bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Finite Cylinders Rotating Within Moderate Clearance Ratios
Authors: Pinkus O. , Etsion I.
Published: November 2010

The Navier-Stokes equations are examined here for the flow of an incompressible fluid contained between rotating eccentric cylinders of finite length and moderate clearance ratios. Based on a modified form of the Reynolds Equation an analytical solution for short cylinders, and numerical results for finite configurations are given for the range of Reynolds numbers and (C/R) ratios in which inertia forces can be neglected. In a subsequent paper consideration will be given to the range of Taylor numbers in which inertia and transverse effects may become significant.
Flow Interaction Near the Tail of a Body of Revolution—Part 1: Flow Exterior to Boundary Layer and Wake
Authors: Nakayama A. , Patel V. C. , Landweber L.
Published: November 2010

An iterative procedure for the calculation of the thick attached turbulent boundary layer near the tail of a body of revolution is presented. The procedure consists of the potential-flow calculation by a method of integral equation of the first kind and the calculation of the development of the boundary layer and the wake using an integral method with the condition that the velocity remains continuous across the edge of the boundary layer and the wake. The additional terms that appear in the momentum integral equation for the thick boundary layer and the near wake are taken into account and the pressure difference between the body surface and the edge of the boundary layer and the wake can be determined. The results obtained by the present method are in good agreement with the experimental data. Part 1 of this paper deals with the potential flow, while Part 2 [1] describes the boundary layer and wake calculations, and the overall iterative procedure and results.
A Centrifugal Compressor Flow Analysis Employing a Jet-Wake Passage Flow Model
Authors: Howard J. H. G. , Osborne C.
Published: November 2010

The streamline curvature through-flow analysis of a centrifugal impeller passage flow has been modified to include a flow model with a wake on the suction surface. With this model, empirically determined or measured impeller conditions can be matched without requiring a distributed stagnation pressure loss within the passage. Its use in impeller design is presented and comparison with experimental measurements from two impellers illustrate the utility of this approach. A brief discussion of experience with the associated forms of curve fitting and streamline smoothing required for the analysis solution is included.
Free Turbulent Shear Layers on Plug Nozzles
Authors: Scott C. J. , Rask D. R.
Published: November 2010

Two-dimensional, free, turbulent mixing between a uniform stream and a cavity flow is investigated experimentally in a plug nozzle, a geometry that generates idealized mixing layer conditions. Upstream viscous layer effects are minimized through the use of a sharp-expansion plug nozzle. Experimental velocity profiles exhibit close agreement with both similarity analyses and with error function predictions. Refrigerant-12 was injected into the cavity and concentration profiles were obtained using a gas chromatograph. Spreading factors for momentum and mass were determined. Two methods are presented to determine the average turbulent Schmidt number. The relation Sct = Sc is suggested by the data for Sc < 2.0.
Capsule-Pipelining—An Improved Theoretical Analysis
Authors: Garg V. K.
Published: November 2010

Abstracts

This paper provides an improvement over the earlier theoretical analysis for a rigid, frictionless, cylindrical capsule moving parallel to the horizontal pipe wall (Garg and Round [1]) by taking into account the effects of friction between the capsule and pipe surfaces and of nonuniform clearance over the capsule length. It is found that these effects markedly affect the energy requirements suggesting, thereby, an optimum operation of the capsule-pipeline system. The theoretical results are also compared with the available experimental data.
Taylor-Goertler Vortices and Their Effect on Heat Transfer
Authors: McCormack P. D. , Welker H. , Kelleher M.
Published: November 2010

An experimental measurement of the effect of Taylor-Goertler vortex formation on the heat transfer through the boundary layer on a concave wall has been made. A theoretical analysis based on independent mean and oscillatory flow components indicates that, although the heat transfer rate will fluctuate periodically in the spanwise direction, there should be no overall increase in heat transfer. The experimental results indicate that there is a significant increase in Nusselt number in the presence of the vortices. Interaction between the oscillatory and mean components must be accounted for, if the theoretical model is to be reliable.
Multiple Scatter: Comparison of Theory With Experiment
Authors: Hottel H. C. , Sarofim A. F. , Vasalos I. A. , Dalzell W. H.
Published: November 2010

In the solution of the transport equation for scattering media it is usually assumed that the particles scatter independently, and that polarization effects may be neglected. The validity of these assumptions has been here tested by measurement of the bidirectional reflectance and transmittance of suspensions of monodisperse polystyrene spheres confined between two parallel glass slides, followed by comparison of the results with the values predicted from theory. For the range of conditions studied—particle diameters of 0.106 and 0.530μ, wavelengths of 0.436μ and 0.546μ, and optical thicknesses of 0.25–3000—the agreement between theory and experiment is excellent.
Transient Temperature Distribution in Round and Slab-Type Loads Heated by Electric Induction
Authors: Kasper Robert J.
Published: November 2010

Equations are derived for the transient temperature distribution in a round or slab-type load with a radiation boundary condition, as required for a thermal analysis of large steel sections heated for forging, by electric induction. The load is assumed to be initially at a uniform temperature and then has heat generated in it by the induction process. Initial distribution curves of the derived transient corrections are compared with the steady-state induced thermal wave shapes that would exist at various heating frequencies if not dampened by the transient correction.
Combining Forced and Free Convective Equations to Represent Combined Heat-Transfer Coefficients for a Horizontal Cylinder
Authors: Jackson Thomas W. , Yen Howard H.
Published: November 2010

An analytical correlation of superposed free and forced convection for air for a horizontal cylinder in which the forced convection and free convection forces act in the same direction is considered. A simplified method by which the ordinary formulas for forced convection and for free convection can be used together to give the Nusselt number is presented. The method proposed herein can easily be modified to work for other combinations of free and forced flow systems. The method, therefore, may have wide application because standard formulas for simple systems are easily combined to obtain formulas which are valid for complicated systems.
Thermal Recovery Factors in Supersonic Flows of Gas Mixtures
Authors: Maise George , Fenn John B.
Published: November 2010

Thermal recovery factors were measured at the stagnation point of a hemispheric probe in low-density supersonic jets of helium–argon and hydrogen–nitrogen mixtures. A “guard” heater in the probe made it possible to eliminate conduction losses. Radiation corrections were small. The final values correspond to adiabatic conditions. With jets of mixed gases, experimental recovery factors were as high as 1.6, substantially above the free molecule limit for pure gases. It is suggested that these anomalously high values are due to the species separation which occurs during the stagnation process and which results in concentrations of heavy species in the stagnation zone higher than in the free stream. The results are correlated in terms of the degree of rarefaction and the composition of the jet gas.
Some Experiments on Screen Wick Dry-out Limits
Authors: Chun K. R.
Published: November 2010

Dry-out limits of screen wicks vertically pumping against gravity above an acetone pool were determined in evaporation experiments. As the pumping height shortened, the increase in heat input at dry-out became less than that expected from a fully saturated wick layer. The receding of the evaporating boundary into a sublayer of the wick was postulated, based on the fact that the measured thermal resistance across the wick layer decreased as heat input increased. Such a recess seems to terminate at two layers above the heated wall. A new wicking model taking into account the receding of evaporation boundary could predict the experimental dry-out heat inputs within 10 percent.
Steady Two-Dimensional Forced Film Condensation with Pressure Gradients for Fluids of Small Prandtl Numbers
Authors: Isa Ismaila , Chen Ching-Jen
Published: November 2010

A laminar two-dimensional steady forced film condensation with pressure gradients on a nonisothermal surface with (Tsat − Tw) remaining constant is considered. The case of small Prandtl number has been solved. Body force and interface resistance effects have been neglected. Inertia effect for the liquid phase is assumed negligible. Three parameters govern the problem: the pressure gradient parameter β, the property parameter R = (νv/νl)1/2, and the parameter B = hfg μv/ΔTKl. It is found that an increase in pressure parameter, β, results in the decrease of the average Nusselt number, the condensation rate, and the average skin friction coefficient. With or without pressure gradients, the condensation rate and the heat flux increase with the property parameter R. The average Nusselt number, however, decreases with the parameter B to a minimum and then rises again.
The Effect of Lateral Rod Displacement on Laminar-Flow Transfer
Authors: Hsu Chia-Jung
Published: November 2010

Heat transfer in longitudinal laminar flow through tightly packed rod bundles is analyzed for a rod displaced from its symmetrical position. The influences of the P/D ratio, the magnitude of σ, and the type of thermal boundary condition, etc. on the variation of the coolant temperature field and the rod-average Nusselt number are investigated. Average Nusselt numbers for the displaced rod are calculated for rod bundles with 1.00 ≤ P/D ≤ 2.0 and 0 ≤ σ ≤ 0.8. The results for the special case of σ = 0 (i.e., for symmetrical rod bundle) show excellent agreement with those reported by Dwyer and Berry [1], who analyzed numerically the corresponding problem for symmetrical rod bundles.
Improved Point-Matching Techniques Applied to Multi-Region Heat Transfer Problems
Authors: France D. M. , Ginsberg T.
Published: November 2010

An analytical method is presented which extends the series solution of the Laplace and Poisson equations with irregular boundary conditions to multi-cell problems. The method employs a least-squares technique of satisfying the boundary conditions on the irregular boundaries and eliminates the use of a finite number of boundary points to satisfy these conditions. The technique is applied to the calculation of the fully developed temperature distribution of a constant-velocity fluid flowing parallel to a semi-infinite square array of circular nuclear fuel rods. The bounding wall of the array is located such that the flow area of the cell associated with the rod adjacent to the wall is different from the (equal) areas of all the other cells. The series solution is compared to a finite-difference solution for a sample case of two cells. The results for the semi-infinite array indicate that while the array temperature distribution is markedly affected by the difference in flow areas, the Nusselt numbers of the rods are relatively unaffected. Typical results are presented for a pitch-to-diameter of 1.2; the flow area of the first cell is 3.67 percent greater than the area of the other cells.
Unsteady Heat Transfer and Temperature for Stokesian Flow about a Sphere
Authors: Konopliv N. , Sparrow E. M.
Published: November 2010

An analysis is made of the unsteady thermal processes which result when a moving sphere encounters a fluid environment whose initial temperature is different from that of the sphere. The fluid velocity field is steady and Stokesian, and the temperature field is of the boundary-layer type. Two related physical situations are analyzed. In one of these, the sphere is a solid of high thermal conductance such that its temperature is spatially uniform, but varies with time as a result of heat transfer with the fluid. In the other, the sphere heat capacity and conductance are both large so that its surface temperature is spatially and temporally uniform for a finite period of time. A number of solution methods is employed, including numerical inversion of integral transforms, series, and asymptotic expansions. Results are presented both in graphical and algebraic form for the local and overall heat-transfer rates, for the temperature history, and and for the time required to reach thermal equilibrium.
Falling-Film Solidification Rates for Water inside a Short Vertical Tube
Authors: Mullin T. E. , Renda R. B.
Published: November 2010

The purpose of this investigation was twofold: (1) to present the results of an experimental investigation of the solidification rates for water at its fusion temperature in falling-film flow inside a short vertical tube and (2) to compare the experimental results to those predicted from the expression developed by London and Seban [1]. The experimental data were in good agreement with those values predicted by their expression when evaluated on a weight-of-ice-formed basis. However, the liquid-solid interface radius rs could be determined with reasonable accuracy only for large values of rs. It was shown that by increasing the temperature difference across the ice field, closer agreement was obtained in both cases. It is believed that erosion of the ice by the liquid falling film is responsible for most of the deviations.
Theory of Two-component Heat Pipes
Authors: Tien C. L. , Rohani A. R.
Published: November 2010

A theoretical framework for predicting the steady-state operational characteristics of two-component heat pipes is established. The laws of conservation of mass and energy as well as thermodynamic phase equilibrium relations are applied to the system, and the governing relations between the various system parameters are specified. Measurements of the operational characteristics of a water–ethanol heat pipe indicate that complete separation into two pure components did not occur in any of the experiments. The observed degrees of separation and other operational characteristics agree well with the predictions.
Specular Reflectors for Prescribed Disturbed Radiant Heating from a Point Energy Source
Authors: Pfahl R. C.
Published: November 2010

This paper presents a mathematical model for designing a reflector shape which will produce a prescribed rotationally symmetric energy distribution on a plane workpiece using a single point energy source. The model considers spectral, directional, and polarizing effects. The necessary equations are developed and their solutions described. A reflector is designed to uniformly heat a 6-in-dia circle using a 200-w compact mercury-arc lamp. The validity of the model is demonstrated by constructing the designed reflector and experimentally confirming that the desired heat-flux distribution is achieved. It is quantitatively shown that the minor differences between the desired flux distribution and the actual distribution are due primarily to the finite source size and that a more precise distribution could be obtained by modeling the source as four point sources.
The Effect of Noncondensable Gas on Laminar Film Condensation of Liquid Metals
Authors: Turner R. H. , Mills A. F. , Denny V. E.
Published: November 2010

The effect of noncondensable gas on laminar film condensation of a liquid metal on an isothermal vertical surface with forced vapor flow is analyzed. Where necessary the interfacial resistance due to thermodynamic nonequilibrium is included for a condensation coefficient σ = 1. A computer program has been developed to solve a finite-difference analog of the governing partial differential equations and is applied here to the mercury–air and sodium–argon systems. Heat-transfer results are presented for vapor velocities in the range 1 to 100 fps with mass fraction of gas varying from 10−5 to 3 × 10−2. The overall temperature difference ranged from 0.1 to 30 deg F while the temperature levels were 1200 and 900 deg R for mercury–air and 2000 and 1500 deg R for sodium–argon. The effect of noncondensable gas is most marked for low vapor velocities and high gas concentrations. At the lower pressure levels the inter facial resistance plays a dominant role, causing maxima in the curves of q/qNu versus x. For the mercury–air system the adverse buoyancy force causes vapor boundary-layer separation when the free-stream vapor velocity is low.
Heat, Mass, and Momentum Transfer During the Melting of Glacial Ice in Sea Water
Authors: Griffin O. M.
Published: November 2010

The velocity, temperature, and concentration distributions near a melting surface of glacial, or pure, ice in saline water are determined for laminar flow conditions using integral techniques. Estimates are made of the relative thicknesses of the momentum, thermal, and mass diffusion boundary layers for a variety of the appropriate flow and thermal parameters. These findings are applied to the melting of glacial ice in sea water, but they also are applicable to other systems in which heat, mass, and momentum transfer occur simultaneously with phase transformation. The speed of sound at constant pressure in sea water is a function of temperature and salinity, and the variation of sound speed with changing environmental conditions plays an important role in underwater acoustic propagation. The results of the heat and mass transfer analyses are employed to determine the sound speed profiles within the temperature and salinity boundary layers near the melting glacial ice for free-stream water temperatures of 5 and 10 deg C.
Wave Instability of Natural Convection on Inclined Surfaces Accounting for Nonparallelism of the Basic Flow
Authors: Haaland S. E. , Sparrow E. M.
Published: November 2010

Neutral stability results for Prandtl numbers of 6.7 and 0.733 were obtained by solving disturbance equations that take account of the nonparallelism of the basic flow. Compared with the results for the conventional parallel-flow model, the neutral curves are shifted to higher Grashof numbers and higher wave numbers but maintain their characteristic shapes. The effect of varying the plate inclination from downward-facing to upward facing is to increase the susceptibility of the flow to instability. The critical Grashof numbers are substantially lower than the Grashof numbers of experiments where instability was due to natural disturbances.
Similar Solutions for Film Condensation With Variable Gravity or Body Shape
Authors: Dhir V. K. , Lienhard J. H.
Published: November 2010

The configurations of laminar film condensation on two-dimensional isothermal surfaces, for which the complete boundary layer equations admit similarity solutions, are described. These configurations include certain kinds of curved surfaces at earth-normal gravity and/or certain variable-gravity fields. The bodies have forward stagnation points, near which the governing equations break down. A criterion is given for delimiting the region in which the theory does not apply. It is shown how to compute heat transfer results for the similar solutions and some examples are worked. Condensation on a cool plate, synchronously rotating with a vapor, is treated in some detail.
The Effect of Obstacles on a Liquid Film
Authors: Shiralkar B. S. , Lahey R. T.
Published: November 2010

It has been observed in simulated nuclear reactor critical heat flux (CHF) experiments that CHF tends to occur upstream of flow obstructions, such as grid type spacers. An experimental program was conducted to quantify the effect of various obstacles on a liquid film. Although this was an adiabatic (air-water) study, a phenomenological mechanism causing dryout was observed. A simplified analysis of the observed phenomena has indicated that, above a critical Weber number, the ratio of the momenta of the liquid and vapor streams is the important parameter in determining when an upstream dry patch will form.
Local and Average Transfer Coefficients for One-Row Plate Fin and Tube Heat Exchanger Configurations
Authors: Saboya F. E. M. , Sparrow E. M.
Published: November 2010

The analogy between heat and mass transfer has been used to obtain local and average transfer coefficients for a one-row plate fin and tube heat exchanger configuration. The mass transfer experiments were performed using the naphthalene sublimation technique. A heat exchanger passage was modeled using naphthalene plates; spacer disks simulated the tubes. Detailed measurements of the surface elevation of the naphthalene plates were made before and after a data run, and this enabled evaluation of the local transfer coefficients. Average transfer coefficients were determined both by surface integration of the local mass transfer or by weighing the test plate with a precision balance; the two methods gave results that agree within one or two percent. The local measurements revealed high values of the transfer coefficient on the forward part of the fin due to the presence of developing boundary layers. In addition, owing to a natural augmentation effect caused by a vortex system which develops in front of the tube, there are very high fin transfer coefficients in a U-shaped band that rings the tube. The effect of the vortex system is more pronounced at higher Reynolds numbers. Relatively low transfer coefficients are encountered on the portion of the fin that lies downstream of the minimum flow cross section. The coefficients are especially low in the region behind the tube.
A Dry Materials Heat Exchanger With Regeneration
Authors: Berry M. R. , Parker R. W. , Dickerson R. W.
Published: November 2010

The concept of regeneration is successfully demonstrated for the heat processing of sorptive materials in a continuous-flow heat exchanger. Data are presented for oats, cracked corn, and black peppercorns. Regeneration efficiency depends on the relative flow rates of the air and the product. Maximum efficiency was attained with the ratio of the air-to-product heat capacity fluxes near unity. Regeneration efficiency is also dependent on the moisture content of the product entering the heat exchanger. A maximum efficiency of 57 percent was obtained for black peppercorns that entered the heat exchanger with moisture contents of 5 to 8 percent (dry basis) and were processed to a holding temperature of 175° F (79.5° C). Significant drying of the product was realized in the heat exchanger/regenerator. For oats, processed at 200° F, approximately half the moisture was removed in a single pass when the inlet moisture content was 13.7 percent. The amount of drying decreased as the moisture content of the product entering the heat exchanger was lowered. Drying also decreased when the processing temperature was lowered. Considerable energy is consumed by drying, and thus the regeneration effect for high moisture products is not as apparent.
The Effects of Nonuniform Cooling on the Heat Transfer From an Insulated Electric Cable
Authors: Chato J. C. , Chern S. Y.
Published: November 2010

Due to the geometric configurations of convectively cooled underground electric power cable systems, nonuniform cooling of the individual cables can occur. A numerical analysis has been performed on the effects of nonuniform surface cooling on the temperature distribution inside the insulation of a single cable. The results show that with the typical geometries considered, the coolant temperature would have to be lowered significantly in order to maintain a given amount of heat dissipation per unit length in comparison to uniform cooling. It is useful, therefore, to promote uniform cooling around the circumference of each cable by changing the fluid flow pattern and by the use of metal sheathing around the circumference. To evaluate this latter effect, a dimensionless parameter representing the relative magnitudes of heat conduction in the sheathing and in the insulation is proposed.
The Effect of a Stabilizing Temperature Gradient on Heat Transfer From a Molten Fuel Layer With Volumetric Heating
Authors: Suo-Anttila A. J. , Catton I.
Published: November 2010

The Landau method is used to determine the heat transfer to the upper and lower surfaces of a volumetrically heated layer of molten fuel for various fixed values of the upper and lower surface temperatures. To use the Landau method, the Stuart shape assumption is imposed and solutions to the linearized stability problem are used. The results are generalized in terms of two Nusselt numbers (upper and lower surface heat transfer) which are presented as a function of the Rayleigh number based on the internal heat generation rate for various values of an external Rayleigh number based on the surface to surface temperature difference. Results are also presented for a molten UO2 layer for various typical values of decay heat. Comparison is made with experiment, where possible, and found to be good.
Correlation of Theoretical Analysis With Experimental Data on The Performance of Charring Ablators
Authors: Mastanaiah K.
Published: November 2010

Experimental data are obtained for surface recession, char depth, and temperatures in silica phenolic and carbon phenolic ablators from static test conducted on rocket nozzles. In an attempt to correlate the theoretical analysis with the experimental observations, it is found that the effective thermal conductivity of char is strongly dependent on the wall heat flux. An hypothesis is postulated that the char conductivity can best be correlated by cold wall heat flux treated as a generalized variable that includes the effects of other factors like temperature and chemical composition of the char. Exponential dependence of char conductivity on the cold wall heat flux is observed for both the ablators, and has offered excellent comparison between the theoretical and the experimental system response.
An Experimental and Theoretical Study of Heat Transfer in Vertical Tube Flows
Authors: Greif R.
Published: November 2010

An experimental and theoretical study was carried out for the heat transfer in laminar and turbulent tube flows with air and argon. Radial temperature profiles were measured at a location 108 tube diameters from the inlet of the vertical, electrically heated test section. The temperature of the tube wall was also measured. The experimental data were in good agreement with the results obtained from numerical solutions of the conservation equations and from simplified, fully developed solutions. For turbulent flows the Reynolds numbers varied from 10,000 to 19,500; for laminar flows the Reynolds numbers varied from 1850 to 2100 while the Rayleigh numbers varied from 70 to 80.
An Experimental Investigation of Burn Injury in Living Tissue
Authors: Ross D. C. , Diller K. R.
Published: November 2010

The effects of thermal insult on living tissue have been studied by direct microscopic observation of the circulatory system’s response to a controlled trauma regimen. An experimental apparatus has been developed which utilizes a unique high and low temperature stage in conjunction with a precision thermal control system to examine the injury process in the microcirculation of the golden hamster cheek pouch. Unique features of this experimental apparatus are: (1) continuous monitoring of the injury processes at the cellular level, (2) capability for quantitative assay of thermal injury, (3) precise control over the thermal parameters that govern injury, (4) versatility in isolating the effects of these individual parameters. The important thermal parameters monitored using this experimental procedure are the time rates of change of temperature during burning and cooling, the maximum temperature reached, and the length of time the tissue was held at this temperature. With this type of experimental apparatus any portion of the burn protocol, such as the maximum temperature reached during burning, may be varied while holding all other parameters constant. It is well documented that the microvascular bed is a primary site for manifestation of burn wound injury. Burn injury occurs as a consequence of rate dependent physiochemical processes, and, therefore, develops over a finite period of time subsequent to trauma. The experimental technique is designed to determine the gross response of the microvascular system to burn trauma. Initial investigations on burn injury have demonstrated a direct dependency of the extent of damage upon both the maximum temperature attained and the duration of exposure. The minimum temperature required to produce stasis within 20 s after completion of the burn in 95 ±5 percent of the microcirculation decreased exponentially with burn duration between the extremes of 85°C for 1 s exposure and 60°C for 100 s exposure.
Pipe Heating With Steam Tracers
Authors: Steiner A.
Published: November 2010

Steam tracers are widely used in industry for heating pipes transporting fluid that cannot be pumped beneath a certain temperature. In most industrial operations the need for heating does not arise during flow from heated tanks, for the residence time of the pipe content is normally short enough to avoid excessive cooling. However, steam tracers must be added to the pipe to allow warming when pumping is stopped. In this paper a mathematical solution for the heat transfer problem is developed giving the mean temperature of the pipe content and the hottest point temperature as a function of time, under nonflow conditions. The analysis covers the cases of pipes with one or two tracers and with or without heat conducting cement. The equations are cumbersome, but their evaluation for steel pipes with diameters spanning from 38.1 to 355.6 mm and filled with heavy oil products shows that in this particular case they can be greatly simplified.
Non-Fourier Melting of a Semi-Infinite Solid
Authors: Sadd M. H. , Didlake J. E.
Published: November 2010

The melting of a semi-infinite solid subjected to a step change in temperature is solved according to a non-Fourier heat conduction law postulated by Cattaneo and Vernotte. Unlike the classical Fourier theory which predicts an infinite speed of heat propagation, the non-Fourier theory implies that the speed of a thermal disturbance is finite. The effect of this finite thermal wave speed on the melting phenomenon is determined. The problem is solved by following a similar method as used by Carslaw and Jaeger for the corresponding Fourier problem. Non-Fourier results differ from Fourier theory only for small values of time. Comparing the temperature profiles and the solid-liquid interface location for aluminum, differences between the two theories were significant only for times on the order of 10−9–10−11 s and in a region within approximately 10−4–10−5 cm from the boundary surface. However, these results are based on an approximate value of the thermal relaxation time.
Heat Transfer and Fluid Flow Analysis of Interrupted-Wall Channels, With Application to Heat Exchangers
Authors: Sparrow E. M. , Baliga B. R. , Patankar S. V.
Published: November 2010

An analysis has been made of laminar flow and heat transfer in channels whose walls are interrupted periodically along the streamwise direction. Such channels are frequently employed in high-performance compact heat exchangers. Numerical solutions of the mass, momentum, and energy conservation equations yielded local heat transfer and pressure drop results. These results were obtained for a range of Reynolds numbers and for several values of a dimensionless geometrical parameter characterizing the streamwise length L of the individual plate segments which make up the interrupted walls. The Prandtl number was fixed at 0.7 for all the calculations. The basic heat transfer and pressure drop results were employed to investigate whether an interrupted-wall channel experiences an augmented heat transfer rate compared with that for a parallel plate channel. For conditions of equal heat transfer surface area and equal pumping power, appreciably higher heat transfer rates prevailed in the interrupted-wall channel for a wide range of operating conditions. The augmentation was especially marked for relatively short channels and high Reynolds numbers. The results also demonstrated the existence of a new type of fully developed regime, one that is periodic. At sufficiently large downstream distances, the velocity and temperature profiles repeat their values at successive axial stations separated by a distance 2L and, in addition, the average heat transfer coefficient for a plate segment takes on a constant value.
Performance Measurements of a Cylindrical Glass Honeycomb Solar Collector Compared With Predictions
Authors: McMurrin J. C. , Djordjevic N. A. , Buchberg H.
Published: November 2010

A glass tube honeycomb solar collector, composed of a conventional single-glazed flat-plate water cooled nonselective black absorber with a cylindrical glass honeycomb mounted between the plate and cover glass, was designed, fabricated, and tested. The test procedure followed the National Bureau of Standards Method of Testing for Rating Solar Collectors. The honeycomb consists of individual cylindrical thin-wall glass tubes standing on end on the absorber plate in a hexagonal close-packed pattern. The tubes are 9.5-mm ID, 0.2-mm wall thickness, 5.3 length to diameter ratio made of glass with mean solar absorptive index (k), 2.6 × 10−6 μ−1, evaluated from spectral transmittance-reflectance measurements on a tubing specimen. The collector performance equalled or surpassed theoretical predictions for measurements made over a broad range of collector inlet temperatures and environmental conditions. Performance comparisons are made with a baseline double-glazed solar collector tested alongside the honeycomb collector. For applications requiring a working fluid temperature of 65°C above the ambient air temperature, honeycomb collector efficiencies of 35–55 percent may be expected for approximately a six hour period on clear days; for fluid temperature 40° C above ambient air temperature, efficiencies of 50–65 percent may be expected.
Freezing-Controlled Penetration of a Saturated Liquid Into a Cold Tube
Authors: Epstein M. , Yim A. , Cheung F. B.
Published: November 2010

The penetration of a saturated liquid (a liquid at its freezing temperature) into a tube that is initially empty and maintained at a temperature below the freezing temperature of the liquid is treated theoretically and experimentally. A convenient approximate method is introduced which involves postulating a reasonable functional form for the instantaneous shape of the frozen layer along the tube wall. Graphical velocity-time and penetration distance-time curves are presented displaying the principal effects of a single dimensionless parameter. In the limit of negligible liquid inertia, shown to be relevant to high Prandtl number materials, a closed-form expression for the liquid penetration length is obtained. The expression compares well with the experimental results.
Established Stripwise Laminar Natural Convection On A Horizontal Surface
Authors: Boehm R. F. , Kamyab D.
Published: November 2010

A finite difference technique was used to analyze steady, laminar natural convection due to stripwise heating on an infinite, horizontal surface. The stripwise heating was accomplished by an array of alternately heated and unheated strips. Plots of the stream function and temperature field within a two-dimensional cell are given for a variety of heating and spacing configurations. From these results, the average Nusselt number was determined as a function of the Grashof number for a Prandtl number of 0.7. A plot of this dependence indicates diffusion, transition and plume modes exist, depending upon the value of the Grashof number. The present results are compared to previous experimental results for the same system, as well as results for uniformly heated surfaces. Higher heat transfer rates for the stripwise-heated surfaces compared to uniformly-heated surfaces are demonstrated for a wide range of Grashof numbers.
Hypersonic Viscous Shock Layer Calculation of Leeward Vortex-Induced Heat Transfer on a Sharp Cone at a High Angle of Attack
Authors: Adams J. C.
Published: November 2010

An analysis technique applicable to the problem of leeward vortex-induced heat transfer on a sharp cone at high angles of incidence under hypersonic laminar flow conditions is presented. The analysis, a three-dimensional hypersonic viscous shock layer approach in conjunction with a numerical solution procedure, is shown to be both applicable and accurate based on comparisons of heat-transfer distributions, surface pressure distributions, and leeward meridian flow-field profile measurements taken in a hypersonic wind tunnel. Detailed calculations of the embedded vortex flow field on the leeward side of the cone are presented in such a manner as to clearly portray exactly how embedded vortex flow influences local heating rates.
Incipient Boiling Characteristics at Atmospheric and Subatmospheric Pressures
Authors: Joudi K. A. , James D. D.
Published: November 2010

Experimental data are reported for incipient boiling of water, refrigerant R-113, and methanol from a flat horizontal stainless steel surface of known surface roughness. The work was carried out over a pressure range of 1, 0.5, and 0.25 atm. Overshoot temperatures at incipience for R-113 and methanol were systematically investigated and found to exist for all pressures employed. The overshoot in temperature at incipience did not occur for water within the experimental range covered. Surface temperature fluctuations were found to increase in amplitude with decreasing pressure, reaching a maximum at incipience. In general, these temperature fluctuations became less pronounced as fully developed nucleate boiling became established. An abnormal occurrence of transition from single-phase free convection to film boiling is also reported.
Mass Diffusion From a Point Source in a Neutral Turbulent Shear Layer
Authors: Rao K. S. , Nee V. W. , Yang K. T.
Published: November 2010

An investigation of the diffusion of pollutants in neutral surface layer of atmosphere is analyzed here based on a simple phenomenological differential field theory of turbulent shear flows. The variation of the effective turbulent viscosity is governed by a rate equation. The analytical model studied in this work consists of mass diffusion from a continuous crosswind point source at ground level in a turbulent shear layer. The system of governing equations is solved by finite-differences giving the pollutant distributions, eddy diffusivities, and velocity profiles at various downstream locations for various initial and boundary conditions. The computed diffusion data are presented and compared favorably with the available experimental results.
Numerical Predictions of Heat Transfer to Supercritical Helium in Turbulent Flow Through Circular Tubes
Authors: Schnurr N. M.
Published: November 2010

A numerical method is used to calculate heat transfer to supercritical helium in turbulent flow through circular tubes with constant wall heat flux. Comparisons of numerical predictions to experimental data showed good agreement. Numerical results were obtained for pressures from 2.5 to 20 atm and these results were correlated in terms of a heat flux parameter. A preliminary study of heat transfer in the thermal entry region showed the increase of the film coefficient to be larger for higher heat fluxes and for cases where the inlet bulk enthalpy was above the pseudocritical value.
Local Mass Transfer From Rotating Wedge-Shaped Blades
Authors: Koyama H. , Nakayama A. , Sato K. , Shimizu T.
Published: November 2010

The purpose of this investigation is to determine the mass transfer from rotating wedge-shaped blades in an air environment. Through theoretical considerations, effect of negative pressure gradient has been emphasized wherever possible. The experimental results are correlated with local Sherwood number and Reynolds number. Furthermore, a new method has been proposed to judge the flow type by reading directly the slope of contour lines of equal sublimation drawn on the surface.
Heat Transfer and Mean Structure of a Turbulent Thermal Plume Along a Vertical Isothermal Wall
Authors: Liburdy J. A. , Faeth G. M.
Published: November 2010

This investigation considers a two-dimensional turbulent thermal plume rising along a smooth vertical wall which is cooled to the ambient temperature. Mean velocity and temperature profiles within the plume, and the heat flux to the wall, were measured for various plume strengths and distances above the source. Integral analysis suggested an approach to local similarity, based on the local values of the thermal energy flux in the plume and the height above the source, at the limit of large Reynolds number where the local skin friction coefficient and Stanton number can be assumed to be nearly constant. The use of the local similarity hypothesis provided correlations for profiles of mean quantities, comparable to similarity correlations observed for other two-dimensional plumes. The wall plume was found to have greater velocities and temperatures than a free-line plume, in spite of direct losses to the wall. The local similarity hypothesis also provided a satisfactory correlation of wall heat transfer rates. The Nusselt number correlation is Nux=1.344Rax*0.18;2×1010<Rax*<6×1012 for Pr = 0.71. This expression is similar to correlations for turbulent natural convection with uniform heat flux, in fact, the present values are within 20 percent of the values found for natural convection with uniform heat flux for this range of Rax*.
Accurate Spectral Modeling for Infrared Radiation
Authors: Tiwari S. N. , Gupta S. K.
Published: November 2010

Direct line-by-line integration and quasi-random band model techniques are employed to calculate the spectral transmittance and total band absorptance of the 4.7 μ CO, 4.3μ CO2, 15μ CO2, and 5.35μ NO bands. Results are obtained for different pressure and path lengths. These are compared with available theoretical and experimental investigations. Total band absorptance values are available in the literature for certain pressure and path length conditions for these gases. Total absorptances have been calculated for the same physical conditions, employing line-by-line and quasi-random band models and the continuous correlations of Tien and Lowder, Cess and Tiwari, and Felske and Tien. In almost all cases, the line-by-line results are found to be in excellent agreement with the experimental values. The range of validity of other models are discussed.
Longitudinal Heat Propagation in Three-Phase Laminated Composites at High Exciting Frequencies
Authors: Horvay G. , Gold B. , Kaczenski E. S.
Published: November 2010

The performance of a laminated composite depends critically on the behavior of the interfaces. This behavior cannot be explored with the usual analysis which employs a smearing out of the temperature across the widths of the laminas, but requires a rigorous solution of the problem in the vicinity of the interfaces. This task can be accomplished by augmenting the usual bilaminate arrangement of matrix M and filler F with binder layers B (of volume fractions fM, fF, fB) into trilaminates MBFBMBF…and then considering the condition fB → 0. The unexpected result is obtained that for high exciting frequencies ω the case fB → 0 does not reduce to the case fB = 0. This thrusts into the foreground two questions: (a) What are the physical implications of such an “unreasonable” result? (b) What constitutes high frequency, what constitutes low frequency? The problem posed admits a rigorous solution.
Thermal Performance Deterioration in Crossflow Heat Exchanger due to the Flow Nonuniformity
Authors: Chiou J. P.
Published: November 2010

A mathematical method to determine the effectiveness of the crossflow heat exchanger accounting for the effect of two-dimensional nonuniform fluid flow distribution is presented. By using a successive substitution technique, the exchanger effectiveness and its deterioration due to the fluid flow nonuniformity effect have been calculated for four typical fluid flow maldistributions. A Flow Nonuniformity Factor has been developed as the principal parameter for predicting the degree of deterioration of the exchanger effectiveness.
Velocity Profiles near a Vertical Ice Surface Melting into Fresh Water
Authors: Wilson N. W. , Vyas B. D.
Published: November 2010

An experimental determination is made of the velocity profiles which result from the free convective melting of a vertical ice sheet into fresh water at temperatures in the range from 2.0°C to 7.0°C. The results suggest that upward flows exist for water temperatures below 4.7°C. Entirely downward flowing boundary layers are suggested for temperatures above 7.0°C. For intermediate temperatures, an oscillatory dual flow regime is indicated.
Molecular Gas Radiation in the Thermal Entrance Region of a Duct
Authors: Balakrishnan A. , Edwards D. K.
Published: November 2010

The effect of molecular gas radiation upon the thermal development downstream from a step change in wall temperature is examined for both laminar and turbulent flow in a black-walled flat-plate duct. The exponential-tailed band model is used to represent spectral variations in gas absorption and emission. Values of total and radiative Nusselt numbers, cold-wall-layer transmission factors, and dimensionless bulk temperatures are reported for several dimensionless axial locations and for various sets of the dimension-less controlling parameters. Even in the entrance region, self absorption by wall layer gas blocks significantly the radiation exchange between the gas core and wall. An approximate correlation is proposed for both plane-duct and pipe turbulent entrance flows.
Radiative Transfer in Hartmann MHD Flow
Authors: Smith T. F. , Paul P. H.
Published: November 2010

The high temperatures and gaseous products resulting from combustion of hydrocarbon fuels in magnetohydrodynamic generators have provided an impetus to develop more accurate methods for prediction of gas temperature profiles and heat fluxes at the generator walls. One area where an improvement may be realized is in the evaluation of radiative transfer between the gas and surrounding walls. Analyses and results are presented to examine the importance of the radiative transfer term appearing in the gas energy balance for classical Hartmann MHD flow. Results for both real (nongray) and gray gas radiative properties are presented. Inclusion of radiation is found to increase the surface heat flux as well as to alter gas temperature profiles. Furthermore, real gas results differ significantly from those for a gray gas.
Design and Load Rating Analysis of the Elastic Support for a Large Roller Bearing
Authors: Anderson W. D. , Dellinger C. L.
Published: November 2010

The Basic Oxygen Furnace comprises a tiltable vessel supported by two trunnions in large roller bearings. To accommodate thermal expansion, the floating bearing is mounted on a deep curved beam which moves axially on two linear bearings. Under loads of 1 to 2 million pounds, the elastic deflection of this beam alters the static load capacity of the roller bearing. This paper describes a computer assisted analysis based on Castigliano’s First Theorem for determining the effective bearing capacity, and secondly for optimizing the beam design.