bluuebunny/crossref_metadata_2025 huggingface dataset:
The Calculation of Turbulent Boundary Layers on Spinning and Curved Surfaces
Authors: Launder B. E. , Priddin C. H. , Sharma B. I.
Published: November 2010

The development of turbulent shear layers on rotating or curved surfaces is usually characterized by strong effects of streamline curvature on the turbulence structure. The present contribution deals with the calculation of these effects with a model of turbulence which solves transport equations for the turbulence kinetic energy and its local rate of dissipation. The direct effect of curvature in the model is limited to a single empirical coefficient whose magnitude is directly proportional to a Richardson number based on a time scale of the energy-containing eddies. (In the absence of significant streamline curvature the model reduces to a form that has earlier been extensively tested in various thin shear flows.) Finite difference computations are reported of the following turbulent flows: the boundary layer on concave and convex surfaces; fully developed flow in a curved channel; axisymmetric flow over a spinning cylinder; and heat and mass transfer due to spinning cones of various vertex angles. Agreement with experiment is satisfactorily close in all these cases.
An Initial Approach to the Design of Very Wide Angle Axisymmetric Diffusers With Gauzes to Achieve Uniform Outlet Velocity Profiles
Authors: Kachhara N. L. , Livesey J. L. , Wilcox P. L.
Published: November 2010

A method is presented of designing very wide angle axisymmetric diffusing ducts which achieve uniform outlet velocity profiles. The aim was to concentrate the major part of the diffuser pressure rise on a small portion of the duct boundary with zero or favorable pressure gradients on the remainder of the boundary. With an optimum location and design of gauze the diffusers are capable of giving a very uniform outlet velocity profile in a short overall length, when working with thin inlet boundary layers and some, although recognizably moderate, pressure recovery. One diffuser tested (diffuser C) produced uniform outlet velocity profiles in approximately 1.5 inlet diameters compared with the 10 diameters required for a sudden enlargement having comparable performance.
Conditions for a Pipe to Run Full When Discharging Liquid Into a Space Filled With Gas
Authors: Wallis G. B. , Crowley C. J. , Hagi Y.
Published: November 2010

Experiments were performed with water discharging into air from horizontal and vertical tubes of several diameters. The horizontal tubes discharged into a variable space between vertical plates. The effects of length/diameter ratio and the shape of the end of the tube were investigated for the case of vertical tubes. In each case the conditions for the pipes to run full were associated with the formation and washout of large gas bubbles resembling those occurring in the slug flow regime of two-phase flow. The data for horizontal tubes were successfully correlated with some simple limiting theories and dimensionless representations. The vertical tube results were influenced by stability phenomena and nonsymmetrical flow patterns; as a result only a partial understanding was obtained.
Vortex Excited Oscillations of Yawed Circular Cylinders
Authors: King R.
Published: November 2010

Yawed cylinders are cylinders inclined forward or backwards in the plane of the flowing fluid. They are used in many practical situations such as braced frame members and raked marine piles. This paper describes an examination of three aspects of the yawed cylinder-fluid interactions over a range of yaw angles ±45° from the vertical for the Reynolds number range 2,000 < Re < 20,000. viz. 1. Establishment of the stability criteria of vortex-excited oscillations. 2. Measurement of ‘steady’ drag forces and equivalent drag coefficients. 3. Visualization of the local flow over stationary and oscillating cylinder. After a brief review of previous experimental and theoretical work, the results of the three items listed above are presented and discussed. Vortex-excited oscillations were recorded in the in-line and crossflow directions throughout the range of yaw angles and the results of items 2, 3 were used to justify the forms of the stability criteria proposed for these oscillations.
A Brief Review of Flow Induced Vibrations of Tube Arrays in Cross-Flow
Authors: Savkar S. D.
Published: November 2010

A brief review summarizing the key conclusions arrived at in a more extensive survey presented by the author to the 1976 ASME Winter Annual Meeting [1] is offered. In particular, an empirical stability map for tube arrays in cross-flow is suggested.
A Note on the Phase Relationships Involved in the Whirling
Instability in Tube Arrays
Authors: Savkar S. D.
Published: November 2010

The quasi-steady, displacement dependent, whirling instability model of Connors [1] and Blevins [2] is re-examined to clarify the phase relationships involved. In particular, conditions required for the oscillations to occur at a given frequency are clearly established.
Laminar Incompressible Recirculating Flow in a Driven Cavity of Polar
Cross Section
Authors: Ghia U. , Goyal R. K.
Published: November 2010

The driven flow in a polar cavity has been analyzed using the complete Navier-Stokes equations formulated in terms of a stream function and vorticity. An alternating-direction implicit method, with careful treatment of the convective terms in the equations, is used to obtain the numerical solutions. Results are obtained for the stream function, vorticity, velocities and pressure for various values of the two characteristic parameters of the problem, namely, the flow Reynolds number Re and the aspect ratio of the cavity. The formulation is general and produces results for the driven rectangular cavity-flow problem as a special case. Good agreement is obtained between the present solutions for this case and available corresponding results. The overall features of the driven polar-cavity flow are found to be generally similar to those for the rectangular cavity.
Heat Transfer From the Wall of a Porous Solid Involving Gas Injection and Vaporization
Authors: Frea W. J. , Hamelink J. H.
Published: November 2010

An experimental study was made of heat transfer with gas injection through a porous wall into a pool of liquid, including vaporization effects. Air bubbling from the surface of a graphite cylinder into water at atmospheric pressure was used. It was possible to determine limits on energy transfer due to convection and to latent heat transport. It was found that under some conditions it was possible to operate the system with the surface rejecting heat while at temperatures less than that of the bulk pool liquid.
Nongray Radiative Transport in a Cylindrical Medium
Authors: Habib I. S. , Greif R.
Published: November 2010

The problem of determining the radiative transport in a nongray cylindrical medium is considered. Nongray effects are included through use of the total band absorptance. Exact and approximate formulations and results are presented and very good agreement is obtained.
New Analytical Approach to the Evaluation of Configuration Factors in Radiation From Spheres and Infinitely Long Cylinders
Authors: Feingold A. , Gupta K. G.
Published: November 2010

It is shown in this paper that, in the case of radiation from spheres and infinitely long cylinders to a certain class of surfaces, the configuration factors are independent of the validity of Lambert’s cosine law. A new technique has been developed to calculate the configuration factors in radiation from spheres and infinitely long cylinders and, with this technique, formulas have been obtained for several geometries for which no solutions have previously appeared in the literature.
Heat Transfer by Thermal Radiation and Laminar Forced Convection to an Absorbing Fluid in the Entry Region of a Pipe
Authors: Pearce B. E. , Emery A. F.
Published: November 2010

The heat transferred to an absorbing fluid by coupled thermal radiation and laminar forced convection is computed for the entrance region of a tube with circular cross section. The tube wall is black and isothermal and the fluid enters with either a fully developed (parabolic) or uniform axial velocity distribution. Both gray and approximately nongray absorption are considered with the nongray absorption specified by the “box model” which approximates the spectral absorption of a vibration-rotation band in a molecular gas by an absorption coefficient which is a constant within an effective bandwidth and zero elsewhere. The box model is applied to carbon monoxide and to carbon dioxide and the calculations additionally include the effects of variable transport properties and variable density. It is shown that for the range of parameters considered in this paper the effect of the absorbed radiation is to increase the heat transfer near the entrance by as much as a factor of four and to decrease the thermal entry length by a factor of ten. The effects of radiation are shown to be more important when the fluid is heated than when it is cooled. By comparing the solutions for a gray fluid with constant properties with those using the box model of the absorption it is demonstrated that the gray approximation is not quantitatively accurate. Approximate solutions are investigated and it is shown that when the radiation-convection interaction is weak the radiation heat flux can be computed approximately by ignoring the interaction and using the known forced convection temperature solution. When the interaction is intense, both the coupling of the radiation and convection and also the spectral absorption must be accounted for in calculating the heat transfer. The box model is shown to be an acceptable method for specifying the approximate spectral absorption coefficient in nonisothermal gases.
Emittance of Oxide Layers on a Metal Substrate
Authors: Brannon R. R. , Goldstein R. J.
Published: November 2010

The variation of total normal emittance as a function of oxide thickness on a metal sub strate is investigated experimentally for Al-Al2O3 and Cu-CuO systems. The measurements are made using a comparative black-body technique. Over the range of aluminumoxide thicknesses investigated (1.2μ–86.4μ) the total normal emittance varies from 0.15–0.92 for a sample temperature of 96 deg C. With a copper-oxide thickness range from 1.2μ–5.6μ, the total normal emittance varies from 0.09–0.81 at 96 deg C. An analytical solution to the foregoing problem is formulated and the total normal emittance of the anodized aluminum samples is computed. Although the theoretical values are lower than the measured values, the effect of increasing oxide thickness on emittance is similar.
Instantaneous Measurement of Heat Transfer From an Oscillating Wire in Free Convection
Authors: Thrasher B. H. , Schaetzle W. J.
Published: November 2010

The instantaneous heat transfer properties are measured as a function of time for an oscillating wire (20 to 40 Hz) in still air. The wire is oscillated by thermal contractions and expansions which match the natural frequency based on wire mass and tension. The temperature variation results from the internal resistance heating of an alternating current. The wire temperature and velocity are measured as a function of time by photocells. This eliminates any instrumentation interference with the heat transfer. The results are plotted as a function of instantaneous and average Reynolds’ number. The oscillatory heat transfer data are divided into two regimes of free and forced convection by the critical Reynolds number. Oscillatory heat transfer rates are smaller for forced convection and greater for free convection than those for steady state conditions recommended by McAdams [2] for the respective regimes. No significant difference is found in the heat transfer for oscillations in the vertical and horizontal planes. Due to the time variation of the variables an appreciable amount of emphasis is placed on the experimental apparatus and the recording of data. The recorded data is basically corrected by assuming first order linear systems.
Condensation of Freon-114 in the Presence of a Strong Nonuniform, Alternating Electric Field
Authors: Holmes R. E. , Chapman A. J.
Published: November 2010

The condensation of Freon-114 in the presence of a nonuniform, alternating, 60-cycle, electric field was examined experimentally. The condensing surface was a grounded, cooled flat plate, and the electric field was produced by applying a voltage to a second plate placed above the first. Voltages up to 60 kv were imposed, and nonuniformities in the field were created by varying the angle between the plates. Analytical predictions were made of the expected heat-transfer rate, and reasonable agreement with the experimental data was obtained for voltages less than 40 kv. Above 40 kv the results were unpredictable, but increases in the heat-transfer coefficient as high as ten times that for no field were obtained.
Constant Temperature at the Surface of an Initially Uniform Temperature, Variable Conductivity Half Space
Authors: Cooper Leonard Y.
Published: November 2010

The transient temperature distribution resulting from a constant and uniform temperature being imposed on the surface of an initially uniform temperature, variable conductivity half space is studied. Various solution expansion ideas are discussed. These are utilized in the solution of an example problem, and the resulting approximate analytic solutions representations are compared to exact numerical results. One of these approximations is found to be superior to the others, and, in fact, it is shown to yield useful results over a range of variables where the nonlinearities of the problem are significant.
Heat Transfer Due to Combined Free and Forced Convection in a Horizontal and Isothermal Tube
Authors: Depew C. A. , August S. E.
Published: November 2010

The influence of natural convection due to buoyancy has been studied both experimentally and analytically for many cases, but the existing correlations are not accurate for horizontal, isothermal tube flow when the heated length is relatively short. The research reported in this paper was undertaken to alleviate this shortcoming by deriving a correlation to include new experimental data on a tube with L/D = 28.4. The experimental data from this and other investigations represents a variety of fluids, heating and cooling, and various apparatus and conditions. The equation which correlates the present and previous data to within ±40 percent is Nuaμwμb0.14=1.75[Gz+0.12(GzGr1/3Pr0.36)0.88]1/3
Turbulent Boundary Layer and Heat Transfer Measurements Along a Convergent-Divergent Nozzle
Authors: Back L. H. , Cuffel R. F.
Published: November 2010

Boundary layer and heat transfer measurements are presented along a cooled, conical nozzle with a convergent and a divergent half-angle of 10 deg. Semi-empirical analyses are considered in conjunction with the measurements. The heat transfer is found to be describable by using the integral form of the energy equation once the relationship between the Stanton number and energy thickness Reynolds number has been established from the measurements. The friction coefficient, however, is not described accurately along the entire nozzle by existing formulations considered.
On Acoustic Propagation and Critical Mass Flux in Two-Phase Flow
Authors: D’Arcy D. F.
Published: November 2010

Theoretical values for the propagation speed of small pressure disturbances through two-phase fluid have been derived by a method analogous to the well-known method for single-phase fluids and using the well-known separated-flow model of two-phase flow. Since the liquid and vapor phases in general flow at different mean speeds, it is appropriate to compute the propagation speed relative to the laboratory frame of reference, not relative to the fluid as is usually done in single phase. With the extra degree of freedom in two-phase flow, two distinct speeds are found for propagation both upstream and downstream, each representing compatible thermodynamic behavior of both phases. Comparisons between calculations based on the model, and several published sets of experimental values of the speed of sound, tend to confirm the theory at low and at high void fractions. Both propagation speeds have been observed in experiments. Also by analogy with the single-phase case, critical flow is predicted to occur when the upstream propagation speed relative to the laboratory is zero, i.e., when pressure waves cannot travel into the opening from which the flow issues. Flow calculations based on the model under these conditions show agreement with published experimental critical-flow measurements in the regions of low and high void fractions. Thus, a satisfactory explanation of the critical-flow phenomenon in two-phase fluids is obtained in these regions. From the analytical–experimental comparisons it appears that of the two propagation speeds and critical flows, one is observed at low void fraction, and the other at high void fraction. In the intermediate range, the theory and experiment differ and it is probable that the separated-flow model does not adequately represent the flow regimes occurring in this range.
The Influence of Electric Fields on Convective Heat and Mass Transfer from a Horizontal Surface under Forced Convection
Authors: Sadek S. E. , Fax R. G. , Hurwitz M.
Published: November 2010

This paper presents the results of an investigation of the electrohydrodynamic augmentation of drying under forced convection. Heat and mass transfer coefficients were calculated from the drying rates of sponges, using the analogy between heat and mass transfer. The test setup used was a flat plate with tangential air flow. Electrical forces, used to disturb the boundary layer, were applied by placing a high-voltage electrode above the sponge which was maintained at ground potential. Augmented heat and mass transfer coefficients were correlated to nondimensional terms developed from similarity and modeling principles.
Developing Flow with Combined Forced–Free Convection in an Isothermal Vertical Tube
Authors: Zeldin B. , Schmidt F. W.
Published: November 2010

The influence of gravity on developing forced, laminar flow in a vertical isothermal tube was investigated by means of a numerical analysis and an associated experiment. Numerically predicted velocity profiles and Nusselt numbers for combined forced–free convection with Gr/Re = −30 are compared with their counterparts for pure forced convection, Gr/Re = 0, for air with Re = 500. The analysis was performed for both the uniform irrotational and the fully developed velocity entrance models. Velocity profiles were measured in a vertical-tube apparatus designed to provide an approximately uniform entrance velocity using air as the test fluid. These are compared with numerical predictions based on test conditions.
An Experimental and Analytical Study of Radiative and Conductive Heat Transfer in Molten Glass
Authors: Eryou N. D. , Glicksman L. R.
Published: November 2010

One-dimensional temperature profiles and heat fluxes within a slab of molten glass were measured experimentally. The glass slab was contained between two parallel platinum-lined ceramic plates. The plate temperatures were kept above 2000 deg F so that radiation heat flux was always equal to or larger than conduction. An optical method of temperature measurement was developed in which a helium–neon laser beam was directed along an isothermal path through the glass. The attenuation of the beam was a strong function of temperature and was used to evaluate the local temperatures within the glass slab. In order to perform a theoretical analysis the spectral absorption coefficient of the glass was measured from 2000 to 2300 deg F. Two analyses were performed: one for a diffuse platinum–glass boundary and the other for a specular boundary. The calculated temperatures agree with the measured values within 5 deg F throughout the slab, and the measured and predicted heat fluxes agree within 10 percent.
Effect of Wall Conduction on the Stability of a Fluid in a Rectangular Region Heated from Below
Authors: Catton Ivan
Published: November 2010

The initiation of natural convection in a fluid confined above and below by rigid, perfectly conducting surfaces and laterally by vertical walls of arbitrary thermal conductivity which form a rectangle is examined. The linearized perturbation equations are obtained in the usual manner and reduced to an eigenvalue problem. The Rayleigh number is the eigenvalue and is a function of the lateral-wall conductance and horizontal plan form (aspect ratios). The problem associated with satisfying the no-slip boundary conditions on all surfaces is surmounted by using the Galerkin method. Results are compared with experiments and shown to be in good agreement.
Heat Transfer and Forces on Concave Surfaces in a Free Molecular Flow
Authors: Fan Chien
Published: November 2010

A Monte Carlo modeling technique is described for mathematically simulating free molecular flows over a concave spherical surface and a concave cylindrical surface of finite length. The half-angle of the surfaces may vary from 0 to 90 deg, and the incident flow may have an arbitrary speed ratio and an arbitrary angle of attack. Partial diffuse reflection and imperfect energy accommodation for molecules colliding with the surfaces are also considered. Results of heat transfer, drag, and lift coefficients are presented for a variety of flow conditions. The present Monte Carlo results are shown to be in very good agreement with certain available theoretical solutions.
Perturbation Solutions for Spherical Solidification of Saturated Liquids
Authors: Pedroso R. I. , Domoto G. A.
Published: November 2010

A perturbation solution is obtained for outward and partial inward spherical solidification of a liquid initially at the freezing temperature. The constant-wall-temperature boundary condition is considered with the properties of the solidified material assumed as constants. A nonlinear transformation is applied to the sequence of partial sums in the perturbation solution to increase its range of applicability. For inward solidification it is found that the regular perturbation solution diverges for front positions close to the center. An Euler transformation and an overall energy balance are then used to obtain a modified series solution which is compared with numerical results.
Convective Instability in the Thermal Entrance Region of a Horizontal Parallel-Plate Channel Heated from Below
Authors: Hwang G. J. , Cheng K. C.
Published: November 2010

An investigation is carried out to determine the conditions marking the onset of longitudinal vortex rolls due to buoyant forces in the thermal entrance region of a horizontal parallel-plate channel where the lower plate is heated isothermally and the upper plate is cooled isothermally. Axial heat conduction is included in an analytical solution for the Graetz problem with fully developed laminar velocity profile. Linear-stability theory based on Boussinesq approximation is employed in the derivation of perturbation equations. An iterative procedure using high-order finite-difference approximation is applied to solve the perturbation equations and a comparison is made against the conventional second-order approximation. It is found that for Pr ≥ 0.7 the flow is more stable in the thermal entrance region than in the fully developed region, but the situation is just opposite for small Prandtl number, say Pr ≤ 0.2. Graphical results for the critical Rayleigh numbers and the corresponding disturbance wavenumbers are presented for the case of Pe → ∞ with Prandtl number as a parameter and the case of air (Pr = 0.7) with Peclet number as a parameter in the range of dimensionless axial distance from the entrance between x = 0.001 and 4 × 10−1.
A Model for Eddy Conductivity and Turbulent Prandtl Number
Authors: Cebeci T.
Published: November 2010

This paper presents a model for eddy conductivity and turbulent Prandtl number based on the considerations of a Stokes-type flow. The expressions obtained by the model provide continuous velocity and temperature distributions for turbulent flows and are applicable to flows with pressure gradients, mass transfer, and heat transfer. Close to the wall the turbulent Prandtl number appears to be strongly affected by the molecular Prandtl number; away from the wall it is constant, that is, it is independent of the molecular Prandtl number. Calculated results agree well with experiments, including those with fluids having both low and high Prandtl numbers. In addition the results confirm recent experimental findings, in that the mass transfer has no effect on turbulent Prandtl number.
Thermal Model for Prediction of a Desert Iguana’s Daily and Seasonal Behavior
Authors: Beckman W. A. , Mitchell J. W. , Porter W. P.
Published: November 2010

A mathematical description of the transient thermal response of the desert iguana, Dipsosaurus dorsalis, to environmental changes is developed. The thermal model for the lizard was combined with a desert micrometeorological model, and the combination was used to predict diurnal and seasonal thermoregulatory behavior. Comparisons are made between the predictions and observed behavior. The model analysis is sufficiently general so that it can be used to predict the thermoregulatory behavior of other species of lizards.
Steady Two-Dimensional Heat and Mass Transfer in the Vapor-Gas Region of a Gas-Loaded Heat Pipe
Authors: Rohani A. R. , Tien C. L.
Published: November 2010

A numerical analysis is made of the steady two-dimensional heat and mass transfer in the vapor-gas region of a gas-loaded heat pipe. Consideration is given to a cylindrical heat pipe with typical evaporator, condenser, and noncondensible-gas sections and with negligible axial conduction through the wall and the liquid-wick matrix. The elliptical mass, momentum, energy, and species conservation equations have been solved in conjunction with the overall energy and mass conservation constraints and the thermodynamic equilibrium condition for three heat pipe cases with different working fluids and diameters. The results show that in certain gas-loaded heat pipes, such as liquid-metal heat pipes, vapor-gas diffusion and two-dimensionality must be considered in the analysis. Extension of the present numerical framework to more general cases such as including the axial wall conduction is indicated.
Heat Transfer in Non-Newtonian Flow Past a Wedge With Nonisothermal Surfaces
Authors: Chen J. L. S. , Radulovic P. T.
Published: November 2010

The steady heat transfer in the incompressible laminar boundary layer flow of power law fluids past a wedge having a step discontinuity in surface temperature is studied analytically. The solution method recently introduced by Chao and Cheema is extended to the present problem. The solution is obtained in terms of an infinite set of similar solutions which are expressible as universal functions. Tabulations of such functions are given. For most of the non-Newtonian fluids commonly encountered having large Prandtl numbers, only a very few terms of the functions are needed to yield accurate results.
Heat Transfer and Fragmentation During Molten-Metal/Water Interactions
Authors: Witte L. C. , Vyas T. J. , Gelabert A. A.
Published: November 2010

Molten metals, (mercury, lead, zinc, bismuth, tin, and aluminum) were quenched in water and liquid nitrogen. High-speed photographs provide insight into the fragmentation phenomenon. The key to the vapor explosion is the very rapid transfer of heat which requires substantial surface area: fragmentation provides this necessary surface area. Prior fragmentation theories are examined in light of these experiments and are found to be inadequate. This study indicates strongly that fragmentation occurs when a sample is molten and fragmentation is a response to an external stimulus. Alternate causes of fragmentation are proposed and are predicated upon the initial collapse of a vapor film around the molten metal. The data also show that energy required to form new surface area and to displace water during the fragmentation phenomenon is not significant when compared to the energy available in a molten sample.
Transport to a Rotating Disk in Turbulent Flow at High Prandtl or Schmidt Number
Authors: Paterson J. A. , Greif R.
Published: November 2010

The eddy viscosity distribution near the surface of a rotating disk is determined from an analysis of the basic conservation equations. The results are applied to the high Schmidt number problem and good agreement is obtained with experimental data for the mass flux.
Effect of a Heat Flux Spike on the Downstream Dryout Behavior
Authors: Groeneveld D. C.
Published: November 2010

The effect of a short hot patch on the downstream dryout behavior was investigated in heated tubes cooled by Freon-12 at conditions equivalent (on the basis of liquid to vapor density ratio) to 69 bar in steam-water. The hot patch, located well upstream from the heated end, generated a heat flux spike which resulted in a local dry patch. Following an increase in downstream surface heat flux the dry patch would often spread in the downstream direction even though the heat flux was only a small fraction of the measured critical heat flux with uniform heating. A force balance on the dry patch boundary showed that, for certain conditions, spreading of the dry patch in the downstream direction is inevitable. This spreading however can be limited by interfacial instability, droplet-wall interaction and axial conduction.
Laminar Film Condensation on Nonisothermal and Arbitrary-Heat-Flux Surfaces, and on Fins
Authors: Lienhard J. H. , Dhir V. K.
Published: November 2010

The class of two-dimensional laminar film condensation problems with variable wall-subcooling, for which the full boundary layer equations admit similar solutions, is identified. The solutions of this problem reveal the limitations of the simple Nusselt-Rohsenow method when it is employed to deal with nonisothermal wall problems. The Nusselt-Rohsenow method is used to treat a wide spectrum of variable wall termpeature problems, and results are compared with the exact solutions. Problems in which the heat flux is arbitrarily specified are considered. Variable wall termperature problems involving axisymmetric bodies and arbitrary variations of gravity are also included. Finally, condensation on fins of various configurations is also treated.
Temperature Field Due to a Time Dependent Heat Source of Spherical Geometry in an Infinite Medium
Authors: Balasubramaniam T. A. , Bowman H. F.
Published: November 2010

A solution is given for the heat conduction problem in which a sphere generating heat, at a rate which is proportional to time raised to the minus one-half power, is embedded in an infinite medium. The solution is of use in the thermistor probe technique for the determination of both the thermal conductivity and diffusivity of media which wet the surface of the thermistor. The thermistor bead is treated as a spherical distributed thermal mass and the coupled thermal response of the bead and the medium are presented. Typical temperature profiles both in the sphere and in the surrounding medium are presented.
Analysis of Cooling Effectiveness for Porous Material in a Coolant Passage
Authors: Koh J. C. Y. , Colony R.
Published: November 2010

An analytical investigation of the performance of a heat exchanger containing a conductive porous media was made. The partial differential equations governing the steady-state temperature distributions for both the porous media and the coolant fluid are given. A method for obtaining an approximate solution of the governing equations is shown. A computer program was written in FORTRAN IV and the results are provided for determining the cooling effectiveness.
Laminar Free Convection Over Two-Dimensional and Axisymmetric Bodies of Arbitrary Contour
Authors: Lin F. N. , Chao B. T.
Published: November 2010

A rapid computation procedure is described for the prediction of heat transfer in laminar free convection boundary layers, either two-dimensional or axisymmetrical, over isothermal smooth objects with fairly arbitrary shape. The analysis employs suitable coordinate transformation which makes it possible to express the solutions of the governing conservation equations in terms of a sequence of universal functions that depend on the fluid Prandtl number and a configuration function. The latter is completely determined by the body contour and its orientation relative to the body force that generates the motion. Several of the leading universal functions have been evaluated and tabulated. The theory was applied to a number of body configurations and the results compared well with published analytical and/or experimental information. Some new results are also obtained for the local Nusselt number over horizontal elliptical cylinders and ellipsoids or revolution.
Transient Electrical Heating of Toroidal Coils of Rectangular Cross Section
Authors: Cooper H. F. , Williams G. N.
Published: November 2010

The exact solution is obtained for the transient thermal response of toroidal coils of rectangular cross section with orthotropic constant thermal conductivity, constant density, and specific heat, and linear boundary conditions. The solution is a rapidly converging doubly infinite eigenfunction expansion whose leading term is generally accurate to within 5 percent. No conclusive results were obtained from our evaluation of the applicability of previously obtained solutions for the infinite rod approximation for the toroidal coils. In some cases, the infinite rod approximation is accurate even for large curvatures, but in other cases it is in substantial error for relatively small curvatures. Hence, the solution presented here is generally recommended to predict the temperature distribution in toroidal coils and a number of design curves are provided for prediction purposes.
Pseudosteady-State Natural Convection Inside Spheres
Authors: Chow M. Y. , Akins R. G.
Published: November 2010

Natural convection heat transfer to water contained within five different sized spheres was studied. Pseudosteady-state was maintained by keeping the driving force for convection constant, i.e., the temperature outside the sphere was increased steadily so that the temperature difference between the outside and the center remained constant. Flow visualization was used to determine flow patterns within the spheres. Laminar flow was found to exist below Rayleigh numbers of about 107. The flow patterns along with the position of the circulation centers are presented and compared with recent numerical solutions. The overall heat transfer in the laminar region was fitted by least squares and the following correlation obtained: Nu=0.80Ra0.30
New Method to Determine Latent Heat of Liquids by Means of Dielectric Data
Authors: Leidenfrost W.
Published: November 2010

A new method to determine heat of vaporization by means of dielectric data is described which allows one to obtain specific volumes introduced into Clausius-Clapeyron’s equation. Isochoric observations are not needed in most cases. An instrument is described for the observation of dielectric data, vapor pressure curve, p-T relationships in superheated state and also molecular weight and polarizability. The measurements to be performed are listed. The validity of the method is checked by using data observed in a similar instrument. The latent heat obtained by the new method is in excellent agreement with literature data. The new method, therefore, can be used advantageously to determine, in not too elaborate test equipment, latent heat, and other properties easily, quickly, and reliably.
Heat Transfer and Friction Loss Performance of Perforated Heat Exchanger Surfaces
Authors: Liang C. Y. , Yang Wen-Jei
Published: November 2010

A scale-up modeling technique has been developed to examine the effects of perforation geometry on the heat transfer and friction loss performance of compact heat exchangers having plate-perforated rectangular fin surfaces. The test cores, each consisting of a number of aluminum plates separated by wooden spacers to form parallel flow channels, were tested in a subsonic wind tunnel. The effects of the Reynolds number, plate surface porosity, core frontal porosity, and slot geometry on the heat transfer rate, friction loss, and noise intensity are determined. It is found that under certain circumstances plate perforation will produce significant improvement in heat transfer for the same pressure drop and pumping power. These studies are directed to the design of air-cooled condensers for Rankine cycle automotive engines, marine power propulsion systems, and the dry cooling towers of extra-high capacity electric power plants.
On the Influence of the Thickness and Thermal Properties of Heating Walls on the Heat Transfer Coefficients in Nucleate Pool Boiling
Authors: Magrini U. , Nannei E.
Published: November 2010

An experimental investigation was conducted under conditions of saturated pool boiling of water at atmospheric pressure on thin, horizontal, cylindrical walls of different metals and thicknesses, electrically heated. The heating walls, ranging in thickness from 5 to 250 μm, were obtained by plating copper, silver, zinc, nickel, and tin on nonmetallic rods. Experiments showed that the heat transfer coefficient can be affected, in particular conditions, by the heating wall thickness. In particular, it resulted that the smaller the thermal conductivity of the metal layer, the higher the influence of the thickness. A semiempirical correlation of the form ΔT = (q/A)nf(κd, √κρc) suitable to correlate the experimental data within ±15 percent in the whole range of variables here investigated is proposed.
Prediction of Local and Integral Turbulent Transport Properties for Liquid-Metal Heat Transfer in Equilateral Triangular Rod Arrays
Authors: Ramm H. , Johannsen K.
Published: November 2010

A theoretical method based on a phenomenological turbulence model has been applied to evaluate turbulent transport properties for liquid-metal heat transfer in bare equilateral triangular rod bundles. Results obtained for local distributions of thermal eddy diffusivity in the various directions are presented in terms of correlations. From a subsequent solution of the three-dimensional heat transfer problem between two characteristic interior subchannels under conditions characteristic for tracer-type mixing experiments, integral thermal mixing coefficients and thermal length scales have been evaluated. Results demonstrate that the basic concept of subchannel analysis treating molecular conduction and turbulent transport independently of each other tends to underestimate intersubchannel transport. The uncertainties which are involved in principal assumptions of the turbulence-model as well as in the available empirical results are discussed in some detail.
Frost Formation With Varying Environmental Parameters
Authors: Jones B. W. , Parker J. D.
Published: November 2010

In practical applications frost formation often takes place with varying environmental parameters (air velocity, temperature, and humidity). Most correlations that have been developed are for constant parameters. Since the frost formation process is dependent on both time and on the history of the frost layer, the correlations for constant environmental parameters will not work when the parameters vary. For this reason, a study was made to develop a method to predict frost formations with varying parameters. A theoretical model of frost growth based on molecular diffusion of water vapor at the frost surface and using energy and mass balances was developed. The model can incorporate varying environmental parameters. The model uses functions relating heat and mass transfer coefficients at the frost surface to the environmental parameters. The model was first tested and calibrated using data taken by previous investigators. A facility was then built to test the validity of the model for varying environmental parameters. Tests were made for changes in humidity and air velocity. The model showed good agreement with the basic trends observed for varying parameters. The qualitative results were generally within 25 percent of the predicted values for time periods up to 3 hr.
Transient Convective Heat Transfer During and After Gas Injection Into Containers
Authors: Means J. D. , Ulrich R. D.
Published: November 2010

This paper presents experimental data correlations for the spatially averaged convective heat transfer coefficient for thin-walled closed containers during and after gas injection. The different modes of heat transfer are identified, and correlations are presented for each. Correlations are presented for the injection period, post-top injection, post-bottom injection, post-tangential injection, post-radial injection, and post-ejection heat transfer for various tank geometries. Of special significance are the very high heat transfer rates that are shown to be present in some cases immediately after injection. Heat transfer rates are shown to be, for a short period, up to almost two orders of magnitude higher than natural convection predictions would indicate.
Transient Response of Straight Fins
Authors: Suryanarayana N. V.
Published: November 2010

The transient response of a fin of constant area of cross section and perimeter, with its end insulated, is analyzed using Laplace transforms. Solutions are developed for small and large values of times when the base is subjected to a step change in temperature or heat flux. Fins with base subjected to sinusoidal temperature or heat flux are also analyzed. Typical results are represented in graphical form.
A Study of Flow Stability in Helium Cooling Systems
Authors: Jones M. C. , Peterson R. G.
Published: November 2010

Methods have been developed for the computation of the frequency response and stability of helium cooling systems in the frequency range of the density wave instability. While more generally applicable, these methods were developed for a study of superconducting power transmission. Special features are the use of helium thermodynamic properties derived at every point from the exact equation of state, and the full accounting of the effect of compressibility. Classical linear control theory is employed throughout. By using a finite difference approach to the integration of the conservation equations over the space coordinate, the accuracy obtainable is limited only by the computation time available. Examples are given for representative transmission line parameters with the helium at a variety of supercritical pressures. It is concluded that, while density wave instability is a real potential problem in superconducting power transmission lines, it is not difficult to select operating parameters in a safe stable regime.
New Techniques for Measuring Film Cooling Effectiveness
Authors: Blair M. F. , Lander R. D.
Published: November 2010

Techniques to measure local film effectiveness distributions on large-scale models of turbine blade and vane sections were developed for use in subsonic, room-temperature wind-tunnel environments. Highly detailed film cooling effectiveness distributions were obtained on near-adiabatic, cast rigid foam test models using infrared radiometer scanning techniques. Sample results from both flat-plate film cooling studies and airfoil leading-edge film cooling studies are presented.
Turbulent Natural Convection on Upward and Downward Facing Inclined Constant Heat Flux Surfaces
Authors: Vliet G. C. , Ross D. C.
Published: November 2010

Local heat transfer data were obtained for turbulent natural convection on vertical and inclined upward and downward facing surfaces. The test surface consisted of a 1.83 m (6 ft) wide × 7.32 m (24 ft) high plate with a constant heat flux obtained by electrical resistive heating of a metal foil on the surface. The tests were conducted in air for modified Grashof numbers up to 1015. Measurements were made of the local surface temperature for this constant heat flux condition, for the plate inclined at angles from 30 deg to the vertical (upward facing, unstable) through the vertical to 80 deg to the vertical (downward facing, stable). The results show the location of the transition to be a function of the plate angle. For the unstable case, the transition length decreases as the plate angle increases from the vertical while for the stable case the position of transition increases with the angle from the vertical. The laminar data for both orientations are correlated as: Nux=0.55(Grx*Pr)0.20 in which the gravity is the component along the surface, g cos θ. The turbulent natural convection data are correlated quite well by the relation: Nux=0.17(Grx*Pr)0.25 In the turbulent case the correlation is independent of angle for the unstable case, whereas for the stable case the data correlate best when the gravity is modified by cos2 θ, where θ is measured from the vertical. Thus, there is a significant influence of angle on the convective heat transfer for the stable turbulent region.
Melting and Evaporation Phenomena During Electrical Erosion
Authors: Toren M. , Zvirin Y. , Winograd Y.
Published: November 2010

A modeling method is presented for the evaluation of the eroded crater during electrical discharge machining. The method is based on the propagation of the melting crater when other effects such as evaporation can take place. Calculations are performed for a point heat source on the surface of copper and steel electrodes. An experimental technique for the measurement of the amount of eroded material is described: the method consists of extraction of the metal from the dielectric fluid by chemical reactions and measurement of the resulting color intensity.
Laminar Film Condensation on a Vertical Melting Surface
Authors: Epstein M. , Cho D. H.
Published: November 2010

Laminar film condensation of a saturated vapor on a vertical melting surface is treated theoretically, with emphasis on departures from a previous treatment produced by: (a) arbitrary liquid Prandtl numbers and (b) condensation-melting systems involving two materials of immiscible liquids. An integral method is utilized which takes full account of the effects of both liquid film inertia and shear force at the condensing vapor-liquid film interface. For a one-component system accurate numerical results for the melting rates are displayed graphically and define the range of validity of a simple treatment of this problem based on Nusselt’s method. For a two-component system, illustrative calculations are made for the condensation of a refrigerant vapor on melting ice.
Theory on Thermal Instability of Binary Gas Mixtures in Porous Media
Authors: Lawson M. L. , Yang Wen-Jei , Bunditkul S.
Published: November 2010

A theory is developed which predicts the instability of a horizontal layer of porous medium saturated with a binary gas mixture. The lower boundary of the system is maintained at a higher temperature and the upper one at low temperature. The transport equations and coefficients are developed on the basis of kinetic theory. A linear perturbation technique is employed to reduce the governing equations for momentum, heat, and mass transfer to eigenvalue differential equations which are solved by the Finlayson method, the combination of the Galerkin method and the Routh-Hurwitz stability criterion. Only neutral stationary stability is found to occur in the system. Its criterion can be predicted by a simple algebraic equation. Both the critical Rayleigh and wave numbers for the onset of convection are governed by five independent dimensionless parameters, two of which are most influential. The critical Rayleigh number may be lower or greater than that for pure fluid layer depending upon whether thermal diffusion induces the heavier component of the mixture to move toward the cold or hot boundary, respectively. The theory compares well with the experimental results.