bluuebunny/crossref_metadata_2025 huggingface dataset:
Heat Transfer by Combined Conduction and Radiation Between Concentric Spheres Separated by Radiating Medium
Authors: Viskanta R. , Merriam R. L.
Published: February 2012

Steady-state heat transfer by simultaneous conduction and radiation through a spherical shell of absorbing, emitting, and scattering medium has been investigated analytically. The medium is confined between two gray, diffuse, isothermal spheres kept at different but uniform temperatures and is capable of generating heat. The problem is formulated rigorously using exact radiative transfer methods. The governing equations were solved numerically using an iterative scheme. The results reported illustrate the interaction of conduction with radiation heat transfer as well as reveal the effects of the parameters on the heat transfer characteristics. A simple approximation is suggested for predicting total heat transfer through a spherical shell from the results through a plane layer. The results are compared with available solutions and super position approximations.
Equilibrium Temperatures in a Boundary-Layer Flow Over a Flat Plate of Absorbing-Emitting Gas
Authors: Taitel Yehuda , Hartnett J. P.
Published: February 2012

The effect of radiation on the equilibrium temperature for a flow of emitting-absorbing gas over a flat plate is studied. Three methods of solution are formulated: An approximate solution for a thin boundary layer, a similarity solution for the limiting case when the boundary layer is optically thick, and an exact solution. Emphasis is put on the study of the recovery or adiabatic wall case, where conduction to the wall is balanced by the net radiation away from the wall. Results are reported for the limiting cases of a black plate and completely reflective plate and for a unit Prandtl number. The exact solution reflects very favorably on the use of the approximate methods and points out clearly the conditions for which the approximate solutions are applicable. Results are also reported for the equilibrium wall temperature for the case of constant heat flux and for the recovery factor in the case of blowing and suction; both for optically thin boundary layers. Special attention is put on the interaction mechanism and the role of the emitting-absorbing coefficient on this process. It is shown that, for small absorption coefficient, high wall emissivity, and Mach number, the results approach the case where the gas is transparent.
Incipient Boiling Superheats in Liquid Metals
Authors: Chen J. C.
Published: February 2012

Measurements were obtained of the superheat required to initiate incipient boiling of potassium in forced convective flow. Emphasis was placed on determining the effect of preboiling, deactivation conditions on subsequent incipient-boiling superheat. Data were obtained with deactivation subcoolings of 10 to 380 deg F, boiling temperatures of 1295 to 1600 deg F, and boiling pressures of 8 to 24 psia. Measured superheats ranged from 17 to 117 deg F. Sufficient data were obtained to indicate the functional dependence of incipient-boiling superheats on each of the three independent variables: deactivation pressure, deactivation temperature, and boiling pressure. The experimental results were found to be in substantial agreement with an analytical model developed herein. The proposed correlating equation was generally correct in predicting both the magnitude of the superheat and in its functional dependence on each of the independent variables.
Dynamics of Moving Gas Bubbles in Injection Cooling
Authors: Tokuda N. , Yang W. J. , Clark J. A.
Published: February 2012

This paper presents a study of the growth or collapse of a spherical gas bubble being injected into a quiescent liquid of different compositions. The influence of translatory bubble velocity is given particular attention. Consideration is given to the case in which the bubble dynamics is governed by heat and mass transfer between the bubble and the liquid. By approximating the flow around the bubble as irrotational, two asymptotic solutions, valid for small and large times, respectively, are obtained for the thermal boundary layer over the bubble through the use of a coordinate perturbation technique. The bubble behavior in the two time domains is satisfactorily joined at a certain time interval. It is disclosed that the transient bubble size, interfacial temperature, and interfacial gas composition are governed by four dimensionless parameters. Translatory bubble motion is shown to cause a significant increase in the growth rate, an effect also provided by an increase in the Jakob number. Experimental results are cited and a favorable comparison with the theory is obtained.
Nucleate Pool Boiling of Nitrogen With Different Surface Conditions
Authors: Marto P. J. , Moulson J. A. , Maynard M. D.
Published: February 2012

Pool-boiling heat transfer of liquid nitrogen from circular, 1-in.-dia horizontal disks was studied. Surface conditions included copper and nickel mirror finishes, and copper surfaces which were roughened, grease-coated, and Teflon-coated. Artificial cavities were manufactured, including mechanically drilled cylindrical holes of diameter 0.0043 and 0.015 in., and also a 0.022-in.-dia spark cut conical hole. Results indicate that a systematic testing procedure is necessary to obtain reproducible nucleate-boiling data. Surface roughness and surface material alter the nucleate-boiling curve. A grease coating significantly decreases the nucleate-boiling heat-transfer coefficient. A Teflon coating has very little effect. Past history of the test surface, including the length of time spent while boiling, can change boiling results. The effect of artificial cavities on both natural convection and nucleate-boiling was determined.
Gas Solids Suspension Convective Heat Transfer at a Reynolds Number of 130,000
Authors: Briller R. , Peskin R. L.
Published: February 2012

An experiment was performed to determine the convective heat-transfer coefficient to heated and cooled gas solids suspensions at a Reynolds number of 130,000. Measurements of the heat transfer were performed by traversing the stream at various locations along the pipe with specially designed probes which measured air and particle temperature locally. The results showed that for a high Reynolds number, the heat-transfer coefficient for the suspension appears to be equal to that of the pure gas at the same Reynolds number, and independent of solids loading ratio, heating or cooling, and particle size (between 0.0011 and 0.0058 in. dia).
Turbulent Flow in an Annulus
Authors: Levy S.
Published: February 2012

Equations describing fully developed turbulent flow in an annulus are derived. They are based upon Reichardt’s expression for the eddy diffusivity of momentum, and they assume that the velocity profiles starting from the core tube wall and the outer tube wall have the same velocity and eddy diffusivity at the plane of zero shear. The predicted location of the plane of zero shear, mixing length, eddy diffusivity, velocity distribution, and friction factor are compared to available data and are found to give good agreement with the test results. Potential extension of the proposed method to more complex geometries is illustrated by considering the case of flow in an annulus with one artificially roughened surface.
Simulation of Space Conditions and Thermal Behavior of Spacecraft
Authors: Hassan Kamal-Eldin
Published: February 2012

The present paper treats the problem of simultaneously simulating the spacecraft and space. The combined problem is analysed, and the similarity groups that affect this simulation are deduced; they include a criterion from which it is possible to determine the extent to which actual space is simulated by a facility. The analysis takes into account the effect of the earth on the thermal behavior of an artificial satellite, and the means by which this effect could be simulated. The problems involved in simulating space with “warm-walled” chambers, important from the viewpoint of reducing initial and operation costs, are discussed in length.
Optimization of Some Radiators With Fins and Involute Reflectors
Authors: Hwang-Bo H.
Published: February 2012

The maximum heat rejection per unit weight of radiator with involute-type reflectors is compared with those of some radiators with optimum rectangular fins by means of examples. The mutual irradiations among the surfaces of neighboring radiator parts are considered in computing the view factors.
Effect of Polarization on Radiant Heat Transfer Through Long Passages
Authors: Edwards D. K. , Tobin R. D.
Published: February 2012

Theoretical predictions of radiant transfer through long passages are shown to be quite sensitive to directional variation of radiation characteristics and to polarization of the radiation. With use of the Fresnel relations for specular reflection to find the amount and state of polarization of radiation reflected by dielectric and metallic walls, values of transmittance are calculated and tabulated for long passages of square and infinite slot cross sections with lengths of up to 30 times the lateral distance between walls. Differences in answers by factors up to 14 are shown to result from neglect of directional variation, polarization, and phase change in the reflection process. A simple, approximate analytical relation is presented to permit transmittance and integrated transmittance obtained for isothermal passage walls to be used to calculate transfer in passages with adiabatic or refractory walls.
Heat Transfer of Thin Fins With Temperature-Dependent Thermal Properties and Internal Heat Generation
Authors: Hung H. M. , Appl F. C.
Published: February 2012

An analytical study of the temperature distribution along thin fins with temperature-dependent thermal properties and internal heat generation is presented. The analysis utilizes a recently published bounding procedure which yields analytical and continuous bounding functions for the temperature distribution. Several numerical examples are considered. Tabular and graphical results are given. The effects of variable thermal properties and internal heat generation are also shown.
Effects of Free-Stream Turbulence and Pressure Gradient on Flat-Plate Boundary-Layer Velocity Profiles and on Heat Transfer
Authors: Junkhan G. H. , Serovy G. K.
Published: February 2012

Experimental data indicating some effects of free-stream turbulence intensity on time-average boundary-layer velocity profiles and on heat transfer from a constant-temperature flat plate with a favorable pressure gradient are presented for local Reynolds numbers ranging from 4 × 104 to 4 × 105 and for free-stream turbulence intensities from 0.4 to 8.3 percent. It is concluded that, for the range of variables covered by the experiments: (a) The effect of free-stream turbulence intensity on heat transfer through the laminar boundary layer with a zero pressure gradient is negligible; (b) for a given Reynolds number, the local Nusselt number increases with increasing free-stream turbulence intensity when a pressure gradient is present, the boundary-layer profiles for these conditions changing with a variation in free-stream turbulence intensity; and (c) no increase in Nusselt number with increase in free-stream turbulence intensity occurs for turbulent boundary layers with a favorable pressure gradient.
Momentum and Heat Transfer in Laminar Flow of Gas With Liquid-Droplet Suspension Over a Circular Cylinder
Authors: Goldstein M. E. , Yang Wen-Jei , Clark J. A.
Published: February 2012

An analysis has been made to determine the heat transfer and friction characteristics in a two-phase (gas-liquid) flow over a circular cylinder. It is demonstrated that the resulting two-layer flow problem can be formulated exactly within the framework of laminar boundary layer theory. Two cases are studied; (1) For the parameter E greater or equal to 0.1 and the drop trajectories straight and, (2) For E less or equal to 0.1 and for any drop trajectory. Solutions obtained in power series include the local liquid-film thickness, velocity and temperature profiles, skin friction and Nusselt number. Numerical results disclose a significant increase in both heat transfer rate and skin friction over those of a pure gas flow. The theoretical prediction compares favorably with experimental results of Acrivos, et al. [1].
Radiative Heat Transfer Between Parallel Plates Separated by a Nonisothermal Medium With Anisotropic Scattering
Authors: Hsia H. M. , Love T. J.
Published: February 2012

The problem of radiative heat transfer in a nonisothermal medium is considered. The analysis is carried out for a plane parallel atmosphere separated by a cloud of particles which scatters radiant energy in an anisotropic fashion. Linear and isothermal temperature profiles are compared for enclosures with partially reflecting diffuse boundaries. The solutions are obtained by representing the integral term of the radiative transport equation by a quadrature. The resulting set of nonhomogeneous differential equations are solved utilizing the method of idempotents.
Radiation Heat Transfer in Nonisothermal Nongray Gases
Authors: Edwards D. K. , Glassen L. K. , Hauser W. C. , Tuchscher J. S.
Published: February 2012

Experimental measurements of absorption and emission by nonisothermal CO2 and H2O gases are reported. Analytical formulations and calculations of radiant heat transfer using a simple nongray gas model are presented. It is found that a gray gas model cannot predict even qualitatively the experimental results, while the band model method of calculation yields results in quantitative agreement for total emission and absorption in a band. Effects of line structure are shown to be of secondary importance compared to band envelope structure for line-width-to-spacing ratios above 10−2 in saturated bands. An analytical solution for coupled convection and radiation in a plane-parallel-wall duct is derived to illustrate the utility of the exponential band model for analysis of radiant transfer in nonisothermal, nongray gases.
Laminar Forced Convection in the Entrance Region Between Parallel Flat Plates
Authors: Mercer W. E. , Pearce W. M. , Hitchcock J. E.
Published: February 2012

Interferometer measurements of laminar forced convection to air in the entrance region between parallel flat plates are reported. Experimental local and mean Nusselt numbers are given for Reynolds numbers from 300 to 1500 and length-to-plate spacing ratios from 2 to 8. The experimental data are compared with corresponding values from theoretical analyses of simultaneously developing momentum and thermal boundary layers for the two cases considered: Air heated by both plates with the same uniform temperature, and air heated by one plate with a uniform temperature and other insulated. Equations are also given which summarize the theoretical results.
Directional Emissivities From a Two-Dimensional, Absorbing-Scattering Medium: The Semi-Infinite Slab
Authors: Bobco R. P.
Published: February 2012

A closed-form solution is presented for the directional emissivity at any location on the surface of a semi-infinite slab of an absorbing-scattering medium. The medium is assumed to be a gray, isothermal dispersion which emits, absorbs, and scatters isotropically, and is confined by free boundaries. The solution to this two-dimensional problem is found by the approximate technique based on an iteration of the solution to the diffusion equation. Polar plots of directional emissivity are presented which show the influence of optical thickness, surface location, and scattering strength (albedo).
Combined Forced and Free Turbulent Convection in a Vertical Circular
Tube With Volume Heat Sources and Constant Wall Heat Addition
Authors: Ojalvo M. S. , Anand D. K. , Dunbar R. P.
Published: February 2012

A study is made of turbulent heat transfer in a vertical circular tube under conditions of combined forced and free convection with uniform heat flux at the wall and volume heat sources. The basic conservation laws are reduced to three coupled, linear integrodifferential equations which are numerically solved by means of a digital computer. An improved expression for eddy viscosity variation with radial distance and degree of turbulence is used in the solution, as is an expression for the ratio of eddy diffusivity of heat to momentum. The parameters in the integrodifferential equations are: Prandtl number, Pr; Rayleigh number, Ra; friction Reynolds number, Re*; and a volume heat source parameter, F. For fixed values of these parameters, the solution results in: the velocity and temperature profiles; the pressure drop parameter, C; mixed-mean-to-wall temperature difference, φm; Nusselt number, Nu; and Reynolds number, Re. The solutions to this fairly general problem compare very closely to solutions of the following special cases (with no volume heat source): pure forced convection, laminar flow; pure forced convection, turbulent flow; and combined forced and free-convection, laminar flow.
Gravitational Effects on the Thermal Instability
Authors: v. Krzywoblocki M. Z.
Published: February 2012

The author demonstrates that the decreasing gravitational field induces greater thermal stability against disturbances and vice versa. Some remarks on the effects of surface stresses and on the possible methods of calculating them by using optimization techniques close the work.
Numerical Solutions to an Inverse Problem of Heat Conduction for Simple Shapes
Authors: Stolz G.
Published: February 2012

Numerical methods are presented for solving an inverse problem of heat conduction: Given an interior temperature versus time, find the surface heat flux versus time. The analysis is developed specifically for spheres; it applies to other simple shapes. The system is treated as linear, permitting use of the superposition principle. The essence of the method is the numerical inversion of a suitable direct problem: Given a surface heat flux versus time, find an interior temperature versus time. Care is required in selecting a time spacing for, if it is chosen too small in relation to the conditions, undesirable oscillation results. Simplifying suggestions are presented, and the use of the methods are illustrated by examples.
Measurement of the Thermal Conductivities of Gases at High Temperatures
Authors: Vines Robert G.
Published: February 2012

Experimental results are reported for the thermal conductivities of air, argon, nitrogen, and carbon dioxide at temperatures up to 900 C, and of steam up to 560 C. These results are compared with values predicted from correlation formulas based on low temperature measurements.
Heat Transfer From Transverse and Yawed Cylinders in Continuum, Slip, and Free Molecule Air Flows
Authors: Baldwin Lionel V. , Sandborn Virgil A. , Laurence James C.
Published: February 2012

A general Nusselt number correlation is presented for transverse cylinders in subsonic and supersonic air flows where dissociation is negligible. New and existing data in the following experimental range have been correlated: Mach M = 0.001 to 6.0, Reynolds NRe = 0.02 to 300,000, Knudsen NKn = 4 × 10−6 to 37. In subsonic flow, heat transfer from a cylinder yawed at an angle to the air velocity is predicted by the transverse cylinder Nusselt number correlation when the normal velocity component is used as the characteristic velocity. Finally, recovery temperature data from cylinders are divided into three regimes by a Knudsen number criterion.
Conical Turbulent Boundary Layer Experiments and a Correlation With Flat Plate Data
Authors: Bradfield W. S.
Published: February 2012

Measurements in the turbulent boundary layer of unyawed cones for Mach numbers from 1 to 6 are presented. Specifically, the first measurements of total temperature profiles, directly determined skin friction, and local heat flux in the turbulent boundary layer of cone models are given. In addition, these experimental data are shown to justify the calculation of turbulent friction and heat transfer on unyawed cones by means of an incompressible plate friction law and simple auxiliary relations.
Unsteady Turbulent Heat Transfer in Tubes
Authors: Sparrow E. M. , Siegel R.
Published: February 2012

An analysis is made of the unsteady turbulent heat transfer in a circular tube whose wall temperature varies arbitrarily with time. The flow is steady and fully developed. The formulation permits the heat-transfer coefficient to vary with time and position in accordance with the energy conservation principle. This is in contrast to previous transient analyses where it has been standard to use steady-state, fully developed coefficients. The first step in the analysis yields the heat-transfer response to a step jump in wall temperature, and this is then generalized by a superposition technique to apply to arbitrary time variations. Use of the generalized results is illustrated by application to the case where the wall temperature varies linearly with time. Comparison is made between the unsteady heat-transfer results of the present theory and those computed using steady-state heat-transfer coefficients.
Improved Lumped Parameter Method for Transient Heat Conduction Calculations
Authors: Elrod H. G.
Published: February 2012

A general mathematical method is presented suitable for the “lumping” of many damped linear systems when the response function and the forcing function can be related by a convolution integral. The method is illustrated by application to transient heat conduction in slabs and cylindrical rods. An ordinary differential equation (equation 26) relating the mean temperature of these bodies to their surface temperature is derived, and then applied to the solution of several problems. Agreement with exact results is found to be excellent except for very rapid transients. Means for estimating error are provided in the paper.
Heat-Transfer and Flow-Friction Characteristics of Crossed-Rod Matrices
Authors: London A. L. , Mitchell J. W. , Sutherland W. A.
Published: February 2012

The paper presents a continuation of the program on porous media heat-transfer and flow-friction behavior previously covered in References [2b] and [3b]. All the previous results of interest to the designer on woven-screen matrices and crossed-rod matrices of a random configuration are summarized here. In addition, new design results for the regular in-line and regular staggered crossed-rod-matrix configurations are reported. Matrices of the type considered here may find application as heat-transfer surface geometries for nuclear-reactor fuel elements, for electrical resistance heaters and for periodic-flow-type heat exchangers used for gas-turbine regenerators, and some air-conditioning applications.
On Combined Free and Forced Convection in Channels
Authors: Tao L. N.
Published: February 2012

The heat-transfer problems of combined free and forced convection by a fully developed laminar flow in a vertical channel of constant axial wall temperature gradient with or without heat generations are approached by a new method. By introducing a complex function which is directly related to the velocity and temperature fields, the coupled momentum and energy equations are readily combinable to a Helmholtz wave equation in the complex domain. This greatly reduces the complexities of the problems. For illustrations, the cases of flows between parallel plates and in a rectangular channel are treated. It shows that this method is more direct and powerful than those of previous investigations.
Sublimation Mass Transfer Through Compressible Boundary Layers on a Flat Plate
Authors: Sherwood T. K. , Tra¨ss Olev
Published: February 2012

Data are reported on rates of sublimation mass transfer from an adiabatic, sharp-edged flat plate exposed to air streams at Mach numbers of 0.43, 2.0, and 3.5. Thickness decrease of the subliming naphthalene coating, plate surface temperature, and flow conditions were measured. An analysis of friction and heat transfer in turbulent compressible flow has been extended to mass transfer at low rates. Agreement between theory and data is good over the entire range of Reynolds numbers from 3 × 104 to 9 × 106. The effect of compressibility on mass transfer is found to be slightly greater than on friction. The measurement of the sublimation rate of thin coatings of solids provides a powerful technique of obtaining local friction coefficients, being simpler and of a wider applicability than the method involving force measurements on small floating surface elements.
An Experimental Study of the Effects of Nonuniform Wall Temperature on Heat Transfer in Laminar and Turbulent Axisymmetric Flow Along a Cylinder
Authors: Eichhorn R. , Eckert E. R. G. , Anderson A. D.
Published: February 2012

Measurements of both the hydrodynamic and thermal characteristics of flow over an axial cylinder at subsonic speeds are reported. It was found that the boundary layer along an axial cylinder tends to become asymmetrical as it approaches the transition point. This asymmetry vanishes again in turbulent flow. For both laminar and turbulent flow, the average boundary-layer growth could be predicted by the standard flat-plate relationships, and simple methods were deduced for determining the effective hydrodynamic length of the boundary layers. Local and total heat-transfer measurements were made with both laminar and turbulent flow for various unheated starting lengths followed by linearly increasing wall temperatures. For laminar flow, agreement with theory was obtained, this agreement being improved by the Seban and Bond cylindrical curvature correction. The turbulent-flow results indicated preference for the theory of Seban. Isothermal equations represent turbulent heat transfer within approximately 20 per cent when the wall-temperature variations are not too abrupt.
A Survey of P-V-T Data for Water in the Critical Region
Authors: Nowak E. S. , Grosh R. J. , Liley P. E.
Published: February 2012

A comprehensive review is given of P-V-T data available for water at pressures from 2700 to 4000 psia, specific volumes from 0.025 to 0.125 cu ft per lb, and temperatures from about 680 to 800 deg F. Experimental and computed values of various investigations are given. A description of the various methods and formulas used to interpolate the original data is also given. The results indicate there is a lack of smoothed or computed values for the specific volumes of the superheated vapor at sufficiently close intervals in the critical region. This makes it difficult to interpolate accurately and derive such properties as density and coefficients of volume expansion and compressibility. Furthermore, there are significant differences between the data for superheated steam given in the various tables which can be attributed to erroneous methods of interpolating the original experimental data.
Experimental Determination of Limit of Supersaturation of Nitrogen Vapor Expanding in a Nozzle
Authors: Goglia Gennaro L. , Van Wylen Gordon J.
Published: February 2012

The limit line of supersaturation of slightly superheated nitrogen vapor as it expands in a two-dimensional nozzle has been determined. The results indicate that the degrees of supersaturation vary from 12.3 F at a condensation temperature of 109 R to 3.5 F at 126 R. These results are in agreement with work of other investigations with nitrogen gas initially at room temperature.
Transient Natural Convection From Vertical Elements
Authors: Gebhart B.
Published: February 2012

The transient natural-convection process is analyzed using an integral method of analysis. Differential equations are derived which relate average surface temperature and time for either heating or cooling for vertical elements having arbitrary thermal capacity. The equations are applicable to laminar flow for all fluids. The coefficients are Prandtl number dependent and are estimated for Prandtl numbers in the range 0.01 to 1000. A solution of the equations is presented for the extreme case of a vertical plate of negligible thermal capacity subjected to a step in flux at its surface. Fluids having Prandtl numbers of 0.01, 0.1, 0.72, 1.0, 5, 10, 100, and 1000 are considered. The results, in terms of generalized variables, are practically independent of Prandtl number. Simple one-dimensional transient behavior is followed for approximately 20 per cent of the transient with a subsequent quick approach to the asymptotic value. The results show no substantial overshoot of the average surface temperature. It is doubted that significant temperature overshoot actually occurs for vertical surfaces even for a step in flux.
Effect of Aspect Ratio and Tube Orientation on Free Convection Heat Transfer to Water and Mercury in Enclosed Circular Tubes
Authors: Larsen Floyd W. , Hartnett James P.
Published: February 2012

Free convection heat transfer to water and to mercury in a circular tube closed at the bottom end, open to a cooled reservoir at the top, and heated through the wall with a uniform heat flux, has been investigated with emphasis on the effect of length-to-radius ratio and tube inclination. Dimensionless wall and fluid temperatures are presented for several tube inclinations over a range of imposed dimensionless heat fluxes to a tube of length-to-radius ratio 14.6; these results are compared to earlier measurements in a tube of length-to-radius ratio 21.0. Over the range of the investigation the flow was apparently in fully mixed turbulent motion, as evidenced by the large fluid temperature fluctuations recorded during the tests. Inclination of the tube was found to result in a considerable decrease in temperature fluctuations and a corresponding increase in heat transfer above that observed with the tube axis vertical.
The Influence of Sound on Free Convection From a Horizontal Cylinder
Authors: Fand R. M. , Kaye J.
Published: February 2012

In a previous publication the authors described a new type of acoustic streaming, called thermoacoustic streaming, which occurs near a heated horizontal cylinder in the presence of horizontal transverse sound fields. In the present paper, quantitative experimental results are presented, which show that thermoacoustic streaming causes a marked increase in the coefficient of heat transfer from a heated cylinder; for a given temperature potential, the superposition of a sound field can increase the heat-transfer coefficient by a factor of 3, relative to the free-convection heat-transfer coefficient in the absence of sound. An empirical equation is provided by means of which the coefficient of heat transfer from a horizontal cylinder in the presence of horizontal transverse sound fields can be computed for many cases of practical interest.
Natural-Circulation Tests With Water at 800 to 2000 Psia Under Nonboiling, Local Boiling, and Bulk Boiling Conditions
Authors: Mendler O. J. , Rathbun A. S. , Van Huff N. E. , Weiss A.
Published: February 2012

Natural and forced-circulation test data for a closed-loop system are presented and analyzed. The data were obtained at pressures of 800, 1200, 1600, and 2000 psia from the natural-circulation loop at the Bettis Laboratory, using single rectangular channel test sections (0.100 in. × 1.0 in. × 27.0 in. long, 0.200 in. × 1.0 in. × 27.0 in. long, and 0.250 in. × 1.0 in. × 27.0 in. long). Heat fluxes ranged from 50,000 Btu/hr-sq ft to burnout with inlet subcoolings of 20, 70, and 100 deg F. The results showed that single and two-phase pressure drop, burnout heat flux, and riser density measured under natural-circulation operation are no different from those measured with forced circulation at the same thermal and fluid flow conditions. For the loop studied, it was shown that natural-circulation-loop flow rates can be predicted to within 10 per cent for both single and two-phase flow. Some data for slip ratios at liquid velocities less than 1/2 fps and for two-phase exit losses were obtained. Flow fluctuations were noted during some of the natural-circulation runs; these occurred before burnout heat flux was reached. In some instances these fluctuations were severe enough to cause a premature burnout.
Heat Transfer to Laminar Flow Across a Flat Plate With a Nonsteady Surface Temperature
Authors: Cess R. D.
Published: February 2012

Forced convection heat transfer is considered for laminar flow across a flat plate whose surface temperature varies with time. The case analyzed first is that of a step change in surface temperature, and series solutions are obtained which apply for both small and large time. These series results are used to construct an approximate solution which describes the entire time-history of the nonsteady heat-transfer process, and it is found that the results agree closely with an envelope composed of pure transient conduction and steady-state convection solutions. The analysis is then generalized to include any prescribed variation of surface temperature with time.
Film Boiling in a Forced-Convection Boundary-Layer Flow
Authors: Cess R. D. , Sparrow E. M.
Published: February 2012

An analysis has been made to determine the heat transfer and friction characteristics in forced-convection film boiling on a flat plate. It is shown that the resulting two-phase flow problem can be formulated exactly within the framework of laminar boundary-layer theory. Solutions covering the parameter range of practical interest have been obtained by a combination analytical-numerical method. Heat-transfer and skin-friction results are presented both graphically and as simple, closed form analytical expressions. Relative to the case of pure liquid flow, the skin friction is substantially reduced due to film boiling. The heat transfer is found to increase as (ΔT)1/2, a much smaller dependence than in other convection phenomena.
On Some Laminar Forced-Convection Problems
Authors: Tao L. N.
Published: February 2012

The forced-connection problems in channels of fully developed laminar flow with heat sources and constant wall-temperature gradient are approached by the method of complex variables. It is shown that the stated problems are reduced to the determination of some analytic functions which satisfy the boundary conditions. Few basic problems, including flows in equilateral triangular ducts and in elliptical tubes, are studied. Also, it is shown that the cases of circular tubes and of parallel plates with a gap are directly deducible from that of elliptical tubes. All these solutions are expressed in closed forms by polynomials.
Local Mass Transfer From Circular Cylinders in Cross Flow
Authors: Sogin H. H. , Subramanian V. S.
Published: February 2012

This is an investigation of the distribution of the local rate of mass transfer from 4.2-in-diam naphthalene cylinders to air at ordinary temperature and pressure, flowing normal to the axis. The air speeds are near and within the critical zone of the drag. The results in the laminar region are compared with approximate boundary-layer calculations of H. Schuh and of H. J. Merk and with corresponding heat and mass-transfer experimentation in the literature. It is shown that the calculations after Merk are reliable from the point of stagnation to the predicted point of separation.
Heat Conduction in an Eccentrically Hollow, Infinitely Long Cylinder With Internal Heat Generation
Authors: El-Saden M. R.
Published: February 2012

This paper discusses the steady temperature distribution in an infinitely long, eccentrically hollow cylinder with uniform rate of internal heat generation. An exact theoretical solution is presented. The result is applied to the special case of no internal heat generation, and the rate of heat conduction is obtained.
Thermal Radiation Characteristics of Cylindrical Enclosures
Authors: Sparrow E. M. , Albers L. U. , Eckert E. R. G.
Published: February 2012

Consideration is given to the radiant interchange within finite-length cylindrical holes, one end of which is open to the environment. The bounding surfaces of the hole are isothermal and radiate in a gray, diffuse manner. The problem is analyzed by applying radiant flux balances to infinitesimal elements of surface, and this gives rise to two simultaneous integral equations. The solutions to these provide such technically interesting results as the distribution of the apparent emissivity and local heat flux along the bounding surfaces and, also, the over-all heat flux streaming from the hole. It is found, for example, that to achieve an apparent emissivity of 0.99, the minimum length of hole is 1.6, 2.6, or 4 diameters depending on whether the surface emissivity ε is 0.9, 0.75, or 0.5. The over-all heat loss results demonstrate the effect of the presence of pits and depressions in increasing the heat loss from a surface.
A Comparison of Predicted and Measured Friction Factors for Turbulent Flow Through Rectangular Ducts
Authors: Hartnett J. P. , Koh J. C. Y. , McComas S. T.
Published: February 2012

The friction coefficient for both laminar and turbulent flow through rectangular channels was analytically and experimentally studied. The analytic expression for the pressure loss in fully established laminar flow was verified by experiment. In turbulent flow, the method of Deissler and Taylor was used to calculate the friction coefficient. The calculated and measured results were in agreement for ducts having large aspect ratios. At aspect ratios less than 5:1, the predicted values of the friction factors were lower than the experimental data, with a maximum difference of 12 per cent evident for the square duct. It was found that the circular-tube correlation accurately predicts the friction coefficient for flow through rectangular ducts of any aspect ratio for Reynolds numbers between 6 × 103 and 5 × 105. Hydrodynamic entrance-length results are also presented in the laminar and turbulent flow ranges for both a smooth and an abrupt entrance configuration.
Heat Transfer for Pulsating Laminar Duct Flow
Authors: Siegel R. , Perlmutter M.
Published: February 2012

Heat-transfer solutions have been obtained for pulsating laminar flow between parallel plates. The pulsations are caused by superposing an oscillating pressure gradient on the steady driving pressure of the flow. Two types of heat-transfer boundary conditions are considered: (a) The channel walls are at constant temperature; or (b) a specified uniform heat flux is transferred at the walls. The heat-transfer behavior is obtained along the entire length of the channel, that is, in both the thermal entrance and fully developed regions. The temperature distributions are two-dimensional, but a slug flow (one-dimensional) assumption is used to simplify the velocity distribution. The results are compared with those obtained using a quasi-steady assumption.
The Effect of Subcooled Liquid on Laminar Film Boiling
Authors: Sparrow E. M. , Cess R. D.
Published: February 2012

Heat-transfer results for film boiling in the presence of a subcooled liquid have been determined analytically for the case of the isothermal vertical plate. The two-phase flow and heat-transfer problem which arises has been formulated exactly within the framework of boundary-layer theory, and free convection within the liquid has been accounted for. At a fixed temperature difference between surface and saturation, the effect of subcooling is to increase the heat transfer from the plate surface, with the magnitude of the increase being controlled by five physical parameters. Graphical presentation of the heat-transfer results is made for parametric values which correspond to water, but this information may be applied to other fluids having similar parameter ranges. For large subcooling, the heat transfer is essentially equal to that for pure free convection (no boiling), and the limits for this condition are given.
Laminar Flow Heat Transfer for Variable Physical Properties
Authors: Koppel L. B. , Smith J. M.
Published: February 2012

A solution is presented for heat transfer from a circular tube to a fluid, with variable properties, in fully developed laminar flow within the tube. The major assumption employed is that the radial velocity component may be neglected. The method is illustrated for supercritical carbon dioxide with the boundary condition of constant wall heat flux. Under these conditions the density and thermal properties vary greatly with temperature. The results indicate that unusual behavior of the heat-transfer coefficient may occur for certain values of heat flux and fluid temperature. The new solution technique presented should be applicable to a variety of partial differential equations with variable coefficients.
Heat Transfer From Partially Ionized Gases in the Presence of an Axial Magnetic Field
Authors: Raelson V. J. , Dickerman P. J.
Published: February 2012

This work was performed in order to investigate the influence of an axial magnetic field on the flow properties and heat-transfer characteristics of a partially ionized gas in a cylindrical flow channel. A description of the plasma generator and test channel is given along with experimental results for heat-transfer measurements at the channel wall and flow conditions within the channel as a function of field strength. Data obtained show a heat-flux reduction to the walls of the order of 20 per cent for a field strength of 20 kilogauss with indications that the interaction is limited to the boundary-layer region.
Thermoelectric Generators With Surface Heat Loss
Authors: Nottage H. B. , Starrett P. S. , Winskell P. L.
Published: February 2012

The influence of surface heat loss is treated analytically for unidimensional thermoelectric energy converters. Also, conditions are formulated whereby a gain in thermoelectric generator system efficiency can result from the transfer of heat from the thermoelectric conductors to a convecting fluid. While the general problem of the temperature distribution along the unidimensional conductor is described by a nonlinear differential equation, practical utility is demonstrated for linearization by assuring constant Thomson coefficient and mean-temperature properties within the range of most contemporary thermoelectric materials and applications. Influences of surface heat loss are discussed and demonstrated upon the longitudinal temperature distribution and the source and sink heat conduction rates.
Transient Pool Boiling of Water on a Vertical Surface With a Step in Heat Generation
Authors: Lurie Henry , Johnson H. A.
Published: February 2012

This paper is based on the PhD thesis investigation by H. Lurie [1] on the transient heat transfer from a vertical submerged metallic ribbon undergoing a step in Joule heating leading to boiling on its surface. The tests were made in deaerated distilled water at atmospheric pressure with pool temperatures at saturation and 112 deg F subcooled, and with heat generation rates per unit of ribbon surface area from nonboiling to 1.6 × 106 Btu/ft2hr. Although the heat capacity of the ribbon is low, the surface temperature overshoot compared to the steady-state temperature is minor with values of less than 10 deg F. The time required to reach this overshoot, or the time required to reach steady state, is very short and decreases with increasing heat flux. These values are short compared to Goldstein and Eckert [2] and Siegel’s [3] estimates of the time required to develop the hydro-dynamic and thermal boundary layers in natural convection, and indicate that nucleate boiling heat transfer is probably a weak function of the fluid circulation. Some further support for this is evidenced by calculated transient temperatures based on steady nucleate boiling heat transfer which are in reasonable agreement with the measured performance.
The Local Heat-Transfer Coefficient Around a Heated Horizontal Cylinder in an Intense Sound Field
Authors: Fand R. M. , Roos J. , Cheng P. , Kaye J.
Published: February 2012

In order to achieve a better understanding of the physical mechanism of interaction between free convection and sound, an experimental investigation of the local heat-transfer coefficient around the circumference of a heated horizontal cylinder, both in the presence and absence of a strong stationary sound field, has been carried out. The results show that superposition of intense sound upon the free-convection temperature-velocity field about a heated horizontal cylinder increases the heat-transfer coefficient both on the under and upper portions of the cylinder’s surface. In the presence of a sound field for which SPL = 146 db (re 0.0002 microbar) and f = 1500 cps, the maximum measured increases in the local heat-transfer coefficient on the under and upper portions of a 3/4-in-diam cylinder—relative to the free convection case at the same temperature potential—were found to be approximately 250 and 1200 per cent, respectively. A comparison of these results with earlier flow-visualization studies indicates that the relatively large percentage increase in the heat-transfer coefficient on the upper portion of the cylinder is caused by the oscillating vortex flow which is characteristic of thermoacoustic streaming. The reasons for the increase in the heat-transfer coefficient on the lower portion of the cylinder appear to be: (a) An increase in laminar boundary-layer velocities (steady components) in this region; and (b) modification of the boundary-layer temperature profile due to acoustically induced oscillations (unsteady components) within the laminar boundary layer. The experimental data presented can be used to check the validity of future analytical investigations of thermoacoustic phenomena.
A Comparison of the Influence of Mechanical and Acoustical Vibrations on Free Convections From a Horizontal Cylinder
Authors: Fand R. M. , Peebles E. M.
Published: February 2012

This technical brief reports the results of an experimental investigation of the influence of horizontal transverse mechanical vibrations (frequency order of magnitude: 100 cps) upon the rate of convective heat transfer from a horizontal cylinder. The results of the experiments are compared with earlier findings. It is shown that, in spite of a tenfold difference in frequency (and amplitude), the heat-transfer correlations previously obtained for the case of horizontal acoustical vibrations [1] are also valid for horizontal mechanical vibrations, and that the character of the boundary-layer flow is the same (thermoacoustic streaming [2]) for these two cases.
Diffusion and Chemical Surface Catalysis in a Low-Temperature Plasmajet: The Determination of Atom Concentrations in Nonequilibrium Supersonic Streams of Activated Nitrogen
Authors: Rosner Daniel E.
Published: February 2012

Chemical and thermal methods have been used to estimate the free atom concentration in a nonequilibrium supersonic jet of activated nitrogen emerging from a direct-current, high pressure, glow discharge. Emphasis is given to differential catalytic probe techniques, several variations of which are discussed. For nonequilibrium dissociated streams of low stagnation enthalpy, a differential catalytic thermometer is described which, in principle, offers the advantages of: (a) Linearity of probe response; (b) sensitivity independent of catalyst activity, details of gas dynamic environment, and catalyst geometry. A simple thermometric probe has been constructed and its output has been studied over a small range of electrical power dissipation. Evidence is given in support of the view that the probe responds principally to the same component of activated nitrogen that is depleted by chemical reaction with ethylene and propylene. Both catalytic probe measurements and the limiting amount of hydrogen cyanide production yielded about the same atom concentration (mole fractions of about 2 per cent). For electrical discharges operating at higher power densities, radiation losses from the catalytic thermometer surfaces necessitate design compromises which reduce the potential accuracy of the thermometric technique applied herein. This difficulty can be circumvented by using cooled catalytic probes (calorimeters), one type of which is currently under investigation. In general, it appears that the aerodynamic uncertainties involved in the catalytic probe theories presented are minor compared to the physicochemical questions raised by the use of such probes in nonequilibrium environments. Particular attention must be devoted to the role of excited species (other than ground state atoms) on the accuracy of both differential thermal detectors and chemical reactivity methods of analysis.