bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Specularly Reflecting Gray Surface on Thermal Radiation Through a Tube and From Its Heated Wall
Authors: Perlmutter M. , Siegel R.
Published: February 2012

An analysis was made of specular radiation exchange within a circular tube open at both ends and in vacuum. The tube is exposed to thermal radiation from an environment at each end and can have a uniform heat flux supplied at its wall. The external surface of the tube wall is insulated, while the internal surface is a gray, specular (mirrorlike) reflector for thermal radiation. The integral equations governing the radiation exchange are solved to determine the internal surface temperature and the amount of heat transmitted through the tube from the environment at one end to the other. Specular reflections were found to reduce the maximum surface temperature of the heated wall as compared with diffuse reflections, and in some instances the maximum temperature was below the value for a black surface. The energy transmitted through the tube was larger for the specularly reflecting wall than for diffuse reflections. It was also shown that the energy transmitted for a diffusely reflecting gray wall is the same as for a black wall.
Configuration Factors for Radiant Heat-Transfer Calculations Involving People
Authors: Dunkle R. V.
Published: February 2012

Results of point form factor measurements on people are correlated by simple equations for standing and sitting subjects. The point values are integrated to obtain area configuration factors and the results are presented in graphical form for the standing man. Equations for the area configuration factors are given for the seated man. Comparisons are made with other published data.
Surface Recombination and Heat Transfer in a Dissociated Diatomic Gas—Part 1
Authors: Cottingham W. B. , Grosh R. J.
Published: February 2012

In Part 1 of this two-part paper, a method is described for the investigation of surface catalytic effects and heat transfer in a dissociated diatomic gas. Description is given of the experimental apparatus and the method and theory of testing. Part 2 shows the results obtained by using the equipment with hydrogen gas. A comparison of these results with theory is given and some conclusions are drawn about the recombination of atoms on surfaces.
The Effect of a Magnetic Field Upon the Free Convection of a Conducting Fluid
Authors: Emery Ashley F.
Published: February 2012

The heat transferred by free convection through vertical plane layers of water and mercury was measured as a function of the temperature difference across the layer, the height of the layer, and its thickness. Subsequently, the reduction in the heat transferred through the mercury due to the application of transverse magnetic fields was measured and correlated by the parameter (magnetic field intensity squared)/(square root of the layer temperature difference). The form of this correlation was determined by an analysis based upon the assumption that the flow within the layer resembled two boundary layers, one rising on the hot side and the other falling on the cold side, with crossflow at the top and bottom of the layer.
A Contribution to the Solution of Transient Heat-Transfer Problems by Means of Electric Analogy
Authors: Svoboda O. , Tu˚ma J.
Published: February 2012

A description and theoretical basis of a new method for solving of transient temperature fields by means of an electric analogy is introduced. This method substitutes the usual input function by a continuous spectrum of harmonic oscillations. Thus it is possible to solve some special problems with minimal equipment requirements.
A New and Simpler Formulation for Radiative Angle Factors
Authors: Sparrow E. M.
Published: February 2012

A new representation for diffuse angle factors has been derived which replaces the usual area integrals by more tractable contour (i.e., line) integrals. The new formulation generally simplifies analytical calculation of angle factors. The advantages of the new representation are associated with the reduced order of the integrals (i.e., double reduced to single, quadruple reduced to double) which must be evaluated to calculate the angle factor. An additional benefit of the new representation is that integrals of simpler form are encountered than in the present representation. For the numerical evaluation of angle factors, the reduction in the order of the integrals should have great practical utility. In the case of energy exchange between an infinitesimal element and a finite area, a superposition theorem has been derived which permits results for certain basic surfaces to be linearly combined to yield angle factors for surfaces at other orientations. Several illustrations of the application of the new formulation are presented.
Some Possible Critical Conditions in Nucleate Boiling
Authors: Chang Yan-Po
Published: February 2012

The primary purpose of this paper is to introduce into boiling heat transfer certain basic ideas from which several critical conditions are derived. The heat transfer in nucleate boiling is considered as being limited by the maximum rate of bubble generation from a unit area of the heating surface. With certain simplified assumptions, an equation is obtained for the first critical heat flux of nucleate boiling with and without forced convection and subcooling.
Heat Transfer to Plane Turbulent Wall Jets
Authors: Myers G. E. , Schauer J. J. , Eustis R. H.
Published: February 2012

The heat-transfer characteristics of two-dimensional, incompressible, turbulent wall jets are discussed. An analytical prediction is made for the local Stanton number and data are presented for a step wall temperature distribution. The method for extending these data to arbitrary heating conditions is shown. Temperature surveys in the wall jet boundary layer are also presented.
Investigations of Heat-Transfer Coefficients for Air Flow Through Round Jets Impinging Normal to a Heat-Transfer Surface
Authors: Huang G. C.
Published: February 2012

In this paper, empirical equations of local as well as average heat-transfer coefficients of single jet system were derived. Two aspects of multiple jet systems have been studied. One concerns mainly the uniform distribution of heat-transfer coefficients and economy of power consumption. The other concerns the high magnitude of heat-transfer coefficients and the interference among jets. The experiments were conducted at Reynolds number from 103 to 104 and hole size from 1/8 to 1/4 in. diameter. An attempt was made to correlate empirical data to render practical application possible.
Natural Convection Flows in Parallel-Channel Systems
Authors: Chato J. C.
Published: February 2012

An analysis was developed for natural circulation flows in vertical multiple-channel systems with nonuniform heat inputs. A three-channel configuration was investigated in detail both analytically and experimentally. The results showed the existence of a metastable regime in which two metastable flow patterns could occur for a given set of heat input rates. A third predicted flow pattern in this regime was shown to be unstable and, therefore, nonexistent in practice.
Monte Carlo Solution of Thermal Transfer Through Radiant Media Between Gray Walls
Authors: Howell J. R. , Perlmutter M.
Published: February 2012

The Monte Carlo method is applied to the problem of radiant heat transfer to a nonisothermal absorbing and emitting gray gas between gray walls. The solutions are compared to limiting cases of black walls and large optical thickness available in the literature. The Monte Carlo procedure was found to be simply and quickly formulated for complex cases which cannot be readily attacked by standard analytical techniques. The numerical results were quickly obtained with the use of a high speed electronic computer. This method also gives greater physical insight into the behavior of the system.
Friction and Forced Convection Heat-Transfer Characteristics in Tubes With Twisted Tape Swirl Generators
Authors: Smithberg E. , Landis F.
Published: February 2012

Velocity distributions, friction losses, and heat-transfer characteristics were studied analytically and experimentally for fully developed turbulent flow in tubes with twisted tape swirl generators. Data were obtained for pitch-to-diameter ratios from 3.62 to 22.0 with both air and water under isothermal and forced convection heating conditions. The following principal conclusions result: (a) The velocity field is helicoidal and corresponds to a forced vortex in the core superposed on an essentially uniform axial flow. (b) Friction losses may be predicted from the combined effects of the axial and tangential boundary-layer flows coupled with an additional “vortex-mixing” effect. (c) Approximate heat-transfer correlations can be predicted from a Colburn-type analysis. These may be improved by considering a boundary layer and vortex mixing model.
Transient Heat Transfer in a Vapor-Heated Heat Exchanger With Arbitrary Timewise-Variant Flow Perturbation
Authors: Yang Wen-Jei
Published: February 2012

An analysis is made of transient heat transfer in a vapor-heated heat exchanger with an arbitrary timewise-variant flow perturbation. The heat-transfer coefficient between the tube and coolant is assumed to vary like the n power of the coolant velocity. Results are obtained through the use of the perturbation technique. General relations are presented in closed form and their application is illustrated by carrying out some typical examples: step, linear, exponential, and sinusoidal transients in the coolant flow velocity. The influence of the system parameters on the variation of the coolant temperature is investigated. A phenomenon of resonance in the amplitude-ratio and phase-shift is disclosed for the oscillating flow transient. This phenomenon is explained by analyzing the enthalpy change of the coolant particle in the heat exchanger. The results are also compared with the analyses that have assumed a constant heat-transfer coefficient. Heat exchangers to which these results apply include the double-pipe and shell- and-tube type heat exchangers.
Radiant Transfer Through a Gray Gas Between Concentric Cylinders Using Monte Carlo
Authors: Perlmutter M. , Howell J. R.
Published: February 2012

Solutions are obtained for the radiation heat transfer and emissive power distribution between infinitely long concentric gray cylinders at different wall temperatures and emissivities enclosing a gray nonisothermal gas with a uniformly distributed heat source. Solutions for black surfaces are obtained by the Monte Carlo method. These solutions are generalized by means of derived transformation equations relating the gray surface and black surface cases. Comparison of these results is made to the diffusion approximation solution with jump boundary condition. The effect of parameters on the heat transfer and emissive power distribution in the gas is discussed.
Exergy of Heat Radiation
Authors: Petela R.
Published: February 2012

The idea of exergy—a notion which nowadays is becoming increasingly widespread—was recently introduced into the field of radiation. In this paper formulas for the computation of exergy of heat radiation are set out. The ratio of exergy to the radiation energy has been considered and a discussion is presented of the dependence of substance exergy and radiation on temperature. In addition, the possible applications of radiation energy are mentioned as well as numerical examples using the relations derived in this paper.
A Summary of Experiments on Local Heat Transfer From the Rear of Bluff Obstacles to a Low Speed Airstream
Authors: Sogin H. H.
Published: February 2012

The local heat transfer by forced convection from the base surface of a bluff obstacle in a variety of configurations was measured. The data are satisfactorily represented by an equation of the type hLkf=C·U∞ρfLμf2/3 The coefficient C depends upon the configuration and the location. Its value is uniformly 0.20 on the rear of a flat-plate strip at 90-deg angle of attack. It diminishes wherever any device can close the dead air space, or reduce its size.
On the Application of the Source Theory to the Solution of Problems Involving Phase Change: Part 1—Growth and Collapse of Bubbles
Authors: Yang Wen-Jei , Clark J. A.
Published: February 2012

By use of the source theory approximate solutions are obtained for determining (a) the growth of a vapor bubble in pure liquids and binary liquid mixtures and (b) the growth and collapse of a noncondensing, nonsoluble-gas bubble in a pure liquid. These approximate results for case (a) exhibit good agreement with the existing exact solutions. Case (b) may be applied to the injection of helium gas into liquid oxygen, a problem of current importance in cryogenic rocket systems.
The Effect of Diffusion Thermo and Thermal Diffusion for Helium Injection Into Plane and Axisymmetric Stagnation Flow of Air
Authors: Sparrow E. M. , Minkowycz W. J. , Eckert E. R. G. , Ibele W. E.
Published: February 2012

An analysis has been carried out with the aim of clarifying the effects of diffusion thermo and thermal diffusion on heat transfer, flow, and mass transfer for the helium-air boundary layer in stagnation flow. To provide information applicable to both laboratory-type situations and aerospace applications, results have been obtained over the range of free-stream temperatures from 500 to 5000 deg R. For ratios of wall-to-stream temperature (Tw/Te) which differ only moderately from unity, it is found that the aforementioned diffusional transport has a decisive effect on heat transfer. For example, the heat transfer may be from the fluid to the wall even if Tw > Te. Further, the diffusion thermo is far more important than the thermal diffusion. When Tw/Te is much less than unity (highly cooled wall), the diffusional effects on heat transfer are small. For the condition of the adiabatic wall, the surface temperature (adiabatic wall temperature) can exceed that of the free stream by an appreciable amount. Once again, it is diffusion thermo which is responsible for this. Numerical results are given over a wide range of blowing rate for the Nusselt number, friction factor, and helium concentration at the wall.
The Prediction of Low-Quality Boiling Voids
Authors: Griffith P.
Published: February 2012

Slug flow theory is used to predict the density in heated channels of various shapes. In order to make this calculation possible, measurements are made of the bubble rise velocity in annuli, tube bundles, and channels. It is found that the large dimension is most important in channels and the shroud dimension most important in annuli and tube bundles. It is also found that no rotationally symmetrical bubble shapes are obtained in annuli and tube bundles. Finally, a comparison is made between the theory, which contains no free constants, and the experiments. The comparison is good. The results, as presented, apply only to vertical heated channels of various shapes with up flow in the low-quality region.
Boiling Heat Transfer With Cryogenic Fluids at Standard, Fractional, and Near-Zero Gravity
Authors: Merte H. , Clark J. A.
Published: February 2012

A study is reported of boiling heat transfer with saturated liquid nitrogen under atmospheric pressure at standard, fractional, and near-zero gravity. A drop-tower technique is used to achieve the reduced gravities. Because of the short test time available a transient technique using a sphere as a transient calorimeter is employed to obtain the heat-transfer data. This technique permits the ready acquisition of data in all boiling regimes from the film boiling region through nucleate boiling. Comparison is made with correlations for film boiling and for maximum and minimum heat flux and their corresponding Δtsat.
Measurements of Burnout Conditions for Flow of Boiling Water in a Vertical Annulus
Authors: Becker K. M. , Hernborg G.
Published: February 2012

The present paper deals with measurements of burnout conditions for flow of boiling water in an annulus with an inner diameter of 9.92 mm, an outer diameter of 17.42 mm, and a heated length of 608 mm. Data were obtained in respect of external heating only, internal heating only, and dual uniform and nonuniform heating. The following ranges of variables were studied and 978 burnout measurements were obtained. Pressure: 8.5 < p < 37.5 kg/cm2; Inlet subcooling: 60 < Δtsub < 205 deg C; Steam quality: 0.10 < x < 0.91; Inner surface heat flux: 0 < (q/A)i < 303 W/cm2; Outer surface heat flux: 0 < (q/A)0 < 374 W/cm2; Mass velocity: 71 < m˙/F < 961 kg/m2sec. The results are presented in diagrams where the burnout steam qualities, xBO, were plotted against the pressure with the surface heat fluxes as parameters. The data have been correlated by curves. The scatter of the data around the curves is less than ±5 percent. In the case of equal heat fluxes on both walls of the annulus, burnout always occurred on the inner wall, and the data compared rather well with round duct data. When the annulus was heated internally only, the data showed very low burnout values in comparison with the results for dual heating and round ducts. This disagreement was explained by considering the climbing film flow model and by the fact that only a fraction of the channel perimeter was heated. For external heating the data are somewhat lower than corresponding round duct data, but rather high in comparison with internal heating. The climbing film flow model was also used to interpret this observation. For dual nonuniform heating it was found that the outer surface may be overloaded from 30 to 70 percent compared with the inner surface without reducing the margin of safety in respect to burnout for the annulus. It was further observed that when the heat flux for the wall on which burnout occurs is increased, the burnout steam quality for the channel decreases. If, however, the heat flux for the opposite wall is increased, the burnout steam quality also increases. It was also observed that the highest burnout values are obtained when burnout occurs simultaneously on both cylinders. Finally, the results have been compared with annuli and rod cluster data in published works, and a method for predicting burnout conditions in rod clusters has been proposed.
Condensation Heat Transfer in the Presence of a Noncondensable Gas
Authors: Sparrow E. M. , Lin S. H.
Published: February 2012

A theory has been devised for predicting condensation heat transfer in the presence of a noncondensable gas. The analysis is based on the conservation laws alone and does not utilize empirical data. It is shown that the presence of a very small amount of noncondensable gas in the bulk of the vapor can cause a large buildup of the noncondensable at the liquid-vapor interface. A consequence of this buildup is that the partial pressure of the vapor at the interface is reduced. This, in turn, lowers the temperature at which the vapor condenses and diminishes the effective thermal driving force. Heat-transfer reductions of well over fifty percent may be brought about by the presence of the noncondensable. The predictions of the analysis are compared with condensation heat-transfer measurements for steam with air as noncondensable. The agreement between theory and experiment is satisfactory.
Radiation Effects Upon Boundary-Layer Flow of an Absorbing Gas
Authors: Cess R. D.
Published: February 2012

An analysis has been made to determine the effect of thermal radiation upon heat transfer to boundary-layer flow of an absorbing gas. Laminar flow across an isothermal flat plate is considered, and first-order interaction effects between the convection and radiation processes are evaluated for a gas with Pr = 1.0. The plate surface is assumed to be gray, and two types of gases are considered: a gray gas and a nongray gas for which the monochromatic absorption coefficient is assumed to be independent of temperature. The first-order results for the simplified version of a nongray gas differ substantially from those for the gray gas.
Transient Free Convection About Vertical Plates and Circular Cylinders
Authors: Goldstein R. J. , Briggs D. G.
Published: February 2012

An analysis is made of the transient free-convection, heat-transfer problem from vertical flat plates and vertical circular cylinders to a surrounding initially quiescent fluid. The transient is initiated by a change in wall temperature of the plate or cylinder. A method of predicting the length of time for which a one-dimensional regime of velocity and heat transfer will exist is proposed and solutions are presented. Good agreement is found with the few existing data.
Steady-State Temperature Solution for a Heat-Generating Circular Cylinder Cooled by a Ring of Holes
Authors: Rowley J. C. , Payne J. B.
Published: February 2012

A series solution is presented to the heat-conduction equation for a heat-generating circular cylinder pierced axially by a ring of equal holes spaced uniformly on a concentric circle. The solution is based upon a class of potential functions previously defined by Howland. Typical nondimensional curves for peak and average temperatures and optimum location of the ring of holes for uniform convective cooling are presented. In addition, some shape factors or conductances for the geometry are given.
Steady Free Convection to a Flat Plate With Uniform Surface Heat Flux and Nonuniform Acceleration
Authors: Lemlich Robert , Vardi Joseph
Published: February 2012

Solutions for laminar and turbulent boundary layers are arrived at by means of the integral method. These show that the nonuniformity in acceleration results in distributions (along the plate) for the local heat transfer coefficient and boundary layer thickness which differ from the classical case of uniform acceleration. For the laminar boundary layer under nonuniform acceleration, these distributions yield results for uniform surface heat flux which are identical with those for uniform surface temperature. However, for the turbulent boundary layer, this identity does not apply.
Heat Transfer Across Vertical Layers
Authors: Emery A. , Chu N. C.
Published: February 2012

The heat transferred through vertical plane layers by free convection was measured as a function of the temperature difference across the layer, the height of the layer, and its thickness. Heat transfer coefficients are reported for fluids having Prandtl numbers from 3 to 30,000. An analysis of the problem by means of integral equations yielded results which differed by no more than 12 percent from the measured data in the range in which the equations were applicable.
Maximum Flow Rate of a Single Component, Two-Phase Mixture
Authors: Moody F. J.
Published: February 2012

A theoretical model is developed for predicting the maximum flow rate of a single component, two-phase mixture. It is based upon annular flow, uniform linear velocities of each phase, and equilibrium between liquid and vapor. Flow rate is maximized with respect to local slip ratio and static pressure for known stagnation conditions. Graphs are presented giving maximum steam/water flow rates for: local static pressures between 25 and 3,000 psia, with local qualities from 0.01 to 1.00; local stagnation pressures and enthalpies which cover the range of saturation states.
Heat Transfer by Conduction and Radiation in Absorbing and Scattering Materials
Authors: Viskanta R.
Published: February 2012

Heat transfer by simultaneous conduction and radiation in thermal radiation absorbing, emitting, and scattering materials is investigated theoretically. Consideration is given to a one-dimensional system consisting of two diffuse, nonblack, isothermal parallel plates separated by a finite distance. The space between the two plates is filled with an isotropically scattering material. The problem is formulated exactly in terms of integrodifferential and integral equations. The results define as well as illustrate several mechanisms of radiant energy transfer and show how one mode of heat transfer influences the other. The numerical results reveal the effect of the system parameters on the heat transfer characteristics. In particular, it is shown that the effect of albedo on the heat transfer is small. Albedo being the parameter which represents the fraction of the incident pencil of radiation which has been scattered.
Photographic Study of Nucleate Pool Boiling on a Horizontal Surface
Authors: Gaertner R. F.
Published: February 2012

A photographic study was made of saturated nucleate pool boiling at a pressure of one atmosphere. Over 1000 still photographs and 12 high-speed motion pictures were taken of water boiling from a 2-in-dia flat horizontal surface facing upward. Two surfaces were studied, a 2/0 polished platinum surface and a 4/0 polished copper surface. The platinum surface was studied in the heat flux range of 14,700 to 176,000 Btu/hr, sq ft, and the copper surface from the incipient boiling heat flux of 10,500 Btu/hr, sq ft to the maximum flux of 493,000 Btu/hr, sq ft. Data were obtained for the breakoff diameters of discrete bubbles, and for the populations of active sites at heat fluxes up to 58,600 Btu/hr, sq ft. At least three, and possibly four, heat-transfer regions were found to exist in nucleate boiling, depending upon the mode of vapor generation. The vapor structures on the surface progressed through a sequence of first discrete bubbles, then vapor columns and vapor mushrooms, and finally vapor patches, as the surface temperature was increased. These individual vapor structures, or combinations of them, determine the mechanism of heat transfer in the four nucleate boiling regions. It was concluded that any heat-transfer model or design equation which is based on the dynamics of individual bubbles, or on any other single mechanism, must be in serious error.
Heat Transfer Characteristics of the Closed Thermosyphon
Authors: Bayley F. J. , Lock G. S. H.
Published: February 2012

This paper describes a series of closely controlled experiments made to investigate the performance of the closed thermosyphon. All the regimes previously observed in the open system were identified, and suggestions are made concerning the nature of the process by which the heated and cooled regions of the thermosyphon are hydrodynamically coupled together. A theoretical analysis of the laminar boundary layer regime is given and comparisons made with the experimental results.
Transient Heat Conduction at High Thermal Flux
Authors: Lindholm U. S. , Baker E. J. , Kirkpatrick R. C.
Published: February 2012

Transient heat conduction in a copper rod was studied using an arc-imaging furnace to supply pure radiant thermal energy at flux levels up to 1000 cal/cm2-sec. No significant effects were observed attributable to the rate of heating up to and through melting at the surface. Transient temperature profiles agree well with theory and melting was initiated at its equilibrium temperature. The dynamics of the vaporization process are more uncertain.
An Analytical Solution of the Effect of Peripheral Wall Conduction on Laminar Forced Convection in Rectangular Channels
Authors: Siegel R. , Savino J. M.
Published: February 2012

This study deals with fully developed laminar forced convection in rectangular channels that are heated on the broad sides. The analysis determines the effect of peripheral heat conduction within the heated walls on the wall temperature distributions. The unheated short side walls are assumed nonconducting. The heat conduction within the broad walls was formulated in terms of an integral equation and coupled with the convective energy equation within the fluid. Analytical solutions were obtained where the heating extends over the entire width of the broad side, is removed from the corner region, or extends beyond the corner into the side wall. Transverse wall conduction produced substantial decreases in the peak wall temperature and in the temperature gradients along the long side.
Effect of Large Temperature Gradients on Convective Heat Transfer: The Downstream Region
Authors: McEligot D. M. , Magee P. M. , Leppert G.
Published: February 2012

The results of an experimental investigation of the frictional and heat transfer effects in air, nitrogen, and helium in steady, turbulent flow in round tubes are presented. Wall-to-bulk temperature ratios extend from near unity to 2.5, entering Reynolds numbers from 15,000 to 233,000. Dependence of the thermodynamic and transport properties on temperature is shown to be significant in both heat transfer and wall friction and is reflected in the empirical correlations for local and average coefficients which are developed. The results of other investigators who have analyzed or measured variable properties effects are recalculated where necessary to facilitate comparisons.
A Theoretical Analysis of Laminar Forced Flow and Heat Transfer About a Rotating Cone
Authors: Tien C. L. , Tsuji I. J.
Published: February 2012

The present paper presents analytically a method of attack on the problem of laminar forced flow and heat transfer about a rotating cone. The nonsimilar nature of the general problem requires that separate consideration be given to a slow rotating cone and a fast rotating cone, depending on the relative magnitude of the rotating speed with respect to the free-stream velocity. The Mangler transformation first reduces the problem of a slow rotating cone to one of wedge flow with a transverse velocity component. The problem is then solved by a perturbation scheme which uses the solution of wedge flow as the zeroth-order solution. The case of a fast rotating cone is solved by a series-expansion scheme which gives successive corrections to the zeroth-order solution, i.e. the solution of a rotating disk in a quiescent fluid. The zeroth-order and first-order equations for both cases are given in the present work, together with the numerical results for the special case of a cone of about 107-deg cone angle. The first-order results in both cases are shown for the drag and torque coefficients, and the local Nusselt number. Higher-order results can be obtained according to the present analysis. The effect of cone angle on the flow and heat-transfer characteristics is indicated by the comparison between the results of the 107-deg cone and those of the disk, i.e., the 180-deg cone.
Condensation of Vapor on a Vertical Plate With a Transverse Electrostatic Field
Authors: Velkoff H. R. , Miller J. H.
Published: February 2012

An exploratory experimental program was conducted to determine the improvements in heat transfer which could be achieved in the condensation of vapor by the application of electrostatic fields. Freon-113 was utilized as the working fluid in the tests, and condensation of the Freon vapor was produced on a cooled vertical copper plate. A series of electrodes was utilized to vary field strength and geometric configuration of the field, and the particular electrostatic action being studied. Results of the tests indicated that very large increases in heat transfer can be obtained with the use of screen electrodes placed parallel to the cooled copper plate. Increases of 150 percent were achieved which were controllable and readily reproducible.
Laminar Free Convection From a Nonisothermal Cylinder
Authors: Koh J. C. Y. , Price J. F.
Published: February 2012

Laminar free convection from a nonisothermal horizontal cylinder is analyzed. The wall surface temperature is assumed to be varied in the manner of a1(x/R)2 + a2(x/R)4. Special transformations are devised and employed so that the resulting differential equations and boundary conditions are free of the parameters a1 and a2. These differential equations are solved once and for all; solutions to the original equations for any particular values of a1 and a2 may then be read off easily as linear combinations of the numerical solutions given here. It is found that the dependence of heat transfer from a horizontal cylinder on Prandtl number is practically the same as that from a vertical plate. Furthermore, the heat transfer is greatly influenced by the surface temperature variations.
Thermal Contact Resistance in a Vacuum Environment
Authors: Clausing A. M. , Chao B. T.
Published: February 2012

A restrictive analysis based on a new model is presented for the prediction of thermal contact resistance in a vacuum environment. It is demonstrated that, for many surfaces commonly encountered in engineering practice, the macroscopic constriction has a commanding influence. Extensive results are given for brass, magnesium, stainless steel, and aluminum surfaces which show the effects of material properties and the degree of conformity of mating surfaces under load. Limited results are presented to show the influence of surface films, surface roughness, creep, additional interstitial material, mean interface temperature, etc. Good agreement between the measured and predicted values of the thermal contact resistance was found over wide ranges of the applied load and other system variables.
Convectively Cooled Thermoelements With Variable Cross-Sectional Area
Authors: Rollinger C. N.
Published: February 2012

The differential equations which describe the one-dimensional temperature distribution in a convectively cooled thermoelement with variable cross-sectional area are presented and solved analytically with appropriate boundary conditions. Expressions for the maximum heat pumping and the maximum temperature difference are developed. Sample computations for two families of shapes are presented, and a comparison is made between the performance of a constant-area element and the performance of a variable-area element. It is shown that under certain conditions shaping the element can enhance the performance gains to be derived from the use of convective cooling along the length of the element. The results seem to indicate that in certain special applications—especially those in which it would be desirable to use little or no insulation along the element near the cold junction—shaped, cooled elements will offer some performance advantages over cooled, constant-area elements.
Laminar Heat Transfer in Noncircular Ducts by Moire´ Method
Authors: Cheng K. C.
Published: February 2012

This note describes the application of moire´ method to forced convection problems for a fully developed laminar flow in non-circular ducts with a constant longitudinal wall temperature gradient. It is pointed out that the method is applicable to any complex polygonal-shaped duct and to any annular polygonal-shaped duct. Some properties and limitations of the moire´ method are pointed out.
Experiments on the Diffusion Thermo Effect in a Binary Boundary Layer With Injection of Various Gases
Authors: Sparrow E. M. , Scott C. J. , Forstrom R. J. , Ebert W. A.
Published: February 2012

The free convection heat and mass transfer about a porous horizontal cylinder is investigated experimentally. Various gases, which are either preheated or precooled, are injected through the porous cylinder into an otherwise quiescent air environment. The gases include hydrogen, helium, carbon dioxide, and Freon-12; the first two of these have molecular weights less than that of air while the latter two have molecular weights greater than that of air. It is found that for the condition of no net heat transfer at the surface, the temperature of the surface differs from the temperature of the environment. The existence of the aforementioned adiabatic wall temperature is due to the diffusion thermo effect. When hydrogen or helium is the injected gas, the adiabatic wall temperature exceeds the ambient temperature by as much as 100F. On the other hand, when carbon dioxide or Freon-12 is the injected gas, the deviation between adiabatic wall and ambient temperatures is both much smaller and of opposite sign relative to that noted previously. Nusselt number results are also reported and discussed. Comparisons of the experimental findings with those of analysis are made whenever possible.
Moving Heat Sources With Change of Phase
Authors: Jackson F.
Published: February 2012

The theory of moving heat sources in the quasi-steady state has been developed and finds applications in welding, flame cutting, and other processes. The theory is now extended to include phase changes in rods and in infinite media arising from plane sources.
Subcooled Swirl-Flow Boiling and Burnout With Electrically Heated Twisted Tapes and Zero Wall Flux
Authors: Gambill W. R.
Published: February 2012

A series of swirl-flow tests was conducted in which all of the heat was generated in twisted-tape swirl generators. This is in contrast to past ORNL swirl-flow tests with twisted tapes, in which ∼99 percent of the heat was generated in the metallic tube wall. In the present study, water from a constant-head tank flowed by gravity at 5 to 8 fps through a vertical 0.27-in.-ID glass tube ∼13 in. long, in which was located a resistance-heated, 16-mil-thick A-nickel tape. Tape-twist ratios were varied from 2.7 to ∞ inside tube diameters/180-deg twist, inlet water temperatures from 63 to 173 F, and heat fluxes from 0.21 × 106 to 1.20 × 106 Btu/hr·ft2. The water head above the top of the tube was held at 30.7 in. In all cases, the critical wall superheat increased with decrease of tape-twist ratio, whereas the critical heat fluxes for the twisted tapes fell between 93 percent and 122 percent of those for flat tapes, maximizing in all cases at a tape-twist ratio of 7 to 10. It is postulated that the deleterious effect of centripetal acceleration with this geometry, which tends to hold the vapor on the heated surface, is compensated in the swirl-flow entrance region by inertial impingement of the liquid onto the tape surface, and along the remainder of the length by a double-vortex secondary flow pattern in the plane normal to the tube wall. The power density of a swirl-flow tube assembly may therefore be significantly increased by generating heat in the twisted tape as well as in the tube wall.
Heat Transfer to a Nonisothermal Rotating Disk With a Turbulent Boundary Layer
Authors: Hartnett J. P. , Tsai Shing-Hwa , Jantscher H. N.
Published: February 2012

Three approaches are presented for the prediction of heat transfer from a nonisothermal disk rotating in a fluid of infinite extent at such high speeds that the induced flow is turbulent. These include the analysis of Dorfman, the analysis of Davies (extended to nonisothermal conditions) assuming the eddy diffusivity of radial momentum is equal to the eddy diffusivity of heat, and a modified Davies analysis assuming the eddy diffusivity of tangential momentum is equal to the eddy diffusivity of heat. A comparison of these three predictions with available heat and mass transfer data suggests that Dorfman’s analysis when appropriately modified gives the best representation for the isothermal rotating disk. For the nonisothermal disk having a power-function wall-temperature distribution, Tw − Te = Brm, both the Dorfman analysis and the tangential momentum analogy give what appears to be a reasonable estimate of the influence of the nonisothermal condition, while the radial momentum analogy overestimates the influence. Until additional data are obtained, it is recommended that the modified Dorfman prediction be used to estimate heat transfer from a nonisothermal disk in the presence of turbulent flow.
A Photographic Study of Boiling in an Accelerating System
Authors: Beckman W. A. , Merte H.
Published: February 2012

Pool boiling of distilled and degassed water in an accelerating system was studied by means of high speed motion pictures, up to 20,000 frames per sec. The acceleration was produced by the centrifuge principle with the heating surface oriented normal to the vectorial sum of the centrifugal acceleration and the gravitational acceleration. The range of experimental variables include: heat flux between 16,000 and 72,000 Btu/hr-ft2, acceleration between one and 100 times standard gravitational acceleration, and subcooling of 2 and 10 deg F. From the photographs, data are presented on bubble growth rates, departure sizes, frequency of formation, and departure contact angles.
Radiation Exchange in an Enclosure With Directional Wall Properties
Authors: Bevans J. T. , Edwards D. K.
Published: February 2012

Three methods of increasing exactness are given for calculating the radiant exchange within a multisurface enclosure made up of “real” surfaces. The first approximation considers the directional characteristics of the thermal radiation properties but does not include specular interreflections. The second method incorporates an approximation for specular reflection as well as the directional behavior of real materials. Solutions of the radiant exchange within an enclosure by these two methods are shown to be no more complex than existing techniques for perfectly diffuse enclosures [1, 2]. The third approximation, while more exact, involves a more detailed but not impractical method of solution. Comparisons of the three approximations to the nondirectional diffuse and specular computational methods [8, 9] are presented, and the importance of considering the directional characteristics of thermal radiation properties is shown.
Correlation of Sound Generation and Heat Transfer in Boiling
Authors: Schwartz F. L. , Siler L. G.
Published: February 2012

The generation of sound accompanying boiling heat transfer is common knowledge. The intensity of the sound varies with the rate of heat transfer. This study was inaugurated to determine whether a correlation existed between intensity and frequency with the rate of heat transfer.
On Heat Transfer From Isothermal and Nonisothermal Spinning Bodies of Revolution
Authors: Hayday A. A.
Published: February 2012

The class of similar flows engendered by bodies of revolution rotating uniformly about axes of symmetry in an otherwise undisturbed fluid is studied. Local heat transfer by forced convection is determined theoretically for laminar flows under both isothermal and nonisothermal surface conditions. It is shown that the known solutions for rotating disks and cones are special cases which fall within the scope of this analysis. The flows are in general characterized by continuously thinning boundary layers formed along the body surface. Criteria which determine such boundary-layer behavior are related to the similarity transformations and also to the rates of change of cross-sectional areas of the bodies in question. The thinning boundary layers imply higher local friction and moment coefficients than those found for comparable cones. The same is true for local Nusselt numbers. Estimates of the region of validity of the results are given, and the results are tabulated for several Prandtl numbers. The role of free convection is discussed briefly.
Pressure Distribution and Heat Transfer for Flow Over Simulated Cylindrical Parachutes
Authors: Koh J. C. Y. , Hartnett J. P.
Published: February 2012

The aerodynamic and heat-transfer characteristics for flow over an upstream-facing cylindrical cup simulating a parachute geometry were studied. It was found that: (1) The pressure on the bottom of the cup increases as the depth of the cup increases. (2) An increase in the free-stream turbulence level increases the aerodynamic heat transfer significantly. (3) The heat transfer front the bottom of the cup decreases monotonically as the depth of the cup increases. (4) The effect of suction at the cup bottom is to equalize the pressure distribution and to increase the heat transfer.
Heat Transfer Characteristics of Impinging Two-Dimensional Air Jets
Authors: Gardon Robert , Akfirat J. Cahit
Published: February 2012

Local as well as average heat transfer coefficients between an isothermal flat plate and impinging two-dimensional jets were measured for both single jets and arrays of jets. For a large and technologically important range of variables the results have been correlated in relatively simple terms, and their application to design is briefly considered.
Macroscopic Interface Shape During Solidification
Authors: Wilcox W. R. , Duty R. L.
Published: February 2012

Steady-state heat transfer considerations have been used to determine the macroscopic solid-liquid interface shape in solidification processes such as floating zone melting and crystal pulling. It was found by means of computer solutions that the Biot number haR/k, is the prime determinant of the shape of the interface. As the Biot number increases, the interface becomes increasingly concave into the solid. A uniform heat input model was formulated which gives analytical results close to the computer results. A one-dimensional analysis showed that the fractional error in the position of the isotherms caused by ignoring the heat carried by the motion of the crystal is approximately Vρcp−R/8hak. The effect of various heat transfer parameters on the dislocation generation caused by thermal stresses was also predicted and found to compare fairly well with experimental results.
Measurement of the Thermal Conductivity of Noble Gases in the Temperature Range 1500 to 5000 Deg Kelvin
Authors: Collins D. J. , Menard W. A.
Published: February 2012

The thermal conductivities of argon, neon, and krypton in the temperature range 1500 to 5000 deg Kelvin have been deduced from the measurement of heat transfer rates from the heated gases to the end wall in the reflected shock wave. Pressures ranged from approximately 1/2 atm to 3 atm. The relationship between thermal conductivity and temperature was assumed to be of the form k = aTb. The constant “b” was determined by a best fit to the data and the constant “a” by the known values of “k” below 1500 K. The effect of density variation in the thermal boundary layer was found to be significant in reducing the data; some previous investigations have neglected this effect.
Theory of Nonequilibrium Thermodynamics With Application to the Transport Processes in a Solid
Authors: El-Saden M. R.
Published: February 2012

The theory of nonequilibrium thermodynamics for inherently irreversible coupled processes is presented and the concept of heat is incorporated appropriately. The theory was applied to the problem of a solid carrying electric and heat currents in the presence of an external magnetic field. The principle of increase of entropy was employed to determine the reversibility or irreversibility of the macroscopic effects involved and to determine the limits on the material’s properties. The dynamic equations show that, in the one-dimensional thermoelectric case, the heat current is not coupled to the electrical phenomenon. In two and three-dimensional cases, the heat current is coupled to the electrical phenomenon only through the influence of the external magnetic field. Areas of disagreement with the literature are pointed out and discussed.
Evaporation From a Draining Liquid Film
Authors: O’Loughlin J. R.
Published: February 2012

The thickness of a laminar liquid film draining from a vertical surface is found analytically under the assumption that the evaporation rate from the surface of the film is a known constant. The transient is studied as well as the steady solution. Expressions are found for the location where the film vanishes as well as for the rate of evaporation and total mass evaporated until any time.
On Correlating the Peak and Minimum Boiling Heat Fluxes With Pressure and Heater Configuration
Authors: Lienhard John H. , Watanabe Kiyokazu
Published: February 2012

The peak nucleate boiling heat flux has been observed for five fluids during saturated pool boiling on horizontal wire heaters, ranging in radius from 0.0025 in. to 0.0254 in., over a reduced pressure range from 0.0010 to 0.0197. A scheme for correlating the peak and minimum heat fluxes is developed heuristically and successfully applied to these data. The result is a single three-dimensional surface which represents all of the data. The surface can be represented as the product of a function of geometric scale, and a function of pressure. The function of pressure appears to be the same in any configuration.