogen tank, after an expert he sought for advice proved unhelpful.

Jansen, Michael C.

2002-01-01

33

Preparation and properties of low boiling point of alcohol and acetone-based magnetic fluid  

NASA Astrophysics Data System (ADS)

Ultra-fine magnetic particles are difficult to be dispersed in low boiling point solvents such as alcohol (C 1-C 4) and acetone. In this paper, we report the preparation methods of several alcohol and acetone-based magnetic fluids. The stability of magnetic fluid depended on the HLB (hydrophile-lipophile balance) of the solvent and alkyl chain lengths of organic layers. The fluid was most stable only when the HLB value of surfactant and the solvents are similar.

Fujita, T.; Miyazaki, T.; Nishiyama, H.; Jeyadevan, B.

1999-07-01

34

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

35

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

36

Generalized syntheses of nanocrystal-graphene hybrids in high-boiling-point organic solvents  

NASA Astrophysics Data System (ADS)

Nanocrystal-graphene have been proposed as a new kind of promising hybrid for a wide range of application areas including catalysts, electronics, sensors, biomedicine, and energy storage, etc. Although a variety of methods have been developed for the preparation of hybrids, a facile and general synthetic approach is still highly required. In this study, nanocrystal-graphene hybrids were successfully synthesized in high-boiling-point organic solvents. Graphene oxide (GO) nanosheets were modified by oleylamine (OLA) to form a OLA-GO complex in order to be readily incorporated into hydrophobic synthesis. A rich library of highly crystalline nanocrystals, with types including noble metal, metal oxide, magnetic material and semiconductor were successfully grown on chemically converted graphene (CCG), which is simultaneously reduced from GO during the synthesis. High boiling-point solvents afford sufficient thermal energy to assure the high-quality crystalline nature of NCs, therefore the post-annealing process is obviated. Controlled experiments revealed that OLA-GO triggers heterogeneous nucleation and serves as excellent nuclei anchorage media. The protocol developed here brings one step closer to achieve ``unity in diversity'' on the preparation of nanocrystal-graphene hybrids.Nanocrystal-graphene have been proposed as a new kind of promising hybrid for a wide range of application areas including catalysts, electronics, sensors, biomedicine, and energy storage, etc. Although a variety of methods have been developed for the preparation of hybrids, a facile and general synthetic approach is still highly required. In this study, nanocrystal-graphene hybrids were successfully synthesized in high-boiling-point organic solvents. Graphene oxide (GO) nanosheets were modified by oleylamine (OLA) to form a OLA-GO complex in order to be readily incorporated into hydrophobic synthesis. A rich library of highly crystalline nanocrystals, with types including noble metal, metal oxide, magnetic material and semiconductor were successfully grown on chemically converted graphene (CCG), which is simultaneously reduced from GO during the synthesis. High boiling-point solvents afford sufficient thermal energy to assure the high-quality crystalline nature of NCs, therefore the post-annealing process is obviated. Controlled experiments revealed that OLA-GO triggers heterogeneous nucleation and serves as excellent nuclei anchorage media. The protocol developed here brings one step closer to achieve ``unity in diversity'' on the preparation of nanocrystal-graphene hybrids. Electronic supplementary information (ESI) available: detail of experimental parameters, AFM, FTIR, XRD, XPS spectra, and other TEM images of GO, CCG and NC-CCG. See DOI: 10.1039/c2nr30915g

Pang, Danny Wei-Ping; Yuan, Fang-Wei; Chang, Yan-Cheng; Li, Guo-An; Tuan, Hsing-Yu

2012-07-01

37

A new procedure for the determination of distillation temperature distribution of high-boiling petroleum products and fractions.  

PubMed

The distribution of distillation temperatures of liquid and semi-fluid products, including petroleum fractions and products, is an important process and practical parameter. It provides information on properties of crude oil and content of particular fractions, classified on the basis of their boiling points, as well as the optimum conditions of atmospheric or vacuum distillation. At present, the distribution of distillation temperatures is often investigated by simulated distillation (SIMDIS) using capillary gas chromatography (CGC) with a short capillary column with polydimethylsiloxane as the stationary phase. This paper presents the results of investigations on the possibility of replacing currently used CGC columns for SIMDIS with a deactivated fused silica capillary tube without any stationary phase. The SIMDIS technique making use of such an empty fused silica column allows a considerable lowering of elution temperature of the analytes, which results in a decrease of the final oven temperature while ensuring a complete separation of the mixture. This eliminates the possibility of decomposition of less thermally stable mixture components and bleeding of the stationary phase which would result in an increase of the detector signal. It also improves the stability of the baseline, which is especially important in the determination of the end point of elution, which is the basis for finding the final temperature of distillation. This is the key parameter for the safety process of hydrocracking, where an excessively high final temperature of distillation of a batch can result in serious damage to an expensive catalyst bed. This paper compares the distribution of distillation temperatures of the fraction from vacuum distillation of petroleum obtained using SIMDIS with that obtained by the proposed procedure. A good agreement between the two procedures was observed. In addition, typical values of elution temperatures of n-paraffin standards obtained by the two procedures were compared. Finally, the agreement between boiling points of polar compounds determined from their retention times and actual boiling points was investigated. PMID:21153592

Boczkaj, Grzegorz; Przyjazny, Andrzej; Kami?ski, Marian

2011-03-01

38

Extraction of giant fullerene molecules, and their subsequent solvation in low boiling point solvents  

NASA Astrophysics Data System (ADS)

Carbon soot produced by the graphite arc-synthesis method was solvated to varying extents in four different solvents, after previous removal of some fullerenes, particularly C 60 and C 70, by toulene extraction. The solvents and weight percentages of soot solvated (in parentheses) are: xylene (3.5), 1,3,5-trimethylbenzene (7.4), 1,2,4-trichlorobenzene (31.1), and 1-methylnaphthalene (22.5). If one accounts for the C 2 n fullerene molecules, primarily C 60 and C 70, extracted from virgin soot by toluene, roughly 37% of the virgin carbon soot can be solvated by the use of 1,2,4-trichlorobenzene. A rough value for the enthalpy of solvation difference is determined for C 70 and C 60, by van't Hoff analysis, to be ?? H = 5 kcal/mol. This method is suggested as a valuable indicator for the difference of enthalpies of binding of C 2 n molecules to the soot matrix. After filtration and removal of the solvents used in the extractions, the residues can be redissolved in low-boiling-point solvents such as methylene chloride and toluene, two solvents which dissolved essentially none of the (previously) toluene-extracted starting material. This underscores the importance of the soot matrix in inhibiting solvation of C 2 n fullerene molecules, and suggests that chromatographic separation of large fullerene molecules can be done with low-boiling-point solvents, and may therefore be feasible.

Smart, C.; Eldridge, B.; Reuter, W.; Zimmerman, J. A.; Creasy, W. R.; Rivera, Nilda; Ruoff, R. S.

1992-01-01

39

Determination of the cross-sectional temperature distribution and boiling limitation of a heat pipe  

NASA Technical Reports Server (NTRS)

A computer model is developed and verified which is capable of determining the cross-sectional temperature distribution within a heat pipe with an attached radiator fin; such heat pipes would be plugged into contact heat exchangers designed to carry heat from a space station habitation module to the radiator elements through a centralized fluid loop. The model can furnish information for determining the susceptibility of the monogroove heat pipe to boiling, as well as the location and magnitude of that boiling.

Peterson, G. P.

1987-01-01

40

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

41

A Useful System for Microscale and Semi-microscale Fractional Distillation of Air-Sensitive Substances with High Boiling Points  

Microsoft Academic Search

A procedure to purify air-sensitive liquids with high boiling points is proposed. Attempts to purify those compounds in a conventional short-path distillation apparatus were unsuccessful. The heat required for the vapors to overcome the relatively large vertical distance before reaching the condenser promotes their decomposition. A horizontal distilling apparatus that avoids extreme refluxing and can efficiently separate the fractions of

J. Alfredo Gutirrez

2001-01-01

42

Temperature and Flow Fluctuations under Local Boiling in a Simulated Fuel Subassembly.  

National Technical Information Service (NTIS)

Out-of-pile experiments were carried out with the sodium test loop SIENA in O-arai Engineering Center of PNC, and the feasibility studies had been made on the local boiling detection by use of temperature and flow fluctuations. The studies showed that the...

H. Inujima T. Ogino M. Uotani K. Yamaguchi

1980-01-01

43

Homochirality beyond grinding: deracemizing chiral crystals by temperature gradient under boiling.  

PubMed

A single-chirality solid phase can be obtained in boiling solutions containing a racemic mixture of left- and right-handed enantiomorphous crystals due to dissolution-crystallization cycles induced by a temperature gradient. This phenomenon provides further insights into asymmetric amplification mechanisms under presumably prebiotic conditions. PMID:22053323

Viedma, Cristbal; Cintas, Pedro

2011-12-28

44

Method of and apparatus for determining deposition-point temperature  

DOEpatents

Acoustic-wave sensor apparatus and method for analyzing a normally liquid petroleum-based composition for monitoring deposition-point temperature. The apparatus includes at least one acoustic-wave device such as SAW, QCM, FPM, TSM or APM type devices in contact with the petroleum-based composition for sensing or detecting the surface temperature at which deposition occurs and/or rate of deposition as a function of temperature by sensing an accompanying change in frequency, phase shift, damping voltage or damping current of an electrical oscillator to a known calibrated condition. The acoustic wave device is actively cooled to monitor the deposition of constituents such as paraffins by determining the point at which solids from the liquid composition begin to form on the acoustic wave device. The acoustic wave device can be heated to melt or boil off the deposits to reset the monitor and the process can be repeated.

Mansure, Arthur J. (Albuquerque, NM); Spates, James J. (Albuquerque, NM); Martin, Stephen J. (Albuquerque, NM)

1998-01-01

45

Chemical characterization and genotoxic potential related to boiling point for fractionally distilled SRC-I coal liquids  

SciTech Connect

This report summarizes selected research efforts oriented toward ameliorating the genotoxic potential of direct coal liquefaction materials through modification or optimization of process conditions. The studies described were conducted to evaluate the utility of optimized distillation for coal liquids from the SRC-I process. SRC-I process solvent was distilled into 50/sup 0/F-range boiling point (bp) cuts. Analysis of amino-PAH (APAH) showed that mutagenic APAHs containing 3 or more rings were found primarily in fractions boiling above 750/sup 0/F. Three microbial tester strains were used to screen for genetically active agents in the SRC-I distillate bp cuts. Reverse mutation with the Ames tester strain TA98 demonstrated that mutagens were concentrated in the bp cuts boiling above 700/sup 0/F. For this tester strain most of the genetic activity in these distillates was attributable to chemical fractions enriched in APAH having 3 or more rings. Mutagenicity data obtained with TA98 was in good agreement with sk in carcinogenesis results from the mouse-skin initiation/promotion (in vivo) test system. The strongest response in the forward mutation assay did not occur in the most carcinogenically active fractions. Results of initiation/promotion experiments used to measure the relative potency of bp cuts as initiators of mouse skin carcinogenesis again showed that fractions boiling above 750/sup 0/F. Compounds reaching their highest concentrations in the highest boiling and most carcinogenically active cut included known carcinogens such as benzo(a)pyrene and dimethyl benzanthracene. Thus, all biomedical test results indicate that consideration should be given to conducting distillation so as to minimize, in the distillate product, the concentrations of those biologically active compounds found in cuts boiling above 700/sup 0/C.

Wilson, B.W.; Pelroy, R.A.; Mahlum, D.D.

1982-07-01

46

Smoothing strategies for surface temperatures measured during vigorous transient boiling  

Microsoft Academic Search

A vertically oriented hollow nickel cylinder (0.15-m dia, 0.3-m height, 0.095-m wall thickness) has been quenched in cold (22 °C) water from an initial temperature of 810°C. During the quench, the output from surface-mounted intrinsic thermocouples was digitized and recorded at intervals of 0.004 s over a test period of 40 s. The output from one of these thermocouples is

J. E. Park; W. Chu; G. M. Ludtka

1990-01-01

47

XC. The influence of zero-point energy on the thermodynamic properties of the low boiling point elements  

Microsoft Academic Search

The internal energy and molar volume at absolute zero and the characteristic temperature of the inert gas solids, together with solid hydrogen and deuterium, are calculated taking account of zero-point energy. It is found that to a good approximation a law of corresponding states is valid and the consequences of this are discussed.

J. S. Dugdale; D. K. C. MacDonald

1954-01-01

48

Circumferential temperature distribution during nucleate pool boiling outside smooth and modified horizontal tubes  

SciTech Connect

In the work an approach to avoid a circumferential temperature distribution existing during nucleate pool boiling on a horizontal cylinder within low heat flux densities is presented. The idea of the approach is local heat transfer enhancement by a porous layer application on a part of the heating surface. An experiment on nucleate pool boiling heat transfer from horizontal cylinders to saturated R141b and water under atmospheric pressure is reported. Experiments have been conducted using stainless steel tubes with the outside diameter between 8 mm and 23 mm with the active length of 250 mm. The outside surface of the tubes was smooth or partially coated with a porous metallic layer. In particular, measurements of inside circumferential temperature distribution have been performed. (author)

Dominiczak, Przemyslaw R.; Cieslinski, Janusz T. [Gdansk University of Technology, Faculty of Mechanical Engineering, Narutowicza 11/12, 80-952 Gdansk (Poland)

2008-10-15

49

Oxidation kinetics of micron-sized aluminum powder in high-temperature boiling water  

Microsoft Academic Search

A new efficient method of hydrogen, heat and aluminum oxide\\/hydroxide co-production is proposed. Only micron-sized aluminum powder (without any chemical activation) and usual water are used as initial reagents. For aluminum to be effectively oxidized, water is converted into the high-temperature boiling state that creates high pressure inside oxidation reactor. Paper describes the oxidation kinetics of aluminum micron powder in

M. S. Vlaskin; E. I. Shkolnikov; A. V. Bersh

2011-01-01

50

Phase Separation, Density Fluctuations, and Boiling Near the Liquid-Gas Critical Point  

NASA Astrophysics Data System (ADS)

A pure liquid-gas mixture is one of the simplest examples of a soft-matter system. In fact, when co-existing gas and liquid phases of pure fluid are heated to their critical point, large-scale density fluctuations make the fluid extremely compressible (to external forces), expandable (to heating), slows the diffusive transport, and decreases the surface tension. In principle these properties and others either diverge to infinity or converge to zero at the critical temperature. These properties lead to some very unusual behavior: large density gradients at the laboratory scale, a large mechanical response to heating, and perfect wetting of a solid wall by the liquid phase (zero contact-angle). We have further simplified this system by performing experiments in weightlessness (Mir spaces station). By controlling the fluid's temperature, these properties may be varied over large ranges in a single sample. When the fluid is driven out of equilibrium by a fast temperature quench from the single-phase (supercritical fluid) state into the two-phase state, we have observed universal growth laws of minority domains (gas bubbles) during phase separation. Prior to this quench we have also observed density fluctuations using optical microscopy near the critical point. When heat is applied to a liquid-gas mixture, we have observed a spectacular spreading of a gas bubble along a hot solid wall as well as gas bubble over-heating (where the interior of a gas bubble gains a higher temperature than the heating wall). Although this gas phase over-heating appears to violate the second law, it is really a transient our-of-equilibrium effect. Inside of these unusual bubbles we also have observed unusually large variations in liquid wetting film thickness that often appear to evolve into spreading contact lines on the sapphire wall when heat is applied. We have observed coarsening and growth of minority domains (gas bubbles) in SF6 near its liquid-gas critical point. Phase separation in our constant density samples was induced in our constant volume cells by temperature quenches in weightless conditions (Mir station), while visualizing density fluctuations and domain growth using optical microscopy. The optics of the formation of the density fluctuation images will be discussed. The well-known statistics of the density fluctuations provide natural space and time scales for domain growth. Previous experiments have documented two morphologies and two associated growth laws with a sharp transition between the two. This transition appears to be controlled by the minority volume fraction. While the slow, t 1/3 growth, for disconnected morphologies, is understood as a diffusion process, the fast growth, t1 growth, for connected domains, is less well-understood. We will discuss several shallow quenching sequences at the critical density (+/-0.02%) and slightly off-critical where we have observed fast linear growth.

Hegseth, John; Oprisan, Ana; Roy, Arun; Nikolayev, Vadim; Beysens, Daniel; Garrabos, Yves; Lecoutre-Chabot, Carole

2002-11-01

51

Remote temperature-set-point controller  

DOEpatents

An instrument for carrying out mechanical strain tests on metallic samples with the addition of an electrical system for varying the temperature with strain, the instrument including opposing arms and associated equipment for holding a sample and varying the mechanical strain on the sample through a plurality of cycles of increasing and decreasing strain within predetermined limits, circuitry for producing an output signal representative of the strain during the tests, apparatus including a set point and a coil about the sample for providing a controlled temperature in the sample, and circuitry interconnected between the strain output signal and set point for varying the temperature of the sample linearly with strain during the tests.

Burke, William F. (Crest Hill, IL); Winiecki, Alan L. (Downers Grove, IL)

1986-01-01

52

Boiling temperature as a scaling parameter for the microscopic relaxation dynamics in molecular liquids.  

PubMed

At sufficiently high temperatures, the center-of-mass microscopic diffusion dynamics of liquids is characterized by a single component, often with weak temperature dependence. In this regime, the effective cage made by the neighbor particles cannot be sustained and readily breaks down, enabling long-range diffusion. As the temperature is decreased, the cage relaxation becomes impeded, leading to a higher viscosity with more pronounced temperature dependence. On the microscopic scale, the sustained caging effect leads to a separation between a faster in-cage relaxation component and a slower cage-breaking relaxation component. The evidence for the separate dynamic components, as opposed to a single stretched component, is provided by quasielastic neutron scattering experiments. We use a simple method to evaluate the extent of the dynamic components separation as a function of temperature in a group of related aromatic molecular liquids. We find that, regardless of the glass-forming capabilities or lack thereof, progressively more pronounced separation between the in-cage and cage-breaking dynamic components develops on cooling down as the ratio of T(b)/T, where T(b) is the boiling temperature, increases. This reflects the microscopic mechanism behind the empirical rule for the glass forming capability based on the ratio of boiling and melting temperatures, T(b)/T(m). When a liquid's T(b)/T(m) happens to be high, the liquid can readily be supercooled below its T(m) because the liquid's microscopic relaxation dynamics is already impeded at T(m), as evidenced by a sustained caging effect manifested through the separation of the in-cage and cage-breaking dynamic components. Our findings suggest certain universality in the temperature dependence of the microscopic diffusion dynamics in molecular liquids, regardless of their glass-forming capabilities. Unless the insufficiently low (with respect to T(b)) melting temperature, T(m), intervenes and makes crystallization thermodynamically favorable when cage-breaking is still unimpeded and the structural relaxation is fast, the liquid is likely to become supercooled. The propensity to supercooling and eventually forming a glass is thus determined by a purely thermodynamic factor, T(b)/T(m). PMID:23869489

Mamontov, Eugene

2013-08-15

53

Measurement of thermodynamic temperature of high temperature fixed points  

SciTech Connect

The paper is devoted to VNIIOFI's measurements of thermodynamic temperature of the high temperature fixed points Co-C, Pt-C and Re-C within the scope of the international project coordinated by the Consultative Committee for Thermometry working group 5 'Radiation Thermometry'. The melting temperatures of the fixed points were measured by a radiance mode radiation thermometer calibrated against a filter radiometer with known irradiance spectral responsivity via a high temperature black body. This paper describes the facility used for the measurements, the results and estimated uncertainties.

Gavrilov, V. R.; Khlevnoy, B. B.; Otryaskin, D. A.; Grigorieva, I. A.; Samoylov, M. L.; Sapritsky, V. I. [All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI), 46 Ozernaya St., Moscow 119361 (Russian Federation)] [All-Russian Research Institute for Optical and Physical Measurements (VNIIOFI), 46 Ozernaya St., Moscow 119361 (Russian Federation)

2013-09-11

54

Determination of the Latent Heats and Triple Point of Perfluorocyclobutane  

ERIC Educational Resources Information Center

Proposes the use of Perfluorocyclobutane in physical chemistry courses to conduct experiments on latent heat, triple point temperatures and pressures, boiling points, and entropy of vaporization. (SL)

Briggs, A. G.; Strachan, A. N.

1977-01-01

55

Sediment microbial communities in Great Boiling Spring are controlled by temperature and distinct from water communities  

PubMed Central

Great Boiling Spring is a large, circumneutral, geothermal spring in the US Great Basin. Twelve samples were collected from water and four different sediment sites on four different dates. Microbial community composition and diversity were assessed by PCR amplification of a portion of the small subunit rRNA gene using a universal primer set followed by pyrosequencing of the V8 region. Analysis of 164?178 quality-filtered pyrotags clearly distinguished sediment and water microbial communities. Water communities were extremely uneven and dominated by the bacterium Thermocrinis. Sediment microbial communities grouped according to temperature and sampling location, with a strong, negative, linear relationship between temperature and richness at all taxonomic levels. Two sediment locations, Site A (8780?C) and Site B (79?C), were predominantly composed of single phylotypes of the bacterial lineage GAL35 (p?=36.1%), Aeropyrum (p?=16.6%), the archaeal lineage pSL4 (p?=15.9%), the archaeal lineage NAG1 (p?=10.6%) and Thermocrinis (p?=7.6%). The ammonia-oxidizing archaeon Candidatus Nitrosocaldus' was relatively abundant in all sediment samples <82?C (p?=9.51%), delineating the upper temperature limit for chemolithotrophic ammonia oxidation in this spring. This study underscores the distinctness of water and sediment communities in GBS and the importance of temperature in driving microbial diversity, composition and, ultimately, the functioning of biogeochemical cycles.

Cole, Jessica K; Peacock, Joseph P; Dodsworth, Jeremy A; Williams, Amanda J; Thompson, Daniel B; Dong, Hailiang; Wu, Geng; Hedlund, Brian P

2013-01-01

56

Time and Space Resolved Wall Temperature Measurements during Nucleate Boiling with Constant Heat Flux Boundary Conditions  

NASA Technical Reports Server (NTRS)

The lack of temporally and spatially resolved measurements under nucleate bubbles has complicated efforts to fully explain pool-boiling phenomena. The objective of this current work is to acquire time and space resolved temperature distributions under nucleate bubbles on a constant heat flux surface. This was performed using a microheater array with 100 micron resolution that allowed effectively simultaneous measurements of surface temperature while supplying a constant dissipative heat flux. This data is then correlated with high speed (> 1000Hz) visual recordings of the bubble growth and departure from the heater surface acquired from below and from the side of the heater. The data indicate that a significant source of energy during bubble nucleation and initial growth is the superheated layer around the bubble. Bubble coalescence was not observed to decrease surface temperature as significantly as bubble departure from the surface. Since bubble departure is typically followed by a sharp increase in the heater surface temperature, it is surmised that the departing bubble effectively removes the superheated layer, allowing a high local heat transfer rate with the bulk fluid through transient conduction/micro-convection during rewetting.

Myers, Jerry G.; Hussey, Sam W.; Yee, Glenda F.; Yerramilli, Vamsee K.; Kim, Jungho

2005-01-01

57

Determining factors for anodic polarization curves of typical structural materials of boiling water reactors in high temperature high purity water  

Microsoft Academic Search

In order to examine the anodic polarization characteristics of typical structural materials of boiling water reactors (BWRs), the anodic polarization curves of type 316L stainless steel (316L SS) and Alloy 182 were measured in deaerated high purity water at 553K using the previously reported measurement method which was confirmed suitable for high temperature high purity water. In order to

Masahiko Tachibana; Kazushige Ishida; Yoichi Wada; Ryosuke Shimizu; Nobuyuki Ota; Nobuyoshi Hara

2012-01-01

58

Remote temperature-set-point controller  

DOEpatents

An instrument is described for carrying out mechanical strain tests on metallic samples with the addition of means for varying the temperature with strain. The instrument includes opposing arms and associated equipment for holding a sample and varying the mechanical strain on the sample through a plurality of cycles of increasing and decreasing strain within predetermined limits, circuitry for producing an output signal representative of the strain during the tests, apparatus including a a set point and a coil about the sample for providing a controlled temperature in the sample, and circuitry interconnected between the strain output signal and set point for varying the temperature of the sample linearly with strain during the tests.

Burke, W.F.; Winiecki, A.L.

1984-10-17

59

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

60

Assigning thermodynamic temperatures to high-temperature fixed-points  

NASA Astrophysics Data System (ADS)

Workpackage five of the High Temperature Fixed-Point research programme will determine the thermodynamic temperature for the equilibrium melting transition of the pure eutectic systems of Re-C, Pt-C and Co-C and, in addition, the freezing point of Cu. Measurements of four different cells of each type will be made by nine participating laboratories. This paper describes how the melt sensitivity to the rate of the previous freeze, furnace effects and cell impurities will be accounted for and how the results will be combined allowing for all existing correlations.

Woolliams, E. R.; Bloembergen, P.; Machin, G.

2013-09-01

61

Flow boiling heat transfer coefficients at cryogenic temperatures for multi-component refrigerant mixtures of nitrogen-hydrocarbons  

NASA Astrophysics Data System (ADS)

The recuperative heat exchanger governs the overall performance of the mixed refrigerant Joule-Thomson cryocooler. In these heat exchangers, the non-azeotropic refrigerant mixture of nitrogen-hydrocarbons undergoes boiling and condensation simultaneously at cryogenic temperature. Hence, the design of such heat exchanger is crucial. However, due to lack of empirical correlations to predict two-phase heat transfer coefficients of multi-component mixtures at low temperature, the design of such heat exchanger is difficult.

Ardhapurkar, P. M.; Sridharan, Arunkumar; Atrey, M. D.

2014-01-01

62

Phase Separation, Density Fluctuations, and Boiling Near the Liquid-Gas Critical Point  

Microsoft Academic Search

A pure liquid-gas mixture is one of the simplest examples of a soft-matter system. In fact, when co-existing gas and liquid phases of pure fluid are heated to their critical point, large-scale density fluctuations make the fluid extremely compressible (to external forces), expandable (to heating), slows the diffusive transport, and decreases the surface tension. In principle these properties and others

John Hegseth; Ana Oprisan; Arun Roy; Vadim Nikolayev; Daniel Beysens; Yves Garrabos; Carole Lecoutre-Chabot

2002-01-01

63

Spatial and temporal variation of the surface temperature and heat flux for saturated pool nucleate boiling at lower heat fluxes  

SciTech Connect

The spatial and temporal variations of local surface temperature and heat flux for saturated pool nucleate boiling are investigated parametrically using a numerical model. The numerical model consisted of solving the three-dimensional transient heat conduction equation within the heater subjected to nucleate boiling over its upper surface. The surface topography model to distribute the cavities over the boiling surface used a Monte Carlo scheme. All cavities were assumed to be conical in shape. The cavity radii are obtained using an exponential probability density function with a known mean value. Local surface temperatures showed significant spatial and temporal variations, depending upon the surface topography and the heater material and thickness. However, the surface-averaged temperature showed practically no temporal variation. The temporal variations in local temperatures caused the surface-averaged heat flux to vary significantly. The temporal variations in the surface-averaged heat flux were similar for smooth and rough and thick and thin copper and nickel plates. Results indicated that the use of a classical energy balance equation to evaluate the surface heat flux must consider the spatial variation of the temperature. Results also showed that any thermocouple embedded beneath the surface of the heater does not follow the temporal variations at the surface.

Unal, C.; Pasamehmetoglu, K.O.

1993-10-01

64

Determination of boiling point of petrochemicals by gas chromatography-mass spectrometry and multivariate regression analysis of structural activity relationship.  

PubMed

Accurate understanding of analyte boiling points (BP) is of critical importance in gas chromatographic (GC) separation and crude oil refinery operation in petrochemical industries. This study reported the first combined use of GC separation and partial-least-square (PLS1) multivariate regression analysis of petrochemical structural activity relationship (SAR) for accurate BP determination of two commercially available (D3710 and MA VHP) calibration gas mix samples. The results of the BP determination using PLS1 multivariate regression were further compared with the results of traditional simulated distillation method of BP determination. The developed PLS1 regression was able to correctly predict analytes BP in D3710 and MA VHP calibration gas mix samples, with a root-mean-square-%-relative-error (RMS%RE) of 6.4%, and 10.8% respectively. In contrast, the overall RMS%RE of 32.9% and 40.4%, respectively obtained for BP determination in D3710 and MA VHP using a traditional simulated distillation method were approximately four times larger than the corresponding RMS%RE of BP prediction using MRA, demonstrating the better predictive ability of MRA. The reported method is rapid, robust, and promising, and can be potentially used routinely for fast analysis, pattern recognition, and analyte BP determination in petrochemical industries. PMID:24881546

Fakayode, Sayo O; Mitchell, Breanna S; Pollard, David A

2014-08-01

65

Highly efficient secondary dewatering of dewatered sewage sludge using low boiling point solvents.  

PubMed

Secondary dewatering of dewatered sludge is imperative to make conventional drying and incineration of sludge more economically feasible. In this study, a secondary dewatering of dewatered sludge with selected solvents (i.e. acetone and ethanol) followed by vacuum filtration and nature drying was investigated to achieve in-depth dewatering. After the entire secondary dewatering process, the sludge was shown to be odourless and the organic matter content was greatly retained. Increased mean particle size of sludge after solvent contact improved solid-liquid separation. With an acetone/sludge ratio of 3:1 (mL:g) in solvent contact and subsequent nature drying at ambient temperature after 24 h, the moisture content of sludge can be reduced to a level less than 20%. It is found that the polysaccharides were mainly precipitated by acetone, whereas the release ratios of protein and DNA were increased significantly as the added acetone volumes were elevated. During nature drying, accumulated evaporation rates of the sludge after solvent contact were 5-6 times higher than original dewatered sludge. Furthermore, sludge after acetone contact had better nature drying performance than ethanol. The two-stage dewatering involves solvent contact dewatering and solvent enhanced evaporation dewatering. Through selecting an appropriate solvent/sludge ratio as well as economical solvents and minimizing the solvent loss in a closed-pilot system, this dewatering process can be competitive in industrial applications. Therefore, this solvent-aided secondary dewatering is an energy-saving technology for effective in-depth dewatering of dewatered sludge and subsequent sludge utilization. PMID:24600846

He, Chao; Chena, Chia-Lung; Xu, Zhirong; Wang, Jing-Yuan

2014-01-01

66

Preparation of indium-tin oxide (ITO) nano-aciculae by a simple precipitation near boiling point and post-calcination method  

Microsoft Academic Search

ITO nano-aciculae (needle-like nanometer crystals) were prepared by post-calcination of ITO precursor nano-aciculae, which were synthesized by a simple precipitation near boiling point method. Transparent conductive film formed of ITO nano-aciculae was prepared by a simple coating process. ITO precursor nano-aciculae, ITO nano-aciculae and films were characterized with morphology, phase structure, optical and electrical properties, etc. The cross-sectional diameters of

Shu-Guang Chen; Chen-Hui Li; Wei-Hao Xiong; Lang-Ming Liu; Hui Wang

2005-01-01

67

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

68

Low Temperature Regenerators for Zero Boil-Off Liquid Hydrogen Pulse Tube Cryocoolers.  

National Technical Information Service (NTIS)

Recently, a great deal of attention has been focused on zero boil-off (ZBO) propellant storage as a means of minimizing the launch mass required for long-term exploration missions. A key component of ZBO systems is the cooler. Pulse tube coolers offer the...

L. J. Salerno A. Kashani B. Helvensteijn P. Kittel

2002-01-01

69

Influence of Quenchant Hydrodynamics and Boiling Phase Incipient Temperature Shifts on Residual Stress Formation  

Microsoft Academic Search

Quench heat treatments are used in metallurgical applications to alter material mechanical properties such as hardness and strength. Although these conventional heat treatments have been used for many decades, specific influences of material properties and heat transfer conditions during quenching are not very well understood. In particular, predictions based on steady-state boiling heat transfer coefficients disagree with observations, leading to

Willem J. J. Vorster; Morne W. Van Der Watt; Andrew M. Venter; Edward C. Oliver; D. G. Leo Prakash; Alexander M. Korsunsky

2009-01-01

70

Microscale measurement of wall-temperature distribution at a single vapor bubble for evaluation of a nucleate boiling model  

NASA Astrophysics Data System (ADS)

An experiment is designed for evaluation of an existing nucleate boiling model. An essential aspect of the model is the description of heat and mass transfer in a tiny thin film area where the vapor bubble is attached to the wall. A considerable amount of the total heat transferred from the heater flows through this ``micro region.'' The high local heat flux in the micro region leads to a local cooling. The associated wall temperature drop underneath this area is calculated with the nucleate boiling model and measured with an optical method using thermochromic liquid crystals (TLC). In the first ground experiment a thin liquid film evaporator was built with a thin electrically heated wall featuring two-dimensional, high-resolution temperature measurement by TLCs. The measured temperature distribution corresponds to the calculated one. The second experimental setup for l-g and reduced gravity conditions is designed to establish a stationary bubble of appropriate size to enable optical observation of the circular temperature drop. A qualitative evaluation of the model seems to be possible with this experiment. .

Stephan, Peter; Hhmann, Christoph; Kern, Jrgen

2002-01-01

71

Numerical modelling of temperature fields in the flow boiling liquid through a vertical minichannel with an enhanced heating surface  

NASA Astrophysics Data System (ADS)

The paper presents results of heat transfer research on flow boiling in a rectangular minichannel positioned vertically, with an enhanced surface. One of the channel walls was made of thin foil powered by direct current. This foil is enhanced on the side contacting fluid in the minichannel. It is possible to observe both surfaces of the minichannel through two openings covered with glass panes. One allows detecting temperature of the plain side of the foil by liquid crystal thermography. The opposite surface of the minichannel (from the enhanced side of the foil) can be observed through the other glass pane. The observations of the flow structures allowed to calculate the void fraction for some cross-sections of selected two phase flow images. In mathematical modelling of the considered process stationary heat transfer in a glass pane, heating foil and boiling liquid can be described with Laplace equation, Poisson equation and energy equation, respectively. For completeness of the model a corresponding system of boundary conditions was given. The two-dimensional temperature fields of glass pane, heating foil and fluid was computed with the Trefftz method. The equalizing calculus used to smooth the measured data has reduced errors.

Ho?ejowska, Sylwia; Piasecka, Magdalena

2014-03-01

72

A novel refrigerator attaining temperature below ? point  

NASA Astrophysics Data System (ADS)

The present study proposes a novel refrigerator in theory, which uses 4He as working fluid to directly reach 2.3 K and uses a small amount of 3He to attain the temperature below 1.7 K. The compact and highly efficient new refrigerator works with the Vuilleumier cycle. The novel refrigerator is driven by a thermal compressor which creatively uses mix-refrigerants J-T refrigerator alternative to liquid nitrogen as the power source. Furthermore, the Vuilleumier cycle can be used to achieve temperature below liquid helium with the improvement of the ultra-low temperature regenerator material. A new method of reaching the temperature below 1.7 K is proposed on the regenerative refrigerator, which could be an important breakthrough for the cryogenic science and technology.

Zhou, Yuan; Xue, XiaoDai; Wang, JunJie; Gu, Chao

2012-08-01

73

Estimation of reference or balance point temperatures  

Microsoft Academic Search

For many years the enrgy performance of buildings has been estimated by using regression techniques involving energy use and heating degree day data. Recently, some techniques have emerged that use variable-base heating degree day data to more closely characterize the energy performance of buildings. The base temperature used to calculate heating degree days is varied to match the reference or

J. M. MacDonald; L. Jung; J. A. Tevepaugh

1985-01-01

74

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

75

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

76

Pyrosequencing reveals high-temperature cellulolytic microbial consortia in Great Boiling Spring after in situ lignocellulose enrichment.  

PubMed

To characterize high-temperature cellulolytic microbial communities, two lignocellulosic substrates, ammonia fiber-explosion-treated corn stover and aspen shavings, were incubated at average temperatures of 77 and 85C in the sediment and water column of Great Boiling Spring, Nevada. Comparison of 109,941 quality-filtered 16S rRNA gene pyrosequences (pyrotags) from eight enrichments to 37,057 quality-filtered pyrotags from corresponding natural samples revealed distinct enriched communities dominated by phylotypes related to cellulolytic and hemicellulolytic Thermotoga and Dictyoglomus, cellulolytic and sugar-fermenting Desulfurococcales, and sugar-fermenting and hydrogenotrophic Archaeoglobales. Minor enriched populations included close relatives of hydrogenotrophic Thermodesulfobacteria, the candidate bacterial phylum OP9, and candidate archaeal groups C2 and DHVE3. Enrichment temperature was the major factor influencing community composition, with a negative correlation between temperature and richness, followed by lignocellulosic substrate composition. This study establishes the importance of these groups in the natural degradation of lignocellulose at high temperatures and suggests that a substantial portion of the diversity of thermophiles contributing to consortial cellulolysis may be contained within lineages that have representatives in pure culture. PMID:23555835

Peacock, Joseph P; Cole, Jessica K; Murugapiran, Senthil K; Dodsworth, Jeremy A; Fisher, Jenny C; Moser, Duane P; Hedlund, Brian P

2013-01-01

77

Pyrosequencing Reveals High-Temperature Cellulolytic Microbial Consortia in Great Boiling Spring after In Situ Lignocellulose Enrichment  

PubMed Central

To characterize high-temperature cellulolytic microbial communities, two lignocellulosic substrates, ammonia fiber-explosion-treated corn stover and aspen shavings, were incubated at average temperatures of 77 and 85C in the sediment and water column of Great Boiling Spring, Nevada. Comparison of 109,941 quality-filtered 16S rRNA gene pyrosequences (pyrotags) from eight enrichments to 37,057 quality-filtered pyrotags from corresponding natural samples revealed distinct enriched communities dominated by phylotypes related to cellulolytic and hemicellulolytic Thermotoga and Dictyoglomus, cellulolytic and sugar-fermenting Desulfurococcales, and sugar-fermenting and hydrogenotrophic Archaeoglobales. Minor enriched populations included close relatives of hydrogenotrophic Thermodesulfobacteria, the candidate bacterial phylum OP9, and candidate archaeal groups C2 and DHVE3. Enrichment temperature was the major factor influencing community composition, with a negative correlation between temperature and richness, followed by lignocellulosic substrate composition. This study establishes the importance of these groups in the natural degradation of lignocellulose at high temperatures and suggests that a substantial portion of the diversity of thermophiles contributing to consortial cellulolysis may be contained within lineages that have representatives in pure culture.

Peacock, Joseph P.; Cole, Jessica K.; Murugapiran, Senthil K.; Dodsworth, Jeremy A.; Fisher, Jenny C.; Moser, Duane P.; Hedlund, Brian P.

2013-01-01

78

Ensemble Artificial Neural Networks for Prediction of Dew Point temperature  

Microsoft Academic Search

Dew point temperature is needed as an input to calculate various meteorological variables. In general, it contributes to human and animal comfort levels. The goal of this study was to develop artificial neural network (ANN) models for dew point temperature prediction to improve upon previous research. These improvements included optimizing the stopping criteria, comparing seasonal models to year-round models, and

D. B. Shank; Ronald W. Mcclendon; J. Paz; Gerrit Hoogenboom

2008-01-01

79

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

80

Experimental boiling heat transfer coefficients in the high temperature generator of a double effect absorption machine for the lithium bromide\\/water mixture  

Microsoft Academic Search

The aim of this work is to determine the boiling heat transfer coefficients in the high temperature desorber (HTD) of an air-cooled double effect lithium bromide\\/water absorption prototype. The HTD is a plate heat exchanger (PHE) with thermal oil on one side, and a lithium bromide solution on the other side. Several experiments were performed with this PHE while the

J. D. Marcos; M. Izquierdo; R. Lizarte; E. Palacios; C. A. Infante Ferreira

2009-01-01

81

Key role of temperature in ferromagnetic Bloch point simulations  

NASA Astrophysics Data System (ADS)

Bloch points in permalloy cylinders are investigated using a micromagnetic framework, where thermal effects are included via the Landau-Lifshitz-Bloch equation of motion. We show that this enables micromagnetic modeling of a Bloch point avoiding the problem of singularities, which have been reported in the literature so far. The details of the Bloch point which we reveal are compared with earlier analytic approximations describing its geometry and the magnetization drop in its center. The temperature dependence of characteristic parameters, like the Bloch point radius or the azimuthal inflow angle is given in the full temperature range.

Lebecki, K. M.; Hinzke, D.; Nowak, U.; Chubykalo-Fesenko, O.

2012-09-01

82

Non-invasive measurement of void fraction and liquid temperature in microchannel flow boiling  

NASA Astrophysics Data System (ADS)

Past thermometry research for two-phase microfluidic systems made much progress regarding wall temperature distributions, yet the direct measurement of fluid temperature has received little attention. This paper uses a non-invasive two-dye/two-color fluorescent technique to capture fluid temperature along with local liquid fraction in a two-phase microflow generated by injecting air into a heated microchannel. The fluorescent emission of Rhodamine 110 and Rhodamine B, measured with photodiodes, is used to obtain local liquid temperature (3C) and void fraction (2% full-scale) over a temperature range from 45 to 100C. Arrays of these sensors can significantly expand the set of measurable flow parameters to include bubble/slug frequency, size, velocity, and growth rates in addition to mapping the local liquid temperature and void fraction.

Fogg, David; David, Milnes; Goodson, Kenneth

2009-04-01

83

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

84

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

85

The use of linear expressions of solute boiling point versus retention to indicate special interactions with the molecular rings of modified cyclodextrin phases in gas chromatography  

PubMed

The boiling points (degrees C, 1 x 10) of diverse C10 polar solutes from volatile oils are set against their relative retention times versus n-undecane to calculate linear equations for 12 commercial modified cyclodextrin (CD) capillary phases. Ten data points are considered for each CD, then solutes are rejected until 5 or more remain that give an expression with a correlation coefficient of at least 0.990 and a standard deviation of less than 5.5. Three phases give almost perfect correlation, and 3 other CDs have difficulty complying. Solutes involved in the equations (most frequently cuminal, linalol, and carvone) are presumed to have a 'standard' polar transient interaction with the molecular rings of the CDs concerned. Several remaining solutes (mostly citral, fenchone, and menthol) exhibit extra retention over the calculated standard (up to 772%), which is believed to indicate a firm 'host' CD or 'guest' solute molecular fit in some cases. Other solutes show less retention than calculated (mostly citronellal, citronellol, estragole, and pulegone). This suggests rejection by the CD, which behaves merely as a conventional stationary phase to them. The intercept constant in the equation for each phase is suggested to be a numerical relative polarity indicator. These b values indicate that 3 hydroxypropyl CDs show the most polarity with values from 28 to 43; and CDs that are fully substituted with inert groups fall in the range of 15 to 20. PMID:10955511

Betts

2000-08-01

86

Estimating surface temperature in forced convection nucleate boiling: A simplified method  

NASA Technical Reports Server (NTRS)

During a test program to investigate low-cycle thermal fatigue, 21 of 22 cylindrical test sections of a cylindrical rocket thrust chamber were thermally cycled to failure. Cylinder liners were fabricated from OFHC copper, Amzirc, and NARloy-Z. The cylinders were fabricated by milling cooling channels into the liner and closing out the backside with electrodeposited copper. The tests were conducted at a chamber pressure of 4.14 MN/sq m (600 psia) and an oxidant-fuel ratio of 6.0 using hydrogen-oxygen as propellants. The average throat heat flux was 54 MW/sq m (33 Btu/sq in./sec). All of the failures were characterized by a thinning of the cooling channel wall and eventual failure by tensile rupture. The 1/2-hard Amzirc material showed little improvement in cyclic life when compared with OFHC copper; while the NARloy-Z and aged Amzirc materials had the best cyclic life characteristics. One OFHC copper cylinder was thermall cycled 2044 times at a steady-state hot-gas-side wall temperature of 514 K (925 R) without failing.

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

1977-01-01

87

Upconversion photoluminescence of ZrO 2:Er 3+ nanocrystals synthesized by using butadinol as high boiling point solvent  

NASA Astrophysics Data System (ADS)

Erbium doped ZrO 2 (ZrO 2:Er 3+) nanocrystals are prepared by a butadinol low thermal crystallization method. The crystallization temperature is reduced to 500 C. X-ray diffraction (XRD) spectra show there exists monoclinic and cubic ZrO 2 phases. Green, yellow and red lights are seen from the upconverting luminescence spectra under 980 nm excitation. The results confirm that upconverting emission is due to excited-state absorption (ESA) and energy transfer upconverting (ETU) process.

Jia, Ruokun; Yang, Wensheng; Bai, Yubai; Li, Tiejin

2006-02-01

88

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

89

Radiance Temperature of Tantalum at Its Melting Point.  

National Technical Information Service (NTIS)

Radiance temperature (at two wavelengths, 653 and 995 nm) of tantalum at its melting point was measured with the use of a subsecond-duration pulse heating technique. Specimens in the form of strips with initially different surface roughnesses were used. T...

A. Cezairliyan J. L. McClure L. Coslovi F. Righini A. Rosso

1976-01-01

90

ENERGY CONSERVATION THROUGH POINT SOURCE RECYCLE WITH HIGH TEMPERATURE HYPERFILTRATION  

EPA Science Inventory

The report gives results of a study of energy conservation effects of point source recycle with high-temperature hyperfiltration (HF) in the textile industry. (HF and ultrafiltration (UF) are pressure-driven membrane processes which have potential for recycle of water, energy, an...

91

Carbon dioxide and R410A flow boiling heat transfer, pressure drop, and flow pattern in horizontal tubes at low temperatures  

NASA Astrophysics Data System (ADS)

Carbon dioxide (CO2) has been seriously considered as an alternate refrigerant for HCFC and HFC fluids, due to the increasing interest of environmentally safe refrigerants in air-conditioning and refrigeration systems. In this study, CO2 flow boiling heat transfer coefficients and pressure drop are measured in macro-scale (6.1 and 3.5 mm) tubes at evaporation temperatures of -15 and -30C. The measured results show that the nucleate boiling is a main heat transfer mechanism in the 6.1 mm tube and the contribution of convective boiling becomes greater with the decrease of tube diameters and the increase of mass fluxes. The surface roughness of the 6.1 and 3.5 mm tube are presented by SEM and AFM images and surface profiles, and it is shown that the rougher surface of the 6.1 mm tube can affect the flow boiling heat transfer. The CO2 heat transfer coefficients and pressure drop are measured in a mini-scale (0.89 mm) multi-ported tube at the evaporation temperature of -30C. Also, R410A and R22 flow boiling heat transfer coefficients and pressure drop in a macro-scale (6.1 mm) tube were measured, and they are compared with CO2. This comparison presents that the CO2 flow boiling heat transfer coefficients are higher than R410A and R22 at low vapor qualities, and CO2 pressure drop is significantly lower than R410A and R22. This advantageous characteristic for CO2 could be explained by properties such as surface tension, reduced pressure, and the density ratio of liquid to vapor. The prediction of heat transfer coefficients and pressure drop was performed by general correlations and the calculation results are compared with measured values. Two-phase flow patterns were visualized for CO2 and R410A in the 6 and 3 mm glass tubes, and they are compared with the Weisman et al. and the Wojtan et al. flow pattern maps. The flow pattern maps can determine the flow patterns relatively well, except the transition from intermittent to annular flow.

Park, Chang Yong

92

Twelve years of high temperature fixed point research: A review  

NASA Astrophysics Data System (ADS)

A review of research into high temperature fixed points (HTFPs), since their inception at NMIJ in 1999 until 2011 is given. HTFPs discussed in this paper are those whose transition temperatures are above the freezing point of copper and based on eutectic/peritectic alloys. The paper will begin with an historical overview; including a description of the different types of modern HTFPs. The evolution of construction methods of HTFPs will be elaborated. The performance of the current generation of HTFPs will be compared to that of earlier ones. Current uses of HTFPs will be described. Finally an overview of some remaining research issues will be given including assignment of definitive thermodynamic temperatures and inclusion into the developing mise en pratique for the definition of the kelvin.

Machin, G.

2013-09-01

93

Liquid paraffin as new dilution medium for the analysis of high boiling point residual solvents with static headspace-gas chromatography.  

PubMed

Residual solvents are volatile organic compounds which can be present in pharmaceutical substances. A generic static headspace-gas chromatography analysis method for the identification and control of residual solvents is described in the European Pharmacopoeia. Although this method is proved to be suitable for the majority of samples and residual solvents, the method may lack sensitivity for high boiling point residual solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and benzyl alcohol. In this study, liquid paraffin was investigated as new dilution medium for the analysis of these residual solvents. The headspace-gas chromatography method was developed and optimized taking the official Pharmacopoeia method as a starting point. The optimized method was validated according to ICH criteria. It was found that the detection limits were below 1?g/vial for each compound, indicating a drastically increased sensitivity compared to the Pharmacopoeia method, which failed to detect the compounds at their respective limit concentrations. Linearity was evaluated based on the R(2) values, which were above 0.997 for all compounds, and inspection of residual plots. Instrument and method precision were examined by calculating the relative standard deviations (RSD) of repeated analyses within the linearity and accuracy experiments, respectively. It was found that all RSD values were below 10%. Accuracy was checked by a recovery experiment at three different levels. Mean recovery values were all in the range 95-105%. Finally, the optimized method was applied to residual DMSO analysis in four different Kollicoat() sample batches. PMID:21549541

D'Autry, Ward; Zheng, Chao; Bugalama, John; Wolfs, Kris; Hoogmartens, Jos; Adams, Erwin; Wang, Bochu; Van Schepdael, Ann

2011-07-15

94

Spotlighting quantum critical points via quantum correlations at finite temperatures  

SciTech Connect

We extend the program initiated by T. Werlang et al. [Phys. Rev. Lett. 105, 095702 (2010)] in several directions. Firstly, we investigate how useful quantum correlations, such as entanglement and quantum discord, are in the detection of critical points of quantum phase transitions when the system is at finite temperatures. For that purpose we study several thermalized spin models in the thermodynamic limit, namely, the XXZ model, the XY model, and the Ising model, all of which with an external magnetic field. We compare the ability of quantum discord, entanglement, and some thermodynamic quantities to spotlight the quantum critical points for several different temperatures. Secondly, for some models we go beyond nearest neighbors and also study the behavior of entanglement and quantum discord for second nearest neighbors around the critical point at finite temperature. Finally, we furnish a more quantitative description of how good all these quantities are in spotlighting critical points of quantum phase transitions at finite T, bridging the gap between experimental data and those theoretical descriptions solely based on the unattainable absolute zero assumption.

Werlang, T.; Ribeiro, G. A. P.; Rigolin, Gustavo [Departamento de Fisica, Universidade Federal de Sao Carlos, Sao Carlos, SP 13565-905 (Brazil)

2011-06-15

95

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

96

Thermodynamic temperature measurements of silver freezing point and HTFPs  

NASA Astrophysics Data System (ADS)

The hybrid method, by introducing a lens to the irradiance method, was adopted to measure the thermodynamic temperature at NIM. An absolute radiation thermometer was established with two alternative filter radiometers (633nm and 900nm). The parameters of the absolute radiation thermometer were calibrated. The thermodynamic temperatures of the silver fixed point and Co-C, Pt-C, Re-C were determined. The uncertainties were 0.24K to 0.94K for FR633 and 0.34K to 1.6K for FR900 from the silver point to Re-C. The results were compared with the ITS-90 values and show a good agreement: 0.18K at Co-C, -0.11K at Pt-C and -0.24K at Re-C, which are under the estimated uncertainties.

Yuan, Z.; Lu, X.; Hao, X.; Dong, W.; Wang, T.; Lin, Y.; Wang, J.; Duan, Y.

2013-09-01

97

Superconducting critical temperature near a ferromagnetic quantum critical point.  

NASA Astrophysics Data System (ADS)

We study the superconducting critical temperature near a three dimensional ferromagnetic quantum critical point by solving the Eliashberg equations numerically. A scaling procedure is required to renormalize the frequency cutoff down to numerically accessible values. We use the methods of D. J. Bergmann and D. Rainer, Z. Phys. 263, 59 (1973) to determine the universal behavior of Tc on distance from criticality. Comparison to the 2d results of P. Monthoux and G. G. Lonzarich Phys. Rev. B 59, 14598 (1999) is made.

Roussev, Rossen; Millis, Andrew

2000-03-01

98

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

99

Confinement by carbon nanotubes drastically alters the boiling and critical behavior of water droplets.  

PubMed

Vapor pressure grows rapidly above the boiling temperature, and past the critical point liquid droplets disintegrate. Our atomistic simulations show that this sequence of events is reversed inside carbon nanotubes (CNT). Droplets disintegrate first and at low temperature, while pressure remains low. The droplet disintegration temperature is independent of the CNT diameter. In contrast, depending on CNT diameter, a temperature that is much higher than the bulk boiling temperature is required to raise the internal pressure. The control over pressure by CNT size can be useful for therapeutic drug delivery. PMID:22352413

Chaban, Vitaly V; Prezhdo, Victor V; Prezhdo, Oleg V

2012-03-27

100

High temperature antenna pointing mechanism for BepiColombo mission  

NASA Astrophysics Data System (ADS)

This paper describes the two axis Antenna Pointing Mechanism (APM) with dual frequency (X-Ka bands) Rotary Joint (RJ) developed by Kongsberg Defence and Aerospace and BAE Systems, in the frame of the ESA BepiColombo mission to the planet Mercury. The extreme environmental conditions induced by Mercury's proximity to the Sun (up to 14.500 W/m2 direct solar fluxes, up to 5000 W/m2 infrared flux and up to 1200 W/m2 albedo shine form the planet surface), have dictated the need for a specific high temperature development of the pointing mechanism and of its integrated RF Rotary Joint. Global thermal analysis of the antenna predicts qualification temperature for the elevation stage APM between 250C and 295C. In addition, the mechanism shall survive extreme cold temperatures during the interplanetary cruise phase. Beside the harsh environment, the stringent pointing accuracy required by the antenna high frequency operations, and the extreme dimensional stability demanded by a radio science experiment (which is using the antenna for range and range rate measurements), have introduced additional, specific challenges to the mechanism design. Innovative solutions have been deemed necessary at system architecture level, in the design of the mechanisms critical areas and in the selection of high temperature compatible materials and processes. The very high working temperature of the mechanism ruled out use of aluminium alloys, which is replaced by Titanium alloy and stainless steels. Special heat treatments of the steel are applied for minimum loss of hardness. The structures are optimised for minimum mass. To handle thermal stresses and distortion, a very compact design of the APM was performed integrating the bearings, position sensor and drive chain within minimum structural length. The Rotary Joint is a unique design tailored to the APM using a common main bearing support. Special manufacturing processes have been tested and applied for manufacture of the very compact RJ being the first of its kind (dual X-Ka band) in European space development. The twin channels are arranged concentrically, permitting continuous 360 rotation. Maximum use of waveguide has been made to minimise the loss in the Ka-band frequency channel and this leads to an unconventional design of the X-band channel. A specific effort and extensive test program at ESTL in the UK have been put in place to identify suitable high temperature solutions for the RJ and APM bearings lubrication. The high temperature demands the use of a dry lubrication system. High working loads due to thermal stresses puts extra challenge to the life duration of the dry film lubrication. Lead lubrication was initially the preferred concept, but has later in the program been substituted by MoS2 film. A design life of 20,000 cycles at 250C and elevated load has been demonstrated for the bearings with MoS2. Special attention has been paid to the materials in the stepper motor using high temperature solder material and MoS2 dry lubrication in the bearings and gear train. The APM is designed for use of a high accuracy inductive based position sensor with remote signal and amplifier electronics. Electrical signal transfer is via a high temperature Twist Capsule. The activity has included the design, manufacturing and testing in a respresentative environment of a breadboard model of the APM and of its integrated radio frequency RJ. The breadboard does not include a position sensor or the Twist Capsule. The breadboard tests will include functional performance tests in air, vibration tests and thermal vacuum. The thermal vacuum test will include RF testing at high temperature combined with APM pointing performance.

Mrer, Johan A.; Harper, Richard; Anderson, Mike

2005-07-01

101

Transient boiling heat transfer in saturated liquid nitrogen and F113 at standard and zero gravity  

NASA Technical Reports Server (NTRS)

Transient and steady state nucleate boiling in saturated LN2 and F113 at standard and near zero gravity conditions were investigated for the horizontal up, vertical and horizontal down orientations of the heating surface. Two distinct regimes of heat transfer mechanisms were observed during the interval from the step increase of power input to the onset of nucleate boiling: the conduction and convection dominated regimes. The time duration in each regime was considerably shorter with LN2 than with F113, and decreased as heat flux increased, as gravity was reduced, and as the orientation was changed from horizontal up to horizontal down. In transient boiling, boiling initiates at a single point following the step increase in power, and then spreads over the surface. The delay time for the inception of boiling at the first site, and the velocity of spread of boiling varies depending upon the heat flux, orientation, body force, surface roughness and liquid properties, and are a consequence of changes in boundary layer temperature levels associated with changes in natural convection. Following the step increase in power input, surface temperature overshoot and undershoot occur before the steady state boiling temperature level is established.

Oker, E.; Merte, H., Jr.

1973-01-01

102

Enhanced convective and film boiling heat transfer by surface gas injection  

SciTech Connect

Heat transfer measurements were made for stable film boiling of water over a horizontal, flat stainless steel plate from the minimum film boiling point temperature, T{sub SURFACE} {approximately}500K, to T{sub SURFACE} {approximately}950K. The pressure at the plate was approximately 1 atmosphere and the temperature of the water pool was maintained at saturation. The data were compared to the Berenson film-boiling model, which was developed for minimum film-boiling-point conditions. The model accurately represented the data near the minimum film-boiling point and at the highest temperatures measured, as long it was corrected for the heat transferred by radiation. On the average, the experimental data lay within {plus_minus}7% of the model. Measurements of heat transfer were made without film boiling for nitrogen jetting into an overlying pool of water from nine 1-mm- diameter holes, drilled in the heat transfer plate. The heat flux was maintained constant at approximately 26.4 kW/m{sup 2}. For water-pool heights of less than 6cm the heat transfer coefficient deceased linearly with a decrease in heights. Above 6cm the heat transfer coefficient was unaffected. For the entire range of gas velocities measured [0 to 8.5 cm/s], the magnitude of the magnitude of the heat transfer coefficient only changed by approximately 20%. The heat transfer data bound the Konsetov model for turbulent pool heat transfer which was developed for vertical heat transfer surfaces. This agreement suggests that surface orientation may not be important when the gas jets do not locally affect the surface heat transfer. Finally, a database was developed for heat transfer from the plate with both film boiling and gas jetting occurring simultaneously, in a pool of water maintained at its saturation temperature. The effect of passing nitrogen through established film boiling is to increase the heat transfer from that surface. 60 refs.

Duignan, M.R.; Greene, G.A. [Brookhaven National Lab., Upton, NY (United States); Irvine, T.F., Jr. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Mechanical Engineering

1992-04-01

103

Enhanced convective and film boiling heat transfer by surface gas injection  

SciTech Connect

Heat transfer measurements were made for stable film boiling of water over a horizontal, flat stainless steel plate from the minimum film boiling point temperature, T{sub SURFACE} {approximately}500K, to T{sub SURFACE} {approximately}950K. The pressure at the plate was approximately 1 atmosphere and the temperature of the water pool was maintained at saturation. The data were compared to the Berenson film-boiling model, which was developed for minimum film-boiling-point conditions. The model accurately represented the data near the minimum film-boiling point and at the highest temperatures measured, as long it was corrected for the heat transferred by radiation. On the average, the experimental data lay within {plus minus}7% of the model. Measurements of heat transfer were made without film boiling for nitrogen jetting into an overlying pool of water from nine 1-mm- diameter holes, drilled in the heat transfer plate. The heat flux was maintained constant at approximately 26.4 kW/m{sup 2}. For water-pool heights of less than 6cm the heat transfer coefficient deceased linearly with a decrease in heights. Above 6cm the heat transfer coefficient was unaffected. For the entire range of gas velocities measured (0 to 8.5 cm/s), the magnitude of the magnitude of the heat transfer coefficient only changed by approximately 20%. The heat transfer data bound the Konsetov model for turbulent pool heat transfer which was developed for vertical heat transfer surfaces. This agreement suggests that surface orientation may not be important when the gas jets do not locally affect the surface heat transfer. Finally, a database was developed for heat transfer from the plate with both film boiling and gas jetting occurring simultaneously, in a pool of water maintained at its saturation temperature. The effect of passing nitrogen through established film boiling is to increase the heat transfer from that surface. 60 refs.

Duignan, M.R.; Greene, G.A. (Brookhaven National Lab., Upton, NY (United States)); Irvine, T.F., Jr. (State Univ. of New York, Stony Brook, NY (United States). Dept. of Mechanical Engineering)

1992-04-01

104

Method for Measuring Collimator-Pointing Sensitivity to Temperature Changes  

NASA Technical Reports Server (NTRS)

For a variety of applications, it is important to measure the sensitivity of the pointing of a beam emerging from a collimator, as a function of temperature changes. A straightforward method for carrying out this measurement is based on using interferometry for monitoring the changes in beam pointing, which presents its own problems. The added temperature dependence and complexity issues relating to using an interferometer are addressed by not using an interferometer in the first place. Instead, the collimator is made part of an arrangement that uses a minimum number of low-cost, off-the-shelf materials and by using a quad diode to measure changes in beam pointing. In order to minimize the influence of the test arrangement on the outcome of the measurement, several steps are taken. The collimator assembly is placed on top of a vertical, 1-m-long, fused silica tube. The quad diode is bonded to a fused silica bar, which, in turn, is bonded to the lower end of the fused silica tube. The lower end of the tube rests on a self-aligning support piece, while the upper end of the tube is kept against two rounded setscrew tips, using a soft rubber string. This ensures that very little stress is applied to the tube as the support structure changes dimensions due to thermal expansion. Light is delivered to the collimator through a bare fiber in order to minimize variable bending torque caused by a randomly relaxing, rigid fiber jacket. In order to separate the effect of temperature on the collimator assembly from the effect temperature has on the rest of the setup, multiple measurements are taken with the collimator assembly rotated from measurement to measurement. Laboratory testing, with 1-m spacing between the collimator and the quad diode, has shown that the sensitivity of the arrangement is better than 100 nm rms, over time spans of at least one hour, if the beam path is protected from atmospheric turbulence by a tube. The equivalent sensitivity to detecting changes in pointing angle is 100 nanoradians.

Abramovici, Alex; Cox, Timothy E.; Hein, Randall C.; MacDonald, Daniel R.

2011-01-01

105

Potential Aerospace Applications of High Temperature Superconductors.  

National Technical Information Service (NTIS)

The recent discovery of High Temperature Superconductors (HTS) with superconducting transition temperature, T(sub c), above the boiling point of liquid nitrogen has opened the door for using these materials in new and practical applications. These materia...

R. Selim

1994-01-01

106

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

107

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

108

In-situ Stress Measurements on SUS316L Stainless Steel in High Temperature Water Simulated Boiling Water Reactor  

NASA Astrophysics Data System (ADS)

An in-situ straining device has been developed, which enables one to apply a load of 240 N to a specimen in hot water at 561 K and a pressure of 8 MPa, simulating the environment in a boiling water reactor (BWR). The device is equipped with sapphire glass windows for a light path, that is, the device can be used for dynamic measurements of stress induced in the specimen using a synchrotron radiation facility. In-situ stress measurements have been carried out at SPring-8 (BL02B1) on a specimen prepared from SUS316L stainless steel. Inhomogeneity in stress distribution and time-dependent changes in stress were successfully measured.

Yamamoto, A.; Nakahigashi, S.; Terasawa, M.; Mitamura, T.; Akiniwa, Y.; Yamada, T.; Liu, L.; Shobu, T.; Tsubakino, H.

2007-01-01

109

Electron temperature fluctuations in H II regions. The feasibility of t2 estimates from point-to-point observations  

Microsoft Academic Search

Context: . The spatial electron temperature fluctuations in ionized nebulae that were initially proposed to explain the discrepancies among temperatures obtained from different sensors have been pointed to as the cause of huge inconsistencies among abundances of heavy elements calculated from recombination and forbidden emission lines. Recently, there have been some attempts of direct detection and quantification of spatial temperature

M. V. F. Copetti

2006-01-01

110

TEMPERATURE VARIATION WITH TIME IN A PERENNIALLY BOILING WELL IN THE LONG VALLEY CALDERA, MONO COUNTY, CALIFORNIA; OBSERVATIONS IN CHANCE NO. 1 (1976-1983).  

USGS Publications Warehouse

Chance No. 1 was drilled to a depth of 245. 4 m and cased to a depth of 72. 2 m in 1961. Temperature logs were obtained in 1976, 1982, and 1983, with the casing open to the atmosphere. Water was boiling at the surface of the fluid column on each occasion. Temperatures within the upper part of the cased interval remained virtually identical over the 7-year period. The small differences observed can be ascribed to convective motions in the large-diameter casing and the large geothermal gradient. Above a depth of 160 m in the open hole, temperatures have cooled 5 degree -7 degree C over the 7-year period of observation. The shape of the temperature profiles and their variation with time can be explained by an influx of cool water at about 160 m. The cooling rate is much larger between 1982 and 1983 than that between 1982 and 1976, which suggests that earthquake shaking may be a major contributing factor.

Diment, W. H.; Urban, T. C.; Nathenson, Manuel

1985-01-01

111

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

112

Distributed Fiber-Bragg Grating Temperature Sensors for Real-Time Multiple-Point Temperature Monitoring  

NASA Astrophysics Data System (ADS)

Distributed fiber-optic temperature sensors (DFOTS) are being increasingly deployed in applications requiring 2D or 3D temperature profiling. Fiber Bragg Gratings (FBG's), through the shift of their Bragg wavelength, are well suited for such applications due to their immunity to electromagnetic interference and small physical size and thermal inertia of the sensing element. These characteristics are complemented by the easiness of combining individual gratings in series or parallel arrays that can monitor systems with characteristic dimensions from as small as a few millimeters to as large as several kilometers. To highlight this versatility, we report on the study of two FBG arrays for temperature monitoring. A series array obtained by inserting several discrete FBG's operating at different Bragg wavelengths on a 5-km long fiber strand is used to monitor the temperature at predetermined points along the fiber link. A second, parallel array of FBG's is used to monitor the temperature in a cross-section of a 3 ml vial containing a ferrofluid in magnetic field. The temperature resolution in both cases is better than 1 C. The longitudinal spatial resolution is 5 mm, and the lateral spatial resolution for the parallel array is better than 1 mm.

Rablau, Corneliu; Murphy, Simon

2008-03-01

113

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

114

On the effect of annealing temperature on Curie point in amorphous alloys  

NASA Astrophysics Data System (ADS)

The change in the Curie point of the amorphous alloys of the Fe-Ni-Si-As system is investigated after annealing at temperatures below the crystallization temperature. It is shown that, the higher the crystallization temperature of the alloy, the greater the increase in the Curie point during annealing.

Kornienkov, B. A.; Libman, M. A.; Estrin, E. I.

2014-02-01

115

The Transition From Nucleate Boiling Towards the Convection: Application to the Quenching of Metallic Massive Parts  

NASA Astrophysics Data System (ADS)

In a recent study on thermal aspects of the quenching process, we developed an original device of measurement which allowed to update the competition between the heat transfer modes according to the quenching conditions and the quenched part size. One shows that, according to the range value of Biot number, the more resistive one part is, the more the boiling phases are relatively short. In order to provide relatively precise data for simulation of the quenching process in the case of strongly resistive parts from a thermal point of view, we undertook experiments on the cooling transition from nucleate boiling towards the convection. The obtained experimental results show that the temperature of transition from the nucleate boiling to the convection increases when the bath temperature decreases. We present the differences between the values of convection coefficient according to whether the bath is agitated or not. Experimental results relating are compared to some classical correlations.

Bourouga, Brahim; Gilles, Jrme

2007-04-01

116

Aging and effective temperatures near a critical point.  

PubMed

The orientation fluctuations of the director of a liquid crystal are measured after a quench near the Fredericksz transition, which is a second order transition driven by an electric field. We report experimental evidence that, because of the critical slowing down, the liquid crystal presents several properties of an aging system after the quench, such as power law scaling in times of correlation and response functions. During this slow relaxation, a well defined effective temperature, much larger than the heat bath temperature, can be measured using the fluctuation dissipation relation. PMID:19392339

Joubaud, S; Percier, B; Petrosyan, A; Ciliberto, S

2009-04-01

117

Numerical solution of the point reactor kinetics equations with fuel burn-up and temperature feedback  

Microsoft Academic Search

Point reactor kinetics equations are solved numerically using one group of delayed neutrons and with fuel burn-up and temperature feedback included. To calculate the fraction of one-group delayed neutrons, a group of differential equations are solved by an implicit time method. Using point reactor kinetics equations, changes in mean neutrons density, temperature, and reactivity are calculated in different times during

S. Tashakor; G. Jahanfarnia; M. Hashemi-Tilehnoee

2010-01-01

118

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

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

The life cycle of individual boiling bubbles: Insights from beyond optical imaging  

NASA Astrophysics Data System (ADS)

With a high-speed camera, we have investigated the dynamics of individual vapor bubbles boiling on a laser-heated surface. Their sizes and shapes as they grow and depart from a surface are correlated with simultaneous thermal imaging measurements of the boiling surface using thermoreflectance-based microscopy to measure temperatures of individual stochastic events. Analysis of both the thermal profiles and the bubble shapes suggests the presence of an evaporating liquid microlayer under the developing bubble. Tuning surface and heating properties, we control the shapes of bubbles, ranging from regular periodic growth and departure to stochastic bubbles which exhibit rapid cavitation-like expansion and collapse. Unlike typical cavitation bubbles which collapse and form jets pointed towards the surface, jets from bubbles observed during boiling were observed to be directed away from the surface. By tuning the wettability of the substrate, we will report on how wettability affects the strength and direction of these jets.

Parker, Scott; Bae, Sung Chul; Cahill, David; Granick, Steve

2012-02-01

122

Phase equilibria for high-boiling fossil-fuel distillates  

SciTech Connect

An experimental procedure is described for characterizing high-boiling, distillable fossil-fuel mixtures. A mixture is first separated into narrow-boiling fractions using a spinning-band column operating at low pressure and high reflux. Each fraction is characterized by structural properties as given by the number of atoms per average molecule for the following: carbon, aromatic-, ..cap alpha..-, ..beta..-, and ..gamma..-hydrogen; hydroxyl, ether oxygen; primary and secondary amines, pyridinic nitrogen; and thiophenic sulphur. Phase-equilibrium measurements were made for the crude-oil fractions using closed, constant-volume equilibrium cells. The reported measurements include vapor-pressures of eight fractions and the solubilities of methane, ethane, and carbon dioxide in one fraction. The measurements were made at sub-atmospheric pressures and from 20/sup 0/C to the lower of the atmospheric boiling point of the fraction of 300/sup 0/C. Liquid densities for the fractions were measured over the same temperature range for use in calculating gas solubilities by mass balance. The Redlich-Kwong-Soave equation of state is used to calculate phase equilibria for the systems. Equation-of-state constants are calculated from structural-characterization data. Limited experimental data indicate that vapor pressure calculations for petroleum fractions based on structural data are comparable to those based on specific gravity and normal boiling point. The results of this study suggest that for petroleum fractions, structural data for characterization do not provide significantly improved correlation of vapor pressures when that correlation is based on a simple model like the Soave equation. For effective utilization of structural characterization data, it appears necessary to base correlations on a more realistic molecular model that is more suitable for mixtures of large molecules.

Alexander, G.L.

1985-01-01

123

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

124

Solubility of Solid 2Methyl1,3-butadiene (Isoprene) in Liquid Argon and Nitrogen at the Standard Boiling Points of the Solvents  

Microsoft Academic Search

The solubility of solid 2-methyl-1,3-butadiene (isoprene) in liquid argon at a temperature of 87.3 K and in liquid nitrogen at 77.4 K has been measured by the filtration method. The hydrocarbon contents in solutions were determined using gas chromatography. GCMS was used to identify impurities in the solute. The experimental value of the mole fraction solubility of solid isoprene in

Magdalena Kurdziel; El?bieta Szczepaniec-Cieciak; Monika Watorczyk; Barbara Dabrowska

2004-01-01

125

Cathodic polarization curves of the oxygen reduction reaction on various structural materials of boiling water reactors in high temperaturehigh purity water  

Microsoft Academic Search

Cathodic polarization curves of the O2 reduction reaction were measured by using electrodes made from typical structural materials of boiling water reactors (BWRs) to evaluate the effects of kind of material on the electrochemical corrosion potential (ECP) calculation. To estimate ECPs at any region in the BWRs on the basis of the BWR environmental conditions, anodic and cathodic polarization curves

Masahiko Tachibana; Kazushige Ishida; Yoichi Wada; Ryosuke Shimizu; Nobuyuki Ota; Nobuyoshi Hara

2012-01-01

126

Boiling of an emulsion in a yield stress fluid.  

PubMed

We report the boiling behavior of pentane emulsified in a yield stress fluid, a colloidal clay (Laponite) suspension. We have observed that a superheated state is easily reached: the emulsion, heated more than 50?C above the alkane boiling point, does not boil. Superheating is made possible by the suppression of heterogeneous nucleation in pentane, resulting from the emulsification process, a phenomenon evidenced decades ago in studies of the superheating of two phase fluids. We have furthermore studied the growth of isolated bubbles nucleated in the emulsion. The rate of increase of the bubble radius with time depends on both the temperature and emulsion volume fraction but, rather unexpectedly, does not depend on the fluid rheology. We show that the bubbles grow by diffusion of the alkane through the aqueous phase between liquid droplets and bubbles, analogously to an Ostwald ripening process. The peculiarity of the process reported here is that a layer depleted in oil droplets forms around the bubble, layer to which the alkane concentration gradient is confined. We successfully describe our experimental results with a simple transfer model. PMID:21230481

Guna, Geoffroy; Wang, Ji; d'Espinose, Jean-Baptiste; Lequeux, Franois; Talini, Laurence

2010-11-01

127

``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

128

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

129

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

130

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

131

Distributed Fiber-Bragg Grating Temperature Sensors for Real-Time MultiplePoint Temperature Monitoring  

Microsoft Academic Search

Distributed fiber-optic temperature sensors (DFOTS) are being increasingly deployed in applications requiring 2D or 3D temperature profiling. Fiber Bragg Gratings (FBG's), through the shift of their Bragg wavelength, are well suited for such applications due to their immunity to electromagnetic interference and small physical size and thermal inertia of the sensing element. These characteristics are complemented by the easiness of

Corneliu Rablau; Simon Murphy

2008-01-01

132

Changes in skin surface temperature at an acupuncture point with moxibustion  

PubMed Central

Objective This study evaluates the thermographic changes associated with moxa burner moxibustion at the SP6 acupuncture point to establish an appropriate, safe distance of efficacy for moxibustion. Methods Baseline temperature changes using a moxa burner were obtained for a paper substrate at various distances and times, and the tested with volunteers in a pilot study. A single-group trial was then conducted with 36 healthy women to monitor temperature changes on the body surface at the acupuncture point (SP6). Results Based on the temperature changes seen for the paper substrate and in the pilot study, a distance of 3?cm was chosen as the intervention distance. Moxibustion significantly increased the SP6 point skin surface temperature, with a peak increase of 11C at 4?min (p?<0.001). This study also found that during moxibustion the temperature of the moxa burner's rubber layer and moxa cautery were 56.90.9C and 65.81.2C, as compared to baseline values of 35.1C and 43.8C (p<0.001). Conclusions We determined 3?cm was a safe distance between the moxa burner and acupuncture point. Moxibustion can increase the skin surface temperature at the SP6 point. This data will aid traditional Chinese medicine (TCM) practitioners in gauging safer treatment distances when using moxibustion treatments.

Lin, Li-Mei; Wang, Shu-Fang; Lee, Ru-Ping; Hsu, Bang-Gee; Tsai, Nu-Man; Peng, Tai-Chu

2013-01-01

133

Two-point two-colour pyrometry using the REMS ground temperature sensor  

NASA Astrophysics Data System (ADS)

The REMS ground temperature sensor has two IR bands dedicated to the observation of the daily evolution of the ground temperature. One thermopile has a very good signal-to-noise ratio and provides a clean estimate of the brightness temperature. Here we use the information from the extra channel, during the hours of maximal temperatures, and compare the data of both channels (two-colour) at different acquisitions (two-point) to estimate the kinetic temperature and extract information about the averaged emissivity of each spectral band. This information is compared with emissivities from existing spectral data bases and satellite estimates of the landing area.

Zorzano, Mara-Paz; Martn-Torres, Francisco Javier; Martnez-Fras, Jess; Hamilton, Victoria; Sebastian, Eduardo; Armiens, Carlos; Javier Gmez-Elvira, REMS Team; the MSL Science Team

2013-04-01

134

Acoustic measurements of the thermodynamic temperature between the triple point of mercury and 380 K  

Microsoft Academic Search

We have measured the differences between the Kelvin thermodynamic temperature and the temperature of the International Temperature Scale of 1990 on nine isotherms between the triple point of mercury and 380 K, by means of a primary acoustic thermometer. For the present measurements the standard uncertainty of (T - T90) ranges from 0.9 mK at 234 K to 1.7 mK

G. Benedetto; R. M. Gavioso; R. Spagnolo; P. Marcarino; A. Merlone

2004-01-01

135

EVALUATION OF ROTARY KILN INCINERATOR OPERATION AT LOW TO MODERATE TEMPERATURE CONDITIONS VOLUME 1. TECHNICAL RESULTS  

EPA Science Inventory

A test program was performed at the Environmental Protection Agency Incineration Research Facility to study the effectiveness of incineration at low-to-moderate temperatures in decontaminating soils containing organic compounds with different volatilities (boiling points). The da...

136

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

137

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

138

Electronic rhinological thermometer for three-point air temperature measurement in nasal cavity  

NASA Astrophysics Data System (ADS)

This article describes the design and construction of diagnostic medical system for air temperature measurement in nasal cavity. Concept of three-point thermometer is connected with single point electronic thermometer for air temperature measurement in nasal cavity that was previously constructed [1]. Researches were done in Microsystems and Sensors Research Group (WUT) with cooperation of physicians and laryngologists from Otolaryngology Department, Military Medical Institute, Warsaw. Measurement system consist of microprocessor module which periodically collects samples of air temperature from different part of nasal cavity, measurement head with three temperature sensors, and computer software presenting on-line results, calculating breathing parameters and storing data in database. Air temperature is measured in nasal cavity, middle part cavity and nasopharynx during regular respiration process.

?nieg, Marcin; Paczesny, Daniel; Weremczuk, Jerzy

2008-01-01

139

Modeling of Aerobrake Ballute Stagnation Point Temperature and Heat Transfer to Inflation Gas  

NASA Technical Reports Server (NTRS)

A trailing Ballute drag device concept for spacecraft aerocapture is considered. A thermal model for calculation of the Ballute membrane temperature and the inflation gas temperature is developed. An algorithm capturing the most salient features of the concept is implemented. In conjunction with the thermal model, trajectory calculations for two candidate missions, Titan Explorer and Neptune Orbiter missions, are used to estimate the stagnation point temperature and the inflation gas temperature. Radiation from both sides of the membrane at the stagnation point and conduction to the inflating gas is included. The results showed that the radiation from the membrane and to a much lesser extent conduction to the inflating gas, are likely to be the controlling heat transfer mechanisms and that the increase in gas temperature due to aerodynamic heating is of secondary importance.

Bahrami, Parviz A.

2012-01-01

140

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

141

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

142

Temperature-programmed capillary electrophoresis for the analysis of high-melting point mutants in thalassemias.  

PubMed

The behavior of different sieving polymers for unambiguous determination of point mutations in genomic DNA, based on electrophoresis in thin capillaries, is evaluated. High melters from thalassemia patients are separated by exploiting the principle of denaturing gradient gel electrophoresis, in fact, of its variant utilizing temperature gradients (TGGE), along the migration path, encompassing the melting points of both homo- and heteroduplex, polymerase chain reaction (PCR)-amplified DNA fragments. Unlike TGGE, where the temperature gradient exists along the separation space, the denaturing temperature gradient in the fused-silica capillaries is time-programmed, so as to reach the Tm's of all species under analysis prior to electrophoretic transport past the detector window. The DNA fragments are injected in a capillary maintained (by combined chemical and thermal means) just below the expected Tm values. The deltaT applied is rather minute (1-1.5 degrees C) and the temperature gradient quite shallow (e.g., 0.05 degrees C/min). The denaturing thermal gradient is generated internally, via Joule heat produced by voltage ramps. This method is applied to the analysis of the most common point mutations in thalassemias, characterized by being high melters (in the temperature range of 60-62 degrees C) in presence of 6 M urea. Point mutants are fully resolved into a spectrum of four bands only when poly(N-acryloylaminopropanol) and hydroxyethylcellulose are used. However, the former offers the best separation capability at such high temperatures. PMID:9194597

Gelfi, C; Righetti, P G; Travi, M; Fattore, S

1997-05-01

143

Loop Heat Pipe Operation Using Heat Source Temperature for Set Point Control  

NASA Technical Reports Server (NTRS)

The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly accomplished by cold biasing the reservoir and using electrical heaters to provide the required control power. Using this method, the loop operating temperature can be controlled within +/- 0.5K. However, because of the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP has been carried out to investigate the effects on the LHP operation when the control temperature sensor is placed on the heat source instead of the reservoir. In these tests, the LHP reservoir is cold-biased and is heated by a control heater. Tests results show that it is feasible to use the heat source temperature for feedback control of the LHP operation. Using this method, the heat source temperature can be maintained within a tight range for moderate and high powers. At low powers, however, temperature oscillations may occur due to interactions among the reservoir control heater power, the heat source mass, and the heat output from the heat source. In addition, the heat source temperature could temporarily deviate from its set point during fast thermal transients. The implication is that more sophisticated feedback control algorithms need to be implemented for LHP transient operation when the heat source temperature is used for feedback control.

Ku, Jentung; Paiva, Kleber; Mantelli, Marcia

2011-01-01

144

Efficient reconstruction of local heat fluxes in pool boiling experiments by goal-oriented adaptive mesh refinement  

NASA Astrophysics Data System (ADS)

In this paper, we consider the efficient estimation of local boiling heat fluxes from transient temperature measurements in the heater close to the heater surface. For accurate prediction, heat flux estimation is formulated as a transient three-dimensional (3D) inverse heat conduction problem (IHCP). This inverse problem is ill-posed and cannot be treated straightforwardly by established numerical methods. In order to obtain a regularized stable solution, a large-scale time-dependent PDE-constrained optimization problem has to be solved and an appropriate stopping criterion for the termination of the iterative solution process has to be chosen. Since the boiling heat flux is non-uniformly distributed on the heater surface due to the strong local activity of the boiling process, the use of a fixed uniform spatial discretization is not efficient. Instead, an adaptive mesh refinement strategy can be used to obtain an appropriate discretization which significantly reduces the total computational effort. In this work, we present an automatic algorithm incorporating an adaptive mesh refinement via a heat flux-based a-posteriori error estimation technique. The suggested algorithm can cope with both spatially point-wise or highly resolved temperature observations efficiently. It is applied to real measurement data obtained from two different types of pool boiling experiments. The numerical results show that the computational effort can be reduced significantly for given estimation quality. This adaptive IHCP solution technique can be also viewed as an efficient soft sensor to deduce unmeasurable local boiling heat fluxes.

Heng, Yi; Mhamdi, Adel; Marquardt, Wolfgang

2010-11-01

145

Analysis of Screen Channel LAD Bubble Point Tests in Liquid Oxygen at Elevated Temperature  

NASA Technical Reports Server (NTRS)

The purpose of this paper is to examine the key parameters that affect the bubble point pressure for screen channel Liquid Acquisition Devices in cryogenic liquid oxygen at elevated pressures and temperatures. An in depth analysis of the effect of varying temperature, pressure, and pressurization gas on bubble point is presented. Testing of a 200 x 1400 and 325 x 2300 Dutch Twill screen sample was conducted in the Cryogenics Components Lab 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. Test conditions ranged from 92 to 130K and 0.138 - 1.79 MPa. Bubble point is shown to be a strong function of temperature with a secondary dependence on pressure. The pressure dependence is believed to be a function of the amount of evaporation and condensation occurring at the screen. Good agreement exists between data and theory for normally saturated liquid but the model generally under predicts the bubble point in subcooled liquid. Better correlation with the data is obtained by using the liquid temperature at the screen to determine surface tension of the fluid, as opposed to the bulk liquid temperature.

Hartwig, Jason; McQuillen, John

2011-01-01

146

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

147

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

148

Uniaxial deformation behavior of different polypropylene cast films at temperatures near the melting point  

Microsoft Academic Search

A new apparatus for stretching polypropylenes at elevated temperatures below the melting point at high deformation speeds (up to 750 mm\\/s) is described. In the temperature range of 140-160 C the tensile behavior of polypropylene undergoes a shift from the ductile to the quasi-rubber-like deformation behavior. Furthermore, the deformation behavior is strongly affected by the strain rate. The homogeneity of

Stefan Rettenberger; Ludovic Capt; Helmut Mnstedt; Klaus Stopperka; Johannes Snze

2002-01-01

149

Temperature and Species Measurements of Combustion Produced by a 9-Point Lean Direct Injector  

NASA Technical Reports Server (NTRS)

This paper presents measurements of temperature and relative species concentrations in the combustion flowfield of a 9-point swirl venturi lean direct injector fueled with JP-8. The temperature and relative species concentrations of the flame produced by the injector were measured using spontaneous Raman scattering (SRS). Results of measurements taken at four flame conditions are presented. The species concentrations reported are measured relative to nitrogen and include oxygen, carbon dioxide, and water.

Tedder, Sarah A.; Hicks, Yolanda R.; Locke, Randy J.

2013-01-01

150

Terrestrial and microgravity boiling heat transfer in a dielectrophoretic force field  

Microsoft Academic Search

In order to maintain steady nucleate boiling in microgravity another force must be imposed on the boiling process to replace the buoyancy force. The objective of this study is to investigate the effectiveness of a static electric field for maintaining nucleate boiling in microgravity. Semi-transparent gold-film heaters are used to measure the instantaneous average heater surface temperature and to provide

T. J. Snyder; J. N. Chung

2000-01-01

151

Progress report for the CCT-WG5 high temperature fixed point research plan  

SciTech Connect

An overview of the progress in High Temperature Fixed Point (HTFP) research conducted under the auspices of the CCT-WG5 research plan is reported. In brief highlights are: Provisional long term stability of HTFPs has been demonstrated. Optimum construction methods for HTFPs have been established and high quality HTFPs of Co-C, Pt-C and Re-C have been constructed for thermodynamic temperature assignment. The major sources of uncertainty in the assignment of thermodynamic temperature have been identified and quantified. The status of absolute radiometric temperature measurement has been quantified through the circulation of a set of HTFPs. The measurement campaign to assign low uncertainty thermodynamic temperatures to a selected set of HTFPs will begin in mid-2012. It is envisaged that this will be complete by 2015 leading to HTFPs becoming routine reference standards for radiometry and high temperature metrology.

Machin, G.; Woolliams, E. R. [National Physical Laboratory (NPL), Hampton Road, Teddington, Middlesex,TW11 0LW (United Kingdom)] [National Physical Laboratory (NPL), Hampton Road, Teddington, Middlesex,TW11 0LW (United Kingdom); Anhalt, K. [Physikalisch-Technische Bundesanstalt (PTB), Abbestrasse 2-12, 10587 Berlin (Germany)] [Physikalisch-Technische Bundesanstalt (PTB), Abbestrasse 2-12, 10587 Berlin (Germany); Bloembergen, P. [National Institute of Metrology (NIM), Bei San Huan Dong Lu No. 18, Beijing, 100013 (China)] [National Institute of Metrology (NIM), Bei San Huan Dong Lu No. 18, Beijing, 100013 (China); Sadli, M. [Laboratoire Commun de Mtrologie (LNE-Cnam), 61, rue du Landy, 93210 Saint-Denis, La Plaine (France)] [Laboratoire Commun de Mtrologie (LNE-Cnam), 61, rue du Landy, 93210 Saint-Denis, La Plaine (France); Yamada, Y. [National Measurement Institute of Japan (NMIJ), AIST, Tsukuba, Ibaraki (Japan)] [National Measurement Institute of Japan (NMIJ), AIST, Tsukuba, Ibaraki (Japan)

2013-09-11

152

Progress report for the CCT-WG5 high temperature fixed point research plan  

NASA Astrophysics Data System (ADS)

An overview of the progress in High Temperature Fixed Point (HTFP) research conducted under the auspices of the CCT-WG5 research plan is reported. In brief highlights are: Provisional long term stability of HTFPs has been demonstrated. Optimum construction methods for HTFPs have been established and high quality HTFPs of Co-C, Pt-C and Re-C have been constructed for thermodynamic temperature assignment. The major sources of uncertainty in the assignment of thermodynamic temperature have been identified and quantified. The status of absolute radiometric temperature measurement has been quantified through the circulation of a set of HTFPs. The measurement campaign to assign low uncertainty thermodynamic temperatures to a selected set of HTFPs will begin in mid-2012. It is envisaged that this will be complete by 2015 leading to HTFPs becoming routine reference standards for radiometry and high temperature metrology.

Machin, G.; Anhalt, K.; Bloembergen, P.; Sadli, M.; Yamada, Y.; Woolliams, E. R.

2013-09-01

153

Ultra-high temperature isothermal furnace liners (IFLS) for copper freeze point cells  

NASA Astrophysics Data System (ADS)

Primary Laboratories use large fixed-point cells in deep calibration furnaces utilizing heat pipes to achieve temperature uniformity. This combination of furnace, heat pipe, and cell gives the smallest of uncertainties. The heat pipe, also known as an isothermal furnace liner (IFL), has typically been manufactured with Alloy 600/601 as the envelope material since the introduction of high temperature IFLs over 40 years ago. Alloy 600/601 is a widely available high temperature material, which is compatible with Cesium, Potassium, and Sodium and has adequate oxidation resistance and reasonable high temperature strength. Advanced Cooling Technologies, Inc. (ACT) Alloy 600/Sodium IFLs are rated to 1100C for approximately 1000 hours of operation (based on creep strength). Laboratories interested in performing calibrations and studies around the copper freezing point (1084.62C) were frustrated by the 1000 hours at 1100C limitation and the fact that expensive freeze-point cells were getting stuck and/or crushed inside the IFL. Because of this growing frustration/need, ACT developed an Ultra High Temperature IFL to take advantage of the exceptional high temperature strength properties of Haynes 230.

Dussinger, P. M.; Tavener, J. P.

2013-09-01

154

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

155

Temperature-dependent growth mechanism and microstructure of ZnO nanostructures grown from the thermal oxidation of zinc  

NASA Astrophysics Data System (ADS)

We report a detailed study on the growth morphologies and microstructure of ZnO nanostructures formed from the oxidation of Zn at different temperatures. ZnO shows bicrystalline nanowire morphology for oxidation below the melting point of Zn, and single-crystalline morphology between the melting and boiling points of Zn, and tetrapod morphology above the boiling point of Zn. The morphological and microstructural variations are attributed to the temperature-dependent oxide growth mechanisms, i.e., the oxidation below the melting point of Zn is dominated by a solid-solid transformation process, a liquid-solid process between the melting and boiling points of Zn, and a vapor-solid process above the boiling point of Zn. The understanding of the oxide growth mechanisms from these results may have practical implications for rational control of the morphology, crystallinity, preferential growth directions, shape and aspect ratio of ZnO nanostructures

Yuan, Lu; Wang, Chao; Cai, Rongsheng; Wang, Yiqian; Zhou, Guangwen

2014-03-01

156

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

157

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

158

Reconstruction of an Entropy Source by Temperature Measurements at Discrete Points with Adjoint Methods  

NASA Astrophysics Data System (ADS)

The link between experiments and numerical analysis is a matter of particular concern. Numerical analysis can help to investigate complex and not well measureable flow fields. To this purpose the reconstruction of a flame in a complex channel flow is investigated. The fluidmechanical variables of the flame will be assimilated by means of adjoint methods using temperature measurements at discrete points downstream the flame.

Lemke, M.; Schulze, J.; Sesterhenn, J.

2011-09-01

159

An efficient technique for the point reactor kinetics equations with Newtonian temperature feedback effects  

Microsoft Academic Search

The point reactor kinetics equations of multi-group of delayed neutrons in the presence Newtonian temperature feedback effects are a system of stiff nonlinear ordinary differential equations which have not any exact analytical solution. The efficient technique for this nonlinear system is based on changing this nonlinear system to a linear system by the predicted value of reactivity and solving this

Abdallah A. Nahla

2011-01-01

160

Improvements in the realization of the ITS-90 over the temperature range from the melting point of gallium to the freezing point of silver at NIM  

SciTech Connect

The temperature primary standard over the range from the melting point of gallium to the freezing point of silver in National institute of Metrology (NIM), China, was established in the early 1990s. The performance of all of fixed-point furnaces degraded and needs to be updated due to many years of use. Nowadays, the satisfactory fixed point materials can be available with the development of the modern purification techniques. NIM plans to use a group of three cells for each defining fixed point temperature. In this way the eventual drift of individual cells can be evidenced by periodic intercomparison and this will increase the reliability in disseminating the ITS-90 in China. This article describes the recent improvements in realization of ITS-90 over temperature range from the melting point of gallium to the freezing point of silver at NIM. Taking advantages of the technological advances in the design and manufacture of furnaces, the new three-zone furnaces and the open-type fixed points were developed from the freezing point of indium to the freezing point of silver, and a furnace with the three-zone semiconductor cooling was designed to automatically realize the melting point of gallium. The reproducibility of the new melting point of gallium and the new open-type freezing points of In, Sn, Zn. Al and Ag is improved, especially the freezing points of Al and Ag with the reproducibility of 0.2mK and 0.5mK respectively. The expanded uncertainty in the realization of these defining fixed point temperatures is 0.34mK, 0.44mK, 0.54mK, 0.60mK, 1.30mK and 1.88mK respectively.

Sun, J.; Zhang, J. T.; Ping, Q. [National institute of Metrology, Beijing (China)] [National institute of Metrology, Beijing (China)

2013-09-11

161

Improvements in the realization of the ITS-90 over the temperature range from the melting point of gallium to the freezing point of silver at NIM  

NASA Astrophysics Data System (ADS)

The temperature primary standard over the range from the melting point of gallium to the freezing point of silver in National institute of Metrology (NIM), China, was established in the early 1990s. The performance of all of fixed-point furnaces degraded and needs to be updated due to many years of use. Nowadays, the satisfactory fixed point materials can be available with the development of the modern purification techniques. NIM plans to use a group of three cells for each defining fixed point temperature. In this way the eventual drift of individual cells can be evidenced by periodic intercomparison and this will increase the reliability in disseminating the ITS-90 in China. This article describes the recent improvements in realization of ITS-90 over temperature range from the melting point of gallium to the freezing point of silver at NIM. Taking advantages of the technological advances in the design and manufacture of furnaces, the new three-zone furnaces and the open-type fixed points were developed from the freezing point of indium to the freezing point of silver, and a furnace with the three-zone semiconductor cooling was designed to automatically realize the melting point of gallium. The reproducibility of the new melting point of gallium and the new open-type freezing points of In, Sn, Zn. Al and Ag is improved, especially the freezing points of Al and Ag with the reproducibility of 0.2mK and 0.5mK respectively. The expanded uncertainty in the realization of these defining fixed point temperatures is 0.34mK, 0.44mK, 0.54mK, 0.60mK, 1.30mK and 1.88mK respectively.

Sun, J.; Zhang, J. T.; Ping, Q.

2013-09-01

162

Development of a new radiometer for the thermodynamic measurement of high temperature fixed points  

NASA Astrophysics Data System (ADS)

The National Physical Laboratory (NPL) has developed a new radiometer to measure the thermodynamic melting point temperatures of high temperature fixed points with ultra-low uncertainties. In comparison with the NPL's Absolute Radiation Thermometer (ART), the "THermodynamic Optical Radiometer" (THOR) is more portable and compact, with a much lower size-of-source effect and improved performance in other parameters such as temperature sensitivity. It has been designed for calibration as a whole instrument via the radiance method, removing the need to calibrate the individual subcomponents, as required by ART, and thereby reducing uncertainties. In addition, the calibration approach has been improved through a new integrating sphere that has been designed to have greater uniformity.

Dury, M. R.; Goodman, T. M.; Lowe, D. H.; Machin, G.; Woolliams, E. R.

2013-09-01

163

Development of a new radiometer for the thermodynamic measurement of high temperature fixed points  

SciTech Connect

The National Physical Laboratory (NPL) has developed a new radiometer to measure the thermodynamic melting point temperatures of high temperature fixed points with ultra-low uncertainties. In comparison with the NPL's Absolute Radiation Thermometer (ART), the 'THermodynamic Optical Radiometer' (THOR) is more portable and compact, with a much lower size-of-source effect and improved performance in other parameters such as temperature sensitivity. It has been designed for calibration as a whole instrument via the radiance method, removing the need to calibrate the individual subcomponents, as required by ART, and thereby reducing uncertainties. In addition, the calibration approach has been improved through a new integrating sphere that has been designed to have greater uniformity.

Dury, M. R.; Goodman, T. M.; Lowe, D. H.; Machin, G.; Woolliams, E. R. [National Physical Laboratory, Teddington (United Kingdom)] [National Physical Laboratory, Teddington (United Kingdom)

2013-09-11

164

Optimization of surface temperature distribution for control of point defects in the silicon single crystal  

NASA Astrophysics Data System (ADS)

Optimization of crystal surface temperature distribution is performed for the control of point defects in a silicon single crystal grown by the Czochralski process. In the optimization problem, we seek an optimal solution that minimizes the level of point defects while the radial uniformity of temperature is maximized. In order to solve the optimization problem with the equality constraints described by partial differential equations, the variational principle is used. Based on the calculus of variations and the method of Lagrange multiplier, the Euler-Lagrange equations are derived and solved by the finite difference method. In order to handle inequality constraints, the penalty function method is also applied. The optimal distribution of the crystal surface temperature is expected to provide an insight for the design of thermal surroundings such as the thermal shield configuration and the heater/cooler position.

Sung Woo, Hwa; Hoon Jeong, Ja; Kang, In Seok

2003-01-01

165

Analysis of Screen Channel LAD Bubble Point Tests in Liquid Methane at Elevated Temperature  

NASA Technical Reports Server (NTRS)

This paper examines the effect of varying the liquid temperature and pressure on the bubble point pressure for screen channel Liquid Acquisition Devices in cryogenic liquid methane using gaseous helium across a wide range of elevated pressures and temperatures. Testing of a 325 x 2300 Dutch Twill screen sample was conducted in the Cryogenic Components Lab 7 facility at the NASA Glenn Research Center in Cleveland, Ohio. Test conditions ranged from 105 to 160K and 0.0965 - 1.78 MPa. Bubble point is shown to be a strong function of the liquid temperature and a weak function of the amount of subcooling at the LAD screen. The model predicts well for saturated liquid but under predicts the subcooled data.

Hartwig, Jason; McQuillen, John

2012-01-01

166

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

167

Optimization of the thermogauge furnace for realizing high temperature fixed points  

NASA Astrophysics Data System (ADS)

The thermogauge furnace was commonly used in many NMIs as a blackbody source for calibration of the radiation thermometer. It can also be used for realizing the high temperature fixed point(HTFP). According to our experience, when realizing HTFP we need the furnace provide relative good temperature uniformity to avoid the possible damage to the HTFP. To improve temperature uniformity in the furnace, the furnace tube was machined near the tube ends with a help of a simulation analysis by "ansys workbench". Temperature distributions before and after optimization were measured and compared at 1300 C, 1700C, 2500 C, which roughly correspond to Co-C(1324 C), Pt-C(1738 C) and Re-C(2474 C), respectively. The results clearly indicate that through machining the tube the temperature uniformity of the Thermogage furnace can be remarkably improved. A Pt-C high temperature fixed point was realized in the modified Thermogauge furnace subsequently, the plateaus were compared with what obtained using old heater, and the results were presented in this paper.

Wang, T.; Dong, W.; Liu, F.

2013-09-01

168

Optimization of the thermogauge furnace for realizing high temperature fixed points  

SciTech Connect

The thermogauge furnace was commonly used in many NMIs as a blackbody source for calibration of the radiation thermometer. It can also be used for realizing the high temperature fixed point(HTFP). According to our experience, when realizing HTFP we need the furnace provide relative good temperature uniformity to avoid the possible damage to the HTFP. To improve temperature uniformity in the furnace, the furnace tube was machined near the tube ends with a help of a simulation analysis by 'ansys workbench'. Temperature distributions before and after optimization were measured and compared at 1300 C, 1700C, 2500 C, which roughly correspond to Co-C(1324 C), Pt-C(1738 C) and Re-C(2474 C), respectively. The results clearly indicate that through machining the tube the temperature uniformity of the Thermogage furnace can be remarkably improved. A Pt-C high temperature fixed point was realized in the modified Thermogauge furnace subsequently, the plateaus were compared with what obtained using old heater, and the results were presented in this paper.

Wang, T.; Dong, W. [National Institute of Metrology (NIM), Beijing (China)] [National Institute of Metrology (NIM), Beijing (China); Liu, F. [AVIC China Precision Engineering Institute for Aircraft Industry, Beijing (China)] [AVIC China Precision Engineering Institute for Aircraft Industry, Beijing (China)

2013-09-11

169

Crystallization fouling of finned tubes during pool boiling: effect of fin density  

NASA Astrophysics Data System (ADS)

Bubble characteristics such as density, size, frequency and motion are key factors that contribute to the superiority of nucleate pool boiling over other modes of heat transfer. Nevertheless, if heat transfer occurs in an environment prone to fouling, the very same parameters may lead to accelerated deposit formation due to concentration effects beneath the growing bubbles. This has led to the widely accepted design recommendation to maintain the heat transfer surface temperature below the boiling point if fouling may occur, e.g., in seawater desalination. The present paper aims at investigating the formation of deposits on finned tubes during nucleate pool boiling of CaSO4 solutions. The test finned tubes are low finned tubes with fin densities of 19 and 26 fins/in. made from Cu-Ni. The fouling experiments were carried out at atmospheric pressure for different heat fluxes ranging from 100 to 300 kW/m2 and a CaSO4 concentration of 1.6 g/L. For the sake of comparison, similar runs were performed with smooth stainless steel tubes. The results show that: (1) the fouling resistance decreases with increasing fin density, (2) fouling on the finned tubes was reduced with increasing nucleate boiling activity and (3) if any fouling layer occurred on the finned tubes it could be removed easily.

Esawy, M.; Malayeri, M. R.; Mller-Steinhagen, H.

2010-11-01

170

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

171

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

172

Liquid oxygen liquid acquisition device bubble point tests with high pressure lox at elevated temperatures  

NASA Astrophysics Data System (ADS)

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth's gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMDs) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122 K) as part of NASA's continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures.

Jurns, J. M.; Hartwig, J. W.

2012-04-01

173

Liquid Oxygen Liquid Acquisition Device Bubble Point Tests with High Pressure LOX at Elevated Temperatures  

NASA Technical Reports Server (NTRS)

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth s gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMD) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122K) as part of NASA s continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures.

Jurns, John M.; Hartwig, Jason W.

2011-01-01

174

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

175

Measurement of the in freezing-point temperature: Effect of the liquid-solid interface structure  

NASA Astrophysics Data System (ADS)

The results of the experimental study of the inner interface formation process under different conditions of its initiation for the indium freezing point showed that, depending on the initiation intensity, both the planar structure of the interface on the thermometer well and a noticeable intergrowth of dendrites could be obtained. However, under some specific initiation conditions dendrites disappeared partly or completely in the process of crystallization. The value of the indium freezing point temperature was measured under realization conditions corresponding to different inner interface structure.

Ivanova, A. G.; Abasov, M. Yu.; Gerasimov, S. F.; Pokhodun, A. I.

2013-09-01

176

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

177

Pilot point temperature regulation for thermal lesion control during ultrasound thermal therapy.  

PubMed

The fundamental goal of ultrasound thermal therapy is to provide proper thermal lesion formations for effective tumour treatment. The quality of the therapy depends mostly on its positional precision. To date, most ultrasound thermal therapy treatments have focused on the formation of power or temperature patterns. The non-linear and time-delay effects of thermal dose formation prohibit direct control of the thermal dose distribution. In the paper, the control of thermal lesions by regulation of the temperature of a pilot point is proposed. This scheme utilises the high correlation between temperature elevation and thermal dose at the forward boundary of thermal lesions. To verify the feasibility, a 2D ultrasound phased array system was used to generate thermal lesions of various sizes, and the temperature elevation required to generate a thermal dose threshold was investigated. Results showed that the required temperature elevation was found to be a reasonably constant value of 52.5 degrees C under differing conditions when the focal area was small. When the focal area under consideration was large, the required temperature elevation became a monotonic function of blood perfusion rate, ranging from 49.2 to 52.5 degrees C. When the reference temperature of the pilot point was set at a conservative value (52.5 degrees C), the thermal lesions were controlled precisely under a wide range of blood perfusion and power pattern changes, tested by using a more realistic model that takes into account thermal-induced attenuation and blood perfusion changes. This changed the complex thermal dose control problem into a simple temperature regulation problem, which makes implementation of thermal lesion control easier, giving the scheme a high potential for application to current ultrasound thermal therapy systems. PMID:15125147

Liu, H L; Chen, Y Y; Yen, J Y; Lin, W L

2004-03-01

178

Measurement of the Melting Point Temperature of Several Lithium-Sodium-Beryllium Fluoride Salt (Flinabe) Mixtures  

SciTech Connect

The molten salt Flibe, a combination of lithium and beryllium fluorides studied for molten salt fission reactors, has been proposed as a breeder and coolant for fusion applications. The melting points of 2LiF-BeF{sub 2} and LiF-BeF{sub 2} are 460 deg. C and 363 deg. C, but LiF-BeF{sub 2} is rather viscous and has less lithium for breeding. In the Advanced Power Extraction (APEX) Program, concepts with a free flowing liquid for the first wall and blanket were investigated. Flinabe (a mixture of LiF, BeF{sub 2} and NaF) was selected for a molten salt design because a melting temperature below 350 deg. C appeared possible and this provided an attractive operating temperature window for a reactor. To confirm that a ternary salt with a low melting temperature existed, several combinations of the fluoride salts, LiF, NaF and BeF{sub 2}, were melted in a stainless steel crucible under vacuum. One had an apparent melting temperature of 305 deg. C. The test system, preparation of the mixtures, melting procedures and temperature curves for the melting and cooling are presented along with the apparent melting points. Thermal modeling of the salt pool and crucible is reported in an accompanying paper.

McDonald, J.M; Nygren, R.E.; Lutz, T.J.; Tanaka, T.J; Ulrickson, M.A.; Boyle, T.J.; Troncosa, K.P. [Sandia National Laboratories (United States)

2005-04-15

179

Estimation of the global average temperature with optimally weighted point gauges  

NASA Technical Reports Server (NTRS)

This paper considers the minimum mean squared error (MSE) incurred in estimating an idealized Earth's global average temperature with a finite network of point gauges located over the globe. We follow the spectral MSE formalism given by North et al. (1992) and derive the optimal weights for N gauges in the problem of estimating the Earth's global average temperature. Our results suggest that for commonly used configurations the variance of the estimate due to sampling error can be reduced by as much as 50%.

Hardin, James W.; Upson, Robert B.

1993-01-01

180

Temperature Effects of Point Sources, Riparian Shading, and Dam Operations on the Willamette River, Oregon  

USGS Publications Warehouse

Water temperature is an important factor influencing the migration, rearing, and spawning of several important fish species in rivers of the Pacific Northwest. To protect these fish populations and to fulfill its responsibilities under the Federal Clean Water Act, the Oregon Department of Environmental Quality set a water temperature Total Maximum Daily Load (TMDL) in 2006 for the Willamette River and the lower reaches of its largest tributaries in northwestern Oregon. As a result, the thermal discharges of the largest point sources of heat to the Willamette River now are limited at certain times of the year, riparian vegetation has been targeted for restoration, and upstream dams are recognized as important influences on downstream temperatures. Many of the prescribed point-source heat-load allocations are sufficiently restrictive that management agencies may need to expend considerable resources to meet those allocations. Trading heat allocations among point-source dischargers may be a more economical and efficient means of meeting the cumulative point-source temperature limits set by the TMDL. The cumulative nature of these limits, however, precludes simple one-to-one trades of heat from one point source to another; a more detailed spatial analysis is needed. In this investigation, the flow and temperature models that formed the basis of the Willamette temperature TMDL were used to determine a spatially indexed 'heating signature' for each of the modeled point sources, and those signatures then were combined into a user-friendly, spreadsheet-based screening tool. The Willamette River Point-Source Heat-Trading Tool allows the user to increase or decrease the heating signature of each source and thereby evaluate the effects of a wide range of potential point-source heat trades. The predictions of the Trading Tool were verified by running the Willamette flow and temperature models under four different trading scenarios, and the predictions typically were accurate to within about 0.005 degrees Celsius (?C). In addition to assessing the effects of point-source heat trades, the models were used to evaluate the temperature effects of several shade-restoration scenarios. Restoration of riparian shade along the entire Long Tom River, from its mouth to Fern Ridge Dam, was calculated to have a small but significant effect on daily maximum temperatures in the main-stem Willamette River, on the order of 0.03?C where the Long Tom River enters the Willamette River, and diminishing downstream. Model scenarios also were run to assess the effects of restoring selected 5-mile reaches of riparian vegetation along the main-stem Willamette River from river mile (RM) 176.80, just upstream of the point where the McKenzie River joins the Willamette River, to RM 116.87 near Albany, which is one location where cumulative point-source heating effects are at a maximum. Restoration of riparian vegetation along the main-stem Willamette River was shown by model runs to have a significant local effect on daily maximum river temperatures (0.046 to 0.194?C) at the site of restoration. The magnitude of the cooling depends on many factors including river width, flow, time of year, and the difference in vegetation characteristics between current and restored conditions. Downstream of the restored reach, the cooling effects are complex and have a nodal nature: at one-half day of travel time downstream, shade restoration has little effect on daily maximum temperature because water passes the restoration site at night; at 1 full day of travel time downstream, cooling effects increase to a second, diminished maximum. Such spatial complexities may complicate the trading of heat allocations between point and nonpoint sources. Upstream dams have an important effect on water temperature in the Willamette River system as a result of augmented flows as well as modified temperature releases over the course of the summer and autumn. The TMDL was formulated prior t

Rounds, Stewart A.

2007-01-01

181

Polarization-Switching FBG Interrogator for Distributed Point Measurement of Magnetic Field Strength and Temperature  

Microsoft Academic Search

We report on the design and implementation of a novel optical fiber system for dual point measurement of magnetic field strength and temperature. The system incorporates a polar- ization switching technique that enables ratiometric processing of the orthogonal circularly polarized reflections from low-bire- fringence fiber Bragg gratings. High-resolution magneto-optical measurement of either static or dynamic magnetic fields may be achieved

Philip Orr; Pawe? Niewczas

2011-01-01

182

Cooling trend of the tropical cold point tropopause temperatures and its implications  

Microsoft Academic Search

Operational sounding data (1973-1998) were used to determine cold point tropopause (CPT) characteristics. A cooling trend (-0.57+\\/-0.06K\\/Decade during 1973-1998) in tropical CPT temperatures has been found, which is opposite to what has been hypothesized to explain the trend in stratospheric water vapor. Given this trend, the annual averages of the CPT saturation mixing ratios (SMRs) inferred from the analysis of

Xue-Long Zhou; Marvin A. Geller; Minghua Zhang

2001-01-01

183

Enzymic hydrolysis of animal fats in organic solvents at temperatures below their melting points  

Microsoft Academic Search

Lipase fromCandida rugosa catalyzed the hydrolysis of inedible beef tallow and pork lard (edible and inedible) in the presence of organic solvents\\u000a at temperatures below the melting point of the fat. Reactions were carried out at 50% substrate with 180 lipase units per\\u000a gram of fat in a two-liter reactor. In the presence of isooctane (5-10%) beef tallow yielded 94%

M. D. Virto; Jose Miguel Lascaray; Rodolfo Solozabal; Mertxe de Renobales

1991-01-01

184

Relationship Between Ice Nucleation Temperature Depression and Equilibrium Melting Points Depression of Medaka (Oryzias latipes) Embryos  

NASA Astrophysics Data System (ADS)

We measured the ice nucleation temperature depression , ?Tf , and equilibrium melting points depression, ?Tm, of Medaka (Oryzias latipes) embryos with different cryoprotectant (ethylene glycol, 1.3-propanediol, 1.4-butanediol, glycerol aqueous solutions) treatments. Our obtained results showed the good relationship between the ?Tf ,and ?Tm all samples. In addition the value of ? , which can be obtained from the linear relationship, ?Tf =? ?Tm, were confirmed to show correlation with the value of ? , as obtained by the W/O emulsion method.

Kimizuka, Norihito; Suzuki, Toru

185

Triple point temperature of neon isotopes: Dependence on nitrogen impurity and sealed-cell model  

SciTech Connect

This paper illustrates a study conducted at INRIM, to further check how some quantities influence the value of the triple point temperature of the neon high-purity isotopes {sup 20}Ne and {sup 22}Ne. The influence of nitrogen as a chemical impurity in neon is critical with regard to the present best total uncertainty achieved in the measurement of these triple points, but only one determination is available in the literature. Checks are reported, performed on two different samples of {sup 22}Ne known to contain a N{sub 2} amount of 157?10{sup ?6}, using two different models of sealed cells. The model of the cell can, in principle, have some effects on the shape of the melting plateau or on the triple point temperature observed for the sample sealed in it. This can be due to cell thermal parameters, or because the INRIM cell element mod. c contains many copper wires closely packed, which can, in principle, constrain the interface and induce a premelting-like effect. The reported results on a cell mod. Bter show no evident effect from the cell model and provide a value for the effect of N{sub 2} in Ne liquidus point of 8.6(1.9) ?K ppm N{sub 2}{sup ?1}, only slightly different from the literature datum.

Pavese, F.; Steur, P. P. M.; Giraudi, D. [Istituto Nazionale di Ricerca Metrologica (INRIM), Torino (Italy)] [Istituto Nazionale di Ricerca Metrologica (INRIM), Torino (Italy)

2013-09-11

186

POINT 2011: ENDF/B-VII.1 Beta2 Temperature Dependent Cross Section Library  

SciTech Connect

This report is one in the series of 'POINT' reports that over the years have presented temperature dependent cross sections for the then current version of ENDF/B. In each case I have used my personal computer at home and publicly available data and codes. I have used these in combination to produce the temperature dependent cross sections used in applications and presented in this report. I should mention that today anyone with a personal computer can produce these results. The latest ENDF/B-VII.1 beta2 data library was recently and is now freely available through the National Nuclear Data Center (NNDC), Brookhaven National Laboratory. This release completely supersedes all preceding releases of ENDF/B. As distributed the ENDF/B-VII.1 data includes cross sections represented in the form of a combination of resonance parameters and/or tabulated energy dependent cross sections, nominally at 0 Kelvin temperature. For use in our applications the ENDF/B-VII.1 library has been processed into cross sections at eight neutron reactor like temperatures, between 0 and 2100 Kelvin, in steps of 300 Kelvin (the exception being 293.6 Kelvin, for exact room temperature at 20 Celsius). It has also been processed to five astrophysics like temperatures, 1, 10, 100 eV, 1 and 10 keV. For reference purposes, 300 Kelvin is approximately 1/40 eV, so that 1 eV is approximately 12,000 Kelvin. At each temperature the cross sections are tabulated and linearly interpolable in energy. All results are in the computer independent ENDF-6 character format [R2], which allows the data to be easily transported between computers. In its processed form the POINT 2011 library is approximately 16 gigabyte in size and is distributed on one compressed DVDs (see, below for the details of the contents of each DVD).

Cullen, D E

2011-04-07

187

Acoustic resonator providing fixed points of temperature between 0.1 and 2 K  

NASA Astrophysics Data System (ADS)

Below 2 K the speed of second sound in mixtures of liquid 3He and 4He first increases to a maximum of 30-40 m/s at about 1 K and then decreases again at lower temperatures to values below 15 m/s. The exact values depend on the concentration and pressure of the mixture. This can be exploited to provide fixed points in temperature by utilizing a resonator with appropriate dimensions and frequency to excite standing waves in the resonator cavity filled with helium mixture. We demonstrate that commercially mass produced quartz tuning forks can be used for this purpose. They are meant for frequency standards operating at 32 kHz. Their dimensions are typically of order 1 mm matching the wavelength of the second sound in helium mixtures at certain values of temperature. Due to the complicated geometry, we observe some 20 sharp acoustic resonances in the range 0.1ell 2 K having temperature resolution of order 1 ?K. The quartz resonators are cheap, compact, simple to implement, easy to measure with great accuracy, and, above all, they are not sensitive to magnetic field, which is a great advantage compared to fixed point devices based on superconductivity transitions. The reproducibility of the resonance pattern upon thermal cycling remains to be verified.

Salmela, Anssi; Tuoriniemi, Juha; Pentti, Elias; Sebedash, Alexander; Rysti, Juho

2009-02-01

188

Thermal modelling comparing high temperature fixed point measurements by contact and non-contact thermometry  

NASA Astrophysics Data System (ADS)

This paper reports thermal modelling that aims to establish if the measurement method - either by a radiation thermometer or by a thermocouple - significantly influences the measured temperature of the high temperature fixed points Co-C, Pd-C and Ru-C. It is clear that both measurement techniques have specific physical characteristics which may affect the temperature measured during the melting plateau. With the radiation thermometer, the radiation heat transfer is directly influenced by the environment because the back-wall is effectively viewing the cold outside environment. In the case of a thermocouple direct viewing of the outside world is blocked so radiation transport is significantly reduced; however, in the case of the thermocouple there is a different component of heat transfer, namely conduction from the thermowell walls in contact with the thermocouple along the thermocouple stem itself.

Castro, P.; Machin, G.; Pearce, J. V.

2013-09-01

189

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

190

Rotational and vibrational temperatures in a hydrogen discharge with a magnetic X-point  

NASA Astrophysics Data System (ADS)

A novel plasma source with a magnetic X-point has been developed to probe an alternative for cesium-free negative hydrogen ion production. This study presents first results for the gas and vibrational temperatures in the source at 1 Pa and various RF powers. The temperatures are obtained from analysis of the intensity distribution of the molecular Fulcher-? bands. The gas temperature increases with the RF power, while the vibrational temperature remains constant in the studied range of RF powers. Both quantities show no appreciable spatial dependence. The obtained high values of the vibrational temperatures indicate a high population of the vibrational levels, favourable for the volume negative ion production. A theoretical concept indicates the presence of an optimum value for the vibrational temperature at which the negative hydrogen ion yield by volume processes has a maximum. Coincidently, the measured value is close to this optimum. This indicates that the novel concept can provide certain advantages compared to other sources based on volume production.

Tsankov, Tsanko V.; Toko, Kaoru; Czarnetzki, Uwe

2012-12-01

191

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

192

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

193

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

194

Experimental evidence of the vapor recoil mechanism in the boiling crisis.  

PubMed

Boiling crisis experiments are carried out in the vicinity of the liquid-gas critical point of H2. A magnetic gravity compensation setup is used to enable nucleate boiling at near critical pressure. The measurements of the critical heat flux that defines the threshold for the boiling crisis are carried out as a function of the distance from the critical point. The obtained power law behavior and the boiling crisis dynamics agree with the predictions of the vapor recoil mechanism and disagree with the classical vapor column mechanism. PMID:17155547

Nikolayev, V S; Chatain, D; Garrabos, Y; Beysens, D

2006-11-01

195

Localized saddle-point search and application to temperature-accelerated dynamics  

NASA Astrophysics Data System (ADS)

We present a method for speeding up temperature-accelerated dynamics (TAD) simulations by carrying out a localized saddle-point (LSAD) search. In this method, instead of using the entire system to determine the energy barriers of activated processes, the calculation is localized by only including a small chunk of atoms around the atoms directly involved in the transition. Using this method, we have obtained N-independent scaling for the computational cost of the saddle-point search as a function of system size N. The error arising from localization is analyzed using a variety of model systems, including a variety of activated processes on Ag(100) and Cu(100) surfaces, as well as multiatom moves in Cu radiation damage and metal heteroepitaxial growth. Our results show significantly improved performance of TAD with the LSAD method, for the case of Ag/Ag(100) annealing and Cu/Cu(100) growth, while maintaining a negligibly small error in energy barriers.

Shim, Yunsic; Callahan, Nathan B.; Amar, Jacques G.

2013-03-01

196

Localized saddle-point search and application to temperature-accelerated dynamics  

SciTech Connect

We present a method for speeding up temperature-accelerated dynamics (TAD) simulations by carrying out a localized saddle-point (LSAD) search. In this method, instead of using the entire system to determine the energy barriers of activated processes, the calculation is localized by only including a small chunk of atoms around the atoms directly involved in the transition. Using this method, we have obtained N-independent scaling for the computational cost of the saddle-point search as a function of system size N. The error arising from localization is analyzed using a variety of model systems, including a variety of activated processes on Ag(100) and Cu(100) surfaces, as well as multiatom moves in Cu radiation damage and metal heteroepitaxial growth. Our results show significantly improved performance of TAD with the LSAD method, for the case of Ag/Ag(100) annealing and Cu/Cu(100) growth, while maintaining a negligibly small error in energy barriers.

Shim, Yunsic; Amar, Jacques G. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Callahan, Nathan B. [Department of Physics and Astronomy, University of Toledo, Toledo, Ohio 43606 (United States); Department of Physics, Indiana University, Bloomington, Indiana 47405 (United States)

2013-03-07

197

Application of the phase equilibrium method for generation of -100 C of humid gas frost-point temperature  

NASA Astrophysics Data System (ADS)

Realization of the phase equilibrium method for very low frost-point temperature generation of a humid gas is presented. A theoretical approach to the analysis of thermodynamic processes of the phase equilibrium achievement is suggested. On the basis of theoretical and experimental analyses, preliminary and main saturators, as parts of the standard low frost-point humidity generator, are designed, enabling us to generate down to -100 C of frost-point temperature.

Mamontov, George

2000-06-01

198

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

199

Correlated electron current and temperature dependence oftheconductance of a quantum point contact  

Microsoft Academic Search

.We investigate finite temperature corrections to the Landauer formula\\u000a due to electronelectron interaction within the quantum point contact.\\u000a When the Fermi level is close to the barrier height, the conducting\\u000a wavefunctions become peaked on the barrier, enhancing the\\u000a electronelectron interaction. At the same time, away from the contact\\u000a the interaction is strongly suppressed by screening. To describe\\u000a electron transport we

C. Sloggett; A. I. Milstein; O. P. Sushkov

2008-01-01

200

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

201

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

202

An updated global grid point surface air temperature anomaly data set: 1851--1990  

SciTech Connect

This document presents land-based monthly surface air temperature anomalies (departures from a 1951--1970 reference period mean) on a 5{degree} latitude by 10{degree} longitude global grid. Monthly surface air temperature anomalies (departures from a 1957--1975 reference period mean) for the Antarctic (grid points from 65{degree}S to 85{degree}S) are presented in a similar way as a separate data set. The data were derived primarily from the World Weather Records and the archives of the United Kingdom Meteorological Office. This long-term record of temperature anomalies may be used in studies addressing possible greenhouse-gas-induced climate changes. To date, the data have been employed in generating regional, hemispheric, and global time series for determining whether recent (i.e., post-1900) warming trends have taken place. This document also presents the monthly mean temperature records for the individual stations that were used to generate the set of gridded anomalies. The periods of record vary by station. Northern Hemisphere station data have been corrected for inhomogeneities, while Southern Hemisphere data are presented in uncorrected form. 14 refs., 11 figs., 10 tabs.

Sepanski, R.J.; Boden, T.A.; Daniels, R.C.

1991-10-01

203

Evidences of the fractional kinetics in temperature region: Evolution of extreme points in ibuprofen  

NASA Astrophysics Data System (ADS)

Based on a new approach presented in detail in this paper one can find new evidences of existence of the fractional kinetics not only in the frequency range. One can find rather general principles of detection of different collective motions in temperature region. These principles can be expressed in terms of an algorithm (defined in the paper as an approach). This approach includes some steps that help to separate a couple of the neighboring collective motions (expressed in the frequency range as a linear combination of two power-law exponents) from each other and establish the temperature evolution of the extreme point that follows to the generalized Vogel-Fulcher-Tamman (VFT)-equation. This experimentally confirmed fact gives new evidences for supporting of the theory of dielectric relaxation based on the fractional kinetics on the frequency/temperature domain. As an example for verification of this new approach the ibuprofen complex permittivity data measured in the wide frequency/temperature range were chosen. The reason of such selection was the following. It helps to compare the conventional study of this complex substance recently published in [1] and use possibilities of the developed approach that can add some new features to the picture obtained in the frame of the conventional treatment. We suppose that possibilities presented by new approach will be extremely useful for detection of different collective motions in other substances studied by the method of broadband dielectric spectroscopy (BDS).

Nigmatullin, Raoul R.; Brs, Ana R.; Correia, Natlia T.

2010-10-01

204

Intramuscular Temperature Differences Between the Mid-Point and Peripheral Effective Radiating Area With Ultrasound  

PubMed Central

The purpose of the study was to determine whether uniform intramuscular heating is achieved throughout a treatment area 2 times the transducer head at both 1 and 3 MHz. Seven male and three female subjects (Age: 23.6 1.0 yrs, Weight: 83.8 23.2 kg, Site Skinfold: 13.9 7.3 mm) underwent two ultrasound treatments (1 and 3 MHz) in the triceps surae muscle group. Thermocouples were inserted at the midpoint and periphery of the treatment area. Ten minute baseline temperatures were recorded followed by a ten minute ultrasound treatment. Two (site) X 10 (time) repeated measures ANOVAs were separately used to determine significance for 1 and 3 MHz treatments. Post-hoc testing was performed using the Bonferroni adjustment. A significant site-by-time interaction was observed for both the 1 and 3 MHz treatments. From baseline to the end of the treatment, temperature increased approximately 2.62C and 1.58C for the midpoint and periphery of the 1 MHz treatment and 5.88C and 3.64C for the 3 MHz treatment. The differences in temperature suggest that uniform heating does not occur throughout the treatment area. Key points 3 MHz is more effective in raising intramuscular temperature within ERA. Stroke count/rate of transducer may play a factor in heating tissue. Treatment size may alter uniform heating.

Miller, Michale G.; Longoria, Janae R.; Cheatham, Christopher C.; Baker, Robert J.; Michael, Timothy J.

2008-01-01

205

Isotopic Effects on the Temperature of the Triple Point of Water  

NASA Astrophysics Data System (ADS)

An investigation into the effects of isotopic composition on the triple point temperature of water has been carried out at the National Institute of Metrology (NIM), China, since redefinition of the kelvin with respect to Vienna Standard Mean Ocean Water (V-SMOW) was officially proposed by the Consultative Committee for Thermometry (CCT) in 2005. In this paper, a comparison of four cells with isotopic analyses and relevant results corrected for isotopic composition, employing the isotope correction algorithm recommended by the CCT, is described. The results indicate that, after application of the corrections, the maximum temperature difference between the cells drops from 0.10 mK to 0.02 mK and that these cells are in good agreement within 0.02 mK. Also, temperature deviations arising from isotopic variations fall in the range from -55.9 ?K to + 40.7 ?K. We consider that the distillation temperature and degassing time of the production procedure lead to isotopic variations.

Yan, X. K.; Zhang, J. T.; Wang, Y. L.; Ma, C. F.; Duan, Y. N.

2008-02-01

206

Statistical methods for change-point detection in surface temperature records  

NASA Astrophysics Data System (ADS)

We describe several statistical methods to detect possible change-points in a time series of values of surface temperature measured at a meteorological station, and to assess the statistical significance of such changes, taking into account the natural variability of the measured values, and the autocorrelations between them. These methods serve to determine whether the record may suffer from biases unrelated to the climate signal, hence whether there may be a need for adjustments as considered by M. J. Menne and C. N. Williams (2009) "Homogenization of Temperature Series via Pairwise Comparisons", Journal of Climate 22 (7), 1700-1717. We also review methods to characterize patterns of seasonality (seasonal decomposition using monthly medians or robust local regression), and explain the role they play in the imputation of missing values, and in enabling robust decompositions of the measured values into a seasonal component, a possible climate signal, and a station-specific remainder. The methods for change-point detection that we describe include statistical process control, wavelet multi-resolution analysis, adaptive weights smoothing, and a Bayesian procedure, all of which are applicable to single station records.

Pintar, A. L.; Possolo, A.; Zhang, N. F.

2013-09-01

207

Measurement of the melting point temperature of several lithium-sodium-beryllium fluoride salt (FLINABE) mixtures.  

SciTech Connect

The molten salt Flibe, a combination of lithium and beryllium flourides, was studied for molten salt fission reactors and has been proposed as a breeder and coolant for the fusion applications. 2LiF-BeF{sub 2} melts at 460 C. LiF-BeF{sub 2} melts at a lower temperature, 363 C, but is rather viscous and has less lithium breeder. In the Advanced Power Extraction (APEX) Program, concepts with a free flowing ternary molten salt for the first wall surface and blanket were investigated. The molten salt (FLiNaBe, a ternary mixture of LiF, BeF2 and NaF) salt was selected because a melting temperature below 350 C that would provide an attractive operating temperature window for a reactor application appeared possible. This information came from a Russian binary phase diagram and a US ternary phase diagram in the 1960's that were not wholly consistent. To confirm that a ternary salt with a low melting temperature existed, several combinations of the fluoride salts, LiF, NaF and, BeF{sub 2}, were melted in a small stainless steel crucible under vacuum. The proportions of the three salts were selected to yield conglomerate salts with as low a melting temperature as possible. The temperature of the salts and the crucible were recorded during the melting and subsequent re-solidification using a thermocouple directly in the salt pool and two thermocouples embedded in the crucible. One mixture had an apparent melting temperature of 305 C. Particular attention was paid to the cooling curve of the salt temperature to observe evidence of any mixed intermediate phases between the fully liquid and fully solid states. The clarity, texture, and thickness were observed and noted as well. The test system, preparation of the mixtures, and the melting procedure are described. The temperature curves for the melting and cooling of each of the mixtures are presented along with the apparent melting points. Thermal modeling of the salt pool and crucible was also done and is reported in a separate paper.

Boyle, Timothy J.; Troncosa, Kenneth P.; Nygren, Richard Einar; Lutz, Thomas Joseph; McDonald, Jimmie M.; Tanaka, Tina Joan; Ulrickson, Michael Andrew

2004-09-01

208

Estimating the Contribution of Impurities to the Uncertainty of Metal Fixed-Point Temperatures  

NASA Astrophysics Data System (ADS)

The estimation of the uncertainty component attributable to impurities remains a central and important topic of fixed-point research. Various methods are available for this estimation, depending on the extent of the available information. The sum of individual estimates method has considerable appeal where there is adequate knowledge of the sensitivity coefficients for each of the impurity elements and sufficiently low uncertainty regarding their concentrations. The overall maximum estimate (OME) forsakes the behavior of the individual elements by assuming that the cryoscopic constant adequately represents (or is an upper bound for) the sensitivity coefficients of the individual impurities. Validation of these methods using melting and/or freezing curves is recommended to provide confidence. Recent investigations of indium, tin, and zinc fixed points are reported. Glow discharge mass spectrometry was used to determine the impurity concentrations of the metals used to fill the cells. Melting curves were analyzed to derive an experimental overall impurity concentration (assuming that all impurities have a sensitivity coefficient equivalent to that of the cryoscopic constant). The two values (chemical and experimental) for the overall impurity concentrations were then compared. Based on the data obtained, the pragmatic approach of choosing the larger of the chemical and experimentally derived quantities as the best estimate of the influence of impurities on the temperature of the freezing point is suggested rather than relying solely on the chemical analysis and the OME method to derive the uncertainty component attributable to impurities.

Hill, K. D.

2014-06-01

209

State-of-the-Art Overview of Boiling and Two-Phase Flows in Microchannels  

Microsoft Academic Search

A state-of-the-art overview of recent work on boiling and two-phase flows in microchannels are reviewed, focusing primarily on the high points of recent developments. The topics covered include critical heat fluxes and their prediction in microchannels, new two-phase flow pattern maps, flow regimes and visualization in microchannels, boiling phenomena and flow instabilities in multi-microchannel cooling elements, flow boiling prediction methods

John R. Thome

2006-01-01

210

Collision of drops with a surface in conditions of film boiling, taking account of the temperature dependence of the vapor properties  

SciTech Connect

A simple theory is proposed for the thermal and dynamic process of collision between an indestructible liquid drop and an isothermal wall heated above the Leidenfrost temperature, taking account of arbitrary temperature dependences of the viscosity, density, and heat conduction of the vapor. The solution of the system of equations is obtained in explicit form. In the theory here proposed, the dynamic behavior of the drop does not depend explicitly on the thermal behavior. The variability in vapor properties only influences the thermal effects of the interaction. The influence of variability in the vapor properties is shown for the example of incidence of a water drop at high-temperature surface.

Kazenin, D.A.; Makeev, A.A.

1987-09-01

211

Colour, myoglobin denaturation and storage stability of raw and cooked mutton chops at different end point cooking temperature.  

PubMed

In our study effect of different end point temperature (51C, 65C, 71C and 79C) on physicochemical and storage stability of mutton chops were evaluated. The L* (lightness) value and b* (yellowness) increased (P?point temperature increased. As internal cooking temperature increased soluble myoglobin content decreased with a corresponding increase in percent myoglobin denatured. Raw mutton chops (uncooked) had lower level of oxidation (less TBA values) than cooked mutton irrespective of storage length. Initial APC of raw and cooked mutton chops ranged from log 1.75 to log 3.73 and was lower in higher end point cooking temperature. It can be concluded that as end point temperature increased, mutton chops appear less red and raw mutton had lower level of oxidation than cooked mutton chops. PMID:24803706

Sen, A R; Naveena, B M; Muthukumar, M; Vaithiyanathan, S

2014-05-01

212

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

213

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

214

Effects of different Methods of Preparation of Ice Mantles of Triple Point of Water Cells on the Temporal Behaviour of the Triple-Point Temperatures.  

National Technical Information Service (NTIS)

We report results of an investigation of the temporal variation of the temperature of triple point of water (TPW) cells, in which the ice mantles were prepared by four different techniques using: (1) solid carbon dioxide, (2) an immersion cooler, (3) liqu...

B. W. Mangum G. F. Strouse G. T. Furukawa

2008-01-01

215

The Impact of Isotopic Concentration, Impurities, and Cell Aging on the Water Triple-Point Temperature  

NASA Astrophysics Data System (ADS)

In 2005, the National Institutes of Standards and Technology (NIST) and Flukes Hart Scientific Division initiated a study to validate the isotopic correction algorithm applied to the realization temperature of triple point of water (TPW) cells. Additionally, the study quantified the impact of water sample impurities on the TPW cell realization temperature. For this study, eight TPW cells containing water of the same nominal isotopic concentration as Vienna Standard Mean Ocean Water (VSMOW) were used. Five of the cells were manufactured with fused-quartz envelopes and the remaining three with borosilicate envelopes. One TPW cell of each type was uniquely designed so that water samples could be periodically removed to analyze the isotopic composition and to monitor any changes in water purity with time and thereby correlate changes in composition with changes in realization temperature. The borosilicate TPW cells gave an average drift of -13 ?K yr-1 and the more stable fused-quartz TPW cells gave an average drift of -2 ?K yr-1.

Strouse, G. F.; Zhao, M.

2007-12-01

216

An experimental study of critical heat flux (CHF) in microgravity forced-convection boiling  

Microsoft Academic Search

Pool and forced-convection boiling of FC-72 was conducted in earth gravity and microgravity. A platinum wire heater was used to generate bubbles and provide simultaneous measurement of the heater surface mean temperature. An electrical circuit was built to control the temperature of heater surface. Boiling curves of FC-72 for different flow rates were obtained in the experiment. By using photographic

Yue Ma; J. N. Chung

2001-01-01

217

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

218

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

219

Boiling phenomena in near-critical SF6 observed in weightlessness  

NASA Astrophysics Data System (ADS)

Boiling phenomena in the two-phase region of SF6 close to its critical point have been observed using the high-quality thermal and optical environment of the CNES dedicated facility ALI-DECLIC on board the International Space Station (ISS). The weightlessness environment of the fluid, which cancels buoyancy forces and favorites the three-dimensional spherical shape of the gas bubble, is proven to be an irreplaceable powerful tool for boiling studies. To identify each key mechanism of the boiling phenomena, the ALI-DECLIC experiments have benefited from (i) the well-adapted design of the test cells, (ii) the high-fidelity of the ALI insert teleoperation when long-duration experiment in stable thermal and microgravity environment are required and (iii) the high repeatability of the controlled thermal disturbances. These key mechanisms were observed by light transmission and interferometry technique independently with two sample cells filled with pure SF6 at a near-critical density. The fluid samples are driven away from thermal equilibrium by using a heater directly implemented in the fluid, or a surface heater on a sapphire optical window. In the interferometry cell, the bulk massive heater distinguishes two symmetrical two-phase domains. The modification of the gas bubble shape is observed during heating. In the direct observation cell, the gas bubble is separated by a liquid film from the thin layered transparent heater deposited on the sapphire window. The liquid film drying and the triple contact line motion during heating are observed using light transmission. The experiments have been performed in a temperature range of 10 K below the critical temperature Tc, with special attention to the range 0.1 mK?T-T?3 mK very close to the critical temperature. The unique advantage of this investigation is to provide opportunities to observe the boiling phenomena at very low heat fluxes, thanks to the fine adjustment of the liquid-vapor properties, (e.g. surface tension), by precise control of the distance to the critical point. We present the new observations of the gas bubble spreading over the heating surface which characterizes the regime where vapor bubbles nucleate separately and grow, as well as liquid drying, vapor film formation, triple contact line motion, which are the key mechanisms at the origin of the boiling crisis when the formed vapor film reduces the heat transfer drastically at the heater wall.

Lecoutre, Carole; Garrabos, Yves; Beysens, Daniel; Nikolayev, Vadim; Hahn, Inseob

2014-07-01

220

A novel role of three dimensional graphene foam to prevent heater failure during boiling.  

PubMed

We report a novel boiling heat transfer (NBHT) in reduced graphene oxide (RGO) suspended in water (RGO colloid) near critical heat flux (CHF), which is traditionally the dangerous limitation of nucleate boiling heat transfer because of heater failure. When the heat flux reaches the maximum value (CHF) in RGO colloid pool boiling, the wall temperature increases gradually and slowly with an almost constant heat flux, contrary to the rapid wall temperature increase found during water pool boiling. The gained time by NBHT would provide the safer margin of the heat transfer and the amazing impact on the thermal system as the first report of graphene application. In addition, the CHF and boiling heat transfer performance also increase. This novel boiling phenomenon can effectively prevent heater failure because of the role played by the self-assembled three-dimensional foam-like graphene network (SFG). PMID:23743619

Ahn, Ho Seon; Kim, Ji Min; Park, Chibeom; Jang, Ji-Wook; Lee, Jae Sung; Kim, Hyungdae; Kaviany, Massoud; Kim, Moo Hwan

2013-01-01

221

Bubble point measurements of the system butane + octylbenzene in the temperature range 290--450 K  

SciTech Connect

As a part of research on nitrogen displacement in light-oil reservoirs, the phase behavior of mixtures of a model oil and nitrogen is studied. The model oil consists of methane, butane, and tetradecane or octylbenzene. For reliable phase behavior calculations in the multicomponent system at reservoir conditions -- about 370 K and 50 MPa in the North Sea -- measurements are needed of at least the binary sub-systems in the temperature and pressure range of interest, in order to determine binary interaction coefficients. Bubble points of butane + octylbenzene at eight different mole fractions have been determined at 290--440 K using the synthetic method. The raw experimental data have been fitted using the Peng-Robinson and the Soave-Redlich-Kwong equations of state in combination with a number of different mixing rules.

Leeuw, V.V. de; Poot, W.; Loos, T.W. de; Swaan Arons, J. de (Delft Univ. of Technology (Netherlands). Lab. of Applied Thermodynamics and Phase Equilibria)

1994-01-01

222

Fluctuation-Induced Heat Release from Temperature-Quenched Nuclear Spins near a Quantum Critical Point  

NASA Astrophysics Data System (ADS)

The quasi-two-dimensional quantum antiferromagnet Cr(diethylenetriamine)(O2)2.H2O [1] has a magnetic-field-tuned quantum critical point (QCP) at 12.3 T, where a highly polarized antiferromagnetic phase turns into a field-induced ferromagnetic phase. We report a novel relaxation phenomenon near this QCP: quantum-fluctuation-driven annealing of hydrogen nuclear spins frozen in a non-equilibrium high-energy state by temperature quenching. This relaxation phenomenon, with readily detectable heat release from the nuclear spins as they are annealed, reveals the extent of a quantum critical region around the QCP and provides a unique avenue to investigate the dynamics of the divergent quantum fluctuations that underlie quantum criticality. [1] C. M. Ramsey et al., Chem. Mater. 15, 92 (2003).

Kim, Y. H.; Kaur, N.; Atkins, B. M.; Dalal, N. S.; Takano, Y.

2010-03-01

223

Geothermal point sources identified in a fumarolic ice cave on Erebus volcano, Antarctica using fiber optic distributed temperature sensing  

Microsoft Academic Search

Point sources of volcanic gas supply heat to the Erebus fumarolic ice cavesFlank degassing on Erebus is modulated by barometric pressureDTS is a useful, economical tool for monitoring low temperature fumaroles

Aaron Curtis; Philip Kyle

2011-01-01

224

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

225

Trends in temperature and dew point at the summit of Mount Washington, New Hampshire, 1935-2004.  

NASA Astrophysics Data System (ADS)

Dry and wet bulb temperatures from sling psychrometer measurements taken every six hours from 1935 to 2004 at the summit of Mount Washington, located at 44 16'N, 71 18'W, 1914 m ASL have recently been digitized. Annual temperature has increased by 0.3C, and annual dew point has decreased by 0.4C over this 70-year period. Synoptic temperature has increased most in spring and winter, changing by 1.0C and 0.5C, respectively, while it has decreased slightly in summer and fall. Dew point has decreased in fall, summer, and winter, 0.9C, 0.5C, and 0.4C respectively, and increased by 0.1C in spring. Preliminary analysis suggests that some of the larger trends in winter and spring may be statistically significant; results of Monte Carlo simulations will be reported. Changes in dew point may be attributed to two factors. Decreasing dew points are expected if the temperature increases but the amount of water vapor present stays the same. Alternatively, lower dew points could be indicative of the presence of drier air. Other dew point climatologies of the continental United States for the second half of the century have shown mixed results, with increased dew points evident at some stations, decreased dew points at others, and no clear regional patterns.

Grant, A. N.; Pszenny, A. A.; Fischer, E. V.

2005-05-01

226

Hybrid Interrogation System for Distributed Fiber Strain Sensors and Point Temperature Sensors Based on Pulse Correlation and FBGs  

Microsoft Academic Search

A hybrid interrogation scheme for distributed strain sensors and point temperature sensors is proposed and its feasibility is demonstrated. It exploits the advantages of distributed sensors and point sensors simultaneously. The proposed interrogation scheme uses a wavelength tunable pulse source and wavelength-dependent reflectors for region selective sensing. Experimental results confirm its linear response and a resolution of 0.02% of the

Antonio Bueno; Koji Nonaka; Salvador Sales

2009-01-01

227

49 CFR 173.224 - Packaging and control and emergency temperatures for self-reactive materials.  

Code of Federal Regulations, 2010 CFR

...Self-reactive liquid, sample, temperature control 3233 OP2 3...Self-reactive solid, sample, temperature control 3234 OP2 3...The emergency and control temperatures must be determined in accordance...compatible diluent having a boiling point of not less than...

2010-10-01

228

49 CFR 173.224 - Packaging and control and emergency temperatures for self-reactive materials.  

Code of Federal Regulations, 2010 CFR

...Self-reactive liquid, sample, temperature control 3233 OP2 3...Self-reactive solid, sample, temperature control 3234 OP2 3...The emergency and control temperatures must be determined in accordance...compatible diluent having a boiling point of not less than...

2009-10-01

229

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...

230

Video monitoring of the superheated liquid boiling up at the attainable superheat boundary  

NASA Astrophysics Data System (ADS)

Using video monitoring, we have observed for the first time the phenomenon of heterogeneous boiling up in a liquid at the attainable superheat boundary, where the boiling up is traditionally assumed to be homogeneous. Thus, the proximity of the theoretical superheat temperature to the results of measurements cannot be considered evidence for the correctness of the theory, since one of the basic assumptions (homogeneity of the boiling up process) is not valid.

Ermakov, G. V.; Gurashkin, A. L.; Lipnyagov, E. V.; Perminov, S. A.

2009-12-01

231

Prediction of fuel cladding strain during post-boiling transition operation  

SciTech Connect

To obtain a basic understanding of the integrity of fuel cladding at elevated temperatures characteristic of operation beyond boiling transition in boiling water reactors, a new description of the transient deformation behavior for unirradiated Zircaloy-2 cladding was developed, using the Larson-Miller parameter (LMP) life-fraction approach. It is possible that the LMP life-fraction approach may give useful information to determine the criteria necessary to minimize fuel cladding damage during the post-boiling transition operation.

Arai, S.; Murabayashi, H.; Tanabe, A.

1986-01-01

232

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

233

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

234

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

235

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

236

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

237

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

238

Temperature and thermo-optic coefficient measurements using optical fibre long period gratings operating at phase matching turning point  

NASA Astrophysics Data System (ADS)

The response of optical fibre long period gratings (LPGs), fabricated with precise control of the grating period to operate at or near the phase matching turning point (PMTP), to temperature was studied. The effect of the grating period on sensor performance was studied. The sensitivity of the LPG operating at the phase matching turning point to temperature was 0.99 nm/C for 111.5 ?m grating period that is ca. 7 times higher than that of an LPG operating far from turning point. The possibility of using LPG sensors to determine the thermo-optic coefficient of the surrounding material was explored.

Korposh, S.; Wong, R.; James, S.; Tatam, R.

2013-05-01

239

Point temperature solution for a penny-shaped crack in an infinite transversely isotropic thermo-piezo-elastic medium  

Microsoft Academic Search

The solution of an impermeable penny-shaped crack subjected to a concentrated thermal load (prescribed point temperature) applied arbitrarily at the crack surfaces is derived using the generalized potential theory method. The integral equation governing the temperature field is found to have the same structure as that for the elastic punch problem and the integro-differential equations related to the electroelastic field

W. Q. Chen; C. W. Lim; H. J. Ding

2005-01-01

240

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

241

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

242

The compensation of natural temperature gradient at the measuring point during the sap flow rate determination in trees  

Microsoft Academic Search

The study summarizes the results of the influence of outer temperature gradient on the accuracy of sap flow rate measurements\\u000a in tree trunks by means of thermic-based methods. Particularly it deals with those methods based on the continual accurate\\u000a measurements of temperature differences between the heated part and the part with natural temperature, at the measuring point.\\u000a The battery of

J. ?ermk; J. Ku?era

1981-01-01

243

A cobalt carbon eutectic fixed point for the calibration of contact thermometers at temperatures above 1100 C  

Microsoft Academic Search

A vertical cobalt-carbon (Co-C) eutectic fixed point cell was constructed at PTB to demonstrate its use for improvement of the calibration of noble-metal thermocouples at temperatures above 1100 C. The melting and freezing temperatures of the Co-C eutectic were measured in different high-temperature furnaces at PTB and INMETRO (Brazil) to show its stability by using a Pt\\/Pd thermocouple. The reproducibility

F. Edler; A. C. Baratto

2005-01-01

244

Removal of Lead(II) from Aqueous Solutions using Pre-boiled and Formaldehyde-Treated Onion Skins as a New Adsorbent  

Microsoft Academic Search

The adsorption characteristics of Pb on pre-boiled treated onion skins (PTOS) and formaldehyde-treated onion skins (FTOS) were evaluated. The effects of Pb initial concentration, agitation rate, solution pH, and temperature on Pb adsorption were investigated in batch systems. Pb adsorption was found to increase with increase in initial concentration. The point of zero net charge (PZC) was 6.53. The optimum

Cafer Saka; mer ?ahin; Halil Demir; Mustafa Kahyao?lu

2011-01-01

245

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

246

Results from Boiling Temperature Measurements for Saturated Solutions in the Systems NaCl + KNO{sub 3} + H{sub 2}O, NaNO{sub 3} + KNO{sub 3} + H{sub 2}O, and NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O  

SciTech Connect

Boiling temperature measurements have been made for saturated ternary solutions of NaCl + KNO{sub 3} + H{sub 2}O and NaNO{sub 3} + KNO{sub 3} + H{sub 2}O over the full solute mole fraction range, along with the limiting binary solutions NaCl + H{sub 2}O, NaNO{sub 3} + H{sub 2}O, and KNO{sub 3} + H{sub 2}O. Boiling temperatures have also been measured for the quaternary NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O mixtures with KNO{sub 3}:NaNO{sub 3} mole ratios of 1.01 and 1.19, which corresponding to the eutectic ratio and a near-eutectic ratio for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O subsystem. The maximum boiling temperature found for the NaCl + KNO{sub 3} + H{sub 2}O system is 134 C and for the NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system is 160 C, but boiling temperatures as high as 196 C were measured the NaCl + NaNO{sub 3} + KNO{sub 3} + H{sub 2}O system. These mixture compositions correspond to the major mineral assemblages that are predicted to control the deliquescence relative humidity of salts found by leaching dust samples from the proposed nuclear repository at Yucca Mountain, Nevada.

Rard, J A

2004-10-04

247

Thermodynamic temperature measurements of the melting temperatures of Co-C, Pt-C and Re-C fixed points at NRC  

NASA Astrophysics Data System (ADS)

This paper outlines measurements made at the National Research Council Canada (NRC) of the thermodynamic melting temperatures of Co-C, Pt-C and Re-C fixed points that have been part of the high-temperature fixed-point research plan of Working Group 5 of the Consultative Committee for Thermometry (CCT-WG5) to assign melting temperatures to those fixed points. This document will outline the equipment used, describe the scheme used to calibrate a pyrometer with traceability to a cryogenic electrical substitution radiometer, and detail the method of measuring the fixed points. It will then report the uncertainties in the measurements and the results. A brief description of the improvements that we plan to implement to the scheme to reduce the uncertainties for future measurements will be given. The thermodynamic temperatures determined for the three fixed points are: 1597.776 K with an expanded uncertainty of 0.36 K, 2011.390 K with an expanded uncertainty of 0.55 K, and 2748.056 K with an expanded uncertainty of 0.95 K, for the Co-C, Pt-C and Re-C fixed points, respectively (all expanded uncertainties assume a 95% confidence interval and a Gaussian distribution).

Todd, A. D. W.; Woods, D. J.

2013-02-01

248

Branching points in the low-temperature dipolar hard sphere fluid.  

PubMed

In this contribution, we investigate the low-temperature, low-density behaviour of dipolar hard-sphere (DHS) particles, i.e., hard spheres with dipoles embedded in their centre. We aim at describing the DHS fluid in terms of a network of chains and rings (the fundamental clusters) held together by branching points (defects) of different nature. We first introduce a systematic way of classifying inter-cluster connections according to their topology, and then employ this classification to analyse the geometric and thermodynamic properties of each class of defects, as extracted from state-of-the-art equilibrium Monte Carlo simulations. By computing the average density and energetic cost of each defect class, we find that the relevant contribution to inter-cluster interactions is indeed provided by (rare) three-way junctions and by four-way junctions arising from parallel or anti-parallel locally linear aggregates. All other (numerous) defects are either intra-cluster or associated to low cluster-cluster interaction energies, suggesting that these defects do not play a significant part in the thermodynamic description of the self-assembly processes of dipolar hard spheres. PMID:24116579

Rovigatti, Lorenzo; Kantorovich, Sofia; Ivanov, Alexey O; Tavares, Jos Maria; Sciortino, Francesco

2013-10-01

249

Branching points in the low-temperature dipolar hard sphere fluid  

NASA Astrophysics Data System (ADS)

In this contribution, we investigate the low-temperature, low-density behaviour of dipolar hard-sphere (DHS) particles, i.e., hard spheres with dipoles embedded in their centre. We aim at describing the DHS fluid in terms of a network of chains and rings (the fundamental clusters) held together by branching points (defects) of different nature. We first introduce a systematic way of classifying inter-cluster connections according to their topology, and then employ this classification to analyse the geometric and thermodynamic properties of each class of defects, as extracted from state-of-the-art equilibrium Monte Carlo simulations. By computing the average density and energetic cost of each defect class, we find that the relevant contribution to inter-cluster interactions is indeed provided by (rare) three-way junctions and by four-way junctions arising from parallel or anti-parallel locally linear aggregates. All other (numerous) defects are either intra-cluster or associated to low cluster-cluster interaction energies, suggesting that these defects do not play a significant part in the thermodynamic description of the self-assembly processes of dipolar hard spheres.

Rovigatti, Lorenzo; Kantorovich, Sofia; Ivanov, Alexey O.; Tavares, Jos Maria; Sciortino, Francesco

2013-10-01

250

Observed changes in relative humidity and dew point temperature in coastal regions of Iran  

NASA Astrophysics Data System (ADS)

The analysis of trends in hydroclimatic parameters and assessment of their statistical significance have recently received a great concern to clarify whether or not there is an obvious climate change. In the current study, parametric linear regression and nonparametric Mann-Kendall tests were applied for detecting annual and seasonal trends in the relative humidity (RH) and dew point temperature ( T dew) time series at ten coastal weather stations in Iran during 1966-2005. The serial structure of the data was considered, and the significant serial correlations were eliminated using the trend-free pre-whitening method. The results showed that annual RH increased by 1.03 and 0.28 %/decade at the northern and southern coastal regions of the country, respectively, while annual T dew increased by 0.29 and 0.15C per decade at the northern and southern regions, respectively. The significant trends were frequent in the T dew series, but they were observed only at 2 out of the 50 RH series. The results showed that the difference between the results of the parametric and nonparametric tests was small, although the parametric test detected larger significant trends in the RH and T dew time series. Furthermore, the differences between the results of the trend tests were not related to the normality of the statistical distribution.

Hosseinzadeh Talaee, P.; Sabziparvar, A. A.; Tabari, Hossein

2012-12-01

251

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

252

Investigation of film boiling thermal hydraulics under FCI conditions: results of analyses and a numerical study  

Microsoft Academic Search

Film boiling on the surface of a high-temperature melt jet or of a melt particle is one of key phenomena governing the physics of fuelcoolant interactions (FCIs) which may occur during the course of a severe accident in a light water reactor (LWR). A number of experimental and analytical studies have been performed, in the past, to address film boiling

T. N Dinh; A. T Dinh; R. R Nourgaliev; B. R Sehgal

1999-01-01

253

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

254

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

255

Some Observations on the Use of the Triple Points of Deuterium and Xenon in Interpolation Schemes for Platinum Resistance Thermometers below 273 K  

NASA Astrophysics Data System (ADS)

The use of the triple points of deuterium and xenon is investigated in some interpolation schemes for platinum resistance thermometers between 13.8 K and 273 K. The use of these triple points together is shown to lead to a large sensitivity to errors in the realization of the boiling point of water or the triple point of gallium and of the triple point of xenon for interpolated temperatures below 25 K. The behaviour of these interpolation schemes is presented as evidence that the large non-uniqueness observed in temperature scales between 84 K and 273 K is due in part to measurement errors at the boiling point of water. The use of the triple point of xenon in an interpolation scheme between 25 K and 273 K is shown to lead to a large sensitivity to calibration errors in the triple points of xenon and gallium between 25 K and 54 K.

Kemp, R. C.

1988-01-01

256

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

257

Turning point temperature and competition between relativistic and ponderomotive effects in self-focusing of laser beam in plasma  

SciTech Connect

The propagation characters of Gaussian laser beam in collisionless plasma are investigated by considering the ponderomotive and relativistic nonlinearities. The second-order differential equation of dimensionless beam width parameter is solved numerically, taking into account the effect of electron temperature. The results show that the ponderomotive force does not facilitate the relativistic self-focusing in all intensity ranges. In fact, there exists a certain intensity value that, if below this value, the ponderomotive nonlinearity can contribute to the relativistic self-focusing, or obstruct it, if above. It is also indicated that there is a temperature interval in which self-focusing can occur, while the beam diverges outside of this region. In addition, the results represent the existence of a turning point temperature in the mentioned interval that the self-focusing has the strongest power. The value of the turning point is dependent on laser intensity in which higher intensities result in higher turning point.

Bokaei, B.; Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Jafari Milani, M. R. [Plasma Physics Research School, Tehran (Iran, Islamic Republic of)] [Plasma Physics Research School, Tehran (Iran, Islamic Republic of)

2013-10-15

258

Temperature dependence of transport spin polarization in NdNi5 from point-contact Andreev reflection  

NASA Astrophysics Data System (ADS)

We report a study in which point-contact Andreev reflection (PCAR) spectroscopy using a superconducting Nb tip has been carried out on NdNi5 , a ferromagnet with a Curie temperature of TC7.7K . The measurements were performed over a temperature range of 2-9K , which spans across the ferromagnetic transition temperature. From an analysis of the spectra, we show that (i) the temperature dependence of the extracted value of transport spin polarization closely follows the temperature dependence of the spontaneous magnetization; (ii) the superconducting quasiparticle lifetime shows a large decrease close to the Curie temperature of the ferromagnet. We attribute the latter to the presence of strong ferromagnetic spin fluctuations in the ferromagnet close to the ferromagnetic transition temperature.

Mukhopadhyay, Sourin; Raychaudhuri, Pratap; Joshi, Devang A.; Tomy, C. V.

2007-01-01

259

Polarized optical properties of forsterite from room temperature up to the melting point  

NASA Astrophysics Data System (ADS)

Olivines are the most abundant phases of the Earth's upper mantle. Determining their optical properties under extreme conditions is essential to investigate their lattice dynamics and related structural evolution and to quantify their thermophysical properties. Optical properties of forsterite were determined by acquiring infrared emittance spectra from room temperature up to the melting point along the [100], [010] and [001] polarization directions and over a wide spectral range, from 50 to 15000 cm-1. The fitting of the experimental data by using a semi-quantum dielectric function model provides new results on lattice vibrations and phonon-phonon interactions in forsterite. In particular, a sudden enhancement of anharmonicity at high temperature is observed and is concomitant with the disappearance or brutal change of some modes around 1000K. The normal modes involving Mg1 cation motions are the more impacted and some of them vanish around 1200K. The polarization along [001] direction is more specifically impacted and this change can be linked to the magnesium mobility within M1 sites. This result is consistent with ab initio calculations1 and experimental data on tracer diffusion2 in forsterite that show the presence of an enhanced diffusion of magnesium via M1 sites along [001] direction. These data contribute to explain literature results that show evidences of a change of vibrational behaviour around 1000K, and in particular a strenghtening of lattice anharmonicity 3,4. This vibrational change may impact some important geophysical properties that depends on ionic diffusion, such as creep or electrical conductivity, were magnesium diffusion plays a key role. Finally, absorption coefficient has been calculated over the whole IR range from optical indices, allowing for the evaluation of the contribution of heat transport by radiation in forsterite. 1. J. Brodholt, Am. Mineral. 82, 1049-1053 (1997). 2. S. Chakraborty, J. R. Farver, R. A. Yund, D. C. Rubie, Phys. Chem. Miner. 21, 489-500 (1994). 3. P. Gillet, P. Richet, F. Guyot, G. Fiquet, J. Geophys. Research. B7, 96: 11805-11816 (1991). 4. F. Guyot, Y. Wang, P. Gillet, Y. Ricard, Phys. Earth. Planet. Inter. 98, 17-29 (1996).

Eckes, M.; Gibert, B.; De Sousa Meneses, D.; Malki, M.; Echegut, P.

2012-12-01

260

Route to Room-Temperature Superconductivity from a Practical Point of View  

Microsoft Academic Search

To synthesize a new superconductor which has a critical temperature, Tc, exceeding the room temperature, one needs to know what chemical components to start with. This chapter presents analysis of experimental data which allow one to draw a conclusion about components and the structure of a potential room-temperature superconductor. The two essential components of a room temperature superconductor are large

A. Mourachkine

2007-01-01

261

Integrated hybrid Raman/fiber Bragg grating interrogation scheme for distributed temperature and point dynamic strain measurements.  

PubMed

We propose and experimentally demonstrate the feasibility of an integrated hybrid optical fiber sensing interrogation technique that efficiently combines distributed Raman-based temperature sensing with fiber Bragg grating (FBG)-based dynamic strain measurements. The proposed sensing system is highly integrated, making use of a common optical source/receiver block and exploiting the advantages of both (distributed and point) sensing technologies simultaneously. A multimode fiber is used for distributed temperature sensing, and a pair of FBGs in each discrete sensing point, partially overlapped in the spectral domain, allows for temperature-independent discrete strain measurements. Experimental results report a dynamic strain resolution of 7.8 n?/?Hz within a full range of 1700 ?? and a distributed temperature resolution of 1C at 20 km distance with 2.7 m spatial resolution. PMID:23089781

Zaidi, Farhan; Nannipieri, Tiziano; Soto, Marcelo A; Signorini, Alessandro; Bolognini, Gabriele; Di Pasquale, Fabrizio

2012-10-20

262

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

263

The Boiling eXperiment Facility (BXF) for the Microgravity Science Glovebox (MSG)  

NASA Technical Reports Server (NTRS)

Boiling is an effective means of cooling by removing heat from surfaces through vaporization of a working fluid. It is also affected by both the magnitude and direction of gravity. By conducting pool boiling tests in microgravity, the effect of buoyancy n the overall boiling process and the relative magnitude of other phenomena can be assessed. The Boiling eXperiment Facility (BXF) is being built for the Microgravity Science Glovebox. This facility will conduct two pool boiling studies. The first study the Microheater Array Boiling Experiment (MABE) uses two 96 element microheater arrays, 2.7 mm and 7.0 mm in size, to measure localized hear fluxes while operating at a constant temperature. The other experiment, the Nucleate Pool Boiling eXperiment (NPBX) uses a 85 mm diameter heater wafer that has been "seeded" with five individually-controlled nucleation sites to study bubble nucleation, growth, coalescence and departure. The BXF uses normal-perfluorohexane as the test fluid and will operate between pressures of 60 to 244 Pa. and temperatures of 35 to 60 C. Both sets of experimental heaters are highly instrumented. Pressure and bulk fluid temperature measurements will be made with standard rate video. A high speed video system will be used to visualize the boiling process through the bottom of the MABE heater arrays. The BXF is currently scheduled to fly on Utilization Flight-13A.1 to the ISS with facility integration into the MSG and operation during Increment 15

McQuillen, John; Chao, David; Vergilii, Frank

2006-01-01

264

Enhancement of pool boiling from a vertical rod using guide disks  

SciTech Connect

This report provides experimental and theoretical investigation of the boiling process which used a system of evenly spaced disks to constrain the path of bubbles from point origin to point of collapse. The experiments identified five distinct heat-transfer regimes, two of which (flange and strobe) are unique to this geometry and cannot be explained by conventional heat-transfer correlations. Bubble and wave models developed for flange and strobe boiling, respectively, predict these phenomena with reasonable success.

Whitehouse, J.C.

1992-01-01

265

Enhancement of pool boiling from a vertical rod using guide disks  

SciTech Connect

This report provides experimental and theoretical investigation of the boiling process which used a system of evenly spaced disks to constrain the path of bubbles from point origin to point of collapse. The experiments identified five distinct heat-transfer regimes, two of which (flange and strobe) are unique to this geometry and cannot be explained by conventional heat-transfer correlations. Bubble and wave models developed for flange and strobe boiling, respectively, predict these phenomena with reasonable success.

Whitehouse, J.C.

1992-11-01

266

Liquid Phase Stability Under an Extreme Temperature Gradient  

NASA Astrophysics Data System (ADS)

Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the bulk driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid.

Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

2013-11-01

267

Liquid phase stability under an extreme temperature gradient.  

PubMed

Using nonequilibrium molecular dynamics simulations, we subject bulk liquid to a very high-temperature gradient and observe a stable liquid phase with a local temperature well above the boiling point. Also, under this high-temperature gradient, the vapor phase exhibits condensation into a liquid at a temperature higher than the saturation temperature, indicating that the observed liquid stability is not caused by nucleation barrier kinetics. We show that, assuming local thermal equilibrium, the phase change can be understood from the thermodynamic analysis. The observed elevation of the boiling point is associated with the interplay between the "bulk" driving force for the phase change and surface tension of the liquid-vapor interface that suppresses the transformation. This phenomenon is analogous to that observed for liquids in confined geometries. In our study, however, a low-temperature liquid, rather than a solid, confines the high-temperature liquid. PMID:24329454

Liang, Zhi; Sasikumar, Kiran; Keblinski, Pawel

2013-11-27

268

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

269

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

270

46 CFR 153.908 - Cargo viscosity and melting point information; measuring cargo temperature during discharge...  

Code of Federal Regulations, 2010 CFR

...2010-10-01 2010-10-01 false Cargo viscosity and melting point information; measuring...Cargo Information § 153.908 Cargo viscosity and melting point information; measuring...For Category A or B NLS, the cargo's viscosity at 20 °C in mPa.s and, if the...

2010-10-01

271

46 CFR 153.908 - Cargo viscosity and melting point information; measuring cargo temperature during discharge...  

Code of Federal Regulations, 2010 CFR

...2009-10-01 2009-10-01 false Cargo viscosity and melting point information; measuring...Cargo Information § 153.908 Cargo viscosity and melting point information; measuring...For Category A or B NLS, the cargo's viscosity at 20 °C in mPa.s and, if the...

2009-10-01

272

46 CFR 153.908 - Cargo viscosity and melting point information; measuring cargo temperature during discharge...  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Cargo viscosity and melting point information; measuring...Cargo Information § 153.908 Cargo viscosity and melting point information; measuring...For Category A or B NLS, the cargo's viscosity at 20 °C in mPa.s and, if the...

2013-10-01

273

Hourly predictive Levenberg-Marquardt ANN and multi linear regression models for predicting of dew point temperature  

NASA Astrophysics Data System (ADS)

In this study, the ability of two models of multi linear regression (MLR) and Levenberg-Marquardt (LM) feed-forward neural network was examined to estimate the hourly dew point temperature. Dew point temperature is the temperature at which water vapor in the air condenses into liquid. This temperature can be useful in estimating meteorological variables such as fog, rain, snow, dew, and evapotranspiration and in investigating agronomical issues as stomatal closure in plants. The availability of hourly records of climatic data (air temperature, relative humidity and pressure) which could be used to predict dew point temperature initiated the practice of modeling. Additionally, the wind vector (wind speed magnitude and direction) and conceptual input of weather condition were employed as other input variables. The three quantitative standard statistical performance evaluation measures, i.e. the root mean squared error, mean absolute error, and absolute logarithmic Nash-Sutcliffe efficiency coefficient ( {| {{{Log}}({{NS}})} |} ) were employed to evaluate the performances of the developed models. The results showed that applying wind vector and weather condition as input vectors along with meteorological variables could slightly increase the ANN and MLR predictive accuracy. The results also revealed that LM-NN was superior to MLR model and the best performance was obtained by considering all potential input variables in terms of different evaluation criteria.

Zounemat-Kermani, Mohammad

2012-08-01

274

A polymer electrolyte for operation at temperatures up to 200 C  

Microsoft Academic Search

In developing advanced fuel cells and other electrochemical reactors, it is desirable to combine the advantages of solid polymer electrolytes with the enhanced catalytic activity associated with temperatures above 100 C. This will require polymer electrolytes which retain high ionic conductivity at temperatures above the boiling point of water. One possibility is to equilibrate standard perfluorosulfonic acid polymer electrolytes such

R. Savinell; E. Yeager; D. Tryk; U. Landau; J. Wainright; D. Weng; K. Lux; M. Litt; C. Rogers

1994-01-01

275

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

276

Magnetic susceptibility of high-Curie-temperature alloys near their melting point  

Microsoft Academic Search

An experimental set-up allowing the magnetic susceptibility measurement during the processing of metallic alloys at high temperature in high magnetic fields is described. Curie temperature, melting and solidification can be observed by the magnetic susceptibility variations. Results for a high-Curie-temperature CoSn alloy are presented, together with the effect of the field on the resulting microstructure.

F. Gaucherand; E. Beaugnon

2001-01-01

277

Magnetic susceptibility of high-Curie-temperature alloys near their melting point  

NASA Astrophysics Data System (ADS)

An experimental set-up allowing the magnetic susceptibility measurement during the processing of metallic alloys at high temperature in high magnetic fields is described. Curie temperature, melting and solidification can be observed by the magnetic susceptibility variations. Results for a high-Curie-temperature Co-Sn alloy are presented, together with the effect of the field on the resulting microstructure.

Gaucherand, F.; Beaugnon, E.

2001-01-01

278

"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

279

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

280

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

281

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

282

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

283

Experimental studies of MLI systems at very low boundary temperatures  

Microsoft Academic Search

Experimental results for various multilayer insulation (MLI) systems are summarized for two sizes of tank calorimeters. The cold side boundary temperature was normal boiling point (NBP) helium (4.2 K) with hot boundaries between 30 and 130 K. Heat rate data were obtained for double aluminized Mylar (DAM) and double goldizer Mylar (DGM) radiation shields and for a wide variety of

I. E. Spradley; T. C. Nast; D. J. Frank

1990-01-01

284

An optical fibre system design enabling simultaneous point measurement of magnetic field strength and temperature using low-birefringence FBGs  

Microsoft Academic Search

Fibre measurement of key parameters in nuclear fusion reactor environments, such as the magnetic field strength and temperature, is highly desirable due to the convenience and robustness of optical fibre sensors when compared with conventional electrical sensors. Presently, fibre point sensors for magnetic field are based predominantly on magnetostriction which limits their applicability to this environment. We present an optical

P. Orr; P. Niewczas

2010-01-01

285

Zero-Point Energy: The Case of the Leiden Low-Temperature Laboratory of Heike Kamerlingh Onnes  

Microsoft Academic Search

In this paper we examine the reaction of the Leiden low-temperature laboratory of Heike Kamerlingh Onnes to new ideas in quantum theory. Especially the contributions of Albert Einstein (1906) and Peter Debye (1912) to the theory of specific heat, and the concept of zero-point energy formulated by Max Planck in 1911, gave a boost to solid state research to test

Dirk van Delft

2008-01-01

286

Influence of impurities on the fixed-point temperature of zinc: estimations by the SIE method and practical limitations  

NASA Astrophysics Data System (ADS)

This publication deals with the practical challenge of describing the impurity influence on the fixed-point temperature of zinc. For this, the sum of individual estimate (SIE) approach is applied to miniaturized fixed-point cells (MFPC) filled with high-purity zinc that can be used in industrial applications. This includes comparative analyses by glow discharge mass spectroscopy as well as mass spectroscopy with inductive coupled plasma to quantify the impurity concentrations in zinc. Furthermore, the element-specific and concentration-dependent temperature deviations are presented for the fixed-point material zinc. For this, binary phase diagrams as well as thermal calculations and experimental data were analysed to extract the relevant sensitivity coefficients. Besides, results from SIE analyses of MFPCs are presented and their uncertainties are compared. On this basis, practical limits of the SIE method are identified and discussed.

Krapf, G.; Mammen, H.; Blumrder, G.; Frhlich, T.

2012-07-01

287

Evaluation of Correlations of Flow Boiling Heat Transfer of R22 in Horizontal Channels  

PubMed Central

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels.

Fang, Xiande; Li, Dingkun

2013-01-01

288

Evaluation of correlations of flow boiling heat transfer of R22 in horizontal channels.  

PubMed

The calculation of two-phase flow boiling heat transfer of R22 in channels is required in a variety of applications, such as chemical process cooling systems, refrigeration, and air conditioning. A number of correlations for flow boiling heat transfer in channels have been proposed. This work evaluates the existing correlations for flow boiling heat transfer coefficient with 1669 experimental data points of flow boiling heat transfer of R22 collected from 18 published papers. The top two correlations for R22 are those of Liu and Winterton (1991) and Fang (2013), with the mean absolute deviation of 32.7% and 32.8%, respectively. More studies should be carried out to develop better ones. Effects of channel dimension and vapor quality on heat transfer are analyzed, and the results provide valuable information for further research in the correlation of two-phase flow boiling heat transfer of R22 in channels. PMID:23956695

Zhou, Zhanru; Fang, Xiande; Li, Dingkun

2013-01-01

289

Electrical effects in measurements at the silver point using high temperature SPRTs  

NASA Astrophysics Data System (ADS)

In this work, measurements at the silver point using various types of HTSPRT are conducted, with a focus on finding a reliable thermal and electrical condition for an HTSPRT calibration. Sodium heat pipe furnaces, operating on DC power supply, are used. A platinum wire is bound to the graphite crucible of one of silver point cells used, through which a DC voltage bias can be provided. The effect of the DC voltage bias and of the heat pipe ground-connection to the HTSPRT reading at silver point is evaluated. Cell comparisons are also performed at various ground-connection conditions. A method for estimating the uncertainty due to such effect in an HTSPRT calibration at silver point is proposed.

Widiatmo, J. V.; Harada, K.; Yamazawa, K.; Tamba, J.; Arai, M.

2013-09-01

290

Trend analysis and change point detection of annual and seasonal precipitation and temperature series over southwest Iran  

NASA Astrophysics Data System (ADS)

This paper presents results of trend analysis and change point detection of annual and seasonal precipitation, and mean temperature (TM), maximum temperature (TMAX) and minimum temperature (TMIN) time series of the period 1950-2007. Investigations were carried out for 50 precipitation stations and 39 temperature stations located in southwest Iran. Three statistical tests including Pettitt's test, Sequential Mann-Kendall test (SQ-MK test) and Mann-Kendall rank test (MK-test) were used for the analysis. The results obtained for precipitation series indicated that most stations showed insignificant trends in annual and seasonal series. Out of the stations which showed significant trends, highest numbers were observed during winter season while no significant trends were detected in summer precipitation. Moreover, no decreasing significant trends were detected by statistical tests in annual and seasonal precipitation series. The analysis of temperature trends revealed a significant increase during summer and spring seasons. TMAX was more stable than TMIN and TM, and winter was stable compared to summer, spring and autumn seasons. The results of change point detection indicated that most of the positive significant mutation points in TM, TMAX and TMIN began in the 1990s.

Zarenistanak, Mohammad; Dhorde, Amit G.; Kripalani, R. H.

2014-03-01

291

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

292

Laboratory study of non-aqueous phase liquid and water co-boiling during thermal treatment  

NASA Astrophysics Data System (ADS)

In situ thermal treatment technologies, such as electrical resistance heating and thermal conductive heating, use subsurface temperature measurements in addition to the analysis of soil and groundwater samples to monitor remediation performance. One potential indication of non-aqueous phase liquid (NAPL) removal is an increase in temperature following observations of a co-boiling plateau, during which subsurface temperatures remain constant as NAPL and water co-boil. However, observed co-boiling temperatures can be affected by the composition of the NAPL and the proximity of the NAPL to the temperature measurement location. Results of laboratory heating experiments using single-component and multi-component NAPLs showed that local-scale temperature measurements can be mistakenly interpreted as an indication of the end of NAPL-water co-boiling, and that significant NAPL saturations (1% to 9%) remain despite observed increases in temperature. Furthermore, co-boiling of multi-component NAPL results in gradually increasing temperature, rather than a co-boiling plateau. Measurements of gas production can serve as a complementary metric for assessing NAPL removal by providing a larger-scale measurement integrated over multiple smaller-scale NAPL locations. Measurements of the composition of the NAPL condensate can provide ISTT operators with information regarding the progress of NAPL removal for multi-component sources.

Zhao, C.; Mumford, K. G.; Kueper, B. H.

2014-08-01

293

LANDSCAPE SCALE NON-POINT SOURCE POLLUTION TEMPERATURE ASSESSMENT AND TMDL DEVELOPMENT  

EPA Science Inventory

THIS IS AN ONGOING PROJECT. Elevated river temperature is a significant water quality issue in the Pacific Northwest. For example, over 12,000 miles of perennial streams are designated 303(d) water quality limited due to temperature violation in the State of Oregon. Over t...

294

Loop Heat Pipe Transient Behavior Using Heat Source Temperature for Set Point Control with Thermoelectric Converter on Reservoir  

NASA Technical Reports Server (NTRS)

The LHP operating temperature is governed by the saturation temperature of its reservoir. Controlling the reservoir saturation temperature is commonly done by cold biasing the reservoir and using electrical heaters to provide the required control power. With this method, the loop operating temperature can be controlled within 0.5K or better. However, because the thermal resistance that exists between the heat source and the LHP evaporator, the heat source temperature will vary with its heat output even if the LHP operating temperature is kept constant. Since maintaining a constant heat source temperature is of most interest, a question often raised is whether the heat source temperature can be used for LHP set point temperature control. A test program with a miniature LHP was carried out to investigate the effects on the LHP operation when the control temperature sensor was placed on the heat source instead of the reservoir. In these tests, the LHP reservoir was cold-biased and was heated by a control heater. Test results show that it was feasible to use the heat source temperature for feedback control of the LHP operation. In particular, when a thermoelectric converter was used as the reservoir control heater, the heat source temperature could be maintained within a tight range using a proportional-integral-derivative or on/off control algorithm. Moreover, because the TEC could provide both heating and cooling to the reservoir, temperature oscillations during fast transients such as loop startup could be eliminated or substantially reduced when compared to using an electrical heater as the control heater.

Ku, Jentung; Paiva, Kleber; Mantelli, Marcia

2011-01-01

295

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

296

Two-Dimensional Calculation of Sodium Boiling in sub-Assemblies.  

National Technical Information Service (NTIS)

The geometrical differences between interior and peripheral subchannels affect the flow and temperature fields inside a subassembly. In the case of a loss of flow without scram, these effects are enhanced after boiling has started in the hottest region, d...

D. Grand G. Basque

1979-01-01

297

Scaling theory of the mott transition and breakdown of the Grneisen scaling near a finite-temperature critical end point.  

PubMed

We discuss a scaling theory of the lattice response in the vicinity of a finite-temperature critical end point. The thermal expansivity is shown to be more singular than the specific heat such that the Grneisen ratio diverges as the critical point is approached, except for its immediate vicinity. More generally, we express the thermal expansivity in terms of a scaling function which we explicitly evaluate for the two-dimensional Ising universality class. Recent thermal expansivity measurements on the layered organic conductor ?-(BEDT-TTF)2X close to the Mott transition are well described by our theory. PMID:20867311

Bartosch, Lorenz; de Souza, Mariano; Lang, Michael

2010-06-18

298

High freezing point fuels used for aviation turbine engines  

NASA Technical Reports Server (NTRS)

Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating.

Friedman, R.

1979-01-01

299

Sandwich heating film boiling heat transfer research in narrow rectangle channel  

NASA Astrophysics Data System (ADS)

The narrow rectangle channel heat transfer technique is a new developing heat transfer technique in recent years. In the narrow rectangle channel, film boiling is an important two-phase flow heat transfer process in many engineering application, including steam generator, nuclear reactor and engineering metallurgy. As the temperature of droplet, steam and wall are decided by forced convection heat transfer between the steam and the wall, the droplet and the wall, the steam and the droplet and radiation heat transfer process, which makes heat transfer mechanism of film boiling be difficultly interpretative. Film boiling in narrow rectangle channel is analyzed in the paper, investigating the influence of all kinds of heat transfer processes on film boiling. A rectangle channel film boiling model has been built up using thermodynamic non-equilibrium model.

Wang, Z. H.; Ni, M. J.

2010-03-01

300

Glass Transition and Sticky Point Temperatures and Stability\\/Mobility Diagram of Fruit Powders  

Microsoft Academic Search

Principal components present in fruits are low molecular weight sugars and some organic acids. They have low glass transition\\u000a temperature (T\\u000a g) and are very hygroscopic in their amorphous state, so the dry product becomes sticky. Water acts as a plasticizer and decreases\\u000a the glass transition temperature of the product with the increase in moisture content and water activity. To

S. Jaya; H. Das

2009-01-01

301

An InGaAs detector based radiation thermometer and fixed-point blackbodies for temperature scale realization at NIM  

SciTech Connect

In this paper, we describe an InGaAs detector based radiation thermometer (IRT) and new design of fixed-point blackbodies, including Sn, Zn, Al and Cu, for the establishment of a temperature scale from 200 C to 1085 C at the National Institute of Metrology of China. The construction and calibration of the IRT with the four fixed-point blackbodies are described. Characteristics of the IRT, such as the size-of-source effect, the amplifier performance and its stability are determined. The design of the four fixed-points, with 10 mm diameter of aperture and 0.9999 emissivity, is described. The uncertainty of the scale realization is elaborated.

Hao, X.; Yuan, Z.; Wang, J.; Lu, X. [Division of Thermometry and Materials Evaluation, National Institute of Metrology, Beijing, China, 100013 (China)] [Division of Thermometry and Materials Evaluation, National Institute of Metrology, Beijing, China, 100013 (China)

2013-09-11

302

An InGaAs detector based radiation thermometer and fixed-point blackbodies for temperature scale realization at NIM  

NASA Astrophysics Data System (ADS)

In this paper, we describe an InGaAs detector based radiation thermometer (IRT) and new design of fixed-point blackbodies, including Sn, Zn, Al and Cu, for the establishment of a temperature scale from 200 C to 1085 C at the National Institute of Metrology of China. The construction and calibration of the IRT with the four fixed-point blackbodies are described. Characteristics of the IRT, such as the size-of-source effect, the amplifier performance and its stability are determined. The design of the four fixed-points, with 10 mm diameter of aperture and 0.9999 emissivity, is described. The uncertainty of the scale realization is elaborated.

Hao, X.; Yuan, Z.; Wang, J.; Lu, X.

2013-09-01

303

Quantum point contact displacement transducer for a mechanical resonator at sub-Kelvin temperatures  

SciTech Connect

Highly sensitive displacement transduction of a 1.67 MHz mechanical resonator with a quantum point contact (QPC) formed in a GaAs heterostructure is demonstrated. By positioning the QPC at the point of maximum mechanical strain on the resonator and operating at 80 mK, a displacement responsivity of 3.81 A/m is measured, which represents a two order of magnitude improvement on the previous QPC based devices. By further analyzing the QPC transport characteristics, a sub-Poisson-noise-limited displacement sensitivity of 25 fm/Hz{sup 1/2} is determined which corresponds to a position resolution that is 23 times the standard quantum limit.

Okazaki, Yuma; Mahboob, Imran; Onomitsu, Koji; Sasaki, Satoshi; Yamaguchi, Hiroshi [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)] [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198 (Japan)

2013-11-04

304

Effect of the temperature and dew point of the decarburization process on the oxide subscale of a 3% silicon steel  

NASA Astrophysics Data System (ADS)

The oxide subscale formed on the decarburization annealing of 3% Si-Fe was investigated using microscopy and spectroscopy techniques. It was found that the morphology as well as the molecular structure of the subscale are affected by temperature and dew point. The results suggest that there is an optimum level of internal oxidation and an optimum fayalite/silica ratio in the subscale to achieve a oriented grain silicon steel having a continuous and smooth ceramic film and low core loss.

Cesar, Maria das Graas M. M.; Mantel, Marc J.

2003-01-01

305

Ab initio study of self-diffusion in silicon over a wide temperature range: Point defect states and migration mechanisms  

Microsoft Academic Search

We identified the states of intrinsic point defects underlying the self-diffusion in Si and clarified the change of dominant diffusion mechanism responsible for the self-diffusion over a wide temperature range using ab initio method. We presented a reliable self-diffusion model that the mechanisms of vacancies and self-interstitials dominate below and above 1220 K, respectively. Our calculations provided a clear picture

Shangyi Ma; Shaoqing Wang

2010-01-01

306

Effects of temperature, oxygen concentration, leaf age and seasonal variations on the CO 2 compensation point of Lolium perenne L  

Microsoft Academic Search

Various factors affect the CO2 compensation point of detached leaves of Lolium perenne L. These include oxygen concentration, temperature, leaf age, and season (spring and summer). Analysis of the results using the model of G.D. Farquhar, S. von Caemmerer and J.A. Berry (1980) Planta 149, 7890, indicates that some of the CO2 evolved by leaves in the light is derived

J. Azcn-Bieto; G. D. Farquhar; A. Caballero

1981-01-01

307

Universal finite-temperature properties of a three-dimensional quantum antiferromagnet in the vicinity of a quantum critical point  

NASA Astrophysics Data System (ADS)

We consider a three-dimensional quantum antiferromagnet which can be driven through a quantum critical point (QCP) by varying a tuning parameter g. Starting from the magnetically ordered phase, the Nel temperature will decrease to zero as the QCP is approached. From a generic quantum field theory, together with numerical results from a specific microscopic Heisenberg spin model, we demonstrate the existence of universal behavior near the QCP. We compare our results with available data for TlCuCl3.

Oitmaa, J.; Kulik, Y.; Sushkov, O. P.

2012-04-01

308

Development of a Multi-Point Pyrometer System (MPPS) for measuring surface temperature and emissivity  

SciTech Connect

In support of the US DOE MHD research program, the Diagnostic Instrumentation and Analysis Laboratory (DIAL) has been actively engaged in developing and applying advanced optical diagnostic techniques and instrumentation systems to high temperature coal-fired gas streams for over a decade. One of the earliest diagnostic systems developed by DIAL was a two color pyrometer (TCP). In this system, two commercial single-color pyrometers and a microprocessor system were used to form a TCP which can make accurate measurements of surfaces of unknown emissivity and temperature. This system has been used extensively to make measurements in support of the national MHD program. This report describes this system.

Benton, R.D.; Jang, Ping-Rey

1993-06-01

309

Rotational cars application to simultaneous and multiple-point temperature and concentration determination in a turbulent flow  

NASA Technical Reports Server (NTRS)

Coherent Anti-stokes Raman Scattering (CARS) from the pure rotational Raman lines of N2 is employed to measure the instantaneous rotational temperature of N2 gas at room temperature and below with good spatial resolution. A broad-bandwidth dye laser is used to obtain the entire rotational spectrum from a signal laser pulse; the CARS signal is then dispersed by a spectrograph and recorded on an optical multichannel analyzer. A best-fit temperature is found in several seconds with the aid of a computer for each experimental spectrum by a least squares comparison with calculated spectra. The model used to calculate the theoretical spectra incorporates the temperature and pressure dependence of the pressure-broadened rotational Raman lines, includes the nonresonant background susceptibility, and assumes that the pump laser has a finite linewidth. Temperatures are fit to experimental spectra recorded over the temperature range of 135 to 296K, and over the pressure range of 0.13 to 15.3 atm. In addition to the spatially resolved single point work, we have used multipoint CARS to obtain information from many spatially resolved volume elements along a cylindrical line (0.1 x 0.1 x 2.0 mm). We also obtained qualitative information on the instantaneous species concentration and temperature at 20 spatially resolved volume elements (0.1 x 0.1 x 0.1 mm) along a line.

Snow, J. B.; Murphy, D. V.; Chang, R. K.

1984-01-01

310

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 makeup of the enveloping sublayer, thereby affecting the bubble dynamics and boiling heat transfer. Finally, the computational modeling of Marangoni convection for boiling nuclei at short time transients shows similarity solutions for pure water, and reduced convection with a peak in circulation strength in the presence of surfactants. The peaking corresponds to the characteristic surfactant adsorption time, which has been shown to depend solely upon the surfactant bulk concentration. For the absence of surfactant surface convection, an enhancement in Marangoni convection is observed. Furthermore, for the investigated range of parameters and time scales, the surfactant adsorption at the interface is not characterized by the presence of a stagnant cap. (Abstract shortened by UMI.)

Wasekar, Vivek Mahadeorao

311

Freeze tolerance, supercooling points and ice formation: comparative studies on the subzero temperature survival of limno-terrestrial tardigrades.  

PubMed

Many limno-terrestrial tardigrades live in unstable habitats where they experience extreme environmental conditions such as drought, heat and subzero temperatures. Although their stress tolerance is often related only to the anhydrobiotic state, tardigrades can also be exposed to great daily temperature fluctuations without dehydration. Survival of subzero temperatures in an active state requires either the ability to tolerate the freezing of body water or mechanisms to decrease the freezing point. Considering freeze tolerance in tardigrades as a general feature, we studied the survival rate of nine tardigrade species originating from polar, temperate and tropical regions by cooling them at rates of 9, 7, 5, 3 and 1 degrees C h(-1) down to -30 degrees C then returning them to room temperature at 10 degrees C h(-1). The resulting moderate survival after fast and slow cooling rates and low survival after intermediate cooling rates may indicate the influence of a physical effect during fast cooling and the possibility that they are able to synthesize cryoprotectants during slow cooling. Differential scanning calorimetry of starved, fed and cold acclimatized individuals showed no intraspecific significant differences in supercooling points and ice formation. Although this might suggest that metabolic and biochemical preparation are non-essential prior to subzero temperature exposure, the increased survival rate with slower cooling rates gives evidence that tardigrades still use some kind of mechanism to protect their cellular structure from freezing injury without influencing the freezing temperature. These results expand our current understanding of freeze tolerance in tardigrades and will lead to a better understanding of their ability to survive subzero temperature conditions. PMID:19251996

Hengherr, S; Worland, M R; Reuner, A; Brmmer, F; Schill, R O

2009-03-01

312

Heat transfer in pool boiling of ammonia\\/water mixture  

Microsoft Academic Search

. \\u000a The nonazeotropic binary mixtures such as, methanol\\/water, ethanol\\/water and ammonia\\/water, have variable boiling and dew\\u000a points, depending on the combination of substance and those mass fraction. It is expected to have a higher performance as\\u000a a result of decreasing the thermodynamically irreversible loss, when there is a relevant mass fraction. Therefore, ammonia\\/water\\u000a mixture is expected to use as

Hirofumi Arima; Masanori Monde; Yuhichi Mitsutake

2003-01-01

313

A review on saturated boiling of liquids on tube bundles  

NASA Astrophysics Data System (ADS)

A review of recent investigation on boiling of saturated liquids over plain and enhanced tube bundles has been carried out taking the earlier review works as reference point. The experimental observations of various geometry and performance parameters studied by researchers are analyzed keeping current demand of industries in design and development of compact, efficient heat exchanging devices. The study shows that tube spacing plays an important role in determination of compactness of the heat exchanger.

Swain, Abhilas; Das, Mihir Kumar

2014-05-01

314

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

315

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

316

Influence of Cutting Fluid on Tool Temperature Distribution in Single Point Turning of Steel.  

National Technical Information Service (NTIS)

Results from a study devoted to the cooling effect arising from the use of a water based cutting fluid during the turning of quenched and tempered steel SS2541 using coated hardmetal tool is presented here. Tool temperature distribution with and without a...

H. Chandraesekaran J. O. Johannsson A. Thuvander

1998-01-01

317

On the Curie points and high temperature susceptibilities of Heisenberg model ferromagnetics  

Microsoft Academic Search

The first six coefficients in the expansion of the susceptibility ?, and its inverse, ? , in ascending powers of the reciprocal temperature, have been determined for the Heisenberg model of a ferromagnetic, for any spin value, S, and any lattice. The first five coefficients appropriate to the magnetic specific heat, C, have also been found. For the body-centred and

G. S. Rushbrooke; P. J. Wood

1958-01-01

318

Coherent anti-stokes Raman spectroscopy system for point temperature and major species concentration measurement  

SciTech Connect

The Coherent anti-Stokes Raman Spectroscopy system (CARS) has been developed as a laser-based, advanced, combustion-diagnostic technique to measure temperature and major species concentration. Principles of operation, description of the system and its capabilities, and operational details of this instrument are presented in this report.

Singh, J.P.; Yueh, Fang-Yu

1993-10-01

319

Point Defect Properties of Cd(Zn)Te and TlBr for Room-Temperature Gamma Radiation Detectors  

NASA Astrophysics Data System (ADS)

The effects of various crystal defects in CdTe, Cd1-xZnxTe (CZT), and TlBr are critical for their performance as room-temperature gamma radiation detectors. We use predictive first principles theoretical methods to provide fundamental, atomic scale understanding of the defect properties of these materials to enable design of optimal growth and processing conditions, such as doping, annealing, and stoichiometry. Several recent cases will be reviewed, including (i) accurate calculations of the thermodynamic and electronic properties of native point defects and point defect complexes in CdTe and CZT; (ii) the effects of Zn alloying on the native point defect properties of CZT; (iii) point defect diffusion and binding related to Te clustering in Cd(Zn)Te; (iv) the profound effect of native point defects---principally vacancies---on the intrinsic material properties of TlBr, particularly electronic and ionic conductivity; (v) tailored doping of TlBr to independently control the electronic and ionic conductivity; and (vi) the effects of metal impurities on the electronic properties and device performance of TlBr detectors.

Lordi, Vincenzo

2013-03-01

320

Investigation of the effects of pressure gradient, temperature and wall temperature ratio on the stagnation point heat transfer for circular cylinders and gas turbine vanes  

NASA Technical Reports Server (NTRS)

Low and high pressure shock tubes were designed and constructed for the purpose of obtaining heat transfer data over a temperature range of 390 to 2500 K, pressures of 0.3 to 42 atm, and Mach numbers of 0.15 to 1.5 with and without pressure gradient. A square test section with adjustable top and bottom walls was constructed to produce the favorable and adverse pressure gradient over the flat plate with heat gages. A water cooled gas turbine nozzle cascade which is attached to the high pressure shock tube was obtained to measuse the heat flux over pressure and suction surfaces. Thin-film platinum heat gages with a response time of a few microseconds were developed and used to measure the heat flux for laminar, transition, and turbulent boundary layers. The laminar boundary heat flux on the shock tube wall agreed with Mirel's flat plate theory. Stagnation point heat transfer for circular cylinders at low temperature compared with the theoretical prediction, but for a gas temperature of 922 K the heat fluxes were higher than the predicted values. Preliminary flat plate heat transfer data were measured for laminar, transition, and turbulent boundary layers with and without pressure gradients for free-stream temperatures of 350 to 2575 K and flow Mach numbers of 0.11 to 1.9. The experimental heat flux data were correlated with the laminar and turbulent theories and the agreement was good at low temperatures which was not the case for higher temperatures.

Nagamatsu, H. T.; Duffy, R. E.

1984-01-01

321

Universal low-temperature tricritical point in metallic ferromagnets and ferrimagnets  

NASA Astrophysics Data System (ADS)

An earlier theory of the quantum phase transition in metallic ferromagnets is revisited and generalized in three ways. It is shown that the mechanism that leads to a fluctuation-induced first-order transition in metallic ferromagnets with a low Curie temperature is valid, (1) irrespective of whether the magnetic moments are supplied by the conduction electrons or by electrons in another band, (2) for ferromagnets in the XY and Ising universality classes as well as for Heisenberg ferromagnets, and (3) for any systems with a nonzero homogeneous magnetization, such as ferrimagnets or canted ferromagnets. This vastly expands the class of materials for which a first-order transition at low temperatures is expected, and it explains why strongly anisotropic ferromagnets, such as UGe2, display a first-order transition as well as Heisenberg magnets.

Kirkpatrick, T. R.; Belitz, D.

2012-04-01

322

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

323

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.

324

Hydrogen bonded polymeric multilayer films assembled below and above the cloud point temperature.  

PubMed

Polymeric multilayer films assembled via hydrogen-bonding are witnessing increased interest from the scientific community. Here we report on hydrogen bonded multilayers of tannic acid and neutral poly(2-oxazoline)s. Importantly we demonstrate, to the best of our knowledge, for the first time that a temperature responsive polymer, in this case poly(2-(n-propyl)-2-oxazline), can be assembled below and above its TCP with distinctly different growth mechanisms. PMID:24022339

da Fonseca Antunes, Andr B; Dierendonck, Marijke; Vancoillie, Gertjan; Remon, Jean Paul; Hoogenboom, Richard; De Geest, Bruno G

2013-10-25

325

STEELS CONTAINING NICKEL TREATED AT TEMPERATURES ABOVE AND BELOW THE TOP CRITICAL POINT  

Microsoft Academic Search

A systematic examination of the effect of the hardening temperature on ; the basic mechanical properties of various case-hardened steels was made on 2% Ni-; Mo, 0.75% Ni-Cr, 1% Ni-Cr, 2% Ni-Cr, 2% Ni-Cr-Mo and 4.25% Ni-Cr-Mo steels. ; Data are presented on steels subjected to direct hardening after a pseudo-; casehardening at 920 deg and to single and double

1961-01-01

326

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

327

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

328

A universal reduced glass transition temperature for liquids  

NASA Technical Reports Server (NTRS)

Data on the dependence of the glass transition temperature on the molecular structure for low-molecular-weight liquids are analyzed in order to determine whether Boyer's reduced glass transition temperature (1952) is a universal constant as proposed. It is shown that the Boyer ratio varies widely depending on the chemical nature of the molecule. It is pointed out that a characteristic temperature ratio, defined by the ratio of the sum of the melting temperature and the boiling temperature to the sum of the glass transition temperature and the boiling temperature, is a universal constant independent of the molecular structure of the liquid. The average value of the ratio obtained from data for 65 liquids is 1.15.

Fedors, R. F.

1979-01-01

329

Experimental study of temperature effect on the growth and collapse of cavitation bubbles near a rigid boundary  

NASA Astrophysics Data System (ADS)

The effect of temperature on the dynamics of a laser-induced cavitation bubble is studied experimentally. The growth and collapse of the cavitation bubble are measured by two sensitive fiber-optic sensors based on optical beam deflection (OBD). Cavitation bubble tests are performed in water at different temperatures, and the temperature ranges from freezing point (0C) to near boiling point. The results indicate that both the maximum bubble radius and bubble lifetime are increased with the increase of temperature. During the stage of bubble rapidly collapsing in the vicinity of a solid surface, besides laser ablation effect, both the first and second liquid-jet-induced impulses are also observed. They are both increased with liquid temperature increasing, and then reach a peak, followed by a decrease. The peak appears at the temperature which is approximately the average of freezing and boiling points. The mechanism of liquid temperature influence on cavitation erosion is also discussed.

Liu, Xiu-mei; Long, Zheng; He, Jie; Li, Bei-bei; Liu, Xin-hua; Zhao, Ji-yun; Lu, Jian; Ni, Xiao-wu

2013-07-01

330

Near-critical fluid boiling  

NASA Astrophysics Data System (ADS)

When co-existing gas and liquid phases of pure fluid are heated through their critical point, large scale density fluctuations make the fluid extremely compressible, expandable, slows the diffusive transport, and decreases the contact-angle to zero (perfect wetting by the liquid phase). We have performed experiments on near-critical fluids in weightlessness on several missions on the Mir space station using the Alice-II instrument, to suppress buoyancy driven flows and gravitational constraints on the liquid-gas interface. We have found that when the system's temperature T is increased at a constant rate past the critical temperature, TC, so that its slightly out of equilibrium, several unusual phenomena occur. The gas phase (or low density regions above TC) of the fluid gains a higher temperature than the hot wall and the wetting film on the wall shows large variations in thickness (0.023mm) that forms spatial structures. When the large gas bubble makes contact with a side-wall heating surface, it spreads on the heating surface making a large spreading angle (over 180), so that the bubble's shape is significantly changed. This last unexpected result is robust, i.e., it is observed either under continuous heating (ramping) or stepping by positive temperature quenches, for various morphologies of the gas bubble and in different fluids. We consider as possible causes of the spreading phenomenon both a surface-tension gradient, due to a temperature gradient along the interface, and the vapor recoil force, due to evaporation. It appears that the vapor recoil force has a more dominant divergence and explains qualitatively the large apparent contact angle far below TC.

Hegseth, John; Nikolayev, Vadim; Garrabos, Yves; Beysens, Daniel

2001-03-01

331

Heat Transfer Performances of Pool Boiling on Metal-Graphite Composite Surfaces  

NASA Technical Reports Server (NTRS)

Nucleate boiling, especially near the critical heat flux (CHF), can provide excellent economy along with high efficiency of heat transfer. However, the performance of nucleate boiling may deteriorate in a reduced gravity environment and the nucleate boiling usually has a potentially dangerous characteristic in CHF regime. That is, any slight overload can result in burnout of the boiling surface because the heat transfer will suddenly move into the film-boiling regime. Therefore, enhancement of nucleate boiling heat transfer becomes more important in reduced gravity environments. Enhancing nucleate boiling and critical heat flux can be reached using micro-configured metal-graphite composites as the boiling surface. Thermocapillary force induced by temperature difference between the graphite-fiber tips and the metal matrix, which is independent of gravity, will play an important role in bubble detachment. Thus boiling heat transfer performance does not deteriorate in a reduced-gravity environment. 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. Experimental studies were performed on nucleate pool boiling of pentane on cooper-graphite (Cu-Gr) and aluminum-graphite (Al-Gr) composite surfaces with various fiber volume concentrations for heat fluxes up to 35 W per square centimeter. It is revealed that a significant enhancement in boiling heat transfer performance on the composite surfaces is achieved, due to the presence of micro-graphite fibers embedded in the matrix. The onset of nucleate boiling (the isolated bubble regime) occurs at wall superheat of about 10 C for the Cu-Gr surface and 15 C for the Al-Gr surface, much lower than their respective pure metal surfaces. Transition from an isolated bubble regime to a coalesced bubble regime in boiling occurs at a superheat of about 14 C on Cu-Gr surface and 19 C on Al-Gr surface.

Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

2000-01-01

332

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

333

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

334

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

335

Effect of bubble frequency on bubble departure diameter in nucleate pool boiling  

SciTech Connect

A remarkably high heat flux can be obtained with a heat source of small temperature difference by generating a small amount of electrolytic hydrogen gas from a heating surface under nucleate boiling conditions. In order to elucidate the mechanisms involved in such a system and also in heat transfer in ordinary nucleate boiling, the diameter of escaping vapor bubble at the time of nucleate boiling under reduced pressure was investigated theoretically and experimentally. It was determined that an analytical model which considered the frequency of vapor bubble generation was able to explain relatively well the experimental values.

Nakayama, A.; Kano, M.

1983-07-01

336

Steady State Film Boiling Heat Transfer Simulated With Trace V4.160  

SciTech Connect

This paper presents the results of the assessment and analysis of TRACE v4.160 heat transfer predictions in the post-CHF (critical heat flux) region and discusses the possibilities to improve the TRACE v4.160 code predictions in the film boiling heat transfer when applying different film boiling correlations. For this purpose, the TRACE v4.160-calculated film boiling heat flux and the resulting maximum inner wall temperatures during film boiling in single tubes were compared with experimental data obtained at the Royal Institute of Technology (KTH) in Stockholm, Sweden. The experimental database included measurements for pressures ranging from 30 to 200 bar and coolant mass fluxes from 500 to 3000 kg/m{sup 2}s. It was found that TRACE v4.160 does not produce correct predictions of the film boiling heat flux, and consequently of the maximum inner wall temperature in the test section, under the wide range of conditions documented in the KTH experiments. In particular, it was found that the standard TRACE v4.160 under-predicts the film boiling heat transfer coefficient at low pressure-low mass flux and high pressure-high mass flux conditions. For most of the rest of the investigated range of parameters, TRACE v4.160 over-predicts the film boiling heat transfer coefficient, which can lead to non-conservative predictions in applications to nuclear power plant analyses. Since no satisfactory agreement with the experimental database was obtained with the standard TRACE v4.160 film boiling heat transfer correlations, we have added seven film boiling correlations to TRACE v4.160 in order to investigate the possibility to improve the code predictions for the conditions similar to the KTH tests. The film boiling correlations were selected among the most commonly used film boiling correlations found in the open literature, namely Groeneveld 5.7, Bishop (2 correlations), Tong, Konkov, Miropolskii and Groeneveld-Delorme correlations. The only correlation among the investigated, which resulted in a significant improvement of TRACE predictions, was the Groeneveld 5.7. It was found, that replacing the current film boiling correlation (Dougall-Rohsenow) for the wall-togas heat transfer with Groeneveld 5.7 improves the code predictions for the film boiling heat transfer at high qualities in single tubes in the entire range of pressure and coolant mass flux considered. (authors)

Audrius Jasiulevicius; Rafael Macian-Juan [Paul Scherrer Institute, 5232 Villigen PSI, Schweiz (Switzerland)

2006-07-01

337

Response of copper to shock-wave loading at temperatures up to the melting point  

NASA Astrophysics Data System (ADS)

The evolution of elastic-plastic shock waves as a function of the propagation distance has been studied in 99.999% purity polycrystalline copper over the 300 to 1353 K temperature range. The free surface velocity histories of shock-loaded samples 0.1 to 2.0 mm in thickness have been recorded using the velocity interferometer. The measured decay of the elastic precursor waves has been converted into relationships between the shear stress at Hugoniot elastic limit and the initial plastic strain rate. Independently of the temperature, the initial densities of mobile dislocations in a range of 2.5106 cm-2 to 5108 cm-2 are required to provide observed initial strain rates varied from 2.3103 s-1 to 2106 s-1. Above 1100 K, the shape of the elastic precursor wave changes with the appearance of a sharp spike at its front part. This change is treated in terms of nucleation and multiplication of mobile dislocations. An analysis of the rise times of the plastic shock waves has shown that for the same level of shear stress, the plastic strain rates after a 2% compressive strain increase with respect to those just behind the elastic precursor front by a factor of 300 at 300 K and by a factor of 30 at 1353 K.

Zaretsky, E. B.; Kanel, G. I.

2013-08-01

338

The relationship between point defects and mechanical properties in Fe-Al at room temperature  

SciTech Connect

The defect concentrations and mechanical properties of B2-structured Fe-Al have been investigated at room temperature as a function of Al concentration. Mechanical testing of large-grained Fe-Al alloys has shown that the yield strength decreases rapidly with small (iron-rich) deviations from the stoichiometric composition but is almost independent of composition from 40 to 45at.% Al. X-ray diffractometry was used to determine the lattice parameter, the degree of long range order, the concentration of vacancies and the fraction of lattice sites occupied by anti-site atoms. It was found that the lattice parameter increases with increasing Al concentrations for Fe-rich and stoichiometric compositions, but that the lattice parameter of Fe-51 at.% Al is almost the same as that of Fe-50 at.% Al, indicating that one Fe-Al phase boundary is around the stoichiometric composition. The anti-site atom concentrations are shown to decrease and the vacancy concentration to increase with increasing Al content. Comparisons of the anti-site atom concentration and vacancy concentration with the yield strength as a function of Al concentration suggest that vacancies control the room temperature mechanical properties.

Xiao, H.; Baker, I. (Dartmouth College, NH (United States). Thayer School of Engineering)

1995-01-01

339

Membrane lipid perturbation modifies the set point of the temperature of heat shock response in yeast.  

PubMed Central

Addition of a saturated fatty acid (SFA) induced a strong increase in heat shock (HS) mRNA transcription when cells were heat-shocked at 37 degrees C, whereas treatment with an unsaturated fatty acid (UFA) reduced or eliminated the level of HS gene transcription at 37 degrees C. Transcription of the delta 9-desaturase gene (Ole1) of Histoplasma capsulatum, whose gene product is responsible for the synthesis of UFA, is up-regulated in a temperature-sensitive strain. We show that when the L8-14C mutant of Saccharomyces cerevisiae, which has a disrupted Ole1 gene, is complemented with its own Ole1 coding region under control of its own promoter or Ole1 promoters of H. capsulatum, the level of HS gene transcription depends on the activity of the promoters. Fluorescence anisotropy of mitochondrial membranes of completed strains corresponded to the different activity of the Ole1 promoter used. We propose that the SFA/UFA ratio and perturbation of membrane lipoprotein complexes are involved in the perception of rapid temperature changes and under HS conditions disturbance of the preexisting membrane physical state causes transduction of a signal that induces transcription of HS genes. Images Fig. 1 Fig. 2 Fig. 3 Fig. 7

Carratu, L; Franceschelli, S; Pardini, C L; Kobayashi, G S; Horvath, I; Vigh, L; Maresca, B

1996-01-01

340

Forced-convective boiling in small diameter tube  

NASA Astrophysics Data System (ADS)

A straight bare tube type evaporator was tested in order to evaluate its feasibility on space applications. Two categories of flow regimes were observed during the test. One flow regime indicated a high pressure loss and a slight temperature decrease along the flow direction, and the test results showed a fairly good agreement with the analytical results obtained using a nucleat boiling model. Whereas, the other flow regime showed a contrasting feature of low pressure loss and abrupt temperature rise along the flow direction. In this case also the results obtained on the basis of the analytical model of film boiling showed a fairly good agreement with the experimental results of heat transfer characteristics.

Miyazaki, Yoshiro; Kuriyma, Yoshio; Furukawa, Masao

1988-03-01

341

Numerical analysis of contaminant removal from fractured rock during boiling  

NASA Astrophysics Data System (ADS)

A multiphase heat transfer numerical model is used to simulate a laboratory experiment of contaminant removal at boiling temperatures from a rock core representing the matrix adjacent to a fracture. The simulated temperature, condensate production, contaminant and bromide concentrations are similar to experimental data. A key observation from the experiment and simulation is that boiling out approximately 1/2 pore volume (50 mL) of water results in the removal of essentially 100% of the dissolved volatile contaminant (1,2-DCA). A field-scale simulation using the multiple interacting continua (MINC) discretization approach is conducted to illustrate possible applications of thermal remediation of fractured geologic media, assuming uniform heating. The results show that after 28% of the pore water (including both steam vapor and liquid water) was extracted, and essentially all the 1,2-DCA mass (more than 99%) was removed.

Chen, Fei; Falta, Ronald W.; Murdoch, Lawrence C.

2012-06-01

342

Numerical analysis of contaminant removal from fractured rock during boiling.  

PubMed

A multiphase heat transfer numerical model is used to simulate a laboratory experiment of contaminant removal at boiling temperatures from a rock core representing the matrix adjacent to a fracture. The simulated temperature, condensate production, contaminant and bromide concentrations are similar to experimental data. A key observation from the experiment and simulation is that boiling out approximately 1/2 pore volume (50 mL) of water results in the removal of essentially 100% of the dissolved volatile contaminant (1,2-DCA). A field-scale simulation using the multiple interacting continua (MINC) discretization approach is conducted to illustrate possible applications of thermal remediation of fractured geologic media, assuming uniform heating. The results show that after 28% of the pore water (including both steam vapor and liquid water) was extracted, and essentially all the 1,2-DCA mass (more than 99%) was removed. PMID:22579665

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

2012-06-01

343

A Nonparametric Temperature Controller With Nonlinear Negative Reaction for Multi-Point Rapid MR-Guided HIFU Ablation.  

PubMed

Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is a noninvasive method for thermal ablation, which exploits the capabilities of magnetic resonance imaging (MRI) for excellent visualization of the target and for near real-time thermometry. Oncological quality of ablation may be obtained by volumetric sonication under automatic feedback control of the temperature. For this purpose, a new nonparametric (i.e., model independent) temperature controller, using nonlinear negative reaction, was designed and evaluated for the iterated sonication of a prescribed pattern of foci. The main objective was to achieve the same thermal history at each sonication point during volumetric MRgHIFU. Differently sized linear and circular trajectories were investigated ex vivo and in vivo using a phased-array HIFU transducer. A clinical 3T MRI scanner was used and the temperature elevation was measured in five slices simultaneously with a voxel size of 1 1 5 mm(3) and temporal resolution of 4 s. In vivo results indicated a similar thermal history of each sonicated focus along the prescribed pattern, that was 17.3 0.5 () C as compared to 16 () C prescribed temperature elevation. The spatio-temporal control of the temperature also enabled meaningful comparison of various sonication patterns in terms of dosimetry and near-field safety. The thermal build-up tended to drift downwards in the HIFU transducer with a circular scan. PMID:24893259

Petrusca, Lorena; Auboiroux, Vincent; Goget, Thomas; Viallon, Magalie; Muller, Arnaud; Gross, Patrick; Becker, Christoph D; Salomir, Rares

2014-06-01

344

Handheld low-temperature plasma probe for portable "point-and-shoot" ambient ionization mass spectrometry.  

PubMed

We describe a handheld, wireless low-temperature plasma (LTP) ambient ionization source and its performance on a benchtop and a miniature mass spectrometer. The source, which is inexpensive to build and operate, is battery-powered and utilizes miniature helium cylinders or air as the discharge gas. Comparison of a conventional, large-scale LTP source against the handheld LTP source, which uses less helium and power than the large-scale version, revealed that the handheld source had similar or slightly better analytical performance. Another advantage of the handheld LTP source is the ability to quickly interrogate a gaseous, liquid, or solid sample without requiring any setup time. A small, 7.4-V Li-polymer battery is able to sustain plasma for 2 h continuously, while the miniature helium cylinder supplies gas flow for approximately 8 continuous hours. Long-distance ion transfer was achieved for distances up to 1 m. PMID:23721516

Wiley, Joshua S; Shelley, Jacob T; Cooks, R Graham

2013-07-16

345

High-freezing-point fuels used for aviation turbine engines  

NASA Technical Reports Server (NTRS)

Broadened-specification aviation fuels could be produced from a greater fraction of crude source material with improvements in fuel supply and price. These fuels, particularly those with increased final boiling temperatures, would have higher freezing temperatures than current aviation turbine fuels. The higher-freezing-point fuels can be substituted in the majority of present commercial flights, since temperature data indicate that in-flight fuel temperatures are relatively mild. For the small but significant fraction of commercial flights where low fuel temperatures make higher freezing-point fuel use unacceptable, adaptations to the fuel or fuel system may be made to accommodate this fuel. Several techniques are discussed. Fuel heating is the most promising concept. One simple system design uses existing heat rejection from the fuel-lubricating oil cooler, another uses an engine-driven generator for electrical heating. Both systems offer advantages that outweigh the obvious penalties.

Friedman, R.

1979-01-01

346

Challenging the distributed temperature sensing technique for estimating groundwater discharge to streams through controlled artificial point source experiment  

NASA Astrophysics Data System (ADS)

Spatially confined groundwater discharge can contribute significantly to stream discharge. Distributed fibre optic temperature sensing (DTS) of stream water has been successfully used to localize- and quantify groundwater discharge from this type "point sources" (PS) in small first-order streams. During periods when stream and groundwater temperatures differ PS appear as abrupt step in longitudinal stream water temperature distribution. Based on stream temperature observation up- and downstream of a point source and estimated or measured groundwater temperature the proportion of groundwater inflow to stream discharge can be quantified using simple mixing models. However so far this method has not been quantitatively verified, nor has a detailed uncertainty analysis of the method been conducted. The relative accuracy of this method is expected to decrease nonlinear with decreasing proportions of lateral inflow. Furthermore it depends on the temperature differences (?T) between groundwater and surface water and on the accuracy of temperature measurement itself. The latter could be affected by different sources of errors. For example it has been shown that a direct impact of solar radiation on fibre optic cables can lead to errors in temperature measurements in small streams due to low water depth. Considerable uncertainty might also be related to the determination of groundwater temperature through direct measurements or derived from the DTS signal. In order to directly validate the method and asses it's uncertainty we performed a set of artificial point source experiments with controlled lateral inflow rates to a natural stream. The experiments were carried out at the Vollnkirchener Bach, a small head water stream in Hessen, Germany in November and December 2011 during a low flow period. A DTS system was installed along a 1.2 km sub reach of the stream. Stream discharge was measured using a gauging flume installed directly upstream of the artificial PS. Lateral inflow was simulated using a pumping system connected to a 2 m3 water tank. Pumping rates were controlled using a magnetic inductive flowmeter and kept constant for a time period of 30 minutes to 1.5 hours depending on the simulated inflow rate. Different temperatures of lateral inflow were adjusted by heating the water in the tank (for summer experiments a cooling by ice cubes could be realized). With this setup, different proportions of lateral inflow to stream flow ranging from 2 to 20%, could be simulated for different ?T's (2-7 C) between stream- and inflowing water. Results indicate that the estimation of groundwater discharge through DTS is working properly, but that the method is very sensitive to the determination of the PS groundwater temperature. The span of adjusted ?T and inflow rates of the artificial system are currently used to perform a thorough uncertainty analysis of the DTS method and to derive thresholds for detection limits.

Lauer, F.; Frede, H.-G.; Breuer, L.

2012-04-01

347

Temperature-plant pigment-optical relations in a recurrent offshore mesoscale eddy near Point Conception, California  

NASA Technical Reports Server (NTRS)

The temperature-plant pigment-optical structure of a mesoscale anticyclonic eddy consistently found in shipboard surveys and satellite-sensed data several hundred kilometers southwest of Point Conception, CA, is described on three different time scales (100-day mesoscale, annual, and several-year). The satellite coastal zone color scanner (CZCS) ocean color imagery detected the near-surface chlorophyll structure of the eddy, but in situ optical and plant pigment data suggest that such imagery does not provide a good estimate of the integrated chlorophyll field of the eddy. The temperature and plant pigment boundaries of the eddy, as determined from two-dimensional gradients of advanced very high resolution radiometer (AVHRR) and CZCS imagery, do not coincide spatially. This and in situ temperature, plant pigment, and optical structure provide additional evidence that some eddy systems in the California Current are not isolated vortex systems but rather continuously entrain waters of nonlocal origin laterally into their upper layers. Within the California Current a ratio of AVHRR/CZCS data is useful for separating inshore from oceanic water masses and following their surface entrainment by offshore vortices. The historical 28-year California Cooperative Oceanic Fisheries Investigations data for the Point Conception region of the California Current and remotely sensed data over this region show that the Point Conception eddy is a recurrent feature in the offshore California Current. Moreover, the available data provide evidence that a large number of warm-core mesoscale eddies occur simultaneously in a transition zone between coastal and oceanic regimes, that these features recur at preferred locations within the transition zone, and that this family of eddies should impose a significant offshore boundary condition on the flow of the California Current.

Simpson, James J.; Pelaez, Jose; Haury, Loren R.; Wiesenhahn, David; Koblinsky, Chester J.

1986-01-01

348

Testing for the Gaussian nature of cosmological density perturbations through the three-point temperature correlation function  

NASA Technical Reports Server (NTRS)

One of the crucial aspects of density perturbations that are produced by the standard inflation scenario is that they are Gaussian where seeds produced by topological defects tend to be non-Gaussian. The three-point correlation function of the temperature anisotropy of the cosmic microwave background radiation (CBR) provides a sensitive test of this aspect of the primordial density field. In this paper, this function is calculated in the general context of various allowed non-Gaussian models. It is shown that the Cosmic Background Explorer and the forthcoming South Pole and balloon CBR anisotropy data may be able to provide a crucial test of the Gaussian nature of the perturbations.

Luo, Xiaochun; Schramm, David N.

1993-01-01

349

Flooded Boiling of Ammonia with Miscible Oil Outside a Horizontal Plain Tube  

Microsoft Academic Search

Pool boiling tests were conducted with plain steel tubing using pure ammonia and a mixture of ammonia and a miscible lubricant. By comparing the results, the effect of miscible lubricant on shell-side boiling heat transfer coefficient of ammonia was quantified. The experiment covered saturation temperature from ?23.3 C to 7.2C (?10 F to 45F) and heat flux up to 60

J. X. Zheng; G. P. Jin; M.-C. Chyu; Z. H. Ayub

2001-01-01

350

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

351

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

352

Modeling and analysis of low heat flux natural convection sodium boiling in LMFBRs  

SciTech Connect

Flow excursion induced dryout at low heat flux natural convection boiling, typical of liquid metal fast breeder reactor, is addressed. Steady state calculations indicate that low quality boiling is possible up to the point of Ledinegg instability leading to flow excursion and subsequent dryout in agreement with experimental data. A flow regime-dependent dryout heat flux relationship based upon saturated boiling criterion is also presented. Transient analysis indicates that premature flow excursion can not be ruled out and sodium boiling is highly transient dependent. Analysis of a high heat flux forced convection, loss-of-flow transient shows a significantly faster flow excursion leading to dryout in excellent agreement with parallel calculations using the two-dimensional THORAX code. 31 refs., 25 figs., 6 tabs.

Khatib-Rahbar, M.; Cazzoli, E.G.

1982-09-01

353

Flow excursion-induced dryout at low heat flux natural convection boiling  

SciTech Connect

Flow excursion-induced dryout at low heat flux natural convection boiling, typical of liquid metal fast breeder reactors, is addressed. Steady-state calculations indicate that low-quality boiling is possible up to the point of the Ledinegg instability, leading to flow excursion and subsequent dryout in agreement with experimental data. A flow regime -dependent critical heat flux relationship based upon a saturated boiling criterion is also presented. Transient analyses indicate that premature flow excursion cannot be ruled out and the boiling process is transient dependent. Analysis of a loss-of-flow transient at high heat flux forced convection shows a significantly faster flow excursion leading to dryout, which is in excellent agreement with the results of the two-dimensional THORAX code.

Khatib-Rahbar, M.; Cazzoli, E.G.

1986-05-01

354

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

355

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

356

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

357

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

358

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

359

The advanced high-temperature reactor: High-temperature fuel, liquid salt coolant, liquid-metal-reactor plant  

Microsoft Academic Search

The Advanced High-Temperature Reactor is a new reactor concept that combines four existing technologies in a new way: (1) coated-particle graphite-matrix nuclear fuels (traditionally used for helium-cooled reactors), (2) Brayton power cycles, (3) passive safety systems and plant designs from liquid-metal-cooled fast reactors, and (4) low-pressure liquid-salt coolants with boiling points far above the maximum coolant temperature. The new combination

Charles Forsberg

2005-01-01

360

Our Educational Melting Pot: Have We Reached the Boiling Point?  

ERIC Educational Resources Information Center

The articles and excerpts in this collection illustrate the complexity of the melting pot concept. Multiculturalism has become a watchword in American life and education, but it may be that in trying to atone for past transgressions educators and others are simply going too far. These essays illustrate some of the problems of a multicultural

Lauderdale, Katherine Lynn, Ed.; Bonilla, Carlos A., Ed.

361

On the Boiling Points of the Alkyl Halides.  

ERIC Educational Resources Information Center

Discusses the variety of explanations in organic chemistry textbooks of a physical property of organic compounds. Focuses on those concepts explaining attractive forces between molecules. Concludes that induction interactions play a major role in alkyl halides and other polar organic molecules and should be given wider exposure in chemistry texts.

Correia, John

1988-01-01

362

Predictive Models for the Velocity of Sound in Liquid Metallic Elements at Their Melting-Point Temperatures  

NASA Astrophysics Data System (ADS)

Nowadays, accurate and reliable data for the thermophysical properties of almost all liquid metallic elements are indispensable in the field of materials process science ( e.g., for computer simulation studies of the fluid flow in a vessel or the solidification of a metallic element). The dimensionless common parameters (denoted by ? {/E 1/2} and ? {/T 1/2}), extracted from the velocity of sound, provide for better predictions of the thermophysical properties of liquid metallic elements such as surface tension, viscosity, self-diffusion, thermal expansion, and evaporation enthalpy, because these two parameters characterize the state of the liquid metallic atom ( i.e., an atoms hardness or softness and its anharmonic motions). The usefulness of reliable predictive models in many engineering situations is clear; in the field of materials process science and engineering, both accuracy and universality are required of any model for predicting the thermophysical properties of liquid metallic elements. In view of the accuracy and universality of a model, predictive models for the velocity of sound in liquid metallic elements at their melting-point temperatures were investigated; the performances of several models were evaluated by comparing experimental values for the melting-point sound velocity in various liquid metallic elements with those calculated from these models, using a relative standard deviation as a yardstick. Of these, two simple models in terms of well-known physical quantities, presented by the authors, give very good agreement with the experimental data. Excluding only a few metals, calculated sound-velocity values fall, or almost fall, within the range of uncertainties associated with experimental measurements of high-melting-point or reactive metals. It can safely be said that the two models for melting-point sound velocity in liquid metallic elements are endowed with the necessary conditions of being predictive.

Iida, Takamichi; Guthrie, Roderick

2009-12-01

363

A New Theory of Nucleate Pool Boiling in Arbitrary Gravity  

NASA Technical Reports Server (NTRS)

Heat transfer rates specific to nucleate pool boiling under various conditions are determined by the dynamics of vapour bubbles that are originated and grow at nucleation sites of a superheated surface. A new dynamic theory of these bubbles has been recently developed on the basis of the thermodynamics of irreversible processes. In contrast to other existing models based on empirically postulated equations for bubble growth and motion, this theory does not contain unwarrantable assumptions, and both the equations are rigorously derived within the framework of a unified approach. The conclusions of the theory are drastically different from those of the conventional models. The bubbles are shown to detach themselves under combined action of buoyancy and a surface tension force that is proven to add to buoyancy in bubble detachment, but not the other way round as is commonly presumed. The theory ensures a sound understanding of a number of so far unexplained phenomena, such as effect caused by gravity level and surface tension on the bubble growth rate and dependence of the bubble characteristics at detachment on the liquid thermophysical parameters and relevant temperature differences. The theoretical predictions are shown to be in a satisfactory qualitative and quantitative agreement with observations. When being applied to heat transfer at nucleate pool boiling, this bubble dynamic theory offers an opportunity to considerably improve the main formulae that are generally used to correlate experimental findings and to design boiling heat removal in various industrial applications. Moreover, the theory makes possible to pose and study a great deal of new problems of essential impact in practice. Two such problems are considered in detail. One problem concerns the development of a principally novel physical model for the first crisis of boiling. This model allows for evaluating critical boiling heat fluxes under various conditions, and in particular at different gravity levels, with a good agreement with experimental evidence. The other problem bears upon equilibrium shapes of a detached bubble near a heated surface in exceedingly low gravity. In low gravity or in weightlessness, the bubble can remain in the close vicinity of the surface for a long time, and its shape is greatly affected by the Marangoni effect due to both temperature and possible surfactant concentration being nonuniform along the interface. The bubble performs at these conditions like a heat pipe, with evaporation at the bubble lower boundary and condensation at its upper boundary, and ultimately ensures a substantial increase in heat removal as compared with that in normal gravity. Some other problems relevant to nucleate pool and forced convection boiling heat transfer are also discussed.

Buyevich, Y. A.; Webbon, Bruce W.

1995-01-01

364

Synthesis and physical properties of novel perfluorinated methylene oxide oligomers. The ultimate low temperature fluids  

SciTech Connect

Perfluorinated polyethers are a class of substances which are extremely inert and have both extraordinary high temperature stability and low temperature properties. The synthesis of perfluorinated polyformaldehydes with the highest oxygen content was designed to give the maximum liquid range and low temperature properties. Novel low molecular weight perfluorinated polyformaldehydes with stable and unreactive perfluoro-n-butyl end groups were prepared by liquid-phase direct fluorination. The boiling point of these compounds increases by approximately 20{degree}C with the addition of each difluoromethylene oxide unit. This trend does not continue for longer chain lengths (n > 4) where the increase in boiling point per CF{sub 2}O unit diminishes. The average increase of melting temperature is approximately 1-2{degree}C as the perfluorinated polyformaldehyde chain increases one difluoromethylene oxide unit. The new perfluoropolyether fluids produced have melting points ranging from -145 to -152{degree}C. 33 refs., 3 tabs.

Sung, K.; Lagow, R.J. [Univ. of Texas, Austin, TX (United States)

1995-04-19

365

Zero Boil Off Cryogen Storage for Future Launchers  

NASA Technical Reports Server (NTRS)

Zero boil off (ZBO) cryogen storage using both cryocoolers and passive insulation technologies will enable long-term exploration missions by allowing designers to optimize tankage without the need for excess cryogen storage to account for boil off. Studies of ZBO (zero boil off) have been on-going in the USA for several years. More recently, a review of the needs of advanced space propulsion took place in Europe. This showed the interest of the European community in cryogenic propulsion for planetary missions as well as the use of liquid hydrogen for large power electric propulsion (manned Mars missions). Although natural boiling could be acceptable for single leg missions, passive insulation techniques yield roughly a I% per month cryogen loss and this would not be cost effective for robotic planetary missions involving storage times greater than one year. To make economic sense, long-term exploration missions require lower tank capacity and longer storage times. Recent advances in cryocooler technology, resulting in vast improvements in both cooler efficiency and reliability, make ZBO is a clear choice for planetary exploration missions. Other, more near term applications of ZBO include boil-off reduction or elimination applied to first and upper stages of future earth-to-orbit (ETO) launchers. This would extend launch windows and reduce infrastructure costs. Successors to vehicles like Ariane 5 could greatly benefit by implementing ZBO. Zero Boil Off will only be successful in ETO launcher applications if it makes economic sense to implement. The energy cost is only a fraction of the total cost of buying liquid cryogen, the rest being transportation and other overhead. Because of this, higher boiling point cryogens will benefit more from on-board liquefaction, thus reducing the infrastructure costs. Since hydrogen requires a liquefier with at least a 17% efficiency just to break even from a cost standpoint, one approach for implementing ZBO in upper stages would be to actively cool the shield in the hydrogen tank to reduce the parasitic losses. This would allow the use of less expensive, presently available coolers (80 K vs. 20 K) and potentially simplify the system by requiring only a single compressor on the pad amd a single disconnect line. The compressor could be a hefty commercial unit, with only the cold head requiring expensive flight development and qualification. While this is actually a reduced boil off configuration rather than a zero-boil off case, if the cryogen loss could be cut significantly, the increase in hold time and reduced need for draining and refilling the propellant tanks could meet the vehicle operations needs in the majority of instances.Bearing in mind the potential benefits of ZBO, NASA AMES and SNECMA Moteurs decided to exchange their technical views on the subject. This paper will present a preliminary analysis for a multi-mission module using a fairly low thrust cryogenic engine and ZBO during cruise. Initial mass is 5.5. tons (in ETO). The cryogenic engine will be used near each periapsis in order to minimize the AV requirement. The payload obtained by this propulsion system is compared to a classical storable bipropellant propulsion system for several cases (e. g. Mars lander, Jupiter orbiter, Saturn orbiter). For the Jupiter and Saturn cases, the power source could be an RTG or a large parabolic mirror illuminating a solar panel. It is shown -that - due to its much larger specific impulse - the cryogenic ZBO solution provides much higher payloads, especially for exploration missions involving landing on planets, asteroids, comets, or other celestial bodies.

Valentian, D.; Plachta, D.; Kittel, P.; Hastings, L. J.; Salerno, Louis J.; Arnold, James O. (Technical Monitor)

2001-01-01

366

Communication: High speed optical investigations of a character of boiling-up onset  

NASA Astrophysics Data System (ADS)

In this communication, we discuss the phenomenon of attainable superheat of liquid and the peculiarities of its release by spontaneous boiling-up. We have combined the apparatus for superheating, namely, bubble chamber, with a high speed micro-optical method for detailed monitoring of the initial stage of boiling-up. In experiments on the isothermal pressure drop, it was found that the boiling-up onset of n-hexane is accompanied by characteristic step signal. The signal has proved to be typical of the heterogeneous character of boiling-up onset in a whole range of superheating degrees. The performance of the method for investigation of the refractive index and density for superheated liquids as functions of temperature and pressure has been revealed. The experimental error is estimated to be 0.1%.

Gurashkin, A. L.; Starostin, A. A.; Ermakov, G. V.; Skripov, P. V.

2012-01-01

367

Experimental study on microscopic evolving process of boiling overheat liquor in boiler under microcracking condition  

NASA Astrophysics Data System (ADS)

Boilers are frequently used in agricultural engineering. After micro cracks appear on the wall of the boiler for high pressure saturated liquor, the containing liquid will be overheated, rapidly boiled and expanded, which may result in explosion of the whole container. The evolving processes differ greatly by cracking conditions. In the experiment conducted in the this article, we made a small sized experimental device and applied high speed photography technology observing the simulated fierce boiling process of the high temperature and high pressure saturated water under overheat condition when micro cracking appears on boiler wall. According to our study, lower depressurization rate will suppress the boiling intensity of the overheated liquid and slow the growth of bubbles, decelerating the expansion of the two-phase flow compared with the boiling liquid expanding vapor explosion. The magnitude of overpressure in the container is also relatively smaller than overpressure in BLEVE.

Chen, Sining; He, Xuechao; Sun, Jinhua

2009-07-01

368

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

369

Pool boiling heat transfer on thin wire in nitrogen-tetrafluoromethane mixtures  

SciTech Connect

Nucleate and film pool boiling heat transfer, critical heat fluxes, and minimum heat fluxes for nitrogen, tetrafluoromethane, and their mixtures were measured on a thin wire. The orientation of the wire was either horizontal or vertical. Critical heat fluxes and minimum heat fluxes for the mixtures in any concentration were larger than those for liquid nitrogen. The heat flux in nucleate boiling regimes for mixtures was represented well by an experimental formula. For a single-component liquid, transition from nucleate boiling to film boiling was observed for a stepwise heat input and rapid heating. It was found that there was no such transition for mixtures in contrast to the pure component. The nitrogen-tetrafluoromethane mixtures are recommended for use as cryogens of oxide superconductors having critical temperature higher than 110 K.

Amano, Toshiyuki

1993-09-01

370

Solubility of Fullerene C60 and C70 in Toluene, o-Xylene and Carbon Disulfide at Various Temperatures  

Microsoft Academic Search

The solubilities of fullerene C60 and C70 in toluene, o-xylene and carbon disulfide between the melting point and boiling point of the solvents, respectively, have been measured. The temperature dependent solubility of C60 displays anomalous behaviors. A solubility maximum of C60 around 0 C for toluene and carbon sulfide and around 30 C for o-xylene was observed. The temperature-dependent solubility

Xflroang Zhou; Jianben Liu; Zhaoxia Jin; Zhennan Gu; Yongqing Wu; Yiliang Sun

1997-01-01

371

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

372

Thermal conductivity measurements of single-crystalline bismuth nanowires by the four-point-probe 3-? technique at low temperatures.  

PubMed

We have successfully investigated the thermal conductivity (?) of single-crystalline bismuth nanowires (BiNWs) with [110] growth direction, via a straightforward and powerful four-point-probe 3-? technique in the temperature range 10-280 K. The BiNWs, which are well known as the most effective material for thermoelectric (TE) device applications, were synthesized by compressive thermal stress on a SiO2/Si substrate at 250-270 C for 10 h. To understand the thermal transport mechanism of BiNWs, we present three kinds of experimental technique as follows, (i) a manipulation of a single BiNW by an Omni-probe in a focused ion beam (FIB), (ii) a suspended bridge structure integrating a four-point-probe chip by micro-fabrication to minimize the thermal loss to the substrate, and (iii) a simple 3-? technique system setup. We found that the thermal transport of BiNWs is highly affected by boundary scattering of both phonons and electrons as the dominant heat carriers. The thermal conductivity of a single BiNW (d ~ 123 nm) was estimated to be ~2.9 W m(-1) K(-1) at 280 K, implying lower values compared to the thermal conductivity of the bulk (~11 W m(-1) K(-1) at 280 K). It was noted that this reduction in the thermal conductivity of the BiNWs could be due to strongly enhanced phonon-boundary scattering at the surface of the BiNWs. Furthermore, we present temperature-dependent (10-280 K) thermal conductivity of the BiNWs using the 3-? technique. PMID:23575254

Lee, Seung-Yong; Kim, Gil-Sung; Lee, Mi-Ri; Lim, Hyuneui; Kim, Wan-Doo; Lee, Sang-Kwon

2013-05-10

373

Induction heating pure vapor source of high temperature melting point materials on electron cyclotron resonance ion source  

SciTech Connect

Multicharged ions that are needed are produced from solid pure material with high melting point in an electron cyclotron resonance ion source. We develop an evaporator by using induction heating (IH) with multilayer induction coil, which is made from bare molybdenum or tungsten wire without water cooling and surrounding the pure vaporized material. We optimize the shapes of induction coil and vaporized materials and operation of rf power supply. We conduct experiment to investigate the reproducibility and stability in the operation and heating efficiency. IH evaporator produces pure material vapor because materials directly heated by eddy currents have no contact with insulated materials, which are usually impurity gas sources. The power and the frequency of the induction currents range from 100 to 900 W and from 48 to 23 kHz, respectively. The working pressure is about 10{sup -4}-10{sup -3} Pa. We measure the temperature of the vaporized materials with different shapes, and compare them with the result of modeling. We estimate the efficiency of the IH vapor source. We are aiming at the evaporator's higher melting point material than that of iron.

Kutsumi, Osamu; Kato, Yushi; Matsui, Yuuki; Sato, Fuminobu; Iida, Toshiyuki [Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871 (Japan); Kitagawa, Atsushi; Muramatsu, Masayuki [National Institute of Radiological Science (NRIS), 4-9-1 Anagawa, Inage, Chiba 263-8555 (Japan); Uchida, Takashi; Yoshida, Yoshikazu [Bio-Nano Electronics Research Centre, Toyo University, 2100 Kujirai, Kawagoe, Saitama 350-8585 (Japan)

2010-02-15

374

Induction heating pure vapor source of high temperature melting point materials on electron cyclotron resonance ion source.  

PubMed

Multicharged ions that are needed are produced from solid pure material with high melting point in an electron cyclotron resonance ion source. We develop an evaporator by using induction heating (IH) with multilayer induction coil, which is made from bare molybdenum or tungsten wire without water cooling and surrounding the pure vaporized material. We optimize the shapes of induction coil and vaporized materials and operation of rf power supply. We conduct experiment to investigate the reproducibility and stability in the operation and heating efficiency. IH evaporator produces pure material vapor because materials directly heated by eddy currents have no contact with insulated materials, which are usually impurity gas sources. The power and the frequency of the induction currents range from 100 to 900 W and from 48 to 23 kHz, respectively. The working pressure is about 10(-4)-10(-3) Pa. We measure the temperature of the vaporized materials with different shapes, and compare them with the result of modeling. We estimate the efficiency of the IH vapor source. We are aiming at the evaporator's higher melting point material than that of iron. PMID:20192343

Kutsumi, Osamu; Kato, Yushi; Matsui, Yuuki; Kitagawa, Atsushi; Muramatsu, Masayuki; Uchida, Takashi; Yoshida, Yoshikazu; Sato, Fuminobu; Iida, Toshiyuki

2010-02-01

375

Increasing Precision Of Temperature Sensors Of Liquid H2  

NASA Technical Reports Server (NTRS)

Commercial silicon-diode temperature sensors intended for use in boiling or nearly boiling liquid hydrogen at temperatures near 37 degrees R recalibrated to greater precision by method involving careful attention to details of design, operation, and computation. Method based on fundamental electrical and thermodynamic principles and good engineering practice, also applicable to recalibration of other temperature sensors intended for use in other boiling or nearly boiling liquids.

Dempsey, Paula J.; Fabik, Richard H.

1995-01-01

376

Influence of the ambient temperature during heat pipe manufacturing on its function and heat transport ability  

NASA Astrophysics Data System (ADS)

Heat pipe is heat transfer device working at a minimum temperature difference of evaporator and condenser. Operating temperature of the heat pipe determine by properties of the working substance and pressure achieved during production. The contribution is focused on the determining the effect of the initial surrounding temperature where the heat pipe is manufactured and on the obtaining performance characteristics produced heat pipes in dependence of manufacturing temperature. Generally hold, that the boiling point of the working liquid decrease with decreasing ambient pressure. Based on this can be suppose that producing of lower ambient temperature during heat pipe manufacturing, will create the lower pressure, the boiling point of the working fluid will lower too and the heat pipe should be better performance characteristics.

?aja, A.; Nemec, P.; Malcho, M.

2014-03-01

377

APPLICATION OF SELF-CALIBRATING THERMOCOUPLES WITH MINIATURE FIXED-POINT CELLS IN A TEMPERATURE RANGE FROM 500 C TO 650 C IN STEAM GENERATORS  

Microsoft Academic Search

Using integrated miniature fixed-point cells, a measuring uncertainty of < 1 K can be reached under operat- ing condi tions in the superheated steam range of power plants by a periodic recalibration of the thermocouples, with operating times of > 20000 h. The fixed-point materials used for a temperature range from 500 o C to 650 o C are techni-

Frank Bernhard; Dirk Boguhn; Silke Augustin; Helge Mammen; Andrej Donin

2003-01-01

378

New Method of Filling of High-Temperature Fixed-Point Cells Based on Metal-Carbon Eutectics/Peritectics  

NASA Astrophysics Data System (ADS)

A new method of filling of high-temperature fixed-point cells based on metal-carbon eutectics and peritectics is suggested and tested. In this method a metal and carbon powder mixture is introduced not directly into the crucible, but into an additional container located just above the crucible. The mixture melts inside the container, and the already molten eutectic drops through a small hole in the bottom of the container and fills the crucible drop by drop. The method can be used to obtain a uniform ingot without porous or foundry cavities, to minimize the risk of contamination, and to avoid some other disadvantages. The method was applied to fabricate Re-C and WC-C cells using 5N purity materials. The cells demonstrated a good plateau shape with melting ranges of 0.2 K and 80 mK for Re-C and WC-C, respectively. The Re-C cell was compared with a cell built at NMIJ and showed good agreement with a difference of melting temperatures of only 45 mK.

Khlevnoy, B. B.; Grigoryeva, I. A.; Ibragimov, N. A.

2011-08-01

379

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

380

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

381

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...

382

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

383

A Study of Nucleate Boiling with Forced Convection in Microgravity  

NASA Technical Reports Server (NTRS)

Boiling is a rather imprecise term applied to the process of evaporation in which the rate of liquid-vapor phase change is large. In seeking to determine the role and significance of body forces on the process, of which buoyancy or gravity is just one agent, it becomes necessary to define the term more precisely. It is generally characterized by the formation and growth of individual vapor bubbles arising from heat transfer to the liquid, either at a solid/liquid or liquid/liquid interface, or volumetrically. The terms 'bubble' boiling and 'nucleate' boiling are frequently used, in recognition of the interactions of surface tension and other forces in producing discrete bubbles at distinctive locations (although not always). Primary considerations are that evaporation can occur only at existing liquid-vapor interfaces, so that attention must be given to the formation of an interface (the nucleation process), and that the latent heat for this evaporation can come only from the superheated liquid, so that attention must also be given to the temperature distributions in the liquid.

Merte, Herman, Jr.

1996-01-01

384

Effects of Temperature and pH on Reduction of Bacteria in a Point-of-Use Drinking Water Treatment Product for Emergency Relief  

PubMed Central

The effects of temperature and pH on the water treatment performance of a point-of-use (POU) coagulant/disinfectant product were evaluated. Cold temperatures (?5C) reduced the bactericidal efficiency of the product with regard to Escherichia coli and total coliform log10 reductions.

Marois-Fiset, Jean-Thomas; Carabin, Anne; Lavoie, Audrey

2013-01-01

385

Variable and fixed-point blackbody sources developed at VNIIOFI for precision measurements in radiometry and thermometry within 100K-3500K temperature range  

Microsoft Academic Search

The demands of modern radiation thermometry and radiometry are being satisfied by a large variety of high-precision unique BB sources (both fixed-point and variable temperature) designed for a wide range of temperature from 100 K to 3500 K. The paper contains a detailed review of low-, medium- and high-temperature precision blackbodies developed at VNIIOFI as the basis of the spectral

V. I. Sapritsky; B. B. Khlevnoy; S. A. Ogarev; V. E. Privalsky; M. L. Samoylov; M. K. Sakharov; A. A. Bourdakin; A. S. Panfilov

2006-01-01

386

Design, Construction, and Qualification of a Microscale Heater Array for Use in Boiling Heat Transfer  

NASA Technical Reports Server (NTRS)

Boiling heat transfer is an efficient means of heat transfer because a large amount of heat can be removed from a surface using a relatively small temperature difference between the surface and the bulk liquid. However, the mechanisms that govern boiling heat transfer are not well understood. Measurements of wall temperature and heat flux near the wall would add to the database of knowledge which is necessary to understand the mechanisms of nucleate boiling. A heater array has been developed which contains 96 heater elements within a 2.5 mm square area. The temperature of each heater element is held constant by an electronic control system similar to a hot-wire anemometer. The voltage that is being applied to each heater element can be measured and digitized using a high-speed A/D converter, and this digital information can be compiled into a series of heat-flux maps. Information for up to 10,000 heat flux maps can be obtained each second. The heater control system, the A/D system and the heater array construction are described in detail. Results are presented which show that this is an effective method of measuring the local heat flux during nucleate and transition boiling. Heat flux maps are obtained for pool boiling in FC-72 on a horizontal surface. Local heat flux variations are shown to be three to six times larger than variations in the spatially averaged heat flux.

Rule, T. D.; Kim, J.; Kalkur, T. S.

1998-01-01

387

Characteristics of Pool Boiling on Graphite-Copper Composite Surfaces  

NASA Technical Reports Server (NTRS)

Nucleate pool boiling performance of different liquids on graphite-copper composite (Gr-Cu) surfaces has been experimentally studied and modeled. Both highly wetting fluids, such as freon-113 and pentane, and a moderately wetting fluid (water) were tested on the Gr-Cu surfaces with different graphite-fiber volume fractions to reveal the enhancement effects of the composite surfaces on the nucleate pool boiling. Results of the experiments show that the graphite-fiber volume fraction has an optimum value. The Gr-Cu composite surface with 25 percent graphite-fiber volume (f=0.25) has a maximum enhancement effect on the nucleate boiling heat transfer comparing to the pure copper surface. For the highly wetting fluid, the nucleate boiling heat transfer is generally enhanced on the Gr- Cu composite surfaces by 3 to 6 times shown. In the low heat flux region, the enhancement is over 6 times, but in the high heat flux region, the enhancement is reduced to about 40%. For the moderately wetting fluid (water), stronger enhancement of nucleate boiling heat transfer is achieved on the composite surface. It shown the experimental results in which one observes the nucleate boiling heat transfer enhancement of 5 to 10 times in the low heat flux region and an enhancement of 3 to 5 times in the high heat flux region. Photographs of bubble departure during the initial stage of nucleate boiling indicate that the bubbles detached from the composite surface are much smaller in diameter than those detached from the pure copper surface. Typical photographs are presented.It shows that the bubbles departed from the composite surface have diameters of only O(0.1) mm, while those departed from the pure copper surface have diameters of O(1) mm. It is also found that the bubbles depart from the composite surface at a much higher frequency, thus forming vapor columns. These two phenomena combined with high thermal conductivity of the graphite fiber are considered the mechanisms for such a significant augmentation in nucleate boiling heat transfer on the composite surfaces. A physical model is developed to describe the phenomenon of bubble departure from the composite surface: The preferred site of bubble nucleation is the fiber tip because of higher tip temperature than the surrounding copper base and poor wettability of the graphite tip compared with that of the base material (copper). The high evaporation rate near the contact line produces the vapor cutback due to the vapor recoil pushing the three-phase line outwards from the fiber tip, and so a neck of the bubble is formed near the bubble bottom. Evaporation and surface tension accelerate the necking process and finally result in the bubble departure while a new small bubble is formed at the tip when the surface tension pushes the three-phase line back to the tip. The process is schematically shown. The proposed model is based on and confirmed by experimental results.

Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

2002-01-01

388

A statistical technique for the investigation of weak points and degradation of high-temperature superconductor tapes  

NASA Astrophysics Data System (ADS)

Recent technological developments in manufacturing high-temperature superconductor (HTSC) tapes have improved their mechanical and electrical performances considerably. Now, a near future when HTSC cables will become a reality can finally be forecast. This brings about the need for work in the field of quality control and diagnostics of HTSC tapes. A new methodology for the analysis of the behaviour of tapes aged under different kinds of mechanical stresses is presented in this paper. The methodology is based on a probabilistic approach, where the two-parameter Weibull function is used to fit the cumulative and density probability distributions obtained from experimental V-I characteristics by numerical-analytical differentiation. Experimental results relevant to both long-term (aging) and short-term tests performed on 2223-BSCCO tapes are presented and discussed. It is shown that the time behaviour of Weibull function parameters provides useful information on the level of aging and on the kind of damage occurring to the tapes. In particular, the comparison between the results obtained from long-term and short-term tests, as well as from different types of mechanical stresses, points out that the shape of probability distributions constitutes a valuable diagnostic tool to distinguish between local or overall degradation and helps in identifying damage location.

Montanari, G. C.; Ghinello, I.; Gherardi, L.; Caracino, P.; Mele, R.

1998-05-01

389

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

390

The influence of bubble evolution on the early characteristics of the boiling liquid expanding vapor explosion  

Microsoft Academic Search

In the study of boiling liquid expanding vapor explosion (BLEVE), the critical point to interpret the mechanism of the disaster is to analyze the phase transition of the superheated liquid in the container and the motions of the medium during the first several or several tens of milliseconds after the explosion from the microscopic angle of view. In the study

Sining Chen; Xuechao He; Jinhua Sun

2008-01-01

391

Chart correlation for saturated boiling heat transfer: Equations and further study  

Microsoft Academic Search

In 1976, the author presented in graphical form a general correlation named CHAPT for the estimation of heat transfer coefficients during saturated boiling at subcritical heat flux in tubes and annuli. It was compared to 780 data points from 19 independent experimental studies and found to have a mean deviation of 14% using data that included eight fluids and a

Shah

1982-01-01

392

Results of the DF-4 BWR (boiling water reactor) control blade-channel box test  

SciTech Connect

The DF-4 in-pile fuel damage experiment investigated the behavior of boiling water reactor (BWR) fuel canisters and control blades in the high temperature environment of an unrecovered reactor accident. This experiment, which was carried out in the Annular Core Research Reactor (ACRR) at Sandia National Laboratories, was performed under the USNRC's internationally sponsored severe fuel damage (SFD) program. The DF-4 test is described herein and results from the experiment are presented. Important findings from the DF-4 test include the low temperature melting of the stainless steel control blade caused by reaction with the B{sub 4}C, and the subsequent low temperature attack of the Zr-4 channel box by the relocating molten blade components. Hydrogen generation was found to continue throughout the experiment, diminishing slightly following the relocation of molten oxidizing zircaloy to the lower extreme of the test bundle. A large blockage which was formed from this material continued to oxidize while steam was being fed into the the test bundle. The results of this test have provided information on the initial stages of core melt progression in BWR geometry involving the heatup and cladding oxidation stages of a severe accident and terminating at the point of melting and relocation of the metallic core components. The information is useful in modeling melt progression in BWR core geometry, and provides engineering insight into the key phenomena controlling these processes. 12 refs., 12 figs.

Gauntt, R.O.; Gasser, R.D.

1990-10-01

393

Enhancement of nucleate pool boiling heat transfer to dilute binary mixtures using endothermic chemical reactions around the smoothed horizontal cylinder  

NASA Astrophysics Data System (ADS)

Experimental studies on enhancing the pool boiling heat transfer coefficient of binary dilute mixtures of water/glycerol, water/MEG (Mono-ethylene glycol) and water/DEG (di-ethylene glycol) have been carried out. Some particular endothermic chemical reactions related to ammonium salts were used to enhance the pool boiling heat transfer coefficient, simultaneously with occurrence of pool boiling heat transfer. Accordingly, 100 g of Ammonium nitrate, ammonium perborate and Ammonium sulfate were selected to dissolve into mixtures. High and extreme solution enthalpies of each of these ammonium salt powders are employed to reduce the surface temperature around the horizontal cylinder locally. Results demonstrated that presence of ammonium salts into the mixtures deteriorates the surface temperature of cylinder and as the result, higher pool boiling heat transfer coefficient is reported for tested solutions. Results are also reported and compared for different ammonium salts to find the influence of inducing different enthalpies of solution on pool boiling heat transfer coefficient. Obtained results also indicated that presence of endothermic reaction besides the pool boiling heat transfer enhances the heat transfer coefficients in comparison with nucleate pool boiling phenomenon solely.

Sarafraz, M. M.; Peyghambarzadeh, S. M.; Alavifazel, S. A.

2012-10-01

394

The effect of surface gas injection on film boiling heat transfer  

SciTech Connect

A database was developed for heat transfer from a horizontal plate with both film boiling and gas jetting occurring simultaneously, in a pool of water maintained at its saturation temperature. The effect of passing nitrogen through established film boiling is to increase the heat transfer from that surface. At the highest superficial gas velocity measured, approximately 8.5 cm/s, and for a constant surface temperature, the heat transfer increases by a factor of two over the heat transfer with no enhancement by gas flux. Further, as the superficial gas velocity approached zero, the data approach the stable film boiling asymptote. A semi-empirical model was developed and correlated to the database. The result is an equation which represents better than 90% of all the measured data within {plus_minus}15% bounds.

Duignan, M.R. [Westinghouse Savannah River Co., Aiken, SC (United States); Greene, G.A. [Brookhaven National Lab., Upton, NY (United States); Irvine, T.F. Jr. [State Univ. of New York, Stony Brook, NY (United States)

1991-12-31

395

Boiling-up of superheated water and water solutions under ultrasound influence  

NASA Astrophysics Data System (ADS)

Boiling-up kinetics of superheated distilled water and sodium chloride solution in a glass cell at atmospheric pressure and low superheating of 15-35 C has been studied far from the boundary of attainable superheating in the area of heterogeneous nucleation. Temperature dependences of average waiting time of superheated liquids boiling-up have been studied experimentally under natural conditions and in the ultrasonic field Waiting time of boiling-up at these temperatures reaches 1000 s, and average time is 600 s. Empirical distribution functions have been found with the use of the waiting time samples obtained by the method of order statistics. Omega-square goodness-of-fit test has shown that they disagree with exponential distribution describing stationary random process of supercritical embryo generation separating the system to macroscopic phases. Thus, it is shown that this random process is not stationary, consequently, nucleation rate to be depending on time.

Perminov, S. A.; Ermakov, G. V.

2010-03-01

396

Fluids and parameters optimization for a novel cogeneration system driven by low-temperature geothermal sources  

Microsoft Academic Search

A novel cogeneration system was proposed and techno-economically investigated, consisting of a low-temperature geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger subsystem and a heat pump subsystem. The main purpose is to identify suitable working fluids (among 27 fluids with boiling point temperature ranging from ?47.69 to 47.59C) and optimized cycle parameters for the ORC-based power generation subsystem.

T. Guo; H. X. Wang; S. J. Zhang

2011-01-01

397

The characteristics of super-elastic Ni-Ti wires in three-point bending. Part I: The effect of temperature.  

PubMed

The load-deflection behaviour of a number of commercially available superalloy nickel-titanium orthodontic wires has been examined in three-point bending over the temperature range 5-50 degrees C. The loading and unloading curves and plateau regions are found to be closely related to temperature with the stiffness decreasing quite dramatically over a narrow temperature range. The position of this range depends on the material being tested as there are marked differences due to the differing processing methods of the manufacturer. Force values at mouth temperature can differ by 600 per cent for wires of the same nominal diameter made by different manufacturers. PMID:7805815

Tonner, R I; Waters, N E

1994-10-01

398

The influence of oil on nucleate pool boiling heat transfer  

NASA Astrophysics Data System (ADS)

The influence of various oil contents in R134a is investigated for nucleate pool boiling on copper tubes either sandblasted or with enhanced heating surfaces (GEWA-B tube). Polyolester oils (POE) (Reniso Triton) with medium viscosity 55 cSt (SE55) and high viscosity 170 cSt (SE170) were used. Heat transfer coefficients were obtained for boiling temperatures between -28.6 and +20.1C. The oil content varied from 0 to 5% mass fraction. For the sandblasted tube and the SE55 oil the heat transfer coefficients for the refrigerant/oil-mixture can be higher or lower than those for the pure refrigerant, depending on oil mass fraction, boiling temperature and heat flux. In some cases the highest heat transfer coefficients were obtained at a mass fraction of 3%. For the 170 cSt oil there is a clear decrease in heat transfer for all variations except for a heat flux 4,000 W/m2 and -10.1C at 0.5% oil content. The heat transfer coefficients are compared to those in the literature for a smooth stainless steel tube and a platinum wire. For the enhanced tube and 55 cSt oil the heat transfer coefficients are clearly below those for pure refrigerant in all cases. The experimental results for the sandblasted tube are compared with the correlation by Jensen and Jackman. The calculated values are within +20 and -40% for the medium viscosity oil and between +50% and -40% for the high viscosity oil. A correlation for predicting oil-degradation effects on enhanced surfaces does not exist.

Spindler, Klaus; Hahne, Erich

2009-05-01

399

The influence of bubble evolution on the early characteristics of the boiling liquid expanding vapor explosion  

NASA Astrophysics Data System (ADS)

In the study of boiling liquid expanding vapor explosion (BLEVE), the critical point to interpret the mechanism of the disaster is to analyze the phase transition of the superheated liquid in the container and the motions of the medium during the first several or several tens of milliseconds after the explosion from the microscopic angle of view. In the study recorded in this paper, a BLEVE simulative device was made. Using high-speed camera, the instant explosive boiling in the liquor phase space and the formation and development of the high speed two-phase flow were observed at the moment of the container broken in explosion, the growing and moving speed of the bubble in the liquor phase space were measured, and the influence of the energy released by blasted bubble nucleate in the early stages on the boiling characteristics of the superheated liquid and the overpressure disciplines in the container were analyzed. The study shows that in a BLEVE process, the boiling of superheated liquid does not present in the form of volume boiling, but presents as a progressive process with several steps that starts from the surface and develops over time.

Chen, Sining; He, Xuechao; Sun, Jinhua

2008-11-01

400

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

401

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

402

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

403

Boiling behavior of sodium-potassium alloy in a bench-scale solar receiver  

NASA Astrophysics Data System (ADS)

During 1989-90, a 75-kW(sub t) sodium reflux pool-boiler solar receiver was successfully demonstrated at Sandia National Laboratories. Significant features of this receiver include the following: (1) boiling sodium as the heat transfer medium, and (2) electric-discharge-machined (EDM) cavities as artificial nucleation sites to stabilize boiling. Since this first demonstration, design of a second-generation pool-boiler receiver that will bring the concept closer to commercialization has begun. For long life, the new receiver uses Haynes Alloy 230. For increased safety factors against film boiling and flooding, it has a refined shape and somewhat larger dimensions. To eliminate the need for trace heating, the receiver will boil the sodium-potassium alloy NaK-78 instead of sodium. To reduce manufacturing costs, it will use one of a number of alternatives to EDM cavities for stabilization of boiling. To control incipient-boiling superheats, especially during hot restarts, it will contain a small amount of inert gas. Before the new receiver design could be finalized, bench-scale tests of some of the proposed changes were necessary. A series of bench-scale pool boilers were built from Haynes Alloy 230 and filled with NaK-78. Various boiling-stabilizer candidates were incorporated into them, including laser-drilled cavities and a number of different sintered-powder-metal coatings. These bench-scale pool boilers have been operated at temperatures up to 750 C, heated by quartz lamps with incident radiant fluxes up to 95 W/sq cm. The effects of various orientations and added gases have been studied. Results of these studies are presented.

Moreno, J. B.; Andraka, C. E.; Moss, T. A.

404

Enhanced Boiling on Micro-Configured Composite Surfaces Under Microgravity Conditions  

NASA Technical Reports Server (NTRS)

In order to accommodate the growing thermal management needs of future space platforms, several two-phase active thermal control systems (ATCSs) have evolved and were included in the designs of space stations. Compared to the pumped single-phase liquid loops used in the conventional Space Transportation System and Spacelab, ATCSs offer significant benefits that may be realized by adopting a two-phase fluid-loop system. Alternately, dynamic power systems (DPSs), based on the Rankine cycle, seem inevitably to be required to supply the electrical power requirements of expanding space activities. Boiling heat transfer is one of the key technologies for both ATCSs and DPSs. Nucleate boiling near critical heat flux (CHF) can transport very large thermal loads with much smaller device size and much lower pumping power. However, boiling performance deteriorates in a reduced gravity environment and operation in the CHF regime is precarious because any slight overload will cause the heat transfer to suddenly move to the film boiling regime, which in turn, will result in burnout of the heat transfer surfaces. New materials, such as micro-configured metal-graphite composites, can provide a solution for boiling enhancement. It has been shown experimentally that this type of material manifests outstanding boiling heat transfer performance and their CHF is also extended to higher values. Due to the high thermal conductivity of graphite fiber (up to 1,200 W/m-K in the fiber direction), the composite surfaces are non-isothermal during the boiling process. The composite surfaces are believed to have a much wider safe operating region (a more uniform boiling curve in the CHF regime) because non-isothermal surfaces have been found to be less sensitive to variations of wall superheat in the CHF regime. The thermocapillary forces formed by the temperature difference between the fiber tips and the metal matrix play a more important role than the buoyancy in the bubble detachment, for the bubble detachment manifests itself by a necking process which should not be weakened by reduced gravity. In addition, the composite surfaces introduce no extra pressure drop, no fouling and do not impose significant primary or maintenance costs. All of these suggest that this type of composite is an ideal material for the challenge of accounting for both reliability and economy of the relevant components applied in the ATCSs, the DPSs and other devices in future space missions. The aim of the proposed work is to experimentally investigate high nucleate pool boiling performance on a micro-configured metal-graphite composite surface and to determine the mechanisms of the nucleate boiling heat transfer both experimentally and theoretically. Freon-113 and water will be used as the test liquids to investigate wettability effects on boiling characteristics. The Cu-Gr and Al-Gr composites with various volume fractions of graphite fibers will be tested to obtain the heat transfer characteristic data in the nucleate boiling region and in the CHF regime. In the experiments, the bubble emission and coalescence processes will be recorded by a video camera with a magnifying borescope probe immersed in the working fluid. The temperature profile in the thermal boundary layer on the composite surfaces will be measured by a group of micro thermocouples consisting of four ultra fine micro thermocouples. This instrument was developed and successfully used to measure the temperature profile of evaporating liquid thin layers by the proposers in a study performed at the NASA/Lewis Research Center. A two tier model to explain the nucleate boiling process and the performance enhancement on the composite surfaces has been suggested by the authors. According to the model, the thicknesses of the microlayer and the macrolayer underneath the bubbles and mushrooms, can be estimated by the geometry of the composite surface. The experimental results will be compared to the predictions from the model, and in turn, to revise and improve it.

Zhang, Nengli; Chai, An-Ti

1999-01-01

405

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

406

Marangoni effects on near-bubble microscale transport during boiling of binary fluid mixtures  

NASA Astrophysics Data System (ADS)

In this study, boiling experiments of 2-propanol/water mixtures in confined gap geometry under various levels of gravity were conducted to examine the Marangoni effects on near-bubble microscale transport. Full boiling curves were obtained and two boiling regimes---nucleate boiling and pseudo film boiling, and the transition condition, critical heat flux, identified. In the nucleate boiling regime, small bubbles were generated, condensed quickly in the bulk liquid, so that the agitation in the system resulted in great heat transfer performance. As the superheat level increased, the bubbles coalesced to a large vapor slug that was constrained by the gap geometry and started to blanket the heated surface. The maximum heat flux, (i.e. the critical heat flux, CHF), was then reached. The pseudo film boiling regime was reached by further increasing the superheat level, creating a slow, fluctuated bubble where boiling only occurred at its base perimeter because the heated surface was dried out. The temperature field created within the parallel plate gap resulted in evaporation over the portion of the vapor-liquid interface of the bubble near the heated surface, and condensation near the cold surface. This scenario produced a heat pipe effect inside the constrained bubble. For positive mixtures, Marangoni forces were proven to greatly enhance heat transfer under reduced and terrestrial gravity when compared with the boiling of distilled water. However, the presence of the gap geometry caused a premature occurrence of CHF conditions, and deteriorated heat transfer at high superheated temperatures. The influence of the confined space was particularly significant when greater Marangoni forces were presented under reduced gravity conditions. It caused the value of the CHF for x = 0.025, which corresponded to weaker Marangoni forces, to be greater than that of x = 0.015 with a 6.35 mm gap. This demonstrates the complex interaction that these three factors---Marangoni effects, gravity level, and gap size---have on heat transfer. A major contribution of this study is that it provides a parametric database, further expanding the knowledge in the field of heat transfer to make more optimal use of coolant composed of binary mixtures in various thermal applications.

Sun, Chen-Li

407

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

408

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

409

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

410

A study of flow boiling phenomena using real time neutron radiography  

Microsoft Academic Search

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

David Raymond Novog

2000-01-01

411

Magnetic resonance imaging of boiling induced by high intensity focused ultrasound.  

PubMed

Both mechanically induced acoustic cavitation and thermally induced boiling can occur during high intensity focused ultrasound (HIFU) medical therapy. The goal was to monitor the temperature as boiling was approached using magnetic resonance imaging (MRI). Tissue phantoms were heated for 20 s in a 4.7-T magnet using a 2-MHz HIFU source with an aperture and radius of curvature of 44 mm. The peak focal pressure was 27.5 MPa with corresponding beam width of 0.5 mm. The temperature measured in a single MRI voxel by water proton resonance frequency shift attained a maximum value of only 73 degrees C after 7 s of continuous HIFU exposure when boiling started. Boiling was detected by visual observation, by appearance on the MR images, and by a marked change in the HIFU source power. Nonlinear modeling of the acoustic field combined with a heat transfer equation predicted 100 degrees C after 7 s of exposure. Averaging of the calculated temperature field over the volume of the MRI voxel (0.3 x 0.5 x 2 mm(3)) yielded a maximum of 73 degrees C that agreed with the MR thermometry measurement. These results have implications for the use of MRI-determined temperature values to guide treatments with clinical HIFU systems. PMID:19354416

Khokhlova, Tatiana D; Canney, Michael S; Lee, Donghoon; Marro, Kenneth I; Crum, Lawrence A; Khokhlova, Vera A; Bailey, Michael R

2009-04-01

412

Measurement of vapor superheat in post-critical-heat-flux boiling  

Microsoft Academic Search

A differentially-aspirated superheat probe was developed to measure vapor temperatures in post-critical-heat-flux, dispersed-flow boiling. Measurements obtained for water, at low-to-moderate pressures and mass flow rates in a tube, indicated very significant nonequilibrium, with vapor superheats of several hundred degrees (°C). Predictions of published correlations showed unsatisfactory agreement with the experimental results.

S. Nijhawan; J. C. Chen; R. K. Sundaram; E. J. London

1980-01-01

413

A comparison of the NPL and LNE-Cnam silver and copper fixed-point blackbody sources, and measurement of the silver/copper temperature interval  

NASA Astrophysics Data System (ADS)

The silver and copper fixed-point blackbody sources of NPL were directly compared with those of LNE-Cnam using an IKE LP3 and an IKE LP5 at three wavelengths (650 nm, 795 nm and 903 nm). The two silver fixed points and the two copper fixed points were in excellent agreement with each other, with a difference of 11 mK for the silver and within 16 mK for the copper, with an expanded measurement uncertainty of between 10 mK and 20 mK depending on the pyrometer used. The temperature interval between the silver and copper freezing points was also measured using combinations of all four fixed points. The results with the NPL LP3 gave a value for the silver-copper temperature interval of 122.89 C with an expanded uncertainty of 30 mK those with the LNE-Cnam LP5 gave a temperature interval of 122.87 C also with an expanded uncertainty of 30 mK this compares with the ITS-90 value of 122.84 C.

McEvoy, H. C.; Sadli, M.; Bourson, F.; Briaudeau, S.; Rougi, B.

2013-12-01

414

Performance of a solar-air-conditioning system utilizing boiling collectors  

SciTech Connect

A boiling-collector system provides a high-temperature organic vapor directly to the expander of a Rankine engine, which may drive an air conditioning compressor or an electrical generator. This system eliminates several pumps, a heat exchanger, and a hot-storage tank from the conventional solar air conditioning system, thereby reducing heat losses and parasitic power requirements. This system was modeled on a computer and the performance compared with the performance of the conventional system. The calculations were done hourly for commercial buildings in Phoenix, Fort Worth, and Miami. The boiling system outperforms the conventional solar system by 28% or more depending on collector type and location.

Hedstrom, J.C.

1983-04-01

415

Tipping Points  

NASA Astrophysics Data System (ADS)

A climate tipping point, at least as I have used the phrase, refers to a situation in which a changing climate forcing has reached a point such that little additional forcing (or global temperature change) is needed to cause large, relatively rapid, climate change. Present examples include potential loss of all Arctic sea ice and instability of the West Antarctic and Greenland ice sheets. Tipping points are characterized by ready feedbacks that amplify the effect of forcings. The notion that these may be runaway feedbacks is a misconception. However, present "unrealized" global warming, due to the climate system's thermal inertia, exacerbates the difficulty of avoiding global warming tipping points. I argue that prompt efforts to slow CO2 emissions and absolutely reduce non-CO2 forcings are both essential if we are to avoid tipping points that would be disastrous for humanity and creation, the planet as civilization knows it.

Hansen, J.

2007-12-01

416

Moored observations of the current and temperature structure over the continental slope off central California 2. The energetics of the flow off Point Sur  

Microsoft Academic Search

The data from two current meter moorings off Point Sur, California, were analyzed to examine the energy transfers over the continental slope in the California Current system (CCS). The method used was to calculate terms in the heat equation at intermediate depths between instruments, using the thermal wind relation to estimate the horizontal temperature gradients from the vertical shear. Time

Timothy D. Tisch; Steven R. Ramp

1997-01-01

417

The effects of quantum zero point energy fluctuations on the variation with concentration of the maximum density temperatures in wateralcohol solutions  

Microsoft Academic Search

Unlike the situation for ionic aqueous solutions, the relationship between the density maximum temperature Tmd and solute concentration for aqueous solutions of primary alcohols is known to be strongly non-linear. Using our recent theory for the existence of the maximum density in water in terms of quantum zero point energy effects, we explain why this is so. We also explain

F. A. Deeney; J. P. OLeary; B. Cronin; D. M. OLeary

2008-01-01

418

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

419

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

420

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

421

A theoretical study of free convection in turbulent film boiling on a horizontal elliptical tube  

NASA Astrophysics Data System (ADS)

The present theoretical study investigates turbulent film boiling on an isothermal elliptical tube under quiescent liquid. The effect of radiation is included in the present analysis. The results of the boiling heat transfer under the turbulent vapor show both the temperature and velocity present the non-linear distribution. Besides, under the free convection turbulent film boiling with higher Rayleigh values, the elliptical tube can get a better heat transfer efficiency than a circular tube. However, when Rayleigh values are low, the eccentricity of an elliptical tube seldom influences the heat transfer. Finally, a comparison between the results of the present study and those reported in a previous theoretical and experimental data is provided.

Hu, Hai-Ping; Chen, Cha'o.-Kuang

2008-08-01

422

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

423

Facilitating Conceptual Change in Students' Understanding of Boiling Concept  

NASA Astrophysics Data System (ADS)

The objective of this study was to construct a teaching strategy for facilitating students' conceptual understanding of the boiling concept. The study is based on 52 freshman students in the primary science education department. Students' ideas were elicited by a test consisting of nine questions. Conceptual change strategy was designed based on students' alternative conceptions. Conceptual change in students' understanding of boiling was evaluated by administering a pre-, post- and delayed post-test. The test scores were analysed both by qualitative and quantitative methods. Statistical analysis using one-way ANOVA of student test scores pointed to statistically significant differences in the tests and total scores ( p < 0.05). Quantitative analysis of students' responses on each test revealed different schema about changing their knowledge system. Both qualitative and quantitative analyses suggest that the teaching activities facilitated students' conceptual understanding. No statistically significant differences were found between post-test and delayed post-test scores, suggesting that the teaching strategy enabled students to retain their new conceptions in the long-term memory.

Co?tu, Bayram; Ayas, Alipa?a; Niaz, Mansoor; nal, Suat; alik, Muammer

2007-12-01