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1

Modeling Local Hygrothermal Interaction: Local surface transfer coefficients  

DEFF Research Database (Denmark)

Current models to predict heat, air and moisture (HAM) conditions in building components assume uniform boundary conditions, both for the temperature and relative humidity of the air in an indoor space as well as for the heat and moisture surface transfer coefficients. In order to obtain a reliable prediction of the HAM conditions in a building component, an accurate description of the indoor boundary conditions is required. This paper presents the modelling of the local indoor environmental conditions, using a (sub)zonal airflow model, focussing on the prediction of the local interior surface heat and moisture transfer coefficients. The research showed that the developed model gives good agreement with the local convective surface transfer coefficients predicted from CFD. The main advantage of the presented (sub)zonal airflow model is that the computational effort is relatively small, while the predictions of the local surface transfer coefficients are relatively accurate.

Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans

2009-01-01

2

Determination of the surface heat-transfer coefficient in CE.  

UK PubMed Central (United Kingdom)

A knowledge of the heat-transfer coefficient, h(s), for the external surface of the capillary or the overall heat coefficient, h(OA), is of great value in predicting the mean increase in temperature of the electrolyte, DeltaT(Mean), during electrokinetic separations. For CE, traditional indirect methods of determining h(s) were time-consuming and tended to overestimate cooling efficiency; a novel method is introduced, which is based on curve-fitting of plots of conductance versus voltage to calculate several important parameters including DeltaT(Mean), h(s), the conductance free of Joule heating effects (G(0)) and the voltage that causes autothermal runaway, V(lim). The new method is superior to previously published methods in that it can be performed more quickly and that it corrects for systematic errors in the measurement of electric current for voltages <5 kV. These errors tended to exaggerate the cooling efficiency of commercial instruments so that the calculated increases in electrolyte temperature were smaller than their actual values. Axially averaged values for h(s) were determined for three different commercial CE instruments ranging from 164 W m(-2) K(-1) for a passively cooled instrument in a drafty environment to 460 W m(-2) K(-1) for a liquid-cooled instrument.

Hruska V; Evenhuis CJ; Guijt RM; Macka M; Gas B; Marriott PJ; Haddad PR

2009-03-01

3

Surface heat and mass transfer coefficients for multiphase porous media transport models with rapid evaporation  

UK PubMed Central (United Kingdom)

Multiphase transport models of food processes require surface heat and mass transfer coefficients as boundary conditions that are traditionally assumed. A conjugate heat and mass transfer model is solved for simple microwave heating of food as a porous medium (from which vapor blows out) with air flow over it, such that there is no need to provide the boundary conditions at the food–air interface. Surface fluxes due to diffusion and flow (blowing) are computed for both vapor and heat from which transfer coefficients are obtained. As evaporation increases with heating, vapor flux due to pressure-driven flow increases but remains small compared with diffusive flux. Vapor accumulation at the interface increases the diffusive flux, leading to an 8% increase in mass transfer coefficient. Heat transfer at the interface occurs through both conduction and flow, and the heat transfer coefficient shows a slight decrease (10%) as blowing increases with heating. The rate of heating has minimal effect on the transfer coefficients.

Halder A; Datta AK

2012-07-01

4

Influence of the convective surface transfer coefficients on the Heat, Air, and Moisture (HAM) building performance  

DEFF Research Database (Denmark)

Current models to predict heat, air and moisture (HAM) conditions in buildings assume constant boundary conditions for the temperature and relative humidity of the neighbouring air and for the surface heat and moisture transfer coefficients. These assumptions may introduce errors in the predicted HAM conditions. The paper focuses on the influence of the interior surface heat and moisture transfer coefficients, and investigates its effect on the hygrothermal performance. The parameter study showed that the magnitude of the convective surface transfer coefficients have a relatively large influence on the predicted hygrothermal conditions at the surface of a building component and on the heat and vapour exchange with the indoor environment.

Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans

2009-01-01

5

The heat transfer coefficients of the heating surface of 300 MWe CFB boiler  

Science.gov (United States)

A study of the heat transfer about the heating surface of three commercial 300 MWe CFB boilers was conducted in this work. The heat transfer coefficients of the platen heating surface, the external heat exchanger (EHE) and cyclone separator were calculated according to the relative operation data at different boiler loads. Moreover, the heat transfer coefficient of the waterwall was calculated by heat balance of the hot circuit of the CFB boiler. With the boiler capacity increasing, the heat transfer coefficients of these heating surface increases, and the heat transfer coefficient of the water wall is higher than that of the platen heating surface. The heat transfer coefficient of the EHE is the highest in high boiler load, the heat transfer coefficient of the cyclone separator is the lowest. Because the fired coal is different from the design coal in No.1 boiler, the ash content of the fired coal is much lower than that of the design coal. The heat transfer coefficients which calculated with the operation data are lower than the previous design value and that is the reason why the bed temperature is rather high during the boiler operation in No.1 boiler.

Wu, Haibo; Zhang, Man; Lu, Qinggang; Sun, Yunkai

2012-08-01

6

Calculation of heat transfer coefficients at the ingot surface during DC casting  

Energy Technology Data Exchange (ETDEWEB)

Surface heat transfer coefficients representing the various regimes of water cooling during the Direct Chill (DC) casting of aluminum 3004 alloy ingots have been calculated using the inverse heat transfer technique. ProCAST, a commercial casting simulation package, which includes heat transfer, fluid flow, solidification, and inverse heat transfer, was used for this effort. Thermocouple data from an experimental casting run, and temperature-dependent thermophysical properties of the alloy were used in the calculation. The use of a structured vs. unstructured mesh was evaluated. The calculated effective heat transfer coefficient, which is a function of temperature and time, covers three water cooling regimes, i.e., convection, nucleate boiling, and film boiling, and the change of water flow rate with time.

Kuwana, K.; Viswanathan, S.; Clark, John A, III; Sabau, A.; Hassan, M.; Saito, K.; Das, S.

2005-02-01

7

Impact of overall and particle surface heat transfer coefficients on thermal process optimization in rotary retorts.  

UK PubMed Central (United Kingdom)

This study attempts to examine the significance of recent research that has focused on efforts to estimate values for global and surface heat transfer coefficients under forced convection heating induced by end-over-end rotation in retorting of canned peas in brine. The study confirms the accuracy of regression analysis used to predict values for heat transfer coefficients as a function of rotating speed and headspace, and uses them to predict values over a range of process conditions, which make up the search domain for process optimization. These coefficients were used in a convective heat transfer model to establish a range of lethality-equivalent retort temperature-time processes for various conditions of retort temperature, rotating speed, and headspace. Then, they were coupled with quality factor kinetics to predict the final volume average and surface quality retention resulting from each process and to find the optimal thermal process conditions for canned fresh green peas. Results showed that maximum quality retention (surface and volume average retention) was achieved with the shortest possible process time (made possible with highest retort temperature), and reached the similar level in all cases with small difference between surface and volume average quality retention. The highest heat transfer coefficients (associated with maximum rotating speed and headspace) showed a 10% reduction in process time over that required with minimum rotating speed and headspace. The study concludes with a discussion of the significance of these findings and degree to which they were expected.

Simpson R; Abakarov A; Almonacid S; Teixeira A

2008-10-01

8

Heat transfer coefficient in the reactor containment with noncondensable gases and wavy surface  

International Nuclear Information System (INIS)

[en] To ensure the safety of nuclear power plant, the analysis of the containment integrity in postulated accident is very important, and the use of the accurate heat transfer coefficient correlation applicable to containment analysis is necessary. But, during the postulated accident, it is difficult to obtain the accurate heat transfer coefficient due to the nonuniform velocity distribution, turbulent flow, wave formation at interface, etc., and the existing heat transfer correlation is mostly relied on simple experimental correlations. In this study, the existence of noncondensable gas and the wavy surface of the falling liquid film was assumed. The heat transfer coefficient model of this study is obtained from the existing simple correlations of the laminar and turbulent forced convective heat transfer at a vertical flat plate. The effect of various noncondensable gas mass ratios, gas flow velocities and plate length on heat transfer coefficient is calculated. The calculation result of low gas velocity(lm/s) was compared with the Uchida's experimental results and Carbajo's correlation. (Author)

1992-01-01

9

Numerical study on correlation of heat transfer coefficient with void fraction at heat transfer tube surface in sodium water reaction  

International Nuclear Information System (INIS)

The present paper deals with a sodium water reaction (SWR) in a steam generator (SG) of sodium-cooled fast reactor (SFR). When a heat transfer tube in the SG fails, SWR would take place. This reaction occurs rapidly and accompanies a high temperature jet. This jet would cover up the neighboring tubes and the tubes have possibilities to fail secondarily by an overheated rupture. Therefore, the quantification of the heat transfer from the fluid to the tube in the SWR is important from the view point of safety evaluation. To obtain knowledge on the SWR phenomenon, experiments with SWAT-1R test facility were carried out at Japan Atomic Energy Agency (JAEA). In the experiment, thermocouples were installed at 6 locations on a tube placed for measurement in the SWR reacting zone and the temperature histories were measured. In the present study, the heat transfer coefficient has been evaluated by solving one-dimensional inverse problem of heat transfer based on the SWAT-1R experimental result. And the flow characteristics such as a void fraction and a fluid velocity, at the surface of the heat transfer tube have been speculated from the magnitude of heat transfer coefficient. Furthermore, one-dimensional thermal hydraulics simulation has been performed based on a boundary layer approximation. In the analyses, the fluid velocity at out of the boundary layer and the void fraction condition are given as a parameter. As a result, the correlation diagram between the heat transfer coefficient and the flow characteristics has been evaluated so as to investigate the flow characteristics in the SWAT-1R experiment. (author)

2009-10-02

10

Equivalent thermophysical properties and surface heat transfer coefficient of fruit layers in trays during cooling.  

UK PubMed Central (United Kingdom)

Experimental engineering data and predictive equations are established for the equivalent thermophysical properties (thermal conductivity, thermal diffusivity, specific heat capacity and density) and surface heat transfer coefficient of bulk layers of fruits (strawberries, raspberries, apricots, peaches, grapes and apples) in trays. Both packed layers and uncovered trays are considered as a system of fruits and air. In the first case the influence of air inclusions and free convection in closed space is taken into account, while in the second--special attention is devoted to the effect of air infiltration between the fruits placed in trays and pallets. The regression equations derived give the relationship between the considered equivalent values and the velocity of longitudinal air flow between the trays. The results are appropriate to be used for mathematical modelling and engineering calculations in real industrial heat transfer scenarios.

Fikiin AG; Fikiin KA; Triphonov SD

1999-05-01

11

An experimental investigation of the rib surface-averaged heat transfer coefficient in a rib-roughened square passage  

Energy Technology Data Exchange (ETDEWEB)

Turbine blade cooling is accomplished, among other methods, by passing the cooling air through an often serpentine passage in the core of the blade. Furthermore, to enhance the heat transfer coefficient, these passages are roughened with rib-shaped turbulence promoters. Considerable data are available on the heat transfer coefficient on the passage surface between the ribs. However, the heat transfer coefficients on the surface of the ribs themselves have not been investigated to the same extent. Therefore, an accurate account of the heat transfer coefficient on the rib surfaces is critical in the overall design of the blade cooling system. The objective of this experimental investigation was to conduct a series of 13 tests to measure the rib surface-averaged heat transfer coefficient, h{sub rib} in a square duct roughened with staggered 90 deg ribs. To investigate the effects that blockage ratio, e/D{sub h}, and pitch-to-height ratio, S/e, have on h{sub rib} and passage friction factor, three rib geometries corresponding to blockage ratios of 0.133, 0.167, and 0.25 were tested for pitch-to-height ratios of 5, 7, 8.5, and 10. Comparisons were made between the rib average heat transfer coefficient and that on the wall surface between two ribs, h{sub floor}, reported previously. It is concluded that: The rib average heat transfer coefficient is much higher than that for the area between the ribs; similar to the heat transfer coefficient on the surface between the ribs, the average rib heat transfer coefficient increases with the blockage ratio; a pitch-to-height ratios of 8.5 consistently produced the highest rib average heat transfer coefficients amongst all tested; under otherwise identical conditions, ribs in upstream-most position produced lower heat transfer coefficients than the midchannel positions; the upstream-most rib average heat transfer coefficients decreased with the blockage ratio; and thermal performance decreased with increased blockage ratio.

Taslim, M.E.; Wadsworth, C.M. [Northeastern Univ., Boston, MA (United States). Dept. of Mechanical Engineering

1997-04-01

12

Determination of local heat transfer coefficient on the surface of longitudinally finned tubes  

Energy Technology Data Exchange (ETDEWEB)

The distribution of the heat transfer coefficient is calculated from temperature measurements at interior points of the solid, and the measured fluid temperature. The unknown parameters associated with the solution were selected to achieve the closest least squares agreement between the computed and measured temperatures using the Levenberg-Marquardt method. The nonlinear least - squares problem is parameterised by assuming the stair-case changes of the heat transfer coefficient on the boundary, or by expressing the space variations of the heat transfer coefficient in its functional form. The determination of the circumferential heat transfer coefficient distribution on the heated tube with two longitudinal fins in cross flow demonstrates the accuracy of the developed method. The actual experimental data were used. Experiments were performed with an array of vertical tubes arranged in staggered pattern. (orig.)

Sobota, T.; Taler, J. [Cracow Univ. of Technology (Poland). Inst. of Process and Power Engineering

2008-06-15

13

To the defenition of the heat transfer coefficient on film condensation of immobile vapor on a vertical surface  

International Nuclear Information System (INIS)

[en] The technique of calculation of average heat transfer coefficient during film condensation on a vertical surface under the conditions of laminar, laminar-wave and turbulent regimes of condensate film leakage is proposed. The conclusion is drawn that at wave film leakage satisfactory results are given by the heat transfer coefficient calculation on ''residual'' film thickness determined by a certain Reynolds specific number Re *

1980-01-01

14

FLOW VELOCITY AND SURFACE TEMPERATURE EFFECTS ON CONVECTIVE HEAT TRANSFER COEFFICIENT FROM URBAN CANOPY SURFACES BY NUMERICAL SIMULATION  

Directory of Open Access Journals (Sweden)

Full Text Available This study investigates the effect of flow velocity and building surface temperature effects on Convective Heat Transfer Coefficient (CHTC) from urban building surfaces by numerical simulation. The thermal effects produced by geometrical and physical properties of urban areas generate a relatively differential heating and uncomfortable environment compared to rural regions called as Urban Heat Island (UHI) phenomena. The urban thermal comfort is directly related to the CHTC from the urban canopy surfaces. This CHTC from urban canopy surfaces expected to depend upon the wind velocity flowing over the urban canopy surfaces, urban canopy configurations, building surface temperature etc. But the most influential parameter on CHTC has not been clarified yet. Urban canopy type experiments in thermally stratified wind tunnel have normally been used to study the heat transfer issues. But, it is not an easy task in wind tunnel experiments to evaluate local CHTC, which vary on individual canyon surfaces such as building roof, walls and ground. Numerical simulation validated by wind tunnel experiments can be an alternative for the prediction of CHTC from building surfaces in an urban area. In our study, wind tunnel experiments were conducted to validate the low-Reynolds-number k-? model which was used for the evaluation of CHTC from surfaces. The calculated CFD results showed good agreement with experimental results. After this validation, the effects of flow velocity and building surface temperature effects on CHTC from urban building surfaces were investigated. It has been found that the change in velocity remarkably affects the CHTC from urban canopy surfaces and change in surface temperature has almost no effect over the CHTC from urban canopy surfaces.

Sivaraja Subramania Pillai; Ryuichiro Yoshie

2013-01-01

15

Transfer coefficients for terrestrial foodchains  

International Nuclear Information System (INIS)

[en] Transfer coefficients to predict the passage of isotopes from the environment to terrestrial foods have been derived for various radionuclides of importance in the nuclear fuel cycle. These data update and extend previously recommended handbook values. We derive transfer coefficients to terrestrial foods and describe the systematics of the derived transfer coefficients. Suggestions are offered for changes in the values of transfer coefficients to terrestrial foods that now appear in federal regulatory guides. Deficiencies in our present knowledge concerning transfer coefficients and limitations in the use of these values to ensure compliance with radiation protection standards are discussed. (orig.) 891 HP/orig. 892 MB

1978-10-08

16

Measuring of heat transfer coefficient  

DEFF Research Database (Denmark)

Subtask 3.4 Measuring of heat transfer coefficient Subtask 3.4.1 Design and setting up of tests to measure heat transfer coefficient Objective: Complementary testing methods together with the relevant experimental equipment are to be designed by the two partners involved in order to measure the heat transfer coefficient for a wide range of interface conditions in hot and warm forging processes. Subtask 3.4.2 Measurement of heat transfer coefficient The objective of subtask 3.4.2 is to determine heat transfer values for different interface conditions reflecting those typically operating in hot and warm forging operations.

Henningsen, Poul; Lindegren, Maria

2000-01-01

17

Estimation of internal heat transfer coefficients and detection of rib positions in gas turbine blades from transient surface temperature measurements  

Energy Technology Data Exchange (ETDEWEB)

This paper describes a non-invasive, non-destructive, transient inverse measurement technique that allows one to determine internal heat transfer coefficients and rib positions of real gas turbine blades from outer surface temperature measurements after a sudden flow heating. The determination of internal heat transfer coefficients is important during the design process to adjust local heat transfer to spatial thermal load. The detection of rib positions is important during production to fulfill design and quality requirements. For the analysis the one-dimensional transient heat transfer problem inside of the turbine blade's wall was solved. This solution was combined with the Levenberg-Marquardt method to estimate the unknown boundary condition by an inverse technique. The method was tested with artificial data to determine uncertainties with positive results. Then experimental testing with a reference model was carried out. Based on the results, it is concluded that the presented inverse technique could be used to determine internal heat transfer coefficients and to detect rib positions of real turbine blades.

Heidrich, P; Wolfersdorf, J v; Schmidt, S [Institute of Aerospace Thermodynamics, Universitaet Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart (Germany); Schnieder, M [ALSTOM (Schweiz) AG, Brown Boveri Strasse 7, 5401 Baden (Switzerland)], E-mail: peter.heidrich@itlr.uni-stuttgart.de

2008-11-01

18

Estimation of internal heat transfer coefficients and detection of rib positions in gas turbine blades from transient surface temperature measurements  

International Nuclear Information System (INIS)

This paper describes a non-invasive, non-destructive, transient inverse measurement technique that allows one to determine internal heat transfer coefficients and rib positions of real gas turbine blades from outer surface temperature measurements after a sudden flow heating. The determination of internal heat transfer coefficients is important during the design process to adjust local heat transfer to spatial thermal load. The detection of rib positions is important during production to fulfill design and quality requirements. For the analysis the one-dimensional transient heat transfer problem inside of the turbine blade's wall was solved. This solution was combined with the Levenberg-Marquardt method to estimate the unknown boundary condition by an inverse technique. The method was tested with artificial data to determine uncertainties with positive results. Then experimental testing with a reference model was carried out. Based on the results, it is concluded that the presented inverse technique could be used to determine internal heat transfer coefficients and to detect rib positions of real turbine blades.

2008-11-01

19

HTPGB: a computer program for calculating from experimental data the variation in heat transfer coefficient round a cylindrical surface  

International Nuclear Information System (INIS)

[en] HTPGB1 calculates from experimental data the variation in heat transfer coefficient round a cyclindrical surface. The structure within the cylindrical surface is assumed to consist of a series of concentric annuli for any one of which the physical properties and volume generation of heat remain constant, but may vary from one annulus to another. Conduction of heat along the cylinder is assumed negligible. However, an adjustment for the localised longitudinal conduction effects associated with ribbed surfaces may be included. The information provided by the program can be used in the prediction of round pin temperature variations in a reactor from out-of-pile tests. It is essential for obtaining the correct interpretation of experimental data when the reduction of temperature differences by thermal conduction within the surface is different in the reactor and the experiment. (author)

1975-01-01

20

Heat transfer coefficient for boiling carbon dioxide  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The pipe is heated by condensing R22 outside the pipe. The heat input is supplied by an electrical heater which evaporates the R22. With the heat flux assumed constant over the whole surface and with the measured temperature difference between the inner surface and the evaporation temperature a mean heat transfer coefficient is calculated. The calculated heat transfer coefficient has been compared with the Chart Correlation of Shah. The Chart Correlation predicts too low heat transfer coefficient but the ratio between the measured and the calculated heat transfer coefficient is nearly constant and equal to 1.9. With this factor the correlation predicts the measured data within 14%. (RMS) The pressure drop is of the same order as the measuring uncertainty and the pressure drop has not been compared to correlations. In commercial refrigeration there is a need for information about new refrigerant to be used as substitutes for the present CFC and HCFC refrigerants. An indirect system using ammonia as the primary refrigerant and boiling carbon dioxide as the secondary refrigerant has been proposed. In order to use this combination there is a need for a correlation for the heat transfer coefficient for boiling carbon dioxide based on experiment. This paper will present some experimental results obtained with boiling carbon dioxide in a pipe. 5 refs.

Hoegaard Knudsen, H.J.; Jensen, P.H. [Department of Energy Engineering, Technical University of Denmark, Lyngby (Denmark)

1998-12-31

 
 
 
 
21

Expressions of mass transfer coefficients of bubbles and free surface of culture tanks using the k-epsilon turbulence model.  

UK PubMed Central (United Kingdom)

For mammalian cell culture, getting a continuous supply of oxygen and extracting carbon dioxide are primary challenges even in the most modern biopharmaceutical manufacturing plants, due to the low oxygen solubility and excessive carbon dioxide accumulation. In addition, various independent flow and mass transfer characteristics in the culture tanks vessel make scale-up extremely difficult. One method for overcoming these and providing rational optimization is solving the fluid and mass transport equations by numerical simulation. To develop a simulation program, it is decisively important to know mass transfer coefficients of gaseous species in the culture tank. In this study, oxygen mass transfer coefficients are measured using a beaker with a sparger and impellers. In order to investigate the formulation of the mass transfer coefficients, the turbulent flow statistics is calculated by a CFD code for all cases, and the expressions of the mass transfer coefficients are established as functions of the statistics. Until now, the expression by Kawase is known in this field. This expression becomes a function only of energy dissipation rate epsilon. It does not coincide with the conventional experimental fact that mass transfer coefficient is proportional power 0.5 of impeller rotation speed. The new mass transfer coefficient is dependent on both of energy dissipation rate epsilon and turbulent flow energy k. It satisfies the relation of power of 0.5 of impeller rotation speed.

Amano K; Haga R; Murakami S

2008-06-01

22

UTILITY OF ASSIMILATING SURFACE RADIOMETRIC TEMPERATURE OBSERVATIONS FOR EVAPORATIVE FRACTION AND HEAT TRANSFER COEFFICIENT RETRIEVAL  

Science.gov (United States)

Recent advances in land data assimilation have yielded variational smoother techniques designed to solve the surface energy balance based on remote observation of surface radiometric temperature. These approaches have a number of potential advantages over existing diagnostic models including the ab...

23

Determination of friction factors and heat transfer coefficients for flow past artifically roughened surfaces  

International Nuclear Information System (INIS)

A critical review of the assumptions, theoretical foundations, and supporting experimental evidence for the analytical procedures in current use for evaluation of the effects of artificial surface roughening on friction factor and Stanton number is provided. Recommendations are given concerning the application of these procedures to rough rod bundles. A new method is demonstrated for determination of the slope and intercept of the universal logarithmic dimensionless velocity distribution law for fully rough flow past roughened surfaces without the need for experimental measurement of the velocity profile. The slope is shown to vary with the nature of the roughened surface and to deviate significantly from the slope for turbulent flow past smooth walls in some cases. It is further shown that the intercept, which is a boundary condition equivalent to the roughness parameter for friction, is independent of the width of the velocity profile. A similar method is developed for determination of the slope and intercept of the temperature distribution law, but additional experimental investigation is required before the efficacy of this application can be conclusively established

1979-01-01

24

Inverse determination of local heat transfer coefficient  

International Nuclear Information System (INIS)

[en] The naphtalene sublimation and transient methods are widely used techniques which are particularly useful in complex flows and solid shapes. Both techniques have been widely used with considerable success but they are not appropriate for high temperatures. An alternative method to obtain the local convective heat transfer coefficient, that does not have any disadvantages noted above, is the inverse procedure. Determination of the space-variable heat transfer coefficient on a complex shape surface requires the solution of the nonlinear inverse heat conduction problem. The distribution of the heat transfer coefficient is calculated from temperature measurements at interior points of the solid and measured fluid temperature. The unknown parameters associated with the solution are selected to achieve the closest agreement in a least squares sense between the computed and measured temperatures using the Levenberg - Marquardt method. The nonlinear least - squares problem is parameterized by assuming the staircase changes of heat transfer coefficient on the boundary or expressing the space variations of the heat transfer coefficient in the functional form. The uncertainties in the estimated components of the heat transfer coefficient or in the estimated parameters are determined for the temperature measurements with known and unknown standard deviations. The determination of the circumferential heat transfer coefficient distribution on the heated tube with two longitudinal fins in cross flow demonstrates the accuracy of the developed method. The actual experimental data were used. Experiments were performed with an array of vertical tubes arranged in staggered pattern. The experimental results reported herein are among the first that show the variation of the local heat transfer coefficients over the circumference of the finned tube. Most data reported previously were acquired for smooth tubes at low temperatures. The main advantage of the method is that it does not require any knowledge, or solution to, the complex fluid flow field. It should be noted that determining unknown steady distribution of heat transfer coefficients by using the developed method is inexpensive, since it requires only one fluid temperature probe and a few thermocouples for temperature measurements inside the solid. Refs. 4 (author)

2002-01-01

25

Comparison of maximum coefficients of heat transfer to a surface submerged in a fluidized bed with an estimate obtained from an empirical formula  

Energy Technology Data Exchange (ETDEWEB)

This paper compares the empirical coefficients of heat transfer from a fluidized bed to bodies of various shapes with coefficients calculated from a formula which considers heat transfer by particle and gas convection and by radiation.

Baskakov, A.P.; Panov, O.M.

1984-06-01

26

Rewetting of hot surfaces-evaluation of wet region heat transfer coefficient from experimental data and prediction of rewetting velocity based on two-region model  

International Nuclear Information System (INIS)

[en] The phenomenon of rewetting of hot surfaces is of significance in the context of emergency core cooling of water cooled nuclear reactors. Solutions have been obtained for conduction controlled rewetting of hot surfaces, based on two-region model, and these are correlated to relate Biot number and Peclet number and the non-dimensional temperature. Using these and the published data on rewetting velocity, wet region heat transfer coefficient values have been evaluated separately for falling film rewetting and bottom flooding rewetting. Based on these values correlations have been obtained for the wet region heat transfer coefficient by regression analysis. These correlations along with that for Peclet number have been used for predicting rewetting velocities. Reasonably good agreement is noted between the predicted values and experimental data

1990-01-01

27

Concentration, Soil-to-Plant Transfer Factor and Soil-Soil Solution Distribution Coefficient of Selenium in the Surface Environment  

International Nuclear Information System (INIS)

Of the major radioactive selenium isotopes, Se-79, a beta emitter with a half-life of about 1.1 million years, is of special interest because it is one of the most important radionuclides for the long-term dose assessment of radioactive waste disposal. This radionuclide can reach human beings through several transfer paths in the environment. To predict Se-79 behavior from the environment to human beings, it would be useful to obtain the following information: stable Se concentration in environmental samples; soil-soil solution distribution coefficient (Kd); and soil-to-plant transfer factor (TF). In the present study, stable Se concentrations in river water, soil and crop samples collected in Japan, Kds and TFs were obtained. The results showed that geometric mean (GM) concentrations of river water, soil and crops were 0.057 ?g/L (range: ds for paddy field soil and upland field soil samples were 116 and 67, respectively, whereas GMs of TFs for brown rice and upland field crops were 0.066 and 0.024, respectively. Probably due to longer growing period and different water management in the paddy fields for brown rice compared to those for upland field crops, the TF would be high in brown rice. (authors)

2009-01-01

28

Heat transfer coefficient for boiling carbon dioxide.  

DEFF Research Database (Denmark)

Heat transfer coefficient and pressure drop for boiling carbon dioxide (R744) flowing in a horizontal pipe has been measured. The calculated heat transfer coeeficient has been compared with the Chart correlation of Shah. The Chart Correlation predits too low heat transfer coefficient but the ratio between the measured and the calculated heat transfer coefficient is nearly constant and equal 1.9. With this factor the correlation predicts the measured data within 14% (RMS). The pressure drop is of the same order as the measuring uncertainty and the pressure drop has not been compared with correlation's.

Knudsen, Hans JØrgen HØgaard; Jensen, Per Henrik

1998-01-01

29

Heat transfer coefficient of cryotop during freezing.  

Science.gov (United States)

Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K). PMID:23812315

Li, W J; Zhou, X L; Wang, H S; Liu, B L; Dai, J J

2013-01-01

30

Heat transfer coefficient of cryotop during freezing.  

UK PubMed Central (United Kingdom)

Cryotop is an efficient vitrification method for cryopreservation of oocytes. It has been widely used owing to its simple operation and high freezing rate. Recently, the heat transfer performance of cryotop was studied by numerical simulation in several studies. However, the range of heat transfer coefficient in the simulation is uncertain. In this study, the heat transfer coefficient for cryotop during freezing process was analyzed. The cooling rates of 40 percent ethylene glycol (EG) droplet in cryotop during freezing were measured by ultra-fast measurement system and calculated by numerical simulation at different value of heat transfer coefficient. Compared with the results obtained by two methods, the range of the heat transfer coefficient necessary for the numerical simulation of cryotop was determined, which is between 9000 W/(m(2)·K) and 10000 W/(m (2)·K).

Li WJ; Zhou XL; Wang HS; Liu BL; Dai JJ

2013-05-01

31

Wind heat transfer coefficient in solar collectors in outdoor conditions  

Energy Technology Data Exchange (ETDEWEB)

Knowledge of wind heat transfer coefficient, h{sub w}, is required for estimation of upward losses from the outer surface of flat plate solar collectors/solar cookers. In present study, an attempt has been made to estimate the wind induced convective heat transfer coefficient by employing unglazed test plate (of size about 0.9 m square) in outdoor conditions. Experiments, for measurement of h{sub w}, have been conducted on rooftop of a building in the Institute campus in summer season for 2 years. The estimated wind heat transfer coefficient has been correlated against wind speed by linear regression and power regression. Experimental values of wind heat transfer coefficient estimated in present work have been compared with studies of other researchers after normalizing for plate length. (author)

Kumar, Suresh; Mullick, S.C. [Centre for Energy Studies, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016 (India)

2010-06-15

32

Transfer coefficients for turbulent flow between parallel plates  

International Nuclear Information System (INIS)

Average transfer coefficients in the turbulent forced convection entrance region between parallel plates, with asymmetrical conditions of the concentration profile, were determined experimentaly with the Naphthalene Sublimation Technique. In accordance with the analogy between heat and mass transfer, the tests correspond to a heat-transfer problem with uniform surface temperature at one plate and the other insulated. The Reynolds number ranges from 10900 to 91700. (Author)

1981-12-18

33

Determination of the heat transfer coefficients in transient heat conduction  

Science.gov (United States)

The determination of the space- or time-dependent heat transfer coefficient which links the boundary temperature to the heat flux through a third-kind Robin boundary condition in transient heat conduction is investigated. The reconstruction uses average surface temperature measurements. In both cases of the space- or time-dependent unknown heat transfer coefficient the inverse problems are nonlinear and ill posed. Least-squares penalized variational formulations are proposed and new formulae for the gradients are derived. Numerical results obtained using the nonlinear conjugate gradient method combined with a boundary element direct solver are presented and discussed.

Nho Hào, Dinh; Thanh, Phan Xuan; Lesnic, D.

2013-09-01

34

Heat transfer coefficient between UO2 and Zircaloy-2  

International Nuclear Information System (INIS)

[en] This paper provides some experimental values of the heat-transfer coefficient between UO2 and Zircaloy-2 surfaces in contact under conditions of interfacial pressure, temperature, surface roughness and interface atmosphere, that are relevant to UO2/Zircaloy-2 fuel elements operating in pressurized-water power reactors. Coefficients were obtained from eight UO2/ Zircaloy-2 pairs in atmospheres of helium, argon, krypton or xenon, at atmosphere pressure and in vacuum. Interfacial pressures were varied from 50 to 550 kgf/cm2 while surface roughness heights were in the range 0.2 x 10-4 to 3.5 x 10-4 cm. The effect on the coefficients of cycling the interfacial pressure, of interface gas pressure and of temperature were examined. The experimental values of the coefficients were used to test the predictions of expressions for the heat-transfer between two solids in contact. For the particular UO2/ Zircaloy-2 pairs examined, numerical values were assigned to several parameters that related the surface roughnesses to either the radius of solid/solid contact spots or to the mean thickness of the interface voids and that accounted for the imperfect accommodation of the void gas on the test surfaces. (author)

1962-01-01

35

Measurement of heat (mass) transfer coefficient on the surface of a turbine blade with a high turing angle using naphthalene sublimation technique  

International Nuclear Information System (INIS)

The heat (mass) transfer characteristics on the blade surface of a high-turning first-stage turbine rotor for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is developed successfully for the measurements of local sublimation depth on the curved surface. In the leading edge region, there is a good agreement between the present heat (mass) transfer data and the previous result on a turbine blade with a moderate turning angle, but come discrepancies are found in the mid-chord heat (mass) transfer between the two results. The local heat (mass) transfer on the present suction surface is greatly enhanced due to an earlier boundary transition, compared with that on a turbine blade with a moderate turning angle, meanwhile there is only a slight change in the pressures-side heat (mass) transfer between the two different turbine rotors. In general, the heat (mass) transfer augmentation by the endwall vortices is found much higher on the suction surface than on the pressure surface

2002-01-01

36

Heat transfer through constant section fins at hear transfer coefficient, changed along the fin height  

International Nuclear Information System (INIS)

[en] Paper presents an analytical solution of the problem to determine the efficiency coefficient of a constant section fin at heat transfer coefficient changing along fin height. It is determined, that the commonly applied assumption about the constancy of a convectional coefficient of heat emission when calculating the efficiency of a fin based on the value of the reduced coefficient of heat emission results in the error reaching 15%. It is shown that to reduce it up to 2-3% when calculating the efficiency coefficient of a fin one should have the experimental values of both the reduced coefficient of heat emission and the convectional coefficient of heat emission at a surface supporting the fins[ru] ???????????? ????????????? ??????? ?????? ??????????? ???????????? ????????????? ????? ??????????? ??????? ??? ?????????? ???????????? ??????????? ?? ?????? ?????. ???????????, ??? ?????? ???????????? ????????? ? ??????????? ????????????? ???????????? ??????????? ??? ??????? ????????????? ????? ?? ???????? ???????????? ???????????? ??????????? ???????? ? ??????, ??????????? 15%. ????????, ??? ??? ?? ???????? ?? 2-3% ??? ??????? ???????????? ????????????? ????? ?????????? ??????????? ???????? ?????????? ?? ?????? ???????????? ???????????? ???????????, ?? ? ????????????? ???????????? ??????????? ?? ???????????, ??????? ?????

2002-01-01

37

Radionuclide transfer to animal products: revised recommended transfer coefficient values  

International Nuclear Information System (INIS)

A compilation has been undertaken of data which can be used to derive animal product transfer coefficients for radionuclides, including an extensive review of Russian language information. The resultant database has been used to provide recommended transfer coefficient values for a range of radionuclides to (i) cow, sheep and goat milk, (ii) meat (muscle) of cattle, sheep, goats, pigs and poultry and (iii) eggs. The values are used in a new IAEA handbook on transfer parameters which replaces that referred to as 'TRS 364'. The paper outlines the approaches and procedures used to identify and collate data, and assumptions used. There are notable differences between the TRS 364 'expected' values and the recommended values in the revised Handbook from the new database. Of the recommended values, three milk values are at least an order of magnitude higher than the TRS 364 values (Cr, Pu (cow) Pu (sheep)) and one milk value is lower (Ni (cow)). For meat, four values (Am, Cd, Sb (beef) I (pork)) are at least an order of magnitude higher than the TRS 364 values and eight values are at least an order of magnitude lower (Ru, Pu (beef), Ru, Sr, Zn (sheep), Ru, Sr (pork), Mn (poultry)). Many data gaps remain.

2009-01-01

38

Mass transfer coefficient: comparison between methods.  

UK PubMed Central (United Kingdom)

The mass transfer area coefficient (MTC) is the best parameter for solute transport evaluation in continuous ambulatory peritoneal dialysis (CAPD) patients. We compared three simplified MTC methods (calculated according Garred, Krediet, or Lindholm) and the peritoneal equilibration test (PET) (Twardowski) to complex MTC (MTCX) (Randerson and Farrell) for urea and creatinine, by means of 29 tests performed in 24 stable CAPD patients. There were no significant differences (paired t-test) between MTCX and each of the simplified MTC, except for creatinine MTC calculated by Krediet's method, which was significantly different (MTCX: 9.36 +/- 4.32, K-MTC: 10.48 +/- 4.55, p < 0.05). Likewise, there was an acceptable correlation between complex MTC and each of the simplified methods including the PET. However, a more detailed study of the MTC's categorizations shows poor agreement with complex MTC categorization. Better results are obtained by PET categorization, which reaches good likelihood ratios either for positive or negative events. We conclude that simplified MTC or the dialysate/plasma ratio at 240 minutes for urea and creatinine has an acceptable correlation with complex MTC and can be useful in clinical practice. There is poor agreement between solute transport categorizations of simplified MTC and complex MTC. There is a better coincidence between the PET (D/P at 240 minutes) and complex MTC categorizations.

Teixidó J; Cofan F; Borrás M; Bonet J; Bonal J; Galimany R; Biosca C; Caralps A

1993-01-01

39

Heat transfer coefficients for drying in pulsating flows  

Energy Technology Data Exchange (ETDEWEB)

Pulsating flows generated by a Rijke type combustor are studied for drying of grains and food particles. It is assumed that the velocity fluctuations are the main factor in the enhancement of the drying process. The heat transfer coefficients for drying in vibrating beds are utilized to estimate the heat transfer coefficients of fixed beds in pulsating and permeating flows and are compared to the steady flow heat transfer coefficients obtained for solid porous bodies, after perturbing the main flow. The cases considered are compared to the convective heat transfer coefficients employed in non-pulsating drying.

Fraenkel, S.L. [DEM/UFRJ, Rio de Janeiro (Brazil); Nogueira, L.A.H. [IEM/EFEI, Itajuba, Minas Gerais (Brazil); Carvalho, J.A. Jr.; Costa, F.S. [LCP/INPE, Cachoeira Paulista, Sao Paulo (Brazil)

1998-05-01

40

Local heat transfer coefficients from the horizontal cylinder  

International Nuclear Information System (INIS)

[en] In this article the experimental investigation of the heat transfer from the smooth horizontal cylinder in the flowing airstream has been shown. Local heat transfer coefficients for the Reynolds numbers ranging from 290 to 1850 have been analysed

1977-01-01

 
 
 
 
41

Overall mass-transfer coefficients in non-linear chromatography  

DEFF Research Database (Denmark)

In case of mass transfer where concentration differences in both phases must be taken into account, one may define an over-all mass-transfer coefficient basd on the apparent over-all concentration difference. If the equilibrium relationship is linear, i.e. in cases where a Henry´s law relationship can be applied, the over-all mass-transfer coefficient will be concentration independent. However, in mass-transfer operations, a linear equilibrium relationship is in most cases not a valid approximation wherefore the over-all mass-transfer coefficient becomes strongly concentration dependent as shown in this paper. In this case one has to discard the use of over-all mass-transfer coefficients and calculate the rate of mass transfer from the two film theory using the appropriate non-linear relationship to calculate the equilibrium ratio at the interface between the two films.

Mollerup, JØrgen; Hansen, Ernst

1998-01-01

42

High-resolution heat-transfer-coefficient maps applicable to compound-curve surfaces using liquid crystals in a transient wind tunnel  

International Nuclear Information System (INIS)

[en] Tests were performed in a transient heat transfer tunnel in which the model under test was preheated prior to allowing room temperature air to be suddenly drawn over the model. The resulting movement of isothermal contours on the model is revealed using a surface coating of thermochromic liquid crystals that display distinctive colors at particular temperatures. A video record is obtained of a temperature and time data pair for all points on the model during a single test. Experiments on a duct model are reported in which the model was preheated using a hot air stream. A manner in which initial model temperature nonuniformities could be taken into account was investigated. The duct model was also tested with a steady-state measurement technique and results were compared with the transient measurements, but recognizing that differences existed between the upstream thermal boundary conditions. The steady-state and transient measurements were shown to be consistent with predicted values. The main advantage of this transient heat transfer technique using liquid crystals is that since the test model need not be actively heated, high-resolution measurements on surfaces with complex shapes may be obtained

1987-01-01

43

Transfer coefficients for plate fin and elliptical tube heat exchangers  

International Nuclear Information System (INIS)

In order to determine transfer coefficients for plate fin and elliptical tube exchangers, mass transfer experiments have been performed using the naphthalene sublimation technique. By means of the heat-mass transfer analogy, the results can be converted to heat transfer results. The transfer coefficients were compared with those for circular tube exchangers and the comparison revealed no major differences. This is a positive outcome, since the use of elliptical tubes may reduce substantially the pressure drop, without affecting the transfer characteristics.(Author)

1981-12-18

44

Heat transfer coefficient for F.E analysis in the warm forging process  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: The Purpose of this paper is to obtain suitable convection and contact heat transfer coefficient forone-time finite element analysis in the warm forging process.Design/methodology/approach: To do this, the temperature of the tool used in the operation was measured witha thermocouple and repeated finite element analysis(FEA) was performed using the experimentally calculatedcontact and cooling heat transfer coefficient. Also the surface temperature of the active tool was obtained bycomparing the measurement and analysis results and finally the contact heat transfer coefficient for one-time FEAwas completed by comparing the surface temperature between the repeated FEA and one-time FEA results.Findings: The acceptable convection heat transfer coefficients are from 0.3 to 0.8N/mm/s/K and the contactheat transfer coefficient of 6~9N/mm/s/K is appropriate for the warm forging process with flow-typelubrication conditions.Practical implications: A comparison of the temperatures from the repeated and one-time analysis allows anoptimum contact heat transfer coefficient for the one time finite element analysis to be determined.Originality/value: Several studies have been conducted with different conditions such as applied pressure andkind of lubricant, but no research has been conducted concerning the convection heat transfer coefficient in thewarm forging process. Also, comparative analysis concerning the reason for difference between experimentallydetermined contact heat transfer coefficient and practically adapted one has not been conducted, yet.

J.H. Kang; K.O. Lee; S.S. Kang

2007-01-01

45

Evaluation of generalized heat transfer coefficients in pilot AFBC units  

Energy Technology Data Exchange (ETDEWEB)

Experimental data for heat transfer rates as obtained in a 0.209m/sup 2/ AFBC unit at the GFETC is examined in the light of the existing four correlations for heat transfer coefficient between an immersed staggered array of horizontal tubes and a gas-solid fluidized bed. The predicted values of heat transfer coefficient from the correlations proposed by Grewal and Bansal are found to be in good agreement with the experimental values of heat transfer coefficient when the contribution due to radiation is also included.

Grewal, N.S.

1981-07-01

46

Measurement technique for local heat transfer coefficients of subchannels of rod bundles using a copper sensor  

International Nuclear Information System (INIS)

This paper is described for the measurement technique for local heat transfer coefficients using a copper sensor in rod bundles with mixing vanes. A copper sensor is defined as the device to measure the convective heat transfer coefficient using constant heat flux and surface temperatures. The copper sensor consists of a cartridge heater and four pieces of thermocouple. The copper sensors located at axial positions of rod bundles are able to measure the local heat transfer coefficients at its positions. The effect of local heated and full heated of copper sensors for rod bundles is investigated using CFD analysis. The decay of local heat transfer coefficients of locally heating condition such as a copper sensor is estimated to be higher value than that of fully heating condition. The calibration curve for local heat transfer coefficients measured is presented.

2008-01-01

47

Enhancement of pool boiling heat transfer coefficients using carbon nanotubes  

International Nuclear Information System (INIS)

In this study, the effect of carbon nanotubes (CNTs) on nucleate boiling heat transfer is investigated. Three refrigerants of R22, R123, R134a, and water were used as working fluids and 1.0 vol.% of CNTs was added to the working fluids to examine the effect of CNTs. Experimental apparatus was composed of a stainless steel vessel and a plain horizontal tube heated by a cartridge heater. All data were obtained at the pool temperature of 7 .deg. C for all refrigerants and 100 .deg. C for water in the heat flux range of 10?80 kW/m2. Test results showed that CNTs increase nucleate boiling heat transfer coefficients for all fluids. Especially, large enhancement was observed at low heat fluxes of less than 30 kW/m2. With increasing heat flux, however, the enhancement was suppressed due to vigorous bubble generation. Fouling on the heat transfer surface was not observed during the course of this study. Optimum quantity and type of CNTs and their dispersion should be examined for their commercial application to enhance nucleate boiling heat transfer in many applications

2007-01-01

48

Boiling Heat Transfer in Falling Film Evaporators with Corrugated Surfaces.  

Science.gov (United States)

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

G. Jansen P. C. Owzarski

1971-01-01

49

Rate Coefficient Determination in Charge Transfer Reactions  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: The development of experimental ion-trap techniques provides the opportunity to compare directly theoretical rate coefficients to experimental data in the low-temperature regime. In the present work, we consider the ion-atom collisional systems, N2+, O2+, Si3+ and Si4+ on a He target, in order to examine the present status of the agreement between theory and experiment.

Marie-Christine Bacchus-Montabonel; Ezinvi Baloïtcha; Michèle Desouter-Lecomte; Nathalie Vaeck

2002-01-01

50

A correlation for mass transfer coefficients in elbows  

Energy Technology Data Exchange (ETDEWEB)

Mass transfer can have a significant effect on corrosion rates depending on the solution chemistry and flow conditions. Therefore, knowledge of the distribution of mass transfer coefficients along the flow geometry can be useful in determining the severity of corrosion rates in situations where mass transfer is a factor. In this investigation, mass transfer in 90 elbows was examined. A computational fluid dynamic (CFD) code was used to model the flow in an elbow and compute mass transfer coefficients. Results were compared to available experimental data to verify the model. Although the number of variables involved in corrosion process is large, only two dimensionless parameters, namely, the flow Reynolds number and the Schmidt number are important for characterizing the mass transfer process. Mass transfer in elbows is also influenced by elbow geometry parameters such as the elbow radius to pipe diameter ratio (r/D). Based on these three dimensionless parameters, mass transfer between the elbow wall and the fluid was simulated and a correlation was developed to predict the maximum elbow mass transfer coefficient as a function of the flow Reynolds number, the Schmidt number and the elbow r/D. This investigation was motivated by a need to predict mass transfer coefficients in elbows for use in conjunction with a comprehensive model for calculating CO{sub 2} corrosion rates in oil and gas pipelines.

Wang, J.; Shirazi, S.A.; Shadley, J.R.; Rybicki, E.F.; Dayalan, E. [Univ. of Tulsa, OK (United States). Dept. of Mechanical Engineering

1998-12-31

51

Measurement of heat transfer coefficients by nuclear magnetic resonance.  

Science.gov (United States)

We demonstrate an experimental method for the measurement of heat transfer coefficient for a fluid system by magnetic resonance imaging. In this method, the temporal variation of thermally induced nuclear shielding is monitored and the average heat transfer coefficient is measured as a function of fluid velocity. We examine the cases of natural convection and forced convection at fluid velocity up to 0.8 m s(-1). These cases correspond to low dimensionless Biot (Bi) number where the heat transfer is limited by thermal convection. We demonstrate the NMR method for two simple geometries, a cylinder and a sphere, to experimentally determine the heat transfer coefficient (h) in two NMR imaging and spectroscopy systems through measuring three NMR parameters, the chemical shift, magnetization and spin self diffusion coefficient. PMID:18524523

Gultekin, David H; Gore, John C

2008-06-03

52

A study on the evaporative heat transfer coefficient in PCCS  

International Nuclear Information System (INIS)

[en] In advanced nuclear reactors, the passive containment cooling has been suggested in AP600 to enhance the safety. The passive cooling has two mechanisms, air natural convection and water cooling with evaporation. To conform the coolability of PCCS, many works have been performed experimentally and numerically. In this study, the water cooling test was performed in scaled down segment type PCCS facility, which have the same configuration with AP600 prototype containment, to obtain the evaporative heat transfer coefficients. In the experiment air-steam mixture temperature and velocity, relative humidity and wall heat flux are measured. The local heat transfer coefficients are calculated and averaged through the vertical plate part of the facility. To convince the measured heat transfer coefficients, an analytical model for the local evaporative heat transfer is developed and compared with experimental data. From the comparison, the predicted coefficients are quite well agreed with measured values

1996-01-01

53

Parametric study of evaporative heat transfer coefficient in solar distillation  

Energy Technology Data Exchange (ETDEWEB)

In this communication, an attempt has been made to study the effect of absorptivity, water depth and bottom heat loss coefficient on the evaporative heat transfer coefficient. The variation of hourly and daily yield with basic variable parameters has been studied. Numerical computations have been carried out for a typical day of Delhi climate. On the basis of numerical results, it is observed that the evaporative heat transfer is a strong function of water depth and absorptivity of the basin as expected. (author)

Kumar, S.; Tiwari, G.N.; Suneja, S. [Indian Institute of Technology, New Delhi (India). Centre for Energy Studies; Rai, S.N. [MMH College, Ghaziabad (India). Physics Dept.

1997-10-01

54

Prediction of film boiling heat transfer coefficients for binary mixtures  

Energy Technology Data Exchange (ETDEWEB)

Film boiling of binary liquid mixtures may be significantly different from that of single-component liquids due to the mass diffusion effect. A theoretical analysis is performed to outline the effects of mass diffusion phenomena on film boiling heat transfer process from a horizontal cylinder heating surface to the binary liquid mixtures of ethylene oxide/water and ethanol/benzene over whole range of compositions. These two binary systems are chosen for illustrating the strong and weak mass diffusion effects, respectively, on film boiling. Furthermore, a simple correlation for predicting heat transfer coefficient is proposed to demonstrate the idea that the dimensionless F factor can satisfactorily account for the mass diffusion effect on film boiling heat transfer of binary mixtures. (orig.). With 9 figs., 1 tab. [Deutsch] Infolge des Stoffdiffusionseffektes kann sich das Filmsiedeverhalten binaerer Fluessigkeitsgemische ganz wesentlich von dem der Einzelkomponentenfluide unterscheiden. In einer theoretischen Studie sollen die Einfluesse der Stoffdiffusionsphaenomene auf den Waermeuebergang beim Filmsieden untersucht werden, und zwar bezueglich einer horizontalen zylindrischen Heizflaeche, die Waerme an die Binaergemische Ethylenoxid/Wasser und Ethanol/Benzol bei beliebigen Konzentrationsverhaeltnissen abgibt. Die beiden Binaersysteme wurden ausgewaehlt, um einmal starken und dann schwachen Einfluss des Stoffdiffusionseffektes auf das Filmsieden zu zeigen. Schliesslich wird eine einfache Korrelationsbeziehung zur Berechnung von Waermeuebergangskoeffizienten vorgeschlagen, die darlegen soll, dass der dimensionslose F-Faktor geeignet ist, den Einfluss des Stoffdiffusionseffektes auf das Filmsieden binaerer Gemische befriedigend zu beruecksichtigen. (orig.)

Liu Mingjuei [Chemical Engineering Dept., National Cheng Kung Univ., Tainan (Taiwan, Province of China); Yang Yumin [Chemical Engineering Dept., National Cheng Kung Univ., Tainan (Taiwan, Province of China); Maa Jerru [Chemical Engineering Dept., National Cheng Kung Univ., Tainan (Taiwan, Province of China)

1997-04-01

55

Effect of specimen geometry on heat transfer coefficient of rubber to air  

Directory of Open Access Journals (Sweden)

Full Text Available It is widely known that the heat transfer coefficient is not material specific but, on the contrary, it depends on several factors such as surface appearance, suface emissivity, fluid velocity and specimen geometry. In this study, the effect of geometry on heat transfer coefficient of rubber to air was investigated. Determination of heat transfer coefficient was undertaken by an indirect method, namely Finite Element Analysis (FEA). With this method, the best value of heat transfer coefficient was determined by matching results obtained from simulation with those obtained experimentally, by observing the temperature changes at any point in the specimen as a function of time. Two rubber compounds were selected for this study; CB-filled NR and CB-Filled SBR. For each compound, rubber specimens with various geometries (i.e., sphere, cylinder and bar) were prepared and studied. Results have shown that both compounds possess approximately the same value of heat transfer coefficient. Regardless of the rubber type, heat transfer coefficient is affected by specimen geometry and is found in the order of sphere ? cylinder > bar. However, the effect of geometry on heat transfer coefficient is not pronounced and based on engineering judgment it can be ignored.

Pongdhorn Sae-oui

2000-01-01

56

The use of steady state heat transfer coefficients in transient calculations  

International Nuclear Information System (INIS)

It is generally not possible to develop fully time-variant analyses for rapid changes of conditions within a reactor. This leads to the use of steady state heat transfer coefficients as an approximation in such calculations. Criteria are set for the validity of using these steady-state heat transfer coefficients in transient calculations. In particular, criteria are given for using a steady state coefficient during a rapid decrease in heat flux. The analysis is based on a solution of the energy equation given by Stein (1971) for a heat flux which is both axially and time dependent. Criteria are given both for smooth and roughened heat transfer surfaces. It is demonstrated that use of the steady state heat transfer coefficient is valid for a set of prescribed AGR conditions. Consideration has been given to the more difficult case of rapid changes in coolant velocity. (U.K.)

1980-01-01

57

Heat transfer coefficient in serpentine coolant passage for CCDTL  

Energy Technology Data Exchange (ETDEWEB)

A series of heat transfer experiments were conducted to refine the cooling passage design in the drift tubes of a coupled cavity drift tube linac (CCDTL). The experimental data were then compared to numerical models to derive relationships between heat transfer rates, Reynold`s number, and Prandtl number, over a range of flow rates. Data reduction consisted of axisymmetric finite element modeling where the heat transfer coefficients were modified to match the experimental data. Unfortunately, the derived relationship is valid only for this specific geometry of the test drift tube. Fortunately, the heat transfer rates were much better (approximately 2.5 times) than expected.

Leslie, P.; Wood, R.; Sigler, F.; Shapiro, A.; Rendon, A.

1998-12-31

58

Experimental evaluation of heat transfer coefficients between radiant ceiling and room  

DEFF Research Database (Denmark)

The heat transfer coefficients between radiant surfaces and room are influenced by several parameters: surfaces temperature distributions, internal gains, air movements. The aim of this paper is to evaluate the heat transfer coefficients between radiant ceiling and room in typical conditions of occupancy of an office or residential building. Internal gains were therefore simulated using heated cylinders and heat losses using cooled surfaces. Evaluations were developed by means of experimental tests in an environmental chamber. Heat transfer coefficient may be expressed separately for radiation and convection or as one total parameter, but this choice may lead to different considerations about thermal performance of the system. In order to perform correct evaluations, it is therefore extremely important to use the proper reference temperature. The obtained values confirm tendencies found in the literature, indicating limitations and possibilities of radiant ceiling systems improvement.

Causone, Francesco; Corgnati, Stefano P.

2009-01-01

59

Experimental and Numerical Study on Effects of Airflow and Aqueous Ammonium Temperature on Ammonia Mass Transfer Coefficient  

DEFF Research Database (Denmark)

This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 × 104 to 5.43 × 104 (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related.

Rong, Li; Nielsen, Peter V.

2010-01-01

60

Heat transfer coefficients under LOCA conditions in containment buildings  

International Nuclear Information System (INIS)

A model to calculate local heat transfer coefficients between the containment atmosphere and the walls of a pressurized water reactor containment building after a loss-of-coolant accident has been developed. The new calculation is based on the containment wall and atmosphere bulk temperatures, mass ratio of steam to air, and condensing or convective heat transfer conditions. Comparison with the Carolinas Virginia Tube Reactor Containment Tests shows good agreement. The model has been implemented into the containment code TECAR. (orig.)

1981-01-01

 
 
 
 
61

3D measurements and numerical computations of heat transfer coefficients on spheres in an array  

International Nuclear Information System (INIS)

[en] The focus of this paper is to investigate the heat transfer coefficient distributions on the spheres in a three-dimensional (3-D) array. This arrangement is an essential geometry in pebble bed reactors (PBRs) that are generally adopted in the chemical and the nuclear engineering. Understanding the thermal-hydraulic characteristics of the pebbles is important for the design of reactors. Using the transient liquid crystal technique, an experimental device is set up to measure the transient wall temperature on the surface of spheres arranged in an array, as heated air flows across. Based on the measured temperature distributions on the sphere surfaces, the heat transfer coefficient can be derived. A 3-D transient computational fluid dynamics (CFD) model with different turbulence models is also developed and assessed using the measured heat transfer coefficient distributions. Five turbulence models are considered in this study: the standard k-? low-Re, AKN k-? low-Re, standard k-? two-layer, realizable k-? two-layer, and v2-bar-f turbulence models, respectively. Comparisons of the predicted heat transfer coefficient distributions and those in the experimental data reveal that the v2-bar-f turbulence model is more suitable for simulating flow and heat transfer characteristics in a sphere array. In addition, the beneficial effect of Rein on the heat transfer coefficient distribution is captured by both experimental measurements and CFD predictions. (authors)

2013-01-01

62

Determination of the wall heat transfer coefficient in pebble beds  

International Nuclear Information System (INIS)

The prediction of the temperature distribution in a packed bed requires the knowledge of the effective thermal conductivity in the core and the wall heat transfer coefficient. Empirical correlations published previously yield strongly differing results varying by a factor of ten at low Reynolds numbers. Very high Reynolds numbers had not yet been investigated. Wall heat transfer coefficients in pebble beds were achieved by applying the analogy between heat and mass transfer on sublimation of napthalene into air. The use of mass transfer instead of heat transfer techniques provides some advantages concerning secondary effects. Two series of tests applying napthalene mass transfer were performed in the ranges of Reynolds number 5x101 ? Re ? 6x103 and 2x103 ? Re ? 2x104. Moreover, the mass transfer in the inlet section was investigated. The results of both test series match well. A good agreement is observed with earlier published data, which were not affected by entrance effects. The data are correlated for the range of Reynolds numbers 5x101 ? Re ? 2x104. The transition effect observed at Re ? 4x103 is explained by a change of the flow structure. A correlation is given for the mass and heat transfer in the entrance section. (orig.).

1986-01-01

63

Multicomponent NAPL source dissolution: evaluation of mass-transfer coefficients.  

UK PubMed Central (United Kingdom)

Mass transfer rate coefficients were quantified by employing an inverse modeling technique to high-resolution aqueous phase concentration data observed following an experimental release of a multicomponent nonaqueous phase liquid (NAPL) at a field site. A solute transport model (SEAM3D) was employed to simulate advective-dispersive transport over time coupled to NAPL dissolution. Model calibration was demonstrated by accurately reproducing the observed breakthrough times and peak concentrations at multiple observation points, observed mass discharge at pumping wells, and the reported mass depletions for three soluble NAPL constituents. Vertically variable NAPL mass transfer coefficients were derived for each constituent using an optimized numerical solute transport model, ranging from 0.082 to 2.0 day(-1) across all constituents. Constituent-specific coefficients showed a positive correlation with liquid-phase diffusion coefficients. Application of a time-varying mass transfer coefficient as NAPL mass depleted showed limited sensitivity during which over 80% of the most soluble NAPL constituent dissolved from the source. Long-term simulation results, calibrated to the experimental data and rendered in terms of mass discharge versus source mass depletion, exhibited multistage behavior.

Mobile MA; Widdowson MA; Gallagher DL

2012-09-01

64

Heat transfer coefficient at minimum fluidization velocity for gas-solid fluidized beds  

Energy Technology Data Exchange (ETDEWEB)

A semi-empirical correlation for heat transfer coefficients between dense gas-solid quiescent fluidized beds and surfaces is presented. Surface heat transfer coefficients at the minimum fluidization condition were measured using a local heat transfer probe in a 5 cm x 30 cm transparent walled, fluidized bed. The initial bed height was held constant at 17.0 cm in all cases. The powders tested were glass, sand, graphite, polypropylene and aluminum with sizes in the range from 25 {micro}m to 1789 {micro}m. The fluidizing medium used was air with the bed operated at atmospheric temperature and pressure. Two different distributor plates were utilized during the experiments, i.e., sintered and perforated distributor plate. Time average, local heat transfer coefficients acquired were averaged over repeated measurements at different times. An empirical correlation for the surface heat transfer coefficient at minimum fluidization conditions, was provided by regressing the 16 data points: Nu = 1.666 Pe{sup 0.553}, for 0.01 {lt} Pe {lt} 100, where the Nusselt number, Nu = (h{sub bs} d{sub p}/k{sub g}) and the Peclet number, Pe = (U{sub mf} d{sub p}/{alpha}{sub g}). The Peclet number effects are accounted for in the equations for heat transfer with diffusion and convection. The resulting expression from the energy balance equation is: Nu = ({radical} Pe/{pi}).

Sharma, K.R.

1999-07-01

65

Dissociation and Mass Transfer Coefficients for Ammonia Volatilization Models  

Science.gov (United States)

Process-based models are being used to predict ammonia emissions from manure sources, but their accuracy has not been fully evaluated for cattle manure. Laboratory trials were conducted to measure the dissociation and mass transfer coefficients for ammonia volatilization from media of buffered ammon...

66

Local heat transfer coefficient for turbulent flow in rod bundles  

International Nuclear Information System (INIS)

[en] The correlation of the local heat transfer coefficients in heated triangular array of rod bundles, in terms of the flow hydrodynamic parameters is presented. The analysis is made first for fluid with Prandtl numbers varying from moderated to high (Pr>0.2), and then extended to fluids with low Prandtl numbers (0.004

1983-01-01

67

Mathematical relationship between surface emission and diffusion coefficients  

Energy Technology Data Exchange (ETDEWEB)

This paper analyzes the surface emission coefficient corresponding to any diffusion coefficient expressed as an exponential function of the concentration of diffusing substance in capillary porous solids. Theoretical equations for surface emission coefficient for both sorption and desorption are presented. Procedures to derive the diffusion coefficient and to verify the corresponding surface emission coefficient are made using experimental sorption data of aspen (Populus sp.) wood. It is of interest to note that the theoretical models for diffusion and surface emission coefficients can be established and/or evaluated using the same set of experimental data.

Liu, J.Y.; Simpson, W.T. [Forest Service, Madison, WI (United States). Forest Products Lab.

1996-05-01

68

Boiling heat transfer intensity on small-size surface  

Directory of Open Access Journals (Sweden)

Full Text Available Dependence of heat-release surface of heat carrier (water and ethanol) characteristic size, boundary conditions and thermophysical properties on boiling heat transfer intensity on small-size surface was investigated. Criterion equation for boiling heat transfer coefficients on small-size surface was obtained.

Alekseik O. S.; Kravets V. Yu.; Kopchevskaya I. A.

2012-01-01

69

Microscale surface modifications for heat transfer enhancement.  

Science.gov (United States)

In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process. PMID:24003985

Bostanci, Huseyin; Singh, Virendra; Kizito, John P; Rini, Daniel P; Seal, Sudipta; Chow, Louis C

2013-09-19

70

Microscale surface modifications for heat transfer enhancement.  

UK PubMed Central (United Kingdom)

In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create microscale indentations, while the other used plasma spray coating to create microscale protrusions on Al 6061 (aluminum alloy 6061) samples. The test surfaces were characterized using scanning electron microscopy (SEM) and confocal scanning laser microscopy. Because of the surface modifications, the actual surface area was increased up to 2.8× compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm(2) representing a thermal management setting for high power systems. Experimental results showed that the microscale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm(2) compared to the smooth surface and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.

Bostanci H; Singh V; Kizito JP; Rini DP; Seal S; Chow LC

2013-10-01

71

Estimation of local temperature dependent heat transfer coefficient for dynamic thermal analysis of electronic circuits  

International Nuclear Information System (INIS)

The value of the surface heat transfer coefficient depends strongly on temperature. This phenomenon is one of the main sources of nonlinearities arising in the dynamic thermal simulation of electronic systems. This paper presents the problem of estimating the temperature dependence of this coefficient based on a practical example of a hybrid circuit. The estimation is carried out by the coupling of the forward Green's function solver with the inverse solver using the modified Landweber iteration.

2008-11-01

72

Transfer coefficients of radionuclides from feed to livestock products  

International Nuclear Information System (INIS)

The accumulation of data on radionuclide transfer are poor in Japan and those are limited to 90Sr, 137Cs and 131I released from the previous atomic bomb experiments. However, in Europe, intensive studies on environment RI level which affects the restriction of the intake for meats and milk products have been made as the measures against the environment radioactivity due to Chernobyl accident. The transfer coefficients of radionuclides to meats and milk products were estimated on a basis of the data published in the Science of the Total Environment vol.85(1989), Oxford University and CEC Radiation Protection, EUR 12608 EN, Luxembourg, 1990 in addition to the data on Exclusion of Radioactivity from foods, Environment Parameter, series No. 4. On the other hand, the transfer coefficients for Japanese were estimated using the concerned data from published reports and the environment radioactivity data reported by national and local government bodies. In this book, many new data of transfer coefficient are presented in tables along with the previous data collected by international nuclear energy agencies and respective national facilities concerned. (M.N.).

1995-01-01

73

Mass Transfer Coefficient Studies in Bubble Column Reactor  

Directory of Open Access Journals (Sweden)

Full Text Available Stirred bubble column are widely used in chemical and allied processes industries. Stirred bubble column reactor promotes significant liquid hold-up and long liquid residence time. It is used when a large mass transfer area and high mass transfer coefficient in both phases are desired. These columns can operate continuously with a concurrent and counter current phase flow where high interfacial areas between phases are possible with low investment cost. An experimental work was undertaken to focus the effect of various parameters like Height to Diameter ratio (H/D), Gas flow rate and Speed of the stirrer (N) on mass transfer coefficient in stirred bubble column reactor. For this purpose, experiments were conducted in 0.14 m i.d column having 2 m height. The column with ring sparger having 67% active area is used as sparger for dispersing the dispersed phase into the continuous phase. For the optimized sparger plate, the effect of various parameters on mass transfer coefficient was studied based on CO2 –absorption Technique.

D. Devakumar; K. Saravanan; T. Kannadasan; B. Meenakshipriya

2010-01-01

74

Air sparging: Prediction of air-water mass transfer coefficients  

Energy Technology Data Exchange (ETDEWEB)

One of the difficulties with the application of air sparging as a remedial technology is that not much is known about the physical-chemical processes during air sparging. This study presents information on the air-water mass transfer of volatile organic compounds (VOCs) under air sparged conditions. The mass transfer coefficients were estimated using a single air channel experimental setup, where a thin channel of air (approx. 1.5 mm) was allowed to flow over saturated VOC-contaminated soil. The experimental setup allowed VOC concentrations in both liquid and gas phases to be measured. Eleven VOCs and three different porous media with mean particle size 0.168 mm, 0.190 mm, and 0.305 mm were used in the experiments. Air velocities ranged between 0.2 cm/s and 2.5 cm/s. Air-water mass transfer coefficients were estimated by fitting experimental data with an advection-diffusion model. The model assumed the existence of an aqueous phase influence zone (called the mass transfer zone (MTZ)) surrounding the air channel in which VOCs present were directly impacted by the air flow. The size of the influence zone was found to be a function of the physical-chemical characteristics of the porous media and the VOCs. The estimated liquid side lumped air-water mass transfer coefficients (K{sub L}a) were found to range from 2.6 x 10{sup {minus}5} to 2.4 x 10{sup {minus}4} min{sup {minus}1}. An empirical model was developed by correlating the modified Sherwood number with the air phase Peclet number. Henry's law constant, normalized particle size, and uniformity coefficient of the porous media.

Braida, W.J.; Ong, S.K.

1998-07-01

75

Uncertainty of evaluations of flow film boiling heat transfer coefficient  

International Nuclear Information System (INIS)

[en] The results of evaluations of the heat transfer coefficient (?s) for the flow film boiling (FFB) region received by two approaches, which are complemented each other are discussed here. In particular, they are as follows: 1) using empirical or semiempirical correlations, 2) developing the look-up tables (LUT). There is a need to distinguish two FFB heat transfer regime, such as 1) the post-dryout (PDO) heat transfer and 2) before critical heat flux (CHF) heat transfer. A new version of the LUT for ?s is presented at forced water flow in long tubes uniformly heated. It covers the following range of parameters: pressure 0.1/20 MPa; mass flux 250/3000 kg/m2·s; quality (-0.2)/2.2; heat flux 0.2/1.0 MW/m2; tube diameter 10 mm. The values of the FFB heat transfer coefficient in the LUT are marked by different methods depending on the used calculation method. Four methods were applied to develop the LUT for ?s, namely: 1) averaging experimental data, 2) calculations on the base of the Sergeev model, 3) using data from the LUT developed by Leung L. et al. (1997), 4) using both interpolation and extrapolation beyond the range of experimental data and theoretical evaluations. The calculated errors of the ?s values were obtained by comparison the LUT data with the experimental data stored in the database of the IPPE Thermophysical Data Center. (author)

2000-01-01

76

Heat transfer coefficient for lead matrixing in disposal containers for used reactor fuel  

International Nuclear Information System (INIS)

[en] In the Canadian Nuclear Fuel Waste Management Program, metal matrices with low melting points are being evaluated for their potential to provide support for the shell of disposal containers for used fuel, and to act as an additional barrier to the release of radionuclides. The metal matrix would be incorporated into the container by casting. To study the heat transfer processes during solidification, a steady-state technique was used, involving lead as the cast metal, to determine the overall heat transfer coefficient between the lead and some of the candidate container materials. The existence of an air gap between the cast lead and the container material appeared to control the overall heat transfer coefficient. The experimental observations indicated that the surface topography of the container material influences the heat transfer and that a smoother surface results in a greater heat transfer than a rough surface. The experimental results also showed an increasing heat transfer coefficient with increasing temperature difference across the container base plates; a model developed to base-plate bending can explain the observed results

1985-01-01

77

Heat transfer coefficients for lead matrixing in disposal containers for used reactor fuel  

Energy Technology Data Exchange (ETDEWEB)

In the Canadian Nuclear Fuel Waste Management Program, metal matrices with low melting points are being evaluated for their potential to provide support for the shell of disposal containers for used fuel, and to act as an additional barrier to the release of radionuclides. The metal matrix would be incorporated into the container by casting. To study the heat transfer processes during solidification, a steady-state technique was used, involving lead as the cast metal, to determine the overall heat transfer coefficient between the lead and some of the candidate container materials. The existence of an air gap between the cast lead and the container material appeared to control the overall heat transfer coefficient. The experimental observations indicated that the surface topography of the container material influences the heat transfer and that a smoother surface results in greater heat transfer than a rough surface. The experimental results also showed an increasing heat transfer coefficient with increasing temperature difference across the container base plates; a model developed for base-plate bending can explain the observed results. 8 references, 12 figures, 3 tables.

Mathew, P.M.; Taylor, M.; Krueger, P.A.

1985-02-15

78

Semi-empirical model for heat transfer coefficient in liquid metal turbulent flow  

International Nuclear Information System (INIS)

[en] The heat transfer by forced convection in a metal liquid turbulent flow for circular ducts is analyzed. An analogy between the momentum and heat in the wall surface, is determined, aiming to determine an expression for heat transfer coefficient in function of the friction coefficient. (E.G.)[pt] Analisa-se transferencia de calor em conveccao forcada de escoamento turbulento de metais liquidos em dutos circulares. E desenvolvida uma analogia entre quantidade de movimento e calor na superficie da parede, para determinar-se uma expressao do coeficiente de troca de calor em funcao do coeficiente de atrito. (Autor)

1982-01-01

79

MASS TRANSFER COEFFICIENT EVALUATION FOR PILOT SCALE FERMENTER USING SODIUM SULPHITE OXIDATION METHOD  

Directory of Open Access Journals (Sweden)

Full Text Available An adequate supply of oxygen in aqueous solution becomes the focal point of interest when it comes to the growth and maintenance of most aerobic microbial and tissue cultures used for biochemical and pharmaceutical production. Unfortunately, oxygen mass transfer to the growth medium serves as a major growth limiting factor owing to it’s low solubility in aqueous solutions. (Approximately 10 ppm at ambient temperature and pressure). The reaction rate is such that as oxygen enters the liquid phase, it is immediately consumed to oxidize the sulfite so that the rate of oxidation equals that of the oxygen transfer. Oxygen must at first be transferred from gas bulk through a series of steps onto the surfaces of cells before it can be utilized. Therefore the enhancement of gas-liquid mass transfer during aerobic cultures and fermentations is always put into priority. The present study involves using the ‘Central Composite Design’, a statistical technique to determine the parametric conditions for the optimum volumetric mass transfer coefficient in a pilot scale (40L) fermenter. The optimum volumetric mass transfer coefficient was found to lie outside the range of parameters studied and analytical expressions was obtained to predict the volumetric mass transfer coefficients for the parameter ranges studied using response surface methodology. The analytical expression was addressed to be significantly valid based on ANOVA results.

Rajesh Ghosh* and Sounak Bhattacherjee

2013-01-01

80

Measurement and modeling of interface heat transfer coefficients  

International Nuclear Information System (INIS)

[en] The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m2/K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, epsilon = 0.2, of the solidified metal

1985-01-01

 
 
 
 
81

Convection heat transfer coefficients at convective drying of porous materials  

Energy Technology Data Exchange (ETDEWEB)

Measurements proved that the convective heat transfer coefficient (h) has a larger value h{sub wet} at the constant drying rate period and after that it falls down to a minimum one: h{sub dry} in the equilibrium dried state. Measurements showed also that the heat of vaporization in the last phase of the falling drying rate period is far greater than it was in the constant drying rate period. The first measurements were made on a gypsum plate. Afterwards the authors carried out measurement research with fine glass powder and cement-perlite plate and determined h{sub wet} and h{sub dry} heat transfer coefficients as a function of Reynolds number. All of these measurements confirmed the conclusion that h{sub wet} is far greater than h{sub dry}.

Szentgyoergyi, S.; Toemoesy, L.; Molnar, O.

2000-07-01

82

Measurement and modeling of interface heat transfer coefficients  

Energy Technology Data Exchange (ETDEWEB)

The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/mS/K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, epsilon = 0.2, of the solidified metal.

Rollett, A.D.; Lewis, H.D.; Dunn, P.S.

1985-01-01

83

A model of the interfacial heat-transfer coefficient during unidirectional solidification of an aluminum alloy  

Energy Technology Data Exchange (ETDEWEB)

A model is presented for the prediction of the interfacial heat-transfer coefficient during the unidirectional solidification vertically upward of an Al-7 wt pct Si alloy cast onto a water cooled copper chill. It has been experimentally determined that the casting surfaces were convex toward the chill, probably due to the deformation of the initial solidified skin of the casting. The model was, therefore, based upon a determination of the (macroscopic) nominal contact area between the respective rough surfaces and, within this region, the actual (microscopic) contact between the casting and the chill surfaces. The model produced approximate agreement with both experimentally determined values of the heat-transfer coefficient and the measured curvature of the casting surface and showed a reasonable agreement with measured temperatures in the casting and the chill also. A common experimental technique for the experimental determination of the heat-transfer coefficient involves the assumption of one-dimensional heat transfer only. An implication of the approach adopted in this model is that the heat transfer in the region of the casting-chill interface may be two-dimensional, and the subsequent error in the experimentally determined values is discussed.

Griffiths, W.D.

2000-04-01

84

INFLTB, Dosimetric Mass Energy Transfer and Absorption Coefficient  

International Nuclear Information System (INIS)

1 - Description of program or function: INFLTB calculates mass energy transfer and mass energy absorption coefficients between 1 keV and 100 MeV for 29 elements and 14 mixtures and compounds of general dosimetric interest. Elements: hydrogen, helium, lithium, beryllium, carbon, graphite, nitrogen, oxygen, fluorine, neon, aluminum, silicon, sulfur, argon, calcium, titanium, iron, copper, germanium, krypton, molybdenum, tin, iodine, barium, gadolinium, tungsten, platinum, uranium, silver, lead. Mixtures and compounds: A-150 tissue-equivalent plastic, adipose tissue (ICRP), adipose tissue (ICRU, 1986), air, dry (near sea level), bone, compact (ICRU), bone, cortical (ICRP), bone, cortical (ICRU, 1986), calcium fluoride, calcium fluoride, ferrous sulfate (standard Fricke) dosimeter solution, ferrous sulfate ('super' Fricke) dosimeter solution, glass, borosilicate ('Pyrex', corning 7740), lithium fluoride, muscle, skeletal (ICRP), muscle, skeletal (ICRU, 1986), muscle, striated (ICRU), polyethylene, polymethyl methacrylate, 'Lucite', 'Perspex', 'Plexiglas', polystyrene, polytetrafluoroethylene, 'Teflon', water, liquid, water vapor, Te gas(methane). 2 - Method of solution: The mass energy transfer coefficient is calculated from the sum of the interaction cross sections (atomic photo effect, Compton scattering, and pair plus triplet production) multiplied by their respective average fractions of energy transferred to electrons and positrons. The mass energy absorption coefficient is the product of the mass energy transfer coefficient and 1 - G, where G is the average fraction of the secondary electron (or positron) kinetic energy that is spent in Bremsstrahlung production and in-flight positron annihilation. 3 - Restrictions on the complexity of the problem: Photon source energies are limited to values between 1 keV and 100 MeV. Radiation yield files are available only for 29 element and 14 compounds and mixtures

1997-01-01

85

Measurement of impingement heat transfer coefficient on a HIPS liner sheet  

Energy Technology Data Exchange (ETDEWEB)

A test facility was built to measure the impingement convective heat transfer coefficient for a high impact polystyrene (HIPS) liner sheet which was heated by an array of air slot nozzles. A HIPS liner sheet having a thickness of 6 mm is a typical material used for inside shells of refrigerators. The nozzle geometry was optimally designed. The pressure drops through the nozzles, the velocities at the exits of nozzles, temperatures on the sheet surface and in the sheet center were measured. The impingement heat transfer coefficient on the sheet was determined using the measured sheet temperature history in conjunction with an inverse analysis which was based on a one-dimensional transient heat conduction model. The effect of air flow rate ranging from 8 to 32 m/s on the heat transfer coefficient is discussed.

Fu, X.

1999-07-01

86

Evaluation of heat transfer coefficient at direct contact condensation of cold water and steam  

International Nuclear Information System (INIS)

[en] The estimation of heat transfer coefficient at the direct contact condensation of cold water and steam is very hard, since the phenomena is unsteady and the interface moves complicately. Present research shows the heat transfer coefficient evaluated in the simulation analyses and experiments on the phenomena related to the Loss-of-Coolant Accident of light water reactors. At chugging the heat transfer coefficient was up to 106W/m2K. At condensation oscillation it was between 105-106 W/m2K. At jet region of cold water injected into steam flow it was around 105 W/m2K, and the surface of stratified flow it was between 104-5 x 104 W/m2K. (author)

1988-01-01

87

Calculation of the mass transfer coefficient for the combustion of a carbon particle  

Energy Technology Data Exchange (ETDEWEB)

In this paper we address the calculation of the mass transfer coefficient around a burning carbon particle in an atmosphere of O{sub 2}, N{sub 2}, CO{sub 2}, CO, and H{sub 2}O. The complete set of Stefan-Maxwell equations is analytically solved under the assumption of no homogeneous reaction in the boundary layer. An expression linking the oxygen concentration and the oxygen flux at the particle surface (as a function of the bulk gas composition) is derived which can be used to calculate the mass transfer coefficient. A very simple approximate explicit expression is also given for the mass transfer coefficient, that is shown to be valid in the low oxygen flux limit or when the primary combustion product is CO{sub 2}. The results are given in terms of a correction factor to the equimolar counter-diffusion mass transfer coefficient, which is typically available in the literature for specific geometries and/or fluid-dynamic conditions. The significance of the correction factor and the accuracy of the different available expressions is illustrated for several cases of practical interest. Results show that under typical combustion conditions the use of the equimolar counter-diffusion mass transfer coefficient can lead to errors up to 10%. Larger errors are possible in oxygen-enriched conditions, while the error is generally low in oxy-combustion. (author)

Scala, Fabrizio [Istituto di Ricerche sulla Combustione - CNR, P.le Tecchio 80, 80125 Napoli (Italy)

2010-01-15

88

Rewetting of a finite rod an arbitrary space-dependent heat transfer coefficient  

International Nuclear Information System (INIS)

[en] Two-dimensional rewetting models usually assume two or three regions, with different boundary conditions specified at the solid surface. The more advanced analytical solutions by eigenfunction expansions obtain a formed expression of the temperature distribution in each sub region with a constant heat transfer coefficient. This expression contains some, yet, unknown constants which are determined by matching the temperatures and their axial gradients at the interface between adjacent sub domains. As far as we know, to date there does not exist an analytical solution of a rewetting model with an arbitrary space-dependent heat transfer coefficient. Moreover, eigenfunction expansions solutions of models with a discontinuous heat transfer coefficient have been shown to impede convergence of the series and to decrease the solution accuracy. In the present study, we solve by eigenfunction expansions a two-dimensional model of rewetting of a finite length slab or cylindrical rod, with an arbitrary space-dependent heat transfer coefficient. The unique features of the present approach are the simplicity of the solution, which does not necessitates a tedious splitting of the solution domain into sub domains, and avoiding the convergence problem associated with cases of discontinuous heat transfer coefficients. (authors); 5 refs

1994-01-01

89

Heat transfer over an unsteady stretching surface  

Energy Technology Data Exchange (ETDEWEB)

Similarity solution of the laminar boundary layer equations corresponding to an unsteady stretching surface have been studied. The governing time-dependent boundary layer are transformed to ordinary differential equations containing Prandtl number and unsteadiness parameter. The effect of various govern-ing parameters such as Prandtl number and unsteadiness param-eter which determine the velocity and temperature profiles and heat transfer coefficient are studied. (orig.)

Elbashbeshy, E.M.A. [Ain Shams University, Faculty of Science, Department of Mathematics, Cairo (Egypt); Bazid, M.A.A. [Suez Canal University, Faculty of Education, Department of Mathematics, El-Arish (Egypt)

2004-11-01

90

Enhancement of Volumetric Mass Transfer Coefficient for Oxygen Transfer Using Fe2O3-Water Nanofluids  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Experiments were carried out with Fe2O3-water nanofluids to study possible enhancement in volumetric mass transfer coefficient for transfer of oxygen from air bubble to nanofluid, in an agitated, aerated bioreactor. The nanoparticles concentration was varied in the range of 0.0...

S. Manikandan; N. Karthikeyan; K.S. Suganthi; K.S. Rajan

91

The Tube Side Heat Transfer Coefficient for Enhanced Double Tube by Wilson Plot Analysis  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of the investigation presented in this study is to evaluate the tube side single phase heat transfer performance on the EXTEK (Twisted Multi-Head) tube. The geometry of the cross-section for a flow passage has an effect on its convective heat transfer capabilities. For concentric annuli in a double tube heat exchanger, the annular surface enhancement and tube profile enhancement play an important role. EXTEK (Twisted Multi-Head) uses twisted extrusion of a star shape tube for tube profile enhancement. The study was able to develop individual heat transfer coefficient correlations for this new method of enhancement for the turbulent flow regimes. A plain annulus was also investigated for comparison. The Wilson plot method was used to determine the tube side heat transfer coefficients from which the Nusselt type correlations were developed.

Tiruselvam Ramahlingam; Vijay R. Raghavan

2011-01-01

92

A correlation to the heat transfer coefficient in nucleate boiling  

International Nuclear Information System (INIS)

[en] Nucleate boiling heat transfer is a complex phenomenon, making the development of a correlation for the heat transfer coefficient rather cumbersome due to the number of physical parameters involved in it. Some authors have followed a pragmatic approach to the problem by correlating the heat transfer coefficient in terms of reduced primitive properties. Two of the most knowledgeable authors who have followed this approach are Gorenflo and Cooper. Comparisons have been performed among results from the correlations proposed by these researchers and experimental results obtained elsewhere for refrigerants R-11, R-113 and R-114. These comparisons have shown that Cooper's correlation is best fitted for halocarbon refrigerants. The correlation proposed by Gorenflo ads the difficulty of including a numerical factor specific for each fluid. Leiner modified Gorenflo's correlation to determine the numerical factor as a function of known physical parameters of the fluid. In present study, the form of this function has been investigated for halocarbon refrigerants. The obtained correlation is written in terms of the following parameters: reduced pressure, eccentric and compressibility factors at the critical state, and a dimensionless specific heat of the vapor phase. The correlation compares well with experimental results. (author)

1999-01-01

93

Resonant charge transfer at dielectric surfaces  

CERN Multimedia

We report on the theoretical description of secondary electron emission due to resonant charge transfer occurring during the collision of metastable nitrogen molecules with dielectric surfaces. The emission is described as a two step process consisting of electron capture to form an intermediate shape resonance and subsequent electron emission by decay of this ion, either due to its natural life time or its interaction with the surface. The electron capture is modeled using the Keldysh Green's function technique and the negative ion decay is described by a combination of the Keldysh technique and a rate equation approach. We find the resonant capture of electrons to be very efficient and the natural decay to be clearly dominating over the surface-induced decay. Secondary electron emission coefficients are calculated for aluminum oxide, magnesium oxide, silicon oxide, and diamond at several kinetic energies of the projectile. With the exception of magnesium oxide the coefficients turn out to be of the order of...

Marbach, Johannes; Fehske, Holger

2012-01-01

94

Local heat transfer coefficient in a fluidized bed  

International Nuclear Information System (INIS)

[en] This paper presents an experimental study for the local heat transfer coefficient. The experiments was conducted inside a reactor with inner diameter (I D = 142mm) at atmospheric conditions (temperature mean value = 29 deg.) The bed was heated by means of a parochial electric heater with a diameter of (dh = 29 mm) and a constant power of 5W. The following factors varied: particles type and diameter, fluid velocity, bed height and heater position inside the reactor. The results were presented and discussed. (author). 15 refs., 7 figs

1999-01-01

95

Experimental determination of correlations for average heat transfer coefficients in heat exchangers on both fluid sides  

Science.gov (United States)

This paper presents an experimental-numerical method for determining heat transfer coefficients in cross-flow heat exchangers with extended heat exchange surfaces. Coefficients in the correlations defining heat transfer on the liquid- and air-side were determined based on experimental data using a non-linear regression method. Correlation coefficients were determined from the condition that the weighted sum of squared liquid and air temperature differences at the heat exchanger outlet, obtained by measurements and those calculated, achieved minimum. Minimum of the sum of the squares was found using the Levenberg-Marquardt method. The uncertainty in estimated parameters was determined using the error propagation rule by Gauss. The outlet temperature of the liquid and air leaving the heat exchanger was calculated using an analytical model of the heat exchanger.

Taler, Dawid

2013-08-01

96

Experimental and numerical study on effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer coefficient.  

UK PubMed Central (United Kingdom)

This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 x 10(4) to 5.43 x 10(4) (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related.

Rong L; Nielsen PV; Zhang G

2010-04-01

97

An alternative use of the heat transfer coefficient in terms of the gradient thickness  

Energy Technology Data Exchange (ETDEWEB)

In this article, the concept of gradient thickness is further extended to characterize the gradient behavior of the thermal and momentum boundary layer near a solid surface. The gradient thickness can replace the use of the conventional heat transfer coefficient used in the analysis of convective heat transfer. Also, the re-interpretation of the Nusselt and Reynolds numbers in terms of the gradient thickness provides a much easier grasp of the physical and practical meaning of the processes involved. Although there is no urgent need to discard the concept of the conventional convective heat transfer coefficient, the concept of the gradient thickness is believed to serve as an efficient tool in helping students understand underlying physics. (author). 2 refs., 3 figs., 1 tab.

Kim, C.J. [Seoul National University, Seoul (Korea)

2000-12-01

98

Detailed heat transfer coefficient measurements and thermal analysis at engine conditions of a pedestal with fillet radii  

Science.gov (United States)

The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modeled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution, is compared to that calculated using an area-averaged heat transfer coefficient. Metal temperature differences of 90 K are predicted across the blade wall.

Wang, Z.; Ireland, P. T.; Jones, T. V.

1995-04-01

99

Assessment of Mass Transfer Coefficients in Coalescing Slug Flow in Vertical Pipes and Applications to Tubular Airlift Membrane Bioreactors  

DEFF Research Database (Denmark)

One of the operational challenges associated with membrane bioreactors (MBRs) is the fouling of the membranes. In tubular side-stream MBRs, fouling reduction can be achieved through controlling the hydrodynamics of the two-phase slug flow near the membrane surface. The two-phase slug flow induces higher shear stresses near the membrane surface, which generate high mass transfer coefficients from the surface to the bulk region. However, measuring the mass transfer coefficient is difficult in complex heterogeneous mixtures like activated sludge and existing techniques (e.g. electrochemical methods) cannot be applied directly. As an alternative, in this work, a multidisciplinary approach was selected, by exploiting dimensionless analysis using the Sherwood number. Mass transfer coefficients were measured at various superficial velocities of gas and liquid flow in a tubular system. Due to the variability of the mass transfer coefficient obtained for each experimental condition, the results were compiled into, mass transfer coefficient histograms (MTH) for analysis. A bimodal MTH was observed, with one peak corresponding to the mass transfer induced by the liquid flow, and the other peak induced by the gas flow. It was noted that coalescence of bubbles affects the MTH. Coalescence increased the “width” of the peaks (i.e. the estimate of the variability of the mass transfer coefficient) and the height of the peak (i.e. amount of time that a mass transfer coefficient of a given value is maintained). A semi-empirical relationship based on the Lévêque relationship for the Sherwood number (mass transfer coefficient) was formulated for the laminar regime. A test case comparison between water and activated sludge was performed based on full-scale airlift MBR operational conditions. It was found that the Sherwood number in the non-Newtonian case is 8% higher than that in the Newtonian case.

Ratkovich, Nicolas Rios; Berube, P.R.

2011-01-01

100

Development of particulate matter transfer coefficients using a three-dimensional air quality model  

Energy Technology Data Exchange (ETDEWEB)

Air quality model simulations constitute an effective approach to develop source-receptor relationships (so-called transfer coefficients in the risk analysis framework) because a significant fraction of particulate matter (particularly PM{sub 2.5}) is secondary and, therefore, depends on the atmospheric chemistry of the airshed. These source-receptor relationships can be made specific to source regions and major pollutants. In this study, the authors have used a comprehensive three-dimensional air quality model for PM (SAQM-AERO) to generate episodic transfer coefficients for several source regions in the Los Angeles basin (i.e., surface coastal region, elevated coastal region, central basin, and downwind region). Transfer coefficients were developed by conducting PM air quality simulations with reduced emissions of one of the four precursors (i.e., primary PM, SO{sub 2}, NO{sub x}, and VOC) from each source region. The authors have also compared the transfer coefficients generated from explicit modeling with those based on expert judgment, which were obtained by integrating information from the development of the baseline simulation and across-the-board emission reduction simulations.

Seigneur, C.; Tonne, C.; Vijayaraghavan, K.; Pai, P.; Levin, L.

1999-07-01

 
 
 
 
101

Evaluation of heat transfer coefficient at direct contact condensation of cold water and steam  

International Nuclear Information System (INIS)

[en] The research shows the heat transfer coefficient evaluated experimentally by assuming simple interface-shapes for complicated surface or by comparing the results of numerical analyses with the data of experiments related to LOCAs of LWRs. At chugging, the heat transfer coefficient reached up to 2 MW//m2 K). At condensation oscillation, it was between 105-106 W(m2 K). At jet region of cold water injected into steam flow in a pipe or stationary stream in a vessel, it was around 2X105 W/(m2 K), and at the surface of stratified flow, it was between 3x103-3x104 W/(m2 K). (orig./DG)

1989-01-01

102

A Comparative Study of Heat Transfer Coefficients for Film Condensation  

Directory of Open Access Journals (Sweden)

Full Text Available Film condensation heat transfer has wide applications in a variety of industrial systems. A number of film condensation heat transfer correlations (FCHTCs) have been proposed. However, their predictions are often inconsistent. This paper presents a comparative study of existing FCHTCs. Totally 1214 experimental data points are obtained from 10 published papers, and 14 FCHTCs are reviewed, among which four correlations are used for horizontal flow outside smooth tubes, three for flow on vertical surfaces of plates or tubes, two for flow inside smooth tubes either vertically or horizontally, and five for horizontal flow inside smooth tubes. 13 FCHTCs are compared with the experimental data. There are three FCHTCs for horizontal flow inside smooth tubes having a mean absolute relative deviation (MARD) less than 26%, among which the best one has an MARD of 22.2%. More efforts should be made to develop better correlations.Key words: Correlation; Heat transfer; Film; Condensation

Xiaoyong WEI; Xiande FANG; Rongrong SHI

2012-01-01

103

Heat and mass transfer coefficients of falling-film absorption process  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with the method to calculate heat and mass transfer coefficients of falling film absorption process over vertical tube or plate type surface employed in absorption refrigeration system. The conventional log mean temperature/concentration difference method is criticized for lack of physical rationality, and for incorrect results from the calculation. A new method based on a simplified model is proposed and demonstrated by numerical simulations and comparison analysis. (Author)

Fujita, Isamu [Independent Administrative Institution, Nagase (Japan). Port and Airport Research Institute; Hihara, Eiji [University of Tokyo (Japan). Institute of Environmental Studies

2005-06-01

104

Determining convective heat transfer coefficient using phoenics software package  

Energy Technology Data Exchange (ETDEWEB)

The two methods of determination of such important quantity of heat exchange on a body surface using PHOENICS are suggested in the presentation. The first method consists in a post-processing of results of conjugate heat transfer problem solved by PHOENICS. The second one is solving an inverse heat conduction problem for solid body using PHOENICS. Comparative characteristic of these two methods is represented. (author) 4 refs.

Kostikov, A.; Matsevity, Y. [Institute of Mechanical Engineering Problems of National Academy of Sciences of Ukraine, Kharkov (Ukraine)

1997-12-31

105

Heat and mass transfer in non-isothermal absorption of gases in falling liquid films. Pt. 1. Experimental determination of heat and mass transfer coefficients  

Energy Technology Data Exchange (ETDEWEB)

In non-isothermal absorption of steam in falling films of aqueous LiBr solutions local heat and mass transfer coefficients were determined independently of each other by measuring the film surface temperature with an infrared pyrometer. The experimentally determined mass transfer coefficients (Sherwood numbers) confirm well-known correlations, as well as the statements of the Levich-type description of falling film heat and mass transfer, that is, the damping of the turbulence not only near the wall but also in the vicinity of the film surface. So, the assumption that the bulk and the surface temperatures of the film are equal, owing to undamped eddy transport, is not correct. The experimentally determined heat transfer coefficients deviate from the experimental data of Blangetti, the latter determined in film condensation of 1-methoxy-2-propanol-water azetrope (MWA). This discrepancy is due to the thermal entrance effects in the experiments of Blangetti and will be discussed in Part 2.

Yueksel, M.L.; Schluender, E.U.

1987-12-01

106

Transient condensation heat transfer coefficient expressions during and after blowdown  

International Nuclear Information System (INIS)

[en] Analytical expressions are presented for calculating condensation heat transfer coefficients during and after blowdown at specific locations in a containment structure. A forced convention model is used during and immediately after blowdown when much turbulence exists, and a free convection model is used after blowdown end when the turbulence subsides. The forced convection expression depends primarily on a turbulent velocity relationship which is dependent on the distance from the break. The free convection expression depends on the wall-mixture temperature difference and the ratio of air partial pressure to total air-steam pressure. Experimental results were used to refine both of these expressions. Recommendations are given on how they are to be used. Calculations are compared with experimental values. (orig.)

1984-01-01

107

Confirmation of selected milk and meat radionuclide-transfer coefficients  

International Nuclear Information System (INIS)

The elements selected for study of their transfer coefficients to eggs, poultry meat, milk and beef were Mo, Tc, Te, and Ba. The radionuclides used in the study were the gamma-emitting radionuclides 99Mo, /sup 123m/Te and 133Ba. 133Ba was selected because 140Ba-140La is produced infrequently and availability was uncertain. 133Ba has a great advantage for our type of experiment because of its longer physical half-life. 99Tc is a pure beta-emitter and was used in the first three animal experiments because we could not obtain the gamma-emitting /sup 95m/Tc. A supply of this nuclide was recently obtained, however, for the second cow experiment

1983-01-01

108

Mass transfer coefficients of ammonia for liquid dairy manure  

Science.gov (United States)

Available data indicate that 75-80% of total nitrogen entering a dairy operation is lost as ammonia (NH3) via manure storage systems such as anaerobic lagoons. Direct measurement of NH3 emissions from manure holding systems can be complicated and expensive; however, process-based emission models can provide a cost-effective alternative for estimating NH3 emissions. The overall NH3 mass transfer coefficient (KOL) is an important component of any NH3 emission process-based model. Models relying purely on theoretically-derived mass transfer coefficients have not adequately predicted NH3 emissions from livestock manure, and these values are lacking in general for liquid dairy manure handling systems. To provide critically needed KOL data for dairy facilities, this study directly measured NH3 loss from dilute dairy manure slurries placed in a laboratory convective emission chamber to determine realistic NH3KOL values under conditions typically experienced in the Pacific Northwest. The KOL values increased as liquid temperature and air velocity increased and decreased as air temperature and total solids content increased, exhibiting an overall range of 1.41 × 10-6-3.73 × 10-6 m s-1. These values were then used to develop a non-linear empirical model of KOL for dilute dairy manure slurries (R2 = 0.83). The KOL exhibited sensitivity to the four model parameters considered in descending order: liquid manure temperature, ambient air temperature, wind or air velocity, and total solids concentration. The suite of KOL values applicable to liquid dairy manure and the establishment of an empirical model that yields accurate KOL estimates under a range of conditions for use in process-based models provide valuable tools for predicting NH3 emissions from dairy operations.

Vaddella, Venkata K.; Ndegwa, Pius M.; Ullman, Jeffrey L.; Jiang, Anping

2013-02-01

109

The mean coefficients of heat transfer from gas to turbine nozzle blade at high Reynolds numbers  

Science.gov (United States)

The mean heat transfer in the flow section of a high-temperature gas turbine at high Reynolds number between six and seven million was examined. The experimental nozzle cascade is described and experimental velocity curves for assessing the aerodynamic efficiency of the blade profile are shown. The heat-transfer investigation involved calorimetric measurement with forward and reverse directions of the heat flux. The flow rate and temperature difference of water passing through the blade were measured, and the mean coefficients of heat transfer over the profile surface were calculated in the form of the ratio of heat flux density to the difference between the mean temperature of the surface and the inlet cascade flow temperature. The experimental results were used to derive a relation which is analyzed.

Mariev, D. I.; Lelchuk, V. L.; Balashov, Iu. A.

1982-10-01

110

Inverse identification of interfacial heat transfer coefficient between the casting and metal mold using neural network  

Energy Technology Data Exchange (ETDEWEB)

The effect of the heat transfer coefficient at the casting-mold interface is of prime importance to improve the casting quality, especially for castings in metal molds. However, it is difficult to determine the values of heat transfer coefficient from experiments due to the influence of various factors, such as contacting pressure, oxides on surfaces, roughness of surfaces, coating material, coating thickness and gap formation caused by the deformation of casting and mold, etc. In the present paper, the interfacial heat transfer coefficient (IHTC) between the casting and metal mold is identified by using the method of inverse analysis based on measured temperatures, neural network with back-propagation algorithm and numerical simulation. Then, by applying the identified IHTC in finite element analysis, the comparison between numerical calculated and experimental results is made to verify the correctness of method. The results show that the numerical calculated temperatures are in good agreement with experimental ones. These demonstrate that the method of inverse analysis is a feasible and effective tool for determination of the casting-mold IHTC. In addition, it is found that the identified IHTC varies with time during the casting solidification and varies in the range of about 100-3200 Wm{sup -2}K{sup -1}. The characteristics of the time-varying IHTC have also been discussed.

Zhang Liqiang [State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, 410082 Hunan (China); College of Materials Science Engineering, Hunan University, Changsha, 410082 Hunan (China); Li Luoxing, E-mail: llxly2000@163.co [State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, 410082 Hunan (China) and College of Materials Science Engineering, Hunan University, Changsha, 410082 Hunan (China); Ju Hui; Zhu Biwu [College of Materials Science Engineering, Hunan University, Changsha, 410082 Hunan (China)

2010-10-15

111

Evaluation of heat-transfer coefficient at direct-contact condensation of cold water and steam  

International Nuclear Information System (INIS)

[en] The estimation of the heat transfer coefficient at the direct-contact condensation of cold water and steam is a very hard task since the phenoma are essentially undsteady and the interface motion is so complicated that an exact estimation of its araea is almost impossible. The present study shows the heat transfer coefficient evaluated experimentally by assuming simple interface shapes for complicated surfaces and estimated those through comparison of the numerical analyses to the data of experiments related to the loss of coolant accidents of light water reactors. At chugging, the heat transfer coefficient reached up to 2 x 106 W/(m2 K). At condensation oscillation, it ranged between 105-106 W/(m2K). At a jet region of cold water injected into the steam flow in a pipe or the stationary steam in a vessel, the value was around 2 x 105 W/(m2 K), and at the surface of stratified flow, it was between 3 x 103-3x104 W/(m2 K). (orig.)

1991-01-01

112

Modeling the Effect of Internal Convection Currents on Heat Transfer Coefficient of Liquid Foods  

Directory of Open Access Journals (Sweden)

Full Text Available The internal convection currents generated during the cooling process affect convective heat transfer coefficient from the surface of the container, these convection currents may increase the effective value of the surface film conductance (h). Therefore, in such situation the Nu-Re correlations, which are generally used to predict h-values, may not yield realistic results. In the present work, this effect has been investigated by using the empirical correlation developed through Temperature-Time measurements at the centre of liquid food containers during cooling .The main concern of the present work is about considering the heat transfer behaviour for liquid foods for which a cylindrical shape container of brass metal have taken, in this work the transient Time-Temperature relation is utilized to calculate the value of convection heat transfer coefficient (h) for each measured temperature at the centre of the cylinder (r¬¬o=0). Then after plotting the graph between ‘h’ and ‘T’ an expression between h and T is obtained, which is fed back in the programme developed with the help of finite difference method by which Time-Temperature variation is obtained. Experimental procedure was used to determine surface film conductance of cylindrical Apple and Orange juice container, calculated temperatures have been compared with the experimental results when the measured surface film conductance were used to solve the transient heat conduction equation in cylindrical coordinates. A consistently excellent agreement was observed.

SAJID ALI; RASHID ALI

2013-01-01

113

Heat transfer coefficient in pool boiling for an electrically heated tube at various inclinations  

International Nuclear Information System (INIS)

[en] An experimental investigation is carried out study the behaviour of heat transfer in pool boiling from a vertical and inclined heated tube at atmospheric pressure. An imperial correlation joining the different parameters affecting the heat transfer coefficient in pool boiling for an electrically heated tube at various inclinations is developed. Two test sections (zircaloy-4 and stainless steel) of 16 n n outer diameter and 120 nm length are investigated. Four levels of heat flux are used for heating the two lest sections (e.g. 381, 518, 721 and 929 k.watt/n 2). The maximum surface temperature achieved is 146.5 degree c for both materials, and the maximum bulk temperature is 95 degree C. It is found that the average heat transfer coefficient is inversely proportional with heated length l, where it reaches a constant value in the horizontal position. The heat transfer coefficient curves at various inclinations with respect to the heated tube length pass around one point which is defined as limit length

1987-01-01

114

Estimation of the heat transfer coefficient in the spray cooling of continuously cast slabs  

Energy Technology Data Exchange (ETDEWEB)

An inverse problem involving the estimation of the heat transfer coefficient at the surface of a plate, with no information regarding the functional form of the unknown, is solved by applying the conjugate gradient method with adjoint equation. This paper is part of an experimental and numerical simulation of the actual spray cooling process in continuous casting machines. Results obtained with simulated measurements, for the estimation of the time and spatial variation of the unknown spray heat transfer coefficient are summarized. The conjugate gradient method is found to provide accurate estimates for the unknown, even for functions containing sharp corners and discontinuities, which are the most difficult to be recovered by inverse analysis. The effects of number and location of sensors on the inverse problem solution are also addressed on the paper.

Orlande, H.R.B.; Colaco, M.J.

1997-07-01

115

Mesoscopic correlation for heat transfer coefficients with pressure fluctuations in pressurized fluidized bed combustors  

Energy Technology Data Exchange (ETDEWEB)

A dimensionless frequency number, N{sub f}, (fd{sub p}{sup 2}/{alpha}{sub e}) was suggested earlier to understand and predict the bed-to-surface heat transfer coefficient in dense gas-solid fluidized beds at atmospheric conditions. The particle conductive component is accounted for the hyperbolic heat wave equation and by integration between the limits of the thermal time constant of the particle and infinity. The equation was solved for a semi-infinite body problem using a scaling parameter and asymptotic solutions obtained. The solution exhibits a maximum in heat transfer coefficient with respect to time. The gas convective component was found to be dependent on the Peclet number using gas thermal properties. The effects of pressure on the density of the gas was obtained using the Virial equation of state.

Sharma, K.R.

1999-07-01

116

Fouling of heat transfer surfaces  

Energy Technology Data Exchange (ETDEWEB)

The history of the fouling of heat transfer surfaces is reviewed up to 1979. Four epochs of fouling are identified. Particular attention is paid to fouling in steam boilers and steam condensers. The origin of the cleanliness factor and the fouling factor are discussed. The introduction of scientific methods of studying fouling through the model of Kern and Seaton, and the application of models based on fundamental ideas in mass transfer are considered. The paper concludes by drawing attention to the successes in understanding fouling and pointing out the needs for future research.

Somerscales, E.F.C. (Rensselaer Polytechnic Inst., Troy, NY (USA))

1990-01-01

117

External heat and mass transfer coefficients for kiln drying of timber  

Energy Technology Data Exchange (ETDEWEB)

Correlations are derived relating the heat-transfer coefficient to the mass-transfer coefficient in kiln drying of timber boards by using the Chilton-Colburn analogy. Existing experimental data for the mass-transfer coefficient of naphthalene vapor in the airstream at low temperature are converted to coefficients under commercial timber drying conditions. The calculated results from this analysis are compared with the values employed by wood drying modelers in their models and it appears that the external transfer coefficients used by the drying modelers are generally below the values calculated from the laboratory data.

Pang, S. [New Zealand Forest Research Inst., Rotorua (New Zealand). Wood Processing Div.

1996-05-01

118

A numerical method for determining heat transfer coefficients in crossflow compact heat exchangers  

International Nuclear Information System (INIS)

An essential, and often the most uncertain, part of any two-fluid heat exchanger analysis is the determination of heat transfer coefficients on both fluid sides. Heat transfer coefficients for exchanger surfaces are usually obtained experimentally using the (modified) Wilson plot technique for the test data analysis. Fluid side heat transfer coefficients are determined from an overall heat transfer coefficient, which is known from energy the balance of a heat exchanger. The original and modified Wilson plot techniques are based on the linear regression and their applications are limited to the power-law relationships between Nusselt (Nu) and Reynolds (Re) and Prandtl (Pr) numbers. In this paper a numerical method for obtaining correlations for both fluid sides is presented. The primary measurements consist of the flow rates of each fluid streams (35 % aqueous ethylene glycol solution and air), their inlet and outlet temperatures and pressure drops in both streams between the inlet and outlet of the heat exchanger. The problem of determining non-dimensional average heat transfer coefficients is formulated as a parameter estimation problem by selecting the functional form for the Nusselt number Nu=f(Re, Pr). There are n parameters x=(x1,...,xn)T to be determined such that computed outlet tube side fluid temperatures Ti agree in the least-squares sense with the experimentally acquired temperatures fi. The non-linear least-squares problem was solved using the Levenberg-Marquardt method. The uncertainties in the estimated parameters are determined for temperature measurements with unknown standard deviations. In order to calculate the outlet fluid temperature Ti as the function of searched parameters a mathematical model of the heat exchanger using the control-volume method was developed. The results of the experimental investigation of the plate-fin-tube automotive radiator are presented. The tested two-pass radiator consists of two inline rows of oval tubes with smooth plate fins. The air and coolant mass flows, the total pressure drops through the radiator and inlet and outlet temperatures were measured in eighteen measurement points. The new correlations for the heat transfer coefficients on the air and coolant sides were developed using presented technique. The 95 % confidence intervals for the determined parameters are also given. The main advantage of the presented method is that it does not require any knowledge, or solution of the complex fluid flow field. It can be used for determining heat transfer characteristics of different type heat exchangers. Refs. 3 (author)

2002-01-01

119

Detailed heat transfer coefficient measurements and thermal analysis at engine conditions of a pedestal with fillet radii  

Energy Technology Data Exchange (ETDEWEB)

Short pin-fin and pin-fin arrays are frequently used in turbine blade internal cooling systems to enhance cooling and stiffen the structure. The present work has shown that a knowledge of the detailed heat transfer coefficient distribution is required to predict the cooling effect of such devices accurately. The heat flow process has been numerically modeled at typical engine conditions with the detailed heat transfer distribution measured by the transient heat transfer method being used as the thermal boundary conditions. The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modeled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution, is compared to that calculated using an area-averaged heat transfer coefficient. Metal temperature differences of 90 K are predicted across the blade wall.

Wang, Z.; Ireland, P.T.; Jones, T.V. [Univ. of Oxford (United Kingdom). Dept. of Engineering Science

1995-04-01

120

Convective heat transfer coefficient identification behind a backward-facing step by active infrared thermography  

Energy Technology Data Exchange (ETDEWEB)

A methodology for measuring mean and unsteady local heat transfer coefficient, based on the thin film method, is presented. It consists in following the evolution of the surface temperature of a sensible surface submitted to a perturbed flow. The temperature field along the time is acquired by an infrared thermography system synchronized with velocity and fluctuating pressure measurements. A thermal modeling of this wall allows us to characterize and identify the local value of the mean and unsteady heat transfer coefficient. This measurement method has been validated by studying the impact of a pulsed turbulent air jet on a flat plate. It is now applied to the study of the heat transfer in the aerodynamic reattachment zone present in the flow downstream a backward-facing step. A first correlation, for the mean heat transfer, is proposed for the backward-facing step setup of the DERMES (Departement d`Etudes et de Recherches en Mecanique et Energetique des Systemes). The unsteady results are analysed in time evolution in a thermal point of view and compared to the tomographic visualizations of this flow. Finally, the contribution of synchronized measurements and infrared thermography are discussed as for their efficiencies and future developments. (authors). 14 refs., 16 figs., 1 tab.

Dumoulin, J. [Institut National des Sciences Appliquees (INSA), 31 - Toulouse (France); Reulet, P.; Plazanet, M.; Millan, P. [Office National d`Etudes et de Recherches Aerospatiales (ONERA), 31 - Toulouse (France). Centre d`Etudes et de Recherches

1995-07-01

 
 
 
 
121

Boiling Heat Transfer on Superhydrophilic, Superhydrophobic, and Superbiphilic Surfaces  

CERN Document Server

With recent advances in micro- and nanofabrication, superhydrophilic and superhydrophobic surfaces have been developed. The statics and dynamics of fluids on these surfaces have been well characterized. However, few investigations have been made into the potential of these surfaces to control and enhance other transport phenomena. In this article, we characterize pool boiling on surfaces with wettabilities varied from superhydrophobic to superhydrophilic, and provide nucleation measurements. The most interesting result of our measurements is that the largest heat transfer coefficients are reached not on surfaces with spatially uniform wettability, but on biphilic surfaces, which juxtapose hydrophilic and hydrophobic regions. We develop an analytical model that describes how biphilic surfaces effectively manage the vapor and liquid transport, delaying critical heat flux and maximizing the heat transfer coefficient. Finally, we manufacture and test the first superbiphilic surfaces (juxtaposing superhydrophobic ...

Betz, Amy Rachel; Kim, Chang-Jin 'CJ'; Attinger, Daniel

2012-01-01

122

Mass transfer coefficient for volatilization of volatile organic compounds from wastewater  

Directory of Open Access Journals (Sweden)

Full Text Available Volatilization of volatile organics compounds (VOCs) from wastewater is recognized as an important source that caused air pollution today. In air pollution management regarding VOCs emission to atmosphere, the amount of VOCs that released from wastewater needs to be known. A model for predicting of VOCs volatilized from wastewater is then necessary. The aim of this research was to develop the gas-film (kGa,VOC) and liquid-film (kLa,VOC) mass transfer coefficients from volatilization of VOCs from wastewater. The volatilization experiments were performed in a pilot volatilization tank with a volume of 100 L. The wind speed over the water surface, measured at 10 cm above water surface (U10cm), was the main parameter which investigated in this work. The U10cm were varied from 0 to 4.42 m/s. VOCs used in this investigation were methanol, toluene and methyl ethyl ketone.The results revealed that the gas-film coefficient of methanol increased linearly with increasing U10cm over the investigated range of U10cm whereas the liquid-film coefficient of toluene fell into two regimes with a break at the U10cm of 2.4 m/s. The correlations of kGa,VOC and kLa,VOC were developed from gas-film and liquid-film coefficient of methanol and toluene, respectively, and verified by predicting overall mass transfer coefficient (KOLa) of MEK. It was found that the correlations of kGa,VOC and kLa,VOC predicted the mass transfer coefficient of MEK which volatilized from wastewater quite well but underestimated KOLa of MEK volatilized from pure water. Since the mass transfer coefficient of VOCs volatilized from pure water were significant higher than that of wastewater as found in this work, the kGa,VOC and kLa,VOC developed based on wastewater is recommended for prediction of VOCs emission rate from wastewater rather than the correlation previously developed based on pure water.

Bunyakan, C.; Saeoung, S.; Intamanee, J.; Chungsiriporn, J.

2006-01-01

123

The transfer of radiocaesium to ewes through a breeding cycle - an illustration of the pitfalls of the transfer coefficient  

Energy Technology Data Exchange (ETDEWEB)

A study to measure the transfer of radiocaesium to adult female sheep through a breeding cycle is described. The transfer of radiocaesium from the diet to muscle (estimated as the equilibrium transfer coefficient) was significantly lower to pregnant, and especially lactating, animals compared to non-lactating and barren animals. High dry matter intake rates were also associated with significantly lower transfer coefficients. Known relationships between dry matter intake rates and protein turnover could credibly explain some of these differences. However, when described as the concentration ratio, radiocaesium transfer to meat was apparently highest during lactation. The apparent difference in results obtained by the two approaches of determining transfer is the consequence of daily dry matter intake being a denominator within the estimation of transfer coefficient. A wider discussion of transfer coefficients and concentration ratios leads us to suggest that the concentration ratio is the more robust and potentially generic parameter.

Beresford, N.A. [Centre for Ecology and Hydrology, CEH-Lancaster, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP (United Kingdom)], E-mail: nab@ceh.ac.uk; Mayes, R.W. [Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen AB15 8QH (United Kingdom); Barnett, C.L.; Howard, B.J. [Centre for Ecology and Hydrology, CEH-Lancaster, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP (United Kingdom)

2007-11-15

124

Mass transfer coefficients in a hanson mixer-settler extraction column  

Directory of Open Access Journals (Sweden)

Full Text Available The volumetric overall mass transfer coefficients in a pilot plant Hanson mixer-settler extraction column of seven stages have been measured using toluene-acetone-water system. The effects of agitation speed and dispersed and continuous phases flow rates on volumetric overall mass transfer coefficients have been investigated. The results show that the volumetric overall mass transfer coefficient increases with increase in agitation speed and reaches a maximum. After having reached its maximum, it falls with further increase in agitation speed. It was found that the volumetric overall mass transfer coefficient increases with increase in dispersed phase flow rate, while it decreases with increase in continuous phase flow rate. By using interfacial area, the overall mass transfer coefficients for continuous and dispersed phases are determined from volumetric coefficients. An empirical correlation for prediction of the continuous phase overall mass transfer coefficient is proposed in terms of Sherwood and Reynolds numbers. Also the experimental data of the column investigated are compared with data for various extraction columns. Comparison between theoretical models and experimental results for the dispersed phase mass transfer coefficient shows that these models do not have enough accuracy for column design. Using effective diffusivity in the Gröber equation results in more accurate prediction of overall mass transfer coefficient. The prediction of overall mass transfer coefficients from the presented equations is in good agreement with experimental results.

M. Torab-Mostaedi; S. J. Safdari; M. A. Moosavian; M. Ghannadi Maragheh

2008-01-01

125

Investigation of the concentration dependence of mass transfer coefficients in reversed-phase liquid chromatography.  

UK PubMed Central (United Kingdom)

In order to investigate the concentration dependence of mass transfer coefficients in RPLC, experimental breakthrough curves obtained by staircase frontal analysis (FA) were fitted to the simplified models such as multiplate (MP) model, equilibrium dispersive (ED) model, and transport model, and the sophisticated models such as lumped pore diffusion (POR) model and general rate (GR) model. The MP model was used to obtain the initial guesses of the parameters of the ED and the transport models. Then the best values were obtained by minimizing the differences between theoretical and experimental values with a nonlinear fitting procedure. The values of the parameters of the POR and the GR models can be calculated by using the expressions derived from the plate height equations, which was further validated by using the fitting method. It was found that the mass transfer coefficients would depend on the solute concentration. This can be ascribed to the surface diffusivity, which correlates with the concentration and is lumped into the mass transfer coefficients for both simplified and sophisticated models.

Hao W; Wang J; Zhang X

2006-12-01

126

Transfer coefficients in soil-plant system in locality of Kecerovce nuclear power plant  

International Nuclear Information System (INIS)

Transfer coefficients were determined in the Kecerovce area in the soil-plant system in cereals, perennial feeds, vegetables and root crops for Sr, Zn, Mn, and 137Cs. The lowest transfer coefficients were found for generative organs in perennial plants. With regard to the value of transfer coefficients the said plants ranked as follows: perennial feeds, root crops, cereals. (author). 2 tabs., 6 refs

1989-01-01

127

Confirmation of selected milk and meat radionuclide transfer coefficients. Progress report  

Energy Technology Data Exchange (ETDEWEB)

The objectives are to determine transfer coefficients to milk, beef and chicken of four radionuclides for which transfer coefficients were either indetermined or based upon secondary data. The radionuclides are /sup 99/Mo, /sup 99/Tc, /sup 140/Ba, and /sup 131/Te. The transfer coefficient for /sup 133/I to eggs was also determined, because again only limited data was available in the literature.

Ward, G.M.; Johnson, J.E.

1984-08-28

128

Analytical determination of the heat transfer coefficient for turbulent flow past a partially heated flat plate  

Energy Technology Data Exchange (ETDEWEB)

This paper presents an analytical solution to determine the average convection heat-transfer coefficient for turbulent flow over partially heated flat plate. In this approach a particular expression is used which uniquely simplifies the expression for local heat-transfer coefficient for the plate. This results in obtaining a general equation for average heat-transfer coefficient for a heated plate length in terms of the total length of the plate.

Scott, R.R.; Najafi, M. [Univ. of Southwestern Louisiana, Lafayette, LA (United States). Dept. of Mechanical Engineering

1996-12-31

129

Enhancement of Volumetric Mass Transfer Coefficient for Oxygen Transfer Using Fe2O3-Water Nanofluids  

Directory of Open Access Journals (Sweden)

Full Text Available Experiments were carried out with Fe2O3-water nanofluids to study possible enhancement in volumetric mass transfer coefficient for transfer of oxygen from air bubble to nanofluid, in an agitated, aerated bioreactor. The nanoparticles concentration was varied in the range of 0.022 to 0.065 wt.%, while the reactor was operated at three operating conditions viz. 200 rpm and 1.5 L min-1 of air flow, 100 rpm and 1.5 L min-1 of air flow and 200 rpm and 0.75 L min-1 of air flow. Nanoparticles were found to contribute to enhance oxygen transfer through ‘grazing effect’. An enhancement of 63% was observed for 0.065 wt.% Fe2O3-water operated at 200 rpm and 0.75 L min-1 air flow.

S. Manikandan; N. Karthikeyan; K.S. Suganthi; K.S. Rajan

2012-01-01

130

Experimental determination of momentum transfer coefficients in hypersonic free molecular flow and distribution function recovery of reflected molecules  

International Nuclear Information System (INIS)

[en] This paper investigates the nitrogen molecule interaction with surfaces at 2eV for a developed adsorbed layer. A molecular beam is obtained by exhausting nitrogen of 6000 K into vacuum. The momentum transfer coefficients are obtained by means of measuring the forces on plates of different materials in a flow. The mass flux indicatrices are measured, the surface roughness being measured electrochemically. The momentum transfere coefficients are shown to be stable with time, within the measured error. The simultaneous handling of the force and indicatrix data show their consitency. A model funciton of reflected molecules distribution is proposed on the basis of these measurements. The surface roughness increase results in a fall of the momentum transferred to the surface by reflected molecules. A number of approximate formulae is given

1985-01-01

131

Transfer coefficients for water-air exchange of ammonia, carbon dioxide and methane  

Energy Technology Data Exchange (ETDEWEB)

The ability of a stagnant film model of gas transfer to an across and air-water interface to predict emissions of ammonia, carbon dioxide and methane from a large, shallow, freshwater pond was examined. The model gives quite different transfer coefficients for the three gases in their air and water phases. Supersaturation of the water with respect to the overlying air occurred for all three gases. Micrometeorological measurements using aerodynamic approaches were used to calculate the atmospheric flux densities of water vapor and the gases. The water vapour density at the surface was inferred from the surface temperature. Wet-trapping was used to measure atmospheric gradients of NH{sub 3} concentration, and knowledge of the water chemistry to calculate aqueous NH concentrations. The CH{sub 4} and CO{sub 2} concentrations in air and water were measured by infrared gas analysis. Transfer coefficients were calculated from the fluxes and the water-air concentration differences, and compared with those predicted by Deacon`s model. For water vapour in the air, Deacon`s model overestimates atmospheric transfer coefficients by c. 25% in low winds. for NH{sub 3}, c. 2/3 of the resistance to transport is in the air, c. 1/3 in the water. The model overestimates the fluxes in low winds. For CO{sub 2}, almost all resistance to transport resides in the water. Deacon`s model would provide a very good description of CO{sub 2} exchange. For CH{sub 4}, most of the transport appears to be by ebullition. Some escaping bubbles were 1/3 methane. (AB) 30 refs.

Denmead, O.T. [Centre for Environ. Mechanics, CSIRO, Canberra (Australia)

1992-12-31

132

Heat transfer from rough surfaces  

International Nuclear Information System (INIS)

[en] Artificial roughness is often used in nuclear reactors to improve the thermal performance of the fuel elements. Although these are made up of clusters of rods, the experiments to measure the heat transfer and friction coefficients of roughness are performed with single rods contained in smooth tubes. This work illustrated a new transformation method to obtain data applicable to reactor fuel elements from these annulus experiments. New experimental friction data are presented for ten rods, each with a different artificial roughness made up of two-dimensional rectangular ribs. For each rod four tests have been performed, each in a different outer smooth tube. For two of these rods, each for two different outer tubes, heat transfer data are also given. The friction and heat transfer data, transformed with the present method, are correlated by simple equations. In the paper, these equations are applied to a case typical for a Gas Cooled Fast Reactor fuel element. (orig.)[de] Durch kuenstliche Rauhigkeit kann in Kernreaktoren die Waermeuebertragungsfaehigkeit der Brennelemente verbesserte werden. Obwohl die Brennelemente aus Stabbuendeln bestehen, werden die Experimente zur Messung der Waermeuebertragungs- und Reibungskoeffizienten der Rauhigkeiten an Einzelstaeben in glatten Rohren durchgefuehrt. Diese Arbeit beschreibt eine neue Transformationsmethode, mit der Daten fuer Reaktorbrennelemente aus diesen Versuchen im Ringspalt erzielt werden koennen. Reibungsbeiwerte wurden an zehn verschiedenen rauhen Staeben mit rechteckigen Rippen in jeweils vier verschiedenen glatten Aussenrohren und Waermeuebergangskoeffizienten an zwei dieser rauhen Staebe in jeweils zwei der glatten Aussenrohre gemessen. Die mit Hilfe der vorgestellten Methode transformierten Reibungs- und Waermeuebertragungswerte werden durch einfache Gleichungen beschrieben. Diese Gleichungen werden auf einen Fall angewandt, der fuer ein Brennelement eines gasgekuehlten schnellen Reaktors typisch ist. (orig.)

1977-01-01

133

Estimation of grass to cow's milk transfer coefficients for emergency situations  

International Nuclear Information System (INIS)

Several studies have been reported on soil to grass equilibrium transfer factors and grass to cow's milk transfer coefficients for 137Cs for the environs of different nuclear power plants of both India and other parts of the world. In such studies, the activity concentration of 137Cs is measured in grass collected from different places. Cow's milk samples are collected from nearby localities or from milk dairies and analyzed for 137Cs and the grass to cow's milk transfer coefficient is estimated. In situation where 137Cs is not present in measurable activity concentrations, its stable counterpart (Cs) is measured for the estimation of transfer coefficients. These transfer coefficient values are generally used in theoretical models to estimate the dose to the population for hypothetical situation of emergency. It should be noted that the transfer coefficients obtained for equilibrium conditions may not be totally applicable for emergency situation. However, studies aimed at evaluating transfer coefficients for emergency situations are sparse because nuclear power plants do not release 137Cs during normal operating situations and therefore simulating situation of emergency release is not possible. Hence, the only method to estimate the grass to milk transfer coefficient for emergency situation is to spike the grass with small quantity of stable Cs. This paper reports the results of grass to milk transfer coefficients for stable isotope of Cesium (Cs) for emergency situation

2012-01-01

134

Townsend coefficients for electron scattering over dielectric surfaces  

Science.gov (United States)

A method for describing the probability of initiating flashover discharges across dielectric surfaces is presented in which a transport coefficient for electron multiplication similar to the Townsend coefficient used for gas discharges is defined. The coefficient is a function of the scaling parameter (charge released from the cathode)/(cathode-anode separation) and is also a measure of the growth of the sheath on the dielectric surface resulting from electron scattering. Results are discussed as to when the source of seed electrons does not necessarily depend upon field emission at the cathode-vacuum-dielectric triple point. For these conditions, there is a different functional dependence of flashover probability on voltage and geometry than when field emission provides the seed electrons. As a result, criteria previously used to predict flashover discharges may not apply.

Peck, Timothy L.; Kushner, Mark J.

1988-11-01

135

Coefficients of solid surface sputtering by light ions  

International Nuclear Information System (INIS)

[en] The formula for calculation of coefficients of solid surface sputtering by light ions in the 10-105 eV energy range, is derived. The formula takes into account the masses and charges of the target atom nucleus and ion, sublimation energy of target surface and parameters of the Born-Mayer interaction between atoms of sputtered target. The formula is based on the model of cascade atom emission

1990-01-01

136

Investigation of Natural Convection Heat Transfer Coefficient on Extended Vertical Base Plates  

Directory of Open Access Journals (Sweden)

Full Text Available In this research, Computational analysis of the laminar natural convection on vertical surfaces has been in-vestigated. Natural convection is observed when density gradients are present in a fluid acted upon by a gravitational field. Our example of this phenomenon is the heated vertical plate exposed to air, which, far from the plate, is motionless. The CFD simulations are carried out using fluent software. Governing equa-tions are solved using a finite volume approach. Coupling between the velocity and pressure is made with SIMPLE algorithm. The resultant system of discretized linear algebraic equations is solved with an alternat-ing direction implicit scheme. Then a configuration of rectangular fins is put in different ways on the surface and natural convection heat transfer coefficient on these no slope surfaces is studied and finally optimization is done.

M. Fahiminia; M. M. Naserian; H. R. Goshayeshi; D. Majidian

2011-01-01

137

Modeling flavor release from aqueous sucrose solutions, using mass transfer and partition coefficients  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The penetration theory of interfacial mass transfer was used to model flavor release from aqueous solutions containing different concentrations of sucrose. The mass transfer coefficient and the gas/solution partition coefficient are the main factors of the model influencing the release in time. Para...

Nahon, D.F.; Harrison, M.; Roozen, J.P.

138

The determination of individual mass transfer coefficients in liquid-liquid extraction  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An improved Lewis cell has been used as an efficient method to determine the mass transfer coefficient for any ternary multi-component system. In this paper the individual mass transfer coefficients were determined for three ternary systems: water-acetone-carbon tetrachloride water-acetone-chlorofor...

Radu Tudose Z.; Lisa Gabriela

139

Condensation heat transfer coefficient with noncondensible gases for heat transfer in thermal hydraulic codes  

Energy Technology Data Exchange (ETDEWEB)

Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology`s (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values.

Banerjee, S.; Hassan, Y.A. [Texas A& M Univ., College Station, TX (United States)

1995-09-01

140

Condensation heat transfer coefficient with noncondensible gases for heat transfer in thermal hydraulic codes  

International Nuclear Information System (INIS)

[en] Condensation in the presence of noncondensible gases plays an important role in the nuclear industry. The RELAP5/MOD3 thermal hydraulic code was used to study the ability of the code to predict this phenomenon. Two separate effects experiments were simulated using this code. These were the Massachusetts Institute of Technology's (MIT) Pressurizer Experiment, the MIT Single Tube Experiment. A new iterative approach to calculate the interface temperature and the degraded heat transfer coefficient was developed and implemented in the RELAP5/MOD3 thermal hydraulic code. This model employs the heat transfer simultaneously. This model was found to perform much better than the reduction factor approach. The calculations using the new model were found to be in much better agreement with the experimental values

1995-01-01

 
 
 
 
141

Calculating the heat transfer coefficient of frame profiles with internal cavities  

DEFF Research Database (Denmark)

Determining the energy performance of windows requires detailed knowledge of the thermal properties of their different elements. A series of standards and guidelines exist in this area. The thermal properties of the frame can be determined either by detailed two-dimensional numerical methods or by measurements in accordance to European or international standards. Comparing measured and calculated heat transfer coefficients for two typical frame profiles with cavities shows considerable differences. This investigation considers two typical frame profiles in aluminium and PVC with internal cavities. The heat transfer coefficient is determined by two-dimensional numerical calculations and by measurements. Calculations are performed in Therm (LBNL (2001)), which is developed at Lawrence Berkeley National Laboratory, USA. The calculations are performed in accordance with the future European standards and measurements have been performed at two German research institutes. The internal cavities have a large influence on the overall thermal performance of the frame profiles and the investigation shows that the applied method for modelling the heat transfer by radiation exchange in the internal cavities of the profiles is critical. The simple radiation model described in the pre European standard (prEN ISO 10077-2) does not yield valid results compared to measured values. Applying a more detailed, viewfactor based, grey surfaces enclosure model as described in the ISO standard (ISO/DIS 15099) gives a better correspondence between measured and calculated values. Hence, when determining the heat transfer coefficient of frame profiles with internal cavities by calculations, it is necessary to apply a more detailed radiation exchange model than described in the prEN ISO 10077-2 standard. The ISO-standard offers such an alternative.

Noyé, Peter Anders; Laustsen, Jacob Birck

2004-01-01

142

Modeling flavor release from aqueous sucrose solutions, using mass transfer and partition coefficients.  

UK PubMed Central (United Kingdom)

The penetration theory of interfacial mass transfer was used to model flavor release from aqueous solutions containing different concentrations of sucrose. The mass transfer coefficient and the gas/solution partition coefficient are the main factors of the model influencing the release in time. Parameters governing the isolation by a purge and trap method at mouth conditions (volume, temperature, and artificial saliva) were used in the model description of the flavor release. Viscosities of the different sucrose solutions (0-60 w/v %) at 37 degrees C were estimated, and their influence on the mass transfer coefficients was determined. The gas/solution partition coefficients for ethyl acetate, methyl butanoate, ethyl butanoate, hexanal, and octanal were measured for the different sucrose concentrations at 37 degrees C. At lower sucrose concentrations the partition coefficient primarily controls flavor release during a purge time of 10 min, whereas at higher sucrose concentrations the influence of the mass transfer coefficient is more important.

Nahon DF; Harrison M; Roozen JP

2000-04-01

143

Importance of the speciation of radionuclides for the calculation of transfer coefficients: Application to soil-fungus transfer  

International Nuclear Information System (INIS)

Full text: Transfer coefficients are commonly used as an approximation to the problem of quantifying the transit of radionuclides between an ecosystem's different characteristic receptor media. These coefficients are traditionally defined as the quotient between the specific activities of the receptor and the donor compartments. In the present study, the receptors were edible mushrooms and the donor, the soil. However, not all the radioactive contents of a soil are in a condition to be transferred. Instead, the fraction that is available will depend intimately on the capacity of the different compounds to which the radionuclides are associated to be taken up by the fungus. To analyse the cited capacity, we carried out a scheme of chemical speciation of the surface layer (0-5 cm) of the soils corresponding to two forest ecosystems (pine woods) that present a high productivity of mushrooms. This scheme consists of the sequential extraction of the available soil fraction (extractable with NH4OAc), that soluble in dilute acid (extractable with HCl 1M), that soluble in strong acid (extractable with HCl 6M), and the residue. We analysed the presence of different man-made (137Cs, 90Sr) and natural (40K, 226Ra) radionuclides in each of the soil fractions enumerated above and in two representative species of mushroom from the aforementioned two ecosystems: Hebeloma cylindrosporum and Lactarius deliciosus. Specifically, more than 75% of the concentrations of 40K and 137Cs present in the soils studied were found bound to fractions not accessible to exchange reactions (the fraction soluble in strong acid and the residue). This implies that they are not associated to chemical compounds capable of being transferred to the fungi's fruiting bodies. Therefore, it is totally inappropriate to calculate the transfer coefficients in the usual way, since this uses the total activity found in the soil layer being considered. By way of example, for 40K the traditional method underestimates the transfer by approximately two orders of magnitude. We hence propose another approach, considering only the fraction of radionuclides present in the soil that are really in condition to be transferred. (author)

2003-01-01

144

MEASUREMENT OF QUENCHING INTENSITY, CALCULATION OF HEAT TRANSFER COEFFICIENT AND GLOBAL DATABASE OF LIQUID QUENCHANTS  

Directory of Open Access Journals (Sweden)

Full Text Available This paper explains the need for a database of cooling intensities for liquid quenchants, in order to predict the quench hardness, microstructure, stresses and distortion, when real engineering components of complex geometry are quenched. The existing laboratory procedures for cooling intensity evaluation, using small test specimens, and Lumped-Heat-Capacity Method for calculation of heat transfer coefficient, are presented. Temperature Gradient Method for heat transfer calculation in workshop conditions, when using the Liscic/Petrofer probe, has been elaborated. Critical heat flux densities and their relation to the initial heat flux density, is explained. Specific facilities for testing quenching intensity in workshop conditions, are shown.The two phase project of the International Federation for Heat Treatment and Surface Engineering (IFHTSE), as recently approved, is mentioned.

Božidar Liš?i?; Tomislav Filetin

2012-01-01

145

Evaluation of generalized heat-transfer coefficients in pilot AFBC units  

Energy Technology Data Exchange (ETDEWEB)

Experimental data for heat transfer rates as obtained in a 0.209m/sup 2/ AFBC unit at the GFETC is examined in the light of the existing four correlations for heat transfer coefficient between an immersed staggered array of horizontal tubes and a gas-solid fluidized bed. The predicted values of heat transfer coefficient from the correlations proposed by Grewal and Bansal are found to be in good agreement with the experimental values of heat transfer coefficient when the contribution due to radiation is also included.

Grewal, N.S.

1981-07-01

146

The determination of individual mass transfer coefficients in liquid-liquid extraction  

Directory of Open Access Journals (Sweden)

Full Text Available An improved Lewis cell has been used as an efficient method to determine the mass transfer coefficient for any ternary multi-component system. In this paper the individual mass transfer coefficients were determined for three ternary systems: water-acetone-carbon tetrachloride water-acetone-chloroform and water-acetone-toluene, using the improved Lewis cell. Criteria! equations were developed to calculate the mass transfer coefficients when one or both (organic and aqueous) phases were agitated and when solute transfer occurs in both directions.

Radu Tudose Z.; Lisa Gabriela

2003-01-01

147

EXPERIMENTAL INVESTIGATION OF HEAT TRANSFER ENHANCEMENT OVER THE DIMPLED SURFACE  

Directory of Open Access Journals (Sweden)

Full Text Available Over the past couple of years the focus on using concavities or dimples provides enhanced heat transfer has been documented by a number of researchers. Dimples are used on the surface of internal flow passages because they produce substantial heat transfer augmentation. This project work is concerned with experimentalinvestigation of the forced convection heat transfer over the dimpled surface. The objective of the experiment is to find out the heat transfer and air flow distribution on dimpled surfaces and all the results obtained are compared with those from a flat surface. The varying parameters were i) Dimple arrangement on the plate i.e.staggered and inline arrangement and ii) Heat input iii)Dimple density on the plate. Heat transfer coefficients and Nusselt number were measured in a channel with one side dimpled surface. Thespherical type dimples were fabricated, and the diameter and the depth of dimple were 6 mm and 3 mm, respectively. Channel height is 25.4mm, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 5000 to 15000.Study shown that thermal performance is increasing with Reynolds number. With the inline and staggered dimple arrangement, the heat transfer coefficients, Nusselt number and the thermal performance factors were higher for the staggered arrangement.

Iftikarahamad H. Patel; Dr. Sachin L. Borse

2012-01-01

148

Fouling of heat transfer surfaces  

International Nuclear Information System (INIS)

There are many parameters affecting the fouling deposit on the heat transfer surface. These parameters include flow velocity, surface temperature, fluid bulk temperature, fluid characteristics, surface material and structure. The flow velocity is one of the most important parameters affecting the fouling rate and there is a rarity in literature covering this effect. Therefore, the purpose of the present work is to study the effect of flow velocity on the fouling rate. To carry out this study, an experimental test rig has been designed and constructed. The experimental loop has three 97% Cu-Ni test tubes of 2400 mm length and 16 mm inner diameter. Water with a solid particle concentration of 19 m/lit is used as a test fluid. The test fluid flows through the tubes which are heated by means of steam. The cooling water is arranged in a closed loop to keep constant solid particle concentration. The experiments are carried out under constant surface temperature by using the steam as a heating medium. These experiments have been carried out under different flow velocities (from 0.2 to 1.42 m/s). The experimental loop is a differential one and the runs have been operated for long time (about 200 hrs.) to attain the asymptotic fouling resistance. The obtained experimental results are analyzed, and the effect of flow velocity on the fouling rate and the asymptotic fouling resistance is plotted. From the discussion of these results, it is concluded that; both the fouling resistance and the asymptotic fouling resistance decrease with increasing the flow velocity. The delay time is very small and is seen to approach zero in all the experimental work. The saw tooth effect has been obtained in all runs. Results have shown also essential.10 tabs.,4-8 figs.,71 refs.

1996-01-01

149

Unsteady radiative-convective heat transfer on a radiating surface  

International Nuclear Information System (INIS)

[en] Research of radiation-convective heat exchange on radiating surfaces at natural and forced convection is complex mathematical task and here we obtain approximate analytical formulations for this process. We consider two dimensional unsteady heat transfer between solid surface and fluid under the natural laminar convection within optically transparent grey media. Also we assume constant thermo-physical properties except density which is decreasing linearly with temperature. Complex radiative-convective unsteady heat transfer approximately can be considered as a multi-stage process. At the beginning heat transfer coefficient is time dependent but almost independent on longitudinal coordinate. Afterwards heat transfer coefficient becomes dependent on longitudinal coordinate but does not change over time. Analytic formulations obtained for those two stages could be merged along the 'time-space' characteristic basing on the equality of heat flows and temperatures there. Solutions are constructed using asymptotic expansions. Theoretical analysis of the solutions revealed the following: effect of radiation leads to a change in the heat transfer coefficient from the values that are characteristic to the second order boundary conditions to the values that are characteristic for the first order boundary conditions. The rate of this transition depends on ß radiation coefficient. Experimental research confirmed correctness of the simplifications introduced.

2012-11-26

150

Heat transfer coefficient correlation for convective boiling inside plain and micro fin tubes using genetic algorithms  

Energy Technology Data Exchange (ETDEWEB)

Two-phase flow heat transfer has been exhaustively studied over recent years. However, in this field several questions remain unanswered. Heat transfer coefficient prediction related to nucleate and convective boiling have been studied using different approaches, numerical, analytical and experimental. In this work, an experimental analysis, data representation and heat transfer coefficient prediction on two-phase heat transfer on nucleate and convective boiling are presented. An empirical correlation is obtained based on genetic algorithms search engine over a dimensional analysis of the two-phase flow heat transfer problem. (author)

Picanco, Marco Antonio Silva [Regional University of Jaragua do Sul (UNERJ), SC (Brazil)], e-mail: mpicanco@unerj.br; Bandarra Filho, Enio Pedone [Federal University of Uberlandia (UFU), MG (Brazil). Fac. de Engenharia Mecanica], e-mail: bandarra@mecanica.ufu.br; Passos, Julio Cesar [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Dept. de Engenharia Mecanica. Lab. de Engenharia de Processos e Tecnologia de Energia], e-mail: jpassos@emc.ufsc.br

2006-07-01

151

Heat transfer coefficient correlation for convective boiling inside plain and micro fin tubes using genetic algorithms  

International Nuclear Information System (INIS)

Two-phase flow heat transfer has been exhaustively studied over recent years. However, in this field several questions remain unanswered. Heat transfer coefficient prediction related to nucleate and convective boiling have been studied using different approaches, numerical, analytical and experimental. In this work, an experimental analysis, data representation and heat transfer coefficient prediction on two-phase heat transfer on nucleate and convective boiling are presented. An empirical correlation is obtained based on genetic algorithms search engine over a dimensional analysis of the two-phase flow heat transfer problem. (author)

2006-01-01

152

The usage of transfer coefficients to describe radionuclide transport from a cow's diet to its milk  

International Nuclear Information System (INIS)

The terms 'transfer coefficient', 'transfer function' and 'transfer rate' are used to describe the transport of radionuclides from a cow's diet to her milk. Simple derivation of these parameters, their interpretations and interrelationships are given, and possible misinterpretations of published values due to imprecise definitions or incorrectly supplied or omitted units are reviewed. (author)

1980-01-01

153

Evaluation of the heat transfer coefficient in thermal shock of alumina disks  

International Nuclear Information System (INIS)

[en] Disks of a high-purity commercial alumina powder were fabricated by slip casting, pre-calcined, sintered and machined with SiC paper (120 and 320 grit). The specimens were tested in thermal shock conditions from several temperatures (Ti) between 870 and 980 C using a high-velocity air jet at room temperature (T0). The temperature differential between the disk and the air jet was incremented in 10 C until crack propagation was detected. During the air impinging, the temperature was recorded on the lower specimen surface at the central point and at a peripheral one. The coefficient governing the convective heat transfer on the specimen surface, h, was estimated by fitting the calculated temperature profiles with those measured during the test. Three alternative models were proposed for the temperature calculations using a finite element analysis. (orig.)

2000-01-15

154

Interpretation of the linear coefficient of surface-plasmon dispersion  

International Nuclear Information System (INIS)

Microscopic theory predicts that the fluctuating charge of free-electron-metal surface plasmons will lie in the tail of the metallic electron gas, and that, as a consequence, the linear coefficient of surface-plasmon dispersion will be negative. The latter prediction is interpreted here using the virial theorem. At larger wave vectors the more rapidly attenuating electric field associated with a fluctuating charge that lies outside the bulk of a metal will move fewer electrons. The virial theorem relates this fact to a lower frequency. Were the fluctuating charge to lie inside a metal, then more of its electric field would move electrons as the field attenuation became more rapid. This, according to the virial theorem, would imply a positive dispersion coefficient.

1989-01-01

155

Interpretation of the linear coefficient of surface-plasmon dispersion  

Energy Technology Data Exchange (ETDEWEB)

Microscopic theory predicts that the fluctuating charge of free-electron-metal surface plasmons will lie in the tail of the metallic electron gas, and that, as a consequence, the linear coefficient of surface-plasmon dispersion will be negative. The latter prediction is interpreted here using the virial theorem. At larger wave vectors the more rapidly attenuating electric field associated with a fluctuating charge that lies outside the bulk of a metal will move fewer electrons. The virial theorem relates this fact to a lower frequency. Were the fluctuating charge to lie inside a metal, then more of its electric field would move electrons as the field attenuation became more rapid. This, according to the virial theorem, would imply a positive dispersion coefficient.

Feibelman, P.J. (Sandia National Laboratories, Albuquerque, New Mexico 87185 (US))

1989-08-15

156

An experimental apparatus measuring convective heat transfer coefficient from a heated fine wire traversing in nanofluids  

International Nuclear Information System (INIS)

[en] Most of the previous convection experiments for nanofluids have been performed for internal tube flow with constant heat flux boundary condition. In contrast, a simple experimental apparatus measuring convective heat transfer coefficient from a heated wire to external nanofluids is proposed and its working principles are explained in detail. The convective heat transfer coefficient provided by the present system might be used as a useful indication justifying the adoption of prepared nanofluids as new efficient heat transfer fluids. Validation experiments by comparing convective heat transfer coefficients between the conventional correlation and measured values are carried out for base fluids. Also the effect of increased thermal conductivity of nano lubrication oil on the enhancement of convective heat transfer coefficient is investigated

2011-01-01

157

Wall heat transfer coefficient for condensation and boiling in forced convection of sodium  

International Nuclear Information System (INIS)

[en] The wall heat transfer coefficient for sodium boiling and condensation in forced convective flow is theoretically derived by using the momentum-heat transfer analogy and the logarithmic law for velocity distribution in the liquid film. Only one constant in the logarithmic form is empirically determined. The results are insensitive to some of the approximations used, namely in the evaluation of E and of /tau/ /SUB i/ //tau/ /SUB w/. The results from the suggested correlation are in good agreement with the Zeigarnick and Litvinov data over the range of parameters that were specified in their experiments, while the Chen and NATOF correlations predict lower heat transfer coefficients. The suggested correlation predicts well the data in the high-heat transfer coefficient region. It can be argued that the data in the low heat transfer coefficient region are affected by unstable flow conditions and the uncertainties in the saturation-temperature measurements

1982-01-01

158

An experimental apparatus measuring convective heat transfer coefficient from a heated fine wire traversing in nanofluids  

Energy Technology Data Exchange (ETDEWEB)

Most of the previous convection experiments for nanofluids have been performed for internal tube flow with constant heat flux boundary condition. In contrast, a simple experimental apparatus measuring convective heat transfer coefficient from a heated wire to external nanofluids is proposed and its working principles are explained in detail. The convective heat transfer coefficient provided by the present system might be used as a useful indication justifying the adoption of prepared nanofluids as new efficient heat transfer fluids. Validation experiments by comparing convective heat transfer coefficients between the conventional correlation and measured values are carried out for base fluids. Also the effect of increased thermal conductivity of nano lubrication oil on the enhancement of convective heat transfer coefficient is investigated.

Lee, Shin Pyo [Kyonggi University, Suwon (Korea, Republic of)

2011-01-15

159

Heat transfer coefficients of individual rows for fin-and-tube heat exchangers  

International Nuclear Information System (INIS)

The row-by-row heat transfer characteristics of fin-and-tube heat exchangers having wavy fins were experimentally investigated. Three samples having different rows (one, tow and three) were tested. Results show that the heat transfer coefficient is strongly dependent on the tube row. The heat transfer coefficient of the first row is larger than those of second or third rows. However, the difference decreases as the Reynolds number increases. The heat transfer coefficients of the second and the third row are approximately the same, probably due to increased mixing of bulk flow by wavy channels. Although samples have different tube row, the heat transfer coefficients of same row are approximately the same.

2004-01-01

160

Prediction of mass-transfer coefficient for solute transport in porous media.  

UK PubMed Central (United Kingdom)

Several previously reported laboratory studies related to transport of solutes through packed columns were utilized to develop predictive relationships for mass-transfer rate coefficient. The data were classified into two groups: those obtained under rate-limited mass transfer between mobile and immobile water regions (physical nonequilibrium conditions), and those derived from rate-limited mass transfer between instantaneous and slow sorption sites (sorption nonequilibrium conditions). The mass-transfer coefficient in all these studies was obtained by fitting breakthrough data to a transport model employing a first-order rate limitations with a "constant" mass-transfer coefficient, independent of flow conditions. This study demonstrated that the mass-transfer coefficient in these models is dependent on system parameters including pore-water velocity, length-scale, retardation coefficient, and particle or aggregate size. Predictive relationships were developed, through regression analysis, relating mass-transfer coefficient to residence time. The developed relationships adequately estimated previously reported field mass-transfer values. Successful simulations of field desorption data reported by Bahr [J. Contam. Hydrol. 4 (1989) 205] further demonstrate the potential applicability of the developed relationships.

Maraqa MA

2001-07-01

 
 
 
 
161

Prediction of mass-transfer coefficient for solute transport in porous media.  

UK PubMed Central (United Kingdom)

Several previously reported laboratory studies related to transport of solutes through packed columns were utilized to develop predictive relationships for mass-transfer rate coefficient. The data were classified into two groups: those obtained under rate-limited mass transfer between mobile and immobile water regions (physical nonequilibrium conditions), and those derived from rate-limited mass transfer between instantaneous and slow sorption sites (sorption nonequilibrium conditions). The mass-transfer coefficient in all these studies was obtained by fitting breakthrough data to a transport model employing a first-order rate limitations with a "constant" mass-transfer coefficient, independent of flow conditions. This study demonstrated that the mass-transfer coefficient in these models is dependent on system parameters including pore-water velocity, length-scale, retardation coefficient, and particle or aggregate size. Predictive relationships were developed, through regression analysis, relating mass-transfer coefficient to residence time. The developed relationships adequately estimated previously reported field mass-transfer values. Successful simulations of field desorption data reported by Bahr [J. Contam. Hydrol. 4 (1989) 205] further demonstrate the potential applicability of the developed relationships.

Maraqa MA

2001-12-01

162

Fuel-to-cladding heat transfer coefficient into reactor fuel element  

International Nuclear Information System (INIS)

[en] Models describing the fuel-to-cladding heat transfer coefficient in a reactor fuel element are reviewed critically. A new model is developed with contributions from solid, fluid and radiation heat transfer components. It provides a consistent description of the transition from an open gap to the contact case. Model parameters are easily available and highly independent of different combinations of material surfaces. There are no restrictions for fast transients. The model parameters are fitted to 388 data points under reactor conditions. For model verification another 274 data points of steel-steel and aluminium-aluminium interfaces, respectively, were used. The fluid component takes into account peak-to-peak surface roughnesses and, approximatively, also the wavelengths of surface roughnesses. For minor surface roughnesses normally prevailing in reactor fuel elements the model asymptotically yields Ross' and Stoute's model for the open gap, which is thus confirmed. Experimental contact data can be interpreted in very different ways. The new model differs greatly from Ross' and Stoute's contact term and results in better correlation coefficients. The numerical algorithm provides an adequate representation for calculating the fuel-to-cladding heat transfer coefficient in large fuel element structural analysis computer systems. (orig.)[de] Modelle zum Waermedurchgang im Bereich zwischen Huelle und Brennstoff eines Brennstabs werden kritisch untersucht. Es wird ein neues Modell entwickelt, das aus einem Spaltanteil, einem Strahlungsanteil und einem Kontaktterm besteht. Dieses Modell beschreibt den Uebergang vom offenen Spalt zum Kontaktfall in sich konsistent, es enthaelt nur leicht zugaengliche Stoff-und Geometrieparameter, es weist eine sehr weitgehende Unabhaengigkeit von verschiedenen Werkstoffpaarungen auf, und es enthaelt keine Einschraenkungen im Hinblick auf die Anwendung von schnell ablaufenden Stoerfaellen. Das Modell wird an 388 Messpunkten unter Reaktorbedingungen geeicht. Fuer Voruntersuchungen wurden weitere 274 Messpunkte an St-St-bzw. Al-Al-Paarungen verwendet. Im Spaltenanteil werden sowohl Einfluesse von Rauhigkeitsspitzen als auch von Welligkeiten naeherungsweise beruecksichtigt. Fuer geringe Einfluesse von Rauhigkeiten, wie sie beim Brennstab vorliegen, gehen die entwickelten Gleichungen in das klassische Modell fuer den Waermedurchgang im offenen Spalt von Ross und Stoute ueber, das somit bestaetigt wird. Im Kontaktfall kann das vorliegende experimentelle Material auf sehr verschiedene Weise interpretiert werden. Eine neu entwickelte Korrelation unterscheidet sich wesentlich vom Kontaktterm wie er im Ross und Stoute-Modell verwendet wird und fuehrt zu besseren Korrelationskoeffizienten. Der gesamte entwickelte Formelapparat zur Berechnung des Waermedurchgangs eignet sich speziell fuer den Einsatz im Rahmen von integralen Brennstab-Rechenprogrammen. (orig.)

1979-01-01

163

Experimental investigation of thermal conductivity coefficient and heat exchange between fluidized bed and inclined exchange surface  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 years owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.

B. Stojanovic; J. Janevski; M. Stojiljkovic

2009-01-01

164

Experimental investigation of thermal conductivity coefficient and heat exchange between fluidized bed and inclined exchange surface  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The paper presents experimental research of thermal conductivity coefficients of the siliceous sand bed fluidized by air and an experimental investigation of the particle size influence on the heat transfer coefficient between fluidized bed and inclined exchange surfaces. The measurements were performed for the specific fluidization velocity and sand particle diameters d p=0.3, 0.5, 0.9 mm. The industrial use of fluidized beds has been increasing rapidly in the past 20 ye (more) ars owing to their useful characteristics. One of the outstanding characteristics of a fluidized bed is that it tends to maintain a uniform temperature even with nonuniform heat release. On the basis of experimental research, the influence of the process's operational parameters on the obtained values of the bed's thermal conductivity has been analyzed. The results show direct dependence of thermal conductivity on the intensity of mixing, the degree of fluidization, and the size of particles. In the axial direction, the coefficients that have been treated have values a whole order higher than in the radial direction. Comparison of experimental research results with experimental results of other authors shows good agreement and the same tendency of thermal conductivity change. It is well known in the literature that the value of the heat transfer coefficient is the highest in the horizontal and the smallest in the vertical position of the heat exchange surface. Variation of heat transfer, depending on inclination angle is not examined in detail. The difference between the values of the relative heat transfer coefficient between vertical and horizontal heater position for all particle sizes reduces by approximately 15% with the increase of fluidization rate.

Stojanovic, B.; Janevski, J.; Stojiljkovic, M.

2009-06-01

165

Improvement of the transfer coefficient of GaAs/Si spin-valve transistors  

Energy Technology Data Exchange (ETDEWEB)

Nowadays GaAs/Si hot electron spin-valve transistors can be readily made using the vacuum bonding technique. They show sharp variations in collector current in small magnetic fields, good for sensor applications. However, the transfer coefficient of the device, defined as collected current over injected current, is only around 10{sup -4}%. We address the structural properties of GaAs/Si spin-valve transistors that influence the transfer coefficient. An improvement of the transfer coefficient of more than one order of magnitude is obtained by implementing a GaAs/AlAs emitter launcher maintaining 93% of relative collector current change.

Dessein, K. E-mail: dessein@imec.be; Anil Kumar, P.S.; Lagae, L.; Boeck, J. de; Delaey, L.; Borghs, G

2001-05-01

166

Improvement of the transfer coefficient of GaAs/Si spin-valve transistors  

International Nuclear Information System (INIS)

Nowadays GaAs/Si hot electron spin-valve transistors can be readily made using the vacuum bonding technique. They show sharp variations in collector current in small magnetic fields, good for sensor applications. However, the transfer coefficient of the device, defined as collected current over injected current, is only around 10-4%. We address the structural properties of GaAs/Si spin-valve transistors that influence the transfer coefficient. An improvement of the transfer coefficient of more than one order of magnitude is obtained by implementing a GaAs/AlAs emitter launcher maintaining 93% of relative collector current change.

2001-01-01

167

Experimental measurement of variation of heat transfer coefficient and temperature gradients in 16'' deep fluidised beds  

International Nuclear Information System (INIS)

[en] The object of the experiments was to choose suitable particulate materials for a fluidised bed cooler, to test a deep fluidised bed for uniformity of heat transfer coefficient, and to explore the temperature distribution in a centrally heated annular fluidised bed. This memorandum records the techniques used and some of the practical aspects involved, together with the performance results obtained, for the assistance of other experimenters who may wish to use fluidised beds as a laboratory technique. Mathematical correlation of the results has not been attempted since some of the properties of the bed material were not known and to determine them was beyond the scope of the work programme. Rather, we have compared our results with those of other experimenters. Graphite tubes, for use in steady state thermal stress experiments, are to be heated by a graphite radiant heater situated in the bore and cooled on the outer surface. The tubes are 2 cm. bore, 8 cm. outside diameter and 48 cm. long. The outside temperature of the tubes is to be between 500 deg. C. and 1500 deg. C. It is estimated that the heat transfer rate required for fracture at the outer surface is 30 watts/cm2. This could readily be achieved by cooling with liquid metals, water or high velocity gas. However, serious problems of either materials compatibility or mechanical complexity make these undesirable. A water-cooled fluidised bed of compatible solids fluidised with nitrogen gas can overcome most of these problems and give heat transfer coefficients close to that required, vis. about 0.1 w/cm C . A coolant bed about 20'' long would be required and an annulus of about 2'' radial width round the specimen was considered to be practicable

1962-01-01

168

Micro Scale Surface Modifications for Heat Transfer Enhancement.  

UK PubMed Central (United Kingdom)

In this experimental study, two surface modification techniques were investigated for their effect on heat transfer enhancement. One of the methods employed the particle (grit) blasting to create micro scale indentations, while the other used plasma spray coating to create micro scale protrusions. The test surfaces were characterized using SEM and confocal scanning laser microscopy. Due to the surface modifications, the actual surface area was increased up to 2.8x compared to the projected base area, and the arithmetic mean roughness value (Ra) was determined to vary from 0.3 ?m for the reference smooth surface, to 19.5 ?m for the modified surfaces. Selected samples with modified surfaces along with the reference smooth surface were then evaluated for their heat transfer performance in spray cooling tests. The cooling system had vapor-atomizing nozzles, and used anhydrous ammonia as the coolant in order to achieve heat fluxes up to 500 W/cm2 representing a thermal management setting for high power systems. Experimental results showed that the micro scale surface modifications enhanced heat transfer coefficients up to 76% at 500 W/cm2 compared to the smooth surface, and demonstrated the benefits of these practical surface modification techniques to enhance two-phase heat transfer process.

Bostanci H; Singh V; Kizito JP; Rini DP; Seal S; Chow LC

2013-09-01

169

On the radial heat transfer coefficient in grooved heat pipe  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is well known that microscopic effects are important in the evaluation of the radial heat transfer within a grooved heat pipe evaporator. We develop a multi-scale model which is composed of two parts, macroscopic and microscopic, which cannot be decoupled from each other. In our study, we include...

Rossomme, Séverine; Goffaux, Cécile; Hillewaert, Koen; Colinet, Pierre

170

Sound conversion phenomena at the free surface of liquid helium. II. Experimental determination of acoustic coefficients and surface absorption coefficients  

International Nuclear Information System (INIS)

[en] The acoustic coefficients of reflection, transmission, and transformation of first-, second-, and gas sound waves incident normally on the free surface of liquid helium have been determined. The experimental results are compared with the theory developed in Part I of this paper. It is shown that equilibrium theories of boundary conditions disagree with the experiments. Nonequilibrium theories, however, which take into account that mass and energy transport processes occur at the liquid-vapor interface of helium II, lead to a very good description of the experimental data below 2 K. Within experimental accuracy the measurements fully confirm several kinetic models of evaporation and energy transport processes. Near the lambda point, deviations from the theory have been found which might be attributed to influences of critical phenomena. The surface absorption coefficients of first-, second-, and gas sound waves could be deduced from the experimental data on the acoustic coefficients, and it is shown that, in agreement with the theory, appreciable energy dissipation occurs at the free surface of helium II when a second-sound or a gas sound wave is incident

1983-05-01

171

Study of Oxygen Mass Transfer Coefficient in Microbial Leaching of Uranium  

International Nuclear Information System (INIS)

Oxygen mass transfer coefficient is one of the most important parameters in the design of aerobic process bioreactor, which is represented by the overall volumetric oxygen mass transfer. The purpose of this article was the investigation of the mass transfer coefficient in the vast range of operational parameters in a stirred tank reactor. The effects of cell concentration, stirred power consumption and apparent air velocity on the mass transfer coefficient show that oxygen mass transfer in microbial leaching of uranium and in this range of parameter is not limited in these experiments. The overall volumetric oxygen mass transfer was determined in the range of 36-84 hr-1. Agreements of the suggested mathematical correlation for predicting the mass transfer were also evaluated. The results showed that the equation based on the rpm and/or power consumption and apparent air velocity specifies a good agreement with the experimental results with the coefficient of determination of R2=94.2 and 93.4. It was concluded that the introduced models are suitable for evaluation of the mass transfer coefficient in the microbial leaching of uranium.

2013-01-01

172

Estimation of overall heat transfer coefficient of cooling system in RF capacitive hyperthermia  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The study presented in this article involves the estimation of the overall heat transfer coefficient of cooling system in RF capacitive hyperthermia treatment using inverse problem based on the conjugate gradient method to provide improved distri...

Seyed Ali Aghayan; Dariush Sardari; Seyed Rabii Mahdi Mahdavi; Mohammad Hasan Zahmatkesh

173

Determination of heat transfer coefficient during high pressure frying of potatoes  

UK PubMed Central (United Kingdom)

Besides traditional atmospheric frying, high pressure (super-atmospheric) frying might be an alternative approach to the frying of food products. In this study, convective heat transfer coefficient during atmospheric and high pressure frying was compared. For this purpose, a pressure cooker was modified to allow the immersion of a sample into frying oil under pressure and temperature measurement of sample and oil. Heat transfer coefficient versus frying time was determined on potato slabs using changes of total mass of the experimental set-up. At the pressure of 2bar, the results showed an almost doubled heat transfer coefficient compared to the atmospheric pressure frying. The knowledge of heat transfer coefficient during pressure frying is expected to allow accurate determination of temperature distribution and hence the kinetic calculations to lead to development of an alternative frying process.

Erdogdu Ferruh; Dejmek Petr

2010-02-01

174

Experimental Approach to Determine the Heat Transfer Coefficient in Directional Solidification Furnaces.  

Science.gov (United States)

The heat transfer coefficient between a molten charge and its surroundings in a Bridgman furnace was experimentally determined using in-situ temperature measurement. The ampoule containing an isothermal melt was suddenly moved from a higher temperature zo...

M. Banan R. T. Gray W. R. Wilcox

1992-01-01

175

Thermal performance analysis for heat exchangers having a variable overall heat transfer coefficient.  

Science.gov (United States)

The classic, conventional analysis for the thermal performance of heat exchangers is based on three assumptions: constant fluid flow rate, constant specific heat fluids, and constant overall heat transfer coefficient. Our analysis describes a general appr...

J. C. Conklin E. Granryd

1991-01-01

176

Parameter estimation method for flash thermal diffusivity with two different heat transfer coefficients.  

Science.gov (United States)

Determining thermal diffusivity using flash diffusivity tests at high temperatures is investigated using parameter estimation. One aspect is development of a method for determining two different heat transfer coefficients, one at the heated face and one a...

J. V. Beck R. Dinwiddie

1995-01-01

177

Measurement of radon diffusion coefficients for Japanese surface soils  

International Nuclear Information System (INIS)

The radon diffusion coefficient for soil, D, is a very important parameter used to estimate radon dose for uranium-bearing waste. Many Ds were measured in the uranium mill tailing remediation action project in the US, and a formula for the estimation of diffusion coefficient, Rogers's formula, was proposed. However, it is uncertain whether Rogers's formula is applicable to Japanese soils because most of them have come from volcanic ash and contain much water. This paper describes the development of a measurement apparatus for D using a lump response transient method and a step response transient method, and presents measured D values for Japanese surface soils. Measured alpha ray count curves are good in agreement with those of theory. This shows that radon transportation in soil can be described using Fick's law. Furthermore, the measured effective D values are good in agreement with those of Rogers's formula. This means that Rogers's formula can be applied to Japanese soils. (author)

2008-01-01

178

Measurement of heat transfer coefficient in the transition region of tube flow  

International Nuclear Information System (INIS)

[en] Heat transfer coefficient and friction factor were obtained experimentally for a circular tube in the transition region from the laminar to the turbulent flow. The measurements were made for two different kinds of intermittently turbulent regions; i.e., puff and slug. A relation between the heat transfer coefficient and the intermittency was examined. Variation of gas temperature was observed and found to be also intermittent. (author)

1982-01-01

179

137Cs transfer coefficients from fodder to cow milk  

International Nuclear Information System (INIS)

The transfer of 137Cs from the components of cows' diets to milk was followed in detail on 10 farms in the north-eastern region of Italy (Friuli-Venezia Giulia) from June to July 1988. Samples of milk, grass and other components of the cows' diet were collected regularly and analysed for radiocaesium content. The transfer factors, calculated for 137Cs after a four-week feeding period with contaminated silage, were higher (0.0064) than those calculated in 1987 in the same area (0.0030). This may be attributable to the fact that the 137Cs associated to the forage administrated to cows in 1988 was completely incorporated in the plant and thus more assimilable to the cattle. (Author).

1993-01-01

180

Influence of temperature on heat transfer coefficient during moderate vacuum deep-fat frying  

UK PubMed Central (United Kingdom)

The objective of this study is to analyze the influence of temperature and reduced pressure on the convective heat transfer coefficient, h, during frying of products with different area/volume ratio. h was determined from surface temperature and moisture loss experimental data during frying of potato cylinders and “churros”, at different oil temperatures (100, 120 and 140°C) and moderate vacuum (19.5–25.9kPa). The results obtained during vacuum frying were compared with those obtained at atmospheric pressure, both for the same oil temperature (140°C) and for the same thermal gradient (40°C). During frying, h changes considerably, reaching a maximum between 700–1600Wm?2K?1 in vacuum frying and 800–2000Wm?2K?1 in atmospheric frying. To quantify the effect of oil temperature, pressure and size of the product on h, a parameter called “bubbling efficiency”, BE, was defined. BE relates the bubble departure radius and the area/volume ratio of the product. An equation (the derivative of the Gompertz function) was proposed to estimate the mean heat convective coefficients for each frying condition as a function of BE (R2=0.957). The relation between h and BE shows a maximum corresponding to an optimal bubbling pattern. Most of the vacuum frying settings are outside this optimum, being affected by the insulation effect of bubbles covering the surface.

Mir-Bel J; Oria R; Salvador ML

2012-11-01

 
 
 
 
181

Determination and correlation of mass transfer coefficients in a stirred cell  

International Nuclear Information System (INIS)

[en] In the proposed Molten Salt Breeder Reactor flowsheet, a fraction of the rare earth fission products is removed from the fuel salt in mass transfer cells. To obtain design parameters for this extraction, the effect of cell size, blade diameter, phase volume, and agitation rate on the mass transfer for a high density ratio system (mercury/water) in nondispersing square cross section contactors was determined. Aqueous side mass transfer coefficients were measured by polarography over a wide range of operating conditions. Correlations for the experimental mass transfer coefficients as functions of the operating parameters are presented. Several techniques for measuring mercury-side mass transfer coefficients were evaluated and a new one is recommended

1975-01-01

182

Transfer coefficients to terrestrial food products in equilibrium assessment models for nuclear installations  

International Nuclear Information System (INIS)

Transfer coefficients have become virtually indispensible in the study of the fate of radioisotopes released from nuclear installations. These coefficients are used in equilibrium assessment models where they specify the degree of transfer in food chains of individual radioisotopes from soil to plant products and from feed or forage and drinking water to animal products and ultimately to man. Information on transfer coefficients for terrestrial food chain models is very piecemeal and occurs in a wide variety of journals and reports. To enable us to choose or determine suitable values for assessments, we have addressed the following aspects of transfer coefficients on a very broad scale: (1) definitions, (2) equilibrium assumption, which stipulates that transfer coefficients be restricted to equilibrium or steady rate conditions, (3) assumption of linearity, that is the idea that radioisotope concentrations in food products increase linearly with contamination levels in the soil or animal feed, (4) methods of determination, (5) variability, (6) generic versus site-specific values, (7) statistical aspects, (8) use, (9) sources of currently used values, (10) criteria for revising values, (11) establishment and maintenance of files on transfer coefficients, and (12) future developments. (auth)

1980-01-01

183

Determining the surface roughness coefficient by 3D Scanner  

Directory of Open Access Journals (Sweden)

Full Text Available Currently, several test methods can be used in the laboratory to determine the roughness of rock joint surfaces.However, true roughness can be distorted and underestimated by the differences in the sampling interval of themeasurement methods. Thus, these measurement methods produce a dead zone and distorted roughness profiles.In this paper a new rock joint surface roughness measurement method is presented, with the use of a camera-typethree-dimensional (3D) scanner as an alternative to current methods. For this study, the surfaces of ten samples oftuff were digitized by means of a 3D scanner, and the results were compared with the corresponding Rock JointCoefficient (JRC) values. Up until now such 3D scanner have been mostly used in the automotive industry, whereastheir use for comparison with obtained JRC coefficient values in rock mechanics is presented here for the first time.The proposed new method is a faster, more precise and more accurate than other existing test methods, and is apromising technique for use in this area of study in the future.

Karmen Fifer Bizjak

2010-01-01

184

MM98.04 Measurement of temperature and determination of heat transfer coefficient in backward can extrusion  

DEFF Research Database (Denmark)

Temperature is measured during backward can extrusion of steel. The process is characterised by large deformations and very high surface pressure. In the experiments, a can in low carbon steel with a lubrication layer of phosphate soap is formed. The temperature is measured by thermocouples in the die insert. The die insert is divided into two halves where the thermocouples are welded to the end of milled grooves in the lower part. The temperature of the workpiece is measured by welding a thermocouple directly onto the free surface.All of the temperature measurements in the tool and the workpiece are compared with a number of FEM simulations computed with different heat transfer coefficients. The current heat transfer coefficient is determined from the simulations.

Henningsen, Poul; Hattel, Jesper Henri

1998-01-01

185

Analysis of wind-driven flow and external convective heat transfer coefficients for the BESTEST model building  

Energy Technology Data Exchange (ETDEWEB)

This study demonstrated the capability of a computational fluid dynamics (CFD) commercial simulation package in predicting air flow and heat transfer coefficients at external building surfaces. Studies have shown that convective heat transfer has a significant influence on the energy balance of a room. Sensitivity calculations have also shown that convective heat transfer coefficient values can lead to differences of 20 to 40 per cent in energy demand. In particular, this study demonstrated the feasibility of simulating real low-rise building external wind-driven flow and determining useful values of convective heat transfer coefficients. The simulations were performed using the International Energy Agency's Building and Energy Simulation Test (BESTEST), on which the ASHRAE Standard 140 is based. In this study, ANSI/ASHRAE Standard 140-2001 was applied in modeling the effects of wind speed and temperatures differences between the building surfaces and the external air. Simulated air velocity values have demonstrated the regular behaviour of air direction. Boundary conditions were also discussed. 27 refs., 19 figs.

Emmel, M.G.; Mendes, N. [Pontifical Catholic Univ. of Parana, Curitiba (Brazil). Thermal Systems Laboratory

2005-07-01

186

Heat recovery without heat transfer surfaces  

Energy Technology Data Exchange (ETDEWEB)

Most heat recovery systems involve heat transfer surfaces. This fact means high initial investment, high maintenance costs and efficiency decrease because of the fouling of the heat transfer surfaces. This article describes the working principles of a surface-less heat recovery system, the mathematical approach to treat such systems and what parameters can be used to evaluate and compare this system with others. The article concludes with numerical examples.

Finkelstein, E.

1983-01-01

187

Extended surface heat transfer in fluidized beds  

Energy Technology Data Exchange (ETDEWEB)

The emerging technology of fluidized bed combustion of coal and recognition of the fluidized bed heat exchanger as a heat transfer device with great potential have regenerated interest in the heat transfer process between a gas fluidized bed and immersed tubes with extended surfaces or fins. In the present work, a critical review of the effects of some important fluidization and fin geometry parameters on the bed-to-tube-surface heat transfer is presented. The significant features of finned tube heat transfer are discussed and areas requiring further attention are suggested.

Kolar, A.K.; Sastri, V.M.K.

1987-07-01

188

Maximum heat transfer coefficient between a horizontal tube and a gas-solid fluidized bed  

Energy Technology Data Exchange (ETDEWEB)

Experiments have been conducted to measure the maximum heat transfer coefficient between an electrically heated single horizontal tube and air-solid square fluidized beds of glass beads, dolomite, sand, silicon carbide and alumina particles. The effect of particle size, shape, density, and specific heat, tube size, bed depth, heat flux, and distributor design on maximum heat transfer rate has been investigated. Experimental values of maximum heat transfer coefficient are compared with the values of maximum heat transfer coefficient predicted by the existing correlations. None of these correlations is found to be adequate to reproduce the present data. Therefore a new correlation has been proposed on the basis of the data and then examined to assess its reliability on the basis of available data in the literature. In addition, the existing correlations for bed porosity and optimum mass fluidizing velocity, have been examined on the basis of our data and a new correlation is given for the bed porosity.

Grewal, N.S.; Saxena, S.C.

1981-01-01

189

In-reactor measurement of fuel-to-sheath heat transfer coefficients between UO2 and stainless steel  

International Nuclear Information System (INIS)

[en] An experimental technique has been developed to measure the fuel-to-sheath heat transfer coefficient in operating UO2 fuel elements in a more direct manner than previously possible. During in-reactor operation, the thermal response of the fuel (measured by thermocouples placed near the outer surface of the UO2 pellets) and the dimensional response of the sheathing (measured by attached strain gauges) were monitored while varying either the element internal gas pressure or the element power. Detailed quantitative analysis yields both the solid and fluid components of fuel-to-sheath heat transfer as a function of gap width, gas pressure and composition, and interfacial pressure. (author)

1977-01-01

190

Relationship between mass transfer coefficient and liquid flow velocity in heterogenous biofilms using microelectrodes and confocal microscopy.  

UK PubMed Central (United Kingdom)

The relationship between local mass transfer coefficient and fluid velocity in heterogenous biofilms was investigated by combining microelectrodes and confocal scanning laser microscopy (CSLM). The biofilms were grown for up to 7 days and consisted of cell clusters separated by interstitial channels. Mass transfer coefficient depth profiles were measured at specific locations in the cell clusters and channels at average flow velocities of 2.3 and 4.0 cm/s. Liquid flow velocity profiles were measured in the same locations using a particle tracking technique. The velocity profiles showed that flow in the open channel was laminar. There was no flow at the top surface of the biofilm cell clusters but the mass transfer coefficient was 0.01 cm/s. At the same depth in a biofilm channel, the flow velocity was 0.3 cm/s and the mass transfer coefficient was 0.017 cm/s. The mass transfer coefficient profiles in the channels were not influenced by the surrounding cell clusters. Local flow velocities were correlated with local mass transfer coefficients using a semi-theoretical mass transfer equation. The relationship between the Sherwood number (Sh,) the Reynolds number (Re,) and the Schmidt number (Sc) was found using the experimental data to find the dimensionless empirical constants (n1, n2, and m) in the equation Sh = n(1) + n(2)Re(m) Sc(1/3). The values of the constants ranged from 1.45 to 2.0 for n(1), 0.22 to 0.28 for n(2), and 0.21 to 0.60 for m. These values were similar to literature values for mass transfer in porous media. The Sherwood number for the entire flow cell was 10 when the bulk flow velocity was 2.3 cm/s and 11 when the bulk flow velocity was 4.0 cm/s. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 681-688, 1997.

Stoodley P; Yang S; Lappin-Scott H; Lewandowski Z

1997-12-01

191

Measurement of Mass Transfer Coefficients for Adsorptive Bulk Gas Separation with Velocity Variations  

Energy Technology Data Exchange (ETDEWEB)

The concentration breakthrough curves were examined to predict mass transfer coefficients of nitrogen and oxygen in adsorption column for design data of PSA process. Experimental Breakthrough curves for bulk gas flow were compared with theoretical simulation results. For quantitative analysis of the adsorption, coupled Langmuir isotherm was considered and LDF model was used to describe the mass transfer effect. In the experimental and theoretical and theoretical results, it was found that mass transfer coefficient was not affected by flow rate but strongly affected by pressure. As a result of this tendency, mass transfer resistance in this system was proved to belong to the macropore diffusion controlling region and the mass transfer coefficients could be expressed by exponential functions of pressure change. The mass transfer coefficients for one component, nitrogen or oxygen, were successfully applied to breakthrough curves for bulk mixed gases. The experimental curves were reasonably in consistent with the theoretical curves and the error time was less than 5 percent. 9 refs., 11 figs., 4 tabs.

Choi, M.H.; Suh, S.S. [Department of Chemical Engineering, Hongik University, Seoul (Korea); Min, J.H. [Hyundai Industrial Research Institute, Hyundai Heavy Industries (Korea)

1999-04-01

192

Prediction of mass transfer coefficients in a pulsed packed extraction column using effective diffusivity  

Directory of Open Access Journals (Sweden)

Full Text Available The volumetric overall mass transfer coefficients have been measured in a pulsed packed extraction column using diffusion model for two different liquid-liquid systems. The effects of operational variables such as pulsation intensity and dispersed and continuous phase flow rates on volumetric overall mass transfer coefficients have been investigated. Effective diffusivity is substituted for molecular diffusivity in the Gröber equation for prediction of dispersed phase overall mass transfer coefficients. The enhancement factor is determined experimentally and therefrom an empirical correlation is derived for prediction of effective diffusivity as a function of Reynolds number, Schmidt number and viscosity ratio. Good agreement between prediction and experiments was found for all operating conditions that were investigated.

M. Torab-Mostaedi; J. Safdari

2009-01-01

193

Prediction of mass transfer coefficients in a pulsed packed extraction column using effective diffusivity  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english The volumetric overall mass transfer coefficients have been measured in a pulsed packed extraction column using diffusion model for two different liquid-liquid systems. The effects of operational variables such as pulsation intensity and dispersed and continuous phase flow rates on volumetric overall mass transfer coefficients have been investigated. Effective diffusivity is substituted for molecular diffusivity in the Gröber equation for prediction of dispersed phase ov (more) erall mass transfer coefficients. The enhancement factor is determined experimentally and therefrom an empirical correlation is derived for prediction of effective diffusivity as a function of Reynolds number, Schmidt number and viscosity ratio. Good agreement between prediction and experiments was found for all operating conditions that were investigated.

Torab-Mostaedi, M.; Safdari, J.

2009-12-01

194

Film mass transfer coefficient for the prediction of volatile organic compound evaporation rate from open water basin  

Directory of Open Access Journals (Sweden)

Full Text Available The evaporation of volatile organic compounds(VOCs) from treatment, storage, disposal facility(TSDF) is an important air pollution issue because of the evaporation quantity and toxicity and/or carcinogenicity. This paper concerns VOC evaporation from open water basins such as the equalization basin and nonaerate surface impoundments in a wastewater treatment plant. The amount of VOCs evaporation from open water basins can be predicted by using the two-film model that requires two mass transfer coefficients including liquid-film(kLand gas-film (kG)mass transfer coefficients. This paper studies the effect of the wind speed and water temperature on these coefficients. A series of volatile organic compound evaporation experiments were performed in a wind tunnel-water tank system in which both the wind speed and the water temperature were easily controlled. The wind speeds and the water temperatures were varied from 0 to 4.8 m/s and 25oC to 45oC, respectively. The air temperatures for all experiment were 28+-2 oC. The kL and kG for various wind speed and watertemperatures were determined from unsteady state evaporation of toluene and methanol from water. The mass transfer coefficients(kL and kG)were then developed based on the experimental data to predict the overall mass transfer coefficient(KOL).Unlike the existing correlations, our empirical equations correlate both the effect of the wind speed and water temperature to kL and kG and have been verified by laboratory experiments with three volatile organic compounds(acetone,MEK and chloroform).Predictions of the KOL by using these correlations were generaly in good agreement with the evaporation data supporting the use of the correlations to predict the VOC evaporations from open water basins.

Charun Bunyakan; Preyaporn Tongsoi; Chakrit Tongurai

2001-01-01

195

Laser flash method for measurement of liquid metals heat transfer coefficients  

Science.gov (United States)

New laser flash technique for the measurement of heat transfer coefficients of liquid metals is presented. The thermal diffusivity of the liquid mercury has been studied experimentally over the room temperature range. The thermal conductivity coefficient has been calculated with the use of the reference data on density and heat capacity. Analysis of systematic errors of the measurements has shown that the data error is about 3%. Comparison of the obtained results with data available in publications has proved their reliability.

Stankus, S. V.; Savchenko, I. V.

2009-12-01

196

Transfer coefficient study of Sr-90 in the soil-grass-milk chain for Cuba  

International Nuclear Information System (INIS)

One of the most important problems in modern radioecology is the lack of able information about the features of radionuclide migration in tropical and subtropical environment. The development of nuclear energy and the enhancing in the applications of nuclear techniques in those latitudes indicate that studies in this area are necessary. Cuba is carrying out studies on radioecological characterization of the principal food chains in the country. One of the objectives of these studies is to define the values of the transfer coefficients to be used in the evaluation programs for the assessment of the radiological impact of practices which involve ionizing radiation. This paper shows the results obtained in the determination of Sr-90 transfer coefficients in soil-grass-milk food chain in 'La Quebrada', a place near the Havana City where an important part of the milk that the citizens consume is produced. Transfer coefficients for Sr-90 were calculated on the basis of data collected during 5 years in the region. Soil-grass transfer coefficients are in the range 0.18-5 while grass-milk coefficients are in the range of 1.2x10-4 - 6x10-3 day/L. These values are in accordance with values reported by other authors in the literature. (authors). 4 refs., 2 tabs

1996-01-01

197

Parameter estimation method for flash thermal diffusivity with two different heat transfer coefficients  

Energy Technology Data Exchange (ETDEWEB)

Determining thermal diffusivity using flash diffusivity tests at high temperatures is investigated using parameter estimation. One aspect is development of a method for determining two different heat transfer coefficients, one at the heated face and one at the opposite face. Both simulated exact and experimental data are used to illustrate the procedure. Although the heat transfer coefficients are different, assuming identical coefficients in the estimation process does not significantly affect the thermal diffusivity estimates. Insight into estimation of thermal diffusivity and other parameters is obtained from a study of the sensitivity coefficients. Although the thermal diffusivity is the primary parameter of interest, a measured signal proportional to the temperature rise also depends on the heat transfer coefficients and energy input, which are called nuisance parameters (if not of interest). As the temperatures increase above 1500 C, heat losses become very large and greatly influence the temperature response. By using insights from the study of the sensitivity coefficients for each of these parameters, the thermal diffusivity can be estimated despite the large heat losses.

Beck, J.V.; Dinwiddie, R.

1995-12-31

198

Heat-transfer coefficient with glancing flow around fuel elements and tubes  

International Nuclear Information System (INIS)

[en] This paper presents the construction of a schematic model of laminar heat-carrier flow with glancing flow around a bundle of tubes or fuel elements and the formulation, on this basis, of a unified dependence of the heat-transfer coefficient on the angle of attack. In calculating heat exchangers and steam generators with complex heat-carrier motion in the intertube space and in calculating fuel assemblies with partial blocking of the cross section, the heat-transfer coefficient is determined as a function of the angle of attack of the flux flowing around the tube or fuel element

1986-01-01

199

Experimental determination of the local heat transfer coefficient in a closely packed pin arrangement  

International Nuclear Information System (INIS)

The determination of the heat transfer coefficient of the pins of the Spallation Neutron Source is a very important problem for the development of this facility, as data for thermal and structural studies. For this purpose, a test apparatus was built, in scale 1:1, for the simulation of the thermal and hydraulical conditions of the Neutron Source. This apparatus is a pin bank, with one of the pins electrically heated. Performance of measurements gave the values for the heat transfer coefficient, here presented in the Nusselt Number form, and its local distribution. Results show the linear dependence of Nusselt Number on Reynolds Number, for a constant heat production. (orig.)

1982-01-01

200

Experimental prediction of heat transfer coefficients by use of a double-blow method  

Energy Technology Data Exchange (ETDEWEB)

A new method is proposed for evaluating heat transfer coefficients in a heat exchanger matrix. In comparison with the well known single-blow method, a new double-blow method offers prediction of heat transfer coefficients on both sides of the heat exchanger wall by using one run only, because temperatures of both fluids flowing through the heat exchanger matrix are changed and measured. The experimental technique, data collection procedure, and the method of analysis are derived from an analysis of the analytical solution of the transient response of gas-to-gas cross flow heat exchanger with finite wall capacitance. (orig.)

Gvozdenac, D.D. (ENCONET International Ltd., Coalville (United Kingdom))

1994-06-01

 
 
 
 
201

Spin transfer coefficients for the (p suprho,n suprho) reaction in the plane wave approximation  

CERN Multimedia

The spin transfer coefficients D sub n sub n (theta=0 .deg. ) for the intermediate energy charge exchange reaction (p suprho,n suprho) leading to the giant resonances in the continuum region are investigated. The dependence of the spin transfer coefficients on the nuclear wave function, the reaction Q-value, and the effective two-body interaction are studied using the plane wave approximation. It is shown that both the direct and the exchange parts of the tensor interaction play important roles in determining the D sub n sub n value.

Lee, H S; Kim, B T

1998-01-01

202

Variation of the transfer coefficient for radiocaesium transport to sheep's milk during a complete lactation period  

International Nuclear Information System (INIS)

[en] The variation with time in the transfer coefficient for radiocaesium transport to sheep's milk was measured during an entire lactation period. One hundred and forty ewes were used. The animals were segregated into groups of six ewes and throughout their lactation period, every week one of the groups was given a diet of ground wheat, contaminated with radiocaesium from the Chernobyl accident. The results showed an increase of radiocaesium activity concentration in the milk by a factor of three, over the 21-week lactation period. A significant correlation was found between transfer coefficients for radiocaesium and average daily milk yield. (Author)

1994-01-01

203

A technique for measuring convective heat transfer at rough surfaces  

Science.gov (United States)

A new method has been developed for measuring local heat transfer coefficients at rough surfaces. The technique was applied to an idealized section of a large scaled model of a turbine blade cooling passage to assess the effect of surface irregularities which result from the blade manufacturing process. The experimental method is described in full and the results are presented for tests on an isolated pin-fin situated in fully developed channel flow. The effect of the thermal conductivity of the roughness elements is discussed.

Wang, Zuolan; Ireland, P. T.; Jones, T. V.

1990-06-01

204

Investigation of mass transfer coefficient, extraction and dispersed phase local holdup in spray columns  

International Nuclear Information System (INIS)

In designing extraction columns many parameters must be considered such as mass transfer coefficients during formation, rising or falling and coalescence time, holdup, drop size and size distribution. Prediction of dispersed phase holdup is one of the most important parameter mentioned above. A laboratory spray column was constructed in our experimental works. Mass transfer coefficients, extraction percentage and local dispersed phase holdup were studied. Three physical systems with different physical properties and wide range of interfacial tensions, the most important physical property in our experiments, were used. It was found that the size of the mother drops produced by nozzles strongly depends on nozzle diameter. Most part of the mass transfer takes place in the nozzle tip and it increases as nozzles diameter decreases. Using multi orifices and single nozzles mass transfers were compared, taking into account the variation of dispersed phase hold up along the column.

2000-01-01

205

Measurement of the thermal conductivity and heat transfer coefficient of a binary bed of beryllium pebbles  

Energy Technology Data Exchange (ETDEWEB)

The four ITER partners propose to use binary beryllium pebble bed as neutron multiplier. Recently this solution has been adopted for the ITER blanket as well. In order to study the heat transfer in the blanket the effective thermal conductivity and the wall heat transfer coefficient of the bed have to be known. Therefore at Forschungszentrum Karlsruhe heat transfer experiments have been performed with a binary bed of beryllium pebbles and the results have been correlated expressing thermal conductivity and wall heat transfer coefficients as a function of temperature in the bed and of the difference between the thermal expansion of the bed and of that of the confinement walls. The comparison of the obtained correlations with the data available from the literature show a quite good agreement. (author)

Donne, M.D.; Piazza, G. [Forschungszentrum Karlsruhe GmbH Technik und Umwelt (Germany). Inst. fuer Neutronenphysik und Reaktortechnik; Goraieb, A.; Sordon, G.

1998-01-01

206

On the generalized correlation equation of two phase heat transfer coefficient in forced-convection boiling  

International Nuclear Information System (INIS)

[en] Investigation of two-phase heat trnsfer in horizontal pipe flow have led to a new generalized correlation for the heat transfer coefficient. The proposed correlation equation is NUTP=3.04 [Pe]0.8 [Bo]0.6 This correlation was tested againts the existing and experimental data obtained on two-pahse heat transfer covering the entire possible flow regimes in a horizontal pipe flow. The correlation produces satisfactory result. (authors). 13 refs, 12 tabs, 2 figs

1992-01-01

207

Time dependence of the 137Cs and 90Sr transfer coefficient in a Mediterranean ecosystem  

International Nuclear Information System (INIS)

The soil-plant transfer of 137Cs and 90Sr was studied in a low turnover rate Mediterranean ecosystem. The available activities of the two radionuclides in the soil and their stable chemical analogues, K and Ca, respectively, evolve periodically over time due to the marked dry and wet seasons existing in this type of climate. This seriously restricts the validity of using constant transfer and discrimination coefficients.

1996-01-01

208

Mass transfer coefficients for arranged packings with vertical walls under gas film control  

Energy Technology Data Exchange (ETDEWEB)

Packings with vertical walls, especially structured packings, are distinguished by their high efficiency and low pressure drop per mass transfer unit. Yet for these types of packings there is still no universal relationship for calculating gas-film-controlled mass transfer coefficients. The present work proposes such an equation. For arranged and structured packings the new equation fits the experimental data, both new results and those taken from the literature, with a mean error of 9%. (orig.)

Kolev, N. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Chemical Engineering; Nakov, S. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Chemical Engineering; Djonova-Atanassova, D. [Bulgarian Academy of Sciences, Sofia (Bulgaria). Inst. of Chemical Engineering

1995-12-01

209

A new method for determining coupled heat and mass transfer coefficients between air and liquid desiccant  

Energy Technology Data Exchange (ETDEWEB)

This paper presented the characteristic of liquid desiccant dehumidification based on NTU-Le model. The results showed that the Lewis number Le had little effect on air outlet humidity ratio during desiccant solution dehumidification process. A new method called h{sub D}-Le separative evaluation method was developed for determining coupled heat and mass transfer coefficients between air and liquid desiccant, through which the heat and mass transfer coefficients between air and liquid desiccant were calculated to obtain from experimental inlet and outlet parameters of air and desiccant solution. The effects of the air volume flow rate, temperature, humidity ratio and the solution concentration, temperature on the Lewis number, heat and mass transfer coefficient were analyzed according to experimental data and the h{sub D}-Le separative evaluation method. Based on the computation results, it was concluded that the Lewis number greatly depended on the operation parameters and conditions of the air and desiccant. In addition, the correlations of the heat and mass transfer coefficients were developed. The additional 74 groups of experiments validated the developed correlations by comparison of air/solution parameters change with the calculation data. (author)

Yin, Yonggao; Zhang, Xiaosong [School of Energy and Environment, Southeast University, Nanjing (China)

2008-07-01

210

Empirical correlation of volumetric mass transfer coefficient for a rectangular internal-loop airlift bioreactor  

Science.gov (United States)

An empirical correlation of volumetric mass transfer coefficient was developed for a pilot scale internal-loop rectangular airlift bioreactor that was designed for biotechnology. The empirical correlation combines classic turbulence theory, Kolmogorov’s isotropic turbulence theory with Higbie’s pen...

211

Effect of Mass on Convective Heat Transfer Coefficient During Onion Flakes Drying  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this present study an open sun and greenhouse drying of onion flakes has been performed to study the effect of mass on convective heat transfer coefficient. Three sets of experiments with total quantity of onion as 300, 600 and 900 g were done. The onion was continuously dried for 33 h both in op...

Anil Kumar; G.N. Tiwari

212

Coefficients of mass transfer in the Van der Waals modified model  

International Nuclear Information System (INIS)

A simple model of molecular components of mass transfer coefficients for a modified Van der Waals state equation is proposed. On the whole, the model calculation results agree with experimental data for different liquid and vapor metals. Estimations of liquid metal (Na, K, Rb, Cs, Mg, Pu) viscosity in the megabar pressure region are presented. 23 refs.; 8 figs.; 1 tab

1995-01-01

213

The ultrasonic-enhanced factor of mass-transfer coefficient in the supercritical carbon dioxide extraction  

Science.gov (United States)

Based on several hypotheses about the process of supercritical carbon dioxide extraction, the onflow around the solute granule is figured out by the Navier-Stocks equation. In combination with the Higbie’s solute infiltration model, the link between the mass-transfer coefficient and the velocity of flow is found. The mass-transfer coefficient with the ultrasonical effect is compared with that without the ultrasonical effect, and then a new parameter named the ultrasonic-enhanced factor of mass-transfer coefficient is brought forward, which describes the mathematical model of the supercritical carbon dioxide extraction process enhanced by ultrasonic. The model gives out the relationships among the ultrasonical power, the ultrasonical frequency, the radius of solute granule and the ultrasonic-enhanced factor of mass-transfer coefficient. The results calculated by this model fit well with the experimental data, including the extraction of Coix Lacryma-jobi Seed Oil (CLSO) and Coix Lacryma-jobi Seed Ester (CLSE) from coix seeds and the extraction of Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) from the alga by means of the ultrasonic-enhanced supercritical carbon dioxide extraction (USFE) and the supercritical carbon dioxide extraction (SFE) respectively. This proves the rationality of the ultrasonic-enhanced factor model. The model provides a theoretical basis for the application of ultrasonic-enhanced supercritical fluid extraction technique.

Luo, Benyi; Lu, Yigang

2008-10-01

214

On the heat transfer coefficient in nonstationary problems of heat exchange  

International Nuclear Information System (INIS)

[en] The solution of a conjugated nonstationary problem of heat exchange between a solid body and a liquid having constant temperature and moving at a constant rate is considered. Formulae for determination of rate and temperature fields as well as the nonstationary coefficient of heat transfer are obtained

1987-01-01

215

FLUID TO PARTICLE HEAT TRANSFER COEFFICIENTS IN HOLDING TUBE HAVING NONCIRCULAR CROSS SECTION  

Science.gov (United States)

Convective heat transfer coefficient (hp) between fluid and particle in continuous tube flow was compared for two configurations of holding tubes: one conventional having circular cross section (CHT) and the other having non-circular cross section (NCHT). A stream of plastic spheres was fed into the...

216

Measurements of pressure drop, heat transfer coefficient and critical energy of a bundle conductor  

International Nuclear Information System (INIS)

[en] Friction factor, saturation temperature, heat transfer coefficient and critical energy of an eight strand bundle conductor were measured in the test facility SULTAN at SIN in Switzerland. The measured values of the critical energy are in good agreement with those calculated by the computer code LONSA. 10 refs

1981-04-03

217

An experimental method to measure local heat transfer coefficient from a distance  

Science.gov (United States)

The present paper describes an experimental method to measure local heat flux from a distance. The method is based on the fact that when a wall is heated locally, the wall temperature rise depends on the local heat transfer coefficient at that point. In the experiment, the wall was heated by a power laser and the temperature rise was measured by an infrared spot thermometer. Transient heat conduction in a wall was numerically solved for a heated location. The integral of the temperature rise is found to be the quantity most sensitive to variation in heat transfer coefficient. If the integral value is measured within a 2 percent error margin, the heat transfer coefficient could be evaluated within a margin of 10 percent for acryl. For metals having high thermal diffusivity, however, error is above 80 percent. Automatical measurement with the aid of a personal computer made it possible to evaluate forced convection heat transfer coefficient of a flat plaster plate within an accuracy of 20 percent.

Fujii, Motoo; Mugabi, Nelson; Yoshikawa, Chouiku; Fujii, Tetsu

218

Effect of Hydrotropes on Solubility and Mass Transfer Coefficient of p-Nitrobenzoic Acid  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of various hydrotropes such as sodium benzoate, sodium salicylate and nicotinamide on the solubility and mass transfer coefficient of p-nitrobenzoic acid was investigated. The solubility studies were carried out under a wide range of hydrotrope concentrations 0 to 3.0 kmol m-3...

D. Gnana Prakash; S. Thenesh Kumar; N. Nagendra Gandhi

219

Mass transfer coefficients developed from the air gasification of wood pellets  

Energy Technology Data Exchange (ETDEWEB)

A convertible updraft/downdraft, fixed-bed gasifier was used in the gasification of 3/8-inch diameter wood pellets. The test data was used to develop mass transfer coefficients and describe the gasification process for each gasifier configuration. The results show that the production of the principal combustion gases, i.e., hydrogen (H{sub c}), carbon monozide (CO), and methane (CH{sub 4}), varies directly as to their mass transfer coefficient: H{sub 2}, CO, and CH{sub 4} = k h{sub DA}. Factoring the Reynolds (Re{sub d}) and Schmidt (Sc) numbers with the influence of the noncombustible gases, i.e., nitrogen (N{sub 2}), oxygen (O{sub 2}), and carbon dioxide (CO{sub 2}), is used to define the mass transfer coefficients. The general form describing this joint variation is: H{sub 2}, CO, and CH{sub 4} = kx (the effect of the noncombustible gases) x Re x Sc where Re = Reynolds number and Sc = Schmidt number. The developments of these mass transfer coefficients are shown for updraft and downdraft gasification.

Botts, J.W.

1998-07-01

220

A new experimental technology for measuring local heat transfer coefficients around the tube immersed in high temperature fluidized bed  

Energy Technology Data Exchange (ETDEWEB)

A new probe has been developed for measuring the local heat transfer coefficients between immersed tubes and high temperature fluidized bed. Operating temperatures extended up to 850{degree}C and the time-averaged local heat transfer coefficients around a single or central tube in an array were investigated. The variation of heat transfer coefficients and its peripheral distribution of the tube with superficial velocity and the pitch in arrays are described. 5 refs., 7 figs., 2 tabs.

Yang, J.; Wang, L.; Ni, X. [University of Science and Technology, Beijing (China)

1995-12-31

 
 
 
 
221

Evaluation of the heat transfer coefficient at the metal-mould interface during flow  

Directory of Open Access Journals (Sweden)

Full Text Available Calculation results concerning the heat transfer coefficient at the metal-mould interface during flow of the AlMg10 alloy in the channel-like cavity of the spiral castability test mould. The experimental cooling curve as well as changes of metal flow velocity have been determined on the basis of the measured metal temperature during flow. The cooling curve equation for the examined alloy, derived from the heat balance condition in a casting-mould system and taking into account experimental data concerning changes in metal temperature and its flow velocity, has enabled evaluation of the heat transfer coefficient at a chosen point of a metal stream along the mould channel. Graphic representations of changes of this coefficient against time and the channel length have been shown.

Z. Konopka; M. ??giewka; A. Zyska

2007-01-01

222

Experimental and predicted overall heat-transfer coefficients for four residential air-to-air heat exchangers  

Energy Technology Data Exchange (ETDEWEB)

Experimental values of the overall heat transfer coefficient are obtained from measured values of the effectiveness for four residental size air-to-air heat exchangers. Predictions of the overall heat transfer coefficient are made from available information, primarily analytical, that specifies the local heat transfer coefficients for the two air streams. For the range of flow rates involved in the experiments, typical of the use of these exchangers, the usual transition criteria imply that the flows are laminar. The correspondence between the experimental and the predicted values of the overall heat transfer coefficients is not very good. Comments are made about these discrepancies, but the differences cannot be definitely explained at present.

Seban, R.A.; Rostami, A.; Zarringhalam, M.

1981-12-01

223

Determination of intraparticulate mass transfer coefficients via permeation measurements: theory and experimental validation.  

UK PubMed Central (United Kingdom)

A mathematical model of mass transfer through a heterogeneous, multiphase barrier has been developed where the dispersed phase is capable of uptake of the diffusant according to a linear relationship. The model was used to describe the penetration of drugs through dispersions of permeable globules in media of known diffusional properties. Water-in-oil-in-water (W/O/W) multiple emulsions have been studied by this method. When used to analyze data obtained with a simple diffusion cell, the model allows the calculation of the mass transfer coefficient which characterizes the diffusional mass transfer across oil-water interfaces within the emulsions. The mass transfer coefficient is directly related to the drug release rate from the internal phases of multiple emulsions. Those cases where instantaneous equilibria are established or where impermeable globules are present can be treated as special limiting cases. Differential equations which express diffusant concentrations as functions of time, space, and dispersion system parameters have been solved by Laplace transformation without recourse to numerical methods. The values of the mass transfer coefficient are shown to reflect the physical characteristics of multiple emulsion systems.

Rippie EG; Liaw WC

1996-04-01

224

Soil plant transfer coefficient of 14C-carbofuran in brassica sp. vegetable agroecosystem  

International Nuclear Information System (INIS)

The soil plant transfer coefficient or f factor of 14C-carbofuran pesticide was studied in outdoor lysimeter experiment consisting of Brassica sp. vegetable crop, riverine alluvial clayey soil and Bungor series sandy loam soil. Soil transfer coefficients at 0-10 cm soil depth were 4.38 ± 0.30, 5.76 ± 1.04, 0.99 ± 0.25 and 2.66 ± 0.71; from IX recommended application rate in alluvial soil, 2X recommended application rate in alluvial soil, IX recommended application rate in Bungor soil and 2X recommended application rate in Bungor soil, respectively. At 0-25 cm soil depth, soil plant transfer coefficients were 8.96 ± 0.91, 10.40 ± 2.63, 2.34 ± 0.68 and 619 ±1.40, from IX recommended application rate in alluvial soil, 2X recommended application rate in alluvial soil, IX recommended application rate in Bungor soil and 2X recommended application rate in Bungor soil, respectively. At 77 days after treatment (DAT), the soil plant transfer coefficient was significantly higher in riverine alluvial soil than Bungor soil whereas shoot and root growth was significantly higher in Bungor soil than in riverine alluvial soil. At both 0-10 cm Brassica sp. rooting depth and 0-25 cm soil depth, the soil plant transfer coefficient was significantly higher in 2X recommended application rate of 14C-carbofuran as compared to IX recommended application rate, in both Bungor and riverine alluvial soils. (Author)

2006-01-01

225

Experimental determination of heat transfer coefficient in the slip regime and its anomalously low value.  

UK PubMed Central (United Kingdom)

In this paper, the measurement of the heat transfer coefficient in rarefied gases is presented; these are among the first heat transfer measurements in the slip flow regime. The experimental setup is validated by comparing friction factor in the slip regime and heat transfer coefficient in the continuum regime. Experimental results suggest that the Nusselt number is a function of Reynolds and Knudsen numbers in the slip flow regime. The measured values for Nusselt numbers are smaller than that predicted by theoretical or simulation results, and can become a few orders of magnitude smaller than the theoretical values in the continuum regime. The results are repeatable and expected to be useful for further experimentation and modeling of flow in the slip and transition regimes.

Demsis A; Verma B; Prabhu SV; Agrawal A

2009-07-01

226

Experimental determination of heat transfer coefficient in the slip regime and its anomalously low value.  

Science.gov (United States)

In this paper, the measurement of the heat transfer coefficient in rarefied gases is presented; these are among the first heat transfer measurements in the slip flow regime. The experimental setup is validated by comparing friction factor in the slip regime and heat transfer coefficient in the continuum regime. Experimental results suggest that the Nusselt number is a function of Reynolds and Knudsen numbers in the slip flow regime. The measured values for Nusselt numbers are smaller than that predicted by theoretical or simulation results, and can become a few orders of magnitude smaller than the theoretical values in the continuum regime. The results are repeatable and expected to be useful for further experimentation and modeling of flow in the slip and transition regimes. PMID:19658810

Demsis, Anwar; Verma, Bhaskar; Prabhu, S V; Agrawal, Amit

2009-07-22

227

Experimental determination of heat transfer coefficient in natural convection within a inclined channel  

International Nuclear Information System (INIS)

[en] An experimental test to study natural convection heat transfer to air within a trapezoidal channel area was carried out, heating one of its faces. The temperature in different points along the heated face, inlet and outlet air temperature, environment temperature, the current and voltage supplied to the heater were measured. From the measures, the power applied and the average heat transfer coefficient in the channel were determined. During the experimental test the power applied, channel inclination and the air entrance and exit position, were changed. The values obtained from the different test modes show that the heat transfer coefficient is independent of the power and strongly dependent of the channel inclination and channel position. (author)

1999-01-01

228

[Preliminary study on characteristics of volumetric oxygen transfer coefficient in granular sludge systems].  

UK PubMed Central (United Kingdom)

The volumetric oxygen transfer coefficient (k(L)a) was tested with mature aerobic granules in the same aeration measurement device and under the same aeration conditions. The k(L)a (min(-1)) was 0.586 1 +/- 0.009 5, 0.586 1 +/- 0.0272, 0.555 6 +/- 0.016 8, 0.5338 +/- 0.0268 for floc sludge, and 0.645 5 +/- 0.027 6, 0.632 0 +/- 0.0755, 0.618 5 +/- 0.062 5, 0.640 6 +/- 0.055 5 for aerobic granules, when the sludge concentration MLSS (mg x L(-1)) was controlled at 2 000, 4 000, 6 000, 8 000, respectively. This indicated that granular sludge exhibited higher k(L)a values than the flocs, and the k(L)a value of floc sludge decreased with the increase of the sludge concentration; however, insignificant decease was found for granular sludge. After screening of granules with different diameter, the k(L)a values of the aerobic granular sludge with different sizes which had the same MLSS, volume, surface area and particle number were compared, and insignificant difference was found, suggesting that the effects of these factors on the k(L)a of granular sludge were negligible. The findings of this work may have significance for the energy-saving operation of wastewater treatment plants.

Li ZH; Fan CQ; Wang XC

2013-06-01

229

Heat transfer to falling water film on a vertical surface  

International Nuclear Information System (INIS)

An experimental study was performed on the heat transfer to a turbulent water film which is falling down the outside surface of a heated vertical tube. The test section was made of stainless steel tube 13 mm in outside diameter and 1,500 mm long. It was found that a nearly constant heat transfer coefficient was obtained for the lower half of the test section covering a length of about 1 m, which was direct-heated by electric current. The resulting values of the Nusselt number in this region were correlated to the Reynolds number, and the plots fell in a region intermediate between those given by Wilke and by McAdams. An analytical model taking account of the undulation on the film surface is proposed. The predictions from the model give fairly good agreement with the experimental data. (auth.)

1975-01-01

230

Consolidation of heat transfer coefficients of viscoelastic simulated food solutions in helical exchangers  

UK PubMed Central (United Kingdom)

Heat transfer of viscoelastic liquids in helical exchangers attracted limited work in the past. Most heat transfer equations proposed do not reduce to the Graetz–Leveque equation for the straight tubes. Heat transfer coefficients were obtained for seven copper helical coil heat exchangers with different diameters and diameter ratios. Hot water was used as the heating medium; and dilute polyacrylamide solutions were used to simulate the food solutions. Results showed increased heat transfer coefficients but the magnitudes were lower than those obtained by previous workers. A unified form of the Graetz–Leveque equation obtained was: Nu=1.75 Gz¹/³[1+0.5421Dn?.??(d/D)?.??] for water. The heat transfer equation for the 250ppm solution is represented by, Nu=1.75 Gz¹/³[1+0.3515Dn?.??(d/D)?.??]; and for the 500ppm solution the results can be represented by Nu=1.75 Gz¹/³[1+0.3615Dn?.??(d/D)?.??]. Viscoelasticity reduces heat transfer performance.

Ismail Z; Karim R

2012-01-01

231

Study for transfer coefficient of iodine from grass to cow milk  

International Nuclear Information System (INIS)

Radioiodine (131I) is one of the radio nuclides likely to get released into the atmosphere in case of a reactor accident, though chances of such an accident are very remote due to stringent engineering safety features. During the short initial phase of accidental release of radioactivity, 131I is transferred through grass-cow milk pathway, leading to significant thyroid dose to those consuming milk, especially infant and children. Transfer coefficients are important for quick evaluation of environmental contamination, during both normal and abnormal operational phases of a nuclear facility. Transfer coefficient of iodine from grass to milk is defined as ratio of iodine concentration in milk (Bq.L-1) obtained at equilibrium for a constant rate of intake of iodine in (Bq.D-1). During normal operation conditions of nuclear power reactor, the release of radioactive iodine isotopes is are too low that they are not present in measurable concentrations in the environment. Hence, studies are to be performed using stable iodine to estimate the transfer coefficient. A method has been developed based on thermal neutron activation analysis (NAA) to estimate the stable iodine concentration present in grass and cow milk. The method involves pre-concentration from matrix, neutron activation and gamma spectrometry and these were standardized

2012-01-01

232

Finite difference method for computer study of the interfacial heat transfer coefficient during rapid solidification of spherical samples on a metallic substrate  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper a numerical model will be adopted to analyze the heat transfer process during rapid solidification of a spherical sample placed on a metallic substrate cooled by water. The interfacial heat transfer coefficient between the sample and the substrate will be evaluated by matching model calculations with the surface temperature history recorded by a digital camera during solidification of a sample melted in an Arc-image furnace. .

Nikoli? Z.S.; Yoshimura M.; Araki S.; Fujiwara T.

2007-01-01

233

Enhanced convective and film boiling heat transfer by surface gas injection  

Energy Technology Data Exchange (ETDEWEB)

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

234

Enhanced convective and film boiling heat transfer by surface gas injection  

Energy Technology Data Exchange (ETDEWEB)

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

235

Comparison of interfacial heat transfer coefficient estimated by two different techniques during solidification of cylindrical aluminum alloy casting  

Energy Technology Data Exchange (ETDEWEB)

The interfacial heat transfer coefficient (IHTC) is necessary for accurate simulation of the casting process. In this study, a cylindrical geometry is selected for the determination of the IHTC between aluminum alloy casting and the surrounding sand mold. The mold surface heat flux and temperature are estimated by two inverse heat conduction techniques, namely Beck's algorithm and control volume technique. The instantaneous cast and mold temperatures are measured experimentally and these values are used in the theoretical investigations. In the control volume technique, partial differential heat conduction equation is reduced to ordinary differential equations in time, which are then solved sequentially. In Beck's method, solution algorithm is developed under the function specification method to solve the inverse heat conduction equations. The IHTC was determined from the surface heat flux and the mold surface temperature by both the techniques and the results are compared. (orig.)

Rajaraman, R. [Anna University, B. S. Abdur Rahman Crescent Engineering College, Chennai (India); Velraj, R. [Anna University, College of Engineering Guindy, Chennai (India)

2008-07-15

236

Theoretical Prediction of Volumetric Mass Transfer Coefficient (kLa) for Designing an Aeration Tank  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this present paper is to propose a new theoretical prediction method of the volumetric mass transfer coefficient (kLa) occurring in a gas-liquid contactor based on the dissociation of the liquid-side mass transfer coefficient (kL) and th...

Pisut Painmanakul; Jidapa Wachirasak; Marupatch Jamnongwong; Gilles Hebrard

237

Development of a new correlation for estimating pool boiling heat transfer coefficient of MEG/DEG/water ternary mixture  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Pool boiling heat transfer coefficient of monoethylene glycol (MEG), diethylene glycol (DEG) and water ternary mixtures has been experimentally measured up to heat flux 114 kW/m2 at various volumetric concentrations of MEG and DEG. As expected, heat transfer coefficient was strongly taken as a d...

Sarafraz M.M.; Alavi-Fazel S.A.; Hasanzadeh Y.; Arabshamsabadi A.; Bahram S.

238

Transient Heat Diffusion with Temperature-Dependent Conductivity and Time-Dependent Heat Transfer Coefficient  

Directory of Open Access Journals (Sweden)

Full Text Available Lie point symmetry analysis is performed for an unsteady nonlinear heat diffusion problem modeling thermal energy storage in a medium with a temperature-dependent power law thermal conductivity and subjected to a convective heat transfer to the surrounding environment at the boundary through a variable heat transfer coefficient. Large symmetry groups are admitted even for special choices of the constants appearing in the governing equation. We construct one-dimensional optimal systems for the admitted Lie algebras. Following symmetry reductions, we construct invariant solutions.

Raseelo J. Moitsheki

2008-01-01

239

Heat transfer coefficient in water-sodium shell-and-tube steam generators  

International Nuclear Information System (INIS)

[en] This paper is related to heat transfer in a shell-and-tube steam generator and provides a comparison between experimental data and results obtained by a simple theoretical model deduced by empirical correlations. The experimental work was carried out in a 50 MW steam generatorprototype for a nuclear fast breeder ractor. Several correlations for the heat transfer coefficients are considered for the preheater (single phase) and the region of subcooled, nucleate, post dry-out boiling (two phase flow). Several temperature distributions are obtained and the configuration best in agreement with the experimental data and the pertinent correlations are emphasized

1985-01-01

240

Developments in geothermal energy in Mexico. Pt. 9. Heat transfer equation for determining convection coefficients in liquid-solid fluidised beds  

Energy Technology Data Exchange (ETDEWEB)

The use of liquid fluidised bed heat exchangers (LFBE) as a promising method of physically eliminating scaling of heat transfer surfaces due to geothermal fluids is described. The methodology employed by other researchers for the development of a heat transfer design equation to predict bed-side convection coefficients is analysed. It appears that such a methodology is inappropriate. An analytical mathematical method for determining the constants in the design equation to predict fluidisation-related convection coefficients is developed and proposed for the analysis of pertinent experimental data. Preliminary results employing the method are included and a complete analysis is underway.

Garcia, A.; Siqueiros, J.; Heard, C.; Barragan, D.; Hinojosa, A.

1986-01-01

 
 
 
 
241

Heat transfer coefficient between the flame and a radioactive material transport cask  

International Nuclear Information System (INIS)

[en] At the time of a full-scale fire experiment on a fire-resisting wooden building, a model radioactive material transport cask was placed within the flame of the fire. By measuring its temperatures and temperatures of the fire flame, the heat transfer coefficient etc. were observed. The specimen model cask is a three-layered structure; the outer steel shell, the inner stainless steel shell and a lead radiation shielding layer in between. (1) When the flame started to surround the cask, the heat flux from the flame into the cask was about 7 x 104 kcal/m2h, in agreement with that measured with a heat flow meter. (2) The total heat transfer coefficient from the flame into the cask, calculated from the temperature measurements in both, was about 150 - 200 kcal/m2h0C. (Mori, K.)

1984-01-01

242

Experimental Estimation of Heat Transfer Coefficients Using Helical Coil in an Agitated Vessel  

Directory of Open Access Journals (Sweden)

Full Text Available A mathematical model is developed to analyze the heating rates and compare the relation with experimental results obtained in our present study . Low shear rate concentration of sodium carboxymethal cellulose fluids with two different coil lengths 2.362m and 2.82m, diameter of the helical coil equal to 156mm, di=4.0mm and do=6.4mm were used to correlate overall heat transfer coefficients in an agitated vessel with four blade paddle impeller. The model is derived by using velocity flow field and energy equations in cylindrical coordinate for straight tube and later extended to helical coil. The new design relation for obtaining the individual heat transfer coefficient in terms of flow behavior index is equal to

Ashok Reddy K , Bhavanth Rao M ,Ram Reddy P

2012-01-01

243

Effect of Hydrotropes on Solubility and Mass Transfer Coefficient of p-Nitrobenzoic Acid  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of various hydrotropes such as sodium benzoate, sodium salicylate and nicotinamide on the solubility and mass transfer coefficient of p-nitrobenzoic acid was investigated. The solubility studies were carried out under a wide range of hydrotrope concentrations 0 to 3.0 kmol m-3 and different system temperatures (303-333 K). It has been observed that the solubility and mass transfer coefficient of p-nitrobenzoic acid increases with increase in hydrotorpe concentration and also with system temperature. The maximum enhancement factor, which is the ratio of the value in the presence and absence of a hydrotrope, has been determined for all sets of experimentations. The effectiveness of hydrotropes was measured in terms of Setschenow constant Ks and reported for all hydrotropes used in this study.

D. Gnana Prakash; S. Thenesh Kumar; N. Nagendra Gandhi

2009-01-01

244

Condensation heat transfer to the free surface of a turbulent film flow  

International Nuclear Information System (INIS)

Condensation heat transfer of steam to the free surface of a developing turbulent film flow was investigated experimentally in an inclined rectangular channel. The heat transfer coefficients at the free surface were approximately three times higher than those at a solid wall calculated by Dittus and Boelter's Nusselt number and McAdams' correction factor for developing turbulent channel flow. Also, the turbulent transport and diffusive characteristics near the free surface were examined by numerical analysis using the k-? model of turbulence for low Reynolds number flow and three different turbulence models near the free surface. The model, whose calculated heat transfer coefficient agrees best with the experimental results, is that having the identical surface boundary conditions of k and ? at the free surface with those at a solid wall. (author)

1986-01-01

245

Determination of heat transfer coefficient between a fluid and a wall  

International Nuclear Information System (INIS)

[en] The authors show the extent to which one can assume the existence of a constant heat transfer coefficient between a fluid and a wall in transient thermal conditions, and the means of estimating it. After reviewing investigations reported in the literature (coefficient assumed constant or not), they present two models based on a pulse method: sudden increase in wall temperature, cooling by fluid flow, temperature recording of the wall face not in contact with the fluid-wether or not the fluid is heated. They present the experimental system, define the tranfer coefficient, and make the calculation from the thermogram obtained. For water and air, they analyze the variations in coefficient as a function of fluid flow rate, initial pulse, temperature detector position, and show that the method proposed yields reproducible results[fr] Les auteurs mesurent un coefficient d'echange de chaleur constant entre un fluide et une paroi en regime thermique transitoire et comment l'evaluer. Puis apres avoir rappele les etudes presentees dans la litterature (coefficient suppose constant ou non), ils presentent deux modeles bases sur une methode impulsionnelle: augmentation brusque de la temperature de paroi, refroidissement par ecoulement de fluide, enregistrement de la temperature de la face de paroi non soumise au fluide - que le fluide s'echauffe ou non -. Ils presentent le dispositif experimental, definissent le coefficient d'echange et en font le calcul a partir du thermogramme obtenu. Pour l'eau et l'air, ils etudient les variations du coefficient en fonction du debit de fluide, de l'impulsion initiale, de la position des detecteurs de temperature et montrent que la methode proposee donnent des resultats reproductibles

1981-01-01

246

A look-up table for film-boiling heat-transfer coefficients in tubes with vertical upward flow  

International Nuclear Information System (INIS)

A look-up table of film-boiling heat-transfer coefficients has been developed for steam-water flow inside vertical tubes, using a methodology similar to that for the look-up table of critical heat flux. The film-boiling look-up table provides heat-transfer coefficients at discrete values of pressure, mass flux, heat flux and thermodynamic quality, covering both the inverted annular-flow film-boiling (IAFB) and the dispersed-flow film-boiling (DFFB) regions. The table values are established using 14 687 film-boiling heat-transfer data points for tubes compiled in the AECL film-boiling data bank. At conditions where no data are available, these values are calculated using the Groeneveld-Delorme correlation (for the DFFB region) and the Hammouda model (for the IAFB region). The film-boiling look-up table and other leading film-boiling prediction methods have been assessed using the available data base. The look-up table predicts the surface-temperature data with a root-mean-square error of 6.73% and an average error of 1.2%, which is an improvement over that of other prediction methods. In addition, the film-boiling look-up table covers a wide range of flow conditions, provides a smooth transition between IAFB and DFFB regions, requires little computing time, and exhibits correct asymptotic and parametric trends. (author)

1997-10-04

247

Whole-body heat transfer coefficient and body temperature change of juvenile Pacific bluefin tuna Thunnus orientalis according to growth  

UK PubMed Central (United Kingdom)

Bluefin tuna maintain a higher body temperature than ambient sea water. Body heat is derived mainly from metabolic heat to elevate and maintain regional body temperature that is higher than the ambient, while heat loss is caused by heat transfer throughout the whole body surface and gills. Retention of high body temperature is thought to differ at each growth stage, so that a larger body mass maintains a higher body temperature. We evaluated the whole-body heat transfer coefficient, thermal difference between each tissue and water temperature, and metabolic heat in tissues during swimming of juvenile bluefin tuna as a function of fork length (FL) using a small thermometer and a treadmill-type flow tank. A system for maintaining high body temperature was well developed in fish with FL greater than 20.0 cm. Whole-body heat transfer coefficient was fitted to a - 0.695 power of mass. Juvenile bluefin tuna showed a transition speed of 3.0 FL/s at which they switched from aerobic to anaerobic motion.

KUBO Toshihiko; SAKAMOTO Wataru; MURATA Osamu; KUMAI Hidemi

2008-10-01

248

The effects of surface roughness on the heat transfer at the metal-mold interface  

Energy Technology Data Exchange (ETDEWEB)

Heat transfer coefficient values at the metal-mold interface are an important parameter in the production of sound quality castings. This investigation focused primarily on the effect of surface roughness on heat transfer coefficient values. The paper will describe the development of a versatile apparatus. This apparatus was instrumented with thermocouples, displacement sensors-LVDT (Linear Variable Differential Transformer) and an electrical contact detection circuit. The equipment facilitated the recording of the temperature profile in chill and casting, as well as the detection and measurement of movement at the metal-mold interface including mold expansion and air-gap detection and measurement. Experiments were carried out by casting various aluminum alloys against different chill materials, each of various surface roughness. Inverse heat transfer analysis was used to estimate the heat transfer coefficient at the metal mold interface. This estimation revealed how the heat transfer coefficient changes during the metal solidification. Generally, an increase in surface roughness results in a decrease in the heat transfer coefficient at the metal mold interface. (author)

Coates, B.L.; Argyropoulos, S.A.; Melissari, B. [Univ. of Toronto, Dept. of Material Science and Engineering, Toronto, Ontario (Canada)]. E-mail: b.coates@utoronto.ca; agryro@ecf.utoronto.ca; blas.melissari@utoronto.ca

2002-07-01

249

Local heat transfer coefficients during the evaporation of 1,1,1,2-tetrafluoroethane (R-134a) in a plate heat exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available The evaporation heat transfer coefficient of the refrigerant R-134a in a vertical plate heat exchanger was investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, the local value of the heat transfer coefficient was calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux, heat flux, pressure of system and the flow configuration on the heat transfer coefficient were also taken into account and a comparison with literature data was performed.

EMILA ŽIVKOVI?; STEPHAN KABELAC; SLOBODAN ŠERBANOVI?

2009-01-01

250

Evaluation of heat transfer coefficient of tungsten filaments at low pressures and high temperatures  

International Nuclear Information System (INIS)

[en] The paper presents an experimental method for the evaluation of the heat transfer coefficient of tungsten filaments at low pressures and high temperatures. For this purpose an electrode of a T5 fluorescent lamp was tested under low pressures with simultaneous heating in order to simulate the starting conditions in the lamp. It was placed in a sealed vessel in which the pressure was varied from 1 kM (kilo micron) to 760 kM. The voltage applied to the electrode was in the order of the filament's voltage of the lamp at the normal operation with the ballast during the preheating process. The operating frequency ranged from DC to 50 kHz. The experiment targeted on estimating the temperature of the electrode at the end of the first and the ninth second after initiating the heating process. Next, the heat transfer coefficient was calculated at the specific experimental conditions. A mathematical model based on the results was developed that estimates the heat transfer coefficient. The experiments under different pressures confirm that the filament's temperature strongly depends on the pressure.

2011-01-01

251

Heat transfer coefficient, two-phase flow boiling of HFC134a  

International Nuclear Information System (INIS)

[en] Evaporation of HFC134a inside smooth, horizontal tubes is studied. Tests are made with pure refrigerant and with oil-refrigerant mixtures. Heat flux has varied from 2 kW/m2 to 10 kW/m2. The inner diameter of the tubes are 12 mm. Two evaporators are used, 4 and 10 m long. Oil content is varied from 0 to 2.5 mass percentage (synthetic oil, EXP-0275). Oil free HFC134a is found to have higher heat transfer coefficient than HCF22 at the same heat flux, as well as mass flux. The effect of oil in the refrigerant depends on the flux. At 2 and 4 kW/m2, the heat transfer coefficient has a maximum value for an oil content of around 0.5 mass percentage. No increase at all is registered for a heat flux of 6 kW/m2. Heat transfer coefficients for pure refrigerant are also compared to existing correlations. Pierre's correlation predict values with a reasonable accuracy

1990-01-01

252

Determination of local heat transfer coefficient from the solution of the inverse heat conduction problem  

Energy Technology Data Exchange (ETDEWEB)

The aim of this paper is to present two techniques for simply and accurately determining space-variable heat transfer coefficient, given measurements of temperature at some interior points in the body. The fluid temperature is also measured as part of the solution. The methods are formulated as linear and non-linear least-squares problems. The unknown parameters associated with the solution of the inverse heat conduction problem (IHCP) are selected to achieve the closest agreement in a least squares sense between the computed and measured temperatures using the Levenberg-Marquardt method (method I) or the singular value decomposition (method II). The methods presented in the paper are used for determining the local heat transfer coefficient on the circumference of the vertical smooth tube placed in the tube bundle with a staggered tube arrangement. Good agreement between the results is obtained. The uncertainties in the estimated heat transfer coefficients are calculated using the error propagation rule of Gauss. The main advantage of the presented methods is that they do not require any complex simulation of flow and temperature field in the fluid. (orig.)

Taler, J. [Cracow Univ. of Tech. (Poland). Inst. of Process and Power Engineering

2007-06-15

253

Measurement of condensation heat transfer coefficients in a steam chamber using a variable conductance heat pipe  

International Nuclear Information System (INIS)

Condensation heat transfer coefficients have been measured in a pressurised chamber containing a mixture of saturated steam and air. They were determined as a function of the air-steam ratio in nominally stagnant conditions. The effect of pressure is assessed and preliminary measurements with a forced convective component of velocity are presented. A novel measurement technique was adopted, namely to use a vertical heat pipe whose conductance could easily be varied. It transported heat from an evaporator located inside the chamber to a condenser section outside, at which the heat flow was measured. Heat flux at the evaporator could then be determined and a condensation heat transfer coefficient derived. The range of coefficients covered was from 150 W/m2 0K at high air-steam ratios to 20,000 W/m2 0K in pure steam. Results show that increasing either total pressure or velocity enhances condensation heat transfer over the range of air/steam ratios considered. (author)

1988-01-01

254

Effect of Mass on Convective Heat Transfer Coefficient During Onion Flakes Drying  

Directory of Open Access Journals (Sweden)

Full Text Available In this present study an open sun and greenhouse drying of onion flakes has been performed to study the effect of mass on convective heat transfer coefficient. Three sets of experiments with total quantity of onion as 300, 600 and 900 g were done. The onion was continuously dried for 33 h both in open sun and in the roof type even span greenhouse with floor area of 1.2 x 0.78 m2. Experiments were carried out during the months of October to December 2003 at IIT Delhi (28°35`N 72°12`E). Experiments were started at 8 am. The data obtained from experimentation under open sun and greenhouse conditions have been used to determine values of the constant `C` and exponent `n` by regression analysis and consequently, convective heat transfer coefficient. It is observed that there is a significant effect of mass on convective heat transfer coefficient for open as well as greenhouse drying. It is also observed that the rate of moisture evaporation in case of greenhouse drying is more than that in open sun drying during the off sunshine hours due to the stored energy inside the greenhouse. The experimental observations were analyzed in terms of percentage uncertainty also.

Anil Kumar; G.N. Tiwari

2006-01-01

255

MM98.34 Experimental Measurements of Die temperatures and determination of heat transfer coefficient in backward can extrusion  

DEFF Research Database (Denmark)

The large deformations in backward can extrusion result in a rise of temperature of more than 200 degrees Centigrade. In the experiments cans in low carbon steel are formed, with a lubrication layer of phosphate soap. The temperature is measured by thermocouples in the die insert and the punch. The die insert is divided into two halves where the thermocouples are welded to the end of milled grooves in the lower part. The temperature of the workpiece is measured by welding a thermocouple directly onto the free surface.The punch is equipped with three thermocouples mounted at a distance of 0.2 mm from the surface. The thermocouples are welded to the end of grooves milled in a small plug, Which is pressed into a hold in the punch nose. All the temperature measurements in the tool and the workpiece are compared with a number of FEM simulations computed with different heat transfer coefficients. The current heat transfer coefficient is determined as the one resulting in the best agreement between measurements and the simulations.

Henningsen, Poul; Hattel, Jesper Henri

1998-01-01

256

MM98.43 Experimental determination of the heat transfer coefficient Under dynamic process conditions in backward can extrusion  

DEFF Research Database (Denmark)

The large deformations in backward can extrusion result in a rise of temperature of more than 200 oC. In the experiments, cans in low carbon steel are formed with a lubrication layer of phosphate soap. The temperature is measured by thermocouples in the die insert and the punch. The die insert is divided into two halves where the thermocouples are welded to the end of milled grooves in the lower part. The temperature of the workpiece is measured by welding a thermocouple directly onto the free surface. The punch is equipped with three thermocouples mounted at a distance of 0.2 mm from the surface. The thermocouples are welded to the end of grooves milled in a small plug, which is pressed into a hold in the punch nose. All the temperature measurements in the tool and the workpiece are compared with a number of finite element (FE) simulations computed with different heat transfer coefficients. The current heat transfer coefficient (HTC) is then determined by the least square method

Henningsen, Poul; Hattel, Jesper Henri

1998-01-01

257

Thermal Accommodation Coefficient of Helium and Argon on an Amorphous SiO sub 2 Surface.  

Science.gov (United States)

The thermal accommodation coefficient was determined for the interaction of two inert gases, helium and argon, on a surface composed of thermally grown amorphous silicon dioxide. The surface was processed as an integrated circuit chip and utilized compone...

A. McFall

1980-01-01

258

Comparison of boiling heat transfer coefficient and pressure drop correlations for evaporators  

International Nuclear Information System (INIS)

[en] Evaporator design is an important aspect for the HVAC industry. As the demand for more efficient and compact heat exchangers increase, researches on estimation of two-phase flow heat transfer and pressure drop gain importance. Due to complexity of the hydrodynamic and heat transfer of the two-phase flow, there are many experimental studies available for refrigerants int he literature. In this study, a model for boiling heat transfer in a horizontal tube has been developed and the simulation results are compared with experimental ones published in the literature. In these comparisons, heat transfer coefficient is calculated by using Kattan-Thome-Favrat (1998), Shah (1982), Kandilikar (1990), Chaddock and Brunemann (1967) correlations under different operational conditions such as saturation pressure, mass flux, the type of refrigerant and two phase flow pattern. Besides that flow pattern has also been considered in the simulation by using Thome and El Hajal (2002) model. For pressure drop Lockhart-Martinelli (1949), Mueller-Steinhagen-Hack (1986) and Groennerund (1979) correlations are used in simulations. Local vapor quality change at each experimental condition through the model is determined. Roughness is an important parameter for frictional pressure drop. Friction coefficient is determined by using Churchill (1977) model. (author)

2009-01-01

259

Evaluation of Heat and Mass Transfer Coefficients for R134a/DMF Bubble Absorber  

Directory of Open Access Journals (Sweden)

Full Text Available The Vapour Absorption Refrigeration System (VARS) has generated renewed interest and is being viewed as one of the alternatives for vapour compression refrigeration due to its potential for waste heat utilization. To improve the efficiency of these systems, it is necessary to study heat and mass transfer processes in absorption system components. The absorber, one of the crucial components in VARS is considered for study. Experimental investigation is carried out to study heat and mass transfer characteristics in a glass absorber. A new combination of R134a/DMF is used as the working fluid to overcome the limitations of well known working pairs, ammonia-water and lithium bromide-water. The effects of parameters viz., gas flow rate, solution initial concentration, solution pressure and solution temperature on absorber performance are analyzed. Heat and mass transfer coefficients evaluated from the experiments are compared with the numerical model and it is found that agreement is good. Heat and mass transfer coefficients increase as the gas flow rate, solution initial concentration and solution temperature increase whereas they decrease as the solution pressure increases. Sherwood number and Nusselt number evaluated from the experimental data are compared with those obtained from the numerical correlations developed earlier by the authors.

M. Suresh; A. Mani

2011-01-01

260

Evaluation of condensation heat transfer coefficient in AC600 passive containment cooling system  

International Nuclear Information System (INIS)

[en] The author gives a warranty to choice condensation heat transfer correlation (HTC) in AC600 passive containment cooling system (PCCS) analysis by comparing some most useful condensation HTC used in PCCSAC-MD code which is a multi-dimensional thermal-hydraulic analysis code for AC600 PCCS. These correlations include Uchida correlation, Gido-Koestl correlation, Tagami correlation and heat-mass transfer analogy correlation using the heat transfer coefficient on the vapor side of the interface. The author gets the conclusion that the Uchida correlation based on steady state data of experiment is more conservative than the Gido-Koestl correlation. The difference of peak pressure value of AC600 containment under double ended cold leg loss of coolant accident or main steam line break accident calculated by different correlation is similar while for double ended hot leg loss of coolant accident the difference is big, Although different correlation gets different heat transfer coefficient. The Tagami correlation is the most conservative one in the main steam line break accident calculated

1999-01-01

 
 
 
 
261

Theoretical Prediction of Volumetric Mass Transfer Coefficient (kLa) for Designing an Aeration Tank  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this present paper is to propose a new theoretical prediction method of the volumetric mass transfer coefficient (kLa) occurring in a gas-liquid contactor based on the dissociation of the liquid-side mass transfer coefficient (kL) and the interfacial area (a). The calculated results have been compared with those obtained with the experimental process in a small-scale bubble column. Tap water was used as liquid phase and an elastic membrane with a single orifice as gas sparger. Only the dynamic bubble regime was considered in this work (ReOR= 1501000 and We = 0.0024). This study has clearly shown that, whatever the operating conditions under test, the generated bubble diameters (dB), bubble frequency (fB) and their associated rising velocities (UB) were the important parameters in order to predict, not only the values of kLa, but also the values of a and of kL. Moreover, these obtained results could provide a better understanding of the parameters which influence the oxygen transfer mechanism in the aeration process. By using the correlations to estimate these bubble hydrodynamics (dB and UB), it diminishes times for measuring the associated mass transfer parameters and also their experimental complexities and errors.

Pisut Painmanakul; Jidapa Wachirasak; Marupatch Jamnongwong; Gilles Hebrard

2009-01-01

262

Experimental study on condensation heat transfer of steam on vertical titanium plates with different surface energies  

Energy Technology Data Exchange (ETDEWEB)

Visual experiments were employed to investigate heat transfer characteristics of steam on vertical titanium plates with/without surface modifications for different surface energies. Stable dropwise condensation and filmwise condensation were achieved on two surface modification titanium plates, respectively. Dropwise and rivulet filmwise co-existing condensation form of steam was observed on unmodified titanium surfaces. With increase in the surface subcooling, the ratio of area ({eta}) covered by drops decreased and departure diameter of droplets increased, resulting in a decrease in condensation heat transfer coefficient. Condensation heat transfer coefficient decreased sharply with the values of {eta} decreasing when the fraction of the surface area covered by drops was greater than that covered by rivulets. Otherwise, the value of {eta} had little effect on the heat transfer performance. Based on the experimental phenomena observed, the heat flux through the surface was proposed to express as the sum of the heat flux through the dropwise region and rivulet filmwise region. The heat flux through the whole surface was the weighted mean value of the two regions mentioned above. The model presented explains the gradual change of heat transfer coefficient for transition condensation with the ratio of area covered by drops. The simulation results agreed well with the present experimental data when the subcooling temperature is lower than 10 C. (author)

Baojin, Qi; Li, Zhang; Hong, Xu; Yan, Sun [State-Key Laboratory of Chemical Engineering, School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237 (China)

2011-01-15

263

FREG-4: a computer program to predict the fuel-to-cladding heat transfer coefficient in accordance with the fuel-rod irradiation history  

International Nuclear Information System (INIS)

Program FREG series calculate temperature distribution in a fuel rod and the stored energy based on the distribution. The temperature distribution is calculated accordance with the fuel rod irradiation history. The temperature in the fuel rod is severely influenced with gap heat transfer coefficients between fuel pellet surface and cladding inner surface. Enphasis is placed on how to find the gap heat transfer coefficients. FREG-4 is a version-up program of FREG-3. Major modification from FREG-3 is handlings of fission product gas release, which have influences on the gap heat transfer. FREG-4 distingushed fission-product isotopes remained in pellets and fission-product gaseous isotopes released from the pellets, and considers that the released isotopes are transported for plenums to balance whole fuel rod internal pressure and transformed into another isotopes due to decay and the nuetron absorptions. The present report describes modified models from FREG-3 and user's manual for FREG-4. (author)

1981-01-01

264

Hydrodynamic characteristics and overall volumetric oxygen transfer coefficient of a new multi-environment bioreactor.  

UK PubMed Central (United Kingdom)

The hydrodynamic characteristics and the overall volumetric oxygen transfer coefficient of a new multi-environment bioreactor which is an integrated part of a wastewater treatment system, called BioCAST, were studied. This bioreactor contains several zones with different environmental conditions including aerobic, microaerophilic and anoxic, designed to increase the contaminant removal capacity of the treatment system. The multi-environment bioreactor is designed based on the concept of airlift reactors where liquid is circulated through the zones with different environmental conditions. The presence of openings between the aerobic zone and the adjacent oxygen-depleted microaerophilic zone changes the hydrodynamic properties of this bioreactor compared to the conventional airlift designs. The impact of operating and process parameters, notably the hydraulic retention time (HRT) and superficial gas velocity (U(G)), on the hydrodynamics and mass transfer characteristics of the system was examined. The results showed that liquid circulation velocity (V(L)), gas holdup (?) and overall volumetric oxygen transfer coefficient (k(L)a(L)) increase with the increase of superficial gas velocity (U(G)), while the mean circulation time (t(c)) decreases with the increase of superficial gas velocity. The mean circulation time between the aerobic zone (riser) and microaerophilic zone (downcomer) is a stronger function of the superficial gas velocity for the smaller openings (1/2 in.) between the two zones, while for the larger opening (1 in.) the mean circulation time is almost independent of U(G) for U(G) ? 0.023 m/s. The smaller openings between the two zones provide higher mass transfer coefficient and better zone generation which will contribute to improved performance of the system during treatment operations.

Behzadian F; Yerushalmi L; Alimahmoodi M; Mulligan CN

2013-08-01

265

Hydrodynamic characteristics and overall volumetric oxygen transfer coefficient of a new multi-environment bioreactor.  

Science.gov (United States)

The hydrodynamic characteristics and the overall volumetric oxygen transfer coefficient of a new multi-environment bioreactor which is an integrated part of a wastewater treatment system, called BioCAST, were studied. This bioreactor contains several zones with different environmental conditions including aerobic, microaerophilic and anoxic, designed to increase the contaminant removal capacity of the treatment system. The multi-environment bioreactor is designed based on the concept of airlift reactors where liquid is circulated through the zones with different environmental conditions. The presence of openings between the aerobic zone and the adjacent oxygen-depleted microaerophilic zone changes the hydrodynamic properties of this bioreactor compared to the conventional airlift designs. The impact of operating and process parameters, notably the hydraulic retention time (HRT) and superficial gas velocity (U(G)), on the hydrodynamics and mass transfer characteristics of the system was examined. The results showed that liquid circulation velocity (V(L)), gas holdup (?) and overall volumetric oxygen transfer coefficient (k(L)a(L)) increase with the increase of superficial gas velocity (U(G)), while the mean circulation time (t(c)) decreases with the increase of superficial gas velocity. The mean circulation time between the aerobic zone (riser) and microaerophilic zone (downcomer) is a stronger function of the superficial gas velocity for the smaller openings (1/2 in.) between the two zones, while for the larger opening (1 in.) the mean circulation time is almost independent of U(G) for U(G) ? 0.023 m/s. The smaller openings between the two zones provide higher mass transfer coefficient and better zone generation which will contribute to improved performance of the system during treatment operations. PMID:23142846

Behzadian, Farnaz; Yerushalmi, Laleh; Alimahmoodi, Mahmood; Mulligan, Catherine N

2012-11-10

266

Mass transfer in SCW extraction molecular diffusion and mass transfer coefficients of ketones and alkenes in sub- and supercritical water  

Energy Technology Data Exchange (ETDEWEB)

The potential of sub- and supercritical water as extraction solvents has been demonstrated for the (reactive) extraction of coals, used car tires, organic species from residual aqueous solutions, and class selective extraction of organic pollutants with different polarities from solids. In addition, the potential of extraction of coal with supercritical aqueous solutions has been studied. However, physical transport in water at elevated temperature and pressures- and their impact on heterogenous reactions and (reactive) extraction -are not adequately understood. This situation is largely due to the limited data that is available for diffusion in high temperature, high pressure water mixture. Only the molecular diffusion of Iodine ions and hydroquinone in near-critical subcritical water and the self diffusion of coefficient of compressed supercritical water have been reported. In this paper, we present molecular diffusion coefficients of benzophenone, acetone, naphthalene, and anthracene in water at infinite dilution. Pressures ranged from 250 to 500 bar at temperatures ranging from 50{degrees}C to 500{degrees}C resulting in water densities ranging from 1000 to 150 kg/m{sup 3}. Diffusion coefficients were determined by the Taylor-Aris dispersion technique. The effects of increased diffusion on the mass transfer coefficients for emulsions and packed beds were quantified. Molecular division coefficients were 10 to 20 times faster in supercritical water than in water at ambient conditions. Experimental results were correlated with hydrodynamic and kinetic theory. This study and results to be published elsewhere show that diffusion-limited conditions are much more likely to be encountered in supercritical water than is commonly acknowledged.

Goemans, M.G.E.; Gloyna, E.F. [Univ. of Texas, Austin, TN (United States)] [and others

1996-10-01

267

Effect of blade tip geometry on heat transfer coefficients on gas turbine blade tips and near tip regions  

International Nuclear Information System (INIS)

Detailed heat transfer coefficient distributions on two types of gas turbine blade tip, plane tip and squealer tip, were measured using a hue-detection base transient liquid crystals technique. The heat transfer coefficients on the shroud and near tip regions of the pressure and suction sides of the blade were also measured. The heat transfer measurements were taken at the three different tip gap clearances of 1.0%, 1.5%, and 2.5% of blade span. Results show the overall heat transfer coefficients on the tip and shroud with squealer tip blade were lower than those with plane tip blade. By using squealer tip, however, the reductions of heat transfer coefficients near the tip regions of the pressure and suction sides were not remarkable

2006-01-01

268

An experimental study on evaporative heat transfer coefficient and applications for passive cooling of AP600 steel containment  

International Nuclear Information System (INIS)

[en] After TMI and Chernobyl accidents, many efforts have been made to enhance the nuclear safety with passive features. Among such passive features, the passive containment cooling system (PCCS) has been suggested by Westinghouse in the AP600 plant. The containment with PCCS is a dual containment, and consists of a stainless steel vessel and a concrete wall. In the gap between these structures, air and water can counter-currently pass and cool the steel surface. This paper experimentally investigates evaporative heat and mass transfer at the surface of a falling water film with counter-current air flow in a vertical duct with one-side heated plate. Experiments included various conditions of mass flow rate of film and air. Experimental results show the strong effects of water temperature and air mass flow rate, but little effect of the water flow rate. Also, simple analyses based on heat and mass transfer analogy were performed to evaluate the experimental results. With experimental data, a new correlation on evaporative mass transfer coefficient was developed, and with the correlation, the containment pressure and temperature was calculated for the design basis accident of AP600 by the use of CONTEMPT4/MOD5 code implementation

2001-01-01

269

Effect of pressure on heat transfer coefficient at the metal/mold interface of A356 aluminum alloy  

DEFF Research Database (Denmark)

The aim of this paper is to correlate interfacial heat transfer coefficient (IHTC) to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of casting under different pressures were obtained using the inverse heat conduction problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented for correlation between external pressure and heat transfer coefficient. Acceptable agreement with data in literature shows the accuracy of the proposed formula.

Fardi Ilkhchy, A.; Jabbari, Masoud

2012-01-01

270

Immersion Condensation on Oil-Infused Heterogeneous Surfaces for Enhanced Heat Transfer  

Science.gov (United States)

Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil. The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles. Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases. This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer.

Xiao, Rong; Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N.

2013-06-01

271

Immersion condensation on oil-infused heterogeneous surfaces for enhanced heat transfer.  

UK PubMed Central (United Kingdom)

Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil. The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles. Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases. This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer.

Xiao R; Miljkovic N; Enright R; Wang EN

2013-01-01

272

Immersion Condensation on Oil-Infused Heterogeneous Surfaces for Enhanced Heat Transfer  

Science.gov (United States)

Enhancing condensation heat transfer is important for broad applications from power generation to water harvesting systems. Significant efforts have focused on easy removal of the condensate, yet the other desired properties of low contact angles and high nucleation densities for high heat transfer performance have been typically neglected. In this work, we demonstrate immersion condensation on oil-infused micro and nanostructured surfaces with heterogeneous coatings, where water droplets nucleate immersed within the oil. The combination of surface energy heterogeneity, reduced oil-water interfacial energy, and surface structuring enabled drastically increased nucleation densities while maintaining easy condensate removal and low contact angles. Accordingly, on oil-infused heterogeneous nanostructured copper oxide surfaces, we demonstrated approximately 100% increase in heat transfer coefficient compared to state-of-the-art dropwise condensation surfaces in the presence of non-condensable gases. This work offers a distinct approach utilizing surface chemistry and structuring together with liquid-infusion for enhanced condensation heat transfer.

Xiao, Rong; Miljkovic, Nenad; Enright, Ryan; Wang, Evelyn N.

2013-01-01

273

Correlations for heat transfer coefficients in open gaps with respect to mixed convection  

International Nuclear Information System (INIS)

Published results on mixed convection phenomena have been applied to determine the convective heat transfer between the cover gas and the open gaps in the roof of SNR 2. It has been reported in the literature that heat transfer coefficients for forced flow conditions in vertical heated or cooled pipes are modified by buoyancy effects. In the ''aiding'' condition, where buoyancy and flow act in the same direction, heat transfer is enhanced. In the ''opposing'' case heat transfer is reduced. This applies for laminar flow; the reverse is true for turbulent flow. The literature indicates furthermore that: the Reynolds number indicating turbulent flow can be as low as 30 for mixed convection; the criterion for the onset of mixed convection is given by the Richardson number Ri=Gr/Re2 > 0,002. The published results have been modified in consistency with the open gaps in the SNR 2 reactor roof. Several heat transfer correlations have been evaluated and their suitability examined. (author)

1986-01-01

274

Dialyzer clearances and mass transfer-area coefficients for small solutes at low dialysate flow rates.  

Science.gov (United States)

New daily hemodialysis therapies operate at low dialysate flow rates to minimize dialysate volume requirements; however, the dependence of dialyzer clearances and mass transfer-area coefficients for small solutes on dialysate flow rate under these conditions have not been studied extensively. We evaluated in vitro dialyzer clearances for urea and creatinine at dialysate flow rates of 40, 80, 120, 160, and 200 ml/min and ultrafiltration flow rates of 0, 1, and 2 l/h, using a dialyzer containing PUREMA membranes (NxStage Medical, Lawrence, MA). Clearances were measured directly across the dialyzer by perfusing bovine blood with added urea and creatinine single pass through the dialyzer at a nominal blood flow rate of 400 ml/min. Limited, additional studies were performed with the use of dialyzers containing PUREMA membranes at a blood flow rate of 200 ml/min and also with the use of other dialyzers containing polysulfone membranes (Optiflux 160NR, FMC-NA, Ogden, UT) and dialyzers containing Synphan membranes (NxStage Medical). For dialyzers containing PUREMA membranes, urea and creatinine clearances increased (p < 0.001) with increasing dialysate and ultrafiltration flow rates but were not different at blood flow rates of 200 and 400 ml/min. Dialysate saturation, defined as dialysate outlet concentration divided by blood water inlet concentration, for urea and creatinine was independent of blood and ultrafiltration flow rate but varied inversely (p < 0.001) with dialysate flow rate. Mass transfer-area coefficients for urea and creatinine were independent of blood and ultrafiltration flow rate but decreased (p < 0.001) with decreasing dialysate flow rate. Calculated mass transfer-area coefficients at low dialysate flow rates for all dialyzers tested were substantially lower than those reported by the manufacturers under conventional conditions. We conclude that dialyzers require specific characterization under relevant conditions if they are used in novel daily hemodialysis therapies at low dialysate flow rate. PMID:16883120

Leypoldt, John K; Kamerath, Craig D; Gilson, Janice F; Friederichs, Goetz

275

Dialyzer clearances and mass transfer-area coefficients for small solutes at low dialysate flow rates.  

UK PubMed Central (United Kingdom)

New daily hemodialysis therapies operate at low dialysate flow rates to minimize dialysate volume requirements; however, the dependence of dialyzer clearances and mass transfer-area coefficients for small solutes on dialysate flow rate under these conditions have not been studied extensively. We evaluated in vitro dialyzer clearances for urea and creatinine at dialysate flow rates of 40, 80, 120, 160, and 200 ml/min and ultrafiltration flow rates of 0, 1, and 2 l/h, using a dialyzer containing PUREMA membranes (NxStage Medical, Lawrence, MA). Clearances were measured directly across the dialyzer by perfusing bovine blood with added urea and creatinine single pass through the dialyzer at a nominal blood flow rate of 400 ml/min. Limited, additional studies were performed with the use of dialyzers containing PUREMA membranes at a blood flow rate of 200 ml/min and also with the use of other dialyzers containing polysulfone membranes (Optiflux 160NR, FMC-NA, Ogden, UT) and dialyzers containing Synphan membranes (NxStage Medical). For dialyzers containing PUREMA membranes, urea and creatinine clearances increased (p < 0.001) with increasing dialysate and ultrafiltration flow rates but were not different at blood flow rates of 200 and 400 ml/min. Dialysate saturation, defined as dialysate outlet concentration divided by blood water inlet concentration, for urea and creatinine was independent of blood and ultrafiltration flow rate but varied inversely (p < 0.001) with dialysate flow rate. Mass transfer-area coefficients for urea and creatinine were independent of blood and ultrafiltration flow rate but decreased (p < 0.001) with decreasing dialysate flow rate. Calculated mass transfer-area coefficients at low dialysate flow rates for all dialyzers tested were substantially lower than those reported by the manufacturers under conventional conditions. We conclude that dialyzers require specific characterization under relevant conditions if they are used in novel daily hemodialysis therapies at low dialysate flow rate.

Leypoldt JK; Kamerath CD; Gilson JF; Friederichs G

2006-07-01

276

Novel, flat plate solar collector, electronic, heat transfer coefficient, digital meter design  

Energy Technology Data Exchange (ETDEWEB)

The design and the theory of the flat-plate collector heat transfer coefficient is presented using a nonlinear analogue to digital converter (NL-ADC). Two voltages, V/sub 1/ and V/sub 2/, proportional to two temperatures T/sub 1/ and T/sub 2/, respectively, are applied to an NL-ADC which produces a digital number proportional to (T/sub 1//sup 4/ - T/sub 2//sup 4/)/(T/sub 1/ - T/sub 2/) or, electronically, (V/sub 1//sup 4/ - V/sub 2//sup 4/)/(V/sub 1/ -V/sub 2/).

Al-Chalabi, B.B.; Abdul-Karim, M.A.H.

1986-01-01

277

Experimental measurement of the water-to-cover heat transfer coefficient inside shallow solar stills  

Energy Technology Data Exchange (ETDEWEB)

The purpose of this work is to measure the overall heat transfer coefficient from water to cover in shallow solar stills using yield measurements. The geometry under analysis represents a real solar still operating with laboratory-controlled temperatures and induced heat flows in steady-state. Temperature differences between the water and the glass cover varied from 2 to 16 K, and water temperature from 298 to 353K, corresponding to the range of heat flows from 0 to 650 W m{sup -2}, in accordance with the operation of a solar still in ambient conditions. (author)

Porta-Gandara, M.A.; Rubio, E. [Centro de Investigaciones Biologicas del Noroeste, La Paz (Mexico); Fernandez, J.L. [Universidad Nacional Autonoma de Mexico (Mexico). Inst. de Ingenieria

1998-01-01

278

Assessment of Real Heat Transfer Coefficients through Shell and Tube and Plate Heat Exchangers  

Directory of Open Access Journals (Sweden)

Full Text Available The purpose of this paper is to present a procedure used in the assessment of the real heat transfer characteristic of shell and tube and plate heat exchangers. The theoretical fundamentals of the procedure are introduced as well as the measured data collection and processing. The theoretical analysis is focused on the adoption of criterial equations which, subjected to certain verification criteria presented in the paper, provide the most credible value of the convection heat transfer coefficients inside the circular and flat tubes. In the end two case studies are presented, one concerning a shell and tube heat exchanger operational at INCERC Thermal Substation and the other concerning a plate heat exchanger tested on the Laboratory Stand of the Department of Building Services and Efficient Use of Energy in Buildings of INCERC Bucharest.

Dan CONSTANTINESCU; Horia PETRAN

2011-01-01

279

The role of surface energy coefficients and nuclear surface diffuseness in the fusion of heavy-ions  

CERN Multimedia

We discuss the effect of surface energy coefficients as well as nuclear surface diffuseness in the proximity potential and ultimately in the fusion of heavy-ions. Here we employ different versions of surface energy coefficients. Our analysis reveals that these technical parameters can influence the fusion barriers by significant amount. A best set of these parameters is also given that explains the experimental data nicely.

Dutt, Ishwar

2010-01-01

280

CONVECTIVE HEAT TRANSFER COEFFICIENT OF INDIAN GOOSEBERRY (EMBLICA OFFICINALIS) DRIED IN THREE DIFFERENT FORMS UNDER FORCED CONVECTION MODE  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, convective heat transfer coefficient of Indian gooseberry (Emblica officinalis), in three different forms (shreds, slices and pieces), under forced convection mode has been determined. These forms were dried in laboratory drier. Values of constants C and n have been determined using experimental data and regression analysis for calculating values of convective heat transfer coefficient. It was found that the convective heat transfer coefficient varies with form of commodity being dried and decreases as the drying progresses. The value of convective heat transfer coefficient was highest for shredded form (30.39 W/m2oC) followed by slices (25.88 W/m2oC) and pieces (18.67 W/m2oC) when compared at certain final moisture content. The data were also analyzed for per cent uncertainty.

S. I. ANWAR; R.D. SINGH

2012-01-01

 
 
 
 
281

Analysis of the transverse heat transfer coefficients in a dual channel ITER-type cable-in-conduit conductor  

CERN Document Server

This paper describes a new method to determine the equivalent heat transfer coefficients, i.e., radial and azimuthal, in CICC’s with parallel cooling channels. The method is based on the measurement of the steady state temperature response to a step heating. The experiment is modelled by a set of transport equations for the temperature distribution that contain explicitly the parametric dependence on the transverse heat transfer coefficients. The equations are solved analytically and the values of the equivalent transverse heat transfer coefficients are obtained as the best fit of the experimental temperature distributions. We show the results obtained with the method by application to a short length sample experiment in the SULTAN test facility using an ITER-type CICC with special instrumentation, and with heaters to generate a variety of heat slugs. The values of heat transfer coefficient are consistent with expected values, based in particular on the theory of dispersion in porous media.

Marinucci, C; Bruzzone, P; Stepanov, B

2007-01-01

282

Dependence of the heat transfer coefficient on the vibration amplitude and frequency of a verical thin heater  

International Nuclear Information System (INIS)

[en] The effect of mechanical vibrations of a heated string on the heat transfer coefficient ? at various heat fluxes has been studied experimentally. An empirical relation between the coefficient ? and the vibration frequency and amplitude with unchanged q has been found

1995-01-01

283

Convective heat transfer coefficient studies in upward and downward, vertical, two-phase, non-boiling flows  

International Nuclear Information System (INIS)

[en] An experimental study was conducted to determine the two-phase heat transfer coefficient in an air-water, non-boiling vertical system. Enhancement of the heat transfer coefficient in this two-phase flow system was observed in both upward and downward flow directions. The correlation of void fraction profile and water velocity profile in bubbly flow was discussed and its influence on heat transfer behavior was examined. An explanation for the heat transfer mechanism in slug flow was postulated from the observed hydrodynamic phenomenon. Correlations based on the Sieder-Tate type equation was established to collapse, within /plus or minus/15%, the experimentally determined two-phase heat transfer coefficient utilizing a two-phase Reynolds number based on a liquid phase Reynolds number corrected for liquid holdup. 24 refs

1980-01-01

284

Effect of Hydrotropes on Solubility and Mass Transfer Coefficient of Methyl Benzoate  

Directory of Open Access Journals (Sweden)

Full Text Available Normal 0 7.8 ? 0 2 false false false EN-US ZH-CN X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:????; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} A comprehensive investigation on the solubility and mass transfer coefficient enhancement of methyl benzoate through hydrotropy has been undertaken. The solubility and mass transfer coefficient studies were carried out using hydrotropes such as citric acid, urea and nicotinamide under a wide range of hydrotrope concentrations (0 to 3.0 mol/L) and different system temperatures (303 to 333 K). The effectiveness of hydrotropes was measured in terms of Setschnew constant Ks and reported for all hydrotropes used in this study.

Senthil Nathan; M. Jayakumar C.; N Nagendra Gandhi

2009-01-01

285

An instrument to measure the convective heat transfer coefficient on large vessels.  

Science.gov (United States)

Hepatocellular carcinoma is one of the most common malignancies worldwide. During radiofrequency hepatic ablation, the tumor is heated by means of radiofrequency energy. The heating causes necrosis of the malignant tumor. Thus, if the procedure is successful it can cure the patient. Studies have shown that recurrences occur after the treatment and these recurrences frequently take place next to the hepatic artery and portal vein. The recurrences occur due to the high convective loss on these vessels. This work proposed, developed and tested an instrument for the measurement of the convective heat transfer coefficient (h) in large vessels. Moreover, this work developed a mechanical simulator and validated an equation developed by Consiglieri et al, which analytically determines the value of h. The instrument was tested using a mechanical simulator that reproduces the flow conditions and the geometry of large vessels in the liver. A flow velocity of 0.2 m/s was simulated in order to mock the typical flow at the portal vein. The average value of h using the experimental apparatus was 2130+/-40 W.m(-2).K(-1) (mean+/-SD). The results showed that the error of the proposed method is approximately 22%. This work showed that the instrument can be used for measuring h in vitro and that the Consiglieri's equation can be used to determine the convective heat transfer coefficient on large vessels. PMID:19162607

Miguel, Alaor Faria; de O Nascimento, Francisco Assis; da Rocha, Adson Ferreira; dos Santos, Icaro

2008-01-01

286

Transfer coefficient of 137Cs from feed to cow milk in tropical region Kaiga (India)  

International Nuclear Information System (INIS)

In the transport model for the prediction of the concentration of 137Cs in milk, the transfer coefficient from feed to milk, Fm, is an important parameter. Site-specific transfer coefficient from feed to cow's milk, for 137Cs in the Kaiga environment, a nuclear power station site in India, determined over a period of 10 y is presented in this paper. The value is determined from 137Cs concentration in milk and grass samples of the Kaiga region and the result ranged from 6.43 E-03 to 1.09 E-02 d l-1 with a geometric mean value of 8.0 E-03 d l-1. The result is compared with that for 40K, determined concurrently at the same region and ranged from 3.06 E-03 to 3.48 E-03 d l-1 with a geometric mean value of 3.26 E-03 d l-1. This parameter is quite useful in decision-making for implementing countermeasures during a large area contamination with 137Cs in tropical areas like Kaiga. (authors)

2012-01-01

287

A correlation for free convection heat transfer from vertical wavy surfaces  

Energy Technology Data Exchange (ETDEWEB)

Free convection heat transfer along an isothermal vertical wavy surface was studied experimentally and numerically. A Mach-Zehnder Interferometer was used in the experiment to determine the local heat transfer coefficients. Experiments were done for three different amplitude-wavelength ratios of {alpha} = 0.05, 0.1, 0.2 and the Rayleigh numbers ranging from Ra{sub l} = 2.9 x 10 {sup 5} to 5.8 x 10 {sup 5}. A finite-volume based code was developed to verify the experimental study and obtain the results for all the amplitude-wavelength ratios between {alpha} = 0 to 0.2. It is found that the numerical results agree well with the experimental data. Results indicate that the frequency of the local heat transfer rate is the same as that of the wavy surface. The average heat transfer coefficient decreases as the amplitude-wavelength ratio increases and there is a significant difference between the average heat transfer coefficients of the surface with {alpha} = 0.2 and those surfaces with {alpha} = 0.05 and 0.1. The experimental data are correlated with a single equation which gives the local Nusselt number along the wavy surface as a function of the amplitude-wavelength ratio and the Rayleigh number. (orig.)

Ashjaee, M.; Amiri, M.; Rostami, J. [University of Tehran, Department of Mechanical Engineering, Tehran (Iran)

2007-11-15

288

Single-Particle Diffusion-Coefficient on Surfaces with Ehrlich-Schwoebel-Barriers  

CERN Multimedia

The diffusion coefficient of single particles in the presence of Ehrlich-Schwoebel barriers (ESB)is considered. An exact expression is given for the diffusion coefficient on linear chains with random arrangements of ESB. The results are extended to surfaces having ESB with uniform extension in one or both directions. All results are verified by Monte Carlo simulations.

Mussawisade, K; Kehr, K W

1997-01-01

289

Measurement and modelling of forced convective heat transfer coefficient and pressure drop of Al2O3- and SiO2-water nanofluids  

Science.gov (United States)

Forced convective heat transfer coefficient and pressure drop of SiO2- and Al2O3-water nanofluids were characterized. The experimental facility was composed of thermal-hydraulic loop with a tank with an immersed heater, a centrifugal pump, a bypass with a globe valve, an electromagnetic flow-meter, a 18 kW in-line pre-heater, a test section with band heaters, a differential pressure transducer and a heat exchanger. The test section consists of a 1000 mm long aluminium pipe with an inner diameter of 31.2 mm. Eighteen band heaters were placed all along the test section in order to provide a uniform heat flux. Heat transfer coefficient was calculated measuring fluid temperature using immersed thermocouples (Pt100) placed at both ends of the test section and surface thermocouples in 10 axial locations along the test section (Pt1000). The measurements have been performed for different nanoparticles (Al2O3 and SiO2 with primary size of 11 nm and 12 nm, respectively), volume concentrations (1% v., 5% v.), and flow rates (3 103Re<105). Maximum heat transfer coefficient enhancement (300%) and pressure drop penalty (1000%) is obtained with 5% v. SiO2 nanofluid. Existing correlations can predict, at least in a first approximation, the heat transfer coefficient and pressure drop of nanofluids if thermal conductivity, viscosity and specific heat were properly modelled.

Julia, J. E.; Hernández, L.; Martínez-Cuenca, R.; Hibiki, T.; Mondragón, R.; Segarra, C.; Jarque, J. C.

2012-11-01

290

Measurement and modelling of forced convective heat transfer coefficient and pressure drop of Al2O3- and SiO2-water nanofluids  

International Nuclear Information System (INIS)

[en] Forced convective heat transfer coefficient and pressure drop of SiO2- and Al2O3-water nanofluids were characterized. The experimental facility was composed of thermal-hydraulic loop with a tank with an immersed heater, a centrifugal pump, a bypass with a globe valve, an electromagnetic flow-meter, a 18 kW in-line pre-heater, a test section with band heaters, a differential pressure transducer and a heat exchanger. The test section consists of a 1000 mm long aluminium pipe with an inner diameter of 31.2 mm. Eighteen band heaters were placed all along the test section in order to provide a uniform heat flux. Heat transfer coefficient was calculated measuring fluid temperature using immersed thermocouples (Pt100) placed at both ends of the test section and surface thermocouples in 10 axial locations along the test section (Pt1000). The measurements have been performed for different nanoparticles (Al2O3 and SiO2 with primary size of 11 nm and 12 nm, respectively), volume concentrations (1% v., 5% v.), and flow rates (3 103Re5). Maximum heat transfer coefficient enhancement (300%) and pressure drop penalty (1000%) is obtained with 5% v. SiO2 nanofluid. Existing correlations can predict, at least in a first approximation, the heat transfer coefficient and pressure drop of nanofluids if thermal conductivity, viscosity and specific heat were properly modelled.

2012-11-26

291

Mass transfer of SCWO processes: Molecular diffusion and mass transfer coefficients of inorganic nitrate species in sub- and supercritical water  

Energy Technology Data Exchange (ETDEWEB)

Molecular diffusion coefficients of lithium-, sodium-, potassium-, cesium-, calcium-, and strontium nitrate in subcritical water were determined by analysis of Taylor dispersion profiles. Pressures ranged from 300 to 500 bar at temperatures ranging from 25{degrees}C to 300{degrees}C. The reported diffusion values were determined at infinite dilution. Molecular diffusion coefficients were 10 to 20 times faster in near-critical subcritical water than in water at ambient temperature and pressure (ATP). These findings implied that the diffusion rates were more liquid like than they were gas like, hence experimental results were correlated with diffusion models for liquids. The subcritical diffusion data presented in this work, and supercritical diffusion results published elsewhere were correlated with hydrodynamic diffusion equations. Both the Wilke-Chang correlation and the Stokes-Einstein equation yielded predictions within 10% of the experimental results if the structure of the diffusing species could be estimated. The effect of the increased diffusion rates on mass transfer rates in supercritical water oxidation applications was quantified, with emphasis on heterogeneous oxidation processes. This study and results published elsewhere showed that diffusion limited conditions are much more likely to be encountered in SCWO processes than commonly acknowledged.

Goemans, M.G.E.; Gloyna, E.F. [Univ. of Texas, Austin, TX (United States). Dept. of Civil Engineering; Buelow, S.J. [Los Alamos National Lab., NM (United States)

1996-04-01

292

Thermocouple error correction for measuring the flame temperature with determination of emissivity and heat transfer coefficient  

Science.gov (United States)

Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%-40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively.

Hindasageri, V.; Vedula, R. P.; Prabhu, S. V.

2013-02-01

293

Thermocouple error correction for measuring the flame temperature with determination of emissivity and heat transfer coefficient.  

UK PubMed Central (United Kingdom)

Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%-40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively.

Hindasageri V; Vedula RP; Prabhu SV

2013-02-01

294

Thermocouple error correction for measuring the flame temperature with determination of emissivity and heat transfer coefficient.  

Science.gov (United States)

Temperature measurement by thermocouples is prone to errors due to conduction and radiation losses and therefore has to be corrected for precise measurement. The temperature dependent emissivity of the thermocouple wires is measured by the use of thermal infrared camera. The measured emissivities are found to be 20%-40% lower than the theoretical values predicted from theory of electromagnetism. A transient technique is employed for finding the heat transfer coefficients for the lead wire and the bead of the thermocouple. This method does not require the data of thermal properties and velocity of the burnt gases. The heat transfer coefficients obtained from the present method have an average deviation of 20% from the available heat transfer correlations in literature for non-reacting convective flow over cylinders and spheres. The parametric study of thermocouple error using the numerical code confirmed the existence of a minimum wire length beyond which the conduction loss is a constant minimal. Temperature of premixed methane-air flames stabilised on 16 mm diameter tube burner is measured by three B-type thermocouples of wire diameters: 0.15 mm, 0.30 mm, and 0.60 mm. The measurements are made at three distances from the burner tip (thermocouple tip to burner tip/burner diameter = 2, 4, and 6) at an equivalence ratio of 1 for the tube Reynolds number varying from 1000 to 2200. These measured flame temperatures are corrected by the present numerical procedure, the multi-element method, and the extrapolation method. The flame temperatures estimated by the two-element method and extrapolation method deviate from numerical results within 2.5% and 4%, respectively. PMID:23464237

Hindasageri, V; Vedula, R P; Prabhu, S V

2013-02-01

295

Analysis of Radome Using Aperture Integration-surface Integration Method with Modified Transmission Coefficient  

Science.gov (United States)

In this paper, the antenna-radome system in millimeter wave band is analyzed by the aperture integration-surface integration (AI-SI) method. When the electromagnetic wave passes through the radome, the transmission coefficient is determined by the transmission line analogy. However, the conventional transmission coefficient always ignores the phase factor of the lateral transmission in the dielectric. In the present work, the modified transmission coefficient is proposed and verified by both the theoretical derivation and the experimental measurement. The measured results of the antenna-radome systems at W-band show that the modified transmission coefficient is more accurate than the conventional one in the antenna-radome analysis.

Meng, Hongfu; Dou, Wenbin; Chen, Tiantian; Yin, Kai

2009-02-01

296

Heat transfer during cooling of hot surfaces by water nozzles  

Directory of Open Access Journals (Sweden)

Full Text Available Method of cooling in a secondary zone of continuous casting of steel has a significant influence on a quality of continuously cast products mainly from the point of view of internal and surface defects as well as zonal segregations. At the department of thermal engineering, a physical model of the secondary zone has been developed, which enables testing of both water and water-air nozzles. During laboratory measurements cooling effects of a cone nozzle have been expressed by means of three parameters. Most commonly used parameter is an admission characteristic, infrequently heat transfer coefficient is determined and newly a measuring of dynamic impact of the cooling water has been introduced.

M. Pøíhoda; J. Molínek; R. Pyszko; M. Veli?ka; M. Vaculík; J. Burda

2009-01-01

297

Application of a Fuzzy Neural Network for Modeling of the Mass-Transfer Coefficient in a Stirred Tank Bioreactor  

Directory of Open Access Journals (Sweden)

Full Text Available A type of a fuzzy neural network for mathematical modeling of the volumetric mass-transfer coefficient is presented in the paper. Performed investigations show that the presented fuzzy neural network can be successfully used for modeling of such a complex process, like mass-transfer.

Mitko Petrov; Tatiana Ilkova; Stoyan Tzonkov; Uldis Viesturs

2005-01-01

298

Application of a Fuzzy Neural Network for Modeling of the Mass-Transfer Coefficient in a Stirred Tank Bioreactor  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A type of a fuzzy neural network for mathematical modeling of the volumetric mass-transfer coefficient is presented in the paper. Performed investigations show that the presented fuzzy neural network can be successfully used for modeling of such a complex process, like mass-transfer.

Mitko Petrov; Tatiana Ilkova; Stoyan Tzonkov; Uldis Viesturs

299

[Interrelationship of the mass transfer coefficient with regard to O2 and CO2 in the process of antibiotic biosynthesis  

UK PubMed Central (United Kingdom)

A complex of studies on the effect of technological parameters on the mass transfer coeficients with respect to O2 and CO2 was carried out. It was shown that the ratio between the mass transfer coefficients with respect to O2 and CO2 was constant and equal to 20 for the fermentation broths of the antibiotic-producing organisms studied.

Sherstobitova TS; Bylinkina ES

1977-08-01

300

A methodology to assess transient contact heat transfer coefficient using contact boiling test data  

International Nuclear Information System (INIS)

[en] One of the passive safety features present in CANDU reactors is the heavy-water moderator surrounding the fuel channels. During some postulated loss-of-coolant accidents (LOCAs), pressure tubes (PTs) will deform radially into contact with associated calandria tubes (CTs). The contacted tubes form a radial heat removal path that is additional to the heat removal capability of the heat transport system. The stored heat and the decay heat from the fuel channel are transferred through the CT to the moderator, which acts as a heat sink. To demonstrate the effectiveness of the moderator as a heat sink and to ensure the integrity of the fuel channel, the transient contact heat transfer coefficient (CHTC) between the PT and CT after PT/CT contact is needed for safety analysis. Since the early 1980s, several series of experiments have been conducted at AECL Whiteshell Laboratories to assess contact boiling heat transfer that occurs when a pressurized PT deforms through a CO2 annulus gas gap into contact with a CT in a tank of heated water. Such contact boiling tests, in which full-scale PT and CT sections were used, provide sufficient data (i.e., test section temperatures, applied heater power and internal pressure) to infer the transient PT/CT CHTC based on the principles of heat transfer. A methodology has been developed to assess the transient PT/CT CHTC. The simulation model implements a negative feedback method by comparing contact boiling test data with the corresponding transient simulation results. The effectiveness and applicability of such a CHTC simulation model has been demonstrated with several test cases. The results show that the model has the capability to capture CHTC transient characteristics from the input data including the rapid changes in PT and CT temperatures upon initial contact and associated rapid changes in contact heat transfer coefficients. The PT/CT CHTC is an important parameter for determining fuel channel behaviour, which changes significantly during the course of a LOCA. With the methodology developed here the PT/CT CHTC transient can be determined using contact boiling test data to meet the needs of safety analysis. (author)

2002-01-01

 
 
 
 
301

Determination of the heat transfer coefficient and thermal conductivity for coconut kernels using an inverse method with a developed hemispherical shell model  

UK PubMed Central (United Kingdom)

Simulation studies for improved efficiency of thermal food processes (dryers) require knowledge of the heat transfer coefficient and thermal conductivity of the food. A novel analytical solution to the heat transfer problem in a hemispherical shell has been developed using the shifted Legendre functions. This was fitted to experimental data to determine the heat transfer coefficient and thermal conductivity of coconut by an inverse method. To minimize errors the natural shape of the food was taken into account. Neither the values nor the solution have been reported to-date. The values of heat transfer coefficients (h) and thermal conductivities (k) were found to be 17?h2?36, 4.0?h2? ?11 and 7.0?h1?15, 1.2?h1??3.0W/m2°C for the outer and inner surfaces, and 0.125?k?0.127 and 0.030?k??0.020W/m°C, respectively. The maximum temperature occurred at the outer equatorial surface and the minimum at the middle near to the pole. In the future these thermal parameters can be used to develop coconut dryers with improved energy efficiency and the method can be used to determine parameters for foods of similar shape.

Ramsaroop R; Persad P

2012-05-01

302

Effect of surface roughness on heat transfer from horizontal immersed tubes in a fluidized bed  

International Nuclear Information System (INIS)

[en] Experimental results of the total heat transfer coefficient between 12.7 mm dia copper tubes with four different rough surfaces and glass beads of three different sizes as taken in a 0.305 m x 0.305 m square fluidized bed as a function of fluidizing velocity are reported. The comparison of results for the rough and technically smooth tubes suggests that the heat transfer coefficient strongly depends on the ratio of pitch (P/sub f/) to the average particle diameter (d/sub p/), where P/sub f/ is the distance between the two corresponding points on consecutive threads or knurls. By the proper choice of (P/sub f//d/sub p/) ratio, the maximum total heat transfer coefficient for V-thread tubes (h/sub w/fb) can be increased by as much as 40 percent over the value for a smooth tube with the same outside diameter. However, for values of (P/sub f//d/sub p/) less than 0.95, the maximum heat transfer coefficient for the V-thread rough tubes is smaller than the smooth tube having the same outside diameter. The qualitative variation of the heat transfer coefficient for rough tubes with (P/sub f//d) is explained on the basis of the combined effect of contact geometry between the solid particles and the heat transfer surface, and the solids renewal rate at the surface. The present findings are critically compared with somewhat similar investigations from the literature on the heat transfer from horizontal or vertical rough tubes and tubes with small fins

1979-01-01

303

Heat Transfer and Pressure Drop with Rough Surfaces, a Literature Survey  

International Nuclear Information System (INIS)

This literature survey deals with changes in heat transfer coefficient and friction factor with varying nature and degree of roughness. Experimental data cover mainly the turbulent flow region for both air and water as flow mediums. Semiempirical analysis about changes in heat transfer coefficient due to roughness has been included. An example of how to use these data to design a heat exchanger surface is also cited. The extreme case of large fins has not been considered. Available literature between 1933 - 1963 has been covered

1964-01-01

304

Electron transfer in gas surface collisions  

International Nuclear Information System (INIS)

In this thesis electron transfer between atoms and metal surfaces in general is discussed and the negative ionization of hydrogen by scattering protons at a cesiated crystalline tungsten (110) surface in particular. Experimental results and a novel theoretical analysis are presented. In Chapter I a theoretical overview of resonant electron transitions between atoms and metals is given. In the first part of chapter II atom-metal electron transitions at a fixed atom-metal distance are described on the basis of a model developed by Gadzuk. In the second part the influence of the motion of the atom on the atomic charge state is incorporated. Measurements presented in chapter III show a strong dependence of the fraction of negatively charged H atoms scattered at cesiated tungsten, on the normal as well as the parallel velocity component. In chapter IV the proposed mechanism for the parallel velocity effect is incorporated in the amplitude method. The scattering process of protons incident under grazing angles on a cesium covered surface is studied in chapter V. (Auth.).

1983-01-01

305

Effect of the mass transfer coefficient on the erosion-corrosion rate of specimens tested in the Ciroco loop  

International Nuclear Information System (INIS)

[en] The erosion-corrosion rate of steels should theoretically depend upon the mass transfer coefficient of the outflow. It is shown with 2 examples: 1) Erosion-corrosion after a steam generator orifice used in some nuclear plant. In this case actual thickness of metal erosion are available. Mass transfer is estimated by a polarographic method. 2) Erosion corrosion produced by impact of a jet. A parallel between the mass transfer coefficients obtained by polarography and the measurements of corrosion depths permits a verification of this dependence

1982-05-12

306

Low-Flow Film Boiling Heat Transfer on Vertical Surfaces  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer coefficient...

Munthe Andersen, J. G.; Dix, G. E.; Leonard, J. E.; Sun, K. H.

307

Angular anisotropy of group averaged absorption coefficient and its effect on the behavior of diffusion approach in radiative transfer  

Energy Technology Data Exchange (ETDEWEB)

Multi-group method, a generally accepted procedure for handling the radiative transfer equation, is accompanied by the group averaged absorption coefficient, and actually the coefficient is angularly anisotropic. In the paper, we present a brief discussion how the anisotropy of the coefficient makes the material absorb photons at different rate in each direction, also study its effect on the diffusion approach by comparing the results calculated using multi-group diffusion and multi-group discrete ordinate SN for the isotropic and anisotropic group averaged absorption coefficients respectively, and find that the anisotropy deteriorates the behavior of diffusion approach.

Li Jiwei [Institute of Applied Physics and Computational Mathematics, P.O. Box 8009-14, Beijing 100088 (China)], E-mail: li_jiwei@iapcm.ac.cn; Li Jinghong [Institute of Applied Physics and Computational Mathematics, P.O. Box 8009-14, Beijing 100088 (China)

2009-03-15

308

Angular anisotropy of group averaged absorption coefficient and its effect on the behavior of diffusion approach in radiative transfer  

International Nuclear Information System (INIS)

Multi-group method, a generally accepted procedure for handling the radiative transfer equation, is accompanied by the group averaged absorption coefficient, and actually the coefficient is angularly anisotropic. In the paper, we present a brief discussion how the anisotropy of the coefficient makes the material absorb photons at different rate in each direction, also study its effect on the diffusion approach by comparing the results calculated using multi-group diffusion and multi-group discrete ordinate SN for the isotropic and anisotropic group averaged absorption coefficients respectively, and find that the anisotropy deteriorates the behavior of diffusion approach.

1000-01-00

309

Study on transfer coefficients of 90Sr, 137Cs, natural U, 226Ra and 239Pu in terrestrial food chains  

International Nuclear Information System (INIS)

The aim of study was to provide values of transfer parameter of 90Sr, 137Cs, Natural U, 226Ra and 239Pu in terrestrial food chains, more applicable for Chinese socio-natural conditions. Data of radionuclides contents in agricultural crops and in associated soils, in sheep tissues and in associated grasses were collected in couples. The transfer coefficients in terrestrial food chains (soil-crops, grasses-sheep tissues) were calculated. On basis of statistical analysis, the representative values and 95% ranges of transfer coefficient for 5 radionuclides in 7 kind of agricultural products for southern moist areas and north dry areas were given. Regression analysis showed that relation between the transfer coefficients and the radionuclide contents in their associated soils present a negative correlation, it could be described with a equation: Y = aX-b.

1995-01-01

310

Low-Flow Film Boiling Heat Transfer on Vertical Surfaces  

DEFF Research Database (Denmark)

The phenomenon of film boiling heat transfer for high wall temperatures has been investigated. Based on the assumption of laminar flow for the film, the continuity, momentum, and energy equations for the vapor film are solved and a Bromley-type analytical expression for the heat transfer coefficient versus the film length is obtained. The Helmholtz instability for the steam-liquid interface is analyzed, and it is shown that films beyond a certain length are unstable. Assuming the most unstable wavelength for disturbances at the steam-liquid interface is a reasonable expression for the film length, an average film boiling heat transfer coefficient is obtained.

Munthe Andersen, J. G.; Dix, G. E.

1976-01-01

311

Estimation of overall heat transfer coefficient of cooling system in RF capacitive hyperthermia  

Directory of Open Access Journals (Sweden)

Full Text Available The study presented in this article involves the estimation of the overall heat transfer coefficient of cooling system in RF capacitive hyperthermia treatment using inverse problem based on the conjugate gradient method to provide improved distribution of temperature. The temperature data computed numerically from the direct problem using the finite difference time domain method are used to simulate the temperature measurements. The effects of the errors and sensor positions upon the precision of the estimated results are also considered. The results show that a reasonable estimation of the unknown can be obtained. Finally, measurements in a tissue-equivalent phantom are employed to appraise the reliability of the presented method. The comparison of computed data with measurements shows a good agreement between numerical and experimental results.

Seyed Ali Aghayan; Dariush Sardari; Seyed Rabii Mahdi Mahdavi; Mohammad Hasan Zahmatkesh

2013-01-01

312

Distribution coefficient and transfer factor of stable iodine in agricultural soils in Aomori, Japan  

International Nuclear Information System (INIS)

Soil-to-solution distribution coefficient (Kd) and soil-to-plant transfer factor (TF) were determined for agricultural soils and selected plants in Aomori Prefecture, Japan, by means of analysis of stable I in soil and plant samples. The concentration of I in the soil samples varied between 0.52 and 82.8 mg kg-1 (geometric mean of 4.4 mg kg-1). The Kd, which was defined as the ratio of I concentration in soil to that in water extracted from the soil, was 1.5 x 103 in geometric mean (L/kg). The TF value was defined as the ratio of I concentration in plant to that in soil. Geometric means of the TF on dry weight base obtained in this study were 3.2 x 10-2 for komatsuna, 2.0 x 10-2 for Japanese radish and 2.3 x 10-2 for pasture grass. (author)

2007-01-01

313

Effect factors of heat transfer coefficient between hollow glass microsphere and furnace atmosphere  

International Nuclear Information System (INIS)

In order to achieve an effective control of the heat transfer coefficient (hq) between microsphere and furnace atmosphere in the fabrication of hollow glass micro-sphere by sol-gel technology, the effects of component percentage, temperature and total pressure of gas mixture on hq are studied. Further, the influences of diameter and wall thickness of hollow glass microsphere on hq are also investigated. The results show that in the range of component percentage, temperature and pressure of gas mixture commonly used in the fabrication of hollow glass microsphere by sol-gel technology, the temperature and total pressure of gas mixture and the wall thickness of hollow glass microsphere have little influence on hq, but hq significantly increases with the volume fraction of helium in the furnace atmosphere and significantly decreases with increasing of microsphere diameter. (authors)

2005-01-01

314

Heat transfer coefficient between bed and inserted horizontal tube in a three-phase fluidized bed  

International Nuclear Information System (INIS)

[en] The heat transfer coefficient between bed and horizontal tube wall was measured in three-phase fluidized beds of 19 and 12 cm i.d. Glass spheres with different diameters (particle diameter=0.052-0.22 cm, particle density = 2.5 g.cm-3) and alumina spheres (particle diameter=0.32 cm, apparent particle density=1.62 g.cm-3) were fluidized by the fluid media of air-water or air-aqueous solution of carboxymethyl cellulose. The superficial velocities of gas and liquid were varied in the range of 2.0-16 cm . s-1 and 0.1-8.0 cm . s-1, respectively

1986-01-01

315

On the two-region rewetting model with a step change in the heat transfer coefficient  

International Nuclear Information System (INIS)

[en] The two-region rewetting model of a slab with a constant 'wet' side heat transfer coefficient and a zero 'dry' side one, is solved by the Wiener-Hopf technique (Jones's direct method) and by separation of variables. The Wiener-Hopf technique yields a solution for the rewetting temperature which is simple in form and more accurate than that obtained by separation of variables, especially for high Biot numbers. The two solutions are found to be in good agreement with each other and with those of Coney (1974) and Caflisch and Keller (1981). Accurate results for the rewetting temperature are presented for a wide range of Biot and Peclet numbers. (orig.)

1988-01-01

316

Microstructure Simulation of Al-Cu Alloy Based on Inverse Identified Interfacial Heat Transfer Coefficient  

Science.gov (United States)

The interfacial heat transfer coefficient (IHTC) is taken as one of the most important factors affecting the accuracy of the simulation. In the present paper, the IHTC variation with temperature was obtained by an inverse heat conduction method. Then, a 3D cellular automaton-finite element method was adopted to predict the microstructure of an Al-Cu alloy based on the identified IHTC. It was found that the IHTC was of prime importance for the precise simulation of solidification microstructure, especially in the grains distribution. In addition, the simulated results using the IHTC variation with temperature were found to exhibit a better agreement with the experimental results than those using the constant value.

Bu, X. B.; Li, L. X.; Zhang, L. Q.; Zhu, B. W.; Xu, R.; Wang, S. P.

2013-09-01

317

Experimental Characterization of Heat Transfer Coefficients During Hot Forming Die Quenching of Boron Steel  

Science.gov (United States)

The heat transfer coefficient (HTC) between the sheet metal and the cold tool is required to predict the final microstructure and mechanical properties of parts manufactured via hot forming die quenching. Temperature data obtained from hot stamping experiments conducted on boron steel blanks were processed using an inverse heat conduction algorithm to calculate heat fluxes and temperatures at the blank/die interface. The effect of the thermocouple response time on the calculated heat flux was compensated by minimizing the heat imbalance between the blank and the die. Peak HTCs obtained at the end of the stamping phase match steady-state model predictions. At higher blank temperatures, the time-dependent deformation of contact asperities is associated with a transient regime in which calculated HTCs are a function of the initial stamping temperature.

Caron, Etienne; Daun, Kyle J.; Wells, Mary A.

2013-04-01

318

Correlation of heat transfer coefficient for saturated film boiling during reflood phase prior to quenching  

International Nuclear Information System (INIS)

[en] A correlation of a heat transfer coefficient was derived for the transition flow region between the quench front and the dispersed flow region during the reflood phase. The correlation was compared with data from a small scale reflood experiment with a 4 x 4 heater-rod bundle and FLECHT experiments and showed fairly good agreement with the experimental data. The predicted errors were nearly within +-30% for all the data of the referred small scale reflood experiment, +-20% for all data except for the data of high flooding rate cases (higher than 7.5 x 10-2 m/s) and the data measured at the location just below the spacer grid, and +-20% for two selected FLECHT tests. (author)

1981-01-01

319

Condensation heat transfer coefficient in horizontal stratified cocurrent flow of steam and cold water  

International Nuclear Information System (INIS)

Some studies on direct-contact condensation in cocurrent stratified flow of steam and subcooled water were reviewed. Several approaches have been performed to develop the condensation heat transfer coefficient relationship. The local Nusselt number is correlated in terms of the local water Reynolds and Prandtl numbers as well as the steam Froude number. In addition, a turbulence-centered model, developed principally for gas absorption in several geometries, is modified by using calculated interfacial parameters for the turbulent velocity and length scales. These approaches result in a fairly good agreement with the data, whereas, the turbulence-centered model is here recommended since it is based on the turbulent properties which may be closely related to the condensation phenomena. (Author)

1986-01-01

320

Measurement of condensation Heat Transfer Coefficient inside a vertical tube in the presence of noncondensable gas  

International Nuclear Information System (INIS)

[en] Degradation of condensation HTC (Heat Transfer Coefficient) under an air presence in a vertical tube was explored both experimentally and analytically, with the aim of developing evaluation methods for the design of passive containment cooling systems in the next generation reactors. Measurements were done using a stainless steel tube of 49.5 mm I.D. and 2.0 m length, enclosed by a cooling jacket. Flow rates of steam, air and cooling water, and the system pressure were varied as the experimental parameters. First, condensation HTC was correlated to a function of mixture Reynolds number and air partial pressure ratio, in which thermal resistance of the condensate film was excluded. Secondly, an analogy between heat and mass transfer was applied. The calculated values agreed well with the measured values of condensation HTCs in turbulent flow, while an obvious underestimation was observed for the flow in which mixture Reynolds number was lower than 2,300. Finally, ratios of calculated to experimental HTCs, which include thermal resistances of the condensate film, averaged 1.01 for turbulent steam flow. (author)

1995-01-01

 
 
 
 
321

Simulation of Convective Heat-Transfer Coefficient in a Buried Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available This study presents analytical models allowing to study a forced convection laminar flow in non-established dynamic and thermic regimes. We treated a flow in a bitubular exchanger in permanent thermal contact with a semi-infinite medium, such as the ground. The wall temperature as well as the wall heat flux evolve in the course of time until a quasi-steady mode. The theoretical method is original because it uses Green's functions method to determine the analytical solutions of the heat propagation equation on the wall during the heating phase. These analytical solutions allow to identify the temperature distribution versus time. The complexity of the system geometry as well as the infinity of the medium surrounding the exchanger make the traditional methods of numerical resolution unable to solve the problem. We used, to solve it, the finite volume method coupled with the finite element method at the boundary. We studied the effect of Reynolds number, the fluid entry temperature and the transfer duration on the axial evolution of the heat transfer coefficient. We illustrated also the profile of the temperature field in the fluid medium.

Taoufik Mnasri; Rached B.  Younes; Maher Raddaoui; Salem Elouragini

2008-01-01

322

A Method for Estimating Mass-Transfer Coefficients in a Biofilter from Membrane Inlet Mass Spectrometer Data  

DEFF Research Database (Denmark)

A membrane inlet mass spectrometer (MIMS) was used in combination with a developed computer model to study and improve management of a biofilter (BF) treating malodorous ventilation air from a meat rendering facility. The MIMS was used to determine percentage removal efficiencies (REs) of selected sulfur gases and to provide toluene retention profiles for the model to determine the air velocity and overall mass-transfer coefficient of toluene. The mass-transfer coefficient of toluene was used as a reference for determining the mass transfer of sulfur gases. By presenting the model to scenarios of a filter bed with a consortium of effective sulfur oxidizers, the most likely mechanism for incomplete removal of sulfur compounds from the exhaust air was elucidated. This was found to be insufficient mass transfer and not inadequate bacterial activity as anticipated by the manager of the BF. Thus, knowing the relationship between mass-transfer coefficients and air velocity for a given type of BF allows for an improved dimensioning and managing of this and similar BFs. This research demonstrates that it is possible to estimate mass-transfer coefficients and air velocity in BFs using MIMS in combination with computer modeling. Udgivelsesdato: February

Nielsen, Anders Michael; Nielsen, Lars Peter

2009-01-01

323

Heat transfer from the roughened surface of gas cooled fast breeder reactor fuel element  

International Nuclear Information System (INIS)

[en] The temperature distributions and the augmentation of heat transfer performance by artificial roughening of a gas cooled fast breeder reactor (GCFR) fuel rod cladding are studied. Numerical solutions are based on the axisymmetric assumption for a two-dimensional model for one rib pitch of axial distance. The local and axial clad temperature distributions are obtained for both the rectangular and ramp rib roughened surface geometries. The transformation of experimentally measured convective heat transfer coefficients, in terms of Stanton number, into GCFR values is studied. In addition, the heat transfer performance of a GCFR fuel rod cladding roughened surface design is evaluated. Approximate analytical solution for correlating an average Stanton number is also obtained and satisfactorily compared with the corresponding numerical result for a GCFR design. The analytical correlation is useful in assessing roughened surface heat transfer performance in scoping studies and conceptual design

1979-01-01

324

Comparative analysis and selection of correlations for determination of heat transfer coefficients under conditions characteristic of VVER core emergency cooling  

Energy Technology Data Exchange (ETDEWEB)

As a result of the analysis of a considerable amount of literature on heat transfer in core emergency cooling, a classification is presented of the conditions of heat transfer and two-phase flow, as well as of the respective correlations for the determination of the heat transfer coefficients. On the basis of a comparative analysis recommendations are made concerning some correlations for the determination of heat transfer under the conditions of transition boiling and film boiling with inverted annular flow, slug flow and dispersed flow. Those correlations agree best with the experimental data at the present stage.

Pavlov, V.P.; Shishkova, I.V.; Marinov, M.I.

1985-01-01

325

Prediction of average heat transfer coefficients between a riser's wall and circulating fluidized bed: effect of pressure and temperature  

Energy Technology Data Exchange (ETDEWEB)

A phenomenological model of heat transfer in a transport zone of a circulating fluidized bed (CFB) is developed, which allows for basic specific features of the process: a gas film at the riser's wall, temperature profile in its horizontal section, and the dependence of their characteristics on the concentration of particles. Test data are generalized on the basis of simple semi-empirical relations for calculating a conductive-convective component of the heat transfer coefficient and of the total coefficient of heat exchange between extended surfaces (L > 0.5 m) and a CFB in the transport zone. These formulae allow for the effect of pressure and temperature and are verified within a rather wide range of experimental conditions. (orig.)

Borodulya, V.A.; Teplitsky, Yu.S. [Belarussian Academy of Sciences, Minsk (Belarus). A.V. Luikov Heat and Mass Transfer Inst.

1999-07-01

326

Heat transfer and friction coefficients for air flow in a smooth annulus  

International Nuclear Information System (INIS)

In the Heat Transfer Laboratory of INR various experiments on single rough or smooth rods contained in smooth annuli have been performed in the past. These experiments have been performed with rods of large diameters. Recently however a series of experiments with rough rods of 8 mm O.D. has been carried out. To check if the new experimental apparatus and the experimental techniques used were correct, an experiment was performed with an inner heated tube of 8 mm O.D. contained in the smooth outer tube of 16 mm I.D. used in the experiments with the rough rods. The results of this experiment are reported in the present paper. The friction and heat transfer data obtained with the turbulent flow runs of the present experiment agree well with previous experiments performed at INR with larger smooth annuli. The smaller size of the annulus and the improvements in mass flow and pressure drop measurements have allowed to extend the investigations to laminar flow. The laminar flow friction data can be correlated in terms of fsub(B) versus Re-sub(W), where the gas physical properties in Re-sub(W) are evaluated at the temperature T-sub(W), average between the temperature of the inner surface and the outer surface of the annulus, weighted over the two surfaces. This correlation method has been already suggested by us for rough rods in a smooth tube. The laminar flow heat transfer data, correlated in terms of Nusub(B) versus Gr-sub(W) tend to be lower than the analytical prediction of Heaton, Reynolds and Kays, a fact which could be explained by the superposition of natural convection. (orig.)

327

Calculation of heat and mass transfer coefficients in a packed tower operating with a desiccant-air contact system  

Energy Technology Data Exchange (ETDEWEB)

Packed towers can be used for solar regeneration of aqueous solutions and dehumidification of air using aqueous solutions. These processes involve simultaneous heat and mass transfer with heat effects. In order to design a packed tower for aqueous solution-air contacting operations, heat and mass transfer coefficients for each phase are required. For the present study, aqueous calcium chloride solution is used; ceramic Raschig rings and Berl saddles are used as the packing materials. In this paper air phase transfer coefficients are correlated with flow rates of air and liquid and the temperature of air, whereas liquid phase coefficients are correlated with rates of air and liquid flow, and the temperature and concentration of the liquid.

Gandhidasan, P.; Kettleborough, C.F.; Ullah, M.R.

1986-05-01

328

Development of a new correlation for estimating pool boiling heat transfer coefficient of MEG/DEG/water ternary mixture  

Directory of Open Access Journals (Sweden)

Full Text Available Pool boiling heat transfer coefficient of monoethylene glycol (MEG), diethylene glycol (DEG) and water ternary mixtures has been experimentally measured up to heat flux 114 kW/m2 at various volumetric concentrations of MEG and DEG. As expected, heat transfer coefficient was strongly taken as a direct function of heat flux. Existing well-known correlations are shown to be unable to predict the acceptable values for the tested ternary mixtures, particularly at different concentrations of MEG and DEG. Furthermore, a new modified correlation is developed on the basis of the Stephan - Preußer correlation that predicts the values of heat transfer coefficients with absolute average error of about 7% that is reasonable and acceptable values in compare to other existing correlations.

Sarafraz M.M.; Alavi-Fazel S.A.; Hasanzadeh Y.; Arabshamsabadi A.; Bahram S.

2012-01-01

329

Concentration Dependence of Pool Nucleate Boiling Heat Transfer Coefficients for R134a and Polyolester Oil System  

Science.gov (United States)

This paper presents experimental results of the concentration dependence of heat transfer coefficients for mixtures of R134a and polyolester (POE) oil under the conditions of pool nuc1eateboiling. The experiments are conducted by means of ah horizontal platinum wire at saturation tel11peraturesof 9, 19, and 29°C and at oil concentrations from 0 to 8 mass%. The present results show that the boiling heat transfer coefficient for the system concerned decreases with increasing oil concentration as a whole but increases slightly at a low oil concentration of about 4 mass%. A correlation equation is also given as a function of heat flux, temperature and oil concentration to reproduce the experimental boiling heat transfer coefficient within an uncertainly of about±15%.

Sato, Tomoaki; Takaishi, Yoshinori; Oguchi, Kosei

330

Effect of some additives on mass transfer coefficient at a vibrating horizontal screen  

Energy Technology Data Exchange (ETDEWEB)

The addition of small amounts of high molecular weight substances, such as polymers and surface-active agents, to fluids can produce significant reduction of friction in turbulent flow. The objectiv of the present work is to study the effect of drag-reducing additives such as Polyox WSR 301 and sodium lauryl sulfate (anionic surfactant) on the rate of mass transfer at a vibrating horizontal screen. The variables studied were the concentration of polymer and surfactant, frequency of vibration and amplitude of vibration. (orig.)

Nosier, S.A.; El-Abd, M.Z. [Chemical Engineering Dept., Faculty of Engineering, Alexandria Univ. (Egypt); Zaki, M.M. [Environmental Engineering Dept., Faculty of Engineering, Zagazig Univ. (Egypt)

1998-01-01

331

Determination of coefficients for the universal laws of friction and heat transfer for CFTL calculations  

Energy Technology Data Exchange (ETDEWEB)

The friction factor and Stanton number for flow past a roughened surface are determined by the parameters A and R(h/sup +/) of the universal law of friction and A/sub H/ and G(h/sup +/) of the universal law of heat transfer. The methods to be used for determination of these parameters for the particular roughness to be used in the Core Flow Test Loop (CFTL) are presented. Examples are given concerning the application of these methods to both transitional and fully rough flow using experimental results taken from the literature.

Hodge, S.A.

1980-08-01

332

Determination of coefficients for the universal laws of friction and heat transfer for CFTL calculations  

International Nuclear Information System (INIS)

[en] The friction factor and Stanton number for flow past a roughened surface are determined by the parameters A and R(h+) of the universal law of friction and A/sub H/ and G(h+) of the universal law of heat transfer. The methods to be used for determination of these parameters for the particular roughness to be used in the Core Flow Test Loop (CFTL) are presented. Examples are given concerning the application of these methods to both transitional and fully rough flow using experimental results taken from the literature

1980-01-01

333

Experimental result of BWR post-CHF tests. Critical heat flux and post-CHF heat transfer coefficient. Contract research  

Energy Technology Data Exchange (ETDEWEB)

Authors performed post-CHF experiments under wider pressure ranges of 2 MPa - 18 MPa, wider mass flux ranges of 33 kg/m{sup 2}s - 1651 kg/m{sup 2}s and wider superheat of heaters up to 500 K in comparison to experimental ranges at previous post-CHF experiments. Data on boiling transition, critical heat flux and post-CHF heat transfer coefficient were obtained. Used test section was 4x4-rod bundle with heaters, which diameter and length were the same as those of BWR nuclear fuels. As the result of the experiments, it was found that the boiling transition occurred just below several grid spacers, and that the fronts of the boiling transition region proceeded lower with increase of heated power. Heat transfer was due to nucleate boiling above grid spacers, while it was due to film boiling below grid spacers. Consequently, critical heat flux is affected on the distance from the grid spacers. Critical heat flux above the grid spacers was about 15% higher than that below the grid spacers, by comparing them under the same local condition. Heat transfer by steam turbulent flow was dominant to post-CHF heat transfer, when superheat of heaters was sufficiently high. Then, post-CHF heat transfer coefficient was predicted with heat transfer correlations for single-phase flow. On the other hand, when superhead of heaters was not sufficiently high, post-CHF heat transfer coefficient was higher than the prediction with heat transfer correlations for single-phase flow. Mass flux effect on post-CHF heat transfer coefficient was described by standardization of post-CHF heat transfer coefficient with the prediction for single-phase flow. However, pressure effect, superheat effect and effect of position were not described. Authors clarified that those effects could be described with functions of heater temperature and position. Post-CHF heat transfer coefficient was lowest just blow the grid spacers, and it increased with the lower positions. It increased by about 30% in one span of the grid spacers, which length was about 50 cm. (author)

Iguchi, Tadashi; Anoda, Yoshinari [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Iwaki, Chikako [Toshiba Corp., Tokyo (Japan)

2002-02-01

334

Experimental result of BWR post-CHF tests. Critical heat flux and post-CHF heat transfer coefficient. Contract research  

International Nuclear Information System (INIS)

Authors performed post-CHF experiments under wider pressure ranges of 2 MPa - 18 MPa, wider mass flux ranges of 33 kg/m2s - 1651 kg/m2s and wider superheat of heaters up to 500 K in comparison to experimental ranges at previous post-CHF experiments. Data on boiling transition, critical heat flux and post-CHF heat transfer coefficient were obtained. Used test section was 4x4-rod bundle with heaters, which diameter and length were the same as those of BWR nuclear fuels. As the result of the experiments, it was found that the boiling transition occurred just below several grid spacers, and that the fronts of the boiling transition region proceeded lower with increase of heated power. Heat transfer was due to nucleate boiling above grid spacers, while it was due to film boiling below grid spacers. Consequently, critical heat flux is affected on the distance from the grid spacers. Critical heat flux above the grid spacers was about 15% higher than that below the grid spacers, by comparing them under the same local condition. Heat transfer by steam turbulent flow was dominant to post-CHF heat transfer, when superheat of heaters was sufficiently high. Then, post-CHF heat transfer coefficient was predicted with heat transfer correlations for single-phase flow. On the other hand, when superhead of heaters was not sufficiently high, post-CHF heat transfer coefficient was higher than the prediction with heat transfer correlations for single-phase flow. Mass flux effect on post-CHF heat transfer coefficient was described by standardization of post-CHF heat transfer coefficient with the prediction for single-phase flow. However, pressure effect, superheat effect and effect of position were not described. Authors clarified that those effects could be described with functions of heater temperature and position. Post-CHF heat transfer coefficient was lowest just blow the grid spacers, and it increased with the lower positions. It increased by about 30% in one span of the grid spacers, which length was about 50 cm. (author)

2002-01-01

335

General expansions for nuclear surface and curvature energy coefficients in series of volume terms and surface moments  

Energy Technology Data Exchange (ETDEWEB)

General expansions for the surface, a/sub s/, and curvature, a/sub c/, energy coefficients in series of volume terms (incompressibility and higher order derivatives of the volume energy per particle) and surface moments (surface thickness, skewness, kurtosis,...) are discussed. It is also shown, that the ratio (a/sub c//a/sub s//sup 2/) is better represented by such expansions than a/sub s/ or a/sub c/ alone.

Farine, M.

1988-12-01

336

ITEM WITH AT LEAST ONE THERMOPROGRAMMABLE SWITCHING SECTION FOR APPLICATIONS IN CONTACT WITH MATERIALS HAVING HIGH HEAT TRANSFER COEFFICIENTS  

UK PubMed Central (United Kingdom)

The invention relates to an item with at least one switching section, wherein the at least one switching section a) comprises a shape memory compound that comprises at least one thermoprogrammable shape memory polymer and particles incorporated therein suitable for heating in an alternating electromagnetic field, wherein the shape memory compound has a heat transfer coefficient hschalt and b) comprises an insulating area that surrounds the shape memory compound a) and that has a heat transfer coefficient hiso wherein hiso schalt and to a manufacturing method for such an item.

WEIGEL THOMAS; LENDLEIN ANDREAS; LUETZOW KAROLA; KLEIN FRANK; MADBOULY SAMY

337

Transfer coefficients in a four-cusp duct simulating a typical nuclear reactor channel degraded by accident  

International Nuclear Information System (INIS)

An experimental study on forced convection in a four-cusp duct simulating a typical nuclear reactor channel degraded by accident is presented. Transfer coefficients were obtained by using the analogy between heat and mass tranfer, with the naphtalene sublimation technique. The experiment consisted in forcing air past a four-cusp naphthalene moulded duct. Mass transfer coefficients were determined in nondimensional form as Sherwood number. Experimental curves correlating the Sherwood number with a nondimensional length, x+, were obtained for Reynolds number varying from 891 to 30.374. This range covers typical flow rates that are expected to exist in a degraded nuclear reactor core. (Author)

1985-01-01

338

Impact of External Pressure on the Heat Transfer Coefficient during Solidification of Al-A356 Alloy  

DEFF Research Database (Denmark)

In this paper the interfacial heat transfer coefficient (IHTC) is correlated to applied external pressure, in which IHTC at the interface between A356 aluminum alloy and metallic mold during the solidification of the casting under different pressures were obtained using the Inverse Heat Conduction Problem (IHCP) method. The method covers the expedient of comparing theoretical and experimental thermal histories. Temperature profiles obtained from thermocouples were used in a finite difference heat flow program to estimate the transient heat transfer coefficients. The new simple formula was presented and compared with data in literature which shows acceptable agreement.

Jabbari, Masoud; Ilkhchy, A.Fardi

339

Effect of sprayed density on the pressure drop and mass transfer coefficient in hydrogen-water liquid phase catalytic bed  

International Nuclear Information System (INIS)

[en] The effects of liquid sprayed density on the pressure drop and mass transfer coefficient were discussed in a hydrogen-water liquid phase catalytic bed of ?24 mm x 1000 mm, which was filled with the mixture of hydrophobic catalyst and packing. The pressure drop (?p) increases obviously with the liquid sprayed density (l) in higher gas velocity and slightly with l in lower gas velocity. When the gas velocity is lower, l and entrained liquid (?) have little effect on the mass transfer coefficient (Kya). While the gas velocity is higher, Kya increases with l, ? has effect on Kya. (authors)

2006-01-01

340

Modeling and simulating the drying of grass seeds (Brachiaria brizantha) in fluidized beds: evaluation of heat transfer coefficients  

Directory of Open Access Journals (Sweden)

Full Text Available This work is aimed at modeling the heat transfer mechanism in a fluidized bed of grass seeds (Brachiaria brizantha) for supporting further works on simulating the drying of these seeds in such a bed. The three-phase heat transfer model, developed by Vitor et al. (2004), is the one used for this proposal. This model is modified to uncouple one of the four adjusted model parameters from the gas temperature. Using the first set of experiments, carried out in a laboratory scale batch fluidized bed, the four adjusted model parameters are determined, generating the heat transfer coefficient between particles and gas phase, as well as the heat transfer coefficient between the column wall and ambient air. The second set of experiments, performed in the same unit at different conditions, validates the modified model.

A. C. Rizzi Jr.; M. L. Passos; J. T. Freire

2009-01-01

 
 
 
 
341

Modeling and simulating the drying of grass seeds (Brachiaria brizantha) in fluidized beds: evaluation of heat transfer coefficients  

Scientific Electronic Library Online (English)

Full Text Available Abstract in english This work is aimed at modeling the heat transfer mechanism in a fluidized bed of grass seeds (Brachiaria brizantha) for supporting further works on simulating the drying of these seeds in such a bed. The three-phase heat transfer model, developed by Vitor et al. (2004), is the one used for this proposal. This model is modified to uncouple one of the four adjusted model parameters from the gas temperature. Using the first set of experiments, carried out in a laboratory sca (more) le batch fluidized bed, the four adjusted model parameters are determined, generating the heat transfer coefficient between particles and gas phase, as well as the heat transfer coefficient between the column wall and ambient air. The second set of experiments, performed in the same unit at different conditions, validates the modified model.

Rizzi Jr., A. C.; Passos, M. L.; Freire, J. T.

2009-09-01

342

Thermal conductivity and the electron-ion heat transfer coefficient in condensed media with a strongly excited electron subsystem  

Science.gov (United States)

The two-temperature ( T e > T i ) thermal conductivity coefficient ?2 T and electron-ion heat transfer coefficient ?, which are necessary for the quantitative description of the processes initiated by ultrashort laser pulse, have been calculated using a kinetic equation, the matrix element for the scattering probability, and a screened Coulomb potential describing the interaction between charged particles. Quantitative information has been obtained for coefficients ?2 T and ? values for noble and transition metals, where the d-band electrons play a significant role.

Petrov, Yu. V.; Inogamov, N. A.; Migdal, K. P.

2013-03-01

343

Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere  

Energy Technology Data Exchange (ETDEWEB)

The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface. 24 references.

Courtin, R.

1988-08-01

344

Pressure-induced absorption coefficients for radiative transfer calculations in Titan's atmosphere  

International Nuclear Information System (INIS)

The semiempirical theory of Birnbaum and Cohen (1976) is used to calculate the FIR pressure-induced absorption (PIA) spectra of N2, CH4, N2 + Ar, N2 + CH4, and N2 + H2 under conditions like those in the Titan troposphere. The results are presented graphically and compared with published data from laboratory measurements of PIA in the same gases and mixtures (Dagg et al., 1986; Dore et al., 1986). Good agreement is obtained, with only a slight underestimation of PIA at 300-400/cm in the case of CH4. The absorption coefficients are presented in tables, and it is suggested that the present findings are of value for evaluating the effects of tropospheric clouds on the Titan FIR spectrum and studying the greenhouse effect near the Titan surface. 24 references.

1988-01-01

345

Kinetic study of the concentration dependence of the mass transfer rate coefficient in anion-exchange chromatography of bovine serum albumin  

Energy Technology Data Exchange (ETDEWEB)

The experimental results of a previous study of the mass transfer kinetics of bovine serum albumin (BSA) in ion-exchange chromatography under nonlinear conditions are reevaluated. The analysis of the concentration dependence of the lumped mass-transfer rate coefficient (k{sub m,L}) provides information on the kinetics of axial dispersion, fluid-to-particle mass transfer, intraparticle mass transfer, and adsorption/desorption. The new analysis shows that the contribution of intraparticle mass transfer is the dominant one. Similar to k{sub m,L}, the surface diffusivity (D{sub s}) of BSA increases with increasing concentration. The linear concentration dependence of k{sub m,L} seems to originate in a similar dependence of D{sub s}. The use of a heterogeneous-surface model for the anion-exchange resin provides an explanation of the positive concentration dependence of D{sub s}. This work illustrates how frontal analysis data can be used for a detailed investigation of the kinetics of mass transfer between the phases of a chromatographic column, in addition to its conventional use in the determination of the thermodynamic characteristics of the phase equilibrium.

Miyabe, Kanji; Guiochon, G. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry]|[Oak Ridge National Lab., TN (United States). Div. of Chemical and Analytical Sciences

1999-07-01

346

Time dependence of the {sup 137}Cs and {sup 90}Sr transfer coefficient in a Mediterranean ecosystem  

Energy Technology Data Exchange (ETDEWEB)

The soil-plant transfer of {sup 137}Cs and {sup 90}Sr was studied in a low turnover rate Mediterranean ecosystem. The available activities of the two radionuclides in the soil and their stable chemical analogues, K and Ca, respectively, evolve periodically over time due to the marked dry and wet seasons existing in this type of climate. This seriously restricts the validity of using constant transfer and discrimination coefficients. 7 refs, 3 figs, 2 tabs.

Baeza, A.; Paniagua, J.; Rufo, M. [Univ. de Extremadura, Caceres (Spain). Dpto. de Fisica; Barandica, J. [Univ. Complutense, Madrid (Spain). Dpto. de Ecologia

1996-12-31

347

Two-Phase condensation Heat Transfer Coefficients Heat Transfer Coefficients and Pressure drops of R-404A for different Condensing Temperatures in a smooth and Micro-Fin Tube  

Directory of Open Access Journals (Sweden)

Full Text Available Two phase heat transfer coefficients and pressure drops of R-404A in a smooth (8.56 mm ID) and micro-fin tube (8.96 mm ID) are experimentally investigated. Different from previous studies, the present experiments are performed for different condensing temperatures, with superheating and sub cooling and using hermetically sealed compressor. The test runs are done at average saturated condensing temperatures ranging from 35oC to 60oC. The mass fluxes are between 90 and 800 kg m-2s-1 . The experimental results from both smooth and micro-fin tubes show that the average heat transfer coefficient and pressure drop increases with mass flux but decreases with increasing condensing temperature. The average heat transfer coefficient is 30-210% higher for micro-fin tube than that of smooth tube, with moderate increase in pressure drop ranging from 10-55%. New correlations based on the data gathered during the experimentation for predicting condensation heat transfer coefficients are proposed for wide range of practical applications.

DR. S.N. Sapali; Pradeep A.Patil

2009-01-01

348

Tailoring of Seebeck coefficient with surface roughness effects in silicon sub-50 nm films.  

UK PubMed Central (United Kingdom)

ABSTRACT: The effect of surface roughness on the seebeck coefficient in the sub 50 nm scale silicon ultra thin films is investigated theoretically using nonequilibrium Green's function formalism. For systematic studies, the surface roughness is modelled by varying thickness periodically with square wave profile characterized by two parameters: amplitude (A0) and wavelength (lambda). Since high Seebeck coefficient is obtained if the temperature difference between the ends of device produces higher currents and higher induced voltages, we investigate how the generated current and induced voltage is affected with increasing A0 and lambda. The theoretical investigations show that pseudoperiodicity of the device structure gives rise to two effects: firstly the threshold energy at which the transmission of current starts is shifted towards higher energy sides and secondly transmission spectra of current possess pseudobands and pseudogaps. The width of the pseudobands and their occupancies determine the total generated current. It is found that current decreases with increasing A0 but shows a complicated trend with lambda. The trends of threshold energy determine the trends of Seebeck voltage with roughness parameters. The increase in threshold energy makes the current flow in higher energy levels. Thus the Seebeck voltage i.e. voltage required to nullify this current increases. Increase in Seebeck voltage results in increase in Seebeck coefficient. We find that threshold energy increases with increasing A0 and frequency (1/lambda). Hence Seebeck voltage and Seebeck coefficient increases vice versa. It is observed that Seebeck coefficient is tunable with surface roughness parameters.

Kumar M; Bagga A; Neeleshwar S

2012-03-01

349

Transfer coefficient of 226Ra from vegetation to meadow voles, Microtus pennsylvanicus, on U mill tailings  

International Nuclear Information System (INIS)

[en] The 226Ra level in vegetation growing on U mine tailings in Elliot Lake, Ontario, Canada, was 211 + 22 mBq g-1 (dry weight) compared to less than 7 mBq g-1 (dry weight) in material from a control site. Skeletons of meadow voles (Microtus pennsylvanicus) established on the tailings had concentrations of 226Ra of 6083 +/- 673 mBq per animal in winter; 7163 +/- 1077 mBq per animal in spring; 1506 +/- 625 mBq per animal in summer; and 703 +/- 59 mBq per animal in fall, compared to less than 7 mBq per animal in controls. The 226Ra transfer coefficient from vegetation to voles (defined as total millibecquerels of 226Ra in adult vole per total millibecquerels of 226Ra consumed by the vole in its lifetime) was calculated as 4.6 +/- 2.9 X 10(-2) in summer and 2.8 +/- 0.6 X 10(-2) in fall

1986-01-01

350

Carbon dioxide heat transfer coefficients and pressure drops during flow boiling: Assessment of predictive methods  

Energy Technology Data Exchange (ETDEWEB)

Among the alternatives to the HCFCs and HFCs, carbon dioxide emerged as one of the most promising environmentally friendly refrigerants. In past years many works were carried out about CO{sub 2} flow boiling and very different two-phase flow characteristics from conventional fluids were found. In order to assess the best predictive methods for the evaluation of CO{sub 2} heat transfer coefficients and pressure gradients in macro-channels, in the current article a literature survey of works and a collection of the results of statistical comparisons available in literature are furnished. In addition the experimental data from University of Naples are used to run a deeper analysis. Both a statistical and a direct comparison against some of the most quoted predictive methods are carried out. Methods implemented both for low-medium pressure refrigerants and specifically developed for R744 are used in the comparison. Some general indications about the choice of the predictive methods dependently on the operating conditions are given. (author)

Mastrullo, R.; Mauro, A.W.; Rosato, A. [D.E.TE.C., Facolta di Ingegneria, Universita degli Studi di Napoli Federico II, p.le Tecchio 80, 80125 Napoli (Italy); Vanoli, G.P. [Dipartimento di Ingegneria, Universita degli Studi del Sannio, corso Garibaldi 107, Palazzo dell' Aquila Bosco Lucarelli, 82100 Benevento (Italy)

2010-09-15

351

Heat transfer coefficients of the glass window with an interior high-reflectivity venetian blind  

Energy Technology Data Exchange (ETDEWEB)

The heat transfer coefficient (U-factor) of the glass window with an interior high-reflectivity venetian blind (long-wave reflectivity = 0.93) is studied. Two side-by-side test boxes are built in a room. The window systems tested are 100% glass area without frames, which are equivalent to the center-of-glass of common glass window. Two types of the window systems are tested which are the single glazing and the double glazing with an interior high-reflectivity venetian blind respectively. The effects of slat slope conditions on U-factors are also considered for each of them. The empirical equations of the center-of-glass U-factors are derived from the test data, and some corrections of the effects of window frames and ambient wind velocity are made thereafter. The corrected empirical equations can be easily used to estimate U-factors of the actual glass window with an interior high-reflectivity venetian blind.

Fang, X.

1999-07-01

352

An Experimental Investigation of Heat Transfer Coefficients for Spiral Plate Heat Exchanger  

Directory of Open Access Journals (Sweden)

Full Text Available Spiral plate heat exchangers play a vital role in cooling high density and high viscous fluids. This paper presents an experimental investigation of convective heat transfer co-efficient for electrolytes using spiral plate heat exchanger. The test section consists of a Plate of width 0.3150 m, thickness 0.001 m and mean hydraulic diameter of 0.01 m. The mass flow rate of hot fluid is varying from 0.4 kg sec-1 to 0.8 kg sec-1 and the mass flow rate of cold fluid varies from 0.3 kg sec-1 to 0.8 kg sec-1. Experiments have been conducted by varying the mass flow rate, temperature and pressure of cold fluid, keeping the mass flow rate of hot fluid constant. The effects of relevant parameters on spiral plate heat exchanger are investigated. The data obtained from the experimental study are compared with the theoretical data. Besides, a new correlation for the nusselt number that can be used for practical applications is proposed.

Kaliannan Saravanan; Rangasamy Rajavel

2009-01-01

353

Evaporative heat transfer characteristics of a water spray on micro-structured silicon surfaces  

Energy Technology Data Exchange (ETDEWEB)

Experiments were performed to evaluate the evaporative heat transfer characteristics of spray cooling of water on plain and micro-structured silicon surfaces at very low spray mass fluxes. The textured surface is made of an array of square micro-studs. It was found that the Bond number of the microstructures is the primary factor responsible for the heat transfer enhancement of evaporative spray cooling on micro-structured silicon surface in the present study. A qualitative study of evaporation of a single water droplet on plain and textured silicon surface shows that the capillary force within the microstructures is effective in spreading the deposited liquid film, thus increasing the evaporation rates. Four distinct heat transfer regimes, which are the flooded, thin film, partial dryout, and dryout regimes, were identified for evaporative spray cooling on micro-structured silicon surfaces. The microstructures provided better cooling performance in the thin film and partial dryout regime and higher liquid film breakup heat flux, because more water was retained on the heat transfer surface due to the capillary force. Heat transfer coefficient and temperature stability deteriorated greatly once the liquid film breakup occurred. The liquid film breakup heat flux increases with the Bond number. Effects of surface material, system orientation and spray mass flux were also addressed in this study. (author)

Hsieh, Cheng-Chieh; Yao, Shi-Chune [Department of Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States)

2006-03-15

354

Negative surface-plasmon dispersion coefficient: A physically illustrative, exact formula  

Energy Technology Data Exchange (ETDEWEB)

It is shown that in the nonretarded regime, the frequency of the long-wavelength surface plasmon of a free-electron metal is directly related to the overlap of the metal's unperturbed electron density and the normalized, fluctuating potential of the surface plasmon. This result directly expresses the idea that the surface plasmon's frequency depends on the efficiency with which its electric potential energy can be interchanged with electron kinetic energy. It shows that a negative surface-plasmon dispersion coefficient can be interpreted in terms of decreasing overlap of the fluctuating potential and the unperturbed electron density, as the plasmon wave vector increases.

Feibelman, P.J. (Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-5800 (USA)); Tsuei, K.D. (Department of Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396 (USA))

1990-04-15

355

Thermal accommodation coefficient of helium and argon on an amorphous SiO/sub 2/ surface  

Energy Technology Data Exchange (ETDEWEB)

The thermal accommodation coefficient was determined for the interaction of two inert gases, helium and argon, on a surface composed of thermally grown amorphous silicon dioxide. The surface was processed as an integrated circuit chip and utilized components capable of generating heat and measuring temperature. The accommodation coefficient of helium on clean SiO/sub 2/ was found to be 0.198, while that for argon was 0.421. Both one-dimensional and three-dimensional continuum theory models of the accommodation coefficient were used for comparison with the experimental data. Correlation for helium is good when the well depth and range parameter of the Morse interacting gas potential are chosen to be: a = 1.67 A/sup -1/ and D = 550 cal/mole. The Debye temperature was computed from elastic constants to be 498/sup 0/K.

McFall, A.

1980-01-01

356

Mass transfer coefficient of tritium from molten lithium-lead alloy (Li17Pb83) to environmental gas under neutron irradiation  

International Nuclear Information System (INIS)

[en] The mass transfer coefficient of tritium from molten Li17Pb83 alloy to environmental gas was determined by in-situ tritium release experiments under neutron irradiation in the temperature range from 400 to 700deg C. The tritium residence time in the sample in Al2O3 crucible was measured and a tritium release model was applied to obtain the mass transfer coefficient. The mass transfer coefficient decreased with increasing H2 partial pressure in He sweep gas up to 104 Pa at 600deg C, and its maximum value was 5.1x10-3[m s-1]. At 103 Pa in H2 pressure, it was expressed as follows: KD=2.5x10-3[m s-1]xexp(-30.7[kJ mol-1]/RT). From the dependence of KD on H2 pressure and the value of the activation energy in KD, it was concluded that the rate-controlling process is a liquid film diffusion above 103 Pa in H2 pressure while, below 102 Pa, some surface reaction was considered to be a rate-controlling process. (orig.)

1991-01-01

357

On-line analysis of local values of the heat transfer coefficient during a pressurized thermal shock  

International Nuclear Information System (INIS)

[en] This paper investigates the determination of local, non-stationary values of the heat transfer coefficient (h) in the cooling phase of the pressurized thermal shock (PTS) events and in the cooling phase of the large scale PTS experiments

1989-01-01

358

Analysis of heat transfer coefficient and exit conditions of moisture sepatrator reheater with the variation of power  

International Nuclear Information System (INIS)

[en] The relation of heat transfer coefficient with the variation of power was derived. The exit conditions of moisture separator reheater (MSR) are also derived, where by theoretical base can be provided for calculation and designing the temperature control system

1988-01-01

359

Evaluation of heat transfer coefficient in assisting mixed convection on a vertical element with uniform heat flux  

International Nuclear Information System (INIS)

[en] The loss of cooling accident (LOCA) in a nuclear reactor is a case where the heat transfer by forced convection is of the same order of magnitude as the heat transfer by natural convection. Two simple theoretical solutions for evaluating the heat transfer coefficient are presented, assuming a combined velocity and temperature profile of natural and forced convection, within the boundary layer. The following mathematical form is proposed: Y= [1+Xsup(n)]sup(1/n) which is a general expression for a combined effect of wo limiting solutions. (author)

1985-01-01

360

Coefficient of friction between carbon steel and perlite concrete surfaces. Test report  

International Nuclear Information System (INIS)

The results of coefficient of friction, ?, tests conducted on perlite blocks and carbon steel plates under various conditions are discussed. Variables included in the test entailed the use of lubricants (i.e. water and simulated radioactive waste solution) abrasives (120 grit, 60 grit, 40 grit sand paper) applied to the surfaces of the perlite block and carbon steel plates

1978-01-01

 
 
 
 
361

Evaluation Of Mass Transfer Coefficient By Single Droplet Experiment In A Water-Uranyl Nitrake-TBP Diluted In Normal Dodecane System  

International Nuclear Information System (INIS)

[en] In order to evaluate the mass transfer coefficient in a solvent extraction, an experiment was conducted by single droplet failing method. Single droplet of uranyl nitrate solution were allowed to fall into a solvent of 30 % TBP diluted in normal dodecane. The mass transfer coefficient was obtained for the various solute concentrations, column heights and droplet diameters by measuring the concentration change of solute the feed and effluent. the mass transfer coefficient results of the relationships of the internal circulation as well as droplet oscillation, taking place with certain droplet diameter, with the mass transfer coefficient of the system, were also presented. (authors). 16 refs, 7 figs

1991-01-01

362

On development of analytical closure relationships for local wall friction, heat and mass transfer coefficients for sub-channel codes  

International Nuclear Information System (INIS)

[en] The purpose has been to describe an approach suggested for constructing generalized closure relationships for local and subchannel wall friction, heat and mass transfer coefficients, with not only axial and transversal parameters taken into account, but azimuthal substance transfer effects as well. These constitutive relations that are primary for description of one- and two-phase one-dimensional flow models can be derived from the initial 3-D drift flux formulation. The approach is based on the Reynolds flux, boundary layer and generalized coefficient of substance transfer. One more task has been to illustrate the validity of the 'conformity principle' for the limiting cases. The method proposed is based on the similarity theory, boundary layer model, and a phenomenological description of the regularities of the substance transfer (momentum, heat, and mass), as well as on an adequate simulation of the forms of flow structure by a generalized approach to build (an integrated in form and semi-empirical in maintenance structure) analytical relationships for wall friction, heat and mass transfer coefficients. (author)

2000-01-01

363

FEM method with the use of Trefftz functions for determination of heat transfer coefficient in a minichannel  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the FEM method for determination of boiling heat transfer coefficient in cooling liquid flow in a rectangular minichannel with asymmetric heating. Experimental research has focused on the transition from single phase forced convection to nucleate boiling, i.e. the zone of boiling incipience. The “boiling front” location has been determined from the temperature distribution of the heated wall obtained from liquid crystal thermography. The main part of the test section has been a minichannel of pre-set depth from 0.7 to 2.0 mm, of different spatial orientations. Local values of heat transfer coefficient have been determined following the solution of the two-dimensional inverse heat transfer problem. This problem has been solved with the use of Trefftz functions. Trefftz functions have been used to construct base functions in the finite element method (FEMT).

Piasecka Magdalena; Maciejewska Beata

2012-01-01

364

Effect of azimuthal variation of heat-transfer coefficient and pellet-cladding gap on fuel-pin cladding deformation  

International Nuclear Information System (INIS)

[en] The importance of azimuthal temperature variation upon the diametral strain of PWR zircaloy cladding at fuel pin failure is discussed and causes of temperature gradients are considered. A correlation between the surface heat-transfer coefficient profile and the pitch-to-diameter ratio of the pin bundle has been incorporated in the ADVICE computer code. This enables the code to calculate the temperature distribution in a segment of the fuel pin and hence to predict the deformation of the fuel cladding, both before and after contact with adjacent rods. The code also predicts the bowing of the cladding and relative movement between the fuel pellet and the cladding. Two postulated loss-of-coolant flow histories have been studied using the ADVICE code, and estimates of the deformation histories and the failure strains are presented. In the first case the cladding failed while in the alpha phase and the failure strain was limited by temperature gradients caused by unstable bowing. In the second, the cladding started to change phase before cladding substantial deformation had occurred and it hardly bowed at all. In this case, the cladding temperature remained relatively uniform and a higher failure strain was predicted. (author)

1985-01-01

365

Film cooling characteristics of rows of round holes at various streamwise angles in a crossflow: Part II. Heat transfer coefficients  

Energy Technology Data Exchange (ETDEWEB)

Measurements of heat transfer coefficient (h) are presented for rows of round holes at streamwise angles of 30{sup o}, 60{sup o} and 90{sup o} with a short but engine representative hole length (L/D=4). The study began with a single row of holes with pitch-to-diameter ratios of 3 and 6, followed by two inline and staggered rows for each hole spacing and streamwise inclination, which amount to 105 different test cases in addition to the 21 test cases presented on the single hole [C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single round hole at various angles in a crossflow: Part I. Effectiveness, Int. J. Heat Mass Transfer, in press; C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of a single round hole at various angles in a crossflow: Part II. Heat transfer coefficients, Int. J. Heat Mass Transfer, in press]. The present investigation is a continuation of the previous work [Yuen and Martinez-Botas, Parts I and II, in press] with the same test facility, operating conditions (freestream Reynolds number, Re{sub D} of 8563, and blowing ratio, 0.33=transfer method, therefore the results presented in the form of h/h{sub 0}, which is the ratio of heat transfer coefficient with film cooling to that without, are directly comparable. Both local values and laterally averaged ones are presented, the latter refers to the averaged value across the central hole. The corresponding measurements of effectiveness for the rows of holes are presented in a companion paper [C.H.N. Yuen, R.F. Martinez-Botas, Film cooling characteristics of rows of round holes at various angles in a crossflow: Part I. Effectiveness, Int. J. Heat Mass Transfer, submitted for publication]. The low effectiveness observed with the 90{sup o} holes in the companion paper [Yuen and Martinez-Botas, submitted for publication] and the relatively large heat transfer coefficient presented here, suggest that the normal injection should only be used in situations where shallower holes are not feasible. The combined performance of effectiveness and heat transfer coefficient suggests that the two inline rows are likely to be advantageous in the film cooling of turbine blades with good coverage per unit mass flow of cooling air and lower thermal stresses due to the smaller heat load. (author)

Yuen, C.H.N.; Martinez-Botas, R.F. [Department of Mechanical Engineering, Imperial College of Science, Technology and Medicine, London (United Kingdom)

2005-11-01

366

Macrokinetics of surface reactions in a liquid or gas flow and an approximate method of calculating the mass-transfer rate of the reacting particles  

Science.gov (United States)

A simple approximate formula is proposed for calculating the mass-transfer coefficient for a moving reactive particle, the surface of which is the site of a heterogeneous chemical reaction with arbitrary kinetics.

Gupalo, Yu. P.; Polyanin, A. D.; Ryazantsev, Yu. S.; Sergeev, Yu. A.

1981-08-01

367

Enhanced heat transfer surface for cast-in-bump-covered cooling surfaces and methods of enhancing heat transfer  

Energy Technology Data Exchange (ETDEWEB)

An annular turbine shroud separates a hot gas path from a cooling plenum containing a cooling medium. Bumps are cast in the surface on the cooling side of the shroud. A surface coating overlies the cooling side surface of the shroud, including the bumps, and contains cooling enhancement material. The surface area ratio of the cooling side of the shroud with the bumps and coating is in excess of a surface area ratio of the cooling side surface with bumps without the coating to afford increased heat transfer across the element relative to the heat transfer across the element without the coating.

Chiu, Rong-Shi Paul (Glenmont, NY); Hasz, Wayne Charles (Pownal, VT); Johnson, Robert Alan (Simpsonville, SC); Lee, Ching-Pang (Cincinnati, OH); Abuaf, Nesim (Lincoln City, OR)

2002-01-01

368

A theoretical analysis of film boiling heat transfer from vertical surfaces to subcooled liquids  

International Nuclear Information System (INIS)

[en] A theoretical model has been developed for calculating the film boiling heat transfer coefficient from a vertical surface in inverted annular flow. The momentum and continuity equations for the laminar vapour film are solved using the one-dimensional integral technique similar to the analysis of single-phase boundary layers. In the analysis, the radiation, subcooling and mass flux effects are considered. The resultant equation is an ordinary non-linear differential equation which can be integrated numerically to calculate the heat transfer coefficient. So far, the model correctly exhibits the known effects of all relevant independent parameters on the h. t. coefficient, however, for high flow and subcooled conditions, the h. t. coefficient is generally underpredicted in view of available experimental data. Therefore, an attempt was made to improve the theoretical predictions. An approximate analytical solution has been obtained in dimesionless form whose coefficients are to be adjusted to fit the experimental data. Thus, a semi-empirical correlation has been obtained which properly predicts the film boiling h. t. coefficient

1987-01-01

369

Relationship between the friction coefficient and velocity of two cactus pear (Opuntia ficus india L.) cultivars on different surfaces  

UK PubMed Central (United Kingdom)

The static and dynamic coefficients of friction were determined for two cactus pear cultivars against four different structural materials, namely galvanised steel, rubber, plywood and paper for surface moving velocities of 5.35-26.72 mm s?¹. Velocity affected the dynamic coefficient more than the static coefficient. Differences between the tested surfaces were most pronounced at a velocity of 18.63 mm s?¹. The effects of velocity and friction surface varied inconsistently between the two cultivars.

Kabas Onder; Ozmerzi Aziz

2009-01-01

370

Heat transfer from a hot surface to an impinging spray  

International Nuclear Information System (INIS)

The heat transfer between a liquid spray and a surface at a temperature above the liquid boiling point is relevant to various technologies. In general the heat flux rate depends on surface temperature, surface and liquid thermophysical properties, surface conditions, drops diameter and impact velocity, flow rate of spray and orientation of surface relative to the impinging flow and to the gravity field. Most of the available literature deals with relatively large drops so that very little is known for the case of very small drops. In this situation the heat transfer rate becomes rather poor since impinging droplets do not wet the surface. Toda suggests that a decrease of drop mean diameter moves the range of the transition region toward higher temperatures. In this work experiment investigation of the heat transfer from a hot surface to very small drops is reported. (author)

1985-01-01

371

Temperature dependence of volume and surface symmetry energy coefficients of nuclei  

International Nuclear Information System (INIS)

The thermal evolution of the energies and free energies of a set of spherical and near-spherical nuclei spanning the whole periodic table are calculated in the subtracted finite-temperature Thomas-Fermi framework with the zero-range Skyrme-type KDE0 and the finite-range modified Seyler-Blanchard interaction. The calculated energies are subjected to a global fit in the spirit of the liquid-drop model. The extracted parameters in this model reflect the temperature dependence of the volume symmetry and surface symmetry coefficients of finite nuclei, in addition to that of the volume and surface energy coefficients. The temperature dependence of the surface symmetry energy is found to be very substantial whereas that of the volume symmetry energy turns out to be comparatively mild.

2012-09-19

372

Temperature dependence of volume and surface symmetry energy coefficients of nucle  

CERN Document Server

The thermal evolution of the energies and free energies of a set of spherical and near-spherical nuclei spanning the whole periodic table are calculated in the subtracted finite-temperature Thomas- Fermi framework with the zero-range Skyrme-type KDE0 and the finite-range modified Seyler-Blanchard interaction. The calculated energies are subjected to a global fit in the spirit of the liquid-drop model. The extracted parameters in this model reflect the temperature dependence of the volume symmetry and surface symmetry coefficients of finite nuclei, in addition to that of the volume and surface energy coefficients. The temperature dependence of the surface symmetry energy is found to be very substantial whereas that of the volume symmetry energy turns out to be comparatively mild.

De, J N; Agrawal, B K

2012-01-01

373

MASS TRANSFER COEFFICIENTS FOR A NON-NEWTONIAN FLUID AND WATER WITH AND WITHOUT ANTI-FOAM AGENTS  

International Nuclear Information System (INIS)

Mass transfer rates were measured in a large scale system, which consisted of an 8.4 meter tall by 0.76 meter diameter column containing one of three fluids: water with an anti-foam agent, water without an anti-foam agent, and AZ101 simulant, which simulated a non-Newtonian nuclear waste. The testing contributed to the evaluation of large scale mass transfer of hydrogen in nuclear waste tanks. Due to its radioactivity, the waste was chemically simulated, and due to flammability concerns oxygen was used in lieu of hydrogen. Different liquids were used to better understand the mass transfer processes, where each of the fluids was saturated with oxygen, and the oxygen was then removed from solution as air bubbled up, or sparged, through the solution from the bottom of the column. Air sparging was supplied by a single tube which was co-axial to the column, the decrease in oxygen concentration was recorded, and oxygen measurements were then used to determine the mass transfer coefficients to describe the rate of oxygen transfer from solution. Superficial, average, sparging velocities of 2, 5, and 10 mm/second were applied to each of the liquids at three different column fill levels, and mass transfer coefficient test results are presented here for combinations of superficial velocities and fluid levels.

2009-09-09

374

The effect of surface movements on nitrogen mass transfer in liquid iron  

Science.gov (United States)

Marangoni convection due to surface tension gradients set up in a nitrogen-liquid iron system at 1873 K has been mathematically simulated and experimentally confirmed by measuring the rate of nitrogen absorption into liquid iron and by observing the free surface motion of liquid iron via zirconium oxide particles using X-ray radiography. This surface flow was created by blowing nitrogen gas through a small lance over the free surface of the liquid iron contained in an alumina boat under resistance heating. Absorption measurements indicated that the mass-transfer coefficient of nitrogen in liquid iron due to Marangoni convection ( k {m/1}>=1.5×10-4 m/s) is slightly less than that due to induction stirring ( k {m/1}=2.1×10-4 to 1.5×10-4 m/s). The free surface velocity induced by the surface tension gradient, with an initial composition difference of 425 to 10 ppm, was found to be of the order of 0.05 to 0.11 m/s. Mathematical modeling was also carried out to determine the velocity and nitrogen concentration profiles in the alumina boat. It was found that Marangoni convection creates mildly turbulent flows in liquid iron. Good agreements between the experimentally obtained data (nitrogen concentration and surface velocity) and the computed results were attained when a constant eddy viscosity which was five times the molecular value was assumed. This prescription allows both the predicted apparent mass-transfer coefficient and the predicted surface velocity to match the experimental results simultaneously. Note that the transport coefficients in the momentum and the convective-diffusive equations are correlated by the turbulent Schmidt number. The dimensionless mass-transfer correlation obtained for the present N-Fe system at 1873 K under resistance heating was found to be Sh=0.104 Re0.7·Sc0.7 with Sc=79.5 (3500

Hirashima, N.; Choo, R. T. C.; Toguri, J. M.; Mukai, K.

1995-10-01

375

Effects of bridge cable surface roughness and cross-sectional distortion on aerodynamic force coefficients  

DEFF Research Database (Denmark)

Theoretical and experimental investigations to date have assumed that bridge cables can be modeled as ideal circular cylinders and the associated aerodynamic coefficients are invariant with the wind angle-of-attack. On the other hand, bridge cables are normally characterized by local alterations of their inherent surface roughness and shape, which might present a significant disturbance for the surrounding wind flow. The present study focuses on the experimental determination, based on static wind tunnel tests, of the aerodynamic coefficients of full-scale bridge cable section models both perpendicular and inclined to the flow, for varying wind angles-of-attack. The wind tunnel test results demonstrate that the aerodynamic coefficients of bridge cables can be significantly affected by the wind angle-of-attack.

Matteoni, G.; Georgakis, C.T.

2012-01-01

376

Further studies on the time dependence of the mass transfer coefficients for the system uranyl nitrate - nitric acid - TBP  

International Nuclear Information System (INIS)

[en] Overall mass transfer coefficients as a function of time for the transfer of uranium between nitric acid and tri-butyl phosphate have been measured using the quasi-steady state droplet technique. The time dependence of the mass transfer coefficient is known to be a result of a corresponding decrease in the frequency of interfacial turbulence as the interface ages. The present study reports several supporting experiments carried out in an attempt to gain a better understanding of this phenomenon. The experimental conditions investigated concentrated on the extraction of uranyl nitrate into and from tri-n-butylphosphate, and included measurements of the mass transfer coefficients to examine the effect of solute loading of the solvent continuous phase, the effect of drop size, and the effect of a change of solvent phase diluent. A study of the backwashing of uranyl nitrate, in which interfacial turbulence is not observed, from the solvent phase to an aqueous one was made. An explanation for the cause of the dampening of interfacial turbulence is proposed and discussed. (author)

1990-01-01

377

Heat transfer enhancement and surface thermostabilization for pool boiling on porous structures  

Directory of Open Access Journals (Sweden)

Full Text Available The scope of the article includes the description of the experimental setup, methodology of the experimental studies, the study results for pool boiling heat transfer coefficient encountered on sintered capillary porous coverings. The results of own studies presented here refer to the boiling in a large volume on copper fibrous coverings. Hysteresis type I, II and III were described. Several examples of capillary porous surface coverings applications in purposely chosen complex boiling heat transfer processes have been presented based on Wojcik and Poniewski patents.

Wojcik Tadeusz Michal

2012-01-01

378

Boiling heat transfer in a flat slot between heating surface and perforated plate  

International Nuclear Information System (INIS)

The results are presented of the experimental study of heat transfer and crisis at nitrogen boiling in a flat gap between the horizontal heating surface and perforated plate. The gap width is 1.0 to 5.6 mm, diameter of holes is 1.0 to 2.0 mm, their spacing being 3.0 to 12.0 mm. The geometrical parameters dependence of the heat transfer coefficient and crisis characteristics is invesigated, the experimental data are compared with the results reported by other authors and calculations by some well-known formulas. 12 refs.; 3 figs.; 4 tabs.

1987-01-01

379

Surface heat transfer due to sliding bubble motion  

International Nuclear Information System (INIS)

The presence of a rising bubble in a fluid can greatly enhance heat transfer from adjacent heated surfaces such as in shell and tube heat exchangers and chemical reactors. One specific case of this is when a bubble impacts and slides along the surface. The result is heat transfer enhancement by two main mechanisms: first, the bubble itself acting as a bluff body, and second, the wake generated behind the bubble leads to increasing mixing. The current research is concerned with measuring the heat transfer from a submerged heated surface that is subject to a sliding bubble flow. An ohmically heated 25 ?m thick stainless steel foil, submerged in a water tank, forms the test surface. An air bubble is injected onto the lower surface of the test plate, it slides along its length and the effects are monitored by two methods. Thermochromic liquid crystals (TLC's) are used in conjunction with a high speed camera to obtain a time varying 2D temperature map of the test surface. A second synchronised camera mounted below the foil records the bubble motion. Tests are performed at angles of 10 deg., 20 deg. and 30 deg. to the horizontal. This paper reports on the enhancement of the heat transfer due to the bubble. It has been found that the angle made between the heated surface and the horizontal influences heat transfer by changing the bubble's motion. In general, a steeper angle leads to a higher bubble velocity, which results in greater heat transfer enhancement

2009-01-01

380

Heat Transfer Between Gas Fluidized Beds and Vertical Exchanger Surfaces.  

Science.gov (United States)

After giving an introduction to the characteristic behavior of the heat transfer between vertical exchanger surfaces and the moving bulk material of a fluidized bed and describing the method of measurement employed, the author deals in detail with the inf...

R. Wunder A. Mersmann

1978-01-01

 
 
 
 
381

Sticking coefficient and SIMS of hydrocarbons on fusion relevant plasma-sprayed tungsten surfaces  

Energy Technology Data Exchange (ETDEWEB)

In this work we concentrate on the quantification of the sticking coefficient of CD{sub 3}{sup +} on fusion relevant plasma-sprayed tungsten (PSW) surfaces in the collision energy range from about 0 up to 100eV. PSW samples were cut from ASDEX Upgrade tiles and both untreated and electropolished surfaces are investigated. A collision energy, E{sub coll}, selected CD{sub 3}{sup +} ion beam deposits hydrocarbon layers onto the target surfaces which are ex-situ analyzed by nuclear reaction analysis (NRA) via D({sup 3}He,p){sup 4}He at 800kV and 2.5MeV, respectively. The sticking coefficient, S, for deuterium has been found to be collision energy dependent, decreasing with increasing energy. It is in the order of S{approx}0.4 for PSW and S{approx}0.1 for electro polished PSW at E{sub coll}=10eV. Secondary ion mass spectra of charged particles are recorded after ion-surface collisions with the polished PSW surface for collision energies up to 100eV. While at very low collision energies below about 10eV only simple reflection of CD{sub 3}{sup +} is observed, at higher collision energies both fragmentation of the projectile and fragmentation of ion-surface reaction products are observed. Concerning the stability of the layers we prove that hydrogen exchange plays a role on the time scale of weeks.

Schustereder, W. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Assoziation, Boltzmannstrasse 2, D-85748 Garching (Germany)]. E-mail: Werner.Schustereder@ipp.mpg.de; Rasul, B. [Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Endstrasser, N. [Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Zappa, F. [Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Grill, V. [Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Scheier, P. [Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Maerk, T.D. [Institut fuer Ionenphysik und Angewandte Physik, Universitaet Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria)

2007-05-15

382

Sticking coefficient and SIMS of hydrocarbons on fusion relevant plasma-sprayed tungsten surfaces  

International Nuclear Information System (INIS)

[en] In this work we concentrate on the quantification of the sticking coefficient of CD3+ on fusion relevant plasma-sprayed tungsten (PSW) surfaces in the collision energy range from about 0 up to 100eV. PSW samples were cut from ASDEX Upgrade tiles and both untreated and electropolished surfaces are investigated. A collision energy, Ecoll, selected CD3+ ion beam deposits hydrocarbon layers onto the target surfaces which are ex-situ analyzed by nuclear reaction analysis (NRA) via D(3He,p)4He at 800kV and 2.5MeV, respectively. The sticking coefficient, S, for deuterium has been found to be collision energy dependent, decreasing with increasing energy. It is in the order of S?0.4 for PSW and S?0.1 for electro polished PSW at Ecoll=10eV. Secondary ion mass spectra of charged particles are recorded after ion-surface collisions with the polished PSW surface for collision energies up to 100eV. While at very low collision energies below about 10eV only simple reflection of CD3+ is observed, at higher collision energies both fragmentation of the projectile and fragmentation of ion-surface reaction products are observed. Concerning the stability of the layers we prove that hydrogen exchange plays a role on the time scale of weeks

2007-01-01

383

Local heat transfer coefficients for reflux condensation experiment in a vertical tube in the presence of noncondensable gas  

International Nuclear Information System (INIS)

[en] The local heat transfer coefficient is experimentally investigated for the reflux condensation in a countercurrent flow between the steam-air mixture and the condensate. A single vertical tube has a geometry which is a length of 2.4 m, inner diameter of 16.56 mm and outer diameter of 19.05 mm and is made of stainless steel. Air is used as a noncondensable gas. The secondary side has a shape of annulus around vertical tube and the lost heat by primary condensation is transferred to the coolant water. The local temperatures are measured at 11 locations in the vertical direction and each location has 3 measurement points in the radial direction, which are installed at the tube center, at the outer wall and at the coolant side. In three different pressures, the 27 sets of data are obtained in the range of inlet steam flow rate 1.348?3.282 kg/hr, of inlet air mass fraction 11.8?55.0 percent. The investigation of the flooding is preceded to find the upper limit of the reflux condensation. Onset of flooding is lower than that of Wallis' correlation. The local heat transfer coefficient increases as the increase of inlet steam flow rate and decreases as the increase of inlet air mass fraction. As an increase of the system pressure, the active condensing region is contracted and the heat transfer capability in this region is magnified. The empirical correlation is developed by 165 data of the local heat transfer. As a result, the Jacob number and film Reynolds number are dominant parameters to govern the local heat transfer coefficient. The rms error is 17.7 percent between the results by the experiment and by the correlation. (author)

1999-01-01

384

On the determination of the overall heat transmission coefficient and soil heat flux for a fog cooled, naturally ventilated greenhouse: Analysis of radiation and convection heat transfer  

International Nuclear Information System (INIS)

A physical model for analyzing the radiative and convective heat transfer in a fog cooled, naturally ventilated greenhouse was developed for estimating the overall heat transmission coefficient based on the conduction, convection and thermal radiation heat transfer coefficients and for predicting the soil heat flux. The contribution of the water vapor of the inside air to the emission and absorption of thermal radiation was determined. Measurements of the outside and inside greenhouse environments to be used in the analysis were conducted around solar noon (12:19-13:00) on a hot sunny day to provide the maximum solar radiation transmission into the greenhouse. The net solar radiation flux measured at the greenhouse floor showed a reasonable agreement with the predicted value. The net fluxes were estimated around noon. The average net radiation (solar and thermal) at the soil surface was 220.0 W m-2, the average soil heat flux was 155.0 W m-2 and the average contribution of the water vapor of the inside air to the thermal radiation was 22.0 W m-2. The average overall heat transmission coefficient was 4.0 W m-2 C-1 and was in the range between 3.0 W m-2 C-1 and 6.0 W m-2 C-1 under the different hot summer conditions between the inside and outside of the naturally ventilated, fog cooled greenhouse.

2006-01-01

385

A comparison of mass transfer coefficients between trickle-bed, hollow fiber membrane and stirred tank reactors.  

Science.gov (United States)

Trickle-bed reactor (TBR), hollow fiber membrane reactor (HFR) and stirred tank reactor (STR) can be used in fermentation of sparingly soluble gasses such as CO and H2 to produce biofuels and bio-based chemicals. Gas fermenting reactors must provide high mass transfer capabilities that match the kinetic requirements of the microorganisms used. The present study compared the volumetric mass transfer coefficient (K(tot)A/V(L)) of three reactor types; the TBR with 3 mm and 6 mm beads, five different modules of HFRs, and the STR. The analysis was performed using O2 as the gaseous mass transfer agent. The non-porous polydimethylsiloxane (PDMS) HFR provided the highest K(tot)A/V(L) (1062 h(-1)), followed by the TBR with 6mm beads (421 h(-1)), and then the STR (114 h(-1)). The mass transfer characteristics in each reactor were affected by agitation speed, and gas and liquid flow rates. Furthermore, issues regarding the comparison of mass transfer coefficients are discussed. PMID:23434811

Orgill, James J; Atiyeh, Hasan K; Devarapalli, Mamatha; Phillips, John R; Lewis, Randy S; Huhnke, Raymond L

2013-02-04

386

Transfer coefficients of 137Cs via the forage-cow-milk pathway in Aomori Prefecture of Japan  

International Nuclear Information System (INIS)

The transfer of radiocesium to foodstuff of cattle is very serious, because it contributes significantly to internal exposure resulting from the intake of 137Cs through the feed-cow-milk pathway. The transfer coefficient from feed to milk (Fm) is widely used to predict the dose to man from the radioactivity released to the biosphere. A commercial fuel reprocessing plant is under construction in Rokkasho-mura/Aomori Prefecture, the northeastern district of Japan. To figure out Fm under conventional farming conditions, therefore, transfer of 137Cs deposited in the environment in cooperation with two daily farms in this region. Transfer factors for 137Cs from feed to cow's milk have been obtained from data acquired from biweekly routine monitoring program under the two dissimilar farming conditions. The one dairy farm condition is mainly composed of high hay ration and the other is high concentrate ration. As a result of the experiments, 137Cs activity of milk correlated significantly with that of feed. The mean transfer coefficients of 137Cs to milk were calculated to be 0.0037 and 0.0063 (d/l), respectively. (author)

1994-01-01

387

Mass absorption and mass energy transfer coefficients for 0.4-10 MeV gamma rays in elemental solids and gases  

Energy Technology Data Exchange (ETDEWEB)

The mass energy absorption, the mass energy transfer and mass absorption coefficients have been widely used for problems and applications involving dose calculations. Direct measurements of the coefficients are difficult, and theoretical computations are usually employed. In this paper, analytical equations are presented for determining the mass energy transfer and mass absorption coefficients for gamma rays with an incident energy range between 0.4 and 10 MeV in nitrogen, silicon, carbon, copper and sodium iodide. The mass absorption and mass energy transfer coefficients for gamma rays were calculated, and the results obtained were compared with the values reported in the literature.

Gurler, O. [Physics Department, Faculty of Arts and Sciences, Uludag University, Gorukle Campus, 16059 Bursa (Turkey)], E-mail: ogurler@uludag.edu.tr; Oz, H. [Physics Department, Faculty of Arts and Sciences, Uludag University, Gorukle Campus, 16059 Bursa (Turkey); Yalcin, S. [Education Faculty, Kastamonu University, 37200 Kastamonu (Turkey); Gundogdu, O. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); NCCPM, Medical Physics, Royal Surrey County Hospital, GU2 7XX (United Kingdom)

2009-01-15

388

Mass absorption and mass energy transfer coefficients for 0.4-10 MeV gamma rays in elemental solids and gases  

International Nuclear Information System (INIS)

[en] The mass energy absorption, the mass energy transfer and mass absorption coefficients have been widely used for problems and applications involving dose calculations. Direct measurements of the coefficients are difficult, and theoretical computations are usually employed. In this paper, analytical equations are presented for determining the mass energy transfer and mass absorption coefficients for gamma rays with an incident energy range between 0.4 and 10 MeV in nitrogen, silicon, carbon, copper and sodium iodide. The mass absorption and mass energy transfer coefficients for gamma rays were calculated, and the results obtained were compared with the values reported in the literature

2009-01-01

389

Augmentation of heat transfer coefficient by using 90{sup o} broken transverse ribs on absorber plate of solar air heater  

Energy Technology Data Exchange (ETDEWEB)

An experimental investigation has been carried out to study the heat transfer coefficient by using 90{sup o} broken transverse ribs on absorber plate of a solar air heater; the roughened wall being heated while the remaining three walls are insulated. The roughened wall has roughness with pitch (P), ranging from 10-30 mm, height of the rib of 1.5 mm and duct aspect ratio of 8. The air flow rate corresponds to Reynolds number between 3000-12,000. The heat transfer results have been compared with those for smooth ducts under similar flow and thermal boundary condition to determine the thermal efficiency of solar air heater. (author)

Sahu, M.M. [LNCT, Bhopal (India). Mechanical Engineering Dept.; Bhagoria, J.L. [MANIT, Bhopal (India). Mechanical Engineering Dept.

2005-10-01

390

A determination of the self-diffusion coefficient of the molybdenum surface  

International Nuclear Information System (INIS)

A recent study on the morphological evolution of a metal tip has shown that free evaporation must have a vital influence on the determination of the surface self-diffusion coefficients Dsub(S) in the high temperature region. A method is presented which enables the experimental determination of Dsub(S): (1) in the presence of an evaporation, and (2) in a relatively great region of temperature. As an example, Dsub(S) of molybdenum has been measured. (Auth.)

1976-01-01

391

The coefficient of friction between boron carbide (B4C) surfaces in air and ultrahigh vacuum (UHV)  

International Nuclear Information System (INIS)

Friction measurements between two contacting B4C surfaces in air and UHV at room temperature using 0.10-0.13N loads are reported. A pin (radius = 0.005m) on flat device allowing for interchange in UHV is used. The tribological surfaces can be examined using scanning Auger and XPS in the same UHV system. The coefficient of friction for air exposed surfaces is found to vary between air (0.20-0.25) and UHV (1.2-1.8). Stick-slip behavior, indicating strong adhesion, is observed in UHV while only a smooth friction value is measured in air. Air pressures 100Pa are necessary to reduce the friction from the high value in UHV. The friction between the clean surfaces in UHV initially is 0.8-1.3, but following mechanical conditioning at a higher velocity the friction drops to 0.17-0.25. In situ mechanical conditioning is necessary to obtain reproducible friction values for the clean surface. Exposing the clean surfaces to oxygen (10- 3Pa) while conditioning results in an increase in friction (1.0-1.2). Auger line scans through the scar made using the clean surfaces show enhanced B and reduced C. Similar Auger scans for oxygen exposed surfaces indicate that tearing of the oxide layer may be the reason for the high friction. The friction for a clean pin and an in situ nitrogen-implanted flat (10keV, saturation dose) is 0.70-0.80. Film transfer to the pin is observed

1988-12-02

392

The Computation And Analysis Of The Correction Factor Of Heat Transfer Coefficient For The Kartini Reactor S Heat Exchanger  

International Nuclear Information System (INIS)

[en] The computation and analysis of the heat transfer coefficient correction factor the shell and tube type of the Kartini reactor's heat exchanger (HE) has been carried out. The computation of the correction factor was done by measuring of the actual dimension of HE. As known that the shell and tube type of the Kartini reactor's has been opera-ted for more than 15 years. Due to the scraping and rusting occur at the buffle, the total heat transfer coefficient correction factor Ft was decrease. At the later computation, it is found that it's value is 0,4669 or differ of 0,1331 compared to the prediction standard value. So far, if the rusting and scraping of the secondary water coolant to the buffle is linear to the earlier HE's operation time, it is predicted that the function of the buffle will crisis approximately in the year of 2002/2003 or 7,5 years again

1996-01-01

393

Surface energy budget from a Titan GCM with realistic radiative transfer  

Science.gov (United States)

The existence of Titan's seasonal convective cloud activity, despite the atmosphere's huge thermal inertia, has been explained as resulting from variations in surface temperatures that drive cloud formation. General circulation models (GCMs) that produce significant summer precipitation have typically employed simplified radiative transfer that allows the summer polar surface to receive the maximum insolation, thus allowing vigorous convection to occur there. However, surface energetics from a GCM with nongray radiative transfer that uses optical properties derived from Cassini/Huygens data, and correlated k coefficients, indicate that this may not be entirely realistic. The surface energy budget in equilibrium is a balance between net surface radiation and turbulent surface fluxes of latent and sensible energy; because the maximum surface insolation oscillates seasonally between mid-latitudes, so too do the turbulent fluxes. Thus, the destabilizing influence of surface energy fluxes into the atmosphere with respect to convection is lower than previously suggested at the poles, but higher near midlatitudes. Methane is not available in infinite supply at the surface, and therefore sensible heat flux plays an equally important role as evaporation in balancing the surface radiative imbalance. The modeled moist static energy maximum also oscillates only between midlatitudes, in part because polar surface methane is limited as a source, boosting the possibility of midlatitude clouds. This may help to explain the observed persistence of southern mid-latitude clouds as the seasons change.

Lora, Juan M.; Russell, J.; Lunine, J.

2013-10-01

394

Alkali halide solutions under thermal gradients: soret coefficients and heat transfer mechanisms.  

UK PubMed Central (United Kingdom)

We report an extensive analysis of the non-equilibrium response of alkali halide aqueous solutions (Na(+)/K(+)-Cl(-)) to thermal gradients using state of the art non-equilibrium molecular dynamics simulations and thermal diffusion forced Rayleigh scattering experiments. The coupling between the thermal gradient and the resulting ionic salt mass flux is quantified through the Soret coefficient. We find the Soret coefficient is of the order of 10(-3) K(-1) for a wide range of concentrations. These relatively simple solutions feature a very rich behavior. The Soret coefficient decreases with concentration at high temperatures (higher than T ? 315 K), whereas it increases at lower temperatures. In agreement with previous experiments, we find evidence for sign inversion in the Soret coefficient of NaCl and KCl solutions. We use an atomistic non-equilibrium molecular dynamics approach to compute the Soret coefficients in a wide range of conditions and to attain further microscopic insight on the heat transport mechanism and the behavior of the Soret coefficient in aqueous solutions. The models employed in this work reproduce the magnitude of the Soret coefficient, and the general dependence of this coefficient with temperature and salt concentration. We use the computer simulations as a microscopic approach to establish a correlation between the sign and magnitude of the Soret coefficients and ionic solvation and hydrogen bond structure of the solutions. Finally, we report an analysis of heat transport in ionic solution by quantifying the solution thermal conductivity as a function of concentration. The simulations accurately reproduce the decrease of the thermal conductivity with increasing salt concentration that is observed in experiments. An explanation of this behavior is provided.

Römer F; Wang Z; Wiegand S; Bresme F

2013-07-01

395

Alkali halide solutions under thermal gradients: soret coefficients and heat transfer mechanisms.  

Science.gov (United States)

We report an extensive analysis of the non-equilibrium response of alkali halide aqueous solutions (Na(+)/K(+)-Cl(-)) to thermal gradients using state of the art non-equilibrium molecular dynamics simulations and thermal diffusion forced Rayleigh scattering experiments. The coupling between the thermal gradient and the resulting ionic salt mass flux is quantified through the Soret coefficient. We find the Soret coefficient is of the order of 10(-3) K(-1) for a wide range of concentrations. These relatively simple solutions feature a very rich behavior. The Soret coefficient decreases with concentration at high temperatures (higher than T ? 315 K), whereas it increases at lower temperatures. In agreement with previous experiments, we find evidence for sign inversion in the Soret coefficient of NaCl and KCl solutions. We use an atomistic non-equilibrium molecular dynamics approach to compute the Soret coefficients in a wide range of conditions and to attain further microscopic insight on the heat transport mechanism and the behavior of the Soret coefficient in aqueous solutions. The models employed in this work reproduce the magnitude of the Soret coefficient, and the general dependence of this coefficient with temperature and salt concentration. We use the computer simulations as a microscopic approach to establish a correlation between the sign and magnitude of the Soret coefficients and ionic solvation and hydrogen bond structure of the solutions. Finally, we report an analysis of heat transport in ionic solution by quantifying the solution thermal conductivity as a function of concentration. The simulations accurately reproduce the decrease of the thermal conductivity with increasing salt concentration that is observed in experiments. An explanation of this behavior is provided. PMID:23758489

Römer, Frank; Wang, Zilin; Wiegand, Simone; Bresme, Fernando

2013-06-26

396

Reconstruction of the heat transfer coefficient in the problem of binary alloy solidification with application of the broken line model  

Directory of Open Access Journals (Sweden)

Full Text Available In the paper, solution of the inverse problem is presented, which consists in determination of the heat transfer coefficient during the process of binary alloy solidification for the known temperature measurements in the selected points of the cast. In the considered model distribution of temperature is described with the aid of Stefan problem with the varying liquidus temperature depending on the concentration of alloy component. Whereas, for description of the concentration the broken line model is used.

D. S?ota; E. Hetmaniok; R. Witu?a

2011-01-01

397

Prediction of convective heat transfer coefficients and their effects on distortion and mechanical properties of cylinder steel bodies quenched by gas cooling  

Energy Technology Data Exchange (ETDEWEB)

The primary objectives of this study are to model the nature of the complex high-turbulence quenching cooling-gas flow, and to examine its effects on the resulting distortions and mechanical properties of the quenched piece, here bearing steel tubes and solid cylinders. A {kappa}-{epsilon} turbulent flow and heat transfer model adopted was found to predict the convective heat transfer coefficient (h) distribution reasonably well for Reynolds number up to about (0.3)10{sup 6}. At higher Reynolds number (to 10{sup 6}) it still predicts the nature of the flow well, but overpredicts h by up to 100% in the transition zone. The distributions of h around the body surface were used as the boundary condition for computing the temperature distribution history, phase transformations, distortions and mechanical properties of the quenched bodies. Increasing variation in h was found to increase the probability of large out-of-roundness, and nonuniformity in the properties.

Thuvander, A.; Melander, A.; Lind, M.; Lior, N.; Bark, F.H.

1999-07-01

398

Temperature, surface roughness and anisotropy effects on the tangential momentum accomodation coefficient between Pt(100) AND Ar  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, we study the influence of Platinum (100) surface morphology on the Tangential Momentum Accommodation Coefficient (TMAC) with Argon usingMolecular Dynamics method (MD). The coefficient is computed directly by beaming Ar atoms into the surfaces and measuring the relative momentum change...

Tung Pham, T.; To, Q. D.; Lauriat, G.; Léonard, C.; Vo, V. H.