bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrohydrodynamic Ridge Instability of a Thin Film Flowing Down an Inclined Plate
Authors: Lee Chung-Oh , Choi H. Y.
Published: February 2012

In the flow of a thin liquid film, ridge-type instability occurs in a wide variety of engineering systems. These are instability waves whose crests are parallel to the flow direction. Ridges have also been observed when a flowing film is stressed by an electric field applied normal to the interface. It is shown that in this case also the instability is essentially of a hydrodynamic nature and an analysis is presented explaining when and why ridges occur. In the analysis, the three-dimensional Orr-Sommerfeld equation is solved by the method of successive approximations in terms of small Reynolds numbers. The theory for ridge instability further takes into account the finite electrical conductivity of the liquid film, showing the limit of validity of the simplified theories in the literature for perfectly conducting interface and ideally polarized interface. Experimental results are presented supporting the theory.
The Void Fraction in Subcooled Boiling—Prediction of the Initial Point of Net Vapor Generation
Authors: Staub F. W.
Published: February 2012

The satisfactory prediction of the vapor volume fraction in subcooled boiling depends in large part on the ability to predict the point where a significant amount of net vapor is first formed. A method for the prediction of this point is derived here and compared with experimental measurements at both low and high fluid velocities. The derived relationships for this point include the effect of fluid properties, geometry, and the liquid velocity. A comparison with the empirical formula of Bowring [2] for water is given.
Calculation of Steam Volume Fraction in Subcooled Boiling
Authors: Zia Rouhani S.
Published: February 2012

An analysis of subcooled boiling is presented. It is assumed that heat is removed by vapor generation, heating of the liquid that replaces the detached bubbles, and to some extent by single-phase heat transfer. Two regions of subcooled boiling are considered and a criterion is provided for obtaining the limiting value of subcooling between the two regions. Condensation of vapor in the subcooled liquid is analyzed and the relative velocity of vapor with respect to the liquid is neglected in these regions. The theoretical arguments result in some equations for the calculation of steam volume fraction and true liquid subcooling.
Bubble Growth and Collapse in Liquid Nitrogen
Authors: Hewitt H. C. , Parker J. D.
Published: February 2012

Experimental data on bubble growth in superheated liquid nitrogen, bubble collapse in subcooled liquid nitrogen, and bubble growth with decreasing liquid nitrogen pressure are compared to the theoretical solutions obtained for noncryogens. Vapor bubbles in liquid nitrogen were found to behave quite similarly to vapor bubbles in noncryogens. This paper provides experimental data in two areas where additional theoretical work is needed: Bubble collapse in subcooled liquid, and bubble growth with decreasing pressure.
Heat Transfer to Sulfur Hexafluoride Near the Thermodynamic Critical Region in a Natural-Circulation Loop
Authors: Tanger G. E. , Lytle J. H. , Vachon R. I.
Published: February 2012

Heat transfer near the thermodynamic critical region to sulfur hexafluoride was investigated in two closed natural circulation loops. The vertical distance between the test section and the heat exchanger was the primary difference between two loop configurations. Local and average heat transfer coefficients along the test section were calculated from the experimental data. Test results were correlated by the equation. (Nu)(Grf)(Pr)=0.00982(Re)11/4 The range of variables included: System pressure, 535–896 psia, mean fluid bulk temperature, 111–193 deg F; specific volume, 0.016–0.043 cu ft/lbm; heat flux, 1900–9040 Btu/hr sq ft. The highest heat transfer coefficients were obtained at system pressures and mean fluid bulk temperatures slightly greater than the critical values with mean specific volumes in the loop slightly less than the critical specific volume of the system fluid. The heat transfer coefficients were increased by expanding the vertical distance between the test section and heat exchanger.
Heat Transfer by Free Convection From a Horizontal Wire to Carbon Dioxide in the Critical Region
Authors: Goldstein R. J. , Aung Win
Published: February 2012

The free-convection heat transfer from a 0.015-in-dia horizontal platinum wire to carbon dioxide in its critical region is experimentally investigated. The bulk fluid temperature and pressure are varied from 48 deg F to 136 deg F and 1000 psia to 1300 psia, respectively. Wire temperatures up to 1600 deg F are used. The results do not show the sharp rise in the heat flux curves that has been reported in a recent investigation. From the present measurements it appears that the usual free-convection correlation can be used even near the critical state, providing the properties are suitably evaluated.
Radiative Transfer in Anisotropically Scattering Media: Allowance for Fresnel Reflection at the Boundaries
Authors: Hottel H. C. , Sarofim A. F. , Evans L. B. , Vasalos I. A.
Published: February 2012

An analysis of the effect of Fresnel reflection at the interface of a slab containing isotropic or anisotropic scatterers is presented. A closed form solution for the effect of refractive index on the absorptance of an optically thin slab containing isotropic scatterers shows that allowance for internal reflection leads to absorptances severalfold those obtained with reflection ignored. Allowance for interface reflection also increases the computational effort to obtain solutions to the transport equation by the method of discrete ordinates. Representative numerical results are used to illustrate how interface reflection causes a significant decrease in the magnitude of both reflectance and transmittance, and a marked alteration in the angular distribution of the energy reflected and transmitted by a slab containing scattering centers.
The Effect of Liquid Solidification in a Tube Upon Laminar-Flow Heat Transfer and Pressure Drop
Authors: Zerkle R. D. , Sunderland J. E.
Published: February 2012

The effect of liquid solidification at the inner surface of a circular tube upon laminar-flow heat transfer and pressure drop is investigated. Steady-state conditions and a uniform wall temperature, which is lower than the liquid freezing temperature, are assumed. Theoretical solutions for heat transfer, radius of the liquid-solid interface, and pressure drop are determined assuming negligible free convection. Experimentation shows that free convection may produce considerable deviations between theoretical and observed results. A semiempirical method for obtaining approximate solutions is developed. A numerical example which demonstrates how free convection affects the solid-phase shell profile is presented.
Application of a Simplified Velocity Profile to the Prediction of Pipe-Flow Heat Transfer
Authors: Haberstroh R. D. , Baldwin L. V.
Published: February 2012

The temperature profiles and heat-transfer coefficients are predicted for fully developed turbulent pipe flow with constant wall heat flux for a wide range of Prandtl and Reynolds numbers. The basis for integrating the energy equation comes from a continuously differentiable velocity profile which fits the physical boundary conditions and is a rigorous (though not necessarily unique) solution of the Reynolds equations. This velocity profile is the semiempirical relation proposed by S. I. Pai, reference [12]. The assumptions are those of steady, incompressible, constant-property, fully developed, turbulent flow of Newtonian fluids in smooth, circular pipes with constant heat flux at the wall. The ratio of the turbulent thermal diffusivity to the turbulent momentum diffusivity is taken to be unity. The thermal quantities are obtained by numerical integration of the energy equation, and they are presented as curves and tables. A compact formula for the Nusselt number is given for a wide range of Reynolds and Prandtl numbers. The results degenerate identically to the case of laminar flow. The heat-transfer calculation requires neither adjustable factors nor data-fitting beyond the empirical constants in the momentum equation; thus this analysis constitutes a heat-transfer prediction to be tested against heat-transfer data.
A Study of Bubble Departure in Forced-Convection Boiling
Authors: Koumoutsos N. , Moissis R. , Spyridonos A.
Published: February 2012

Visual observations in a boiling liquid flow indicate that, as the flow velocity is increased, the size of bubbles leaving the heating surface decreases. The purpose of this investigation is to arrive at a criterion for bubble departure in forced-convection nucleate boiling. Photographic studies indicate that a little before departure a “neck” is formed joining the almost spherical bubble to the heating surface. From a consideration of the hydrodynamic stability of the bubble-and-neck model, the departure-size-to-velocity relationship may be predicted. Measured departure radii in a forced-convection boiling water system taken by means of high-speed photography are satisfactorily correlated with the results derived analytically.
Evaluation of Constants for the Rohsenow Pool-Boiling Correlation
Authors: Vachon R. I. , Nix G. H. , Tanger G. E.
Published: February 2012

The paper contains results of applying the Rohsenow pool-boiling correlation to data from the literature. Recent evidence supports the premise that the coefficient Csf and the exponent r of the Rohsenow equation vary with surface preparation technique as well as with liquid-surface combination. Eleven separate studies involving seven liquid-surface combinations and seven different surface preparation techniques have been correlated. Appropriate values of r and Csf have been determined using least squares techniques in conjunction with the Rohsenow equation to represent the various data investigated.
Heat Transfer for Laminar Flow in a Curved Pipe
Authors: O¨zisik M. N. , Topakog˘lu H. C.
Published: February 2012

Heat transfer for hydrodynamically and thermally fully developed laminar flow in a curved pipe is solved by a method of series expansion. The wall temperature around the periphery of any cross section, the mean heat flux along the pipe, and the internal heat generation are assumed to be uniform. The first few terms of the series expansion are determined and analytical expressions for the temperature distribution in the fluid and for the Nusselt number are presented; the results are applicable for small curvatures. A correlation with experiment is included.
High Temperature Thermal Conductivity of Rare Gases and Gas Mixtures
Authors: Matula Richard A.
Published: February 2012

The thermal conductivities of pure argon, pure xenon, and of three helium-argon mixtures have been determined in the temperature range 650–5000 deg K by measuring heat transfer rates from shock heated gases to the end wall of a shock tube. The heat transfer rate was measured by monitoring the time dependence of the voltage drop across a thin-film gage mounted in the end cap of the shock tube. During the course of the experiments, the pressure of the test gas behind the reflected shock wave ranged from approximately 1/3 to 2 atmospheres. In all cases, the temperature dependence (T) of the thermal conductivity (K) was assumed to follow a power law relationship of the form K/Kw = (T/Tw)b where Kw is the established value of the gas conductivity at the reference temperature (Tw) which was chosen near room temperature. The parameter b was evaluated by applying a least squares fit to the experimental data. Theoretical values of the conductivity of all of the gases studied were computed utilizing the Lennard-Jones (6–12) potential. In the case of the gas mixtures, an empirical combining rule was used to relate the force constants between unlike atoms to the known constants between like atoms. The experimental and theoretical results for the pure gases are in good agreement. The experimental and theoretical values of the mixture conductivities are within 10–20 percent, and as expected the theoretical predictions are least accurate for equimolar mixtures.
A Modification to the Monte Carlo Method—The Exodus Method
Authors: Emery A. F. , Carson W. W.
Published: February 2012

A modification to the Monte Carlo method is described which reduces calculation time and improves the accuracy. This method—termed “Exodus”—is not dependent upon a random number generator and may be applied to any problem which admits of a nodal network.
Heat and Mass Transfer Mechanisms in Sublimation Dehydration
Authors: Dyer D. F. , Sunderland J. E.
Published: February 2012

An analytical study is presented for sublimation dehydration which shows the effect of the important mechanisms involved in the process. The effects of the presence of a binary gas mixture are considered. The boundary conditions for this solution are all directly controllable external conditions; namely, the temperature, total pressure, water-vapor partial pressure at the heated surface, and the temperature of the face opposite to the heated surface. The analysis involves the simultaneous solution of the appropriate equations of continuity, momentum, and energy, as well as the equation of state for each of the gas components present. Typical results are given for freeze-drying of bovine muscle. The drying rate is seen to increase with decreasing total pressure and water-vapor concentration. The relative importance of diffusional transport compared with bulk transport is presented. It is shown that drying rates can be substantially increased by judiciously making use of heat transfer through the frozen region.
Laminar Flow Heat Transfer and Fluid Flow for Liquids With Temperature-Dependent Viscosity
Authors: Test F. L.
Published: February 2012

An analytical and experimental study is made of liquids with a temperature dependent viscosity. The analytical approach is a numerical solution of the momentum, continuity, and energy equations. The significance of various terms in the equations is considered. The experimental approach involves the use of hot wire techniques for the determination of velocity profiles. Correlations are obtained for the Nusselt number and friction factor.
Dispersed Flow Film Boiling
Authors: Forslund R. P. , Rohsenow W. M.
Published: February 2012

New data for dispersed flow film boiling of nitrogen are presented for the following conditions: tube diameter 0.228, 0.323, and 0.462 in. ID; length 4 and 8 ft; mass velocity 70,000 to 19,000 lb/hr ft2; heat flux 0 to 2500 Btu/hr ft2; inlet condition near saturation; exit quality 35 to 315 percent. The previously presented analysis [12] is improved by accounting for droplet breakup due to vapor acceleration, modified drag coefficient on accelerating droplets, and a “Leidenfrost” heat transfer from the wall to the droplets at lower qualities. Measurements are also made to verify the existence of the substantial amount of vapor superheat in the presence of liquid droplets, as predicted by the analysis.
A Study of Directional Radiation Properties of Specially Prepared V-Groove Cavities
Authors: Black W. Z. , Schoenhals R. J.
Published: February 2012

Emission and absorption characteristics of a V-groove cavity are analyzed and the predicted results are compared with experimental measurements. The configuration considered consists of a flat black base with diffusely emitting, specularly reflecting side surfaces. The local directional emissivity is given as a function of emission angle, position, side wall emissivity, and cavity geometry. The results show that, with proper selection of the parameters, the cavity can be made a strong emitter and absorber for directions which are nearly normal to the cavity opening area, and a weak emitter and absorber for directions which correspond to large angles measured from the normal. A simple expression for cavity depth is suggested for closely approaching the optimum condition of maximum directionality of the cavity. Some predicted heat transfer rates for surfaces composed of many cavities are also presented. These results illustrate the potential value of employing specially prepared grooved surfaces in applications where control of radiant energy exchange is required.
An Experimental Examination of the Validity of the Commonly Used Methods of Radiant Heat Transfer Analysis
Authors: Schornhorst J. R. , Viskanta R.
Published: February 2012

In this work the validity and accuracy of the commonly used methods of radiant heat transfer prediction were checked experimentally. The local irradiation was measured for five different materials in two simple configurations. The materials tested were sand-blasted stainless steel, electropolished stainless steel, rough electroplated gold, smooth electroplated gold, and PV100 white paint. Measurements were made over the temperature range from 50 deg F to 850 deg F for each of four sets of geometric parameters. The predicted values of local incident fluxes using the diffuse, specular, and diffuse-specular models were compared with experimental data. The data agree with the diffuse model within the accuracy of the measurements for all the surfaces tested. Additional conclusions, recommendations, and procedures, which should be followed for more realistic radiant heat transfer calculations, are given in the body of the paper.
Joulean Heating of an Infinite Rectangular Rod With Orthotropic Thermal Properties
Authors: Cooper H. F.
Published: February 2012

The formal solution previously obtained for the transient thermal response of an infinite rectangular rod, with orthotropic thermal conductivity and linear boundary conditions, to Joulean heating under a constant current condition is extended to include the constant voltage case under certain restrictive conditions. The solution is a rapidly converging doubly infinite series whose leading term is an accurate approximation for the thermal response. Graphical aids are presented which allow the designer of such apparatus as solenoids and various coils to quickly obtain estimates of the temperature distribution, the heat flow from the boundaries, the thermal time constant, and the location of the peak temperature. It is found that in certain cases the theory for constant current case predicts no steady-state condition. This condition is unrealistic because it requires an infinite voltage to provide the constant current. The theory predicts that the constant voltage case is always bounded.
Effect of Buoyancy on the Melting and Freezing Process
Authors: Boger D. V. , Westwater J. W.
Published: February 2012

Measurements were made of interfacial velocities and transient and steady-state temperature profiles during the freezing and melting of water in a 0.5 × 0.5 × 2-in. high test chamber. Heat flow was one-dimensional, up and down. Tests both included and excluded the density-inversion temperature of 4 deg C. Freezing at the top and at the bottom, melting at the top, and at the bottom, all were achieved by selection of cold-end temperatures between −50 and −50 deg C and hot-end temperatures between 3 and 97 deg C. Runs included conditions with buoyancy forces in the liquid, with buoyancy forces existing but insufficient to cause convection, and with natural convection occurring at all times. With no natural convection the results agreed with predictions found by use of the numerical technique of Murray and Landis developed originally for cases with no convection. The onset of natural convection was found to be at a Rayleigh number of about 1700. Proper selection of the significant length, the ΔT, and the coefficient of expansion for the Rayleigh number is described. The effective thermal conductivity for Rayleigh numbers up to 107 agreed with prior correlations obtained with free convection but with no phase change. The numerical calculation procedure was modified successfully by use of the effective k. At the highest Rayleigh number, an unusual case of oscillations in the interface velocity is reported.
The Solution of Heat Conduction Problems by Probability Methods
Authors: Haji-Sheikh A. , Sparrow E. M.
Published: February 2012

Fundamental concepts pertaining to the solution of heat conduction problems by probability methods (Monte Carlo methods) are devised and techniques of application are developed. It is demonstrated that probability methods can be applied over the entire range of heat conduction problems. These include both steady state and transient situations in bodies of arbitrary shape with arbitrary boundary conditions (including derivative conditions) and with volume heat sources. Problems involving nonlinear boundary conditions (e.g., combined convection and radiation) and moving boundaries (change of phase) are also accommodated by probability methods. All of these various situations are treated in the paper. Numerous computational experiments are carried out, many of which provide results for physical problems not heretofore solved in the literature. A new concept, the floating random walk, is introduced and this provides the flexibility needed to accommodate such a wide range of problems.
Secondary Flows Associated With Slowly Oscillating and Rotating Disks
Authors: Hanold R. J. , Moszynski J. R.
Published: February 2012

This investigation concerns the application of a flow visualization technique to obtain a quantitative and qualitative description of the secondary flow associated with a slowly oscillating disk. Included in the description is a systematic study of the flow behavior as a function of the Reynolds number. The three-dimensional character of the flow is verified and the development of a toroidal vortex both above and below the oscillating disk is illustrated. The experiments are performed in a vessel similar in design to a typical oscillating body viscometer. The effect of the Reynolds number on the damping rate of the disk is investigated. The influence of natural convective flows on the magnitude and reproducibility of the damping rate is obtained. The development of a secondary flow in the form of a toroidal vortex for both the rotating disk and rotating sphere is also illustrated.
The Effect of Mass Injection on Heat Transfer from a Partially Dissociated Gas Stream
Authors: Meroney R. N. , Giedt W. H.
Published: February 2012

An investigation of the effect of hydrogen and helium injection on local heat transfer to a porous surface from an oxygen-acetylene combustion gas stream is described. The free-stream temperature varied from 6200 to 5200 deg Rankine and the volumetric percentage of atomic hydrogen from 20 to 8. Flow in the boundary layer was found to be turbulent. Study of the results led to successful correlation of the ratio of the heat flux with injection to the heat flux without injection in terms of a dimensionless blowing parameter in which properties are evaluated at an average reference state. A method for predicting heat flux with injection was then developed. This is based on a temperature rather than an enthalpy potential because the latter resulted in anomalous values for the Stanton number under some of the test conditions.
A Heat-Transfer Analysis of the Solidification of a Binary Eutectic System
Authors: Tien R. H. , Geiger G. E.
Published: February 2012

The solidification of a binary system differs from a pure metal in that the latent heat effect no longer occurs at the melting point but rather in a freezing zone between the liquidus and solidus temperatures. Such solidification is analyzed from a heat-transfer point of view. The system considered occupies a semi-infinite region, is initially at the liquidus temperature, and at all subsequent times the surface temperature is considered constant; the fraction solid is assumed to be linear with distance within the freezing zone between the solidus and liquidus. The heat released during solidification is treated as a discontinuous heat generation. This corresponds to the nonequilibrium freezing of a eutectic system. The temperature distribution and thickness of each region are calculated as a function of time using the error function solution and the heat-balance integral; the results are given in graphical form.
Boiling Heat-Transfer Data at Low Heat Flux
Authors: Elrod W. C. , Clark J. A. , Lady E. R. , Merte H.
Published: February 2012

Data are presented for natural and forced convection heat transfer from the outside of a single 3/4-in-dia tube to saturated water in the pressure range from 535 to 1550 psia. Nonboiling and nucleate boiling at low heat flux are considered for vertical and horizontal tubes. Water chemistry control is shown to be important in obtaining reproducible data. A new factor, suspended solid material in the boiling medium, is found to influence the nucleate boiling data in a manner similar to that of a dissolved gas.
Free Convection From a Vertical Flat Plate With Step Discontinuities in Surface Temperature
Authors: Hayday A. A. , Bowlus D. A. , McGraw R. A.
Published: February 2012

The paper explores a numerical method for the solution of strongly coupled equations governing nonsimilar flows in laminar boundary layers. The analysis deals specifically with nonsimilar free convection from a vertical plate suspended in air, the nonsimilarity of the flow being generated by step discontinuities in surface temperatures. Results presented herein compare favorably with and form a theoretical basis for the experiments of Schetz and Eichhorn.
The Interaction of Thermal Radiation in Optically Thick Boundary Layers
Authors: Novotny J. L. , Yang Kwang-Tzu
Published: February 2012

An analysis is presented to examine the role of the Rosseland or optically thick approximation in convection-radiation interaction situations. The analysis is formulated for the flow of a gray gas in a laminar two-dimensional boundary layer under the restriction of small temperature differences within the flow field. The boundary-layer energy equation is treated using the method of matched asymptotic expansions based on a parameter which characterizes the optical thickness of the gas. Two illustrative examples of the resulting equations are presented.
Heat Transfer in Turbulent Boundary-Layer Separation Over a Surface Cavity
Authors: Haugen R. L. , Dhanak A. M.
Published: February 2012

An experimental and analytical study is presented in this paper describing heat transfer in the region of separated flow over a two-dimensional rectangular cavity (of variable depth-width ratios) facing an oncoming turbulent boundary layer of variable thickness. The analysis, based on a prescription of eddy diffusion in the mixing region, predicts a heat transfer correlation, in terms of the foregoing variables, resulting in good agreement with the data. Experiments were performed with conditions of uniform temperature and uniform heat flux at the cavity walls and revealed no substantial difference between the two methods on the final correlation.
Effect of Uncooled Inlet Length and Nozzle Convergence Angle on the Turbulent Boundary Layer and Heat Transfer in Conical Nozzles Operating With Air
Authors: Boldman D. R. , Schmidt J. F. , Ehlers R. C.
Published: February 2012

Nozzle boundary layer and heat transfer measurements are presented for nozzles having half angles of convergence of 30 and 60 deg, each operating in conjunction with a short and long uncooled pipe inlet. The long inlet, which produced a fully developed turbulent boundary layer at the nozzle entrance, did not significantly alter the nozzle heat transfer distribution relative to values obtained with the short pipe inlet. Peak heat transfer coefficients for the high convergence nozzle were nearly 40 percent higher than the peak value for the 30 deg half angle of convergence nozzle. Measured heat transfer coefficients were compared to predictions based on a boundary layer theory and a pipe flow type correlation.
Transient Heat Transfer for Turbulent Flow Over a Flat Plate of Appreciable Thermal Capacity and Containing Time-Dependent Heat Source
Authors: Soliman M. , Johnson H. A.
Published: February 2012

An approximate analysis and experimental data are presented for the transient mean wall temperature of a flat plate of appreciable thermal capacity, heated by a step in the heat generation rate and cooled on both sides by a steady, incompressible turbulent flow with a Prandtl number of unity. Theory and experiments are in agreement over a range of Reynolds numbers 5 × 105 ≤ ReL ≤ 2 × 106. The experimental mean heat transfer coefficient is observed to go through a dip to a minimum before reaching the steady state. This dip is found to be due to the conjunction of a large wall thermal capacity and a sufficiently high flow velocity.
The Influence of Free Stream Turbulence on the Local Heat Transfer From Cylinders
Authors: Seban R. A.
Published: February 2012

Local heat-transfer coefficients and recovery factors are presented for three different cylinders in a two-dimensional subsonic air flow, with emphasis on the effect of screen-produced turbulence on these quantities. The increase in turbulent intensity so realized produced larger local heat-transfer coefficients, in a way dependent upon the location on the cylinders, through a direct increase in the heat transfer to the laminar boundary layer, through an earlier transition to turbulence, or through an alteration in the character of the separated flow. Alternatively, recovery factors were affected less, being invariant with respect to the turbulent intensity for attached boundary layer flow, but demonstrating large changes in those separated flow regions for which increased free stream turbulence produced substantial changes in the nature of the separated flow.
Steam Slip—Theoretical Prediction From Momentum Model
Authors: Levy S.
Published: February 2012

Theoretical equations governing slip effects in forced circulation of boiling water are derived. The equations indicate that steam slip is dependent upon channel geometry, inlet water velocity, and rate of heat addition. A simplified momentum model is postulated which leads to equal friction and head losses of two phases. The model gives good agreement with available experimental results in horizontal and vertical test sections with and without heat addition at pressures from 12 to 2000 psia. Discussion of the model in terms of nonquasi steady-state unbalances of friction and head losses of the two phases explains experimental deviations from the predictions and the previously noted effects of water inlet velocity. It also gives trends for the effects of channel geometry and rate of heat addition. Application of the simplified model to calculating two-phase pressure drops is included.
Pressure Drop and Heat Transfer in a Duct With Triangular Cross Section
Authors: Eckert E. R. G. , Irvine T. F.
Published: February 2012

Friction factors have been measured for a duct whose cross section has the shape of an isosceles triangle with a side ratio 5 to 1 in the fully developed flow region for laminar, transitional, and turbulent conditions. In addition, local and average heat-transfer coefficients and the temperature field in the duct wall have been determined for the condition of constant heat generation per unit volume of the duct walls. Friction factors in laminar flow agreed well with analytical predictions. In the turbulent flow range they were by 20 per cent lower than values calculated from relations for a round tube with the use of the “hydraulic diameter.” Heat-transfer coefficients averaged over the circumference of the duct were only half as large as values calculated from round tube relations in the Reynolds number range from 4300 to 24,000. The measurements also revealed that thermal starting lengths were in excess of 100 diameters. In round tubes a length of 10 to 20 diameters has been found sufficient to develop the temperature field.
Combined Free and Forced-Convection Heat-Generating Laminar Flow Inside Vertical Pipes With Circular Sector Cross Sections
Authors: Lu Pau-Chang
Published: February 2012

Combined free and forced-convection, heat-generating laminar flow inside cylindrical pipes with elements parallel to the direction of the generating body force is solved by applying the finite Fourier sine transform and finite Hankel transforms when the cross sections of the pipes are circular sectors. A numerical example is provided to show the effects of various parameters.
The Role of the Skin in Heat Transfer
Authors: Stoll A. M.
Published: February 2012

The author considers lines of fundamental research and the impact of human factors in the area of thermal exchange. Logically, this area of investigation may be divided into: (a) Heat exchange between man and his environment; and (b) internal energy balance between heat production and heat loss. Very little information has been compiled in an orderly fashion concerning the skin through which heat must flow in both directions to maintain man in his environment in a functional capacity. It is therefore the purpose of this paper to consider the human skin, its dimensions and properties with respect to its role in heat transfer, and the effects of its impairment or injury.
The Prediction of Human Thermal Tolerance When Using a Ventilating Garment With an Antiexposure Suit
Authors: Mc Cutchan J. W.
Published: February 2012

The physiological responses of human subjects have been investigated in the thermal environments ranging from 120 to 240 deg F while wearing the MA-2 ventilating garment, an MK-IV exposure suit, and other garments comprising 2.15 clo2 of thermal resistance. The ventilating garment was given air inputs ranging from 2 to 14 cfm in volume, and from 50 to 90 F in temperature. The thermal responses of the subjects are shown graphically in terms of heat storage, heart rates, sweat rates, and composite indexes of these variables. The results of these experiments have been prepared in terms of an equation which is presented graphically as a nomograph. This nomograph predicts the cooling power of the MA-2 ventilating garment and is to be used in conjunction with the tolerance chart. The tolerance data, which were determined on steady exposures in a preheated chamber, are used to predict human tolerance for conditions where the air and wall temperatures are not constant.
The Effect of Mass Transfer on Free Convection
Authors: Eichhorn R.
Published: February 2012

Consideration is given to the constant property laminar boundary layer equations with free convection and mass transfer. It is shown that similar solutions are possible for blowing rate distributions varying as the distance from the leading edge raised to the power (n − 1)/4 where n is the exponent in a power law surface temperature distribution. Solutions to the equations in the form of skin friction and heat-transfer parameters, and velocity and temperature profiles are presented for the constant wall temperature case for a fluid with Pr = 0.73. The cases considered range from strong suction to strong blowing. Mass transfer has a pronounced effect on the heat transfer but only a slight effect on the skin friction. In light of the solutions presented, these effects are shown to be physically rational.
Mass Transfer, Flow, and Heat Transfer About a Rotating Disk
Authors: Sparrow E. M. , Gregg J. L.
Published: February 2012

The effects of mass injection or removal at the surface of a rotating disk on heat transfer and on the flow field about the disk are studied. Consideration is given to gaseous systems which are composed of either one or two component gases. Solutions of the equations which govern the hydrodynamics, energy transfer, and mass diffusion have been obtained over the entire range from large suction velocities to large blowing velocities. Results are given for the velocity, temperature, and mass-fraction distributions, as well as for the heat-transfer, mass-transfer, and torque requirements. The effects of the mass transfer are discussed in detail. It is shown that fluid injection sharply decreases the heat transfer at the surface.
Thermal Radiation From a Cylindrical Enclosure With Specified Wall Heat Flux
Authors: Usiskin C. M. , Siegel R.
Published: February 2012

Thermal radiation is considered from the inside surface of a heated cylindrical enclosure. A specified heat input is imposed at the enclosure wall and the surface temperature distribution is determined. The analysis considers both black and diffuse gray-body radiation and obtains a simple relation between the two. The energy equation, which is a linear integral equation, is solved by three methods: (a) Use of a separable kernel; (b) numerical integration; and (c) variational methods.
Optimization of a Sandwiched Thermoelectric Device
Authors: Swanson B. W. , Somers E. V. , Heikes R. R.
Published: February 2012

An analysis is made for optimizing the thermal efficiency of a sandwiched thermoelectric device and is coded for a digital computer. For suitable input data, the computer determines the thermocouple design that approximately maximizes the thermal efficiency of the device. A verification of the analysis indicates that the difference between the approximately optimum efficiency and the optimum efficiency is negligible.
Thermal Conductivity and Prandtl Number of Carbon Dioxide and Carbon-Dioxide Air Mixtures at One Atmosphere
Authors: Novotny Jerome L. , Irvine Thomas F.
Published: February 2012

By measuring laminar recovery factors in a high velocity gas stream, experimental determinations were made of the Prandtl number of carbon dioxide over a temperature range from 285 to 450 K and of carbon-dioxide air mixtures at an average temperature of 285 K with a predicted maximum error of 1.5 per cent. Thermal conductivity values were deduced from these Prandtl numbers and compared with literature values measured by other methods. Using intermolecular force constants determined from literature experimental data, viscosities, thermal conductivities, and Prandtl numbers were calculated for carbon-dioxide air mixtures over the temperature range 200 to 1500 deg for mixture ratios from pure air to pure carbon dioxide.
Forced Convection Heat Transfer From an Isothermal Sphere to Water
Authors: Vliet G. C. , Leppert G.
Published: February 2012

Heat transfer from a spherical heating element by forced convection occurs in many situations of practical importance. While the present investigation stems from interest in spherical fuel elements for liquid-cooled nuclear reactors, similar heat-transfer conditions may prevail in chemical process reactors and in other engineering applications. Previously reported measurements of convective heat-transfer coefficients from spheres to liquids have been limited to low Reynolds numbers and to negligibly small temperature differences. This paper correlates these earlier data with new measurements taken at much higher Reynolds numbers and with substantial temperature difference between the heating surface and the liquid. The significance of the larger temperature difference is twofold: Since the viscosity variation of liquids with temperature is usually strong, there may be an important viscosity change across the boundary layer. Furthermore, natural convection effects may not be ignored in regions of large temperature difference and low or moderate Reynolds number. Both of these effects are discussed in the paper.
Heat Transfer and Pressure Drop in an Annular Gap With Surface Spoilers
Authors: Kemeny G. A. , Cyphers J. A.
Published: February 2012

Heat-transfer and pressure drop data are presented for turbulent water flow in the annular space between concentric tubes. Heat was transferred to the liquid from the inner surface which was equipped with various surface spoiler configurations. A common outer tube was used which was maintained smooth and adiabatic for all tests. An empirical formula is given which correlates friction factors for circular tubes and annular gaps, or narrow flat passages, with semicircular spoilers on either one or both sides. The use of such friction factors in the Martinelli equation for turbulent heat transfer gives satisfactory estimates of the heat transfer for spoiler configurations.
Radiation Heat Transfer in a Spherical Enclosure Containing a Participating, Heat-Generating Gas
Authors: Sparrow E. M. , Usiskin C. M. , Hubbard H. A.
Published: February 2012

An analysis is made of the thermal radiation in an absorbing-emitting nonisothermal gas confined in a hollow spherical enclosure or in the space between two concentric spheres. The gas is gray and contains a volume heat source, while the bounding walls are black and isothermal. The conservation of energy principle yields an integral equation which has been solved for a wide range of geometric and radiative conditions. It is found that as the absorption coefficient increases in a fixed geometry, the gas temperature decreases and becomes more nonuniform. On the other hand, as the enclosure size increases, the gas temperature increases and becomes more nonuniform. An approximate analysis using a conduction-type transfer law has been carried out, and the results are compared with the integral equation solutions.
Pool Boiling in an Accelerating System
Authors: Merte Herman , Clark J. A.
Published: February 2012

A study is reported of the influence of system acceleration (1 to 21 g) on pool boiling heat transfer using distilled water at approximately atmospheric pressure. The acceleration of the system is such that the resulting force field is normal to the heating surface, thereby increasing the buoyant forces acting on the vapor bubbles. Heat-flux rate is varied from approximately 5000 Btu/hr-sq ft (nonboiling) to 100,000 Btu/hr-sq ft. Data are presented for the influence of subcooling with the boiling system under acceleration at the lower values of heat flux. A preliminary analysis is presented for a theoretical description of the process of boiling under the influence of high acceleration, including the simultaneous effect of natural convection.
An Experimental Study of Boiling in Reduced and Zero Gravity Fields
Authors: Usiskin C. M. , Siegel R.
Published: February 2012

A pool boiling apparatus was mounted on a counterweighted platform which could be dropped a distance of nine feet. By varying the size of the counterweight, the effective gravity field on the equipment was adjusted between zero and unity. A study of boiling burnout in water indicated that a variation in the critical heat flux according to the one quarter power of gravity was reasonable. A consideration of the transient burnout process was necessary in order to properly interpret the data. A photographic study of nucleate boiling showed how the velocity of freely rising vapor bubbles decreased as gravity was reduced. The bubble diameters at the time of breakoff from the heated surface were found to vary inversely as gravity to the 1/3.5 power. Motion pictures were taken to illustrate both nucleate and film boiling in the low gravity range.
Film Cooling With Multiple Slots and Louvers
Authors: Chin J. H. , Skirvin S. C. , Hayes L. E. , Burggraf F.
Published: February 2012

Experimental results are presented for film cooling of an adiabatic plate downstream of one to ten slots (Part 1) and two to twenty rows of discrete punched louvers (Part 2) in a subsonic turbulent flow under zero pressure gradient. The adiabatic wall temperatures downstreams of the last equivalent slot were measured and correlated in terms of the flow parameters, equivalent slot number and slot spacing, and distances downstreams of the last equivalent slot.
Dynamic Response of Heat Exchangers Having Internal Heat Sources—Part IV
Authors: Yang W. J. , Clark J. A. , Arpaci V. S.
Published: February 2012

This paper investigates the dynamic response of a heat exchanger having a sinusoidally time-dependent rate of internal heat generation. Results for both the transient-periodic and the steady-periodic, or frequency response, are given. These results include the response of the wall and fluid temperatures and the wall-fluid temperature difference. A phenomena of resonance in the amplitude ratio and phase shift is disclosed. Analytical results are obtained through the use of the Laplace transform technique. Experimental results are presented which compare favorably with the theoretical analysis. Heat exchangers to which these results apply include the heterogeneous nuclear reactor.
An Integral Treatment of Two-Phase Boundary Layer in Film Condensation
Authors: Koh J. C. Y.
Published: February 2012

By using the integral method, the task of solving the complicated two-phase boundary-layer differential equations in laminar-film condensation has been reduced to the simple work of solving an algebraic equation. It was shown analytically that the parameter [(ρμ)L/(ρμ)v]1/2 can be removed from the film-condensation problem and hence only two parameters, cpΔT/hfg and Pr, are involved. The calculated results in heat transfer and condensate flow rates agree very well with the results from the exact solution of the boundary-layer equations. With [(ρμ)v/(ρμ)L]1/2 remaining as a parameter, it is believed that the present method can be used to solve the analogous two-phase boundary-layer problem in laminar film boiling.
Temperature Distribution in a Slab Moving From a Chamber at One Temperature to a Chamber at Another Temperature
Authors: Horvay G.
Published: February 2012

When an infinitely long slab travels from a chamber at one temperature to a chamber isolated from the first, at a higher temperature, heat will leak out along the slab from the second chamber to the first, whose amount decreases as the speed of the slab increases. An estimate of the heat lost is of interest in hot-rolling, in some nuclear processes, and in some continuous casting processes. The problem of determining the temperature distribution and the heat flow in the two chambers is formulated in the form of dual integral equations, and the solution is obtained by the method of Wiener-Hopf.
Thermal Conductivity of Some Commercial Iron-Nickel Alloys
Authors: Watson T. W. , Robinson H. E.
Published: February 2012

Results of laboratory determinations of thermal conductivities in the temperature range −150 to 540 deg C are presented for 12 iron-nickel alloys. Six samples are of low nickel content, in the range from 1 to 9 per cent, and six others have nickel contents in the range from 35 to 80 per cent. A sample of AISI 1015 steel is included for comparative purposes. The determinations were made on bar specimens about 2.54 cm in diameter and 37 cm long, by an absolute steady-state method with heat flowing longitudinally in the bar. Computation of results from observed data was effected by means of a digital computer.
Heat Transfer to Longitudinal Laminar Flow Between Cylinders
Authors: Sparrow E. M. , Loeffler A. L. , Hubbard H. A.
Published: February 2012

Consideration is given to the fully developed heat-transfer characteristics for longitudinal laminar flow between cylinders arranged in an equilateral triangular array. The analysis is carried out for the condition of uniform heat transfer per unit length. Solutions are obtained for the temperature distribution, and from these, Nusselt numbers are derived for a wide range of spacing-to-diameter ratios. It is found that as the spacing ratio increases, so also does the wall-to-bulk temperature difference for a fixed heat transfer per unit length. Corresponding to a uniform surface temperature around the circumference of a cylinder, the circumferential variation of the local heat flux is computed. For spacing ratios of 1.5 ∼ 2.0 and greater, uniform peripheral wall temperature and uniform peripheral heat flux are simultaneously achieved. A simplified analysis which neglects circumferential variations is also carried out, and the results are compared with those from the more exact formulation.