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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

Modeling Local Hygrothermal Interaction: Local surface transfer coefficients  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Steskens, Paul Wilhelmus Maria Hermanus; Janssen, Hans; Rode, Carsten

2009-01-01

3

Proposed method for measuring local heat transfer coefficients of isothermal surfaces  

Energy Technology Data Exchange (ETDEWEB)

A method has been proposed for measuring local heat transfer coefficients. The method uses the change of a wet surface temperature by radiation heating and can be applied to isothermal conditions and with large variations of the local heat transfer coefficients along the surface of a body. The present method is based on the heat balance equation, which expresses a simple relationship between humidity and wet-bulb temperatures. An experiment was devised to measure the local heat transfer coefficient along a flat plate. The results confirmed the effectiveness of the present method to measure local and overall heat and mass transfer coefficients with reasonable accuracy.

Kumada, T. (Hokkaido Univ., Sapporo (Japan))

1989-11-01

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

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

Science.gov (United States)

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. PMID:19019110

Simpson, R; Abakarov, A; Almonacid, S; Teixeira, A

2008-10-01

7

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

8

The Effects of Surface Roughness and Metal Temperature on the Heat-Transfer Coefficient at the Metal Mold Interface  

Science.gov (United States)

This article focused on the effects of surface roughness and temperature on the heat-transfer coefficient at the metal mold interface. The experimental work was carried out in a unique and versatile apparatus, which was instrumented with two types of sensors, thermocouples, and linear variable differential transformers (LVDTs). The monitoring of the two types of sensors was carried out simultaneously during solidification. The concurrent use of two independent sensors provided mutually supportive data, thereby strengthening the validity of the interpretations that were made. With this type of instrumentation, it was possible to measure temperature profiles in mold and casting, as well as the air gap at the metal mold interface. Commercial purity aluminum was cast against steel and high carbon iron molds. Each type of mold had a unique surface roughness value. Inverse heat-transfer analysis was used to estimate the heat-transfer coefficient and the heat flux at the metal mold interface. A significant drop in the heat-transfer coefficient was registered, which coincided with the time period of the air gap formation, detected by the LVDT. An equation of the form h = frac{1} {{b^{ast}A + c}} + d was found to provide excellent correlation between the heat-transfer coefficient and air gap size. In general, an increase in mold surface roughness results in a decrease in the heat-transfer coefficient at the metal mold interface. On the other hand, a rise in liquid metal temperature results in a higher heat-transfer coefficient.

Coates, Basil; Argyropoulos, Stavros A.

2007-04-01

9

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

2013-06-01

10

Transfer Coefficients of Momentum, Heat and Water Vapour in the Atmospheric Surface Layer of a Large Freshwater Lake  

Science.gov (United States)

In studies of lake-atmosphere interactions, the fluxes of momentum, water vapour and sensible heat are often parametrized as being proportional to the differences in wind, humidity and air temperature between the water surface and a reference height above the surface. Here, the proportionality via transfer coefficients in these relationships was investigated with the eddy-covariance method at three sites within an eddy-covariance mesonet across Lake Taihu, China. The results indicate that the transfer coefficients decreased with increasing wind speed for weak winds and approached constant values for strong winds. The presence of submerged macrophytes reduced the momentum transfer (drag) coefficient significantly. At the two sites free of submerged macrophytes, the 10-m drag coefficients under neutral stability were 1.8 and at the wind speed of , which are 38 and 34 % greater than the prediction by the Garratt model for the marine environment.

Xiao, Wei; Liu, Shoudong; Wang, Wei; Yang, Dong; Xu, Jiaping; Cao, Chang; Li, Hanchao; Lee, Xuhui

2013-09-01

11

Convective heat transfer coefficients for exterior building surfaces: Existing correlations and CFD modelling  

International Nuclear Information System (INIS)

Convective heat transfer at exterior building surfaces has an impact on the design and performance of building components such as double-skin facades, solar collectors, solar chimneys and ventilated photovoltaic arrays, and also affects the thermal climate and cooling load in urban areas. In this study, an overview is given of existing correlations of the exterior convective heat transfer coefficient (CHTC) with the wind speed, indicating significant differences between these correlations. As an alternative to using existing correlations, the applicability of CFD to obtain forced CHTC correlations is evaluated, by considering a cubic building in an atmospheric boundary layer. Steady Reynolds-averaged Navier-Stokes simulations are performed and, instead of the commonly used wall functions, low-Reynolds number modelling (LRNM) is used to model the boundary-layer region for reasons of improved accuracy. The flow field is found to become quasi independent of the Reynolds number at Reynolds numbers of about 105. This allows limiting the wind speed at which the CHTC is evaluated and thus the grid resolution in the near-wall region, which significantly reduces the computational expense. The distribution of the power-law CHTC-U10 correlation over the windward and leeward surfaces is presented (U10 = reference wind speed at 10 m height). It is shown that these correlations can be accurately determined by simulations with relatively low wind speed values, which avoids the use of excessively fine grids for LRNM, and by using only two or three discrete wind speed values, which limits the required number of CFD simulations.

2011-01-01

12

An experimental determination of the H2S overall mass transfer coefficient from quiescent surfaces at wastewater treatment plants  

Science.gov (United States)

This study has investigated overall mass transfer coefficients of hydrogen sulphide from quiescent liquid surfaces under simulated laboratory conditions. Wind flow (friction velocity) has been correlated with the overall mass transfer coefficient (KL) of hydrogen sulphide in the liquid phase using a wind tunnel study. The experimental values for this coefficient have been compared with predicted KL values obtained from three different emission models that are widely used to determine volatilization rates from the quiescent surfaces of wastewater treatment unit processes. Friction velocity (in a range of 0.11 and 0.27 m s-1) was found to have a negligible influence on the overall mass transfer coefficients for hydrogen sulphide but by contrast two of the models predicted a stronger influence of friction velocity and overestimate the KL values by up to a factor of 12.5, thus risking unnecessary expenditure on odour control measures. However, at low wind speeds or friction velocities, when more odour complaints might be expected due to poor atmospheric dispersion, a better agreement of emission rates with experimental data was found for all the models.

Santos, Jane Meri; Kreim, Virginie; Guillot, Jean-Michel; Reis, Neyval Costa; de Sá, Leandro Melo; Horan, Nigel John

2012-12-01

13

CFD simulation of direct contact condensation with ANSYS CFX using surface renewal theory based heat transfer coefficients  

Energy Technology Data Exchange (ETDEWEB)

Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)

Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering

2013-07-01

14

CFD simulation of direct contact condensation with ANSYS CFX using surface renewal theory based heat transfer coefficients  

International Nuclear Information System (INIS)

Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)

2013-05-14

15

Surface heat transfer coefficients for refrigeration and freezing of foods immersed in an ice slurry  

Energy Technology Data Exchange (ETDEWEB)

Ice slurries are mixtures of microcrystals of ice in aqueous solutions that do not freeze under the operating conditions used. One potential application of ice slurries in the food industry is the chilling and freezing of foods using direct contact. The latent heat of melting of the ice makes it possible to improve the superficial coefficients of exchange with respect to those obtained using conventional single-phase fluids. In this study, the authors compared the coefficients obtained using immersion in a copper cylinder (l=0.03m, D=0.02m) in various single-phase media (brines) with those obtained using ice slurries. They also analysed the influence of the ice mass fraction, stirring, the evolution of coefficients over time, and the relationships between dimensionless numbers (Nu, Re and Pr). les nombres adimensionnels Nu, Re et Pr. (author)

Torres-de Maria, Gonzalo; Abril, Jose; Casp, Ana [Tecnologia de Alimentos. Escuela Tecnica Superior de Ingenieros Agronomos, Universidad Publica de Navarra. Campus Arrosadia s/n, E-31006, Pamplona (Espana)

2005-11-01

16

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

Energy Technology Data Exchange (ETDEWEB)

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.

Hodge, S.A.; Sanders, J.P.; Klein, D.E.

1979-11-01

17

Influence of wall emissivity and convective heat transfer coefficient on the adiabatic surface temperature as thermal/structural parameter in fire modeling  

International Nuclear Information System (INIS)

In fire engineering analysis, one of the open problem is the transfer of thermal parameters obtained by fire CFD model to FEM models for structural analysis. In this study the new useful concept of “Adiabatic Surface Temperature” or more commonly known as AST, introduced by Wickström, is investigated. The adiabatic surface temperature offers the opportunity to transfer both thermal information of the gas and the net heat flux to the solid phase model, obtained by CFD analysis. In this study two CFD analyses are carried out in order to evaluate the effect of emissivity and of convective heat transfer coefficient to determine the AST. First one CFD analysis simulating a fire scenario, “conjugate heat transfer”, with a square steel beam exposed to hot surface is carried out to calculate AST, heat convective coefficient and temperature field in the beam. Second one, a conductive analysis is carried out on “standalone beam” imposing a third type boundary condition on its boundaries assuming the AST, evaluated in the conjugate analysis, as external temperature. Different heat convective coefficients are imposed on the beam walls. The comparison between results obtained by means of the two proposed analyses shows the use of AST as transfer thermal parameter between CFD (Computational Fluid Dynamic) and FEM (Finite Element Method) models is appropriate when the convective heat transfer coefficient is properly evaluated. -- Highlights: ? An open problem is to transfer parameters obtained by thermal to structural models. ? The useful concept of “Adiabatic Surface Temperature” (AST) is investigated. ? The AST use is right for properly evaluated convective heat transfer coefficient

2013-03-01

18

Quantification of surface area and intrinsic mass transfer coefficient for ultrasound-assisted dissolution process of a sparingly soluble solid dispersed in aqueous solutions.  

Science.gov (United States)

The efficacy of power ultrasound of 20 kHz in enhancing the volumetric mass transfer coefficient was investigated in this study. Breakage and dissolution of sparingly soluble benzoic acid dispersed in either water or 24% aqueous glycerol was monitored as a function of time and ultrasound power input. Particle size measurements were carried out at intermediate times during the experiment to estimate the mean particle size and surface area. Linear combination of lognormal distributions was found to fit the experimental particle size distribution data. The De Brouckere mean diameters (d(43)) obtained from the particle size distributions decreased with increase in the ultrasonic power level. Empirical correlations were developed for the evolution of surface area as a function of ultrasonic energy input per unit mass. The effect of ultrasound on the intrinsic mass transfer coefficient (k(c)) could be decoupled from the volumetric mass transfer coefficient (k(c)a) as the surface area was also estimated. Different approaches involving either constant or variable intrinsic mass transfer coefficients were employed when carrying out the delineation. Mass transfer rates were enhanced due to both higher ultrasound induced intrinsic convective mass transfer coefficient and additional surface area created from particle breakage. To delineate the effects of particle breakage from solid dissolution, experiments were also carried out under non-mass transfer conditions by pre-saturating the solvents with benzoic acid. Both the solid-liquid systems examined in the present study attained saturation concentration when the ultrasonic energy input per unit mass was approximately 60 kJ/kg, irrespective of the ultrasonic power level setting. PMID:22019317

Durbha, Krishna Sandilya; Aravamudan, Kannan

2012-05-01

19

Measurement of heat (mass) transfer coefficient on the blade surfaces of a linear turbine rotor cascade with a four-axis naphthalene profile measuring system  

International Nuclear Information System (INIS)

The heat (mass) transfer characteristics on the blade surface of a first-stage turbine rotor cascade for power generation has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is successfully developed for the measurements of the local heat (mass) transfer coefficient on the curved blade surface. The experiment is carried out at the free-stream Reynolds number and turbulence intensity of 2.09x105 and 1.2%. The results on the blade surfaces show that the local heat (mass) transfer on the suction surface is strongly influenced by the endwall vortices, but that on the pressure surface shows a nearly two-dimensional nature. The pressure surface has a more uniform distribution of heat load than the suction one

2001-11-01

20

Generalized (semi)-empirical formulae for optimal sterilization temperatures of conduction-heated foods with infinite surface heat transfer coefficients  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A computer program was developed to model heat sterilization of one-dimensional conduction-heated foods with negligible surface resistance to heat transfer. The optimal sterilization temperature, defined as the processing temperature that results in a food product with minimum surface cook-value after achieving the desired degree of sterility, was calculated as a function of food properties (thermal diffusivity, Z-value of the quality factor), processing conditions (dimensions and geometry...

Hendrickx, M.; Silva, C.; Oliveira, F.; Tobback, P.

1993-01-01

 
 
 
 
21

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

22

Transfer of risk coefficients across populations  

Energy Technology Data Exchange (ETDEWEB)

The variation of lifetime risk projections for a Canadian population caused by the uncertainty in the choice of method for transferring excess relative risk coefficients between populations is assessed. Site-specific projections, varied by factors up to 3.5 when excess risk coefficients of the BEIR V relative risk models were transferred to the Canadian population using an additive and multiplicative method. When the risk from all cancers are combined, differences between transfer methods were no longer significant. The Canadian projections were consistent with the ICRP-60 nominal fatal cancer risk estimates. (author)

Rasmussen, L.R. [Atomic Energy of Canada Limited, Pinawa, Manitoba (Canada)

1992-07-01

23

Interphase mass transfer coefficient for uranium extraction  

International Nuclear Information System (INIS)

The interphase mass transfer for extraction of uranium from an aqueous sulfuric acid solution, using AMSCO 140 kerosene containing DEHPA (di-2-ethylhexylphosphoric acid)-TOPO (tri-n-octylphosphine oxide) as a complexing extraction agent is examined. The system represents a case of extraction with an equilibrium chemical reaction in the organic phase. The experimental studies were made in both a continuous flow stirred tank reactor (CFSTR) and an annular flow jet reactor (AFJR). The interphase mass transfer coefficient was found to be a function of power input per unit volume for each type of reactor. For the same power input, the AFJR gives a higher mass transfer coefficient than a CFSTR

1979-01-01

24

Determination of the heat transfer coefficients in transient heat conduction  

International Nuclear Information System (INIS)

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. (paper)

2013-09-01

25

Transfer coefficients in elliptical tubes and plate fin heat exchangers  

International Nuclear Information System (INIS)

Mean transfer coefficients in elliptical tubes and plate fin heat exchangers were determined by application of heat and mass transfer analogy in conjunction with the naphthalene sublimation technique. The transfer coefficients are presented in a dimensionless form as functions of the Reynolds number. By using the least squares method analytical expressions for the transfer coefficients were determined with low scattering. (E.G.)

1979-01-01

26

Heat transfer coefficients during quenching of steels  

Science.gov (United States)

Heat transfer coefficients for quenching in water have been measured as a function of temperature using steel probes for a variety of iron alloys. The coefficients were derived from measured cooling curves combined with calculated heat-capacities. The resulting data were then used to calculate cooling curves using the finite volume method for a large steel sample and these curves have been demonstrated to be consistent with measured values for the large sample. Furthermore, by combining the estimated cooling curves with time-temperature-transformation (TTT) diagrams it has been possible to predict the variation of hardness as a function of distance via the quench factor analysis. The work should prove useful in the heat treatment of the steels studied, some of which are in the development stage.

Hasan, H. S.; Peet, M. J.; Jalil, J. M.; Bhadeshia, H. K. D. H.

2011-03-01

27

Heat transfer coefficient between UO2 and Zircaloy-2  

International Nuclear Information System (INIS)

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

28

Hydrocarbon heat transfer coefficients: preliminary isobutane results  

Energy Technology Data Exchange (ETDEWEB)

Research designed to obtain baseline heat transfer data on secondary fluid candidates for geothermal cycle systems is described. The apparatus was designed to provide baseline data under clean conditions to determine inside and outside heat transfer film coefficient, respectivly, for heating and condensation of secondary fluids being considered for binary systems. The secondary fluid loop simulates the binary cycle with steam, instead of geothermal fluid, as the heating fluid and a throttling valve instead of the turbine. Results on film coefficient for condensing the isobutane on the outside of a tube at various pressures and condensate loading, as well as preliminary results on flm coefficient for heating the isobutane inside a tube at 4.14 MPa (600 psia) and various flow rates, are presented. The isobutane was heated in a horizontal, type 316 stainless steel, instrumented tube by steam condensing on the outside. In the condenser, the isobutane was condensed on the outside of a horizontal tube, idential to that in the heater, by cooling water inside the tube. Each instrumented tube was fitted with a total of fifteen thermocouples imbedded in the wall of the tube at five stations located equally along the length of the tube. The inside and outside wall temperature of the tube at each of the five stations was calculated from the location of the imbedded thermocouples and their temperatures. The heat rate to the isobutane in the heater was determined by measuring the rate of condensing steam on the outside of the tube under eachof four sections by means of specially designed vapor-traced meters. The heat rate released by the condensing isobutane was also determined by measuring the rate of isobutane condensing on the outside of the tube with meters similar to those in the heater.

Tleimat, B.W.; Laird, A.D.K.; Rie, H.; Hsu, I.C.; Seban, R.A.

1979-02-01

29

Measurement of airfoil heat transfer coefficients on a turbine stage  

Science.gov (United States)

A combined experimental and analytical program was conducted to examine the impact of a number of variables on the midspan heat transfer coefficients of the three airfoil rows in a one and one-half stage large scale turbine model. Variables included stator/rotor axial spacing, Reynolds number, turbine inlet turbulence, flow coefficient, relevant stator 1/stator 2 circumferential position, and rotation. Heat transfer data were acquired on the suction and pressure surfaces of the three airfoils. High density data were also acquired in the leading edge stagnation regions. Extensive documentation of the steady and unsteady aerodynamics was acquired. Finally, heat transfer data were compared with both a steady and an unsteady boundary layer analysis.

Dring, Robert P.; Blair, Michael F.; Joslyn, H. David

1987-01-01

30

Radionuclide transfer to animal products: revised recommended transfer coefficient values  

Energy Technology Data Exchange (ETDEWEB)

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.

Howard, B.J. [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LAI 4AP (United Kingdom)], E-mail: bjho@ceh.ac.uk; Beresford, N.A.; Barnett, C.L. [Centre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LAI 4AP (United Kingdom); Fesenko, S. [International Atomic Energy Agency, 1400 Vienna (Austria)

2009-03-15

31

Condensation heat transfer coefficients of flammable refrigerants  

Energy Technology Data Exchange (ETDEWEB)

In this study, external condensation heat transfer coefficients (HTCs) of six flammable refrigerants of propylene (R1270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of 39 {sup o}C on a plain tube of 19.0 mm outside diameter with a wall subcooling of 3-8 {sup o}C under a heat flux of 7-23 kW m{sup -2}. Test results showed a typical trend that external condensation HTCs decrease with the wall subcooling. No unusual behavior or phenomenon was observed for these flammable refrigerants during experiments. HFC32 and DME showed 28-44% higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene and butane showed the similar HTCs as those of HCFC22 while propane and isobutane showed 9% lower HTCs than those of HCFC22. Finally, a general correlation was made by modifying Nusselt's equation based upon the measured data of eleven fluids of various vapor pressures including halogenated refrigerants. The general equation showed an excellent agreement with all data exhibiting a deviation of less than 3%. (author)

Dongsoo Jung; Soonam Chae; Dongsoo Bae [Inha University, Incheon (Korea). Department of Mechanical Engineering; Sukjae Oho [TechnoChem Co. Ltd., Kyunggi-Do (Korea)

2004-05-01

32

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

International Nuclear Information System (INIS)

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.)

1982-12-12

33

Analysis of the heat transfer coefficient during potato frying  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this work was to study the dependence of the heat transfer coefficient (h) on the water loss rate of potato during frying. An indirect method was used where a metal piece with the same geometry of the potato pieces was placed on top of various potato samples at different frying times, and its temperature was recorded for 20–30 s. Another method consisted of direct recording of the temperature within a potato slice, close to the surface. Water loss rate was estimated by imag...

Costa, Rui M.; Oliveira, Fernanda A. R.; Delaneya, Olivia; Gekas, Vassilis

2001-01-01

34

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

International Nuclear Information System (INIS)

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

35

Local heat transfer coefficient for turbulent flow in rod bundles  

International Nuclear Information System (INIS)

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< Pr<0.2). Results of temperature and velocity fields distribution of slip coefficients and local heat transfer coefficients are obtained. (E.G.)

1983-01-01

36

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.

S.S. Kang

2007-01-01

37

Soil to plant transfer coefficients at three different Czechoslovak sites  

International Nuclear Information System (INIS)

Soil and plant samples were sampled for the determination of soil to plant transfer coefficients at three different Czechoslovak reactor sites. The lowest transfer factors for cereals and fodder were determined at the site of Eastern Slovakia. Values of transfer factors depend on soil type, cation exchange capacity, and total sorption capacity of the soils. (author)

1989-01-01

38

Estimation of Volumetric Mass Transfer Coefficient in Bioreactor  

Directory of Open Access Journals (Sweden)

Full Text Available This study is concentrated to investigate the effects of aeration and stirring speed on the volumetric mass transfer coefficient (KLa. A dynamic technique was used in estimating KLa values in order to achieve the aim of this study.This study was done in 10L bioreactor by using two medias:-1. Dionized water2. Xanthan solution (1 g /LMoreover, the research covered a comparison between the obtained values of KLa.The Xanthan solution was used because of its higher viscosity in comparison with water. It behaves similarly to the cultivation medium when organisms are cultivated in a bioreactor. Growth of organisms in the reactor leads to a change in the viscosity of the medium which affects the mass transfer.Two variables, the effect of air flow rate (3-20 L/min and the effect of stirring speed (250-700rpm on KLa value were studied. Other parameters such as temperature, liquid volume, and stirrer shape and stirrer position were held constant; the results demonstrated an increase in KLa ? value and mass transfer with increasing stirrer speed. Thus at higher speed, better dispersion of the bubbles was obtained. Therefore, that increased the surface / volume ratio which increased the mass transfer area i.e. KLa value.

Zainab Yaquob Atiya

2012-01-01

39

A New Global Potential Energy Surface for the Hydroperoxyl Radical, HO2: Reaction Coefficients for H + O2 and Vibrational Splittings for H Atom Transfer  

Science.gov (United States)

A new analytic global potential energy surface describing the hydroperoxyl radical system H((sup 2)S) + O2(X (sup 3)Sigma((sup -)(sub g))) (reversible reaction) HO2 ((X-tilde) (sup 2)A'') (reversible reaction) O((sup 3)P) + O H (X (sup 2)Pi) has been fitted using the ab initio complete active space SCF (self-consistent-field)/externally contracted configuration interaction (CASSCF/CCI) energy calculations of Walch and Duchovic. Results of quasiclassical trajectory studies to determine the rate coefficients of the forward and reverse reactions at combustion temperatures will be presented. In addition, vibrational energy levels were calculated using the quantum DVR-DGB (discrete variable representation-distributed Gaussian basis) method and the splitting due to H atom migration is investigated. The material of the proposed presentation was reviewed and the technical content will not reveal any information not already in the public domain and will not give any foreign industry or government a competitive advantage.

Dateo, Christopher E.; Arnold, James O. (Technical Monitor)

1994-01-01

40

Rate Coefficient Determination in Charge Transfer Reactions  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

2002-01-01

 
 
 
 
41

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.

Nathalie Vaeck

2002-03-01

42

Convection coefficient equations for forced air flow over flat surfaces  

Energy Technology Data Exchange (ETDEWEB)

In this paper, various comparisons among well-known equations of the convection heat transfer coefficient for forced air flow over flat surfaces and particularly over flat plate solar collectors, with the aim at arriving at a consensus on which of such equations is more accurate are carried out. Through the application of basic principles, various accuracies, inaccuracies and validations of the considered equations have been found and shown, and a consensus reached. Such consensual equation, which comes from the boundary layer theory and takes into account the determining laminar and turbulent flows as well as the wind direction and the decay of the convection coefficient over the surface, also showed close agreement with different experimental works and tends to represent more accurately the actual heat transfer from/to any flat surface submitted to forced convection. (author)

Sartori, Ernani [Universidade Federal da Paraiba, Av. Silvino Lopes 425/404, 58039-190 Joao Pessoa PB (Brazil)

2006-09-15

43

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

44

Determination of the surface drag coefficient  

DEFF Research Database (Denmark)

This study examines the dependence of the surface drag coefficient on stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable conditions, the drag coefficient does not depend systematically on z/L but decreases with wind speed for fixed intervals of z/L, where L is the Obukhov length. Even though the drag coefficient for weak wind conditions is sensitive to the exact method of calculation and choice of averaging time, the decrease of the drag coefficient with wind speed occurs for all of the calculation methods. A classification of flux calculation methods is constructed, which unifies the most common previous approaches. The roughness length corresponding to the usual Monin-Obukhov stability functions decreases with increasing wind speed. This dependence on wind speed cannot be eliminated by adjusting the stability functions. If physical, the decrease of the roughness length with increasing wind speed might be due to the decreasing role of viscous effects and streamlining of the vegetation, although these effects cannot be isolated from existing atmospheric data. For weak winds, both the mean flow and the stress vector often meander significantly in response to mesoscale motions. The relationship between meandering of the stress and wind vectors is examined. For weak winds, the drag coefficient can be sensitive to the method of calculation, partly due to meandering of the stress vector.

Jensen, N.O.; Ejsing Jørgensen, Hans

2001-01-01

45

Evaluation of heat transfer and drag coefficients for iron meteorites  

International Nuclear Information System (INIS)

According to the observed deceleration of 15 superschmidt meteors generated by iron meteoroids of heat transfer coefficients ? and drag coefficients ? were evaluated assuming the quasi-continuous fragmentation. It is shown that for meteoroid initial masses M1 g ? strongly decreases by M increase reaching values ? ? 0,1 at M ? 10 g. The square dependence of the reactive part of drag coefficient on the velocity instead of linear lows is obtained

1988-01-01

46

A method of measuring local heat and mass transfer coefficients based on the wet-bulb temperature  

Energy Technology Data Exchange (ETDEWEB)

A new technique for measuring convective heat and mass transfer coefficients using the analogy between heat and mass transfer is presented. The method only requires measurements of free stream and surface temperatures and an imposed heat flux. Comparisons one made between heat transfer coefficients measured by this technique and those reported in the literature for similar convective situations.

Kumada, T.

1986-03-01

47

A method of measuring local heat and mass transfer coefficients based on the wet-bulb temperature  

International Nuclear Information System (INIS)

A new technique for measuring convective heat and mass transfer coefficients using the analogy between heat and mass transfer is presented. The method only requires measurements of free stream and surface temperatures and an imposed heat flux. Comparisons one made between heat transfer coefficients measured by this technique and those reported in the literature for similar convective situations

1986-01-01

48

Heat transfer coefficient in serpentine coolant passage for CCDTL  

International Nuclear Information System (INIS)

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

1998-08-23

49

Mass transfer at vertically oscillating surfaces  

Energy Technology Data Exchange (ETDEWEB)

An analysis of mass transfer at vertically oscillating surfaces is presented. It takes into account the interaction between forced and natural convection and can be used under conditions where the fluid velocity outside the boundary layer changes direction. Because of the good agreement with experimental data, the model can explain the multi-fold increase in mass transfer coefficient obtained under oscillatory conditions. 8 refs., 3 figs.

Gomaa, H.G. [Ontario Hydro Nuclear, Tiverton, Ontario (Canada); Landau, J. [Univ. of New Brunswick, Fredericton, NB (Canada); Tawell, A.M.A. [Technical Univ. of Nova Scotia, Halifax, NS (Canada)

1996-12-31

50

Description, calibration, and preliminary testing of the coal liquefaction heat transfer coefficient measurement test unit  

Energy Technology Data Exchange (ETDEWEB)

The efficiency of energy utilization within coal-liquefaction process is of major significance to the commercialization of the process. Heat exchange equipment is also one of the major economic investments in new plants. Consequently, reliable heat transfer data are required for the economical design of heat exchange equipment. Since accurate heat transfer coefficients of coal slurries, especially with a gas phase present, cannot be accurately calculated from known physical data for the operational conditions found in the coal-liquefaction process, experimentally determined heat transfer coefficients under actual process conditions are needed. A liquefaction heat-transfer-coefficient measurement test unit for a nominal one-half-ton-per-day coal slurry was constructed, calibrated, and operated at ANL. This test unit was built to determine heat transfer coefficients needed for design of feed-heat and effluent-heat exchangers used in coal-liquefaction processes. The heat-transfer test module was substituted for the preheater and reactor used in the normal coal-liquefaction process. The heat transfer coefficient can be evaluated for the heat transfer between the three-phase feed and effluent fluids in turbulent flow and a heated or cooled stainless steel surface. A description is presented of the unit and its capabilities, calibration procedures and results, and preliminary operation and data analysis. Recommendations are made that should improve accuracy and ease of operation and data analysis of the test unit.

Mulcahey, T.P.; Lo, R.N.K.; Bump, T.R.; Mulcahey, M.E.; Fischer, J.; Cannon, T.F.; Brock, R.E.; Wilson, W.I.; Bowyer, D.

1979-06-01

51

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

52

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

53

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

54

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

International Nuclear Information System (INIS)

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)

2013-06-01

55

Investigation of correlation diagram between heat transfer coefficient and void fraction under sodium-water reaction  

International Nuclear Information System (INIS)

Sodium-water reaction (SWR) in a steam generator of sodium-cooled fast reactor (SFR) is a significant phenomenon for safety assessment of the system. One of the top concerns in the SWR is an overheating rupture phenomenon in which a neighbor heat transfer tube fails instantaneously because of a deterioration of structural integrity under a high temperature condition. Hence, the heat transfer coefficient on the tube surface is of importance. Since hydrogen gas is generated in the SWR and liquid water will evaporate quickly due to depressurization, the reaction region is covered with a multi-phase flow structure, and thus the value of the heat transfer coefficient will vary widely. In the present paper, a correlation diagram has been developed between the heat transfer coefficient and the void fraction based on one dimensional homogeneous flow simulation. Furthermore, the transient of void fraction in SWAT-1R experiment is investigated using the diagram. (author)

2012-01-01

56

Overall heat transfer coefficient in the presence of the axial dispersion coefficient for a forced draught cooling tower  

Energy Technology Data Exchange (ETDEWEB)

An overall heat transfer coefficient was calculated for a forced draught counterflow cooling tower by using the pulse response technique. The presence of an axial dispersion coefficient for both gas and liquid was considered. Results indicate that, on neglecting the axial mixing and assuming a plug flow, the overall heat transfer coefficient is overestimated and can lead to errors in design applications. (author).

Younis, M.A. (Kuwait Univ. (Kuwait))

57

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

2010-06-01

58

Coefficients determination of differential state equations from Laplace transfer function  

Energy Technology Data Exchange (ETDEWEB)

In control theory, the characteristics of a system are generally described or defined by Laplace transfer function. However, the state variable differential equations are generally used in the actual system simulation on hybrid computer or general digital computer. In this way, the differential equations are integrated to get the result. So, the first thing in system simulation is to translate the Laplace transfer function into the state variable differential equations. The primary object of this article is to develop a computer program to do this job as well as scale the coefficient of each state variable through interactive communication with computer on a terminal.

Wang, C.Y.

1983-04-01

59

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

60

Measurement and modeling of interface heat transfer coefficients  

International Nuclear Information System (INIS)

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/m"2/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

1986-01-12

 
 
 
 
61

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

International Nuclear Information System (INIS)

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

62

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

63

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

International Nuclear Information System (INIS)

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

1994-11-01

64

Heat transfer coefficients for forced-air cooling and freezing of selected foods  

Energy Technology Data Exchange (ETDEWEB)

To maximize the efficiency of cooling and freezing operations for foods, it is necessary to optimally design the refrigeration equipment to fit the specific requirements of the particular cooling or freezing application. The design of food refrigeration equipment requires estimation of the cooling and freezing times of foods, as well as the corresponding refrigeration loads. The accuracy of these estimates, in turn, depends upon accurate estimates of the surface heat transfer coefficient for the cooling or freezing operation. This project reviewed heat transfer data for the cooling and/or freezing of foods. A total of 777 cooling curves for 295 food items were obtained from an industrial survey and a unique iterative algorithm, utilizing the concept of 'equivalent heat transfer dimensionality', was developed to obtain heat transfer coefficients from these cooling curves. Nine Nusselt-Reynolds-Prandtl correlations were developed from a selection of the 777 heat transfer coefficients resulting from this algorithm, as well as 144 heat transfer coefficients for 13 food items, collected from the literature. The data and correlations resulting from this project will be used by designers of cooling and freezing systems for foods. This information will make possible a more accurate determination of cooling and freezing times and corresponding refrigeration loads. Such information is important in the design and operation of cooling and freezing facilities and will be of immediate usefulness to engineers involved in the design and operation of such systems. (author)

Becker, B.R.; Fricke, B.A. [University of Missouri, Kansas City, MO (United States). Mechanical Engineering Dept.

2004-08-01

65

Water mist effect on heat transfer coefficient in cooling of casting die  

Directory of Open Access Journals (Sweden)

Full Text Available This project is showing investigation results of heat transfer process between cast iron die and environment during cooling of die in the temperature range 600÷100 C with compressed air, spray water and water mist streamed under pressure 0.35 0.45 MPa in air jet0.3 0.4 MPa .At the paper are shown results of cooling die’s flat wall using open cooling system. The temperature gradient was presented at die’s wallthickness and calculated thermal curve for cooling surface. The calculation results of heat transfer coefficient ? were presented between die and researched cooling factors and also mathematical models of ? coefficient depending on surface temperature. Revealed that coefficient ? has the biggest value’s range for die cooling with water mist under pressure 0.3/0.35 MPa.

R. W?adysiak

2008-10-01

66

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.

Vijay R. Raghavan

2011-01-01

67

Transfer coefficients of radionuclides secreted in milk of dairy cows  

International Nuclear Information System (INIS)

This study simulated experimentally the transfer of radionuclides to milk of dairy cows on a worst-case situation using various radionuclides known to emanate from nuclear power stations and which have been detected on particulates. Two lactating Holstein cows were administered orally one gelatin capsule containing 10 radionuclides in water-soluble form per day for 14 consecutive days. Milk samples were collected and aliquots analyzed in a germanium lithium-drifted detector coupled to a 2048-multichannel gamma-ray analyzer to measure small amounts of complex mixtures of radionuclides. The transfer coefficients of the radionuclides were calculated when their secretion in milk reached or approached a plateau of concentration. The radionuclides and their transfer coefficients to milk were: chromium51 less than 0.01%; manganese54 0.033 +- 0.005%; cobalt60 0.01 +- 0.002%; iron59 0.0048 +- 0.002%; zinc65 0.31 +- 0.07%; selenium75 0.29 +- 0.1%; antimony125 0.011 +- 0.003%; iodine131 0.88 +- 0.05%; and cesium137 0.79 +- 0.08%

1980-01-01

68

Natural convection heat transfer coefficients in phase change material (PCM) modules with external vertical fins  

Energy Technology Data Exchange (ETDEWEB)

To determine the heat transfer coefficient by natural convection for specific geometries, experimental correlations are used. No correlations were found in the literature for the geometries studied in this work. These geometries consisted of a cylindrical module of 88 mm of diameter and 315 mm height with external vertical fins of 310 mm height and 20 and 40 mm length. To determine the heat transfer coefficient by natural convection, experimental work was done. This module, containing PCM (sodium acetate trihydrate), was situated in the middle upper part of a cylindrical water tank of 440 mm of diameter and 450 mm height. The calculated heat transfer coefficient changed by using external fins, as the heat transfer surface was increased. The temperature variation of the PCM and the water are presented as a function of time, and the heat transfer coefficient for different fins is presented as a function of the temperature difference. Experimental correlations were obtained, presenting the Nusselt number as a function of different dimensionless numbers. Different correlations were analysed to find which one fit better to the experimental data. (author)

Castell, Albert; Sole, Cristian; Medrano, Marc; Roca, Joan; Cabeza, Luisa F. [Departament d' Informatica i Enginyeria Industrial, Universitat de Lleida, Pere de Cabrera s/n, 25001 Lleida (Spain); Garcia, Daniel [Departament Projectes d' Enginyeria, Universitat Politecnica de Catalunya, Colom 11, 08222 Terrassa (Spain)

2008-09-15

69

Heat Transfer Coefficient Variations in Nuclear Fuel Rod Bundles  

International Nuclear Information System (INIS)

The single-phase heat transfer performance of a PWR nuclear fuel rod bundle is enhanced by the use of mixing vanes attached to the downstream edges of the support grid straps. This improved single-phase performance will delay the onset of nucleate boiling, thereby reducing corrosion and delaying crud-related issues. This paper presents the variation in measured single-phase heat transfer coefficients (HTC) for several grid designs. Then, this variation is compared with observations of actual in-core crud patterns. While crud deposition is a function of a number of parameters including rod heat flux, the HTC is assumed to be a primary factor in explaining why crud deposition is a local phenomenon on nuclear fuel rods. The data from this study will be used to examine this assumption by providing a comparison between HTC variations and crud deposition patterns. (authors)

2007-10-03

70

Resonant charge transfer at dielectric surfaces  

CERN Document Server

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

71

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

72

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 Ã? 104 to 5.43 Ã? 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

73

Heat transfer coefficients in bubbly and slug flows under microgravity conditions  

Energy Technology Data Exchange (ETDEWEB)

Experimental local heat transfer data were collected onboard NASA`s KC-135 reduced gravity aircraft for two-phase, air-water flow in vertical, upward, co-current flow through a 9.53 mm circular tube. It was found that in the bubbly and slug flow regimes (surface tension dominated regimes), reduced gravity has a tendency to lower the heat transfer coefficient by up to 50% at the lowest gas qualities. As the gas quality is increased (transition to annular flow), the difference between the 1-g and {micro}-g heat transfer coefficients is much less significant. Empirical correlations were developed in terms of the pertinent dimensionless groups; namely the superficial liquid Reynolds number, the Froude number, the Graetz number and the Morton number. The correlations predicted the experimental data within 10--25%, depending on the flow regime and the superficial gas Weber number.

Rezkallah, K.S. [Univ. of Saskatchewan, Saskatoon (Canada). Mechanical Engineering Dept.; Rite, R.W. [Trane, Co., LaCrosse, WI (United States)

1996-12-31

74

Efficiency analysis of straight fin with variable heat transfer coefficient and thermal conductivity  

International Nuclear Information System (INIS)

In this study, one type of applicable analytical method, differential transformation method (DTM), is used to evaluate the efficiency and behavior of a straight fin with variable thermal conductivity and heat transfer coefficient. Fins are widely used to enhance heat transfer between primary surface and the environment in many industrial applications. The performance of such a surface is significantly affected by variable thermal conductivity and heat transfer coefficient, particularly for large temperature differences. General heat transfer equation related to the fin is derived and dimensionalized. The concept of differential transformation is briefly introduced, and then this method is employed to derive solutions of nonlinear equations. Results are evaluated for several cases such as: laminar film boiling or condensation, forced convection, laminar natural convection, turbulent natural convection, nucleate boiling, and radiation. The obtained results from DTM are compared with the numerical solution to verify the accuracy of the proposed method. The effects of design parameters on temperature and efficiency are evaluated by some figures. The major aim of the present study, which is exclusive for this article, is to find the effect of the modes of heat transfer on fin efficiency. It has been shown that for radiation heat transfer, thermal efficiency reaches its maximum value

2012-04-01

75

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 â??widthâ? 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

76

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

77

Heat transfer coefficient determination for flow boiling in vertical and horizontal minichannels  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the results of boiling heat transfer research during FC-72 laminar flow along a minichannel of 1 mm depth, positioned vertically and horizontally, with an enhanced heating surface. One glass pane allows to determine the temperature of the heating wall by liquid crystal thermography. Calculations are aimed at the evaluation of one- and two-dimensional heat transfer approaches to determine the local heat transfer coefficient. In the one-dimensional approach only the direction of the flow in the channel is considered. In the two-dimensional approach the inverse problem in the heating wall and the direct problem in the glass barrier were solved by the finite element method with Trefftz functions as shape functions (FEMT. The developed flow boiling area was studied. Heat transfer coefficient values obtained for the horizontal minichannel were higher than those obtained for the vertical one. When the heat flux supplied to heating wall grows, the share of gas-phase increases leading to the heat transfer coefficient decreases. The same courses of the experiment were observed for the two applied methods, but the results obtained in the one-dimensional approach are considerably higher than in the two-dimensional one. One-dimensional approach seems to be less sensitive to measurement errors.

Piasecka Magdalena

2014-03-01

78

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 "9"9Mo, /sup 123m/Te and "1"3"3Ba. "1"3"3Ba was selected because "1"4"0Ba-"1"4"0La is produced infrequently and availability was uncertain. "1"3"3Ba has a great advantage for our type of experiment because of its longer physical half-life. "9"9Tc 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

79

Mass-transfer coefficients at the uranium adsorption from solution on ion exchange resins  

Energy Technology Data Exchange (ETDEWEB)

The process of uranium adsorption on ion exchange resins is a mass-transfer process of solid-liquid nature asociated with chemical reaction. Mathematical models used in these studies considers a spherical ion exchange resin grain where on its surface and its pores is taking place the chemical reaction. This paper presents experimental data of the uranium adsorption from alkaline solutions on a strong basic ion exchange resin, second type in chlorine form. The resin and the solution are contacting in two ways: fixed bed and perfect mixing. The optimal resin size and mass transfer coefficient was established for uranium adsorption from alkaline solutions. Also, criterial relation were established between mass-transfer process variables, impulse transfer, equipment geometry used for the experiments. (orig.)

Aurelian, F.; Georgescu, D.; Panturu, E.; Udrea, N.

1998-12-31

80

Measurement of Heat Transfer Coefficients in an Agitated Vessel with Tube Baffles  

Directory of Open Access Journals (Sweden)

Full Text Available Cooling or heating an agitated liquid is a very common operation in many industrial processes. A classic approach is to transfer the necessary heat through the vessel jacket. Another option, frequently used in the chemical and biochemical industries is to use the heat transfer area of vertical tube baffles. In large equipment, e.g. fermentor, the jacket surface is often not sufficient for large heat transfer requirements and tube baffles can help in such cases. It is then important to know the values of the heat transfer coefficients between the baffles and the agitated liquid. This paper presents the results of heat transfer measurements using the transient method when the agitated liquid is periodically heated and cooled by hot and cold water running through tube baffles. Solving the unsteady enthalpy balance, it is possible to determine the heat transfer coefficient. Our results are summarized by the Nusselt number correlations, which describe the dependency on the Reynolds number, and they are compared with other measurements obtained by a steady-state method.

M. Dostál

2010-01-01

 
 
 
 
81

Estimation of Extract Yield and Mass Transfer Coefficient in Solvent Extraction of Lubricating Oil  

Digital Repository Infrastructure Vision for European Research (DRIVER)

An investigation was conducted to suggest relations for estimating yield and properties of the improved light lubricating oil fraction produced from furfural extraction process by using specified regression.Mass transfer in mixer-settler has been studied. Mass transfer coefficient of continuous phase, mass transfer coefficient of dispersed phase and the overall mass transfer coefficient extraction of light lubes oil distillate fraction by furfural are calculated in addition to all physi...

Hussain, Hussain K.

2010-01-01

82

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

International Nuclear Information System (INIS)

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

83

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

International Nuclear Information System (INIS)

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

84

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

85

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)

2002-07-07

86

Measurement of the heat transfer coefficient in the dimpled channel: effects of dimple arrangement and channel height  

International Nuclear Information System (INIS)

Heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated, and the diameter (D) and the depth of dimple was 16 mm and 4 mm, respectively. Two channel heights of about 0.6D and 1.2D, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of the dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With the same dimple arrangement, the heat transfer coefficients and the thermal performance factors were higher for the lower channel height. As the distance between the dimples became smaller, the overall heat transfer coefficient and the thermal performance factors increased

2009-03-01

87

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 us...

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

2009-01-01

88

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

2008-09-01

89

Mass transfer coefficients in a hanson mixer-settler extraction column  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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 coefficie [...] nts 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.

90

Interdiffusivities and mass transfer coefficients of NaF gas  

Science.gov (United States)

To clarify the vaporization phenomena of sodium fluoride (NaF), the interdiffusivities of NaF in N2, Ar, and He were measured by thermogravimetric analysis from 1300 to 1770 K. At 1540 K, the interdiffusivity of NaF in N2 (2.46 cm2/s) was slightly larger than that in Ar (2.40 cm2/s), while the interdiffusivity of NaF in He (6.00 cm2/s) was significantly larger than those in the N2 and Ar systems. The Chapman-Enskog equation was used to calculate the interdiffusivities of NaF in N2, Ar, and He. Calculated results were in good agreement with observations for nitrogen and argon; however, calculated results for the NaF-He system were significantly higher than those observed. Overall experimental mass transfer coefficients were described by a Ranz-Marshall type correlation based upon the Nusselt number (Nu), the Reynolds number (Re), and the Schmidt number (Sc): Nu=7.0+0.28 (Re)4(Sc)2 in which the viscosities in the NaF-N2, Ar, or He system were calculated from the Lennard-Jones parameters developed in this study.

Kashiwaya, Y.; Cramb, A. W.

1998-08-01

91

Calculation and Analysis of Heat Transfer Coefficients in a Circulating Fluidized Bed Boiler Furnace  

Science.gov (United States)

A new way for the circulating fluidized bed (CFB) boiler research is proposed by the supervisory information system (SIS) in power plant level. The heat transfer coefficient in CFB boiler furnace is calculated and analyzed by the SIS calculation analysis in a commercial CFB boiler, the way how to calculate the heat transfer coefficient in SIS is introduced, and the heat transfer coefficient is accurately received by calculating a large amount of data from database. The relation about the heat transfer coefficient to unit load, bed temperature, bed velocity, and suspension density is analyzed; the linear relation could be accepted for the commercial CFB design. A new calculating and simple way for the heat transfer coefficient of CFB boiler is proposed for CFB boiler design. Using this research result, the reheat spray water flux larger than the design value in lots of commercial CFB boilers is analyzed; the main reason is the designed heat transfer coefficient smaller than the actual value.

Wang, Zhiwei; Yang, Jianhua; Li, Qinghai

92

Boiling Heat Transfer on Superhydrophilic, Superhydrophobic, and Superbiphilic Surfaces  

CERN Multimedia

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

93

Prediciton of nucleate pool boiling heat transfer coefficients of refrigerant-oil mixtures  

International Nuclear Information System (INIS)

This paper describes an experimental investigation to determine the mechanism governing nucleate pool boiling heat transfer in refrigerant-oil mixtures, the role diffusion plays in this process, and the influence of the fluid mixture properties. Boiling heat transfer date were taken in mixtures of up to 10 per cent oil by weight in R-113. Thermophysical properties of the mixtures (density, viscosity, surface, tension, specific heat, and contact angle) were measured. The decrease in heat transfer coefficient with incresing oil concentration is attributed to diffusion in an oil-enriched region surrounding the growing vapor bubbles. A correlation based on a postulated mechanism is presented which shows fair agreement with the experimental data from this study and with data obtained from the literature

1984-01-01

94

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.

K.S. Suganthi

2012-01-01

95

Mass transfer coefficients in a hanson mixer-settler extraction column  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

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

2008-01-01

96

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

97

Condensation heat transfer on the tube surface of different materials  

International Nuclear Information System (INIS)

In this paper, two kinds of tube surfaces (bare stainless steel tube and Teflon coated tube) in steam-air mixture flow are experimentally studied to obtain design data for the heat exchanger of the latent heat recovery from flue gas. In the test section, 3-tubes are horizontally installed, and steam-air mixture is flowed vertically from top to bottom. The uncertainty for the heat transfer measurement is surveyed to have the uncertainty within 5%. As experimental results, overall heat transfer coefficient of the Teflon (FEP) coated tube is degraded about 20% compared to bare stainless tube. Nusselt number of Teflon (FEP) coated tube in latent heat transfer is lower than that of bare stainless steel tube, but the Sherwood number is higher. The contact angle of the condensate on Teflon coated surface is higher than bare stainless steel surface about 30%, which will be the reason of higher mass transfer coefficient of Teflon coated tube

2002-11-13

98

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

International Nuclear Information System (INIS)

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

99

Effect of design and operation parameters on heat transfer coefficient in condensers  

International Nuclear Information System (INIS)

Accurate and optimum usage of energy sources is gaining importance all over the world due to the increase of energy need and limited energy sources. Increasing condenser efficiency, reduce both the dimensions and the material usage and also the investment cost of the devices. This can be maintained by increasing the heat transfer coefficient in condensers. Generally, tubes having plain inner surfaces are mounted horizontally in serpentine type condenser applications and due to the performance loss results from the congestion in serpentine connections, vertical tube mounting is not preferred. Due to the complexity of the two-phase flow, a single set of correlation for heat transfer cannot be used. Average and local heat transfer coefficient for condensers are determined. Moreover, for each experiments flow pattern is determined and the validity of the correlations are compared according to that flow pattern. In Table 2, some of the experiments for R134a are listed. Local heat transfer coefficient is also important for condenser design. As a result, to design effective condensers the accuracy of the correlations is very important. When all the experiments are taken into account, it is seen that deviation of the correlations differs according to the refrigerant type, tube dimensions, mass flux, saturation temperature and flow pattern. For high mass flux (>400 kg/m2s) Traviss (1973) correlation failed. For small diameters (<3.14 mm) Tandon (1985) correlation estimate the heat transfer coefficient with a high deviation. Most accurate results are obtained for Akers et al. (1959), M.M. Shah (1978), Cavallini and Zecchlin (1974), J.R. Thome - J. El Hajal - A. Cavallini (2003) correlations. For high mass flux and annular flow, M.M. Shah (1978) correlation estimates the heat transfer coefficient with high precision. However, as the tube diameter decrease, this deviation increases. For small tube diameter such as 0.691 mm Cavallini and Zecchlin (1974) gives the most accurate results. J.R. Thome - J. El Hajal - A. Cavallini (2003) correlations are classified according to the flow pattern. For stratified flow the accuracy of that correlation is much better than the others. (author)

2009-01-01

100

Determination of the heat transfer coefficient between bulk medium and packed containers in a batch retort  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The external heat transfer coefficient in steam retort processing was determined experimentally in a pilot scale retort. The heat transfer equations were solved applying finite elements and using the actual retort temperature profile as boundary condition. The instantaneous values of the heat transfer coe cient were determined, to analyse its time-variability along a retort cycle. It was found that reliable results for the external heat transfer coefficient at time t could be obtaine...

Varga, Szabolcs; Oliveira, Jorge C.

2000-01-01

 
 
 
 
101

Heat conduction in the hollow sphere with a power-law variation of the external heat transfer coefficient  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The conduction phenomenon in an insulated sphere is re-worked through a dimensionless approach, where the heat transfer coefficient dependence on the external radius and on the surface temperature, as in the case of forced and free convection, is taken into account. Assuming a power law variation of the convection coefficient [1, 2], and using the results of Sparrow [3], equations and graphs for the most important dimensionless parameters are presented. The developed equations show, for examp...

2000-01-01

102

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

International Nuclear Information System (INIS)

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

1995-09-01

103

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

104

Heat transfer from rough surfaces  

International Nuclear Information System (INIS)

The transformation of the friction data obtained with experiments in annuli can be performed either with the assumption of universal logarithmic velocity profile or of an universal eddy momentum diffusivity profile. For the roughness of practical interest both methods, when properly applied, give good results. For these roughnesses the transformed friction factors seem not to be unduly affected if one assumes a constant slope of the velocity profile equal to 2.5. All the transformation methods of the heat transfer data so far proposed predict too high wall temperatures in the central channels of a 19-rod bundle with three-dimensional roughness. Preliminary calculations show that the application of the superimposition principle with the logarithmic temperature profiles gives good results for the three-dimensional roughness as well. Although the measurements show that the slope of the logarithmic temperature profiles is different from 2.5, the assumption of a constant slope equal to 2.5 does not affect the transformed heat transfer data appreciably. For moderately high roughness ribs the turbulent Prandtl number, averaged over the cross section of a tube, is about the same (approx. 0.8) for rough as for smooth surfaces. The temperature effect on the heat transfer data with air cooling is stronger than originally assumed in the general correlation of Dalle Donne and Meyer. With helium cooling this temperature effect is even stronger. (orig.)

1980-01-01

105

EXPERIMENTAL RESEARCHES OF ENERGY TRANSFER COEFFICIENT DEPENDING ON INDUCTANCE LOAD IN THE DISK MATCHING DEVICE  

Directory of Open Access Journals (Sweden)

Full Text Available The article deals with determination of energy transfer coefficient dependence from primary coil to secondary matching device coil on inductive load value. In the course of researches, the discharge pulses oscillograms have been registred, and the inductance of research inductors and the energy transfer coefficient from the primary matching device coil to the inductor– processing tool have been experimentally determined.

Gnatov, A.

2012-06-01

106

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.

2003-01-01

107

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?

2012-02-01

108

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?

2012-02-01

109

Calculation of heat transfer coefficients for nucleate boiling in binary mixtures of refrigerant-oil  

International Nuclear Information System (INIS)

The heat transfer coefficient for nucleate boiling of pure liquids can be determined in many cases by the simple relation h = C X q /SUP n/ . (In nucleate boiling of mixtures with widely varying properties, the concentration gradient close to the heating surface strongly affects the heat transfer. The composition of the mixture is difficult to obtain there. The authors develop simple relations based on experimental values for four different refrigerant-oil mixtures in concentrations from 0.005 to 0.20) the following relation renders best results: h = 0.085 X (exp X (b1w) + exp X (b2w)) x q For each kind of oil, however, different values of b1, b2 and B have to be used; these are given

1984-01-01

110

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 c...

Torab-mostaedi, M.; Safdari, J.

2009-01-01

111

Plateau diffusion coefficient for arbitrary flux surface geometry  

Energy Technology Data Exchange (ETDEWEB)

A relatively simple but accurate representation has been developed for magnetic flux surfaces; it is valid for finite ..beta.. and it describes configurations with both ellipticity and D-shape. This representation has been applied to the computation of the diffusion coefficient in the plateau regime.

Meier, H.K.; Hirshman, S.P.; Sigmar, D.J.; Lao, L.L.

1981-03-01

112

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)

2006-12-05

113

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 iiiDimple 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.

Dr. Sachin L. Borse

2012-08-01

114

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

115

A Comparative Study of Heat Transfer Coefficients for Film Condensation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Wei, Xiaoyong; Fang, Xiande; Shi, Rongrong

2012-01-01

116

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

117

Experimental study of convective coefficient of mass transfer of avocado (Persia americana Mill.)  

Energy Technology Data Exchange (ETDEWEB)

Most of all energy consumed worldwide comes from fossil fuels derived from petroleum. With the petroleum crisis in the 70 were sought new energy sources, among them renewable. One such source is biodiesel energy, organic matter originated from animal and/or vegetable. Among the various plant species is the avocado (Persia americana Mill.) showing great potential in the production of petroleum extracted from the pulp and the alcohol removed from the seed. The main obstacle for obtaining the petroleum is the high humidity found in the pulp, being necessary to the drying process, which involves the transfer of heat and mass. The aim of this study was to use the mathematical model represented by Newton's Law of Cooling to simulate the mass transfer on the surface of the avocado pulp during the drying process. The equation of the mathematical model was solved numerically and the method of least squares was identified convective coefficient of Mass Transfer. The dryer used in the experimental process was operated with air flow in the vertical, air flow average fixed 3m/s and temperatures of 50, 60 and 70 deg C. The scheme of the dryer used in the research is composed of the following equipment: centrifugal fan, which drives the air-drying; valve, which allows control of airflow; electrical resistance, used for heating air; the drying chamber, where enables measurement of temperature and relative humidity; support for smaller trays; trays smaller, where the samples of the pulp of the avocado are placed; exit of the air of drying for the environment. The result presented shows the ratio of moisture content as a function of temperature over time, where it is possible to also observe that how much bigger the temperature of drying, greater will be the convective coefficient of mass transfer of the avocado. (author)

Alves, Suerda Bezerra; Luiz, Marcia Ramos; Amorim, Joselma Araujo de; Gusmao, Rennam Pereira de; Gurgel, Jose Mauricio [Universidade Federal da Paraiba (LES/UFPB), Joao Pessoa, PB (Brazil). Lab. de Energia Solar

2010-07-01

118

Heat transfer model for liquid boiling on a porous surface  

International Nuclear Information System (INIS)

A model is suggested for the process of bubble boiling on the surface with porous coating. A motion equation for liquid and vapour flows in a porous structure is obtained. The temperature field in a ''wick'' is described by the equation of heat conductivity with heat sinks. The volumetric heat-transfer coefficient with account of heat resistance to liquid evaporation from the meniscus surfaces is calculated

1984-01-01

119

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

International Nuclear Information System (INIS)

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

120

Integral equation solution for internal flow subjected to a variable heat transfer coefficient  

Science.gov (United States)

A solution methodology based on integral equations is presented for the problem of heat transfer to laminar duct flow subjected to an axial variation of the external heat transfer coefficient. The technique offers an efficient and accurate calculation procedure which combines standard analytical methods with a simple numerical integration. In order to examine the effect of external finning, results are calculated for the cases of a stepwise periodic and a harmonic variation of the heat transfer coefficient for both fully developed laminar flow and slug flow. The general procedure is applicable to a wide class of problems in heat and mass transfer involving variable boundary condition parameters.

Vick, B.; Beale, J. H.; Frankel, J. I.

1987-11-01

 
 
 
 
121

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

122

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

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English 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 perfo [...] rmed 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.

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

123

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

2009-06-01

124

Transmittance Coefficients Generation for Fast Radiative Transfer Models: Application to New Satellite Sounding Systems.  

Science.gov (United States)

Polynomial transmittance coefficients internal to the RTTOV fast radiative transfer model were generated, with atmospheric transmittances calculated by using the FASCOD2 line by line model. The FASCOD2 computations are made for a small set of Earth repres...

P. Brunel L. Lavanant G. Rochard

1992-01-01

125

Experimental and Predicted Overall Heat-Transfer Coefficients for Four Residential Air-to-Air Heat Exchangers.  

Science.gov (United States)

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 informati...

R. A. Seban A. Rostami M. Zarringhalam

1981-01-01

126

Simulation Study of Mass Transfer Coefficient in Slurry Bubble Column Reactor Using Neural Network  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The objective of this study was to develop neural network algorithm, (Multilayer Perceptron), based correlations for the prediction overall volumetric mass-transfer coefficient (kLa), in slurry bubble column for gas-liquid-solid systems. The Multilayer Perceptron is a novel technique based on the feature generation approach using back propagation neural network. Measurements of overall volumetric mass transfer coefficient were made with the air - Water, air - Glycerin and air - Alcohol system...

Al-naimi, Safa A.; Salih, Salih A. J.; Mohsin, Hayder A.

2013-01-01

127

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

International Nuclear Information System (INIS)

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)

1982-05-01

128

Estimating the workpiece-backingplate heat transfer coefficient in friction stirwelding  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Purpose - The purpose of this paper is to determine the magnitude and spatial distribution of the heat transfer coefficient between the workpiece and the backingplate in a friction stir welding process using inverse modelling. Design/methodology/approach - The magnitude and distribution of the heat transfer coefficient are the variables in an optimisation problem. The objective is to minimise the difference between experimentally measured temperatures and temperatures obtained using a 3D fini...

Larsen, Anders; Stolpe, Mathias; Hattel, Jesper Henri

2012-01-01

129

Determination and correlation of mass transfer coefficients in a stirred cell  

International Nuclear Information System (INIS)

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

130

Measurement and Prediction of the Average Heat Transfer Coefficient on a Tube  

International Nuclear Information System (INIS)

Most results are for horizontal tubes of diameter ranging 7.6?51 mm. Only Seethes et al. studied variations in local heat transfer coefficients along the tube periphery while controlling the inclination angle. The main result of the previous investigations is that there is a considerable difference among the local heat transfer coefficients along a tube periphery. This has been the major cause of the discrepancy among the results. It is very important to predict the exact heat transfer coefficient on a tube for the thermal design of tubular type heat exchangers. No results have been reported about the way to predict the average value on a tube except Kang who suggested a method for the horizontal tube. The present study is aimed to find out a way of predicting the average heat transfer coefficient with considering the degree of subcooling and the inclination angle. The average heat transfer coefficient was observed at ? =90 .deg in the saturated water regardless of the tube inclination angle. However, as the water was subcooled the location for the average heat transfer coefficient moves to the lower region of the tube

2013-05-01

131

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

132

Experimental Studies on Carbon Dioxide Flow Boiling Heat Transfer Coefficient in Horizontal Smooth Tube  

Science.gov (United States)

The CO2 heat pump water heater ”ECO CUTE” which was commercialized in 2001 has a high potential for energy conservation and greenhouse abatement. The most important element apparatus is always the evaporator in order to develop smaller and higher performance equipment. In this paper, an experimental study has been conducted to measure the pure CO2 flow boiling heat transfer coefficient (99.999 % purity, without oil) in a horizontal smooth tube (outer diameter 6 mm, thickness 0.4 mm). The measured mean heat transfer coefficients are compared with calculated value with using previous experimental heat transfer correlation equations. These two values are different from each other. Mean heat transfer coefficients are measured with varying mass velocity, pressure and heat transfer lengths. The tube length is varied to 3.0 m, 4.0 m and 5.0 m, to distinguish the influence of mass velocity and that of heat flux to the heat transfer coefficient. The test conditions were: CO2 mass velocity from about 150 to about 700 kg?(m2s) (heat flux from about 10 to about 40 kW?m2), quality at inlet of test section is 0.17, CO2 super heat at outlet of test section is 5 K and saturation temperature of CO2 ranges from 0 to 10 °C. As a result, it has been understood that heat flux has a greater influence on the heat transfer coefficient.

Hashimoto, Katsumi; Kiyotani, Akihiro; Sasaki, Naoe

133

Modeling of the substrate and product transfer coefficients for ethanol fermentation  

International Nuclear Information System (INIS)

The transfer phenomena of the substrate and product for ethanol fermentation with immobilized biocatalyst were investigated. Fermentation was carried out with a biocatalyst consisting of Ca-alginate gel in the form of two-layer spherical beads in anaerobic conditions. The determination of kinetic parameters was achieved by fitting bioreaction progress curves to the experimental data. The calculation of the diffusion coefficients was performed by numerical methods for experimental conditions. Finally, the glucose and ethanol transfer coefficients are defined and determined, using the effective diffusion coefficients. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

2008-07-01

134

Soil to grass transfer coefficient for Cr, Mn, Fe, Sr, and Zn  

International Nuclear Information System (INIS)

The soil-plant transfer factor is a parameter required in mathematical models for the assessment of the level of radionuclides in agricultural products. In pre-operational evaluation of the site of the Kecerovce nuclear power plant, soil-grass transfer coefficients for Cr, Mn, Fe, Sr and Zn were determined and are given. (author). 2 tabs

1989-12-11

135

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)

2008-09-01

136

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

137

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

2010-12-01

138

In-reactor measurement of fuel-to-sheath heat transfer coefficients between UO_2 and stainless steel  

International Nuclear Information System (INIS)

An experimental technique has been developed to measure the fuel-to-sheath heat transfer coefficient in operating UO_2 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 UO_2 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

139

Estimation of Extract Yield and Mass Transfer Coefficient in Solvent Extraction of Lubricating Oil  

Directory of Open Access Journals (Sweden)

Full Text Available An investigation was conducted to suggest relations for estimating yield and properties of the improved light lubricating oil fraction produced from furfural extraction process by using specified regression.Mass transfer in mixer-settler has been studied. Mass transfer coefficient of continuous phase, mass transfer coefficient of dispersed phase and the overall mass transfer coefficient extraction of light lubes oil distillate fraction by furfural are calculated in addition to all physical properties of individual components and the extraction mixtures.The effect of extraction variables were studied such as extraction temperature which ranges from 70 to 110°C and solvent to oil ratio which ranges from 1:1 to 4:1 (wt/wt were studied.The results of this investigation show that the extract yield E decreased with decreasing solvent to oil ratio in extract layer and increased with increasing temperature. The fraction of total solvent in the raffinate phase decreased with increasing oil to solvent ratio in raffinate layer and increased with increasing temperature. Solvent to oil ratio in extract layer decreased with increasing temperature and increased with increasing solvent to charge oil ratio at constant temperature. Oil to solvent ratio in raffinate decreased with increasing temperature and increased with increasing solvent to charge oil ratio at constant temperature.Estimated functions are the best modeling function for prediction extraction data at various operating conditions. Mass transfer coefficient of continuous phase kc and mass transfer coefficient of dispersed phase kd are increased with increasing temperature and solvent charge to oil ratio at constant temperature. The over all mass transfer coefficient Kod is increased with increasing temperature and solvent to charge oil ratio; while Kod a is increased with temperature and decreased with solvent to charge oil ratio.

Hussain K. Hussain

2010-01-01

140

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

1996-08-01

 
 
 
 
141

Local Mass Transfer Coefficient for Idealized 2D Urban Street Canyon Models  

Science.gov (United States)

Human activities in urban areas is one of the major sources of anthropogenic releases in the atmospheric boundary layer (ABL). The mechanism of urban morphology for the heat and mass transfer in built environment is thus an attractive topic in the research community. In this paper, a series of laboratory measurements is conducted to elucidate the mass transfer from hypothetical urban roughness constructed by idealized 2D street canyons. The experiments are carried out in the wind tunnel in the University of Hong Kong. The urban ABL structure inside the wind tunnel is controlled by placing small cubic Styrofoam blocks upstream of the test section. The street canyons are fabricated by movable rectangular acrylic blocks so that different building height to street width (aspect) ratios are examined. The height of building blocks is kept minimum to make sure that the urban ABL over the street canyons is high enough for fully developed turbulent flows. The prevailing wind is normal to the street axis, demonstrating the scenario of least pollutant removal from the street canyons to the urban ABL. The sample street canyon is covered by soaked filter papers to represent uniform mass concentrations on the building facades and ground surface. The wet bulb temperature of the filter papers is continuously monitored to ensure saturated conditions. Their weight before and after an experiment is used to measure the amount of water evaporated. Preliminary results illustrate the local mass transfer coefficient distribution for aspect ratios 1/4, 1/2, 1, and 2, which are comparable with those available in literuatre.

Leung, Ka Kit; Liu, Chun-Ho

2011-09-01

142

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

143

Compartment modelling in nuclear medicine: a new program for the determination of transfer coefficients  

International Nuclear Information System (INIS)

In many investigations concerning transport/exchange of matter in a natural system, e.g. functional studies in nuclear medicine, it is advantageous to relate experimental results to a model of the system. A new computer program is presented for the determination of linear transfer coefficients in a compartment model from experimentally observed time-compartment content curves. The program performs a least-square fit with the specified precision of the observed values as weight factors. The resulting uncertainty in the calculated transfer coefficients may also be assessed. The application of the program in nuclear medicine is demonstrated and discussed. (author)

1986-01-01

144

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

145

Experimental determination of heat transfer coefficients in uranium zirconium hydride fuel rod  

International Nuclear Information System (INIS)

This work presents the experiments and theoretical analysis to determine the temperature parameter of the uranium zirconium hydride fuel elements, used in the TRIGA IPR-R1 Research Nuclear Reactor. The fuel thermal conductivity and the heat transfer coefficient from the cladding to the coolant were evaluated experimentally. It was also presented a correlation for the gap conductance between the fuel and the cladding. In the case of nuclear fuels the heat parameters become functions of the irradiation as a result of change in the chemical and physical composition. The value of the heat transfer coefficients should be determined experimentally. (author)

2005-09-02

146

Convective heat transfer coefficients in a full-scale room with and without furniture  

Energy Technology Data Exchange (ETDEWEB)

The convective heat transfer coefficient at an outer ambient wall with a window exposed to natural climate was measured in a room with and without furniture. The method used was to estimate the heat flow from measured temperatures and solar radiation. The convective heat transfer was calculated as the difference between the heat flow through the building element and the calculated long-wave radiation. Even though the accuracy was at best {+-} 15%, the effect of different heating and ventilation strategies could clearly be detected. Local coefficients may be more than 10 times the expected, due to ventilation or position of the radiator. (author)

Wallenten, P. [Lund Institute of Technology (Sweden). Dept. of Building Science

2001-07-01

147

The surface diffusion coefficient for an arbitrarily curved fluidfluid interface.(II). Coefficient for plane-parallel diffusion  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we developed an expression for the coefficient for plane-parallel diffusion for an arbitrarily curved fluid–fluid interface. The expression is valid for ordinary diffusion in binary mixtures, with isotropic bulk phases and an interfacial region that is isotropic in the plane parallel to the dividing surface. The expression can be used in MD simulations and calculates the plane-parallel diffusion coefficient as a function of the perpendicular distance to the dividing surface. F...

Sagis, L. M. C.

2001-01-01

148

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

149

Numerical calculation of wall-to-bed heat-transfer coefficients in gas-fluidized beds  

International Nuclear Information System (INIS)

In this paper, a computer model for a hot gas-fluidized bed is developed. The theoretical description is based on a two-fluid model (TFM) approach in which both phases are considered to be continuous and fully interpenetrating. Local wall-to-bed heat-transfer coefficients have been calculated by the simultaneous solution of the TFM conservation of mass, momentum and thermal energy equations. Preliminary calculations suggest that the experimentally observed large wall-to-bed heat-transfer coefficients, frequently reported in literature, can be computed from the present hydrodynamic model with no turbulence. This implies that there is no need to explain these high transfer rates by additional heat transport mechanisms (by turbulence). The calculations clearly show the enhancement of the wall-to-bed heat-transfer process due to the bubble-induced bed-material refreshment along the heated wall

1992-07-01

150

Absorption properties of diamond and graphite surfaces. 3. Quantum-chemical calculation of surface diffusion coefficients  

International Nuclear Information System (INIS)

The temperature and coverage dependences of surface diffusion coefficients is investigated for atomic carbon on graphite (0001) and diamond (111). With the use of quantum-chemical calculations it is shown that the surface diffusion on graphite can be observed only at temperatures above 2000 K due to high activation barriers. The diffusion processes at a diamond surface can play the important role for kinetics of growth. Diffusion coefficients for diamond (111) reach 2.3 x 10-5 cm2c-1 in the range of temperatures (1000-1400 K) used in particle

1999-10-01

151

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

1996-05-20

152

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

153

Convective and radiative heat transfer coefficients for individual human body segments  

Science.gov (United States)

Human thermal physiological and comfort models will soon be able to simulate both transient and spatial inhomogeneities in the thermal environment. With this increasing detail comes the need for anatomically specific convective and radiative heat transfer coefficients for the human body. The present study used an articulated thermal manikin with 16 body segments (head, chest, back, upper arms, forearms, hands, pelvis, upper legs, lower legs, feet) to generate radiative heat transfer coefficients as well as natural- and forced-mode convective coefficients. The tests were conducted across a range of wind speeds from still air to 5.0 m/s, representing atmospheric conditions typical of both indoors and outdoors. Both standing and seated postures were investigated, as were eight different wind azimuth angles. The radiative heat transfer coefficient measured for the whole-body was 4.5 W/m2 per K for both the seated and standing cases, closely matching the generally accepted whole-body value of 4.7 W/m2 per K. Similarly, the whole-body natural convection coefficient for the manikin fell within the mid-range of previously published values at 3.4 and 3.3 W/m2 per K when standing and seated respectively. In the forced convective regime, heat transfer coefficients were higher for hands, feet and peripheral limbs compared to the central torso region. Wind direction had little effect on convective heat transfers from individual body segments. A general-purpose forced convection equation suitable for application to both seated and standing postures indoors was hc=10.3v0.6 for the whole-body. Similar equations were generated for individual body segments in both seated and standing postures.

de Dear, R. J.; Arens, Edward; Hui, Zhang; Oguro, Masayuki

154

Charge transfer kinetics from surface plasmon resonance voltammetry.  

Science.gov (United States)

On the basis of a quantitative relationship between surface plasmon resonance signal and electrochemical current in the electrochemical surface plasmon resonance (EC-SPR), EC-SPR signal measures the semi-integral of faradaic current. We theoretically discussed the electrode potential and charge transfer kinetics to be determined from surface plasmon resonance voltammetry (or potential sweep EC-SPR) signals for the fully reversible, quasi-reversible, and irreversible redox reactions. The results indicated that the electroanalysis of EC-SPR signal is more straightforward than conventional electrochemical current. Then, we studied two model redox reactions of hexaammineruthenium chloride and 4-nitrotoluene, to obtain half wave potential of quasi-reversible redox reaction, transfer coefficient, and standard rate constant of irreversible redox reaction from EC-SPR signals. PMID:24654883

Lu, Jin; Li, Jinghong

2014-04-15

155

Experimental study of overall heat transfer coefficient in the application of dilute nanofluids in the car radiator  

International Nuclear Information System (INIS)

Heat transfer of coolant flow through the automobile radiators is of great importance for the optimization of fuel consumption. In this study, the heat transfer performance of the automobile radiator is evaluated experimentally by calculating the overall heat transfer coefficient (U) according to the conventional ?-NTU technique. Copper oxide (CuO) and Iron oxide (Fe2O3) nanoparticles are added to the water at three concentrations 0.15, 0.4, and 0.65 vol.% with considering the best pH for longer stability. In these experiments, the liquid side Reynolds number is varied in the range of 50–1000 and the inlet liquid to the radiator has a constant temperature which is changed at 50, 65 and 80 °C. The ambient air for cooling of the hot liquid is used at constant temperature and the air Reynolds number is varied between 500 and 700. However, the effects of these variables on the overall heat transfer coefficient are deeply investigated. Results demonstrate that both nanofluids show greater overall heat transfer coefficient in comparison with water up to 9%. Furthermore, increasing the nanoparticle concentration, air velocity, and nanofluid velocity enhances the overall heat transfer coefficient. In contrast, increasing the nanofluid inlet temperature, lower overall heat transfer coefficient was recorded. -- Highlights: ? Overall heat transfer coefficient in the car radiator measured experimentally. ? Nanofluids showed greater heat transfer performance comparing with water. ? Increasing liquid and air Re increases the overall heat transfer coefficient. ? Increasing the inlet liquid temperature decreases the overall heat transfer coefficient

2013-04-05

156

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 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 effect...

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

2013-01-01

157

Determination of strontium transfer coefficients in soil-plant system at nuclear power plant sites  

International Nuclear Information System (INIS)

In the surroundings of the Mochovce and Dukovany nuclear power plants samples were taken of soils and some plants, namely wheat, barley, clover and lucerne. Strontium was determined by flame emission spectrometry. The found strontium transfer coefficients and discrimination factors in the soil-plant system are tabulated for both localities. (E.S.)

1985-01-01

158

Evaluation of convective heat transfer coefficient of various crops in cyclone type dryer  

Energy Technology Data Exchange (ETDEWEB)

In this paper, an attempt was made to evaluate the convective heat transfer coefficient during drying of various crops and to investigate the influences of drying air velocity and temperature on the convective heat transfer coefficient. Drying was conducted in a convective cyclone type dryer at drying air temperatures of 60, 70 and 80 deg. C and velocities of 1 and 1.5 m/s using rectangle shaped potato and apple slices (12.5 x 12.5 x 25 mm) and cylindrical shaped pumpkin slices (35 x 5 mm). The temperature changes of the dried crops and the temperature of the drying air were measured during the drying process. It was found that the values of convective heat transfer coefficient varied from crop to crop with a range 30.21406 and 20.65470 W/m{sup 2} C for the crops studied, and it was observed that the convective heat transfer coefficient increased in large amounts with the increase of the drying air velocity but increased in small amounts with the rise of the drying air temperature.

Akpinar, E. Kavak [Mechanical Engineering Department, Firat University, 23279 Elazig (Turkey)]. E-mail: eakpinar@firat.edu.tr

2005-09-15

159

Evaluation of convective heat transfer coefficient of various crops in cyclone type dryer  

International Nuclear Information System (INIS)

In this paper, an attempt was made to evaluate the convective heat transfer coefficient during drying of various crops and to investigate the influences of drying air velocity and temperature on the convective heat transfer coefficient. Drying was conducted in a convective cyclone type dryer at drying air temperatures of 60, 70 and 80 deg. C and velocities of 1 and 1.5 m/s using rectangle shaped potato and apple slices (12.5 x 12.5 x 25 mm) and cylindrical shaped pumpkin slices (35 x 5 mm). The temperature changes of the dried crops and the temperature of the drying air were measured during the drying process. It was found that the values of convective heat transfer coefficient varied from crop to crop with a range 30.21406 and 20.65470 W/m2 C for the crops studied, and it was observed that the convective heat transfer coefficient increased in large amounts with the increase of the drying air velocity but increased in small amounts with the rise of the drying air temperature

2005-09-01

160

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

2007-12-01

 
 
 
 
161

Clinic based transfer of the ND,w60Co calibration coefficient using a linear accelerator  

International Nuclear Information System (INIS)

Ionization chambers used for reference dosimetry require a local secondary standard ionization chamber with a 60Co absorbed dose to water calibration coefficient ND,w60Co traceable to a national primary standards dosimetry laboratory or an accredited secondary dosimetry calibration laboratory. Clinic based (in-house) transfer of this coefficient to tertiary reference ionization chambers has traditionally been accomplished with chamber cross calibration in water using a 60Co beam; however, access to 60Co teletherapy machines has become increasingly limited for clinic based physicists. In this work, the accuracy of alternative methods of transferring the ND,w60Co calibration coefficient using 6 and 18 MV photon beams from a linear accelerator in lieu of 60Co has been investigated for five different setups and four commonly used chamber types.

2009-03-01

162

Apparent Charge Transfer at Semiconductor Surfaces  

Energy Technology Data Exchange (ETDEWEB)

We investigate the apparent charge transfer between adatoms in the GeXPb[l.XjGe(lll) interface both experimentally and theoretically. Scanning tunneling microscopy and surface core level measurements suggest significant charge transfer from the Ge adatoms to the Pb adatoms. However, first-principles calculations unambiguously find that the total electronic displacement is negligibly small, and that the results of published experiments can be explained as a result of bond rearrangement.

Carpinelli, Joseph M.; Stumpf, Roland R.; Weitering, Hanno H.

1999-05-11

163

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

164

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

165

Experimental investigation and comparison of heat transfer coefficient of a two phase closed thermosyphon  

Directory of Open Access Journals (Sweden)

Full Text Available In this study, we investigated and reviewed the heat transfer equations of the evaporator and condenser of a two phase closed Thermosyphon as well as the differences between this equations for a working fluid and different conditions. The heat transfer limits of a two phase closed thermosyphon such as sonic, flooding (or entrainment dry-out and boiling are investigated . A good agreement is observed between analytical results of this study and the analytical and experimental results of those available in the open literature. The heat transfer limits are very important in thermosyphons and have to be calculated accurately while the input heat must be lower than the heat transfer limits for the operations of thermosyphon without any problem. Also by using the experimental results a semi empirical equation for heat transfer coefficient of evaporator was proposed.

I. Khazaee

2014-01-01

166

Determination of heat transfer coefficient between a fluid and a wall  

International Nuclear Information System (INIS)

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

1981-01-01

167

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

Science.gov (United States)

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. PMID:23947050

Li, Zhi-Hua; Fan, Chang-Qing; Wang, Xiao-Chang

2013-06-01

168

Analysis of some available heat transfer coefficients applicable to solar chimney power plant collectors  

Energy Technology Data Exchange (ETDEWEB)

A solar chimney power plant consists of a translucent collector which heats the air near the ground and guides it into the base of a chimney at its centre. The buoyant air rises in the chimney and electricity is generated through one or more turbines in or near the base of the chimney. Various studies about solar chimney power plant performance have been published. Different calculation approaches with a variety of considerations have been applied to calculate chimney power plant performance. In particular, two comprehensive studies are relevant, namely those of (Bernardes, M.A.d. S., Voss, A., Weinrebe, G., 2003. Thermal and technical analyses of solar chimneys. Solar Energy 75, 511-524; Pretorius, J.P., Kroeger, D.G., 2006b. Solar chimney power plant performance. Transactions of the ASME 128, 302-311). The paper compares the methods used to calculate the heat fluxes in the collector, and their effects on solar chimney performance. Reasons for the discrepancies between the predictions of the two models are given. In general the Pretorius model produces higher heat transfer coefficients and higher heat rate fluxes for both the roof and for the ground surfaces. The two approaches lead to very similar air temperature rises in the collector and thus, similar produced power. (author)

Aurelio dos Santos Bernardes, Marco; Von Backstroem, Theodor W.; Kroeger, Detlev G. [Department of Mechanical Engineering, University of Stellenbosch, Private Bag X1, Western Cape, Matieland 7602 (South Africa)

2009-02-15

169

Condensation heat transfer coefficients of flammable refrigerants on various enhanced tubes  

Energy Technology Data Exchange (ETDEWEB)

In this study, external condensation Heat Transfer Coefficients (HTCs) of six flammable refrigerants of propylene (R1270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of 39 .deg. C on a 1023 fpm low fin and turbo-C tubes. All data were taken under the heat flux of 32{approx}116 and 42{approx}142 kW/m{sup 2} for the low fin and turbo-C tubes respectively. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling. HFC32 and DME showed up to 30% higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene, propane, isobutane, and butane showed similar or lower HTCs than those of HCFC22. Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of 7.3%. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate.

Park, Ki Jung; Jung, Dong Soo [Inha Univ., Incheon (Korea, Republic of)

2005-10-15

170

Condensation heat transfer coefficients of flammable refrigerants on various enhanced tubes  

International Nuclear Information System (INIS)

In this study, external condensation Heat Transfer Coefficients (HTCs) of six flammable refrigerants of propylene (R1270), propane (R290), isobutane (R600a), butane (R600), dimethylether (RE170), and HFC32 were measured at the vapor temperature of 39 .deg. C on a 1023 fpm low fin and turbo-C tubes. All data were taken under the heat flux of 32?116 and 42?142 kW/m2 for the low fin and turbo-C tubes respectively. Flammable refrigerants' data obtained on enhanced tubes showed a typical trend that external condensation HTCs decrease with increasing wall subcooling. HFC32 and DME showed up to 30% higher HTCs than those of HCFC22 due to their excellent thermophysical properties. Propylene, propane, isobutane, and butane showed similar or lower HTCs than those of HCFC22. Beatty and Katz' correlation predicted the HTCs of the flammable refrigerants obtained on a low fin tube within a mean deviation of 7.3%. Turbo-C tube showed the best performance due to its 3 dimensional surface geometry for fast removal of condensate

2005-10-01

171

Estimation of internal heat transfer coefficients of a hybrid (PV/T) active solar still  

Energy Technology Data Exchange (ETDEWEB)

In this paper, an attempt is made to estimate the internal heat transfer coefficients of a deep basin hybrid (PV/T) active solar still. The estimation is based on outdoor experimental observation of hybrid (PV/T) solar still for composite climate of New Delhi (latitude 28 35'N and longitude 77 12'E). The internal heat transfer coefficients are evaluated by using thermal models proposed by various researchers. The comparison of hourly yield predicted using various thermal models to the experimental has also been carried out by evaluating the correlation coefficient and percentage deviation. It is observed that, Kumar and Tiwari model (KTM) better validate the results than the others model. The average annual values of convective heat transfer coefficient for the passive and hybrid (PV/T) active solar still are observed as 0.78 and 2.41 W m{sup -2} K{sup -1}, respectively at 0.05 m water depth. (author)

Kumar, Shiv; Tiwari, G.N. [Centre for Energy Studies, Indian Institute of Technology, Haus Khas, New Delhi 11 00 16 (India)

2009-09-15

172

Free Convective Heat Transfer From A Vertical Surface For The Case Of Linearly Varying Thermal Potential  

Directory of Open Access Journals (Sweden)

Full Text Available The present theoretical investigation deals with the problem of free convective heat transfer from a vertical plate having linear temperature gradient along its surface to the surrounding thermally stratified fluid. Integral method of analysis is adopted to investigate the effect of four parameters viz., the gradients of temperature in the fluid and the wall, Grashof number and Prandtl number on heat transfer coefficients. It is observed from the numerical results that an increase in the surface temperature gradient would result in higher heat transfer coefficients than those observed in isothermal wall case.

Parvataneni

2013-09-01

173

A Study on the Determination of the Seasonal Heat Transfer Coefficient in KURT Under Forced Convection  

International Nuclear Information System (INIS)

In a high-level waste (HLW) repository, heat is generated by the radioactive decay of the waste. This can affect the safety of the repository because the surrounding environment can be changed by the heat transfer through the rock. Thus, it is important to determine the heat transfer coefficient of the atmosphere in the underground repository. In this study, the heat transfer coefficient was estimated by measuring the indoor environmental factors in the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT) under forced convection. For the experiment, a heater of 5 kw capacity, 2 meters long, was inserted through the tunnel wall in the heating section of KURT in order to heat up the inside of the rock to 90 .deg. C, and fresh air was provided by an air supply fan connected to the outside of the tunnel. The results showed that the average air velocity in the heating section after the provision of the air from outside of the tunnel was 0.81 m/s with the Reynolds number of 310,000 ? 340,000. The seasonal heat transfer coefficient in the heating section under forced convection was 7.68 W/m2 K in the summer and 7.24 W/mm2 K in the winter

2010-09-01

174

On the critical properties of surface diffusion coefficient  

International Nuclear Information System (INIS)

Thermodinamic peculiarities of diffusion coefficient behaviour in the critical vicinity of continuous phase transition are studied theoretically. It is shown that in such conditions the diffusion coefficient grows anomalously of turns to zero depending on the sign of its critical index

1993-05-01

175

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

176

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

International Nuclear Information System (INIS)

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

177

Friction factors and heat transfer coefficients for hydrogen systems operating at supercritical pressures  

International Nuclear Information System (INIS)

Predicting heat transfer coefficients and friction factors for hydrogen systems operating near and above the thermodynamic critical pressure is at best difficult. Yet most hydrogen land-based and aerospace systems of significant power density operate within this regime. In this paper the authors discuss a modification of the Patankar-Spalding method to include density fluctuations in predicting heat and mass transfer. The essence of this method is then empirically expressed in terms of the volumetric expansion coefficient, the wall to bulk temperature difference, and the reduced Nusselt number. The expression is then applied to hydrogen data. The method is meant to facilitate preliminary design, but for detailed analyses the numerical code is recommended

1985-01-01

178

Analysis of measurement errors influence on experimental determination of mass and heat transfer coefficient  

International Nuclear Information System (INIS)

The influence of temperature and concentration measurement errors on experimental determination of mass and heat transfer coefficients is analysed. Calculus model of coefficients and of measurement errors, the experimental data obtained on the water isotopic distillation plant and the results of determinations are presented. The experimental distillation column, with inner diameter of 108 mm, have been equipped with B7 structured packing on a height of 14 m. This column offers the possibility to measure vapour temperature and isotopic concentration in 12 locations. For error propagation analysis, the parameters measured for each packing bed, namely temperature and isotopic concentration of the vapour, were used. A relation for calculation of maximum error of experimental determinations of mass and heat transoprt coefficients is given. The experimental data emphasize the 'ending effects' and regions with bad thermal insulation. (author)

2003-09-25

179

Heat transfer coefficient measurements for mixed gas working fluids at cryogenic temperatures  

Energy Technology Data Exchange (ETDEWEB)

The use of mixed gas working fluids has become common in Joule-Thomson type cryocoolers for a variety of applications. However, there is very little data or theory currently available regarding the heat transfer coefficient associated with these multi-component, multi-phase mixtures at cryogenic temperatures. This paper describes an experimental test facility and procedure that has been used to make careful measurements of the horizontal, flow boiling heat transfer coefficient for several hydrocarbon mixtures that are nominally optimal for small, Joule-Thomson cryocoolers in the 80 K to 120 K operating range. Data are presented over a range of temperatures from 100 K to room temperature and for several pressures and mass flow rates. The results indicate that quality and mass flux are the most important parameters governing the heat transfer coefficient among those that were varied. The experiment is verified by carrying out tests using single-phase, pure nitrogen gas and comparing the results with the Dittus-Boelter equation. The experimental uncertainty of the measurements is estimated from 1st principles; additionally, the repeatability of the experimental measurements was investigated by replicating tests at a nominal set of operating conditions and composition on separate days. The measurements presented here are intended to aid in the design of small, mixed-gas Joule-Thomson cryocoolers. (Author)

Nellis, Gregory; Hughes, Cory; Pfotenhauer, John [Wisconsin Univ., Dept. of Mechanical Engineering, Madison, WI (United States)

2005-08-01

180

Transfer coefficients of selected radionuclides to animal products. II. Hen eggs and meat  

Energy Technology Data Exchange (ETDEWEB)

Transfer coefficients to eggs and meat were determined after acute oral doses of /sup 95m/Tc, /sup 99/Mo, /sup 123m/Te, /sup 133/Ba, /sup 131/I, /sup 95/Zr and /sup 95/Nb to laying hens. The mean values (in units of d kg-1) to eggs and hen meat were, respectively, 3.0 and 0.03 for Tc, 0.87 and 0.18 for Mo, 5.1 and 0.60 for Te, 0.87 and 9.2 x 10(-3) for Ba, 3.2 and 0.01 for I, 2 x 10(-4) and 6 x 10(-5) for Zr, and 1 x 10(-3) and 3 x 10(-4) for Nb. For the same radionuclides administered in the same chemical form, transfer coefficients for eggs are about one to two orders of magnitude higher than for cow's milk, while the transfer coefficients for hen meat are several orders of magnitude higher than for beef.

Ennis, M.E. Jr.; Ward, G.M.; Johnson, J.E.; Boamah, K.N.

1988-02-01

 
 
 
 
181

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.

G.N. Tiwari

2006-01-01

182

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?

2009-04-01

183

Experimental Measurement Of Drop Phase Mass Transfer Coefficients For The Carbon Tetrachloride-Acetic Acid-Water System  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The overall mass transfer coefficients of single drops of carbon tetrachloride falling in a stagnant continuous phase of water containing acetic acid as solute were measured experimentally for different dispersed phase flowrates and drop falling times. The measured mass transfer coefficients were lower than those estimated from the mass transfer models for circulating drops but were reasonably in agreement with the stagnant drop model. The observed deviation is attributed to the slow dimer...

Javed, K. H.

1991-01-01

184

Effects of cooling and internal wave motions on gas transfer coefficients in a boreal lake  

Directory of Open Access Journals (Sweden)

Full Text Available Lakes and other inland waters contribute significantly to regional and global carbon budgets. Emissions from lakes are often computed as the product of a gas transfer coefficient, k 600 , and the difference in concentration across the diffusive boundary layer at the air–water interface. Eddy covariance (EC techniques are increasingly being used in lacustrine gas flux studies and tend to report higher values for derived k 600 than other approaches. Using results from an EC study of a small, boreal lake, we modelled k 600 using a boundary-layer approach that included wind shear and cooling. During stratification, fluxes estimated by EC occasionally were higher than those obtained by our models. The high fluxes co-occurred with winds strong enough to induce deflections of the thermocline. We attribute the higher measured fluxes to upwelling-induced spatial variability in surface concentrations of CO2 within the EC footprint. We modelled the increased gas concentrations due to the upwelling and corrected our k 600 values using these higher CO2 concentrations. This approach led to greater congruence between measured and modelled k values during the stratified period. k 600 has a well-resolved and ~cubic relationship with wind speed when the water column is unstratified and the dissolved gases well mixed. During stratification and using the corrected k 600 , the same pattern is evident at higher winds, but k 600 has a median value of ~7 cm h?1 when winds are less than 6 m s?1, similar to observations in recent oceanographic studies. Our models for k 600 provide estimates of gas evasion at least 200% higher than earlier wind-based models. Our improved k 600 estimates emphasize the need for integrating within lake physics into models of greenhouse gas evasion.

Jouni J. Heiskanen

2014-05-01

185

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

186

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

187

The influence of a heat transfer coefficient probe on fluid flow near wall  

Directory of Open Access Journals (Sweden)

Full Text Available Good knowledge of the convective boundary condition is necessary for finite element analysis of thermal deformation behavior in machine tools. There are a number of correlation equations for natural and forced convection and several correlations for mixed convection. Due to a relatively wide range of dimensions, temperatures and speeds, all regimes of convective heat transfer can be observed in machine tools, including the transition region between laminar and turbulent free convection, characterized by Rayleigh number values ranging between Ra = 108 – 109. Since convection in machine tools is highly influenced by external and internal factors, the heat transfer coefficient characterizing convective heat transfer and its changes has to be evaluated experimentally. An experimental technique for evaluating the heat transfer coefficient on the wall and its changes between the wall and the ambient air, based on an active sensor, is being developed. Since the probe dimensions are not negligible, given the fluid motion structures near the wall which are induced by buoyancy or by forced flow, the influence of the probe has to be considered. Paper deals with latest experimental results and summarizes previous work.

Mareš Martin

2012-04-01

188

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

2011-01-01

189

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

International Nuclear Information System (INIS)

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

190

Evaluation of heat transfer surfaces for compact recuperator using a CFD code  

Science.gov (United States)

Exhaust recovery recuperator is mandatory in order to realize a thermal efficiency of 30% or higher for micro turbines. In this work an attempt is made to select the cross corrugated heat transfer surface with minimum core volume of a recuperator matrix using a CFD code. Analysis is carried out for selected cross corrugated heat transfer surface configurations. The relation between the minimum core volume from design calculation and average skin friction coefficient from CFD analysis has been established.

Ashok Babu, T. P.; Talekala, Mohammad Shekoor

2009-04-01

191

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

192

A criterion for the assessment of the reliability of ASHRAE conduction transfer function coefficients  

Energy Technology Data Exchange (ETDEWEB)

This paper presents a new mathematical approach, which, when applied to conduction transfer functions (CTFs) of a multi-layered wall, is able to predict the reliability of building simulations. This new procedure can be used to identify the best set of CTF coefficients, which are a critical point at the core of the ASHRAE calculation methodology founded on the transfer function method. To evaluate the performance of different CTF coefficient sets, the authors performed a large number of thermal simulations on the multi-layered walls included in the ASHRAE Handbook, volume fundamentals, and on other walls typical of Mediterranean building heritage. Those data were employed to test an algorithm able to assess the reliability of the simulations. The numerical results show that it is possible to select the optimal number of coefficients on the basis of the size of the poles of a CTF. The proposed criterion, which employs a pole threshold value, is highly accurate, fast and easy to integrate in the most diffuse building simulation tools. (author)

Ciulla, Giuseppina; Lo Brano, Valerio; Orioli, Aldo [Dipartimento di Ricerche Energetiche ed Ambientali, University of Palermo, Viale delle Scienze edificio 9, 90128 Palermo (Italy)

2010-09-15

193

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 da...

2007-01-01

194

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Kaliannan Saravanan; Rangasamy Rajavel

2009-01-01

195

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 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°1...

Anil Kumar; Tiwari, G. N.

2006-01-01

196

Prediction of forced convective boiling heat transfer coefficient of pure refrigerants and binary refrigerant mixtures inside a horizontal tube  

International Nuclear Information System (INIS)

Forced convective boiling heat transfer coefficients were predicted for an annular flow inside a horizontal tube for pure refrigerants and nonazeotropic binary refrigerant mixtures. The heat transfer coefficients were calculated based on the turbulent temperature profile in liquid film and vapor core considering the composition difference in vapor and liquid phases, and the nonlinearity in mixing rules for the calculation of mixture properties. The heat transfer coefficients of pure refrigerants were estimated within a standard deviation of 14% compared with available experimental data. For nonazeotropic binary refrigerant mixtures, prediction of the heat transfer coefficients was made with a standard deviation of 18%. The heat transfer coefficients of refrigerant mixtures were lower than linearly interpolated values calculated from the heat transfer coefficients of pure refrigerants. This degradation was represented by several factors such as the difference between the liquid and the overall compositions, the conductivity ratio and the viscosity ratio of both components in refrigerant mixtures. The temperature change due to the concentration gradient was a major factor for the heat transfer degradation and the mass flux itself at the interface had a minor effect

2003-06-01

197

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

198

Experimental investigation of scale formation at heat transfer surface in PWR secondary system  

International Nuclear Information System (INIS)

In the secondary system of steam generators (SGs) of PWR plants, iron is brought from feedwater and some of it is brought out with blow down of SGs, then others build upon an equipment in the SGs. The iron deposit onto heat transfer surface and form a scale, and increases heat transfer resistance. Then it may affect heat transfer performance. The secondary water chemistry in Japanese PWR plants is operated under the AVT condition (NH_3 and N_2H_4). Feedwater usually contains very low concentration of iron. The study was performed jointly by 5 Japanese utilities and Japanese plant manufacturer of PWR plant, as a title of ''The study on secondary water chemistry to retard deposition onto the secondary side surface of heat transfer tube of SG''. This paper presents investigated results of relationship between feedwater chemistry and scale formation onto heat transfer surface, and heat transfer coefficient. (authors). 6 figs., 2 tabs., 6 refs

1994-01-01

199

A review of measured values of the milk transfer coefficient (fsub(m)) for iodine  

International Nuclear Information System (INIS)

Most published assessments of the environmental transport of iodine have used a value of 1 X 10-2 days per litre (d/1) for the transfer coefficient (fsub(m)) which relates the concentration per litre of milk to the daily amount of the element ingested by a cow. However, the USNRC has recommended (USNRC 77) a value of 0.6 X 10-2 d/1 for the transfer of iodine to cow's milk and 6 X 10-2 d/1 for goat's milk. A literature survey of published values of fsub(m) leads to a recommendation which deviates from the values chosen by the USNRC. An fsub(m) of 0.5 d/1 for goat's milk and an fsub(m) of 1 X 10-2 for cow's milk appear to be more appropriate. (author)

1978-01-01

200

Comparison of the Friction-Loss Coefficient for the Gap of Two Contact Surfaces and a Crack  

International Nuclear Information System (INIS)

A leak-detection method has been developed by measuring the pressure variation between the inner and outer heat transfer tubes of a double-wall tube steam generator. An experiment was carried out to measure the leak rate in the gap between two surfaces pressed with a hydraulic press in order to simulate the phenomena, and a correlation was determined for the leak rate in a micro gap. However, in the correlation, the gap width and friction coefficient were coupled with the surface roughness, which affects the two parameters. The two parameters were separated using a surface-contact model to develop a correlation for the friction coefficient. The correlation was compared with the existing correlations used for crack analysis. Although the applied ranges of Reynolds numbers were different, the developed correlation for Reynolds numbers of 0.1.0.35 showed similar tendencies to existing correlations used for higher Reynolds numbers

2011-10-01

 
 
 
 
201

Comparison of the Friction-Loss Coefficient for the Gap of Two Contact Surfaces and a Crack  

Energy Technology Data Exchange (ETDEWEB)

A leak-detection method has been developed by measuring the pressure variation between the inner and outer heat transfer tubes of a double-wall tube steam generator. An experiment was carried out to measure the leak rate in the gap between two surfaces pressed with a hydraulic press in order to simulate the phenomena, and a correlation was determined for the leak rate in a micro gap. However, in the correlation, the gap width and friction coefficient were coupled with the surface roughness, which affects the two parameters. The two parameters were separated using a surface-contact model to develop a correlation for the friction coefficient. The correlation was compared with the existing correlations used for crack analysis. Although the applied ranges of Reynolds numbers were different, the developed correlation for Reynolds numbers of 0.1.0.35 showed similar tendencies to existing correlations used for higher Reynolds numbers.

Nam, Ho Yun; Choi, Byoung Hae; Kim, Jong Bum; Lee, Young Bum [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2011-10-15

202

AFDM: An Advanced Fluid-Dynamics Model. Volume 3: AFDM heat-transfer and momentum-exchange coefficients.  

Science.gov (United States)

This report consists of three parts. First, for the standard Advanced Fluid-Dynamics Model (AFDM), heat-transfer coefficients between components are worked out, depending on the different possible topologies. Conduction, convection, and radiative heat-tra...

J. Berthier D. Wilhelm W. R. Bohl

1990-01-01

203

Evaluation of the RETRAN-3D Wall Friction Models and Heat Transfer Coefficient Correlations  

International Nuclear Information System (INIS)

This paper presents an evaluation of many of the RETRAN-3D two-phase pressure drop and heat transfer models by comparing model prediction to a large body of experimental data.RETRAN-3D has been used to evaluate multiple two-phase pressure drop models utilizing an extensive experimental two-phase pressure drop database. The experimental pressure drop data cover both heated and adiabatic tests in upflow and horizontal configurations for a wide range of key parameters such as pressure, mass flux, quality, and pipe diameters. Two RETRAN-3D two-phase friction options and the Friedel two-phase friction model are tested and compared to the data. For the two-phase friction models compared herein, the modified Baroczy model available in RETRAN-3D is the best choice for all adiabatic and diabatic situations.The RETRAN-3D code has also been used to simulate a wide variety of heat transfer experiments. These heat transfer data cover single-phase and two-phase conditions over a large range of pressure, heat flux, and mass flux values. The performance of the RETRAN-3D default forced convection heat transfer coefficient correlations is evaluated. The Petukhov correlations provide comparable results for single-phase liquid, but the Dittus-Boelter model provides markedly better statistics for single-phase vapor. The RETRAN five-equation model that combines the Dittus-Boelter and Thom correlations provides the best overall subcooled and saturated boiling statistics and scatter chart behavior

2003-04-01

204

Reconstruction of the heat transfer coefficient on the grounds of experimental data  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: Solidification of pure metal can be modelled by a two-phase Stefan problem, in which the distribution of temperature in the solid and liquid phases is described by the heat conduction equation with initial and boundary conditions. The inverse Stefan problem can be applied to solve design problems in casting process.Design/methodology/approach: In numerical calculations the alternating phase truncation method, the Tikhonov regularization and the genetic algorithm were used. The featured examples of calculations show a very good approximation of the experimental data.Findings: The verification of the method of reconstructing the cooling conditions during the solidification of pure metals. The solution of the problem consists of selecting the heat transfer coefficient on the boundary, so that the temperature in selected points on the boundary of the domain assumes given values.Research limitations/implications: The method requires that it must be possible to describe the sought boundary condition by means of a finite number of parameters. It is not necessary, that the sought boundary condition should be linearly dependent on those parameters.Practical implications: The presented method can be easy applied to solve design problems of different types, e.g. for the design of continuous casting installations (incl. the selection of the length of secondary cooling zones, the number of jets installed in individual zones, etc..Originality/value: Verification, on the grounds of experimental data, the formerly devised method of determining the heat transfer coefficient during the solidification of pure metals.

D. S?ota

2009-05-01

205

An analytical-empirical model to predict heat transfer coefficients in circulating fluidized bed combustors  

Energy Technology Data Exchange (ETDEWEB)

An analytical-empirical model was developed to predict local heat transfer coefficients in circulating fluidized bed (CFB) combustors. The fluid is considered to be composed of a dispersed phase and cluster of particles. Both convection and thermal radiation are taken into account. The estimation of the parameters in the model is discussed and suggestions as well as a sensitivity analysis are given. The model is applied to predict heat transfer coefficients on membrane walls of a CFB boiler for which an experimental investigation had been carried out previously. The predictions were in good agreement with experimental results. (orig.) [Deutsch] Ein analytisch-empirisches Modell zur Ermittlung der lokalen Waermeuebergangskoeffizienten in zirkulierenden Wirbelschichtoefen wird vorgestellt, wobei das Fluid aus einer dispersen Phase und einem Cluster von Partikeln zusammengesetzt sein soll. Sowohl Konvektion als auch Waermestrahlung finden Beruecksichtigung. Die das Modell beschreibenden Parameter werden abgeschaetzt und eingehend diskutiert. Das Modell dient zur Ermittlung von Waermeuebertragungskoeffizienten an der Membranwand eines CFB-Verdampfers, fuer den eine experimentelle Untersuchung vorliegt. Die Uebereinstimmung zwischen Theorie und Experiment ist gut. (orig.)

Golriz, M.R. [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Thermo and Fluid Dynamics; Sunden, B. [Lund Inst. of Tech. (Sweden). Div. of Heat Transfer

1995-09-01

206

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

International Nuclear Information System (INIS)

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

207

A Novel Method for Measuring the Diffusion, Partition and Convective Mass Transfer Coefficients of Formaldehyde and VOC in Building Materials  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The diffusion coefficient (Dm) and material/air partition coefficient (K) are two key parameters characterizing the formaldehyde and volatile organic compounds (VOC) sorption behavior in building materials. By virtue of the sorption process in airtight chamber, this paper proposes a novel method to measure the two key parameters, as well as the convective mass transfer coefficient (hm). Compared to traditional methods, it has the following merits: (1) the K, Dm and hm can be simultaneously ob...

Xiong, Jianyin; Huang, Shaodan; Zhang, Yinping

2012-01-01

208

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

209

The generalized correlation for the evaluation of the influence of the Stefan flow on the heat transfer coefficient  

Science.gov (United States)

The analytical equations for the steady-state heat-and-mass transfer in the steam evaporation/condensation processes from the steam-gas mixtures on the planar and spherical surfaces are derived. The vapor flow through the motionless dry gas is considered according to the method proposed by Maxwell for the solution of the diffusion problems. The relationships for the calculation of the coefficients taking into account an increase in the mass output and an increase or a decrease in the heat emission (depending on the directions of the heat-and-mass flows) as a result of the influence of the Stefan flow are presented. The derived relationships can be used to calculate the apparatuses in which the steam evaporation or condensation from the steam-gas mixture occurs (the coolers of the vapor from deaerators, the apparatuses for the deep utilization of the heat of the combustion products, the condensation boilers, etc.).

Baskakov, A. P.; Rakov, O. A.

2013-11-01

210

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

211

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

212

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

CERN Document Server

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

213

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

International Nuclear Information System (INIS)

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

214

Analysis of the influence of measuring errors in experimental determinations of the mass and heat transfer coefficients  

International Nuclear Information System (INIS)

The paper analyses the influence of measuring errors of the operation parameters (flows, temperatures, pressures, and concentrations) in the experimental determination of the mass and heat transfer coefficients. Data obtained on experimental plants for hydrogen isotopes separation, by hydrogen distillation and water distillation, and calculus model for errors propagation are presented. The results are tabulated. The variation intervals of transfer coefficients are marked graphically. The study of the measuring errors is an intermediate stage, extremely important, in experimental determination of criterion relation coefficients, specific relations for B7 structured packing. (authors)

2002-10-10

215

Determination of the pressure drop and the heat transfer coefficient in a gas-solid two-phase flow  

International Nuclear Information System (INIS)

An experimental study was developed for a vertical gas solid two phase flow with heat transfer by analysing the gradient of both static pressure and temperature alongside the system. The measurements were used to produce the isothermal hydrodynamic entry lenght and the gas-solid heat transfer coefficient as well as the influence of the solid particle. (Author)

1983-12-13

216

Retrieval of surface roughness parameters from dual-frequency measurements of radar backscattering coefficients  

Science.gov (United States)

The use of dual-frequency data of backscattering coefficients at a fixed angle to estimate surface roughness parameters is evaluated. Radar backscattering coefficients at 1.5 and 4.25 GHz are calculated using a model based on Kirchhoff approximation of electromagnetic wave scatttering from a rough soil surface. Plots of the calculated backscattering coefficients for Kansas soil moisture contents at the C- and L-band frequencies and HH polarization are analyzed. The effects of changes in correlation length on the backscattering coefficients are investigated. The calculated backscattering coefficients are compared with scatterometer data collected at 1.5 and 4.25 GHz, and it is detected that the model and field data correlate well. The data reveal that it is possible to retrieve the surface roughness parameters from measured radar data.

Mo, Tsan; Wang, James R.; Schmugge, Thomas J.

1987-01-01

217

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

2009-10-01

218

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

International Nuclear Information System (INIS)

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

219

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

220

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

 
 
 
 
221

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

222

Measurement of the transfer coefficient for radiocesium transport from a sheep's diet to its milk  

International Nuclear Information System (INIS)

The rate of increase and decay of radio contamination secreted in sheep's milk, resulting from a constant level of radiocesium in the animals' diet, was investigated. Ten lactating ewes were used in the experiment. For a period of 12 d the animals fed on contaminated grass, resulting in a daily radiocesium intake of 832 Bq per animal. They were subsequently returned to a contamination-free diet and were monitored for another 9 d. Throughout the period of the experiment, 134Cs and 137Cs concentrations in the animals' milk were measured daily with an 18% efficiency, high-resolution Ge detector. The data were in satisfactory agreement with the predictions of a simple two-compartment theory. The transfer coefficient, describing the steady-state equilibrium in this model, was measured as fm = 0.058 +/- 0.007 dL-1

1987-01-01

223

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

International Nuclear Information System (INIS)

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

224

Reconstruction of the Stefan–Boltzmann coefficients in a heat-transfer process  

International Nuclear Information System (INIS)

In this paper, we investigate an inverse problem of determining the coefficients within the framework of Stefan–Boltzmann radiation boundary conditions for the heat-transfer process in a material. A mathematical formulation for the forward and inverse problems is introduced and the uniqueness of the inverse problem is proved. The finite-difference method is utilized for the discretization of the forward problem. Based on our analysis, we propose a fast-reconstruction method for solving the inverse problem, which can be easily realized in practice. Some regularization techniques are implemented to overcome the ill-posedness of the problem. Numerical simulation shows that our reconstruction method is stable and effective. (paper)

2012-04-01

225

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)

2007-03-01

226

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

227

Determination of heat transfer coefficients at metal/chill interface in the casting solidification process  

Science.gov (United States)

The present work focuses on the determination of interfacial heat transfer coefficients (IHTCs) between the casting and metal chill during casting solidification. The proposed method is established based on the least-squares technique and sequential function specification method and can be applied to calculate heat fluxes and IHTCs for other alloys. The accuracy and stability of the method has been investigated by using a typical profile of heat fluxes simulating the practical conditions of casting solidification. In the test process, the effects of various calculation parameters in the inverse algorithm are also analyzed. Moreover, numerically calculated and experimental results are compared by applying the determined IHTCs into the forward heat conduction model with the same boundary conditions. The results show that the numerically calculated temperatures are in good agreement with those measured experimentally. This confirms that the proposed method is a feasible and effective tool for determination of the casting-mold IHTCs.

Zhang, Liqiang; Li, Luoxing

2013-08-01

228

Electrohydrodynamic instabilities on a liquid anode displaying an anomalous surface tension coefficient  

International Nuclear Information System (INIS)

In the search for a deeper understanding of the factors governing the stability of liquid metal field-ion emitters, the behaviour of a liquid anode with an anomalous surface tension coefficient is studied. The main parameter in this experimental study is the emitter temperature. At the conclusion of the work an important result emerged: apart from the surface tension coefficient, space-charge effects constitute a major factor influencing emitter stability

2003-12-01

229

Flux surface averaging of the diffusion coefficient in electron cyclotron resonance heating  

International Nuclear Information System (INIS)

The single particle model has been used to describe electron cyclotron resonance heating. Fielding's (1980) method of calculating the diffusion coefficient has been simplified and extended to include the effect of finite beam width. It is shown how this effect and the effect of the rotational transform lead to a spreading of the resonance over a wider class of particles and how the diffusion coefficient should be averaged over a magnetic surface or surfaces. (author)

1986-01-01

230

Effects of temperature-dependent molecular absorption coefficients on the thermal infrared remote sensing of the earth surface  

Science.gov (United States)

The effect of temperature-dependent molecular absorption coefficients on thermal infrared spectral signatures measured from satellite sensors is investigated by comparing results from the atmospheric transmission and radiance codes LOWTRAN and MODTRAN and the accurate multiple scattering radiative transfer model ATRAD for different atmospheric profiles. The sensors considered include the operational NOAA AVHRR and two research instruments planned for NASA's Earth Observing System (EOS): MODIS-N (Moderate Resolution Imaging Spectrometer-Nadir-Mode) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). The difference in band transmittance is as large as 6 percent for some thermal bands within atmospheric windows and more than 30 percent near the edges of these atmospheric windows. The effect of temperature-dependent molecular absorption coefficients on satellite measurements of sea-surface temperature can exceed 0.6 K. Quantitative comparison and factor analysis indicate that more accurate measurements of molecular absorption coefficients and better radiative transfer simulation methods are needed to achieve SST accuracy of 0.3 K, as required for global numerical models of climate, and to develop land-surface temperature algorithms at the 1-K accuracy level.

Wan, Zhengming; Dozier, Jeff

1992-01-01

231

Effect of heat transfer coefficient on sheath and fuel centreline temperatures in SCWRS  

International Nuclear Information System (INIS)

SuperCritical Water-cooled nuclear Reactors (SCWRs) utilize light water above the pseudocritical point as a reactor coolant. This Generation IV reactor concept is currently in its preliminary design phase. This paper discusses the variables that influence heat transfer from the fuel. The coolant Heat Transfer Coefficient (HTC). Axial Heat Flux Profile (AHFP), sheath (clad) geometry and fuel thermal conductivity all impact the sheath and fuel centreline temperatures. The presented analysis utilizes the most recent HTC correlation developed for supercritical water, the Mokry et al. correlation (2009). The proposed sheath geometry is based on smaller diameter fuel elements than that of the current design to accommodate more fuel rods. Both uniform and cosine AHFPs, at average channel power, are applied. The results presented describe a sensitivity analysis of the effect of incrementing the HTC on sheath and fuel centreline temperatures. With a uniform AHFP and increasing HTC increments from 50 - 200% HTC the average temperature difference compared to 100% HTC are decreases from 13 to -18%. With a cosine AHFP and HTC incremented from 50 - 200% HTC the average temperature difference compared to 100% HTC have the range of 20 to -10%. (author)

2011-10-24

232

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

2008-01-01

233

Oxygen transfer with circulation flow rate in unbaffled surface aerator  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Circulation flow rate and vortex in unbaffled surface aeration systems are interrelated. These properties exert a profound effect on the performance of the surface aeration systems affecting the oxygen transfer process. This work develops the scale up criteria for oxygen transfer rate based on the circulation flow rate. A relationship between circulation flow rate and vortex depth in surface aerators has been also developed. ????????? ?????????? ?????? ? ???...

Kumar, Bimlesh; Tamphasana Devi, Thiyam

2012-01-01

234

Free-stream turbulence effect on the heat (mass) transfer characteristics on a turbine rotor surface  

International Nuclear Information System (INIS)

The heat (mass) transfer characteristics on the blade surface of a first-stage turbine rotor cascade has been investigated by employing the naphthalene sublimation technique. A four-axis profile measurement system is employed for the measurements of the local heat (mass) transfer coefficient on the curved blade surface. The experiments are carried out for two free-stream turbulence intensities of 1.2% and 14.7%. The high free-stream turbulence results in more uniform distributions of heat load on the both pressure and suction surfaces and in an early boundary-layer separation on the suction surface. The heat (mass) transfer enhancement on the suction surface due to the endwall vortices is found to be relatively small under the high free-stream turbulence

2004-04-28

235

Pattern recognition of surface electromyography signal based on wavelet coefficient entropy  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper introduced a novel, simple and ef-fective method to extract the general feature of two surface EMG (electromyography) signal patterns: forearm supination (FS) surface EMG signal and forearm pronation (FP) surface EMG signal. After surface EMG (SEMG) signal was decomposed to the fourth resolution level with wavelet packet transform (WPT), its whole scaling space (with frequencies in the interval (0Hz, 500Hz]) was divided into16 frequency bands (FB). Then wavelet coefficient entropy ...

Xiao Hu; Ying Gao; Wai-Xi Liu

2009-01-01

236

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.

2012-01-01

237

Heat/Mass transfer measurement on concave surface in rotating jet impingement  

International Nuclear Information System (INIS)

The objective of this paper is to investigate the heat/mass transfer characteristics on a concave surface for rotating impinging jets. The jet with Reynolds number of 5,000 is applied to the concave surface and the flat surface, respectively. The rotating experiments have been carried out at the rotating speed of 560RPM which is corresponding to Ro number of 0.075. The two jet orientation (front and trailing orientation) are considered. Detailed heat/mass transfer coefficients on the target plate were measured using a naphthalene sublimation method. The result indicates that the rotation leads to change in local heat/mass transfer distributions and the slight increase in the Sh level. The front orientation induces asymmetric Sh distributions, whereas the trailing orientation shows the shifted heat/mass transfer feature due to rotation-induced flow behavior. The crossflow effect on heat/mass transfer is also observed as the stream wise direction increases. Compared to flat surface, the heat/mass transfer on the concave surface is enhanced with increasing the spanwise direction due to the curvature effect, providing the higher averaged Sh value. It is proved that the difference of surface geometry affects somewhat the local and averaged heat/mass transfer regardless of rotation condition

2008-10-01

238

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.)

239

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

International Nuclear Information System (INIS)

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

240

Heat transfer coefficients during two-phase, gas-liquid flow in a circular tube under microgravity conditions  

Science.gov (United States)

A two-phase, two-component flow test loop was flown on-board NASA's KC-135 zero-g aircraft in October 1992. During the flights, flow regime, pressure gradient, and heat transfer data were simultaneously gathered for a water-air mixture in vertical, co-current, upward flow through a circular tube with a diameter of 9.53 mm. The range of flow rates studied consisted of superficial liquid velocities from 0.1 to 3.0 m/s and superficial gas velocities between 0.2 and 17 m/s. Heat transfer measurements taken during micro-g were compared with heat transfer data gathered at 1-g with the same test loop. This comparison indicated that at low liquid and gas velocities heat transfer coefficients at 1-g were up to 20 percent greater than those measured in micro-g. At higher liquid or gas velocities, this trend was reversed, and microgravity flows yielded heat transfer coefficients approximately 10 percent higher than the corresponding 1-g flows. The greatest difference in heat transfer between the two gravity levels occurred during slug and annular flows at micro-g, where churn-type flows existed at 1-g. However, it was found that a change in the flow regime was not totally responsible for this difference in heat transfer coefficients.

Rite, Raymond W.; Rezkallah, Kamiel S.

1993-07-01

 
 
 
 
241

Rhodium self-powered detectors transfer regime influence on fuel and emitter material depletion correction coefficients in RBMK-1000 reactors  

International Nuclear Information System (INIS)

The influence of the rhodium self-powered detector transition regime in the RBMK-1000 reactor on correction coefficients taking into account fuel and emitter material burnups is considered. It is shown that application of the known correction coefficients dependence on burnup after the detector transfer into another fuel channel is possible only taking into account the channel power generation and time-integrated current produced by the detector for the moment of transition. 4 refs., 3 figs

1994-06-01

242

Measurement of subcooled boiling pressure drop and local heat transfer coefficient in horizontal tube under LPLF conditions  

International Nuclear Information System (INIS)

Highlights: ? Measured subcooled boiling pressure drop and local heat transfer coefficient in horizontal tubes. ? Infra-red thermal imaging is used for wall temperature measurement. ? Developed correlations for pressure drop and local heat transfer coefficient. -- Abstract: Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (loss of coolant accidents). In the present work, local heat transfer coefficient and pressure drop are measured in a horizontal tube under LPLF conditions of subcooled boiling. Geometrical parameters covered in this study are diameter (5.5 mm, 7.5 mm and 9.5 mm) and length (550 mm, 750 mm and 1000 mm). The operating parameters varied are mass flux (450–935 kg/m2 s) and inlet subcooling (29 °C, 50 °C and 70 °C). Infra-red thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under subcooled boiling conditions as a function of Boiling number (Bo) and Jakob number (Ja) is obtained. Correlation for single phase heat transfer coefficient in the thermal developing region is presented as a function of Reynolds number (Re), Prandtl number (Pr) and z/d (ratio of axial length of the test section to diameter). Correlation for two phase heat transfer coefficient under subcooled boiling condition is developed as a function of boiling number (Bo), Jakob number (Ja) and Prandtl number (Pr)

2013-02-01

243

Measurement of subcooled boiling pressure drop and local heat transfer coefficient in horizontal tube under LPLF conditions  

Energy Technology Data Exchange (ETDEWEB)

Highlights: ? Measured subcooled boiling pressure drop and local heat transfer coefficient in horizontal tubes. ? Infra-red thermal imaging is used for wall temperature measurement. ? Developed correlations for pressure drop and local heat transfer coefficient. -- Abstract: Horizontal flow is commonly encountered in boiler tubes, refrigerating equipments and nuclear reactor fuel channels of pressurized heavy water reactors (PHWR). Study of horizontal flow under low pressure and low flow (LPLF) conditions is important in understanding the nuclear core behavior during situations like LOCA (loss of coolant accidents). In the present work, local heat transfer coefficient and pressure drop are measured in a horizontal tube under LPLF conditions of subcooled boiling. Geometrical parameters covered in this study are diameter (5.5 mm, 7.5 mm and 9.5 mm) and length (550 mm, 750 mm and 1000 mm). The operating parameters varied are mass flux (450–935 kg/m{sup 2} s) and inlet subcooling (29 °C, 50 °C and 70 °C). Infra-red thermography is used for the measurement of local wall temperature to estimate the heat transfer coefficient in single phase and two phase flows with water as the working medium at atmospheric pressure. Correlation for single phase diabatic pressure drop ratio (diabatic to adiabatic) as a function of viscosity ratio (wall temperature to fluid temperature) is presented. Correlation for pressure drop under subcooled boiling conditions as a function of Boiling number (Bo) and Jakob number (Ja) is obtained. Correlation for single phase heat transfer coefficient in the thermal developing region is presented as a function of Reynolds number (Re), Prandtl number (Pr) and z/d (ratio of axial length of the test section to diameter). Correlation for two phase heat transfer coefficient under subcooled boiling condition is developed as a function of boiling number (Bo), Jakob number (Ja) and Prandtl number (Pr)

Baburajan, P.K. [Atomic Energy Regulatory Board, Mumbai (India); Bisht, G.S. [Indian Institute of Technology, Bombay (India); Gupta, S.K. [Atomic Energy Regulatory Board, Mumbai (India); Prabhu, S.V., E-mail: svprabhu@iitb.ac.in [Indian Institute of Technology, Bombay (India)

2013-02-15

244

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

245

Determination of heat transfer coefficients at condensation in a vertical tube on the basis of two-dimensional calculations  

Energy Technology Data Exchange (ETDEWEB)

In development of one-dimensional engineering methods of film-type condensation analysis to complete the momentum, energy and mass equations, it is necessary to know local coefficients of friction and heat and mass transfer on the liquid-solid, gas-liquid interfaces. The data of numerical solution on the two-dimensional condensation model in a vertical tube are presented. The results have been approximated by algebraic relationships for heat and mass transfer local coefficient calculations. The obtained dependences have been recommended for using in one-dimensional models. The comparison of one- and two-dimensional models has been carried out.

Volodin, V.I.; Mikhalevich, A.A.; Sinkevich, A.E.

1983-01-01

246

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

247

EXPERIMENTAL STUDY ON HEAT TRANSFER COEFFICIENT AND FRICTION FACTOR OF Al2O3 NANOFLUID IN A PACKED BED COLUMN  

Directory of Open Access Journals (Sweden)

Full Text Available The forced convection heat transfer coefficient and friction factor are determined for the flow of water and nanofluid in a vertical packed bed column. The analysis is undertaken in the laminar and transition Reynolds number range. The column is filled with spherical glass beads as the bed material. The heat transfer coefficients with Al2O3 nanofluid increased by 12% to 15% with the increase of volume concentration from 0.02% to 0.5% compared with water. The experimental values of axial temperature are in good agreement with the NTU-? method proposed by Schumann’s model.

G. Srinivasa Rao

2011-12-01

248

Determination of surface tension coefficient of liquids by diffraction of light on capillary waves  

International Nuclear Information System (INIS)

This paper describes a simple technique for determining the coefficient of the surface tension of liquids, based on laser light diffraction on capillary waves. Capillary waves of given frequency are created by an exciter needle acting on the surface of liquid and represent a reflective diffraction grating, the constant of which (the wavelength of capillary waves) can be determined based on a known incidence angle of light (grazing angle). We obtain the coefficient of the surface tension of liquids by applying the dispersion relation for capillary waves and analyze the difficulties that arise when setting up and conducting the experiment in detail. (paper)

2012-11-01

249

Experimental study on the influence of SO2 gas injection to pure liquids on pool boiling heat transfer coefficients  

Science.gov (United States)

SO2 gas is injected into the different pure liquids using new innovative method via meshed tubes. Many experiments have been performed to investigate the influence of gas injection process on the pool boiling heat transfer coefficient of pure liquids around the horizontal cylinder at different heat fluxes up to 114 kW m-2. Results demonstrate that presence of SO2 gas into the vapor inside the bubbles creates a mass transfer driving force between the vapor phase inside the formed bubbles and liquid phase and also between the gas/liquid interfaces. Local turbulences and agitations due to the gas injection process around the nucleation sites leads the pool boiling heat transfer coefficient to be dramatically enhanced. Besides, some of earlier well-known correlations were unable to obtain the reasonable values for the pool boiling heat transfer coefficients in this particular case. Therefore, the most accurate correlation among the examined correlations was modified to estimate the pool boiling heat transfer coefficient of pure liquids. Experimental data were in a good agreement with those of obtained by the new modified correlation with absolute average deviation of 10 %.

Sarafraz, M. M.; Hormozi, F.; Peyghambarzadeh, S. M.; Salari, E.

2014-06-01

250

Determination of unidirectional heat transfer coefficient during unsteady-state solidification at metal casting-chill interface  

International Nuclear Information System (INIS)

In this study, the interfacial heat transfer coefficient (IHTC) for vertically upward unidirectional solidification of a eutectic Al-Si casting on water cooled copper and steel chills was measured during solidification. A finite difference method (FDM) was used for solution of the inverse heat conduction problem (IHCP). Six computer guided thermocouples were connected with the chill and casting, and the time-temperature data were recorded automatically. The thermocouples were placed, located symmetrically, at 5 mm, 37.5 mm and 75 mm from the interface. As the lateral surfaces are very well heat isolated, the unidirectional solidification process starts vertically upward at the interface surface. The measured time-temperature data files were used by a FDM using an explicit technique. A heat flow computer program has been written to estimate the transient metal-chill IHTC in the IHCP. The experimental and calculated temperatures have shown excellent agreement. The IHTC during vertically upward unidirectional solidification of an Al-Si casting on copper and steel chills have varied between about 19-9.5 kW/m2 K and 6.5-5 kW/m2 K, respectively

2006-01-01

251

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 SciELO Brazil | Language: English 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 prop [...] osal. 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.

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

252

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.

2009-09-01

253

Some investigations on the enhancement of boiling heat transfer from planer surface embedded with continuous open tunnels  

Energy Technology Data Exchange (ETDEWEB)

Boiling heat transfer from a flat surface can be enhanced if continuous open tunnel type structures are embedded in it. Further, improvement of boiling heat transfer from such surfaces has been tried by two separate avenues. At first, inclined tunnels are embedded over the solid surface and an effort is made to optimize the tunnel inclination for boiling heat transfer. Surfaces are manufactured in house with four different inclinations of the tunnels with or without a reentrant circular pocket at the end of the tunnel. Experiments conducted in the nucleate boiling regime showed that 45 deg inclination of the tunnels for both with and without base geometry provides the highest heat transfer coefficient. Next, active fluid rotation was imposed to enhance the heat transfer from tunnel type surfaces with and without the base geometry. Rotational speed imparted by mechanical stirrer was varied over a wide range. It was observed that fluid rotation enhances the heat transfer coefficient only up to a certain value of stirrer speed. Rotational speed values, beyond this limit, reduce the boiling heat transfer severely. A comparison shows that embedding continuous tunnel turns out to be a better option for the increase of heat transfer coefficient compared to the imposition of fluid rotation. But the behavior of inclined tunnels under the action of fluid rotation is yet to be established and can be treated as a future scope of the work. (author)

Das, A.K.; Das, P.K.; Saha, P. [Department of Mechanical Engineering, Indian Institute of Technology, Kharagpur 721 302 (India)

2010-11-15

254

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

2009-11-01

255

Method of oscillating surface for the determination of the mutual friction coefficient B in superfluids  

International Nuclear Information System (INIS)

A method to determine mutual friction coefficient between normal and superfluid components in superfluid helium-3 has been described. To increase the accuracy of measurement of mutual friction coefficient B the method of oscillation of coasxial cylindric surfaces is realized, in which a multiple intensification of the effect of mutual friction between normal and superfluid components takes place as compared with a hollow cylinder. Results of the experiment carried out for He-2 are presented

1984-01-01

256

Effect of surface roughness on boiling heat transfer  

International Nuclear Information System (INIS)

In boiling heat transfer, many vapors are generated on the heating surface in high heat flux region. If many vapors are stayed on the heating surface, they are collaborated and developed to a vapor film. As the result, the heating surface is covered with the vapor film and the critical heat flux would be decreased. On the rough heating surface, boiling bubbles do not detach completely from the surface. In this case, the fluid state on the surface is considered as a kind of non-equilibrium two phase flow. Authors investigated experimentally the effect of surface roughness on the boiling heat transfer. The heating surfaces with lattice grooves which had different depth and width were employed as typical examples of surface roughness, and the grooving angle was approximately 60 degrees at the top. The authors obtained experimental results on water boiling for the rough heating surface that the critical heat flux decreased below a half value of the usual critical heat flux and the heat flux increased monotonously with the increasing of superheat of the heating surface under some condition of heating surface. The roughness of the heating surface in boiling heat transfer gives considerably an effect on the critical heat flux and the characteristics of heat transfer. The experimental results are different from the common knowledge about boiling heat transfer for the surface roughness. According to the present research, authors need some additional treatment to the surface of nuclear fuel elements and the design of electronic circuits etc

1989-03-23

257

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

258

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

International Nuclear Information System (INIS)

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

259

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

2009-02-01

260

Mass Transfer Coefficient During Cathodic Protectionof Low Carbon Steel in Seawater  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this research is to calculate mass transfer coefficient, kd, during cathodic protection of low carbon steel in neutral seawater (3.5% W/V NaCl in distilled water with pH = 7. Two types of cathodic protection were used:First: Sacrificial anode cathodic protection (SACP were a pipeline of steel carrying seawater using zinc as a sacrificial anode and with variable temperatures ranged (0 ? 45oC and volumetric flow rate ranged (5 ? 900 lit/hr. It was found that the kd increases with increasing temperature and volumetric flow rate of seawater, where kd ranged (0.24×10-6 ? 41.6×10-6 m/s.Second: Impressed current cathodic protection (ICCP technique adopting a rotating vertical steel cylinder in seawater with variable temperatures ranged (0 ? 45oC and rotating velocity ranged (0 ? 400 rpm. It was found that the kd increases with increasing temperature and rotating velocity, where kd ranged (7.25×10-6 ? 36.82×10-6 m/s.

Ameel Mohammed Rahman

2009-01-01

 
 
 
 
261

Heat and mass transfer to flowing bodies of surface water  

International Nuclear Information System (INIS)

The most important limiting quantities for heat transfer from a river to its environment are the thermal radiation, the free convection and the forced convection due to wind. For a sure preliminary calculation of the heat emission of a flowing body of water it is necessary to know exactly the decisive heat- and mass transfer coefficients and their dependence on wind velocity. Measurements have been effected at a power plant channel in Pleidelsheim/Neckar. The measuring technique, arrangement of the measuring points and measuring devices are shown in detail as well as the theoretical basis for the analysis of the measurements. Balancing calculations lead to relations representing, in the form of extended exponential functions, the dependence of the transfer coefficients on wind velocity. As against the transfer coefficients so far used for calculating the thermal load plans, much higher values have been obtained. This is of considerable practical importance insofar as a flowing water obviously emits the received foreign heat quicker than assumed until now. Because of the importance of the radiation a new intermittent measuring method has been developed enabling the determination of the different radiation fluxes as well as the heat- and mass transfer coefficients. (orig.)

1981-01-01

262

Ultrasonic Heat Transfer Enhancement with Obstacle in Front of Heating Surface  

Science.gov (United States)

Heat transfer enhancement using a horn-type transducer was carried out in the natural convection region while a flat plate was used as a wall-like obstacle in front of the heating surface. Three types of plate were used as obstacles: acrylic, aluminum, and Styrofoam. A horn tip of 6 mm diameter and 60.7 kHz was used as the ultrasonic transducer. The acoustic cavitation jet induced by the ultrasonic vibration exhibited the same tendency as the axisymmetric free jet. The acoustic jet from the horn tip was shut out by the flat plate; however, the ultrasound passed through the flat plate and transferred the flow effect and agitation effect to the area behind the plate. By applying ultrasonic vibration, the heat transfer coefficient of the heating surface behind the flat plate was increased by up to threefold. The heat transfer coefficient decreased as the thickness of the flat plate increased. The heat transfer coefficient was the highest for the acrylic plate, then the aluminum plate, and lowest for the Styrofoam plate.

Nomura, Shinfuku; Nakagawa, Masafumi; Mukasa, Shinobu; Toyota, Hiromichi; Murakami, Koichi; Kobayashi, Ryousuke

2005-06-01

263

Relation between the temperature coefficient of surface tension and phase diagrams  

Science.gov (United States)

An equation determining the relation between the temperature coefficient of surface tension and crystallization temperature was obtained. The equation was substantiated experimentally for solutions of NaOH and ZnCl2. The rule governing the alternation of structures in phase diagrams was found. A relation between phase diagram structures and structures in adsorbed surface layers of liquid solutions at microconcentrations of surface-active components was derived.

Koliverdov, V. F.

2010-08-01

264

Bubble enhanced heat transfer from a vertical heated surface  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A rising bubble in a liquid can greatly enhance heat transfer from heated surfaces by acting like a bluff body, displacing fluid as it moves and via the wake generated by the bubble, increasing the mixing of the liquid. The current research quantifies the effect a single free rising ellipsoidal air bubble has on heat transfer from a vertical heated block immersed in water. By measuring the time varying heat transfer and tracking the bubble dynamics, further understanding of the heat transfer ...

Murray, Darina Bridget

2008-01-01

265

Surface charge and hydrodynamic coefficient measurements of Bacillus subtilis spore by optical tweezers.  

Science.gov (United States)

In this work we report on the simultaneous measurement of the hydrodynamic coefficient and the electric charge of single Bacillus subtilis spores. The latter has great importance in protein binding to spores and in the adhesion of spores onto surfaces. The charge and the hydrodynamic coefficient were measured by an accurate procedure based on the analysis of the motion of single spores confined by an optical trap. The technique has been validated using charged spherical polystyrene beads. The excellent agreement of our results with the expected values demonstrates the quality of our procedure. We measured the charge of spores of B. subtilis purified from a wild type strain and from two isogenic mutants characterized by an altered spore surface. Our technique is able to discriminate the three spore types used, by their charge and by their hydrodynamic coefficient which is related to the hydrophobic properties of the spore surface. PMID:24583259

Pesce, Giuseppe; Rusciano, Giulia; Sasso, Antonio; Isticato, Rachele; Sirec, Teja; Ricca, Ezio

2014-04-01

266

Heat transfer coefficients and pressure drops in a reactor channel in a one-phase flow system  

International Nuclear Information System (INIS)

Approaches to heat transfer coefficients and pressure drop measurements in a one-phase flow and its comparison to theory is described. A test section consisting of a tube of reactor channel size to acquire experiences in design, construction, operation and know-how on thermocouples in stalling is assembled. Results have been analyzed

1986-01-01

267

Determination of "1"3"7Cs transfer coefficients in soil-plant system at nuclear power plant sites  

International Nuclear Information System (INIS)

In the surroundings of the Mochovce and Dukovany nuclear power plants samples were taken of soils and some plants, namely wheat, barley, clover and lucerne, which were treated and then measured with a Ge(Li) detector. The found transfer coefficients and discrimination factors for "1"3"7Cs are tabulated for both localities. (E.S.)

1985-01-01

268

Determination of condensing heat transfer coefficients and two-phase flow regimes for dichlorotetrafluoroethane refrigerant (R-114)  

International Nuclear Information System (INIS)

Experimental condensing heat transfer coefficients for R-114 flowing in a horizontal tube were compared with those calculated by the classical Nusselt correlation and with a new prediction method of Rohsenow. It was determined that the Rohsenow method provides satisfactory agreement with the experimental data and that the coefficients calculated by the Nusselt correlation were much too low. A concurrent study of flow regimes was also made by observing the flow patterns in a glass section just downstream of the condensing section. The regimes observed agree reasonably well with a Baker map that was previously developed from theoretical considerations. An improved correlation was also developed for estimating the inside heat transfer coefficients for water in an annulus

1977-01-01

269

Spray cooling with formation of liquid film. Distribution of heat-transfer coefficient in high-temperature region. Ekimaku keisei wo tomonau funmu reikyaku ni kansuru kenkyu. Koon'iki ni okeru netsudentatsuritsu bunpu  

Energy Technology Data Exchange (ETDEWEB)

To enhance the strength of steel, hot rolled steel is sometimes cooled down to the specific temperature by water spray. In this study, concerning the uniform temperature distribution of a steel plate, a test on spray cooling with liquid film formation was performed, and the distribution of heat transfer coefficient in a high-temperature region along the large plate surface was investigated. The water was sprayed from a nozzle to form two-dimensional spray flow from the upper surface of a 19mm-thick stainless steel plate heated at the specific temperature. Deep grooves were made on the backside of the test plate to prevent heat transfer in the width direction of the cooling surface. Spray cooling in the high-temperature region shows different heat transfer characters in the area right under the spray from those in the surrounding area. The local heat transfer coefficient in the former area decreases rapidly with decreasing local droplet flow rate. Also, the minimum temperature of the high-temperature region increases in accordance with the propagation of the liquid film front edge. In the latter area, the local heat transfer coefficient and the minimum temperature of the high-temperature region do not depend on the distance from the area right under the spray, and the local heat transfer coefficient is dominated by the total spray flow rate. 12 refs., 12 figs.

Kim, Y. (The University of Tokyo, Tokyo (Japan)); Nisio, S.; Okubo, H. (The University of Tokyo, Tokyo (Japan). Institute of Industrial Science)

1994-06-25

270

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

271

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

International Nuclear Information System (INIS)

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)

2000-06-01

272

Influence of surface modification on friction coefficient of the titanium-elastomer couple.  

Science.gov (United States)

This paper presents the results of a study of the friction coefficient of titanium-elastomer couple. The study was carried out with a view to potential future utilization of its results for constructing retentive elements of implanted prostheses. Changes in the friction force were recorded while removing titanium specimens placed between two silicone counter specimens made of Ufi Gel. The influence of the titanium specimen movement speed in relation that of to the counter specimens and the influence of clamping force on the friction force were assessed. Additionally, the surface roughness of titanium specimens differed; in one case, titanium was coated with polyethylene. The effect of introducing artificial saliva between the cooperating surfaces on the friction force and friction coefficient was analyzed as well. Based on the characteristics recorded, the possibilities of shaping the friction coefficient have been assessed, since it is the friction coefficient that determines effective operation of a friction couple through increasing the titanium specimen roughness. The artificial saliva being introduced between the specimens reduces considerably the friction coefficient through a change of the phenomenon model. An increase in the pressure force for the specimens of high roughness entails a reduction of the friction coefficient. The study carried out allows us to identify the roughness parameters, which in turn will enable obtaining the prescribed retention force for friction/membrane couplings. PMID:18421939

Chladek, Wies?aw; Hadasik, Eugeniusz; Chladek, Grzegorz

2007-01-01

273

Comparison between one-dimensional uncoupled and convection-conduction conjugated approaches in finned surface heat transfer  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This work studies the forced convection problem in internal flow between concentric annular ducts, with radial fins at the internal tube surface. The finned surface heat transfer is analyzed by two different approaches. In the first one, it is assumed one-dimensional heat conduction along the internal tube wall and fins, with the convection heat transfer coefficient being a known parameter, determined by an uncoupled solution. In the other way, named conjugated approach, the mathematical mode...

Andrade, Cla?udia R.; Zaparoli, Edson L.

2000-01-01

274

Confirmation of selected milk and meat radionuclide transfer coefficients. Third technical progress report, September 1984-August 1985  

International Nuclear Information System (INIS)

The goat milk transfer coefficient of Tc administered as TcO4- was found to be 20 to 40 times that of Tc administered in a reduced form. The fraction of Tc, as TcO4-, transferred from gut to blood was approximately 6 to 10 times that of reduced Tc. The milk transfer coefficient of Tc administered as TcO4- was 6 to 8 times greater for goats than cows. The fraction of Tc, as TcO4-, absorbed from the gut by cows, however, was approximately twice that absorbed by goats. The mean time for loss of Tc in cows' milk based on the average values plotted in Figure 2 was approximately 10 hours. The fraction of Tc, administered as TcO4-, absorbed from blood to mammary gland by cows was estimated to be approximately 2% that of goats. 4 refs., 15 tabs

1985-01-01

275

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.

Maciejewska Beata

2012-04-01

276

Experimental determination of convective heat transfer coefficients in the separated flow region of the Space Shuttle Solid Rocket Motor  

Science.gov (United States)

A series of cold flow heat transfer tests was conducted with a 7.5-percent scale model of the Space Shuttle Rocket Motor (SRM) to measure the heat transfer coefficients in the separated flow region around the nose of the submerged nozzle. Modifications were made to an existing 7.5 percent scale model of the internal geometry of the aft end of the SRM, including the gimballed nozzle in order to accomplish the measurements. The model nozzle nose was fitted with a stainless steel shell with numerous thermocouples welded to the backside of the thin wall. A transient 'thin skin' experimental technique was used to measure the local heat transfer coefficients. The effects of Reynolds number, nozzle gimbal angle, and model location were correlated with a Stanton number versus Reynolds number correlation which may be used to determine the convective heating rates for the full scale Space Shuttle Solid Rocket Motor nozzle.

Whitesides, R. Harold; Majumdar, Alok K.; Jenkins, Susan L.; Bacchus, David L.

1990-01-01

277

Studies on soil to grass transfer factor (Fv) and grass to milk transfer coefficient (Fm) for cesium in Kaiga region  

International Nuclear Information System (INIS)

Detailed studies were carried out to establish site-specific soil to grass transfer factors (Fv) and grass to cow milk transfer coefficients (Fm) for radioactive cesium (137Cs) and stable cesium (Cs) for Kaiga region, where a nuclear power station has been in operation for more than 10 years. The study included adopted cows, cows of local farmers, and cows from the dairy farm. A grass field was developed specifically for the study and 2 local breed cows were adopted and allowed to graze in this grass field. The soil and grass samples were collected regularly from this field and analyzed for the concentrations of 137Cs and stable Cs to evaluate the soil to grass Fv values. The milk samples from the adopted cows were analyzed for the 137Cs and stable Cs concentrations to evaluate Fm values. For comparison, studies were also carried out in dominant grazing areas in different villages around the nuclear power plant and the cows of local farmers which graze in these areas were identified and milk samples were collected and analyzed regularly. The geometric mean values of Fv were found to be 1.1 × 10?1 and 1.8 × 10?1 for 137Cs and stable Cs, respectively. The Fm of 137Cs had geometric mean values of 1.9 × 10?2 d L?1 and 4.6 × 10?2 d L?1, respectively, for adopted Cows 1 and 2; 1.7 × 10?2 d L?1 for the cows of local farmers, and 4.0 × 10?3 d L?1 for the dairy farm cows. The geometric mean values of Fm for stable Cs were similar to those of 137Cs. The Fm value for the dairy farm cows was an order of magnitude lower than those for local breed cows. The Fm values observed for the local breed cows were also an order of magnitude higher when compared to the many values reported in the literature and in the IAEA publication. Possible reasons for this higher Fm values were identified. The correlation between Fv and Fm values for 137Cs and stable Cs and their dependence on the potassium content (40K and stable K) in the soil and grass were also studied. In order to estimate the ingestion dose accurate data of the dietary habits of the population was necessary and this data was collected through a well planned demographic survey. The internal doses to a child due to the ingestion of 137Cs along with the milk of the local cows and from the dairy farm were found to be 0.29 ?Sv y?1 and 0.04 ?Sv y?1,while that to an adult were 0.39 ?Sv y?1 and 0.05 ?Sv y?1, respectively. -- Highlights: • This is a detailed study on Fv and Fm for 137Cs and stable Cs around the Kaiga nuclear power plant, India. • The geometric mean values of Fv were found to be 1.1 × 10?1 and 1.8 × 10?1 for 137Cs and stable Cs, respectively. • The Fm value for 137Cs for the local breed cows was estimated to be 2.4 × 10?2 d L?1. • The Fm value for dairy farm cows (4.0 × 10?3 d L?1) was an order of magnitude lower than those for local breed cows. • The reasons for the higher Fm values for 137Cs for the local breed cows are identified

2013-10-01

278

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

2009-02-01

279

Studying heat transfer enhancement for water boiling on a surface with micro- and nanorelief  

Science.gov (United States)

We present the results from a study of heat transfer enhancement for bulk water boiling at atmospheric pressure on a surface with micro- and nanorelief, including a relief formed from silicon carbide and aluminum oxide nanoparticles. Horizontally oriented steel tube 1.2 mm in diameter and copper plate 15 × 3 mm in size were selected as test sections. The process was recorded by means of a video camera, and the values of heat transfer, critical heat fluxes, and contact angles were measured. The use of surface with micro- and nanorelief makes it possible to obtain a significantly higher critical heat flux and boiling heat transfer coefficient owing to a change of surface wettability. The results of investigations can find use in compact heat exchangers, refrigerating plants, heat pipes, in the mirrors of high-capacity lasers, in the targets and resonators of charged particle accelerators and for external cooling of reactor vessels under emergency conditions.

Kuzma-Kichta, Yu. A.; Lavrikov, A. V.; Shustov, M. V.; Chursin, P. S.; Chistyakova, A. V.; Zvonarev, Yu. A.; Zhukov, V. M.; Vasil'eva, L. T.

2014-03-01

280

Data Qualification Report For DTN: MO0012RIB00065.002, Parameter Values For Transfer Coefficients  

International Nuclear Information System (INIS)

A data-qualification evaluation was conducted on Reference Information Base (RIB) data set MOO0 12RIB00065.002, ''Parameter Values for Transfer Coefficients''. The corroborating data method was used to evaluate the data. This method was selected because it closely matches the literature-review method followed to select parameter values. Five criteria were considered when the corroborating method was used: adequacy of the corroborative literature, sufficiency of value-selection criteria, implementation of the selection criteria, documentation of the process, and whether the analysis was conducted in accordance with applicable quality assurance (QA) procedures. Three criteria were used when a literature review was not conducted: appropriate logic used to select parameters, documentation of the process, and whether the analysis was conducted in accordance with applicable QA procedures. The RIB data item, the associated Analysis and Model Report (AMR), the corroborative literature, and the results of an audit revision O/ICN--0 of the AMR were examined. All calculations and the selection process for all values were repeated and confirmed. The qualification team concluded: (1) A sufficient quantity of corroborative literature was reviewed and no additional literature was identified that should have been considered. (2) The selection criteria were sufficient and resulted in valid parameter values. (3) The process was well defined, adequately documented in the AMR, and correctly followed. (4) The analysis was developed in accordance with applicable QA procedures. No negative findings were documented that resulted in questions about the quality of the data. The qualification team therefore recommends that the qualification status of RIB data set MO0012RIB00065.002 be changed to qualified

2001-01-01

 
 
 
 
281

Heat and mass transfer characteristics of organic sorbent coated on heat transfer surface of a heat exchanger  

Energy Technology Data Exchange (ETDEWEB)

This paper describes heat and mass transfer characteristics of organic sorbent coated on heat transfer surface of a fin-tube heat exchanger. The experiments in which the moist air was passed into the heat exchanger coated with sorption material were conducted under various conditions of air flow rate (0.5-1.0 m/s) and the temperature of brine (14-20 C) that was the heat transfer fluid to cool the air flow in the dehumidifying process. It is found that the sorption rate of vapor is affected by the air flow rate and the brine temperature. Meanwhile, the attempt of clarifying the sorption mechanism is also conducted. Finally the average mass transfer coefficient of the organic sorbent coated on heat transfer surface of a fin-tube heat exchanger is non-dimensionalized as a function of Reynolds number and non-dimensional temperature, and it is found that the effect of non-dimensional temperature on them is larger than Reynolds number. (orig.)

Inaba, Hideo [Okayama University, Tsushima, Okayama (Japan); Komatsu, Fujio; Horibe, Akihiko; Haruki, Naoto [Okayama University, Graduate School of Natural Science and Technology, Tsushima, Okayama (Japan); Machida, Akito [Advanced Tech.Lab., Mayekawa Mfg. Co., Ltd., Moriya, Ibaraki (Japan)

2008-09-15

282

Effect of Lubricant Viscosity and Surface Roughness on Coefficient of Friction in Rolling Contact  

Directory of Open Access Journals (Sweden)

Full Text Available The main objective of this paper is to investigate the effect of surface roughness and lubricant viscosity on coefficient of friction in silicon nitride- steel rolling contact. Two samples of silicon nitride with two different values of surface roughness were tested against steel counter face. The test was performed on four ball tester in presence of lubricant with two different values of viscosity. Taguchi technique a methodology in design of experiment implemented to plan the experimentation and same is utilized to evaluate the interacting effect of surface roughness and lubricant viscosity. Analysis of experimental results presents a strong interaction between surface roughness and lubricant viscosity on coefficient of friction in rolling contact.

S.G. Ghalme

2013-12-01

283

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

284

Calculation of effective diffusion coefficient in even approximations of the surface pseudo source method  

Energy Technology Data Exchange (ETDEWEB)

The preference of even approximations of the surface pseudo source method for calculation of the diffusion coefficient is substantiated. The homogenization limit for the G{sub 0} approximation in the case of the cell size tending to zero is analytically proved.

Kovalishin, A. A., E-mail: kaa@adis.vver.kiae.ru; Laletin, N. I. [Russian Research Centre Kurchatov Institute (Russian Federation)

2011-12-15

285

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

286

Convective heat transfer from rough surfaces with two-dimensional ribs - transitional and laminar flow  

International Nuclear Information System (INIS)

Measurements of friction factor and heat transfer coefficients for two rods of 18.9 mm 0.D. with two-dimensional roughness, each in two different outer smooth tubes have been performed in turbulent and laminar flow. The turbulent flow results indicate that the flow was not thermally fully established, the isothermal data however agree reasonably well with our previously obtained general correlation. Laminar flow results can be correlated best when the Reynolds and Greatz numbers are evaluated at the temperature average between the temperature of the inner rod surface and of the outer smooth surface of the annulus, the average being weighted over the two surfaces. (orig.)

1978-01-01

287

Experimental study of the heat transfer characteristics of refrigerant mixture R-22/R-114 in the annulus of enhanced surface tubing  

International Nuclear Information System (INIS)

In this paper an experimental study of heat transfer characteristics of refrigerant mixture R-22/R-114 in the annuli of a horizontal enhanced surface tubing evaporator is presented. The enhanced surface tubing data showed a significant enhancement of the heat transfer compared to an equivalent smooth tube depending on the mixture's components and their concentrations. Correlations were proposed to predict the average heat transfer coefficients of R-22/R114 non-azeotropic refrigerant moisture flow boiling inside enhanced surface tubing

1991-01-01

288

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

289

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

2012-04-01

290

The Ohio State 1991 geopotential and sea surface topography harmonic coefficient models  

Science.gov (United States)

The computation is described of a geopotential model to deg 360, a sea surface topography model to deg 10/15, and adjusted Geosat orbits for the first year of the exact repeat mission (ERM). This study started from the GEM-T2 potential coefficient model and it's error covariance matrix and Geosat orbits (for 22 ERMs) computed by Haines et al. using the GEM-T2 model. The first step followed the general procedures which use a radial orbit error theory originally developed by English. The Geosat data was processed to find corrections to the a priori geopotential model, corrections to a radial orbit error model for 76 Geosat arcs, and coefficients of a harmonic representation of the sea surface topography. The second stage of the analysis took place by doing a combination of the GEM-T2 coefficients with 30 deg gravity data derived from surface gravity data and anomalies obtained from altimeter data. The analysis has shown how a high degree spherical harmonic model can be determined combining the best aspects of two different analysis techniques. The error analysis was described that has led to the accuracy estimates for all the coefficients to deg 360. Significant work is needed to improve the modeling effort.

Rapp, Richard H.; Wang, Yan Ming; Pavlis, Nikolaos K.

1991-01-01

291

The fuel to clad heat transfer coefficient in advanced MX-type fuel pins  

International Nuclear Information System (INIS)

Advanced fuels (mixed carbides, nitrides and carbonitrides) are characterised by a high thermal conductivity compared to that of oxide fuels (5 times greater) and their behaviour under irradiation (amount of swelling, fracture behaviour, restructuring) is far more sensitive to the design parameters and to the operating temperature than that of oxide fuels. The use of advanced fuels is therefore conditioned by the possibility of mastering the above phenomena, and the full exploitation of their favorable neutron characteristics depends upon a good understanding of the mutual relationships of the various parameters, which eventually affect the mechanical stability of the pin. By far the most important parameter is the radial temperature profile which controls the swelling of the fuel and the build-up of stress fields within the pin. Since the rate of fission gas swelling of these fuels is relatively large, a sufficient amount of free space has to be provided within the pin. This space originally appears as fabrication porosity and as fuel-to-clad clearance. Due to the large initial gap width and to the high fuel thermal conductivity, the range of the fuel operating temperatures is mainly determined by the fuel-to-clad heat transfer coefficient h, whose correct determination becomes one of the central points in modelling. During the many years of modelling activity in the field of oxide fuels, several theoretical models have been developed to calculate h, and a large amount of experimental data has been produced for the empirical adjustment of the parameters involved, so that the situation may be regarded as rather satisfactory. The analysis lead to the following conclusions. A quantitative comparison of experimental h-values with existing models for h requires rather sophisticated instrumented irradiation capsules, which permit the measurement of mechanical data (concerning fuel and clad) together with heat rating and temperatures. More and better well-instrumented irradiation experiments are necessary in order to make progress on this problem. The h-values are sensitive to changes in the linear heat rating and/or clad temperature. A quantitative comparison of experimental values of h with existing models requires capsule irradiations, in which temperatures, rating and also mechanical parameters are all recorded during irradiation

1979-12-01

292

Heat transfer coefficients and pressure drops during in-tube condensation of CO{sub 2}/DME mixture refrigerant  

Energy Technology Data Exchange (ETDEWEB)

Local heat transfer coefficients and pressure drops during condensation of pure Dimethyl Ether (DME) and non-azeotropic mixtures of CO{sub 2} and DME inside a horizontal smooth tube have been measured experimentally. The mass fractions of CO{sub 2} and DME in the mixtures have been varied as CO{sub 2}/DME (39/61, 21/79 mass%) and the refrigerant mass fluxes have been varied from 200 to 500 kg m{sup -2} s{sup -1}. The increase of mass fraction of CO{sub 2} in the mixture decreases the heat transfer coefficient and the pressure drop. At the high refrigerant mass flux, the effect of mass transfer resistance on the heat transfer is decreased. Existing prediction method for condensation of binary refrigerant mixtures, which considered the vapor core mass transfer resistance, has been used to predict the present experimental data. Changing of the two-phase frictional multiplier in that prediction method has improved the prediction of the present experimental data. (author)

Afroz, Hasan M.M. [Graduate School of Science and Engineering, Saga University, 1 Honjomachi, 840-8502 Saga-shi (Japan); Miyara, Akio; Tsubaki, Koutaro [Department of Mechanical Engineering, Saga University, 1 Honjomachi, 840-8502 Saga-shi (Japan)

2008-12-15

293

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)

1994-11-01

294

INVESTIGATION OF TRANSFER OF FLUORESCENT TRACERS FROM SURFACES TO SKIN  

Science.gov (United States)

Under the provisions of the Food Quality Protection Act (FQPA), aggregate exposure assessments must be conducted for pesticides proposed for registration. Many aspects of dermal exposure assessment remain poorly quantified. For purposes of assessing surface-to-skin transfers ...

295

Boiling heat transfer coefficient of R-22 refrigerant and its alternatives in horizontal tube : small refrigerator scale  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Boiling heat transfer coefficients and pressure drop of R-22 and its alternatives, which are R32/R125a/ R134 (23%/25%/52%) and R32/R125a (50%/50%), flowing inside smooth and grooved tubes have been determined with the conditions similar to those in small refrigerators. The range of mass flow rates examined is between 0.0025 and 0.0125 kg/s. The data have been taken at the evaporator temperatures of -35 to -4 oC and at the condenser temperatures of 40 to 50 oC. The boiling heat transfer coeffi...

2002-01-01

296

Calculations of the Energy Accommodation Coefficient for Gas-Surface Interactions  

CERN Multimedia

Calculations are carried out for the energy accommodation coefficient at a gas-surface interface using a recently developed classical mechanical theory of atom-surface collisions that includes both direct scattering and trapping-desorption processes in the physisorption well of the interaction potential. Full three-dimensional calculations are compared with the available data for the accommodation of rare gases at a tungsten surface and good agreement is found for the heavier gases for which classical physics is expected to be valid at all measured temperatures.

Fan, Guoqing

2008-01-01

297

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

2006-09-01

298

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ha...

2012-01-01

299

Prediction of heat transfer coefficients and friction factors for evaporation of R-134a flowing inside corrugated tubes  

Science.gov (United States)

In this study, experimental and simulation studies of the evaporation heat transfer coefficient and pressure drop of R-134a flowing through corrugated tubes are conducted. The test section is a horizontal counter-flow concentric tube-in-tube heat exchanger 2.0 m in length. A smooth tube and corrugated tubes with inner diameters of 8.7 mm are used as the inner tube. The outer tube is made from a smooth copper tube with an inner diameter of 21.2 mm. The corrugation pitches used in this study are 5.08, 6.35, and 8.46 mm. Similarly, the corrugation depths are 1, 1.25, and 1.5 mm, respectively. The results show that the maximum heat transfer coefficient and pressure drop obtained from the corrugated tube are up to 22 and 19 % higher than those obtained from the smooth tube, respectively. In addition, the average difference of the heat transfer coefficient and pressure drop between the simulation model and experimental data are about 10 and 15 %, respectively.

Laohalertdecha, S.; Aroonrat, K.; Dalkilic, A. S.; Mahian, O.; Kaewnai, S.; Wongwises, S.

2014-04-01

300

Optical measurements laboratory for determining heat transfer coefficients. [For use in Liquid Metal Fast Breeder Reactor Cask Technology Development Program  

Energy Technology Data Exchange (ETDEWEB)

A laboratory to be used for determining heat transfer coefficients using the technique of laser holographic interferometry (holometry) is described in this report. The basic theory upon which the experimental measurements are based is derived from first principles. Using a relationship between temperature and index of refraction, several cases of free convection in enclosures are evaluated. Results are presented for a heated hexagonal cylinder in an isothermal circular enclosure. In addition, a heated hexagonal cylinder in an isothermal box is evaluated. These provide check cases to some numerical code development which is being done in parallel with the optical measurements laboratory effort. Example holometrograms or holometric interferograms are shown to agree with analytical predictions as to number of fringes in the convective field. For the case of hexagonal cylinder in the circular cross-section enclosure, it is shown that convection has a significant influence upon the temperature gradient (heat transfer coefficient) when compared with thermal conduction. The laboratory will be used to determine heat transfer coefficients in enclosures related to the Liquid Metal Fast Breeder Reactor (LMFBR) Cask Technology Development Program.

Schimmel, W.P. Jr.

1976-06-01

 
 
 
 
301

Ultrasonic reflection coefficient and surface roughness index of OA articular cartilage: relation to pathological assessment  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Early diagnosis of Osteoarthritis (OA is essential for preventing further cartilage destruction and decreasing severe complications. The aims of this study are to explore the relationship between OA pathological grades and quantitative acoustic parameters and to provide more objective criteria for ultrasonic microscopic evaluation of the OA cartilage. Methods Articular cartilage samples were prepared from rabbit knees and scanned using ultrasound biomicroscopy (UBM. Three quantitative parameters, including the roughness index of the cartilage surface (URI, the reflection coefficients from the cartilage surface (R and from the cartilage-bone interface (Rbone were extracted. The osteoarthritis grades of these cartilage samples were qualitatively assessed by histology according to the grading standards of International Osteoarthritis Institute (OARSI. The relationship between these quantitative parameters and the osteoarthritis grades was explored. Results The results showed that URI increased with the OA grade. URI of the normal cartilage samples was significantly lower than the one of the OA cartilage samples. There was no significant difference in URI between the grade 1 cartilage samples and the grade 2 cartilage samples. The reflection coefficient of the cartilage surface reduced significantly with the development of OA (p Conclusion High frequency ultrasound measurements can reflect the changes in the surface roughness index and the ultrasound reflection coefficients of the cartilage samples with different OA grades. This study may provide useful information for the quantitative ultrasonic diagnosis of early OA.

Niu Hai-jun

2012-03-01

302

Heat transfer enhancement of free surface MHD-flow by the wall with non-uniform electrical conductivity  

Directory of Open Access Journals (Sweden)

Full Text Available Due to the Magnetohydrodynamic (MHD effect, which degrades heat transfer coefficients by pulsation suppression of external magnetic field, on the electrically conducting flow, the wall with non-uniform electrical conductivity is employed in a free surface MHD-flow system for heat transfer enhancement. The non-uniform electrical conductivity distribution of the channel wall may create alternate Lorentz forces along spanwise direction, which can effectively produce flow disturbance, promote mixture, reduce the thickness of boundary layer, and enhance heat transfer. So the heat transfer performances enhanced by some conducting strips aligned with the mean flow direction on the insulating wall of free surface MHD-flow are simulated numerically in this paper. The flow behaviors, heat transfer coefficients, friction factors and pressure drops are presented under different Hartmann numbers. Results show that, in the range of Hartmann numbers between 30 - 100, the wall with non-uniform conductivity can achieve heat transfer enhancements (Nu/Nu0 of about 1.2 to 1.6 relative to the insulating wall, with negligible friction augmentation. This research indicates that the modules with three or five conducting strips can obtain better enhancement effect in our research. Particularly, the heat transfer augmentation increases monotonically with increasing Hartmann numbers. Therefore, the enhancement purpose for high Hartman number MHD-flow is marked, which may remedy the depressing heat transfer coefficients by MHD effect.

H. L. Huang, B. Li

2010-11-01

303

Mass-transfer phenomena on the surface of adsorbents in reversed-phase chromatography  

Energy Technology Data Exchange (ETDEWEB)

Characteristics of mass-transfer phenomena on the surface of adsorbents in reversed-phase chromatography were studied by the chromatographic method and moment analysis. Enthalpy-entropy compensation occurs for surface diffusion in various systems of reversed-phase chromatography. The mechanism of surface diffusion seems to be essentially identical regardless of adsorption conditions. The linear free-energy relation holds in reversed-phase liquid chromatographic systems. Analyzing the slope of the linear relations, it is concluded that the activation energy of surface diffusion is essentially smaller than the isosteric heat of adsorption in liquid-phase adsorption as well as in gaseous systems though the heat of adsorption is experimentally determined to be smaller than the activation energy. Surface diffusion coefficients were correlated to physical properties of adsorbates. Concentration dependence of surface diffusion coefficient was explained by the chemical potential driving force model. An estimation method of the surface diffusion coefficient at each given temperature and amount adsorbed in reversed-phase liquid chromatography was proposed.

Miyabe, Kanji (Kurita Water Industries Ltd., Atsugi (Japan). Central Labs.); Suzuki, Motoyuki (Univ. of Tokyo (Japan). Inst. of Industrial Science)

1994-07-01

304

Measurement of the fuel temperature and the fuel-to-coolant heat transfer coefficient of Super Phenix 1 fuel elements  

International Nuclear Information System (INIS)

A new measurement method for measuring the mean fuel temperature as well as the fuel-to-coolant heat transfer coefficient of fast breeder reactor subassemblies (SA) is reported. The method is based on the individual heat balance of fuel SA's after fast reactor shut-downs and uses only the plants normal SA outlet temperature and neutron power signals. The method was used successfully at the french breeder prototype Super Phenix 1. The mean SA fuel temperature as well as the heat transfer coefficient of all SPX SA's have been determined at power levels between 15 and 90% of nominal power and increasing fuel burn-up from 3 to 83 EFPD (Equivalent of Full Power-Days). The measurements also provided fuel and whole SA time constants. The estimated accuracy of measured fuel parameters is in the order of 10%. Fuel temperatures and SA outlet temperature transients were also calculated with the SPX1 systems code DYN2 for exactly the same fuel and reactor operating parameters as in the experiments. Measured fuel temperatures were higher than calculated ones in all cases. The difference between measured and calculated core mean values increases from 50 K at low power to 180 K at 90% n.p. This is about the double of the experimental error margins. Measured SA heat transfer coefficients are by nearly 20% lower than corresponding heat transfer parameters used in the calculations. Discrepancies found between measured and calculated results also indicate that either the transient heat transfer in the gap between fuel and cladding (gap conductance) might not be exactly reproduced in the computer code or that the gap in the fresh fuel was larger than assumed in the calculations. (orig.)

1995-01-01

305

DETERMINACION COEFICIENTE CONVECTIVO DE MATERIA EN EL SECADO DE SÓLIDOS MATHEMATICAL CORRELATION TO GET MASS TRANSFER COEFFICIENT IN SOLIDS DRYING  

Directory of Open Access Journals (Sweden)

Full Text Available Una correlación matemática para determinar el coeficiente convectivo de materia durante la evaporación de agua desde la superficie húmeda, fue desarrollada para su aplicación con aire húmedo con bajas diferencias sicrométricas y temperaturas del aire sobre los 60°C. La teoría clásica para determinar coeficientes convectivos de calor y de materia, a través de parámetros adimensionales y de las analogías fenomenológicas difusivas, tienen validez sólo para aire seco. En el secado de sólidos, donde se requiere controlar las tasas de secado para evitar un daño físico en el producto, se impone la necesidad de operar con temperaturas bulbo húmedo por sobre los 40°C o diferencias sicrométricas moderadas. En esos rangos, las expresiones que relacionan los coeficientes convectivos de calor y materia, presentan errores que varían entre 26% y 113% para temperatura de bulbo húmedo entre 30°C y 70°C con diferencia sicrométrica de 10°C. La expresión formulada para esta aplicación, se plantea como una función de: el coeficiente convectivo de transferencia de calor, la temperatura bulbo húmedo y la diferencia sicrométrica. Los resultados obtenidos permiten establecer que, para las condiciones extremas de temperatura de bulbo húmedo y diferencia sicrométrica antes señalada el error se sitúa entre -1.4% a 2.14%, respecto del obtenido a partir de la metodología clásica La correlación obtenida es de forma polinomial, de fácil operación y viable de ser incorporada a cualquier modelo de simulación para la predicción de la dinámica del secadoA mathematical correlation to determine the mass coefficient, during the evaporation of water from a wet surface, was developed for their application in wet air with low psychometric differential and with air temperature above 60°C. The classic theory that has been used in order to get heat and mass convective coefficients, through non-dimensional parameters and phenomenological analogies, turns out to be valid only for dry air. In the particular case of solids drying, where operation requires to be performed under controlled drying rates, in order to prevent physical damage from affecting the product, is necessary to operate on a wet bulb temperature above 40ºC or at moderate psychometric differential. When we work under those ranges of temperature, the expressions that relate heat and mass convective coefficients show errors between 26% and 113% for wet temperature between 30°C and 70°C and psychometric difference of 30°C The expression that has been given for this application is stated as a function of the following: heat transfer coefficient, wet bulb temperature, and psychometric differential. The obtained results allow to settle down that, for the extreme conditions of wet bulb temperature and psychometric differences assigned before, the error is located among -1.4% to 2.14%, regarding the obtained through the classic methodology. The obtained correlation has polynomial form, of easy operation and viable of being incorporate to any simulation pattern for the prediction of the dynamics of the drying

Reinaldo Sanchez Arriagada

2007-01-01

306

DETERMINACION COEFICIENTE CONVECTIVO DE MATERIA EN EL SECADO DE SÓLIDOS / MATHEMATICAL CORRELATION TO GET MASS TRANSFER COEFFICIENT IN SOLIDS DRYING  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Una correlación matemática para determinar el coeficiente convectivo de materia durante la evaporación de agua desde la superficie húmeda, fue desarrollada para su aplicación con aire húmedo con bajas diferencias sicrométricas y temperaturas del aire sobre los 60°C. La teoría clásica para determinar [...] coeficientes convectivos de calor y de materia, a través de parámetros adimensionales y de las analogías fenomenológicas difusivas, tienen validez sólo para aire seco. En el secado de sólidos, donde se requiere controlar las tasas de secado para evitar un daño físico en el producto, se impone la necesidad de operar con temperaturas bulbo húmedo por sobre los 40°C o diferencias sicrométricas moderadas. En esos rangos, las expresiones que relacionan los coeficientes convectivos de calor y materia, presentan errores que varían entre 26% y 113% para temperatura de bulbo húmedo entre 30°C y 70°C con diferencia sicrométrica de 10°C. La expresión formulada para esta aplicación, se plantea como una función de: el coeficiente convectivo de transferencia de calor, la temperatura bulbo húmedo y la diferencia sicrométrica. Los resultados obtenidos permiten establecer que, para las condiciones extremas de temperatura de bulbo húmedo y diferencia sicrométrica antes señalada el error se sitúa entre -1.4% a 2.14%, respecto del obtenido a partir de la metodología clásica La correlación obtenida es de forma polinomial, de fácil operación y viable de ser incorporada a cualquier modelo de simulación para la predicción de la dinámica del secado Abstract in english A mathematical correlation to determine the mass coefficient, during the evaporation of water from a wet surface, was developed for their application in wet air with low psychometric differential and with air temperature above 60°C. The classic theory that has been used in order to get heat and mass [...] convective coefficients, through non-dimensional parameters and phenomenological analogies, turns out to be valid only for dry air. In the particular case of solids drying, where operation requires to be performed under controlled drying rates, in order to prevent physical damage from affecting the product, is necessary to operate on a wet bulb temperature above 40ºC or at moderate psychometric differential. When we work under those ranges of temperature, the expressions that relate heat and mass convective coefficients show errors between 26% and 113% for wet temperature between 30°C and 70°C and psychometric difference of 30°C The expression that has been given for this application is stated as a function of the following: heat transfer coefficient, wet bulb temperature, and psychometric differential. The obtained results allow to settle down that, for the extreme conditions of wet bulb temperature and psychometric differences assigned before, the error is located among -1.4% to 2.14%, regarding the obtained through the classic methodology. The obtained correlation has polynomial form, of easy operation and viable of being incorporate to any simulation pattern for the prediction of the dynamics of the drying

Sanchez Arriagada, Reinaldo.

307

A tale of two solutes: Dual-domain flow and the role of the mass transfer coefficient  

Science.gov (United States)

During remediation of natural porous media it is often observed that concentrations of contaminants exhibit long tail-off periods and a concentration rebound following the end of pumping. This phenomenon has often been modeled using a dual-domain approach, which includes a preferential flow domain, such as macropores or fractures, and a less mobile domain, such as the soil or rock matrix. In this model, preferential flow paths provide the majority of the advective mass transport and the less mobile domain contains the majority of storage. A pilot-scale remediation experiment was conducted on salt-affected soil associated with the accidental release of oilfield brine prior to the early 1970's. This salt contamination has deeply impregnated the soil matrix. Preferential flow pathways are present as root hole macropores in shallow soils and fractures in glacial till at depth. Understanding the solute transport processes between the matrix domain and the preferential flow domain is key to optimizing the remediation process. Tile drains were installed to collect saline leachate from shallow soils (0 to 2 m). In addition to the salt flushing experiment, a conservative organic tracer, 2,6-difluorobenzoic acid (DFBA), was applied to the soil surface. In the tile drain effluent, salt and tracer concentrations show differing behavior. Tracer concentrations tend to increase during increased flow events, indicating increased flushing. In contrast, salinity concentrations tend to decrease during increased flow events, indicating dilution of salt by low-salinity rain or irrigation water. Within the soil column, tracer pore water concentrations are decreasing rapidly with time, while salinity levels remain elevated. This is attributed to a lower rate of macropore transport of salt, as a result of the salt having diffused into the soil matrix, while the tracer has not. Thus the tracer is more readily transported through macropores and fractures. The two conservative tracers' histories were different because of the difference in their distribution at the beginning of the experiment. Dual-permeability water flow and solute transport has been modeled using the HYDRUS software package. The numerical model was calibrated to both the observed salt and tracer concentrations, and, consequently, the distinct behavior of the two solutes. The numerical modeling results indicate that salt and tracer transport are sensitive to the mass transfer coefficient between matrix and macropore domains and, consequently, proper selection of the coefficient value is key to the accurate prediction of transport in dual permeability media.

Callaghan, M. V.; Bishop, J. M.; Cey, E. E.; Bentley, L. R.

2011-12-01

308

Analysis and optimization of the heat transfer coefficient of a finned heat exchanger submitted to natural convection; Analise e otimizacao do coeficiente de transferencia de calor de um trocador aletado submetido a conveccao natural  

Energy Technology Data Exchange (ETDEWEB)

A heat transfer (condenser) of a domestic freezer was tested in a vertical channel in order to study the influence of the chimney effect in the optimization of the heat transfer coefficient. The variation of the opening of the channel, position and the heating power of the heat exchanger in the heat transfer coefficient was considered. The influence of the surface emissivity on the heat transfer by thermal radiation was studied with the heat exchanger testes without paint and with black paint. The air velocity entering the channel was measured with a hot wire anemometer. In order to evaluate the chimney effect, the heat exchanger was testes in a open ambient. This situation simulates its operational conditions when installed on the freezer system. The variables collected in the experimental procedures was gathered in the form of dimensionless parameters as Nusselt, Rayleigh, Grashof and Prandtl numbers, and dimensional parameters of the convection. The results showed that the highest heat transfer value occurred when both a specific position and a specific channel opening were used. The experiments pointed out that the radiation contribution must be considered in heat transfer calculations. The conclusions showed that different channel openings can improve the heat transfer coefficient in this heat transfer exchanger. (author)

Rocha, Alan Carlos Bueno da

1997-07-01

309

IR Thermography measurement of convective heat transfer coefficients with periodic excitation by Joule effect applied to the estimation of compact heat exchanger efficiency  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A new methodology has been developed to characterize the loss of efficiency of heat exchangers due to a maldistribution of the two-phase flow. The approach consists to measure the distribution of the local heat transfer coefficients with a non-intrusive and fast measurement method, based on a periodic excitation by Joule effect and infrared thermography measurement. An analytical model of the heat transfer is used to deduce heat transfer coefficients from the amplitude of the outside tube tem...

Leblay, P.; Henry, J. F.; Caron, D.; Leducq, D.; Bontemps, A.; Fournaison, L.

2012-01-01

310

Evaluation of flow accelerated corrosion by coupled analysis of corrosion and flow dynamics (2), flow dynamics calculations for determining mixing factors and mass transfer coefficients  

International Nuclear Information System (INIS)

In order to predict and mitigate flow accelerated corrosion (FAC) of carbon steel piping in PWR and BWR secondary systems, computer program packages for evaluating FAC have been developed by coupling one through three dimensional (1-3D) computational flow dynamics (CFD) models and corrosion models. To evaluate corrosive conditions, e.g., oxygen concentration and electrochemical corrosion potential (ECP) along the flow path, flow pattern and temperature in each elemental volume were obtained with 1D computational flow dynamics (CFD) codes. Precise flow turbulence and mass transfer coefficients at the structure surface were calculated with 3D CFD codes to determine wall thinning rates. One of the engineering options is application of k-? calculation as a 3D CFD code, which has limitation of detail evaluation of flow distribution at very surface of large scale piping. A combination of k-? calculation and wall function was proposed to evaluate precise distribution of mass transfer coefficients with reasonable CPU volume and computing time and, at the same time, reasonable accuracy. (author)

2009-10-02

311

Characteristics of heat transfer coefficient during nucleate pool boiling of binary mixtures . Improvement of correlation and its physical meaning  

Science.gov (United States)

Experimental studies were conducted on heat transfer on a horizontal platinum wire during nucleate pool boiling in nonazeotropic binary mixtures of R12+R113, R134a+R113, R22+R113 and R22+R11, at pressures of 0.25 to 0.7 MPa and at heat fluxes up to critical heat flux. The substances employed were chosen such that the components of a given mixture had a large difference in saturation temperatures. The boiling features of the mixtures and the pure substances were observed by photography. The relationship between the boiling features and the reduction in heat transfer coefficient in binary mixtures is discussed in order to propose a correlation useful for predicting the experimental data measured over a wide range of low and high heat fluxes. It is shown that the correlation is applicable also to alcoholic mixtures. The physical role of k, which was introduced to evaluate the effect of heat flux on the reduction in heat transfer coefficient, is clarified based on the measured nucleate pool boiling heat transfer data and the visual observations of the boiling features.

Inoue, T.; Kawae, N.; Monde, M.

312

Measurement of local heat transfer coefficient during gas–liquid Taylor bubble train flow by infra-red thermography  

International Nuclear Information System (INIS)

Highlights: • Infra-red thermographic study of Taylor bubble train flow in square mini-channel. • Design of experiments for measurement of local streamwise Nusselt number. • Minimizing conjugate heat transfer effects and resulting errors in data reduction. • Benchmarking against single-phase flow and three-dimensional computations. • Local heat transfer enhancement up to two times due to Taylor bubble train flow. -- Abstract: In mini/micro confined internal flow systems, Taylor bubble train flow takes place within specific range of respective volume flow ratios, wherein the liquid slugs get separated by elongated Taylor bubbles, resulting in an intermittent flow situation. This unique flow characteristic requires understanding of transport phenomena on global, as well as on local spatio-temporal scales. In this context, an experimental design methodology and its validation are presented in this work, with an aim of measuring the local heat transfer coefficient by employing high-resolution InfraRed Thermography. The effect of conjugate heat transfer on the true estimate of local transport coefficients, and subsequent data reduction technique, is discerned. Local heat transfer coefficient for (i) hydrodynamically fully developed and thermally developing single-phase flow in three-side heated channel and, (ii) non-boiling, air–water Taylor bubble train flow is measured and compared in a mini-channel of square cross-section (5 mm × 5 mm; Dh = 5 mm, Bo ? 3.4) machined on a stainless steel substrate (300 mm × 25 mm × 11 mm). The design of the setup ensures near uniform heat flux condition at the solid–fluid interface; the conjugate effects arising from the axial back conduction in the substrate are thus minimized. For benchmarking, the data from single-phase flow is also compared with three-dimensional computational simulations. Depending on the employed volume flow ratio, it is concluded that enhancement of nearly 1.2–2.0 times in time-averaged local streamwise Nusselt number can be obtained by Taylor bubble train flow, as compared to fully developed single-phase flow. This enhancement is attributed to the intermittent intrusion of Taylor bubbles in the liquid flow which drastically changes the local fluid temperature profiles. It is important to maintain proper boundary conditions during the experiment while estimating local heat transfer coefficient, especially in mini-micro systems

2014-02-01

313

Factors influencing the transfer of oil from contaminated surfaces to surface sample media  

Energy Technology Data Exchange (ETDEWEB)

This study examines the effect of surface concentration, contact time, and contact pressure on the transfer (collection) of oil from a contaminated surface to wipe sample media as described by the Washburn equation and contributes to the understanding of the transfer mechanisms. The mass of oil transferred from a contaminated work surface to a clean surface was found to be controlled by several factors including: the mass of contaminant on the surface (concentration); the length of time the clean surface is in contact with the contaminated surface (contact time); and the force with which the clean surface contacts the contaminated surface (contact pressure). The current lack of knowledge with respect to the influence of sampling parameters on the transfer of a liquid contaminant to surface sample media make the interpretation of surface sample results difficult at best. A factorial study was designed in which the effect of three surface concentrations, three contact times, and three contact pressures were investigated. This study demonstrated that with increasing either the contact time or contact pressure the mass of oil transferred to the porous sample media (filter papers) increased until a plateau in transfer was reached. A maximum contact time and pressure were found at which there was no longer a statistically significant increase in the mass of oil transferred to the porous sample media as either of these two parameters were increased. These results indicate that contact time and pressure have a significant effect on the transfer of oil to porous sample media. In addition, the composition of the sample media is an equally important factor in oil transfer. Therefore, when using surface sampling methods to determine the mass of contaminant on a work surface the composition of the collection media as well as the contact time and contact pressure must be specified.

McArthur, B.R.

1992-01-01

314

Impact of the increased active surface of the platinum catalyst on the total ammonia recovery coefficient  

Directory of Open Access Journals (Sweden)

Full Text Available In order to increase the active surface of platinum catalysts for ammonia oxidation and on the basis of theoretic considerations and tests in industrial environment, we have finally decided on their specific design. Efficiency on the newly designed catalyst was checked in industrial circumstances. A comparative analysis of the total ammonia recovery coefficient between the mentioned new catalysts and previously applied platinum catalysts was carried out. All advantages of catalysts with increased active surfaces were confirmed and a new method of their manufacturing process was selected.

Trumi? B.

2009-01-01

315

Study of energy transfer in helium atom scattering from surfaces  

CERN Multimedia

Recently developed quantum mechanical theory of inelastic He atom scattering (HAS) from solid surfaces is employed to analyze the energy transfer between projectile particles (thermal energy He-atoms) and vibrational degrees of freedom (phonons) characteristic of a variety of experimentally studied surfaces. We have first calculated the angular resolved energy transfer which can be directly compared with the values deducible from the HAS time-of-flight spectra and a good agreement with experimental data has been found. This enabled us to calculate the total or angular integrated energy transfer, which is of paramount importance in the studies of gas-surface scattering, but is neither accessible in HAS (which yields only the angular resolved quantities), nor in the wind tunnel measurements for surfaces whose atomic composition and cleanliness must be maintained during the experiment. Here we present the results for prototype collision systems of this kind, viz. He => Cu(001), He => Xe/Cu(111) and He => Xe(111)...

Siber, A; Toennies, J P

1999-01-01

316

Optimization of heat transfer coefficient correlation at supercritical pressure using genetic algorithms  

International Nuclear Information System (INIS)

The paper presents a new heat transfer correlation of water at supercritical pressure after review on existing heat transfer correlations. The new correlation is optimized by genetic algorithms based on existing test data. Based on current results, we conclude that genetic algorithms are effective to search a global optimized correlation but it is important to carefully select representative and authentic test data to reach an optimized solution and special attention needs to be paid on the deteriorated heat transfer region in the design of supercritical water reactor because it can not be predicted well by any correlations reviewed. (orig.)

2009-04-01

317

Determination of quadric equation coefficients describing three-dimensional surfaces, their constraint and skewed planes, and view point areas  

Science.gov (United States)

Mathematical model and a digital computer BLITZ language programming technique computes coefficients of quadric equations describing cylinders, paraboloids, ellipsoids, or planes with any orientation to a reference system, coordinates of a vector, and coefficients of quadric surfaces which limit the surface of three-dimensional space.

Paoletti, C. J.; Pond, J. E.; Vance, J. H.

1969-01-01

318

Influence of surface roughness and contact load on friction coefficient and scratch behavior of thermoplastic olefins  

Science.gov (United States)

To study the effects of surface roughness and contact load on the friction behavior and scratch resistance of polymers, a set of model thermoplastic olefins (TPO) systems with various surface roughness ( Ra) levels were prepared and evaluated. It is found that a higher Ra corresponds to a lower surface friction coefficient ( ?s). At each level of Ra, ?s gets larger as contact load increases, with a greater increase in ?s as Ra level increases. It is also observed that with increasing contact load and increasing Ra, the ?s tend to level off. In evaluating TPO scratch resistance, a lower ?s would delay the onset of ductile drawing-induced fish-scale surface deformation feature, thereby raising the load required to cause scratch visibility. However, as the contact load is further increased, the ?s evolves to become scratch coefficient of friction (SCOF) as significant sub-surface deformation and tip penetration occur and material displacement begins, i.e., ploughing. No dependence of Ra and ?s on the critical load for the onset of ploughing is observed. In this work, the distinction between ?s and SCOF will be illustrated. Approaches for improving scratch resistance of polymers via control of Ra are also discussed.

Jiang, Han; Browning, Robert; Fincher, Jason; Gasbarro, Anthony; Jones, Scooter; Sue, Hung-Jue

2008-05-01

319

Concurrent measurement of surface layer thickness and surface diffusion coefficient of oxides by _1_8O-exchange reaction  

International Nuclear Information System (INIS)

The _1_8O-exchange reaction between _1_8O"2 gas and nickel oxide was followed with a microbalance in the temperature range of 300-700_0C. The plots of weight gain vs.tsup(1/2) resulted in a curve having two straight portions. From the data in the first straight line the surface diffusion coefficients of oxygen for NiO were determined and were expressed as Dsub(s)=5.04 x 10"-_1_6 exp (-10.2x10_3 (cal/mol)/RT)(cm_2/s). The surface layer thickness was calculated from the weight change of the specimen at the end of the first line: delta=1.42x10_3 exp(-7.02 x10_3/RT)(A). The grain boundary diffusion coefficient of oxygen at 700_0C calculated from the second slow line was almost identical to the surface diffusion coefficient. (orig.)

1982-01-01

320

The stochastic distribution of available coefficient of friction for human locomotion of five different floor surfaces.  

Science.gov (United States)

The maximum coefficient of friction that can be supported at the shoe and floor interface without a slip is usually called the available coefficient of friction (ACOF) for human locomotion. The probability of a slip could be estimated using a statistical model by comparing the ACOF with the required coefficient of friction (RCOF), assuming that both coefficients have stochastic distributions. An investigation of the stochastic distributions of the ACOF of five different floor surfaces under dry, water and glycerol conditions is presented in this paper. One hundred friction measurements were performed on each floor surface under each surface condition. The Kolmogorov-Smirnov goodness-of-fit test was used to determine if the distribution of the ACOF was a good fit with the normal, log-normal and Weibull distributions. The results indicated that the ACOF distributions had a slightly better match with the normal and log-normal distributions than with the Weibull in only three out of 15 cases with a statistical significance. The results are far more complex than what had heretofore been published and different scenarios could emerge. Since the ACOF is compared with the RCOF for the estimate of slip probability, the distribution of the ACOF in seven cases could be considered a constant for this purpose when the ACOF is much lower or higher than the RCOF. A few cases could be represented by a normal distribution for practical reasons based on their skewness and kurtosis values without a statistical significance. No representation could be found in three cases out of 15. PMID:24268803

Chang, Wen-Ruey; Matz, Simon; Chang, Chien-Chi

2014-05-01

 
 
 
 
321

Sliding bubble dynamics and the effects on surface heat transfer  

International Nuclear Information System (INIS)

An investigation into the effects of a single sliding air bubble on heat transfer from a submerged, inclined surface has been undertaken. Existing literature has shown that both vapour and gas bubbles can increase heat transfer rates from adjacent heated surfaces. However, the mechanisms involved are complex and dynamic and in some cases poorly understood. The present study utilises high speed, high resolution, infrared thermography and video photography to measure two dimensional surface heat transfer and three dimensional bubble position and shape. This provides a unique insight into the complex interactions at the heated surface. Bubbles of volume 0.05, 0.1, 0.2 and 0.4 ml were released onto a surface inclined at 30 degrees to horizontal. Results confirmed that sliding bubbles can enhance heat transfer rates up to a factor of 9 and further insight was gained about the mechanisms behind this phenomenon. The enhancement effects were observed over large areas and persisted for a long duration with the bubble exhibiting complex shape and path oscillations. It is believed that the periodic wake structure present behind the sliding bubble affects the bubble motion and is responsible for the heat transfer effects observed. The nature of this wake is proposed to be that of a chain of horseshoe vortices.

2012-11-26

322

Radionuclide transfer onto ground surface in surface water flow, 1  

International Nuclear Information System (INIS)

Radionuclides migration in ground surface water flow is considered to be one of the important path way in the scenario for environmental migration of radionuclides leaked from low level radioactive waste repository. Simulating the slightly sloped surface on which contaminated solution is flowing downward, testing for radionuclide migration on ground surface had been started. As it's first step, an experiment was carried out under the condition of restricted infiltration in order to elucidate the adsorption behavior of radionuclides onto the loamy soil surface in related with hydraulic conditions. Radionuclides concentration change in effluent solution with time and a concentration distribution of radionuclides adsorbed on the ground surface were obtained from several experimental conditions combining the rate and the duration time of the water flow. The radionuclides concentration in the effluent solution was nearly constant during each experimental period, and was reduced under the condition of lower flow rate. The surface distribution of radionuclides concentration showed two distinctive regions. The one was near the inlet vessel where the concentration was promptly reducing, and the other was following the former where the concentration was nearly constant. The characteristic surface distribution of radionuclides concentration can be explained by a two dimensional diffusion model with a first order adsorption reaction, based on the advection of flow rate distribution in perpendicular direction. (author)

1991-01-01

323

Non-empirical calculation of transfer coefficients of lithium and sodium vapors  

International Nuclear Information System (INIS)

Viscosity and thermal conductivity coefficients of lithium and sodium vapors in the temperature range from 800 to 2000K and pressures from 102 to 105 Pa (lithium) and 103 to 106 Pa (sodium) are calculated. The error of calculated viscosity values is estimated as 10-15%, that for thermal conductivity is 20-30%

1990-01-01

324

Surface heat transfer due to sliding bubble motion  

Energy Technology Data Exchange (ETDEWEB)

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 {mu}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.

Donnelly, Brian [Mechanical and Manufacturing Engineering, Trinity College Dublin, College Green Dublin 2 (Ireland)], E-mail: donnelbg@tcd.ie; O' Donovan, Tadhg S. [School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh (United Kingdom); Murray, Darina B. [Mechanical and Manufacturing Engineering, Trinity College Dublin, College Green Dublin 2 (Ireland)

2009-05-15

325

Evaluation of an unsteady heat transfer coefficient in a mixing area. The FATHER experiment associated to the specific 'coefh' sensor  

International Nuclear Information System (INIS)

Piping systems of nuclear power plants include connections of branches conveying fluids at different temperatures. Thermal-hydraulic fluctuations arising from the turbulent mixing of the flows can affect the inner wall of the pipes and can lead to fatigue damage. In order to assess the high-cycle thermal fatigue damages risks of the NPP mixing zones, the knowledge of the temperature fluctuations transfer from fluid to structure is necessary. Some tests were performed in order to evaluate the unsteady heat transfer coefficient in a mixing zone, and especially during the FATHER experiment, which was initiated by AREVA NP, CEA and EDF to study thermal fatigue phenomena. More precisely, a specific sensor called 'coefh' was used during the experiments. This sensor records simultaneously local temperature fluctuations in the fluid and in the structure thanks to thermocouples incorporated in the body of the sensor, which is specifically designed to capture the rapid unsteady temperature fluctuations. This paper describes and compares different approaches that could be used to evaluate a heat transfer coefficient from the 'coefh' fluid and structure unsteady temperature measurements. A specific attention is paid to the impact of the phase difference between the fluid and the structure temperature measurements. (author)

2009-10-02

326

Boiling heat transfer coefficient of R-22 refrigerant and its alternatives in horizontal tube : small refrigerator scale  

Directory of Open Access Journals (Sweden)

Full Text Available Boiling heat transfer coefficients and pressure drop of R-22 and its alternatives, which are R32/R125a/ R134 (23%/25%/52% and R32/R125a (50%/50%, flowing inside smooth and grooved tubes have been determined with the conditions similar to those in small refrigerators. The range of mass flow rates examined is between 0.0025 and 0.0125 kg/s. The data have been taken at the evaporator temperatures of -35 to -4 oC and at the condenser temperatures of 40 to 50 oC. The boiling heat transfer coefficients of the refrigerants in the grooved tubes are higher than those in the smooth tubes and R-22 shows the best performance for both tubes. The heat transfer correlations have also been developed. In case of the pressure drop, the twophase friction multiplier ?G 2 increases with Martinelli parameter and there is no effect of the tube roughness and the types of the refrigerants.

Uthen Kuntha

2002-04-01

327

Mean 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 In this study the transfer coefficient of evaporation heat of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a in a vertical plate heat exchanger was experimentally investigated. The results are presented as the dependancy of the mean heat transfer coefficient for the whole heat exchanger on the mean vapor quality. The influences of mass flux, heat flux and flow configuration on the heat transfer coefficient were also taken into account and a comparison with previously published experimental data and literature correlations was made.

EMILA DJORDJEVIC

2007-08-01

328

Fouling of roughened stainless steel surfaces during convective heat transfer to aqueous solutions  

International Nuclear Information System (INIS)

The deterioration of heat transfer performance due to fouling is the prime cause for higher energy consumption and inefficiency in many industrial heat exchangers such as those in power plants, refineries, food and dairy industries. Fouling is also a very complex process in which many geometrical, physical and operating parameters are involved with poorly understood interaction. Among them, the surface roughness is an important surface characteristic that would greatly influence crystallisation fouling mechanisms and hence deposition morphology and stickability to the surface. In this work, the effect of the surface roughness of AISI 304 BA stainless steel surfaces on fouling of an aqueous solution with inverse solubility behaviour has been investigated under convective heat transfer. Several experiments have been performed on roughened surfaces ranging from 0.18 to 1.55 ?m for different bulk concentrations and heat fluxes. The EDTA titration method was used to measure the concentration of the calcium sulphate salt in order to maintain it at constant value during each fouling run. Experimental results show that the heat transfer coefficient of very rough surfaces (1.55 ?m) decreases more rapidly than that of 0.54 ?m. Several facts contribute to this behaviour notably (1) increased of primary heterogeneous nucleation rate on the surfaces; (2) reduction of local shear stress in the valleys and (3) reduced removal rate of the crystals from the surfaces where the roughness elements protrude out of the viscous sub-layer. The results also show linear and proportional variation of the fouling rate and heat flux within the range of operating conditions. In addition, the deposition process in terms of fouling rate could only be affected at lower surface contact angles. Such results would particularly be of interest for new surface treatment technologies which aim at altering the surface texture

2008-11-01

329

Coefficients of reflection of particles and energy of slow ions and atoms from a solid surface  

International Nuclear Information System (INIS)

The analytical expressions are derived for total reflection coefficients of particles Rsub(N) and energy Rsub(E) of slow ions and atoms scattered by a solid surface. The expressions derived for Rsub(N) and Rsub(E) are valid for arbitrary values of the incident angle THETA_0 under the condition that the reflection parameter ?=Rsub(0)/lsub(tr) (1-sin THETA_0) (where R_0 and lsub(tr) are, respectively, the total range and transport length of particles in the material) is large as compared with unity (?>>1). The theoretical conclusions agree well with the reflection coefficient data obtained on the base of computer simulation of the backscattering process

1986-01-01

330

Time-dependent heat transfer in a fin-wall assembly. New performance coefficient: thermal reverse admittance  

Energy Technology Data Exchange (ETDEWEB)

Transient thermal fields and heat fluxes due to step-harmonic temperature excitation and their dependence on frequency are studied in a fin-wall assembly. Application of the currently used efficiency coefficient to transient-harmonic processes is discussed. A new coefficient, thermal reverse transfer admittance, and others, including the augmentation factor, have been used to characterise the behaviour of the system. In a thermal frequency response analysis, module, phase, real and imaginary components have been obtained. For the calculation a network model (whose admittance is identical to the thermal admittance of the system) has been designed for the whole system. The network simulation method provides the numerical response of the system by running the network in circuit resolution software. (authors)

Alarcon, M. [Murcia Univ., Thermal Machines and Heat Engines Area (Spain); Alhama, F.; Gonzalez-Fernandez, C.F. [University of Cartagena, Dept. of Amplied Physics, Tech., Cartagena, Murcia (Spain)

2002-04-01

331

Magnetohydrodynamic Three-Dimensional Flow and Heat Transfer over a Stretching Surface in a Viscoelastic Fluid  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the problem of steady laminar three-dimensional magnetohydrodynamic (MHD boundary layer flow and heat transfer over a stretching surface in a viscoelastic fluid is investigated. The equations which govern the flow are coupled nonlinear ordinary differential equations, which are solved numerically using a finite-difference scheme known as the Keller-box method. Various physical governing parameters such as the magnetic parameter M, the material or viscoelastic parameter K and the Prandtl number Pr are considered and the effects of these parameters are investigated. It is found that the material parameter K and the magnetic parameter M present opposite effects on the fluid flow and heat transfer characteristics. The numerical results obtained for the skin friction coefficient and the local Nusselt number are presented in tables. The features and profiles of the flow and heat transfer characteristics are illustrated in the forms of graphs.

Kartini Ahmad

2011-09-01

332

Theoretical and experimental studies of heat transfer at heating surfaces immersed in fluidized beds  

Energy Technology Data Exchange (ETDEWEB)

Proposes a mathematical model for calculating the heat transfer coefficient from a heating surface immersed in a gas-solids fluidized bed. The model is based on equations according to H. Martin and on hydrodynamic calculations according to K. Hilligardt and J. Werther. Furthermore, particle diameters and their definitions by Ergun relations are regarded as relevant values for heat transfer calculations. Heat transfer is analyzed as particle and gas convection and as radiation; equations employed are provided. Laboratory experiments were also carried out verifying the proposed model and comparing results to those of calculations made by H. Richter and K. Janssen. It is concluded that the model is both suitable for analyzing the heating of a fluidized bed by an immersed heat exchanger as well as calculating heat extraction from coal fired fluidized beds. 27 refs.

Ebeling, H.-H.; Sankol, B. (Technische Universitaet, Magdeburg (German Democratic Republic))

1988-01-01

333

On the parameterization of surface momentum transport via drag coefficient in low-wind conditions  

Science.gov (United States)

The subgrid-scale surface momentum transport, which plays an important role in determining the exchange between the atmosphere and the underlying surface, is often parameterized in terms of the surface mean wind speed via drag coefficient (CD), a parameter that needs to be determined externally often through the Monin-Obukhov Similarity (MOS) Theory. However, some characteristics of CD derived from observations for overland conditions, particularly the substantial increase of CD with a decrease in wind speed in low-wind conditions, cannot be explained by MOS. This issue is investigated using data collected by a portable meteorological tower. By analyzing the turbulent kinetic energy budget, a novel parameterization framework for momentum fluxes is proposed. The new parameterization not only appropriately describes the observed variation of CD but also can be simplified to MOS with certain assumptions. Moreover, the effect of stability, which traditionally has to be determined empirically, can now be determined internally within the new framework.

Zhu, Ping; Furst, Jonathan

2013-06-01

334

Experimental Study on the Impact of External Geometrical Shape on Free and Forced Convection Time Dependent Average Heat Transfer Coefficient during Cooling Process  

Directory of Open Access Journals (Sweden)

Full Text Available In this research, an experimental study was conducted to high light the impact of the exterior shape of a cylindrical body on the forced and free convection heat transfer coefficients when the body is hold in the entrance of an air duct. The impact of changing the body location within the air duct and the air speed are also demonstrated. The cylinders were manufactured with circular, triangular and square sections of copper for its high thermal conductivity with appropriate dimensions, while maintaining the surface area of all shapes to be the same. Each cylinder was heated to a certain temperature and put inside the duct at certain locations. The temperature of the cylinder was then monitored. The heat transfer coefficient were then calculated for forced convection for several Reynolds number (4555-18222.The study covered free convection impact for values of Rayleigh number ranging between (1069-3321. Imperical relationships were obtained for all cases of forced and free convection and compared with equations of circular cylindrical shapes found in literature. These imperical equations were found to be in good comparison with that of other sources.

Sundus Hussein Abd

2012-01-01

335

An effusive molecular beam technique for studies of polyatomic gas-surface reactivity and energy transfer.  

Science.gov (United States)

An effusive molecular beam technique is described to measure alkane dissociative sticking coefficients, S(T(g), T(s); ?), on metal surfaces for which the impinging gas temperature, T(g), and surface temperature, T(s), can be independently varied, along with the angle of incidence, ?, of the impinging gas. Effusive beam experiments with T(g) = T(s) = T allow for determination of angle-resolved dissociative sticking coefficients, S(T; ?), which when averaged over the cos?(?)/? angular distribution appropriate to the impinging flux from a thermal ambient gas yield the thermal dissociative sticking coefficient, S(T). Nonequilibrium S(T(g), T(s); ?) measurements for which T(g) ? T(s) provide additional opportunities to characterize the transition state and gas-surface energy transfer at reactive energies. A resistively heated effusive molecular beam doser controls the T(g) of the impinging gas striking the surface. The flux of molecules striking the surface from the effusive beam is determined from knowledge of the dosing geometry, chamber pressure, and pumping speed. Separate experiments with a calibrated leak serve to fix the chamber pumping speed. Postdosing Auger electron spectroscopy is used to measure the carbon of the alkyl radical reaction product that is deposited on the surface as a result of alkane dissociative sticking. As implemented in a typical ultrahigh vacuum chamber for surface analysis, the technique has provided access to a dynamic range of roughly 6 orders of magnitude in the initial dissociative sticking coefficient for small alkanes on Pt(111). PMID:21529024

Cushing, G W; Navin, J K; Valadez, L; Johánek, V; Harrison, I

2011-04-01

336

Transfer matrix treatment of atomic chemisorption on transition metal surface  

International Nuclear Information System (INIS)

We study the atomic adsorption of hydrogen on paramagnetic nickel 100 surface, using the Green's function formalism and the transfer matrix technique, which allows the treatment of the geometry of the system in a simple manner. We incorporate electronic correlation at the adatom orbital in a self consistent Hartree-Fock approach. The adsorption energy, local density of states and cherge transfer between the solid and the adatom are calculated for different crystal structures (sc and fcc) and adatom positions at the surface. The results are discussed in comparison with other theories and with available experimental data, with satisfactory agreement. (Author)

1981-01-01

337

Study on the electromechanical coupling coefficient of Rayleigh-type surface acoustic waves in semi-infinite piezoelectrics/non-piezoelectrics superlattices.  

Science.gov (United States)

The electromechanical coupling coefficient of Rayleigh-type surface acoustic waves in semi-infinite piezoelectrics/non-piezoelectrics superlattices is investigated by the transfer matrix method. Research results show the high electromechanical coupling coefficient can be obtained in these systems. The optimization design of it is also discussed fully. It is significantly influenced by electrical boundary conditions on interfaces, thickness ratios of piezoelectric and non-piezoelectric layers, and material parameters (such as velocities of pure longitudinal and transversal bulk waves in non-piezoelectric layers). In order to obtain higher electromechanical coupling coefficient, shorted interfaces, non-piezoelectric materials with large velocities of longitudinal and transversal bulk waves, and proper thickness ratios should be chosen. PMID:24035609

Chen, Shi; Zhang, Yinhong; Lin, Shuyu; Fu, Zhiqiang

2014-02-01

338

Association of the transfer coefficient of the lung for carbon monoxide with emphysema progression in male smokers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A decreased transfer coefficient of the lung for carbon monoxide (KCO) is associated with emphysema. We evaluated whether in heavy smokers, baseline KCO was associated with the progression of computed tomography (CT)-detected emphysema, and the progression of airflow limitation. Heavy smokers, mean+/-SD 41.3+/-18.7 pack-yrs, participating in a lung cancer screening trial underwent diffusion testing and CT scanning of the lungs. CT scanning was repeated after median (25th-75th percentile) 2.8 ...

Hoesein, F. A. A. Mohamed; Zanen, P.; Ginneken, B.; Klaveren, R. J.; Lammers, J-w J.

2011-01-01

339

Experimental modeling of a nuclear waste repository: Determination of convective heat transfer coefficients and drift temperature profiles  

International Nuclear Information System (INIS)

An experimental model was developed for a nuclear waste repository storage room. Data were taken over a Reynolds number range of 6,000 to 180,000, covering both the forced and mixed (combined natural and forced) regimes of convection. Data are presented for several circumferential boundary conditions. Results indicate that the natural convection component is significant. The finite difference heat conduction code HEATING5 was used to plot temperatures around the repository room for the different heat transfer coefficients. The plots show that the use of standard forced convection relations can result in over estimating the room temperature by as much as 70"0C

1986-01-01

340

Initial temperature coefficient of thermal emf and transfer entropy of electrolytes in aqueous solutions  

International Nuclear Information System (INIS)

Experimental study was made on thermoelectrochemical systems, composed of silver-chloride electrodes and aqueous solutions of calcium, strontium, barium and lanthanum chlorides in 283-358 K temperature range and in m=0.0025-0.05 concentration range. Standard entropies of electrolyte transfer in studied temperature range were calculated

1990-01-01

 
 
 
 
341

Determination of Local Experimental Heat-Transfer Coefficients on Combustion Side of an Ammonia-Oxygen Rocket  

Science.gov (United States)

Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector.

Liebert, Curt H.; Ehlers, Robert C.

1961-01-01

342

Forced axial and torsional vibrations of a shaft line using the transfer matrix method related to solution coefficients  

Science.gov (United States)

This present paper deals with a mathematical description of linear axial and torsional vibrations. The normal and tangential stress tensor components produced by axial-torsional deformations and vibrations in the propeller and intermediate shafts, under the influence of propeller-induced static and variable hydrodynamic excitations are also studied. The transfer matrix method related to the constant coefficients of differential equation solutions is used. The advantage of the latter as compared with a well-known method of transfer matrix associated with state vector is the possibility of reducing the number of multiplied matrices when adjacent shaft segments have the same material properties and diameters. The results show that there is no risk of buckling and confirm that the strength of the shaft line depends on the value of the static tangential stresses which is the most important component of the stress tensor.

Chahr-Eddine, Kandouci; Yassine, Adjal

2014-06-01

343

Heat and mass transfer effect on hydromagnetic flow of a moving permeable vertical surface  

International Nuclear Information System (INIS)

Numerical results are presented for the effects of heat and mass transfer on hydromagnetic flow of a moving permeable vertical surface. The surface is maintained at linear temperature and concentration variations. The nonlinear-coupled boundary layer equations were transformed and the resulting ordinary differential equations were solved by perturbation technique. Numerical results for the dimensionless velocity profiles, the temperature profiles, the local friction coefficient and the local Nusselt number are presented for various values of Prandtl number, suction/blowing parameter, Schrnidt number, buoyancy ratio and Hartmann number. The effects of the different parameters on the velocity and temperature profiles as well as skin friction and wall heat transfer are evaluated. Favorable comparisons with previously published work confirm the correctness of numerical results

2004-02-24

344

Serrating Nozzle Surfaces for Complete Transfer of Droplets  

Science.gov (United States)

A method of ensuring the complete transfer of liquid droplets from nozzles in microfluidic devices to nearby surfaces involves relatively simple geometric modification of the nozzle surfaces. The method is especially applicable to nozzles in print heads and similar devices required to dispense liquid droplets having precise volumes. Examples of such devices include heads for soft printing of ink on paper and heads for depositing droplets of deoxyribonucleic acid (DNA) or protein solutions on glass plates to form microarrays of spots for analysis. The main purpose served by the present method is to ensure that droplets transferred from a nozzle have consistent volume, as needed to ensure accuracy in microarray analysis or consistent appearance of printed text and images. In soft printing, droplets having consistent volume are generated inside a print head, but in the absence of the present method, the consistency is lost in printing because after each printing action (in which a drop is ejected from a nozzle), a small residual volume of liquid remains attached to the nozzle. By providing for complete transfer of droplets (and thus eliminating residual liquid attached to the nozzle) the method ensures consistency of volume of transferred droplets. An additional benefit of elimination of residue is prevention of cross-contamination among different liquids printed through the same nozzle a major consideration in DNA microarray analysis. The method also accelerates the printing process by minimizing the need to clean a printing head to prevent cross-contamination. Soft printing involves a hydrophobic nozzle surface and a hydrophilic print surface. When the two surfaces are brought into proximity such that a droplet in the nozzle makes contact with the print surface, a substantial portion of the droplet becomes transferred to the print surface. Then as the nozzle and the print surface are pulled apart, the droplet is pulled apart and most of the droplet remains on the print surface. The basic principle of the present method is to reduce the liquid-solid surface energy of the nozzle to a level sufficiently below the intrinsic solid-liquid surface energy of the nozzle material so that the droplet is not pulled apart and, instead, the entire droplet volume becomes transferred to the print surface. In this method, the liquid-solid surface energy is reduced by introducing artificial surface roughness in the form of micromachined serrations on the inner nozzle surface (see figure). The method was tested in experiments on soft printing of DNA solutions and of deionized water through 0.5-mm-diameter nozzles, of which some were not serrated, some were partially serrated, and some were fully serrated. In the nozzles without serrations, transfer was incomplete; that is, residual liquids remained in the nozzles after printing. However, in every nozzle in which at least half the inner surface was serrated, complete transfer of droplets to the print surface was achieved.

Kim, Chang-Jin " CJ" Yi, Uichong

2010-01-01

345

Study of Heat Transfer in a Kapok Material from the Convective Heat Transfer Coefficient and the Excitation Pulse of Solicitations External Climatic  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of this study is to characterize thermal insulating local material, kapok, from a study in 3 dimensions in Cartesian coordinate and in dynamic frequency regime. From a study a 3 dimensional the heat transfer through a material made of wool kapok (thermal conductivity: &lambda = 0,035 W/m/K; density: &rho = 12, 35 kg/m3; thermal diffusivity: &alpha = 17, 1.10-7 m2 /s is presented. The evolution curves of temperature versus convective heat transfer coefficient have helped highlight the importance of pulse excitation and the depth in the material. The thermal impedance is studied from representations of Nyquist and Bode diagrams allowing characterizing the thermal behavior from thermistors. The evolution of the thermal impedance with the thermal capacity of the material is presented.

M. Dieng

2013-02-01

346

Pattern recognition of surface electromyography signal based on wavelet coefficient entropy  

Directory of Open Access Journals (Sweden)

Full Text Available This paper introduced a novel, simple and ef-fective method to extract the general feature of two surface EMG (electromyography signal patterns: forearm supination (FS surface EMG signal and forearm pronation (FP surface EMG signal. After surface EMG (SEMG signal was decomposed to the fourth resolution level with wavelet packet transform (WPT, its whole scaling space (with frequencies in the interval (0Hz, 500Hz] was divided into16 frequency bands (FB. Then wavelet coefficient entropy (WCE of every FB was calculated and corre-spondingly marked with WCE(n (from the nth FB, n=1,2,…16. Lastly, some WCE(n were chosen to form WCE feature vector, which was used to distinguish FS surface EMG signals from FP surface EMG signals. The result showed that the WCE feather vector consisted of WCE(7 (187.25Hz, 218.75Hz and WCE(8 (218.75Hz, 250Hz can more effectively recog-nize FS and FP patterns than other WCE feature vector or the WPT feature vector which was gained by the combination of WPT and principal components analysis.

Ying Gao

2009-09-01

347

EPMA-EDS surface measurements of interdiffusion coefficients between miscible metals in thin films  

Energy Technology Data Exchange (ETDEWEB)

A new technique is developed to study interdiffusion between two miscible metals. The technique is applied to the Ni-Pd system. It consists in measuring the change of apparent surface composition of a Pd substrate coated with an 800 nm Ni thin film during annealing at a given temperature. The measurement is carried out in-situ inside the chamber of a SEM (scanning electron microscope) by EPMA-EDS (electron probe microanalysis-energy dispersive X-ray spectroscopy). The experimental data are processed using a model that mixes the Fick's diffusion equations and the electron probe microanalysis equation. This process allows the determination of the mean interdiffusion coefficient at a given annealing temperature. The main advantages of the technique are the possible determination of interdiffusion coefficients in thin films and at very low temperature (down to 430 deg. C, i.e. {approx}0.4 T{sub m}), which is not achievable with other techniques conventionally used for the study of interdiffusion. The Ni-Pd mean interdiffusion coefficient is shown to follow an Arrhenius law (D-tilde{sub c}=6.32x10{sup -3} exp((178.8kJmol{sup -1})/(RT) )cm{sup 2}s{sup -1}) between 430 deg. C and 900 deg. C, in relatively good agreement with previous interdiffusion measurements made on the Ni-Pd system at higher temperature.

Christien, F., E-mail: frederic.christien@univ-nantes.fr [Laboratoire Genie des Materiaux et Procedes Associes, Universite de Nantes, Polytech' Nantes, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France); Pierson, J.F. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt F-54042 NANCY Cedex France (France); Hassini, A. [Laboratoire Genie des Materiaux et Procedes Associes, Universite de Nantes, Polytech' Nantes, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France); Capon, F. [Laboratoire de Science et Genie des Surfaces (UMR CNRS 7570), Ecole des Mines, Parc de Saurupt F-54042 NANCY Cedex France (France); Le Gall, R.; Brousse, T. [Laboratoire Genie des Materiaux et Procedes Associes, Universite de Nantes, Polytech' Nantes, Rue Christian Pauc, BP 50609, F-44306 Nantes Cedex 3 (France)

2010-01-01

348

EPMA-EDS surface measurements of interdiffusion coefficients between miscible metals in thin films  

International Nuclear Information System (INIS)

A new technique is developed to study interdiffusion between two miscible metals. The technique is applied to the Ni-Pd system. It consists in measuring the change of apparent surface composition of a Pd substrate coated with an 800 nm Ni thin film during annealing at a given temperature. The measurement is carried out in-situ inside the chamber of a SEM (scanning electron microscope) by EPMA-EDS (electron probe microanalysis-energy dispersive X-ray spectroscopy). The experimental data are processed using a model that mixes the Fick's diffusion equations and the electron probe microanalysis equation. This process allows the determination of the mean interdiffusion coefficient at a given annealing temperature. The main advantages of the technique are the possible determination of interdiffusion coefficients in thin films and at very low temperature (down to 430 deg. C, i.e. ?0.4 Tm), which is not achievable with other techniques conventionally used for the study of interdiffusion. The Ni-Pd mean interdiffusion coefficient is shown to follow an Arrhenius law (D-tildec=6.32x10-3 exp((178.8kJmol-1)/(RT) )cm2s-1) between 430 deg. C and 900 deg. C, in relatively good agreement with previous interdiffusion measurements made on the Ni-Pd system at higher temperature.

2010-01-01

349

A computer simulation of hydrodynamics and heat transfer at immersed surfaces in a fluidized bed  

Energy Technology Data Exchange (ETDEWEB)

A computer simulation of the hydrodynamics and heat transfer processes in a fluidized bed with bubbles propagating from a single jet has been developed. The velocity, volume fraction, and temperature distributions of both phases predicted by the model show satisfactory agreement with the experimental models of Kuipers (1990). An Eulerian-Eulerian approach that incorporates a two-fluid model was utilized. The simulation was developed using a general purpose Computational Fluid Dynamics (CFD) solver; PHOENICS{reg{underscore}sign}. The conservation equations describing the physics of the two-phase nature of the fluidized bed are solved using the finite volume approach. The Interphase-Slip-Algorithm, which is a part of the PHOENICS package, was utilized to ensure numerical stability and convergence of the problem. The unsteady state simulation predicts the hydrodynamics and heat transfer in the fluidized bed. Also predicted, is the formation and propagation of a bubble from a single jet near the immersed surface, as a function of time. The heat transfer coefficients prevailing at the immersed heated wall are calculated. The calculated values of the heat transfer coefficients and simulated hydrodynamics compare well with experimental and numerical data present in literature. Such a simulation technique allows performance evaluation for different bed input parameters, and can evolve into a tool that would help in the optimum design of a fluidized combustion chamber.

Kodikal, N.J.; Bhavnani, S.H.

1999-07-01

350

Determination of nuclear vertex constants (asymptotic coefficients) from charged-particle-transfer reactions  

International Nuclear Information System (INIS)

We propose a new method of determination of nuclear vertex constants (NVC) from charged-particle-transfer reactions taking into account Coulomb effects. We analyze experimental differential cross sections for the D(d,n)"3He and T(d,n)"4He reactions at different energies of incident deuterons and extract squares of NVC for the virtual processes "3He?d+p and ??t+p

1986-11-01

351

Determination of the nuclear vertex constants (asymptotic coefficients) from charged particle transfer reactions  

International Nuclear Information System (INIS)

A new method is suggested for calculating nuclear vertex constants (NVC) from charged-particle transfer reactions taking Coulomb effects into account. Experimental differential cross sections of the D(d, n)"3He and T(d, n)"4He reactions are analyzed for different energies of the incident deuterons. The NVC square for the virtual processes "3He ? d+p and ? ? t+p are obtained

1986-11-01

352

Graphene segregated on Ni surfaces and transferred to insulators  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We report an approach to synthesize high quality graphene by surface segregation and substrate transfer. Graphene was segregated from Ni surface under the ambient pressure by dissolving carbon in Ni at high temperatures followed by cooling down with various rates. Different cooling rates led to different segregation behaviors, strongly affecting the thickness and quality of the graphene films. Electron microscopy and Raman spectroscopy indicated that the graphene films synthesized with medium...

2008-01-01

353

Effect of Soft Material Hardness and Hard Material Surface Morphology on Friction and Transfer Layer Formation; Dry Condition  

Directory of Open Access Journals (Sweden)

Full Text Available The morphological features of the surface in both micro and macro levels are important factors governing the tribological behavior of the contacting surfaces. Surface hardness is also an important factor which governs the friction and wear behaviors of the contacting surfaces. Surface morphology of a tool is an important factor as it primarily controls the tribological behavior at the interface which in turn controls the surface finish of products. In the present investigation a pin-on-plate sliding tester was used to identify the effect of surface morphology and hardness on co-efficient of friction and transfer layer which characterizes the tribological behavior. The morphology of mild steel (EN8 plate surfaces were modified by employing three different surface modification methods like grinding (silicon carbide wheel polishing, shot blasting and electric discharge machining methods. Surface roughness parameters which characterize the morphology of the steel plates were measured using a three dimensional optical profilometer. Role of hardness is studied by employing lead, copper and Aluminum (Al6082 pins which were slid against steel plates. Experiments were conducted for plate inclination angles of 1, 1.5,2 and 2.5 degrees. Normal load was varied from 1 to 150N during the tests. Experiments were conducted under dry condition in ambient environment. Scanning electron microscope was used to study the formation of transfer layer on plate and pin surfaces. It was observed that the co-efficient of friction and transfer layer formation were found to depend on the surface morphology of the harder surface. The quantum of transfer layer formation on the surfaces is found to increase with increase in surface roughness

Mr.M Basavaraju

2013-09-01

354

Mitigated subsurface transfer line leak resulting in a surface pool  

Energy Technology Data Exchange (ETDEWEB)

This analysis evaluates the mitigated consequences of a potential waste transfer spill from an underground pipeline. The spill forms a surface pool. One waste composite, a 67% liquid, 33% solid, from a single shell tank is evaluated. Even drain back from a very long pipeline (50,000 ft), does not pose dose consequences to the onsite or offsite individual above guideline values.

SCOTT, D.L.

1999-02-08

355

Transfer coefficients of selected radionuclides to animal products. I. Comparison of milk and meat from dairy cows and goats  

Energy Technology Data Exchange (ETDEWEB)

The diet-milk transfer coefficient, Fm (Bq L-1 output in milk divided by Bq d-1 intake to the animal) was studied for eight radionuclides that previously had been given little attention. The Fm values for cows and goats, respectively, were: 2.3 x 10(-5) and 1.5 x 10(-4) for /sup 99m/Tc, 1.4 x 10(-4) and 8.5 x 10(-4) for /sup 95m/Tc, 1.1 x 10(-2) for /sup 99/Tc (goats only); 1.7 x 10(-3) and 9 x 10(-3) for /sup 99/Mo; 4.8 x 10(-4) and 4.4 x 10(-3) for /sup 123m/Te; 4.8 x 10(-4) and 4.6 x 10(-3) for /sup 133/Ba; 5.5 x 10(-7) and 5.5 x 10(-6) for /sup 95/Zr; and 4.1 x 10(-7) and 6.4 x 10(-6) for /sup 95/Nb. The goat/cow transfer coefficient ratios for milk were approximately 10, but the goat/cow ratios for meat varied by three orders of magnitude.

Johnson, J.E.; Ward, G.M.; Ennis, M.E. Jr.; Boamah, K.N.

1988-02-01

356

Influence of Operating Conditions and Physical Properties of Liquid Medium on Volumetric Oxygen Transfer Coefficient in a Dual Impeller Bioreactor  

Directory of Open Access Journals (Sweden)

Full Text Available The objective of this research was to study the effects of process variables on the volumetric mass transfer coefficient of oxygen, in a stirred bioreactor by static gassing-out method. In this study, the various process conditions were chosen including three parameters, namely, concentration of glucose in medium (10, 15 and 20 g/l, air flow rate (1, 1.25, 1.5 and 1.75 vvm, and agitation rate (300, 400, 500 and 600 rpm. From the results, it was found that the increased with increasing air flow rate and/or speed of agitation, but decreased with increasing concentration of the glucose in medium. The maximum occurred when the concentration of glucose in medium was the least (10 g/l, air flow rate 1.75 vvm, and agitation rate 600 rpm. Correlations have been developed for the estimation of volumetric mass transfer coefficient at various process conditions for medium with different glucose concentrations. Then the exponent values representing dependence of on the process conditions were compared with literature values.

Kongdej LIMPAIBOON

2013-01-01

357

Heat transfer coefficient in a shallow fluidized bed heat exchanger with a continuous flow of solid particles  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english This work shows the experimental study of a continuous gas-solid fluidized bed with an immersed tube where cold water is heated by fluidized solid particles presenting inlet temperature from 450 to 700°C. Experiments were carried out in order to verify the influence of solid particle flow rate a [...] nd distance between baffles immersed in a shallow fluidized bed. The solid material was 254µm diameter silica sand particles, fluidized by air in a 0.90m long and 0.15m wide heat exchanger. The measurements were taken at steady state conditions for solid mass flow rate from 10 to 100 kg/h, in a heat exchanger with the presence of 5 or 8 baffles. Bed temperature measurements along the length of the heat exchanger were experimentally obtained and heat balances for differential control volumes of the heat exchanger were made in order to obtain the axial profile of the bed-to-tube heat transfer coefficient. The results showed that heat transfer coefficient increases with the solid particle mass flow rate and with the presence of baffles, suggesting that these are important factors to be considered in the design of such heat exchanger.

Pécora, Araí A. Bernárdez; Parise, Maria Regina.

358

Radiation induced surface activation on heat transfer enhancement  

International Nuclear Information System (INIS)

Improving the limit of boiling heat transfer or critical heat flux requires that the cooling liquid can contact the heating surface, or a high-wettability, highly hydrophilic heating surface, even if a vapor bubble layer is generated on the surface. From this basis, we investigated surface wettability and heat transfer phenomena using metal oxides irradiated by ?-rays. First, contact angle, an indicator of macroscopic wettability, of a water droplet on metal oxide at room temperature was measured by image processing of the images obtained by a CCD video camera. The results showed that the surface wettability on metal oxide pieces of titanium, zircaloy No. 4 SUS-304, and copper was improved significantly by the Radiation Induced Surface Activation (RISA) phenomenon. Highly hydrophilic conditions of the test pieces were achieved after 500-kGy irradiation by 60Co ?-rays. After the end of irradiation, the contact angle decreased. Second, to delineate the effect of Radiation Induced Surface Activation (RISA) on heat transferring phenomena, the Leidenfrost condition and quenching of metal oxides irradiated by ?-rays were investigated in this study. In the Leidenfrost experiment, when the temperature of the heating surface reached the wetting limit temperature, water-solid contact vanished because a stable vapor film existed between the droplet and the metal surface; i.e., a Leidenfrost condition obtained. The wetting limit temperature increased with integrated irradiation dose. After irradiation, the wet length and the duration of contact increased, and the contact angle decreased. In the quenching test, high surface wettability, or a highly hydrophilic condition, of a simulated fuel rod made of SUS was achieved, and the quenching velocities were increased up to 20 30% after 300 kGy 60Co ?-ray irradiation. (author)

2004-12-01

359

The effect of ambient temperature on the shoe-surface interface release coefficient.  

Science.gov (United States)

Previous studies of the shoe-surface interface correlated foot fixation with cleat length, configuration, and material composition as well as turf type and surface conditions. Our study examined the effect of temperature on the rotational torsion resistance of artificial turf football shoes. Five football shoe models, a flat-soled basketball-style turf shoe, a natural grass soccer-style shoe, and three multistudded turf shoes, were studied on dry Astro Turf at five temperatures (range, 52 degrees F to 110 degrees F). An assay device, a prosthetic foot mounted on a loaded stainless steel shaft, was used to determine the force necessary to release a shoe from the turf's surface. We used a torque wrench to apply a rotational force so that each shoe was pivoted counterclockwise through an arc of 60 degrees. Our results indicated that release coefficients differ within and among the shoe models at various turf temperatures. We also found that an increase in turf temperature, in combination with cleat characteristics, affects shoe-surface interface friction and potentially places the athlete's knee and ankle at risk of injury. Based on an established risk criterion, which correlated shoe-surface interface combinations in the laboratory with documented clinical occurrences, only the flat-soled basketball-style turf shoe could be designated "safe" or "probably safe" at all five temperatures. PMID:8638758

Torg, J S; Stilwell, G; Rogers, K

1996-01-01

360

Analysis of accommodation coefficients of noble gases on aluminum surface with an experimental/computational method  

Science.gov (United States)

A method that connects measurements of radiometric forces on a heated vane in the transitional flow regime with the kinetic modeling of the flow, and derives the accommodation coefficients through the successive analysis of measured and computed results, is proposed. The method utilizes the fact that radiometric forces exerted on heated objects immersed in rarefied gases are governed by the interaction of gas molecules with the surface. Experimental results on radiometric forces on a 0.11 m diameter circular vane are obtained on a nano-Newton thrust stand in a 3 m long vacuum chamber for pressures ranging from approximately 0.01 to 1 Pa. The vane was heated to 419 K on the hot side and 396 K on the cold side. The numerical modeling is conducted using a combined ellipsoidal statistical Bhatnagar-Gross-Krook/direct simulation Monte Carlo approach that allows accurate and time efficient analysis of radiometric forces on a vane in large vacuum chambers filled with rarefied gas. Accommodation coefficients for the Maxwell model are estimated for argon, xenon, and helium on a machined aluminum surface, and found to be 0.81, 0.86, and 0.53, respectively.

Selden, Nathaniel; Gimelshein, Natalia; Gimelshein, Sergey; Ketsdever, Andrew

2009-07-01

 
 
 
 
361

Determining the moderator temperature coefficient by fitting the noise analysis transfer function  

International Nuclear Information System (INIS)

Previous researchers have established that the value of the moderator temperature coefficient (MTC) of reactivity is contained in correlations between fluctuations of the neutron flux and core-exit coolant temperature. Both the root-mean-square method and the frequency response function (FRF) technique are used to determine the absolute magnitude of the MTC. Normally, these methods are used in conjunction with the phase angle technique, which is used to ascertain the MTC sign; however, a recent study has determined that a boundary exists on the range of MTC values for which the phase angle from noise analysis can be used. This paper describes a fitting method to determine both the MTC sign and magnitude in a single analysis in order to overcome such limitations

1993-11-14

362

Effect of Soft Material Hardness and Hard Material Surface Morphology on Friction and Transfer Layer Formation; Lubricated Condition  

Directory of Open Access Journals (Sweden)

Full Text Available Hot and cold forming of metals is carried out in industry for manufacturing engineering components. Such manufacturing processes employ dies, whose surface condition is one of the factors which characterize the surface finish of engineering components. The surface finish of engineering components is largely influenced by the tribological phenomenon at die and components interface. Lubrication, morphology and hardness of die surface are found to control surface finish of the products. In the present investigation a pin-on-plate sliding tester was used to identify the effect of surface morphology, lubrication and hardness on co-efficient of friction and transfer layer which characterizes the tribological behaviour. The morphology of mild steel (EN8 plate surfaces were modified by employing three different surface modification methods like grinding (silicon carbide wheel polishing, shot blasting and electric discharge machining methods. Surface roughness parameters which characterize the morphology of the steel plates were measured using a three dimensional optical profilometer. Role of hardness is studied by employing lead, copper and Aluminum (Al6082 pins which were slid against steel plates. Experiments were conducted for plate inclination angles of 1, 1.5,2 and 2.5 degrees. Normal load was varied from 1 to 150N during the tests. Experiments were conducted under lubricated condition in ambient environment. Scanning electron microscope was used to study the formation of transfer layer on plate and pin surfaces. It was observed that the co-efficient of friction and transfer layer formation were found to depend on the surface morphology of the harder surface under lubricated condition. The quantum of transfer layer formation on the surfaces is found to increase with increase in surface roughness.

Dr.S Ranganatha

2013-09-01

363

Combined measurement of surface, grain boundary and lattice diffusion coefficients on olivine bi-crystals  

Science.gov (United States)

Diffusion along interface and grain boundaries provides an efficient pathway and may control chemical transport in rocks as well as their mechanical strength. Besides the significant relevance of these diffusion processes for various geologic processes, experimental data are still very limited (e.g., Dohmen & Milke, 2010). Most of these data were measured using polycrystalline materials and the formalism of LeClaire (1951) to fit integrated concentration depth profiles. To correctly apply this formalism, certain boundary conditions of the diffusion problem need to be fulfilled, e.g., surface diffusion is ignored, and furthermore the lattice diffusion coefficient has to be known from other studies or is an additional fitting parameter, which produces some ambiguity in the derived grain boundary diffusion coefficients. We developed an experimental setup where we can measure the lattice and grain boundary diffusion coefficients simultaneously but independent and demonstrate the relevance of surface diffusion for typical grain boundary diffusion experiments. We performed Mg2SiO4 bicrystal diffusion experiments, where a single grain boundary is covered by a thin-film of pure Ni2SiO4 acting as diffusant source, produced by pulsed laser deposition. The investigated grain boundary is a 60° (011)/[100]. This specific grain boundary configuration was modeled using molecular dynamics for comparison with the experimental observations in the transmission electron microscope (TEM). Both, experiment and model are in good agreement regarding the misorientation, whereas there are still some disagreements regarding the strain fields along the grain boundary that are of outmost importance for the strengths of the material. The subsequent diffusion experiments were carried out in the temperature range between 800° and 1450° C. The inter diffusion profiles were measured using the TEMs energy dispersive x-ray spectrometer standardized using the Cliff-Lorimer equation and EMPA measurements. To evaluate the obtained diffusion profiles we adapted the isolated grain boundary model, first proposed by Fisher (1951) to match several observations: (i) Anisotropic diffusion in forsterite, (ii) fast diffusion along the grain boundary, (iii) fast diffusion on the surface of the sample. The latter process is needed to explain an additional flux of material from the surface into the grain boundary. Surface and grain boundary diffusion coefficients are on the order of 10000 times faster than diffusion in the lattice. Another observation was that in some regions the diffusion profiles in the lattice were greatly extended. TEM observations suggest here that surface defects (nano-cracks, ect.) have been present, which apparently enhanced the diffusion through the bulk lattice. Dohmen, R., & Milke, R. (2010). Diffusion in Polycrystalline Materials: Grain Boundaries, Mathematical Models, and Experimental Data. Reviews in Mineralogy and Geochemistry, 72(1), 921-970. Fisher, J. C. (1951). Calculations of Diffusion Penetration Curves for Surface and Grain Boundary Diffusion. Journal of Applied Physics, 22(1), 74-77. Le Claire, A. D. (1951). Grain boundary diffusion in metals. Philosophical Magazine A, 42(328), 468-474.

Marquardt, Katharina; Dohmen, Ralf; Wagner, Johannes

2014-05-01

364

Analytic approach to charge transfer during atom-surface scattering  

Energy Technology Data Exchange (ETDEWEB)

We present an analytic approach to the solution of the time-dependent Newns-Anderson model of charge transfer during atom-surface scattering. For sufficiently slow atomic velocities we show, using a WKB technique, that the time evolution of the electronic state of the atom is determined by the instantaneous quasiparticle energies of the coupled atom plus surface system. Surface electronic structure and level-crossing effects are thus incorporated into the theory in a natural way. The results of the analysis compare quite favorably with numerical solutions and recently discovered exact solutions.

Dorsey, A.T.; Jacobsen, K.W.; Levine, Z.H.; Wilkins, J.W. (Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501 (US))

1989-08-15

365

Heat transfer between a nano-tip and a surface  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study quasi-ballistic heat transfer through air between a hot nanometer-scale tip and a sample. The hot tip/surface configuration is widely used to perform nonintrusive confined heating. Using a Monte-Carlo simulation, we find that the thermal conductance reaches 0.8 MW.m-2K-1 on the surface under the tip and show the shape of the heat flux density distribution (nanometer-scale thermal spot). These results show that a surface can be efficiently heated locally without contact. The temporal ...

2006-01-01

366

Effects of mesoscale surface inhomogeneities on atmospheric boundary layer transfer  

Energy Technology Data Exchange (ETDEWEB)

Defining the nature of turbulent transfer over horizontally inhomogeneous surfaces remains one of the challenges in meteorology. Because the transfer of energy and momentum through the atmospheric boundary layer forms part of the lower boundary condition for global climate models (GCMs), the problem is important. Over the last two decades, advances in sensor and computer technology wave made good point measurements of turbulent fluxes fairly routine. A fundamental question with respect to climate models, however, is how such point measurements are related to average fluxes over the area of a GCM grid box. In this paper we will use data from the field program to depict the evolution of the boundary layer over adjacent, sharply contrasting surface types on two separate occasions. We will then use simple scaling based on the observations to argue that sub-gridscale motions would often be likely to significantly alter the estimates and resulting parameterizations of GCM-scale surface fluxes in the region.

Shaw, W.J.; Doran, J.C.; Hubbe, J.M.

1992-09-01

367

Numerical Calculation of the Added Mass and Damping Coefficients of Cylinders Oscillating in or Below a Free Surface.  

Science.gov (United States)

The computer program presented herein provides values of the added mass and damping coefficients of infinitely long horizontal cylinders oscillating in or below a free surface. The report includes the theoretical background, the general structure, the det...

J. W. Bedel C. M. Lee

1971-01-01

368

Study of Pool Boiling Heat Transfer on Various Surfaces with Variation of Flow Velocity  

Energy Technology Data Exchange (ETDEWEB)

In this study, a smooth flat surface, low fin, Turbo-B, and Thermo excel-E surfaces are used to examine the effect of the flow velocity on the pool boiling heat transfer coefficients (HTSC) and critical heat fluxes (Chefs). HTSC and Chefs are measured on a smooth square heater of 9.53 {Chi} 9.53 m2 at 60 .deg. C in a pool of pure water at various fluid velocities of 0, 0.1, 0.15, and 0.2 m/s. Test results show that for all surfaces, Chefs obtained with flow are higher than those obtained without flow. Chefs of the low fin surface are higher than those of the Turbo-B and Thermo excel-E surfaces due largely to the increase in surface area and sufficient fin spaces for the easy removal of bubbles. Chefs of the low fin surface show even 5 times higher Chefs as compared to the plain surface. On the other hand, both Turbo-B and Thermo excel-E surfaces do not show satisfactory results because their pore sizes are too small and water bubbles easily cover them. At low heat fluxes of less than 50 k W/m2, HTSC increase as the flow velocity increases for all surfaces. In conclusion, a low fin geometry is good for application to steam generators in nuclear power plants.

Kang, Donggyu; Lee, Yohan; Seo, Hoon; Jung, Dongsoo [Inha Univ., Incheon (Korea, Republic of)

2013-04-15

369

A Survey of Ballistic Transfers to the Lunar Surface  

Science.gov (United States)

In this study techniques are developed which allow an analysis of a range of different types of transfer trajectories from the Earth to the lunar surface. Trajectories ranging from those obtained using the invariant manifolds of unstable orbits to those derived from collision orbits are analyzed. These techniques allow the computation of trajectories encompassing low-energy trajectories as well as more direct transfers. The range of possible trajectory options is summarized, and a broad range of trajectories that exist as a result of the Sun's influence are computed and analyzed. The results are then classified by type, and trades between different measures of cost are discussed.

Anderson, Rodney L.; Parker, Jeffrey S.

2011-01-01

370

Determination of the diffusion coefficient and phase-transfer rate parameter in LaNi{sub 5} and MmNi{sub 3.6}Co{sub 0.8}Mn{sub 0.4}Al{sub 0.3} using microelectrodes  

Energy Technology Data Exchange (ETDEWEB)

A potential-step method for determining the diffusion coefficient and phase-transfer parameter in metal hydrides by using microelectrodes was investigated. It was shown that a large potential step is not enough to ensure a completely diffusion-limited mass transfer if a surface-phase transfer reaction takes place at a finite rate. It was shown, using a kinetic expression for the surface phase-transfer reaction, that the slope of the logarithm of the current vs. time curve will be constant both in the case of the mass-transfer limited by diffusion or by diffusion and a surface-phase transfer. The diffusion coefficient and phase-transfer rate parameter were accurately determined for MmNi{sub 3.6}Co{sub 0.8}Mn{sub 0.4}Al{sub 0.3} using a fit to the whole transient. The diffusion coefficient was found to be (1.3 {+-} 0.3) {times} 10{sup {minus}13} m{sup 2}/s. The fit was good and showed that a pure diffusion model was not enough to explain the observed transient. The diffusion coefficient and phase-transfer rate parameter were also estimated for pure LaNi{sub 5}. A fit of the whole curve showed that neither a pure diffusion model nor a model including phase transfer could explain the whole transient.

Lundqvist, A.; Lindbergh, G. [Royal Inst. of Tech., Stockholm (Sweden)

1998-11-01

371

On the determination of fission product mass transfer coefficients in some parts of reactor cooling system circuits at NPP with RBMK-1000  

International Nuclear Information System (INIS)

Expressions to determine the coefficients of nuclide washing-off and deposition on the reactor circuit pipe walls are derived, which are used in mathematical models, describing mass transfer of radioactive impurities over the circuit. On the basis of experimental data on nuclide activity in the depositions and coolant, the empirical values of mass transfer coefficient (MC) in lowering and suction manifold are obtained. The suggested method of radionuclide MC determination gives positive results, and MC evaluations, obtained with its help, reflect adequately the mass transfer process

1985-01-01

372

Contraction heat transfer coefficient correlation for rectangular pin fin heat sinks  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The demand for smaller but more powerful electronic components is ever increasing. This demand puts a strain on engineers to produce optimal cooling designs for these electronic components. One method for cooling these electronic components is with heat sinks which effectively increase the surface area available for extracting the heat from the electronic components. Computational Fluid Dynamics (CFD) software is sometimes used to aid in the design process, but CFD simulations are computation...

2011-01-01

373

Experimental Investigation of Convective Heat Transfer during Night Cooling with Different Ventilation Systems and Surface Emissivities  

DEFF Research Database (Denmark)

Night-time ventilation is a promising approach to reduce the energy needed for cooling buildings without reducing thermal comfort. Nevertheless actual building simulation tools have showed their limits in predicting accurately the efficiency of night-time ventilation, mainly due to inappropriate models for convection. In a full-scale test room, the heat transfer was investigated during 12 h of discharge by night-time ventilation. A total of 34 experiments have been performed, with different ventilation types (mixing and displacement), air change rates, temperature differences between the inlet air and the room, and floor emissivities. This extensive experimental study enabled a detailed analysis of the convective and radiative flow at the different surfaces of the room. The experimentally derived convective heat transfer coefficients (CHTC) have been compared to existing correlations. For mixing ventilation, existing correlations did not predict accurately the convective heat transfer at the ceiling due to differences in the experimental conditions. But the use of local parameters of the air flow showed interesting results to obtain more adaptive CHTC correlations. For displacement ventilation, the convective heat transfer was well predicted by existing correlations. Nevertheless the change of floor emissivity influenced the CHTC at the surface of interest.

Le Dreau, Jerome; Heiselberg, Per

2013-01-01

374

Convective and boiling heat transfer from a heated surface to an impinging, planar jet of water  

Energy Technology Data Exchange (ETDEWEB)

Cooling of hot rolled steel strip is often accomplished with planar, impinging jets of water. Liquid jet cooling is also well suited for dissipating the heat generated by microelectronic circuits. Although thorough studies of transport processes in impinging gas jets have been performed, the data base and predictive methods for impinging liquid jets are relatively undeveloped. The important heat transfer mechanism for liquid jet cooling have not been identified. Boiling studies have been limited to the region directly beneath the jet. Methods and equipment were developed for measuring the heat transfer to an impinging liquid jet. The rationale for each approach was documented. Alternative methods and designs are also described. The results of this study include local heat transfer coefficients for single phase convection, partial boiling and fully developed nucleate boiling. Heat transfer in the laminar boundary layer was shown to be sensitive to free stream turbulence. The response of boiling and nonboiling heat transfer processes to changes in the heat flux, flow rate and fluid temperature are described on the basis of surface temperature data and the results of a photographic study.

Vader, D.T.

1988-01-01

375

Contribution to the study of heat transfer coefficients during the decompression of a water cooled heating tube  

International Nuclear Information System (INIS)

The main correlations likely to be suitable for describing heat transfers between the fluid and wall during decompression are analyzed. The most important experimental work on the boiling crisis in the transient regime is presented. Experimental studies are then treated. The test installation (OMEGA experiment), the instumentation used and the experiments realized are described. The purpose of these experiments was to establish heat exchange laws for decompression conditions. Local and instantaneous exchange coefficients were determined in a heated test section together with the thermohydraulic parameters of the flow. The methods used to investigate the measurements made and to analyze their validity are described. Finally, the test results are presented and discussed. It is shown that under certain conditions, the boiling crisis can be determined with a permanent regime correlation. An attempt is made to establish a correlation for the transition boiling zone from these results. A test reconstitution calculation based on a two-fluid model is presented

1980-01-01

376

Surface conductivity of the diamond: A novel transfer doping mechanism  

International Nuclear Information System (INIS)

A novel doping mechanism is presented for the case of diamond that does not rely on the incorporation of dopant atoms into the crystal lattice as in conventional doping. Instead, adsorbates provide the acceptor level into which electrons are transferred, leading to a two-dimensional subsurface hole accumulation layer with an areal concentration of up to 1013 cm-2. Two acceptor systems are discussed. One is based on the charge exchange between diamond and solvated H+ ions in a water layer that forms spontaneously on all surfaces in air. The other relies on the high electron affinity of fullerenes and fluorinated fullerenes that act as efficient acceptors when physisorbed at the surface. In either case, the extremely low ionization energy of hydrogen terminated diamond that is matched by no other semiconductor is a necessary requirement for transfer doping

2006-04-01

377

Large-eddy simulations of leading edge film cooling: Analysis of flow structures, effectiveness, and heat transfer coefficient  

International Nuclear Information System (INIS)

A numerical investigation is conducted to study leading edge film cooling with large eddy simulation (LES). The domain geometry is adopted from an experimental setup of [Ekkad, S.V., Han, J.C., Du, H., 1998. Detailed film cooling measurement on a cylindrical leading edge model: Effect of free-stream turbulence and coolant density. Journal of Turbomachinery 120, 799-807.] where turbine blade leading edge is represented by a semi-cylindrical blunt body with compound angle of injection. At blowing ratio of 0.4 and coolant to mainstream density ratio of unity, a laminar constant velocity and fully-turbulent coolant jet are studied. In both cases, the results show the existence of an asymmetric counter-rotating vortex pair in the immediate wake of the coolant jet. In addition to these primary structures, vortex tubes on the windward side of the jet are convected downstream over and to the aft- and fore-side of the counter-rotating vortex pair. All these structures play a role in the mixing of mainstream fluid with the coolant. The fully-turbulent coolant jet increases mixing with the mainstream in the outer shear layer but does not directly influence the flow dynamics in the turbulent boundary layer which forms within two coolant hole diameters of injection. As a result, the turbulent jet decreases adiabatic effectiveness but does not have a substantial effect on the heat transfer coefficient. The span-wise averaged adiabatic effectiveness agrees well with experiments for a turbulent coolant jet, without which the calculated effectiveness is over-predicted. On the other hand, the heat transfer coefficient which is only a function of near wall turbulence, shows good agreement with experiments for both coolant jet inlet conditions

2008-02-01

378

Large-eddy simulations of leading edge film cooling: Analysis of flow structures, effectiveness, and heat transfer coefficient  

Energy Technology Data Exchange (ETDEWEB)

A numerical investigation is conducted to study leading edge film cooling with large eddy simulation (LES). The domain geometry is adopted from an experimental setup of [Ekkad, S.V., Han, J.C., Du, H., 1998. Detailed film cooling measurement on a cylindrical leading edge model: Effect of free-stream turbulence and coolant density. Journal of Turbomachinery 120, 799-807.] where turbine blade leading edge is represented by a semi-cylindrical blunt body with compound angle of injection. At blowing ratio of 0.4 and coolant to mainstream density ratio of unity, a laminar constant velocity and fully-turbulent coolant jet are studied. In both cases, the results show the existence of an asymmetric counter-rotating vortex pair in the immediate wake of the coolant jet. In addition to these primary structures, vortex tubes on the windward side of the jet are convected downstream over and to the aft- and fore-side of the counter-rotating vortex pair. All these structures play a role in the mixing of mainstream fluid with the coolant. The fully-turbulent coolant jet increases mixing with the mainstream in the outer shear layer but does not directly influence the flow dynamics in the turbulent boundary layer which forms within two coolant hole diameters of injection. As a result, the turbulent jet decreases adiabatic effectiveness but does not have a substantial effect on the heat transfer coefficient. The span-wise averaged adiabatic effectiveness agrees well with experiments for a turbulent coolant jet, without which the calculated effectiveness is over-predicted. On the other hand, the heat transfer coefficient which is only a function of near wall turbulence, shows good agreement with experiments for both coolant jet inlet conditions.

Rozati, Ali [Mechanical Engineering Department, Virginia Polytechnic Institute and State University, 114-I Randolph Hall, Mail code 0238, Blacksburg, VA 24061 (United States); Tafti, Danesh K. [Mechanical Engineering Department, Virginia Polytechnic Institute and State University, 114-I Randolph Hall, Mail code 0238, Blacksburg, VA 24061 (United States)], E-mail: dtafti@vt.edu

2008-02-15

379

Heat transfer crisis on sintered porous surfaces – experimental investigations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

There were presented the results of theoretical analysis of boiling heat transfer on heating surfaces covered with thin-layered capillary porous structures. The paper discussed the results of experimental investigations into intralayer boiling crisis and accompanying phenomena. It was observed that the structural parameters of the porous covering affected the course of the process. Hysteresis phenomenon manifested itself when the heat flux initiating intralayer heat crisis was reached. The cr...

Wojcik Tadeusz Michal

2012-01-01

380

Study on mist cooling for a superheated surface. Effect of grooved surface on heat transfer  

International Nuclear Information System (INIS)

In order to pursue the enhancement and control of mist cooling heat transfer by the grooved surface, detailed experiments have been conducted with regard to the boiling and evaporation of liquid film formed on the circular superheated surface with the concentric and/or radial groove. The experimental results indicate that the concentric grooved surface is more effective in the enhancement and stability of mist cooling heat transfer, and a optimum spray condition is given as a relation between spray mass flow rate and superheat degree. (author)

1994-05-01

 
 
 
 
381

Flow and heat transfer regimes during quenching of hot surfaces  

International Nuclear Information System (INIS)

Reflooding experiments have been performed to study flow and heat transfer regimes in a heated annular vertical channel under supercooled inlet conditions. A gamma densitometer was employed to determine the void fraction as a function of the distance from the quench front. Surface heat fluxes were determined by fast measurements of the temperature spatial distribution. Two quench front is shown to lie in the transition boiling region which spreads into the dry and wet segments of the heated surface. (authors) 5 refs, 3 figs

1993-05-18

382

Heat Transfer Enhancement By Three-Dimensional Surface Roughness Technique In Nuclear Fuel Rod Bundles  

Science.gov (United States)

This thesis experimentally investigates the enhancement of single-phase heat transfer, frictional loss and pressure drop characteristics in a Single Heater Element Loop Tester (SHELT). The heater element simulates a single fuel rod for Pressurized Nuclear reactor. In this experimental investigation, the effect of the outer surface roughness of a simulated nuclear rod bundle was studied. The outer surface of a simulated fuel rod was created with a three-dimensional (Diamond-shaped blocks) surface roughness. The angle of corrugation for each diamond was 45 degrees. The length of each side of a diamond block is 1 mm. The depth of each diamond block was 0.3 mm. The pitch of the pattern was 1.614 mm. The simulated fuel rod had an outside diameter of 9.5 mm and wall thickness of 1.5 mm and was placed in a test-section made of 38.1 mm inner diameter, wall thickness 6.35 mm aluminum pipe. The Simulated fuel rod was made of Nickel 200 and Inconel 625 materials. The fuel rod was connected to 10 KW DC power supply. The Inconel 625 material of the rod with an electrical resistance of 32.3 kO was used to generate heat inside the test-section. The heat energy dissipated from the Inconel tube due to the flow of electrical current flows into the working fluid across the rod at constant heat flux conditions. The DI water was employed as working fluid for this experimental investigation. The temperature and pressure readings for both smooth and rough regions of the fuel rod were recorded and compared later to find enhancement in heat transfer coefficient and increment in the pressure drops. Tests were conducted for Reynold's Numbers ranging from 10e4 to 10e5. Enhancement in heat transfer coefficient at all Re was recorded. The maximum heat transfer co-efficient enhancement recorded was 86% at Re = 4.18e5. It was also observed that the pressure drop and friction factor increased by 14.7% due to the increased surface roughness.

Najeeb, Umair

383

Improvement of Reactor Fuel Element Heat Transfer by Surface Roughness  

International Nuclear Information System (INIS)

In heat exchangers with a limited surface temperature such as reactor fuel elements, rough heat transfer surfaces may give lower pumping power than smooth. To obtain data for choice of the most advantageous roughness for the superheater elements in the Marviken reactor, measurements were made of heat transfer and pressure drop in an annular channel with a smooth or rough test rod in a smooth adiabatic shroud. 24 different roughness geometries were tested. The results were transformed to rod cluster geometry by the method of W B Hall, and correlated by the friction and heat transfer similarity laws as suggested by D F Dipprey and R H Sabersky with RMS errors of 12.5 % in the friction factor and 8.1 % in the Stanton number. The relation between the Stanton number and the friction factor could be described by a relation of the type suggested by W Nunner, with a mean error of 3.1 % and an RMS error of 11.6 %. Application of the results to fuel element calculations is discussed, and the great gains in economy which can be obtained with rough surfaces are demonstrated by two examples

1967-01-01

384

Determinación del Coeficiente de Transferencia de Calor a Través de una Aplicación de Computadoras / Determination of Heat Transfer Coefficient through Computer Application  

Scientific Electronic Library Online (English)

Full Text Available SciELO Chile | Language: Spanish Abstract in spanish Se describe un procedimiento de evaluación del coeficiente de transferencia de calor en operaciones industriales. Se presenta un modelo matemático sencillo de determinación del coeficiente convectivo de transferencia de calor usando el software DCAL (Determinación de Coeficiente de Transferencia de [...] Calor durante un Calentamiento). Para validar el modelo se usaron datos experimentales de muestras procesadas por tratamiento térmico, utilizando diferentes temperaturas y tiempos de proceso. Los datos experimentales fueron procesados automáticamente por el software, para la generación de gráficas y determinación de un coeficiente de transferencia de calor optimizado. Se concluye que la metodología descrita sirve para el cálculo del coeficiente convectivo cuando no hay resistencia interna a la transferencia de calor. Abstract in english The evaluation of the heat transfer coefficient for its use in industrial operations is described. A simple mathematical model to determine the heat transfer convective coefficient using the DCAL software (Determination of Heat Transfer Coefficient during a Heating). To valídate the model experiment [...] al data of samples processed by thermal treatment using different temperatures and process time were used. The experimental data was automatically processed by the software, to genérate graphs and to determine an optimum heat transfer coefficient. The main conclusión was that the methodology described is useful to the compute of convective coefficient when there is no inside heat transfer resistance.

Armando, Alvis; Isaac, Caicedo; Pierre, Peña.

385

Determinación del Coeficiente de Transferencia de Calor a Través de una Aplicación de Computadoras Determination of Heat Transfer Coefficient through Computer Application  

Directory of Open Access Journals (Sweden)

Full Text Available Se describe un procedimiento de evaluación del coeficiente de transferencia de calor en operaciones industriales. Se presenta un modelo matemático sencillo de determinación del coeficiente convectivo de transferencia de calor usando el software DCAL (Determinación de Coeficiente de Transferencia de Calor durante un Calentamiento. Para validar el modelo se usaron datos experimentales de muestras procesadas por tratamiento térmico, utilizando diferentes temperaturas y tiempos de proceso. Los datos experimentales fueron procesados automáticamente por el software, para la generación de gráficas y determinación de un coeficiente de transferencia de calor optimizado. Se concluye que la metodología descrita sirve para el cálculo del coeficiente convectivo cuando no hay resistencia interna a la transferencia de calor.The evaluation of the heat transfer coefficient for its use in industrial operations is described. A simple mathematical model to determine the heat transfer convective coefficient using the DCAL software (Determination of Heat Transfer Coefficient during a Heating. To valídate the model experimental data of samples processed by thermal treatment using different temperatures and process time were used. The experimental data was automatically processed by the software, to genérate graphs and to determine an optimum heat transfer coefficient. The main conclusión was that the methodology described is useful to the compute of convective coefficient when there is no inside heat transfer resistance.

Armando Alvis

2010-01-01

386

Method to allow the estimation of heat transfer coefficients in solar stills; Metodo para determinar coeficientes locales de transferencia de calor en destiladores solares  

Energy Technology Data Exchange (ETDEWEB)

This work reports an experimental method that allows to estimate the heat transfer coefficients in the neighborhood of walls or flat plates subject to convective transport phenomena. This method can be applied to a great variety of thermal systems since it is based on the knowledge of the border condition for the temperature at the surface of the plate, and the temperature profile that characterize the dimensionless coefficient of heat transfer in the fluid, according to its definition given by the Nusselt number. The approach of this work are the foundations of the method and the system that has been developed to apply it, that incorporates automatic acquisition equipment for continuos monitoring of the information and elements to control the parameters of interest. In addition, the experimental cavities on which the method will be evaluated are discussed, considering two different scales, as well as experiments in cavities filled with air, and with a mixture of air and steam water, as is the case for solar distillation. [Spanish] En este trabajo se presenta un metodo que permite determinar de manera experimental coeficientes de transferencia de calor por conveccion. Este metodo puede ser aplicado a una gran variedad de sistemas termicos ya que se fundamenta en el conocimiento de la condicion de frontera para la temperatura en la superficie de la placa, y del perfil de temperaturas que caracteriza el coeficiente adimensional de transferencia de calor en el fluido, de acuerdo a la definicion de este, dada por el numero de Nusselt. El trabajo que aqui se reporta esta enfocado a la fundamentacion del metodo y al equipamiento que se ha desarrollado para instrumentarlo, que incorpora equipos automaticos de adquisicion continua de informacion y elementos de control para los parametros de interes. Se presentan ademas, las cavidades experimentales sobre las que sera evaluado el metodo, que considera dos escalas diferentes, asi como experimentos en cavidades llenas de aire, y con una mezcla de aire-vapor de agua, como es el caso de la destilacion solar.

Rubio Cerda, Eduardo; Porta Gandara, Miguel A [CIBNOR, Mexico D.F (Mexico); Fernandez Zayas, Jose Luis [UNAM Mexico, D.F. (Mexico)

2000-07-01

387

Thermal analysis of a longitudinal trapezoidal fin with temperature-dependent thermal conductivity and heat transfer coefficient  

Science.gov (United States)

A homotopy analysis method (HAM) is used to develop analytical solution for the thermal performance of a straight fin of trapezoidal profile when both the thermal conductivity and the heat transfer coefficient are temperature dependent. Results are presented for the temperature distribution, heat transfer rate, and fin efficiency for a range of values of parameters appearing in the mathematical model. Since the HAM algorithm contains a parameter that controls the convergence and accuracy of the solution, its results can be verified internally by calculating the residual error. The HAM results were also found to be accurate to at least three places of decimal compared with the direct numerical solution of the mathematical model generated using a fourth-fifth-order Runge-Kutta-Fehlberg method. The HAM solution appears in terms of algebraic expressions which are not only easy to compute but also give highly accurate results covering a wide range of values of the parameters rather than the small values dictated by the perturbation solution.

Khani, F.; Aziz, Abdul

2010-03-01

388

Application of EoEP principle with variable heat transfer coefficient in minimizing entropy production in heat exchangers  

International Nuclear Information System (INIS)

A more realistic application of the entropy minimization principle EoEP is presented. This principle dictates uniform local entropy generations along the heat exchanger in order to minimize the total entropy generation rate due only to heat transfer. For a certain heat duty and area of an existing exchanger, this is done by changing the temperatures of one fluid while the temperatures of the other fluid are held constant. Since the heat duty is fixed, the change in the temperatures of the fluid after the change, however, may sometimes cause a drastic change in its flow rate. This may cause considerable changes in the overall heat transfer coefficient (U) and, consequently, in the entropy generation rate. Depending on the choice of the fluid for changing, the new entropy generation rates may be higher or lower than those based on constant U as is the case in papers recently published. So, the classical application of the EoEP principle needs to be modified to achieve more realistic entropy generation rates. In this study, the principle of EoEP with variable U is applied to some cases of heat exchange, and a simple method is presented as a criterion for the proper choice of the fluid to be changed

2005-08-01

389

Performance evaluation of a vortex generator heat transfer surface and comparison with different high performance surfaces  

International Nuclear Information System (INIS)

A comparative assessment of five different heat transfer configurations for operation in compact heat exchangers is presented. The configurations under consideration are four standaed heat exchanger surfaces - two plain fin, an offset strip and a louvered fin geometry - and one surface with so called vortex generators for heat transfer augmentation. In the case of the standard surfaces, the basic performance characteristics in the form of heat transfer and friction data versus the Reynolds number have been taken from published experimental results. In the case of the vortex generator surface, the performance characteristics have been derived from a numerical prediction of the flow and temperature field in a closely spaced parallel plate channel with vortex generators in the form of delta wings mounted on the channel walls. In comparison to the plain fin surfaces with a rectangular cross section, the vortex generator surface shows best performance characteristics allowing a reduction in heat transfer surface area of 76%, for fixed heat duty and for fixed pumping power. (Author)

1993-07-01

390

Condensation heat transfer on vertical axis, axisymmetric, rotating surfaces  

International Nuclear Information System (INIS)

Rotating heatpipes make use of centrifugal effects to return id from the condenser to the evaporator without a wick. Daniels and al-Jumaily, Maezawa et al., and Marto used a Nusselt-type analysis for heat pipes rotating about a horizontal axis. Faghri et al. analyzed the vapor flow in a horizontal rotating heat pipe with a constant radius by numerically solving the momentum and energy equations. In a related area, condensation on rotating disks and cones has been modeled and similarity solutions found for temperature, tangential velocity, and pressure fields that are independent of the radius. Nandapurkar and Beatty experimentally determined average heat transfer coefficients for condensation on vertical axis rotating disks. 10 refs., 4 figs

1995-08-01

391

Development of an inverse heat conduction model and its application to determination of heat transfer coefficient during casting solidification  

Science.gov (United States)

The interfacial heat transfer coefficient (IHTC) is required for the accurate simulation of heat transfer in castings especially for near net-shape processes. The large number of factors influencing heat transfer renders quantification by theoretical means a challenge. Likewise experimental methods applied directly to temperature data collected from castings are also a challenge to interpret because of the transient nature of many casting processes. Inverse methods offer a solution and have been applied successfully to predict the IHTC in many cases. However, most inverse approaches thus far focus on use of in-mold temperature data, which may be a challenge to obtain in cases where the molds are water-cooled. Methods based on temperature data from the casting have the potential to be used however; the latent heat released during the solidification of the molten metal complicates the associated IHTC calculations. Furthermore, there are limits on the maximum distance the thermocouples can be placed from the interface under analysis. An inverse conduction based method have been developed, verified and applied successfully to temperature data collected from within an aluminum casting in proximity to the mold. A modified specific heat method was used to account for latent heat evolution in w