bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonaxisymmetric Flow in the Narrow Gap Between a Rotating and a Stationary Disk
Authors: Bein M. , Shavit A. , Solan A.
Published: November 2010

The flow between a rotating disk and a stationary disk, with nonaxisymmetric boundary conditions is studied. A flow field of this type exists in the narrow gap between the rotor and side plates of a rotary vane compressor. Fluid is admitted into the gap in the center of the disk for the purpose of sealing against leakage due to the nonaxisymmetric pressure distribution externally imposed on the disk circumference. The flow is solved analytically by a perturbation technique. Flow maps and pressure maps are obtained for various operating conditions. The effectiveness of the fluid seal is evaluated for these conditions by calculating the flow rates that pass through the gap. The flow field is simulated on a test apparatus and experimental verification is given to the analytical results. The results obtained indicate the possibility of appreciably reducing the leakage through the gap by a proper selection of the fluid pressure and the disk geometry.
An In Vitro Study of Transendothelial Albumin Transport in a Steady State Pipe Flow at High Shear Rates
Authors: Reif Thomas H. , Nerem Robert M. , Kulacki Francis A.
Published: November 2010

The effect of high wall shear rates on the uptake of 131I-albumin by the arterial wall has been studied in vitro using common carotid arteries excised from anesthetized dogs and perfused with a steady state flow of homologous serum. Wall uptake was found to depend nearly linearly upon wall shear rate. The overall transport of 131I-albumin from the perfusing fluid to the vessel wall appears to be rate controlled by a shear dependent fluid-wall interface process. This study was carried out at high shear rates for flows which were transitional and turbulent. Because of the complexity of such flows, direct measurements of pressure drop were used to determine the shear rate at the vessel wall. Simultaneous pressure drop and flow measurements allowed the determination of the friction factor as a function of Reynolds number; results obtained at the higher Reynolds numbers correspond to those for a rigid pipe with a relative roughness of 0.05.
The Breakup Length of Turbulent Liquid Jets
Authors: Lafrance P.
Published: November 2010

A formula for the statistical distribution of the breakup length of a turbulent liquid jet is derived. The formula is based on a model in which random turbulent fluctuations are amplified by capillary instability. A comparison with experimental data is made.
A Survey of Fluid Mechanics Education of Mechanical Engineers
Authors: Lamb J. P. , Swim W. B.
Published: November 2010

Results are presented from a national survey of fluid mechanics courses taught in Mechanical Engineering Departments of U. S. institutions for the academic year 1975–1976. The respondent sample included 91 institutions of widely varying character. Data from five groups of fluids courses are discussed: required undergraduate courses including basic and advanced level; advanced level undergraduate elective courses; graduate level courses; and continuing education courses. Primary educational features reviewed include subject area, textbook used, relative emphasis between theory and applications, credit hours, relative use of multiple course sequence, and amount of laboratory instruction. Guidelines for future surveys are also included.
A Note in Comment on “A Reynolds Stress Model for Turbulent Corner Flows”
Authors: So Ronald M. C.
Published: November 2010

In [1] Gessner and Emery proposed a closure scheme for the Reynolds-stress equations such that the resultant equations are algebraic and can be solved for the various stress components for corner flows. This note summarizes the earlier work on such closure models for different kinds of turbulent shear flows which was omitted by Gessner and Emery and comments on the general applicability of the model proposed by Gessner and Emery.
Turbulent Flow, Heat Transfer, and Mass Transfer in a Tube With Surface Suction
Authors: Kinney R. B. , Sparrow E. M.
Published: November 2010

The problem of turbulent pipe flow with mass removal at the bounding surface is analyzed, and numerical results are presented for the friction factor, axial pressure gradient, heat and mass transfer coefficients, and velocity and temperature profiles. The results, which are relevant to forced-convection condensation in a tube (either with or without noncondensable gases) are shown to be substantially affected by even small amounts of wall suction. Therefore, the present findings do not support the current practice of using impermeable-boundary transfer coefficients in condensation calculations. The analysis is performed under the condition that the velocity field is locally self-similar. Corresponding conditions are used for the distributions of temperature and mass fraction. The cross-sectional distributions of the transverse velocity and the shear stress are not constrained in advance, but rather, are permitted to vary in accordance with the conservation laws. The turbulent transport is expressed in terms of the mixing-length, model, modified in the neighborhood of the wall by a specially derived dumping factor.
Surface Wetting Through Capillary Grooves
Authors: Bressler R. G. , Wyatt P. W.
Published: November 2010

The effects of capillary grooves on surface wetting and evaporation have been analysed. An attempt has been made to obtain expressions which approximately describe the increase in heat transfer in order to select for given properties and temperature differences a groove of optimum design. For this purpose, it is assumed that the heat transfer mechanism is determined by thermal resistance of the liquid layers inside the grooves. From a numerical evaluation of linearized equations, heat transfer rates have been computed for grooves with triangular, semicircular, and square cross sections.
Condensation of Steam on a Rotating Vertical Cylinder
Authors: Nicol A. A. , Gacesa M.
Published: November 2010

Heat transfer coefficients have been determined for steam condensing on a 1-in-dia vertical tube, rotating on its axis. The condensing heat transfer coefficients increased with speed of rotation and for the maximum rotational speed of 2700 rpm investigated were found to be four or five times the stationary value. When the results were plotted in terms of the pertinent parameters of Nusselt number and Weber number, the Nusselt number was found to be constant for Weber numbers below 500, and above this the correlating equation was NNUA, = 6.13 NWC0.496.
Thermal Contact Resistance of Anisotropic Materials
Authors: Vutz N. , Angrist S. W.
Published: November 2010

This work presents an extension of the understanding of thermal contact resistance to include anisotropic materials. The extension involves a mathematical geometric transformation which leaves the thermal currents unchanged while making the temperature distribution in the anisotropic materials soluble by previously published methods. The development of this transformation technique is presented, and the effect of material anisotropy is calculated for a set of interface orientations and material conductivities which characterize typical contact situations. The degree of material anisotropy and the orientation of the contact interface are shown to be important factors affecting the contact resistance in addition to surface roughness, material hardness, and contact load.
Local Heat Transfer Downstream of Abrupt Circular Channel Expansion
Authors: Zemanick P. P. , Dougall R. S.
Published: November 2010

Experimental work was performed to determine local Nusselt numbers in the region beyond an abrupt expansion in a circular channel. Three expansion geometries, ratios of upstream-to-downstream diameter of 0.43, 0.54, and 0.82, were tested with air as the working fluid. Data are shown for Reynolds numbers from 4000 to 50,000–90,000 depending on geometry. Selected comparisons with previously published data for air and water are included.
Asymptotic and Numerical Solutions for Nonlinear Conduction in Radiating Heat Shields
Authors: Malmuth N. , Kascic M. , Mueller H. F.
Published: November 2010

A two-point boundary value problem associated with nonlinear one-dimensional conduction in radiating heat shields and other applications is solved by perturbation and numerical methods. An exact numerical solution is compared with asymptotic results consisting of a previously developed weak conduction solution and its strong conduction counterpart, which is obtained in the present analysis. It is found that the strong conduction asymptotic applies over a much wider range of the radiation conduction parameter than the weak one. Typical calculations show that the maximum temperature of the heat shield is reduced by only nine percent, with a disproportionate increase in end temperature of 32 percent in increasing the radiation conduction parameter from zero to infinity. However, an important structural benefit is obtained by significant reduction in the temperature differences along the shield, with moderate increases in the radiation conduction parameter.
Effects of Velocity and Current on Temperature Distribution Within Crossflow (Blown) Electric Arcs
Authors: Benenson D. M. , Cenkner A. A.
Published: November 2010

The effects of both velocity and current upon the temperature distribution within, and the cross-sectional shape of, steady-state 1.1 atm argon crossflow arcs have been determined experimentally. The tests were conducted over one range at constant current (I = 60.3 amp), U = 0, 41.8 ≤ Ucm/sec ≤ 127.0 and another range at constant velocity (U = 41.8 cm/sec), 42.5 ≤ Iamp ≤ 80.8. Forced convection (at constant arc current) exerts a profound influence upon the crossflow arc. At higher velocities, forced convection appears to completely penetrate the plasma. The effect of increasing current (at constant velocity) is to shield a central core region from the flow field. As a result of the effects of velocity, electrode design, interactions of the electrode jets, and slight misalignment of the jets, neither the isotherms nor the cross sections can be considered to be generally circular, even at the higher currents.
Liquid Droplet Deposition in Two-Phase Flow
Authors: Farmer R. , Griffith P. , Rohsenow W. M.
Published: November 2010

Two-phase annular flow deposition was studied. Experiments were performed to determine where small water droplets in an air stream in a round tube would reach the wall. Results indicated that, for fully accelerated droplets whose diameters were within a factor of two of 150 microns, the number reaching the wall was characteristic of exponential decay with distance downstream. Further, the mean free path to the wall, measured axially, could be taken proportional to droplet diameter. With the assumption that dispersed liquid flow rate in annular two-phase flow regimes consists chiefly of droplets traveling at or near gas velocity, and with arbitrary choices of droplet, diameter spectrum and magnitude of entrainment rate, it was possible to derive analytical expressions for mass transfer coefficient, deposition flow rate, dispersed liquid flow rate, mean diameter and spectrum as they all changed downstream. Some experimental measurements by others were successfully reproduced by these expressions. An important result was that droplet size spectrum “hardening” (preferential depletion of small sizes) operates to decrease the deposition rate downstream, especially if there is no longer any entrainment.
Heat Transfer to Pool-Boiling Mercury From Horizontal Cylindrical Heaters at Heat Fluxes up to Burnout
Authors: Turner J. Brent , Colver C. Phillip
Published: November 2010

Reproducible and consistent data were obtained for heat transfer to pool-boiling mercury from horizontal, 304 stainless steel, cylindrical heaters at heat fluxes up to 1,100,000 Btu/hr· ft2. One actual burnout determination was made during the course of the study. In other runs, a heat-flux level was reached where the slope of the boiling curve decreased significantly so that subsequent increases in heat flux were accompanied by large increases in ΔT. This heat-flux level was termed the “departure heat flux.” Observed maximum departure heat fluxes ranged from 400,000 Btu/hr·ft2 for a 2-in. pool depth above the heater to 950,000 Btu/hr·ft2 for an 8.5-in. depth. The burnout correlations of Noyes [17, 22] and Addoms [1] satisfactorily predicted the maximum departure heat fluxes for each pool depth studied.
Turbulent Flow in a Tube With Wall Suction
Authors: Merkine L. , Solan A. , Winograd Y.
Published: November 2010

The effect of wall suction on turbulent flow in a tube is analyzed, using a mixing-length model with an extended form of van Driest’s damping factor. It is shown that an empirical damping factor similar to that proposed by Kays, Moffat, and Thielbahr, when incorporated in a method of solution developed by Kinney and Sparrow, predicts that the turbulence level in tube flow decreases with suction, and yields excellent correlation with the experiments of Weissberg and Berman.
Calculation of Incompressible Turbulent Boundary Layers With Mass Transfer, Including Highly Accelerating Flows
Authors: Cebeci T. , Mosinskis G. J.
Published: November 2010

This paper describes a general method for calculating turbulent boundary layers with and without mass addition. The method, as in earlier studies, is based on the eddy-viscosity concept. However, the eddy-viscosity formulation presented in this paper differs from the previous ones in that the previous eddy-viscosity formulation has been generalized to handle flows with mass transfer. A large number of flows computed with this method show good agreement with experiment.
Surface Temperatures and Heat Fluxes Associated With the Evaporation of a Liquid Film on a Semi-Infinite Solid
Authors: Hale L. A. , Anderson S. A.
Published: November 2010

The boundary-value problem associated with the evaporation of a thin liquid film from a thick surface is presented in terms of several dimensionless parameters. A numerical solution is presented for a particular limiting case and the result is used to suggest criteria for determining the significance of thin-film evaporation in saturated pool boiling.
Freeze-Drying of Bodies Subject to Radiation Boundary Conditions
Authors: Dyer David F. , Sunderland J. Edward
Published: November 2010

A solution is obtained for the transient temperature distribution and the position of the sublimation front for freeze-drying slabs, cylinders, and spheres. The surface is exposed to thermal radiation boundary conditions so that the surface temperature is time dependent. Results, presented in dimensionless form, cover a wide range of variables that should include essentially all food products.
The Effect of Curvature on Heat or Mass Transfer from an Isothermal Sphere
Authors: Watts R. G.
Published: November 2010

Heat or mass transfer from a sphere to a moving fluid at moderate Reynolds and Peclet numbers is governed by an equation of the form Nu¯orSh¯=C1Pen+C2 All of the parameters C1, C2, and n are functions of the Prandtl number. For the constant-properties case the ranges of the parameters are given in Table 1. The parameter C2 is not necessarily 2 as is sometimes assumed since the equation cannot be used when Pe → 0. C2 is shown to be a first-order correction term resulting from the approximate solution of the energy equation including curvature by a perturbation technique.
Laminar Natural Convection under Nonuniform Gravity
Authors: Lienhard J. , Eichhorn R. , Dhir V.
Published: November 2010

Laminar natural convection is analyzed for cases in which gravity varies with the distance from the leading edge of an isothermal plate. The study includes situations in which gravity varies by virtue of the varying slope of a surface. A general integral solution method which includes certain known integral solutions as special cases is developed to account for arbitrary position-dependence of gravity. A series method of solution is also developed for the full equations. Although it is more cumbersome it provides verification of the integral method.
Correlations for Thermal Contact Conductance In Vacuo
Authors: Thomas T. R. , Probert S. D.
Published: November 2010

A correlation developed by Holm for thermal contact conductance measurements made in vacuo is discussed and its physical basis is deduced with the help of dimensional analysis. On modifying Holm’s treatment by including surface roughness and neglecting nominal contact area, the analysis yields a dimensionless conductance C* = C/σk and a dimensionless load W* = W/σ2M. When 350 data points from the literature for aluminum and stainless steel contacts in vacuo are plotted in this form C* is found to be proportional to about W*0.73 with correlation coefficients of better than 0.9. The correlations for the two materials do not coincide, however, and this and other discrepancies are discussed.
Laminar Free Convection from a Rotating Radial Plate
Authors: Lock G. S. H. , Ko R. S.
Published: November 2010

The paper presents a theoretical analysis of conduction through, and free convection from, a radial plate rotating in a synchronous environment of air. The plate resembles a tapered, radially protruding fin heated at the root. Ordering of the governing equations reveals three controlling parameters, under the condition of steady high-speed rotation. Numerical solutions to the combined conduction–convection problem reveal the effect of the parameters on the velocity and temperature profiles, the overall heat-transfer relation, and the fin effectiveness.
Design of a Specular Aspheric Surface to Uniformly Radiate a Flat Surface using a Nonuniform Collimated Radiation Source
Authors: Horton T. E. , McDermit J. H.
Published: November 2010

When uniform radiative heating is desired on a surface the radiative heating system normally suffers from either (1) low efficiency or (2) the heating not being as uniform as desired. Using an axisymmetric collimated but nonuniform source of radiation and a properly designed specular surface, uniform heating can be obtained at 100 percent efficiency. The differential equation which describes such a surface is derived. The derivation is facilitated by the use of a vectorial ray-trace formulation. The differential equation has been solved and results are presented for the case of an axisymmetric nonuniform collimated source uniformly heating a flat surface.
Finite-Element Method Applied to Heat Conduction in Solids with Nonlinear Boundary Conditions
Authors: Beckett R. E. , Chu S.-C.
Published: November 2010

By use of an implicit iteration technique, the finite-element method applied to the heat-conduction problems of solids is no longer restricted to the linear heat-flux boundary conditions, but is extended to include nonlinear radiation–convection boundary conditions. The variation of surface temperatures within each time increment is taken into account; hence a rather large time-step size can be assigned to obtain transient heat-conduction solutions without introducing instability in the surface temperature of a body.
Non-isothermal Laminar Flow of Gases through Cooled Tubes
Authors: Back Lloyd H.
Published: November 2010

Numerical solutions of the laminar-flow equations in differential form are presented for gas flows through cooled tubes. For nearly isothermal flow there is good agreement with available experimental data, as is also found for the case of a large amount of wall cooling. This correspondence along with a check on the satisfaction of the global momentum and energy constraints allowed an appraisal of the effect of wall cooling on flow through tubes. In general, the effect of wall cooling was to decrease the wall friction and the change in pressure along tubes, but the average heat-transfer coefficient did not vary much.
Thermal Mapping, via Liquid Crystals, of the Temperature Field near a Heated Surgical Probe
Authors: Cooper T. E. , Groff J. P.
Published: November 2010

This paper discusses the use of heat for producing clinical lesions in tissue and presents the design and analysis of a resistively heated surgical probe. The probe surface temperature is accurately maintained and controlled by using a Wheatstone bridge. The probe was embedded in a clear agar–water test medium, and the temperature field generated by the probe was measured with liquid crystals, a material that provides a visual display of certain isotherms. Experimental results compare within approximately 10 percent of a two-dimensional numerical solution. A one-dimensional theoretical model is also developed which examines the influence of blood flow on the temperature field.
Refrigerant–Water Scaling of Critical Heat Flux in Round Tubes—Subcooled Forced-Convection Boiling
Authors: Purcupile J. C. , Tong L. S. , Gouse S. W.
Published: November 2010

Subcooled, critical heat-flux test data on refrigerant R-11 flowing vertically in a uniformly heated circular tube is reported. Using the data reported by Coeffield for R-113, a method is presented for obtaining a direct heat-flux scaling factor between refrigerant and water with the same geometry, mass velocity, and local flowing quality when the pressure is adjusted so that the liquid-to-vapor density ratios are equal in both systems.
Natural Convection in Horizontal Thin-Walled Honeycomb Panels
Authors: Hollands K. G. T.
Published: November 2010

This paper presents an experimental study of the stability of and natural convection heat transfer through a horizontal fluid layer heated from below and constrained internally by a honeycomb. Examination of the types of boundary conditions exacted on the fluid at the cell side-walls has shown that there are three limiting cases: (1) perfectly conducting side-walls; (2) perfectly adiabatic side-walls; and (3) side-walls having zero thickness. Experiments described in this paper approach the latter category. The fluid used is air and the honeycomb used is square-celled. Measured critical Rayleigh numbers are found to be intermediate between those applying to cases (1) and (2), and consistent with an “equivalent wave number” of approximately 0.95 times that for case (1). The measured natural convective heat transfer after instability is found to be significantly less than that predicted by the Malkus-Veronis power integral technique. However, it is found to approach asymptotically the heat transfer which would take place through a similar fluid layer unconstrained by a honeycomb. A general correlation equation for the heat transfer is given.
Thermal Spike Model With Temperature-Dependent Specific Heat
Authors: Kalimullah  , Anno J. N.
Published: November 2010

The thermal spike model is examined with a linear temperature-dependent specific heat. The predicted microvolume of melted material in this case is not significantly different from that predicted with constant specific heat. This result indicates that the thermal spike calculation, as presented here, is not strongly dependent on the variation of physical properties with temperature.
Theoretical Model of the Mixture-Vapor Transition Point Oscillations Associated With Two-Phase Evaporating Flow Instabilities
Authors: Wedekind G. L. , Beck B. T.
Published: November 2010

A horizontal tube evaporator in which complete vaporization takes place can be divided into three distinct regions—a subcooled, a two-phase, and a superheat region. The mixture-vapor transition point corresponds to the liquid film dryout point, and when entrainment is negligible, it represents the boundary between the two-phase and superheat regions. Experimental evidence indicates that during what is conventionally accepted as steady flow conditions, the motion of the mixture-vapor transition point is of an oscillatory nature. Furthermore, not only are the oscillations random, but their statistical characteristics can be represented by a modified Rayleigh distribution. This paper presents the formulation of a theoretical model which incorporates various deterministic mechanisms, while at the same time includes the existence of a random phenomenon. The model has the capability of predicting the influence of evaporator heat flux and inlet flow quality on the statistical characteristics of the transition point oscillations. Perhaps, the most significant potential of the proposed model is that it represents a first step toward the formulation of some of the fundamental mechanisms associated with two-phase evaporating flow instabilities on a statistical basis; a basis which appears to be consistent with many of the experimental observations currently available.
Time-Dependent Transpiration Heat Transfer in Porous Cylinders
Authors: Burch D. M. , Peavy B. A. , Allen R. W.
Published: November 2010

This paper investigates the transient temperature distribution within transpiration-heated and -cooled porous tubes that occur after a step increase in the rate of convective heat transfer at one of the tube surfaces. Analytic solutions are presented for transpiration cooling, catalytic chemical reactor, and tubular regenerator applications. These solutions include the effect of forced convective heat transfer at both tube surfaces where conventional heat-transfer coefficients are used to define the boundary conditions.
An Experimental Investigation of Natural Convection With Vertical Cylinders in Mercury
Authors: Wiles L. E. , Welty J. R.
Published: November 2010

An experimental investigation of laminar natural convection heat transfer from a uniformly heated vertical cylinder immersed in an effectively infinite pool of mercury is described. A correlation was developed for the local Nusselt number as a function of local modified Grashof number for each cylinder. A single equation incorporating the diameter-to-length ratio was formulated that satisfied the data for all three cylinders. An expression derived by extrapolation of the results to zero curvature (the flat plate condition) was found to agree favorably with others’ work, both analytical and experimental. The influence of curvature upon the heat transfer was found to be small but significant. It was established that the effective thermal resistance through the boundary layer is less for a cylinder of finite curvature than for a flat plate. Consequently, local heat transfer coefficients for cylinders are larger than those for flat plates operating under identical conditions.
An Exact Solution for the Temperature Distribution in Parallel Plate Poiseuille Flow
Authors: Deavours C. A.
Published: November 2010

This paper finds by an exact method the temperature distribution in a viscous fluid undergoing Poiseuille flow between two infinite parallel plates. The upstream portion of the plates is assumed to be at temperature T = T− and downstream portion of the plates to be at temperature T = T+. Results are obtained numerically for the “entrance region” temperature profiles. These tend rapidly to zero away from the point where the wall temperature changes abruptly. Using asymptotic expansions for the functions involved estimates are made for the number of terms required to achieve a given level of accuracy for a given Peclet number (Pe). Typical results for Pe = 1 and 10 are shown graphically.
Heat Transfer From Animal Appendage Shapes–Cylinders, Arcs, and Cones
Authors: Wathen P. M. , Mitchell J. W. , Porter W. P.
Published: November 2010

The heat transfer relationships for shapes that approximate animal appendages have been experimentally determined. Finite length hollow cylinders, arcs, and cones with different amounts of closure were tested over a wide range of pitch and yaw angles at different wind speeds. The data for all of these shapes are within ±70 percent of the standard correlation for circular cylinders. Pitch and yaw variations have little effect on the heat transfer coefficient. Shorter length geometries and those with less enclosure have higher heat transfer than the longer and more enclosed geometries. The application of these results to modeling the heat transfer from animal appendages is illustrated.
Convective Heat Transfer From a Desert Surface
Authors: Bailey R. T. , Mitchell J. W. , Beckman W. A.
Published: November 2010

The convective heat transfer relations for atmospheric flow over sparsely vegetated areas are reviewed and compared to existing relations for flow in rough ducts. Experimental convection coefficients obtained at four desert sites are compared to the analytical relations. The experimental equipment for measuring the heat transfer convection coefficient between air and ground in a desert environment consists of two electrically heated plates positioned flush with the ground. Measurements of power dissipation and surface temperatures allow direct calculation of the convection coefficient. The experimental heat transfer results are correlated with micrometeorological models from which a soil roughness height is calculated. This roughness parameter is shown to characterize air flow near the soil surface, and may be significantly different from the roughness parameter ordinarily determined from velocity profiles. A simplified heat transfer correlation is presented for desert surfaces.
Natural Convection in a Horizontal Layer of Water Cooled From Above to Near Freezing
Authors: Forbes R. E. , Cooper J. W.
Published: November 2010

Natural convection in horizontal layers of water cooled from above to near freezing was studied analytically. The water was confined laterally and underneath by rigid insulators, and the upper horizontal surface was subjected to: (1) a constant 0C temperature, rigid conducting boundary, and (2) a free, water to air convection boundary condition, in which the convective heat transfer coefficient was held constant at values of 5.68 W/m2 · K and 284 W/m2 · K (1.0 and 50.0 Btu/hr ft2F) and the temperature of the ambient air was maintained at 0C. The ratios of the width to the depth of the rectangular water layers under consideration were W/D = 1, 3, and 6. Initially the water is assumed to be at a uniform temperature of either 4C or 8C, and then the upper surface boundary condition was suddenly applied. It was observed in all cases for which the initial water temperature was 4C, that the water remained stagnant and became thermally stratified. Heat transfer application of either of the surface boundary conditions to water initially at 8C produced large convective eddies extending from the bottom to the top of the layer of water. As the liquid layer cooled further, two distinct horizontal regions appeared, the 4C isothermal line separating the two. This produces a region of hydrodynamic instability in the fluid since the maximum density fluid (4C) is physically located above the less dense fluid in the lower portion of the cavity. The large eddies which appeared initially were confined to the hydrodynamically unstable region bounded by the 4C isotherm and the bottom of the cavity. The action of viscous shearing forces upon the stable water above the 4C isotherm produced a second “layer” of eddies. An alternating direction implicit finite difference method was used to solve the coupled system of partial differential equations. The paper presents transient isotherms and streamlines and a discussion of the effect of maximum density on the flow patterns.
Laminar Flow in a Porous Tube With Suction
Authors: Quaile J. P. , Levy E. K.
Published: November 2010

A theoretical and experimental investigation of the flow in a porous tube with wall suction is described. The flow is steady, laminar, and incompressible with the fluid entering at one end of the circular tube and flowing out through the porous circumferential surface. The study is limited to an inlet velocity profile parabolic in shape and to the case of uniform wall suction.
An Experimental Study of Low Prandtl Number Natural Convection in an Array of Uniformly Heated Vertical Cylinders
Authors: Dutton J. C. , Welty J. R.
Published: November 2010

An experimental program was conducted to study natural convection heat transfer in an array of uniformly heated vertical cylinders in mercury. The cylinders were arranged in an equilateral triangular pattern, and three bundle spacings, P/D = 1.5, 1.3, and 1.1, were studied. The heat transfer results are presented as local Nusselt number—modified Grashof number correlations. The results indicate a strong dependence on cylinder spacing and the somewhat lesser effects of heat flux and circumferential position. In addition, mean radial temperature profiles were recorded for various conditions as well as the fluctuations in the fluid temperatures which were encountered. The influence of cylinder spacing and axial, radial, and circumferential position on these profiles and disturbances is discussed.
Heat Transfer in the Laminar Boundary Layer Over an Impulsively Started Flat Plate
Authors: Watkins C. B.
Published: November 2010

Numerical solutions are described for the unsteady thermal boundary layer in incompressible laminar flow over a semi-infinite flat plate set impulsively into motion, with the simultaneous imposition of a constant temperature difference between the plate and the fluid. Results are presented for several Prandtl numbers.
Reduction of Heat Transfer to Gun Barrels by Wear-Reducing Additives
Authors: Brosseau T. L. , Ward J. R.
Published: November 2010

Heat transfer measurements were made in a 37-mm gun equipped with thermocouples at a series of axial and radial positions. The heat transferred to the gun barrel was markedly decreased when wear-reducing additives such as polyurethane foam, titanium dioxide/wax, and talc/wax were used as liners wrapped around the gun propellant. The reduction in heat transfer was greatest when the additives were folded over the forward end of the propellant at the base of the projectile. For a given configuration, all three additives tested reduced heat transfer to the gun barrel equally. This contradicts conclusions reached in full-scale tank-cannon firing tests that TiO2/wax and talc/wax are superior to polyurethane foam as erosion reducing additives. In these firings only the metal-oxide/wax liners had flaps folded over the forward end of the propelling charge.
Subcooled Decompression Analysis in PWR LOCA
Authors: Namatame K. , Kobayashi K.
Published: November 2010

The thermo-hydraulic behavior of the coolant in the primary system of a nuclear reactor is important in the core heat transfer analysis during a hypothetical loss-of-coolant accident (LOCA). The heat transfer correlations are strongly dependent on local thermo-hydraulic conditions of the coolant. The present work allows to calculate such thermohydraulic behavior of the coolant during subcooled decompression in PWR LOCA by solving the mass, momentum, and energy conservation equations by the method of characteristics. Detailed studies were made on the transient coolant outflow at the pipe rupture and the effect of frictional loss and heat addition to the coolant on the decompression. Based on the studies, a digital computer code, DEPCO-MULTI, has been prepared and numerical results are compared with the ROSA (JAERI) and the LOFT (NRTS) semiscale test data with various coolant pressures, temperatures, pipe break sizes, and omplexity of flow geometry. Good agreement is generally obtained.
An Investigation of the Laminar Overfire Region Along Upright Surfaces
Authors: Ahmad T. , Faeth G. M.
Published: November 2010

Numerical calculations are presented for the laminar overfire region along an upright burning surface under natural convection conditions. The process was also examined experimentally, using wicks soaked with methanol, ethanol, and propanol to simulate the burning portion of the surface. Predicted flame shapes and wall heat fluxes were within 15–20 percent of the measurements, for various wall inclination angles, except near the tip of the flame where the reaction is quenched by the cold wall. The wall heat flux is nearly constant in the region where the flame is present, but declines beyond the tip of the flame. Shadowgraphs were employed to determine the position of onset of turbulence. For transition beyond the tip of the flame, the flow was laminar for Grx′ < .5 − 2 × 108, although transition is not completely described by this parameter and effects of fuel type, presence or absence of combustion, distance, and wall angle were also observed.
Heat Transfer in Internally Finned Tubes
Authors: Masliyah J. H. , Nandakumar K.
Published: November 2010

Heat transfer characteristics for a laminar forced convection fully developed flow in an internally finned circular tube with axially uniform heat flux with peripherally uniform temperature are obtained using a finite element method. For a given fin geometry, the Nusselt number based on inside tube diameter was higher than that for a smooth tube. Also, it was found that for maximum heat transfer there exists an optimum fin number for a given fin configuration. The internal fins are of triangular shape.
The Numerical Thermal Simulation of the Human Body When Undergoing Exercise or Nonionizing Electromagnetic Irradiation
Authors: Emery A. F. , Short R. E. , Guy A. W. , Kraning K. K. , Lin J. C.
Published: November 2010

The human body was modeled by a finite difference numerical procedure to determine the effect of simulating the sweating rate by different analytical models. Six different models were used in which the hypothalamus, muscle, average skin, and local skin temperatures were used as the controlling parameters for the rate of local sweating. These different models were tested by comparing their predictions of local temperatures for an exercising man with measured values. The computer program was then used to compute the thermal response of a man subjected to microwave irradiation of the entire body and the head only. Transient head and body temperatures and sweating rates were computed and compared with the temperature changes due to an equivalent exercise level. Significant differences in the results found by using the different sweat models point out the need for further work in determining accurate analytical descriptions of this major mode of body heat loss.
The Prediction of Three-Dimensional Discrete-Hole Cooling Processes—Part 1: Laminar Flow
Authors: Bergeles G. , Gosman A. D. , Launder B. E.
Published: November 2010

The paper describes the application of a three-dimensional finite-difference procedure to the problem of predicting the flow and thermal fields arising from the injection of fluid in discrete jets through a wall past which an external stream is flowing. The numerical scheme is of the “partially parabolic” type originated by D. B. Spalding. Predictions of mean velocity and temperature for laminar flow are provided for the cases of a single row of holes inclined at 90, 45, and 35 deg to the plate surface and for a surface with multiple rows of holes in a staggered array. These specifications are for a uniform density flow and a uniform velocity external stream. A final example is presented, simulating typical operating conditions for a gas turbine blade cooled with a single row of holes aligned at 30 deg to the blade surface. Strong streamwise accelerations and density gradients are present. The results show, as has been observed experimentally, that due to the strong acceleration the lateral rate of spread is diminished. Moreover a counter-rotating vortex pair is created downstream from the hole which shifts the minimum effectiveness away from the mid-plane between the holes.
Free Convection Heat Transfer From Spheroids
Authors: Raithby G. D. , Pollard A. , Hollands K. T. G. , Yovanovich M. M.
Published: November 2010

Measurements of the heat transfer by free convection from isothermal spheroids to air are reported. The range of Rayleigh number, Ra, covered was sufficiently large that both thick boundary layer effects (at low Ra) and turbulence (at high Ra) affect the heat transfer. Data are reported for one prolate spheroid and two oblate spheroids. The results of an approximate method of analysis, which accounts for both thick boundary layers and turbulence, are also given. These are compared to the present measurements, and to earlier measurements for spheres. Excellent agreement with experiment is found. Correlation equations, from which average heat transfer rates can be calculated, are also given. These are thought to be valid at all Rayleigh numbers over a large range of eccentricity.
The Heat Balance Integral in Steady-State Conduction
Authors: Sfeir A. A.
Published: November 2010

The Heat Balance Integral Method is applied to solve for the heat flow and temperature distribution in extended surfaces of different shapes and boundary conditions. In most cases the analysis is found to be identical to the exact two-dimensional solutions at Biot numbers for which the one-dimensional analysis is almost 100 percent off. Other possible extensions of the method are briefly described.
Transient Natural Convection of Water in a Horizontal Pipe With Constant Cooling Rate Through 4°C
Authors: Cheng K. C. , Takeuchi M.
Published: November 2010

A theoretical analysis is carried out to study the influence of an anomalous density-temperature relationship of water on the transient natural convection in horizontal cylinders with wall temperature decreasing at a uniform rate. Numercial solutions are obtained for three cases involving different cooling rates, pipe diameters, and initial uniform water temperatures for temperature conditions between 0 and 7°C. The transient flow and temperature fields, and local and overall heat transfer rates are presented to study the inversion of flow patterns caused by the maximum density at 4°C. The numerical results are compared with the experimental measurements and predictions of a quasi-steady boundary-layer model reported by Gilpin [2], and generally a good agreement is observed. Some implications on the subsequent freezing process are pointed out.
Modeling of Temperature and Pollutant Concentration Distributions in Urban Atmospheres
Authors: Viskanta R. , Johnson R. O. , Bergstrom R. W.
Published: November 2010

An unsteady two-dimensional transport model is constructed to study the short-term effects of urbanization and air pollution on the thermal structure and dispersion in an urban atmosphere. The model includes horizontal and vertical advection as well as turbulent diffusion and radiative transfer in the planetary boundary layer (PBL). The gaseous and particulate pollutants as well as the natural constituents in the atmosphere absorb, emit, and anisotropically scatter radiation. The variation of the physical properties of the soil, the radiation characteristics of the earth’s surface, and the urban heat and pollutant emissions along the city are modeled. A number of numerical simulations for summer conditions modeling a typical Midwestern city are performed and the effects of various parameters arising in the problem have been investigated. The diurnal variation of the temperature structure and pollutant concentrations are discussed. It was found that the temperature changes caused by radiatively participating pollutants are generally smaller than the effects induced by urbanization. A maximum urban heat island of approximately 3°C was predicted and found to be in good agreement with observations.
Free Convection Along A Nonisothermal Vertical Flat Plate
Authors: Kao Tsai-Tse , Domoto G. A. , Elrod H. G.
Published: November 2010

A technique has been developed for the solution of free convection problems on a vertical flat plate with arbitrary (though smooth) temperature or heat-flux distributions. The general theory is developed with local similarity as a first approximation, and universal functions for improvement. Comparisons with highly accurate numerical solutions validate the use of one simple correction term for most applications. Computations are readily performed with the use of a hand-held mini-computer. Four illustrative computational examples are carried out with the aid of the two working charts provided for air.
Flashing Flow of Initially Subcooled Water in Convergent–Divergent Nozzles
Authors: Schrock V. E. , Starkman E. S. , Brown R. A.
Published: November 2010

This paper presents results from a research program conducted a number of years ago on the problem of flashing flow of water in nozzles. In a previous paper [1] we presented results for the case of stagnation states in the low quality two-phase region. The present paper reports results for stagnation states in the subcooled region at pressures up to 9.05 × 103 kN/m2 and subcooling from 0 to 60° C. Pressure profiles and flow rates are reported. The results are compared with limiting cases of Bernoulli flow (meta-stable liquid flow) and homogeneous equilibrium flow. As expected neither was able to predict the experimental results. A two-step model based upon nucleation delay, “discontinuous” transition to two-phase flow followed by frozen composition gave reasonable predictions of the flowrates and pressure profiles in the convergent section.
The Effect of Heat Transfer Coefficient, Local Wet Bulb Temperature and Droplet Size Distribution Function on the Thermal Performance of Sprays
Authors: Chen K. H. , Trezek G. J.
Published: November 2010

Energy balance considerations indicate that the droplet heat transfer coefficient, local wet bulb temperature, and droplet size distribution function are the basic parameters affecting spray system thermal performance. Within the range of available experimental data, results indicate that the Ranz-Marshall correlation gives an agreement to within ±5.0 percent of measured droplet temperatures at the pond surface for a medium wind range of between 2.5 and 5 m/s. The local wet bulb temperature is taken as the arithmetic mean of the initial and final wet bulb temperatures. For wind speeds greater than 3.5 m/s, the local wet bulb can be taken as the ambient. The modified log normal distribution of Mugele and Evans provides the best description of the droplet size distribution. Further, through the introduction of a correction term, the Spray Energy Release (SER) can be deduced from single droplet information.
An Experimental Study of Natural Convection Mass Transfer Along a Vertical Plate With Surface Injection
Authors: Lewis G. B. , Novotny J. L. , Yang K. T.
Published: November 2010

Laminar isothermal natural-convection mass transfer along a porous vertical plate in an aqueous sodium chloride solution with uniform surface injection of pure water at the plate surface is investigated experimentally by means of a Mach-Zehnder interferometer. Grashof numbers for the mass transfer system range from 0.253 × 104 to 0.858 × 107; the surface injection velocities are from 0.519 × 10−4 cm/s to 0.937 × 10−3 cm/s; and Schmidt numbers cover a range from 582 to 643. Steady concentration profiles and rate of surface mass transfer have been obtained, and are compared with the theoretical result based on a similarity solution with matched surface concentration distribution, Grashof and Schmidt numbers, and surface injection rate.
Prediction of Temperature Profiles in Fluid Bed Boilers
Authors: Hodges J. L. , Hoke R. C. , Bertrand R.
Published: November 2010

Data acquired in the Exxon Research and Engineering Company’s fluid bed boiler program indicate that the arrangement and orientation of internal boiler tubes has a strong effect on the measured bed temperature profile. Horizontally oriented tubes yield much steeper temperature gradients than do vertical tubes. Excessive vertical temperature gradients in coal fired fluid bed boilers can either limit coal feed rates or result in the formation of agglomerates of solid material which are destructive of bed internals. This study represents an attempt to understand the influence of orientation on vertical temperature profiles in fluid bed boilers. A back-mixing model for solids recirculation was developed and applied to the prediction of bed temperatures. Bubbling bed theory is not suitable for estimating solids circulation rates in pressurized beds of large particles with immersed tubes. However, by introducing the concept of a solids mixing height it was possible to estimate solid movement. The solids mixing height and vertical boiler tube dimensions were correlated in a manner which resulted in good agreement between theoretical and experimental bed temperature profiles. It is felt that this simple model may prove quite useful in the design of large scale commercial fluid bed boilers.