bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Characteristics of Cavity Flow Past Cylindrical Inducers in a Venturi
Authors: Syamala Rao B. C. , Chandrasekhara D. V.
Published: November 2010

The characteristic dimensions of the steady cavity and the shedding frequency of vortices behind six circular cylinders in a two-dimensional venturi have been studied. The normalized length and maximum width of cavity for cavitation sources of different sizes indicated unified trends with a modified cavitation number km. The angles of detachment θ increased with cavitation number k and decreased with increasing Reynolds number R. The Strouhal number Sd reached minimum values for all cavitation sources at small values of k. The possible role of wall effects on the investigations are discussed.
Nonsimilarity Solutions for Cylindrical Blast Waves in Magneto-Gas Dynamics
Authors: Deb Ray G.
Published: November 2010

Nonsimilarity solutions in closed-form, for a sufficiently energetic line-explosion, in the presence of a constant axial current, are obtained. The gaseous medium is of constant pressure and its density varies as some inverse power of the distance from the line of explosion; ω is the power index, lying in the interval 0⩽ω<2. The disturbance is headed by cylindrical shock surface of variable strength. The total energy of the wave is non-constant, but can be made to vary slowly with time.
REVIEW—Progress in Numerical Turbomachinery Analysis
Authors: Japikse David
Published: November 2010

Progress achieved in numerical analysis during the past decade now permits the turbo-machinery designer to carry out a wide variety of inviscid, steady flow, two-dimensional calculations for compressible sybsonic and transonic flow fields, including some strongly diffusing flows. Three-dimensional (including viscosity) calculations are under development and should find wide spread use as analysis tools during the next decade. This review offers an introduction to recent advances in numerical turbomachinery design methods guided by the author’s design usage of several of the techniques reported.
Three-Dimensional Potential Flow and Effects of Blade Dihedral in Axial Flow Propeller Pumps
Authors: Howells R. , Lakshminarayana B.
Published: November 2010

A relatively simple and rapid method for predicting the three-dimensional flow effects in axial flow turbomachinery was investigated. Although the two-dimensional cascade is a satisfactory approximation for the design and analysis of some types of turbo-machines, the flow through devices, such as propeller pumps and inducers, may deviate significantly. A three-dimensional lifting surface theory was used to predict the potential flow around blades, represented by line vortices and sources, spanning an annulus. A rotor was designed, built, and tested (with air as the test medium) for comparison with the theory. Static pressure distributions on a rotating blade were measured. The effect of blade dihedral on these pressures was also measured. Deviation from cascade predictions caused by the three-dimensional flow effects is found to be appreciable for propeller pumps. No theory was developed, but variation of the experimental blade pressure distributions caused by dihedral was found to be considerable.
Pulsatile Blood Flow in a Channel of Small Exponential Divergence—III. Unsteady Flow Separation
Authors: Schneck Daniel J.
Published: November 2010

Analysis of pulsatile flow through exponentially diverging channels reveals the existence of critical mean Reynolds numbers for which the flow separates at a downstream axial station. These Reynolds numbers vary directly with the frequency of flow oscillation and inversely with the rate of channel divergence. Increasing the Reynolds number above its critical value results in a rapid upstream displacement of the point of separation. For a tube of fixed geometry, periodic unsteadiness causes flow separation to occur at lower Reynolds numbers and upstream of a corresponding steady-state situation. The point of separation moves progressively downstream, however, towards its steady-state location, as the frequency of oscillation increases. These results are discussed as consequences of the nonlinear steady streaming phenomenon described in an earlier paper.
A Model for High-Reynolds-Number Flow Past Rough-Walled Circular Cylinders
Authors: Gu¨ven O. , Patel V. C. , Farell C.
Published: November 2010

A simple analytical model for two-dimensional mean flow at very large Reynolds numbers around a circular cylinder with distributed roughness is presented and the results of the theory are compared with experiment. The theory uses the wake-source potential-flow model of Parkinson and Jandali together with an extension to the case of rough-walled circular cylinders of the Stratford-Townsend theory for turbulent boundary-layer separation. In addition, a semi-empirical relation between the base-pressure coefficient and the location of separation is used. Calculation of the boundary-layer development, needed as part of the theory, is accomplished using an integral method, taking into account the influence of surface roughness on the laminar boundary layer and transition as well as on the turbulent boundary layer. Good agreement with experiment is shown by the results of the theory. The significant effects of surface roughness on the mean-pressure distribution on a circular cylinder at large Reynolds numbers and the physical mechanisms giving rise to these effects are demonstrated by the model.
“IRIS” A Computerized High Head Pump Turbine Design System
Authors: Chacour S. , Graybill J. E.
Published: November 2010

“IRIS” is a computerized design and structural optimization system capable of generating all the major hydraulic and mechanical design parameters of high head pump/turbines from limited input data. The program will size the unit and select the proper hydraulic passage configuration according to performance requirements and optimize the dimensions of all the major components, generate command tapes used by a numerically controlled flame cutter, estimate cost, and issue manufacturing process planning. It also generates finite element models for the “in depth” analysis of critical components.
Constrained Flow Past Cavitating Bluff Bodies
Authors: Ramamurthy A. S. , Bhaskaran P.
Published: November 2010

An experimental program has been carried out to determine the effects of wall interference on the drag and vortex shedding characteristics of cavitating two-dimensional triangular prisms and circular cylinders. The former shapes were chosen to eliminate effects of Reynolds number in interpreting the results. Direct pressure measurements were made to estimate the drag force. The vortex shedding frequency of the cavitating bodies was recorded with the help of a pressure transducer. The gap velocity u1 and the jet contraction velocity uj are shown to be the proper velocity scales to form the drag coefficients and Strouhal numbers for the bluff shapes tested. The drag coefficient was found to increase due to wall interference effects when partial cavitation conditions prevailed. The trend of the drag coefficient data indicated that wall interference effects are relatively small at very low cavitation numbers (σ → σch) which correspond to choking conditions. As choking conditions are reached, the vortex shedding from the cavitating source becomes intermittent and finally vortex shedding ceases.
Analysis of Combined Free and Forced Convection for Fully Developed Laminar Flow in Horizontal Tubes
Authors: Newell P. H. , Bergles A. E.
Published: November 2010

This paper summarizes an analytical investigation of the effects of free convection on fully developed laminar flow in horizontal circular tubes with uniform heat flux. Solutions for heat transfer and pressure drop, with both heating and cooling, were obtained for water with two limiting tube-wall conditions. The infinite-conductivity tube exhibits higher Nu and f than the glass tube, with Nu being over five times the Poiseuille value at Gr ∼ 106. With the glass-tube boundary condition, significant circumferential wall temperature variations exist. A correlation for the difference between the wall temperatures at the top and bottom of the tube is presented. Design correlations for Nu and f are developed from the analytical solutions. The analytical predictions bracket recent experimental data for water.
Electron Heat Transfer in a Quiescent Nonequilibrium Plasma
Authors: McAssey E. V. , Yeh Hsuan
Published: November 2010

An asymptotic solution has been obtained for the electron heat transfer to a spherical body immersed in a weakly ionized, quiescent plasma. Dimensional analysis of the governing equations shows that the problem can be divided into two regions: charge-separated and quasi-neutral. For the charge-separated region, the equations must be solved numerically, whereas the quasi-neutral solution can be expressed in closed form. From these studies it was found that the extent of the charge-separated region (i.e, sheath) is of the order of Λ2/3. Within the sheath the effects of ionization and recombination are of the order of Λ4/3. The results include the variation of electron flux, electron heat transfer, and current as a function of body potential. The results are presented in a form to permit the easy determination of the electron heat transfer to a body immersed in a quiescent, weakly ionized plasma over a wide range of operating conditions. Furthermore, the electrical characteristics presented here can be used in conjunction with electron heating data to treat the body as a probe for diagnostic purposes.
The Effect of Thermal Conductivity of Plating Material on Thermal Contact Resistance
Authors: Mikic B. , Carnasciali G.
Published: November 2010

Plating of a base material of low thermal conductivity with materials of high thermal conductivity was considered. The solution for an elemental heat channel (single contact) is given. Experimental results for contact resistance of a plated single contact agreed well with the prediction. In general, results indicate that considerable reduction in thermal contact resistance can be achieved by plating; for example, stainless steel plated with copper of a thickness of the order of the contact size radius will reduce the resistance by more than an order of magnitude. A procedure is presented for extending the results for a plated elemental heat channel to the calculation of thermal contact resistance for nominally flat-plated surfaces in a vacuum.
Transient Free Convection in a Revolving Tube
Authors: Humphreys J. F. , Barrow H. , Morris W. D.
Published: November 2010

An experimental study has been made of transient free convection in a tube which revolves about an axis parallel to the tube axis. Three fluids have been studied for one tube diameter and one radius of rotation for centrifugal accelerations in the range 0 to 100g. The measurement of transient temperature and heat transfer coefficient shows that significant changes result from rotational buoyancy effects. A correlation of all the data to within ±20 percent has been effected by the use of a quasi-steady relation between a modified heat transfer coefficient and a rotational Rayleigh number as Nusseltnumber=0.107(Rayleighnumber)0.35
Approximate Optimum Fin Design for Boiling Heat Transfer
Authors: Cash D. R. , Klein G. J. , Westwater J. W.
Published: November 2010

For extended surfaces used in boiling liquids, the specified fin-base temperature may be such as to result in simultaneous nucleate, transition, and film boiling at adjacent positions on the fins. If the fins are spines of circular cross section, the optimum shape to minimize the volume of metal resembles a turnip, as shown by Haley and Westwater. The object of the new study was to develop easy-to-machine shapes using cones and cylinders. It was shown mathematically that two cones, base-to-base, give an excellent approximation to the turnip shape. Three such fins were constructed of copper and tested in Freon-113 at atmospheric pressure. The measured, peak heat duties were 5 to 70 percent higher than the predicted values, proving that the design method is conservative.
Heat Transfer From an Oscillating Horizontal Wire
Authors: Armaly B. F. , Madsen D. H.
Published: November 2010

The effect of vibration on heat transfer by natural convection has been investigated experimentally using a thin wire, 0.010 in. in diameter, and air as a convection medium. Horizontal reciprocating motion of varying amplitudes, peak-to-peak values of 0–2.655 in., and frequencies, 0–20 cps, was applied to an electrically heated horizontal wire. The average wire velocity (frequency times total path length traveled per cycle by the wire) was used to correlate and predict the experimental results.
Predictions of Flow-Level Angles in Two-Phase, One-Component Stratified Flow
Authors: Sarma P. K. , Sarma A. S. P. , Venkata Apparao K.
Published: November 2010

An analytical method is proposed to predict the flow-level angles under two-phase, one-component stratified flow in a horizontal tube with and without mass transfer. The analysis is restricted to adiabatic flow phenomena. A comparison of the present analysis with the available experimental data has revealed excellent agreement.
Cryo-Immunology: Surgical Approach and Thermal Regimen for Freezing the Elements of the Male Rabbit Reproductive System
Authors: Zappi E. , Shulman S.
Published: November 2010

The destructive freezing of living tissue often stimulates the host animal to produce antibodies against its own tissue. This phenomenon, the expression of an autoimmune process, is currently employed in this laboratory for exploring the antigenic properties of the male rabbit reproductive system. In this paper, the anatomic features of this reproductive system are briefly described. Details are offered of the surgical techniques used to approach these organs, and of the thermal regimes used in the destructive freezing of the target tissues.
An Experimental Technique for Determining the Diffusion Effect of Braze Material on the Thermal Conductance of Thin Copper Fins
Authors: Forslund R. P.
Published: November 2010

The purpose of this communication is to report on a successful technique for the measurement of thermal conductance in thin radiating fins. This work was required in the development of a lightweight radiator–condenser for the mercury Rankine cycle of the SNAP II program at Atomics International.
The Effect of Entrance Configuration on Local Heat-transfer Coefficients in Subsonic Diffusers
Authors: Stoffel E. O. , Welty J. R.
Published: November 2010

The effects of square and reentrant entrances on flow regimes (no “appreciable” separation, large transitory stall, and fully developed two-dimensional stall) and local heat-transfer coefficients were determined with air flowing through a symmetrical, plane-wall, two-dimensional subsonic diffuser with one of the diverging walls heated and maintained isothermal. Flow and heat-transfer studies were made for the following ranges: 2θ = 0 to 45 deg, L/W = 6 to 18, and Rextut = 4 × 104 to 3 × 105. Results indicated that 2θ, L/W, and entrance configuration greatly affected the flow regime and heat transfer. Equations relating Um′ to Ut, Ur to Ut, and equations of the type Nu = C Pr0.6Rex0.8 are presented. For the configurations tested, heat-transfer rates were greater for reentrant than for square entrances.
Stagnation-Point Heat Transfer: The Effect of the First Damko¨hler Similarity Parameter
Authors: Alkidas A. , Durbetaki P.
Published: November 2010

The present study considers the heat interaction between a combustible mixture and a constant-temperature surface near the stagnation region of a blunt body. The steady-state governing equations have been solved numerically for the case of Le = 1. A second-order Arrhenius law is assumed to describe the chemical kinetics of the mixture. The first Damko¨hler similarity parameter is shown to critically influence the surface heat transfer. The parameter represents a measure of the convective time to the chemical time.
The Effect of Thermal Radiation on Transient Vaporization of a Saturated Liquid at a Constant-Temperature Plate
Authors: Limpiyakorn C. , Burmeister L.
Published: November 2010

An analysis of the effect of thermal radiation on transient vaporization of a saturated liquid at a constant-temperature plate is presented. The realistic assumption of a constant-vapor-density–thermal-conductivity product gives results identical to the case in which all properties are constant. If radiation is neglected, identical coincidence with classical analytical results is found. With radiation considered, numerical solutions are obtained which are satisfactorily compared with data from the literature.
Solidification of a Semitransparent Cylindrical Medium by Conduction and Radiation
Authors: Habib I. S.
Published: November 2010

The effect of the radiative transport on the solidification rate and on the temperature distribution in a semitransparent cylindrical medium is investigated. The integral method is employed in the analysis, and results for the cases of absorbing, opaque, and nonparticipating media are presented. It is concluded that the radiative contribution to the process of phase change does have a significant effect on the solidification rate and on the temperature distribution in the solid phase.
Analysis of Real-Gas and Matrix-Conduction Effects in Cyclic Cryogenic Regenerators
Authors: Modest M. F. , Tien C. L.
Published: November 2010

The one-dimensional governing equations for the thermal performance of cryogenic regenerators are developed and simplified by neglecting gas conduction and pressure drop along the matrix. The present formulation includes the effects of matrix conduction and real-gas behavior, which can be quite important in actual situations but were neglected in all previous analyses. The time dependence of the governing equations is eliminated by integration over the compression and expansion periods. Numerical solutions of the resulting time-independent equations are presented for various values of physical parameters and temperature levels. Comparison with the corresponding cases neglecting real-gas and matrix-conduction effects demonstrates the significant nature of these effects for many operating conditions.
Study of the Laminar Free-Convection Wake Above an Isothermal Vertical Plate
Authors: Hardwick N. E. , Levy E. K.
Published: November 2010

The steady, laminar, two-dimensional wake above a thin vertical isothermal heated plate cooled by free convection was investigated theoretically and experimentally. The system of partial differential equations governing the fluid motion and heat transfer in the vicinity of the plate and in the near wake region was formulated and solved using finite difference techniques. Using air, the temperature and velocity profiles in the wake region were measured experimentally using a laser holographic interferometer and a constant temperature hot wire anemometer.
Conductance of Packed Spheres in Vacuum
Authors: Chan C. K. , Tien C. L.
Published: November 2010

An analytical study is presented for the heat transfer through the solid phase of a packed bed of spheres bounded by two infinite plane surfaces of different temperatures. The prediction of the conductance is based on the constriction resistance for spheres in contact. Both exact and approximate equations are derived for solid, hollow, and coated spheres and for several regular packing patterns of different void fractions. Comparisons with the available experimental data indicate that the theory is satisfactory over a wide range of applied load and system parameters.
Effect of Film Cooling Injection on Downstream Heat Transfer Coefficients in High Speed Flow
Authors: Wilson D. J. , Goldstein R. J.
Published: November 2010

An experimental and theoretical investigation was performed to examine the effect of film cooling injection from a two-dimensional slot on the downstream surface heat transfer. The coolant gas was ejected normal to the wall from a porous section on a flat plate under a supersonic Mack 3 mainstream. The mass velocity of injection was 1 percent to 2 percent of the mainstream value and resulted in decreases of 10 percent to 20 percent in the heat transfer coefficients near the slot. A simple theoretical model was formulated which accounted for the effect of the injection on thickening the boundary layer, and which accurately predicted the moderate decreases in heat transfer coefficients observed in the experiments.
Convective Heat Transfer From a Rotating Inner Sphere to a Stationary Outer Sphere
Authors: Maples Glennon , Dyer David F. , Askin Kerim , Maples Dupree
Published: November 2010

The convection heat transfer rate between a rotating, isothermal sphere and a concentrically located, isothermal outer sphere is experimentally determined for various Grashof and Reynolds numbers. A comparison of data with that for a single sphere rotating in an infinite media is given. The heat transfer rate for the single sphere is higher than for the concentric spheres at the same Reynolds number. The present experiment is shown to involve both free and forced convection heat transfer.
The Distortion of Turbulent Velocity and Temperature Profiles on Heating, for Mercury in a Vertical Pipe
Authors: Buhr H. O. , Horsten E. A. , Carr A. D.
Published: November 2010

Measurements were made in mercury, for turbulent flow and constant flux heating in a vertical pipe, in order to determine the extent to which the velocity and temperature distributions are affected by buoyancy forces. With increasing heat flux, velocity profiles at Reynolds numbers of 20,000 to 60,000 were found to be markedly distorted in comparison with the isothermal velocity profile. Even very low heat input caused significant distortion, while at high heat input a limiting profile shape was approached, with the center velocity well below the mean and the maximum occurring in the vicinity of the wall. Eddy diffusivities of heat and momentum calculated from the measured profiles exhibit a considerable variation with heat input, indicating that buoyancy forces not only change the radial shear stress distribution but also alter the nature of the turbulence in the pipe.
Application of Ambarzumian’s Method to Radiant Interchange in a Rectangular Cavity
Authors: Crosbie A. L. , Sawheny T. R.
Published: November 2010

Ambarzumian’s method had been used for the first time to solve a radiant interchange problem. A rectangular cavity is defined by two semi-infinite parallel gray surfaces which are subject to an exponentially varying heat flux, i.e., q = q0 exp(−mx). Instead of solving the integral equation for the radiosity for each value of m, solutions for all values of m are obtained simultaneously. Using Ambarzumian’s method, the integral equation for the radiosity is first transformed into an integro-differential equation and then into a system of ordinary differential equations. Initial conditions required to solve the differential equations are the H functions which represent the radiosity at the edge of the cavity for various values of m. This H function is shown to satisfy a nonlinear integral equation which is easily solved by iteration. Numerical results for the H function and radiosity distribution within the cavity are presented for a wide range of m values.
Modeling of Combustion Chambers for Predicting Pollutant Concentrations
Authors: Kennedy L. A. , Scaccia C.
Published: November 2010

This investigation presents the results of numerically modeling the combustion processes with a combustor. This furnace model consists of a rectangular chamber with rear and forward facing steps. The fuel and oxidizer are injected from two separate inlets. The swirl produced by the oxidizer inlet vanes in the actual physical situation is also modeled. The governing elliptical equations are solved numerically using a modified Gauss-Siedel procedure. Upwind differences are employed in the nonlinear convective terms to insure stability for all the Reynolds numbers considered. A parametric study to show the influence of the inlet conditions on the interior recirculation flow was performed. The burning of methane was studied within the model combustor with particular attention focused on the formation of nitrogen oxide and carbon monoxide. Stream lines, temperature, and concentration profiles are obtained within the combustor. The effect of inlet conditions on center-line profiles is discussed.
Toward a General Theory of Cutting: A Relationship Between the Incident Power Density and the Cut Speed
Authors: Bunting K. A. , Cornfield G.
Published: November 2010

A relationship between the power density incident on a material and the resulting cut speed is developed in terms of the thermal properties of the material. The expression obtained is general and is shown to be in good agreement with experimental results. It is shown that the efficiency of energy utilization is influenced by the incident power density and the jet diameter. The theory indicates that to maximize cut speed and energy utilization the jet diameter should be as small as possible consistent with an attainable power density.
Heat Transfer and Temperature Field Experiments in a Cavity With Rotation, Recirculation, and Coolant Throughflow
Authors: Sparrow E. M. , Buszkiewicz T. C. , Eckert E. R. G.
Published: November 2010

Local wall heat transfer coefficients and fluid temperature distributions were measured in a cavity consisting of a pair of parallel disks and a cylindrical shroud. One of the disks was rotating, whereas the other disk and the shroud were stationary. Coolant air entered the cavity through a central aperture in the rotating disk and exited through an annular gap at the rim of the rotating disk. The coolant flow rate, the disk rotational speed, and the cavity aspect ratio (disk separation distance to radius) were varied throughout the course of the experiments. The latter parameter took on values as large as two. The heat transfer results and the fluid isotherm maps suggested that the flow pattern within the cavity was markedly different depending upon whether the coolant stream or the pumping action of the rotating disk was predominant. The surface distributions of the heat transfer coefficients reversed the direction of their spatial variation over the range from no rotation to high rotation. However, the maximum values of the Nusselt number curves for no rotation were as high as the maximum values of the curves for corresponding cases with high rotation. The isotherm maps for the no-rotation cases revealed that the major portion of the cavity was filled with nearly isothermal fluid. On the other hand, in the presence of strong rotation, there were substantial fluid temperature variations throughout the cavity.
Nucleation Site Activation in Saturated Boiling
Authors: Shoukri M. , Judd R. L.
Published: November 2010

An experimental investigation is presented for the boiling of distilled degassed water at atmospheric pressure on a single copper surface with different surface finishes, in which the activation of nucleation cavities under the influence of different levels of heat flux was investigated. The measured active cavity radii showed good agreement with the active cavity radii predicted by the Hsu model. As a result of this investigation, it would appear that smaller cavities are better able to entrap vapor residue and be activated by their neighbors when boiling is initiated on the surface than larger cavities and that the reason for the relatively high levels of superheat at incipience commonly encountered is the nonexistence of sufficiently large cavities with the prerequisite residue of vapor. The correlation suggested by Brown relating the active site density (N/A)rc as a function of cavity radius rc in the form (N/A)rc α (1/rc)m was confirmed. On the basis of this work Griffith and Wallis’ recommendation that the parameter group [2σ Ts/ρv hfg (Tw − Ts)] be used to characterize a boiling surface was substantiated.
Heat Transfer in a Gray Planar Medium With Linear Anisotropic Scattering
Authors: Dayan A. , Tien C. L.
Published: November 2010

Radiative transfer in an absorbing and linearly-anisotropic scattering gray medium is analyzed. The medium is confined between plane parallel, gray, diffuse walls and contains uniform heat generation. The problem is formulated in terms of coupled integral equations with the intensity-moments as the unknown variables. The set of equations is solved both numerically and in closed form. The closed-form solution consists of exact limiting solutions and approximate general solutions obtained by the kernel-substitution method. The case of combined radiation and conduction is also treated. The results reveal clearly the effects of anisotropic scattering on important characteristics such as heat flux and incident radiant energy per unit area. The approximate closed-form solutions which predict quite well these effects are very simple and convenient to use for engineering calculations.
Natural Convection Mass Transfer Adjacent to Vertical and Downward-Facing Inclined Surfaces
Authors: Moran W. R. , Lloyd J. R.
Published: November 2010

Experimental measurements for natural convection mass transfer adjacent to vertical and downward-facing inclined surfaces were performed using an electrochemical technique. The measurements yielded the time average and instantaneous mass transfer rates for the laminar, transition, and turbulent flow regimes along the test surface. The laminar mass transfer measurements were found to agree with both the analytical and experimental results for both the vertical and downward-facing inclined surfaces. The Rayleigh number marking the onset of the transition from laminar flow conditions depended heavily upon the angle of inclination of the test surface. In the turbulent regime the time average local mass transfer coefficient was correlated by the Rayleigh number to 1/3 power.
Heat Transfer in Liquid-Coupled Indirect Heat Exchanger Systems
Authors: Holmberg R. B.
Published: November 2010

The theory of liquid-coupled indirect heat exchanger systems has been studied to ascertain optimum criteria with respect to the coupling-liquid flow rate and the distribution of total heat transfer area between the hot-side and cold-side exchanger units in the case of counterflow arrangement. The optimum coupling-liquid capacity rate is derived and given as a function of the over-all capacity rate ratio and the Ntu ratio between the two exchanger units. For this optimum liquid capacity rate together with the proposed over-all number of transfer units, it is shown that the over-all heat transfer effectiveness of the liquid-coupled system can be expressed in the ordinary form for individual exchanger units in true counterflow.
Some Effects of Mechanically-Produced Unsteady Boundary Layer Flows on Convective Heat Transfer Augmentation
Authors: Junkhan G. H.
Published: November 2010

Tests of experimental results from augmentation of convective heat transfer coefficients at a gas/solid interface by mechanical disruption of the boundary layer are discussed on both an average and a local basis. The averaged data show that the augmentation obtained depends upon the wake effects of the mechanical device used to produce the disturbance and upon the time required to re-establish the boundary layer after the disturbance has occurred. The local data analysis indicates that the amount of augmentation obtained depends on the relative velocity vector of the fluid with respect to the mechanical device and upon the time behavior of this vector.
Influence of System Pressure on Microlayer Evaporation Heat Transfer
Authors: Fath H. S. , Judd R. L.
Published: November 2010

Evaporation of the microlayer underlying a bubble during nucleate boiling heat transfer is experimentally investigated by boiling dichloromethane (methylene chloride) on an oxide coated glass surface using laser interferometry and high speed photography. The influence of system pressure (51.5 kN/m2—101.3 kN/m2) and heat flux (17 k W/m2—65 kW/m2) upon the active site density, frequency of bubble emission, bubble departure radius and the volume of the microlayer evaporated have been studied. The results of the present investigation indicate that the microlayer evaporation phenomenon is a significant heat transfer mechanism, especially at low pressure, since up to 40 percent of the total heat transport is accounted for by microlayer evaporation. This contribution to the overall heat transfer decreases with increasing system pressure and decreasing heat flux. The results obtained were used to support the model propounded by Hwang and Judd for predicting boiling heat flux incorporating microlayer evaporation, natural convection and transient thermal conduction mechanisms.
Film Boiling in a Scaling Liquid
Authors: Farrar L. C. , Marschall E.
Published: November 2010

Film boiling experiments were carried out in an aqueous-calcium sulfate solution. The experimental results indicate that scale formation on heating surfaces during evaporation of a calcium sulfate solution can be avoided under carefully controlled conditions. Experimental heat transfer results for both distilled water and aqueous calcium solutions compare very well with analytical predictions. In addition, for high heat fluxes, contact between liquid and heating surface was found to exist during stable film boiling in a quiescent, saturated or almost saturated liquid.
Adiabatic Wall Effectiveness of a Turbulent Boundary Layer With Slot Injection
Authors: Mayle R. E. , Kopper F. C.
Published: November 2010

An analysis is presented which extends the theoretical work of Weighardt and determines the adiabatic wall effectiveness of a turbulent boundary layer in a constant free-stream velocity flow heated or cooled by the discharge of a secondary fluid through a slot. A comparison of the analysis with the experimental results of Wieghardt is made and it is found that the streamwise decay in adiabatic wall effectiveness, except in the immediate region of the slot, may be explained by considering the thermal boundary layer growth within the hydrodynamic boundary layer.
The Near-Field Character of a Jet Discharged Normal to a Main Stream
Authors: Bergeles G. , Gosman A. D. , Launder B. E.
Published: November 2010

The paper reports an experimental study of the flow created by the injection of a circular jet of air at 90 deg through a plane wall past which an external stream is flowing. Particular attention has been given to obtaining details of the flow in the vicinity of the injection hole and upstream from the hole. These regions have been omitted, or received only slight attention in earlier studies of discrete-hole cooling processes. Four ratios of average injectant velocity: external velocity were chosen in the range 0.046–0.50. Even at the lowest injection rate there is still a clearly identifiable reverse flow region springing from the downstream side of the hole which extends approximately 0.3 dia downstream. The velocity distribution in the jet at discharge was found to be greatly affected by the presence of the external stream, more than 75 percent of the flow leaving from the downstream half of the discharge hole with a peak velocity in the jet approximately three times the average. Contour mappings of the surface isobars, show the upstream and lateral effects on the static pressure caused by the injection. In addition a number of flow visualization experiments help to reinforce the inferred character of the flow. Detailed film-cooling effectiveness data are reported which help delineate the near-wall flow structure.
Numerical Prediction of the Flow Field and Impingement Heat Transfer Caused by a Laminar Slot Jet
Authors: van Heiningen A. R. P. , Mujumdar A. S. , Douglas W. J. M.
Published: November 2010

The effects of uniform suction and nozzle exit velocity profile on the flow and heat-transfer characteristics of a semiconfined laminar impinging slot jet were investigated numerically. The full Navier-Stokes and energy equations were solved using a hybrid or upwind finite-difference representation of the equations cast into their vorticity-stream-function form. The importance of the nozzle exit profile is shown by comparison of the computed heat-transfer distribution with the available experimental data in the laminar range. Application of suction at the impingement surface is shown to enhance the local heat-transfer rates by a constant amount. The nondimensional heat-transfer coefficient and skin friction at the plate are computed as functions of the nozzle Reynolds number, the suction rate, and the nozzle velocity profile. The effect of temperature-dependent physical properties is included in the analysis.
Continuous Casting of Cylindrical Ingots
Authors: Sfeir A. A. , Clumpner J. A.
Published: November 2010

The Heat Balance Integral Method is applied to solve for the continuous casting of cylindrical ingots. Unlike previously developed integral solutions the present analysis includes the effect of axial conduction. Comparison with the solution derived by Veynick (which neglects axial conduction) shows that, for small Peclet numbers, the discrepancy between the results can be quite appreciable. In particular the pool depth prediction by the present analysis can be as much as 40 percent shorter. In its present form the method assumes constant temperature in the liquid metal and constant properties in the solidified crust. It is applicable to a variety of surface cooling rates including constant film coefficient, constant heat flux and other more general conditions. It can also take into account superheat of the molten metal.
Heat Conduction in an Anisotropic Medium Homogeneous in Cylindrical Regions—Unsteady State
Authors: Chang Y. P. , Tsou R. C. H.
Published: November 2010

A number of problems of heat conduction in an anisotropic medium of a monoclinic system which is homogeneous in circular cylinder coordinates are solved through the use of Green’s functions. Regions of solid and hollow cylinders, and an infinite region bounded internally by a cylindrical surface with boundary conditions of Dirichlet, Neumann, and mixed types are considered. Calculated results for two examples are shown, and the effects of material anisotropy on the temperature field are discussed. This paper is the first of a series to be reported in the open literature concerning the analytical solution for heat conduction in anisotropic media which are homogeneous in circular cylinder and rectangular coordinate systems.
Application of a K-ε Turbulence Model to Natural Convection From a Vertical Isothermal Surface
Authors: Plumb O. A. , Kennedy L. A.
Published: November 2010

A K-ε turbulence model similar to that proposed by Jones and Launder is applied to the calculation of the turbulent natural convective boundary layer on a vertical, isothermal surface. Conservation equations for the turbulent kinetic energy, dissipation rate of turbulent kinetic energy, and mean square temperature fluctuations are solved numerically along with the turbulent momentum and energy equations using the Spalding-Patankar boundary layer method. Various model constants and wall functions, and wall terms were tested. The results are compared with available experimental data and found to be in reasonable agreement.
Design Optimization of a Single Fluid, Solid Sensible Heat Storage Unit
Authors: Schmidt F. W. , Somers R. R. , Szego J. , Laananen D. H.
Published: November 2010

The optimization of the design of a solid sensible heat storage unit initially at a uniform-temperature is presented. The storage unit is composed of a number of rectangular cross-sectional channels for the flowing fluid, connected in parallel and separated by the heat storage material. The complex method for constrained nonlinear optimization as presented by M. J. Box is utilized, with some modifications. The design optimization is based upon achieving maximum utilization of the heat storage or removal capabilities of the material for a given set of operating conditions. This is achieved by varying the storage unit’s geometry while placing constraints on the maximum and minimum length of the unit, fluid channel size, storage material thickness, maximum and minimum outlet fluid temperature, and the minimum amount of heat to be stored.
Circumferential Variations of Bore Heat Flux and Outside Surface Temperature for a Solar Collector Tube
Authors: Sparrow E. M. , Krowech R. J.
Published: November 2010

An analysis is made of the heat transfer processes in a solar collector tube subjected to large circumferential heat flux variations on its outer surface. The analysis is carried out for a collector plate configuration in which the tubes are situated in embossments in the otherwise flat surface of the plate. The solar energy absorbed by the collector plate is conducted to the tubes and gives rise to large heat flux spikes at discrete circumferential locations on the outer surface of a tube. The two-region heat conduction problem encompassing the embossed portion of the collector plate and the tube is solved by a novel procedure which provides closed form solutions of high numerical accuracy. The influence of system dimensions, thermal properties, and tube bore convection is examined by means of five dimensionless parameters, of which the Biot number was found to be the most important. The results showed that for realistic dimensions and thermal properties of the plate and tube, circumferential variations of the outside surface temperature and bore heat flux can be neglected, provided that the tube flow is laminar. For turbulent flow conditions, the variations in bore heat flux are substantially greater than for laminar flow.
Numerical Solution of Transient Heat Conduction Equation for Heat-Treatable Alloys Whose Thermal Properties Change With Time and Temperature
Authors: Farnia K. , Beck J. V.
Published: November 2010

Changes in microstructure occur in as-received aluminum alloy (Al-2024-T351) when it is subjected to elevated temperatures (150–260°C). These changes, which are called precipitation hardening, in turn influence the thermal properties, making them time as well as temperature dependent. A computer-assisted transient experimental procedure has been developed to determine the values of thermal conductivity of as-received Al-2024-T351 under the influence of precipitation-hardening. Based on isothermal experimental data and related algebraic modeling of the thermal conductivity, a mathematical model in the form of two differential equations is proposed. Instantaneous values of volume fraction of precipitate and thermal conductivity can be predicted using this model. A method for the simultaneous numerical solution of the partial differential equation of conduction and the proposed differential equations of precipitation are also given. The influence of precipitation—hardening on temperature distribution and on values of thermal conductivity is shown graphically for several cases involving the Al-2024-T351 material.
Thermal Response of a Transpiration-Cooled System in a Radiative and Convective Environment
Authors: Kubota H.
Published: November 2010

The unsteady thermal response of a one-dimensional transpiration-cooled system in a radiative and convective environment is presented. The governing equations are solved by the Hartree-Womersley differential-difference method. The solid and fluid temperatures, the fluid pressure distributions, and the back-face heat transfer rate are obtained for a sample case of a 15 degree-entry into a Saturn nominal atmosphere.
Heat Transfer Between an Impinging Jet and a Rotating Disk
Authors: Metzger D. E. , Grochowsky L. D.
Published: November 2010

An experimental study of the flow interaction and heat transfer between a single impinging jet and a rotating disk is presented. Tests were conducted over a range of jet flowrates, impingement radii, and disk rotational speeds with various combinations of three jet and three disk sizes. Flow visualization using smoke addition to the jet flow reveals the presence of a flow regime transition which is correlated in terms of the rotationally induced disk pumping flow acting as a cross-flow influence on the jet. Higher rotational speeds, larger impingement radii, and smaller jet flowrates favor a rotationally dominated flow interaction whereas the opposite trends favor an impingement dominated interaction. Heat transfer rates are essentially independent of jet flowrate in the rotationally dominated regime, but increase, strongly with increasing flowrate in the impingement dominated regime.
Effect of an Elevated Pipeline on Moss Covered Ground Temperature
Authors: Mussulman R. L.
Published: November 2010

Elevated pipelines in cold regions will lose heat to the environment and raise the ground temperature below the pipe. The maximum temperature in the ground is the (steady) solution of Laplace’s equation with boundary condtions appropriate for summer months which are complicated by the insulating effects of mossy vegetation that grows in cold regions. A linear decomposition of the problem was accomplished to permit isolation of the thermal effects for the pipeline. That is, increases in ground and vegetation temperature due to the presence of the pipeline were obtained so that the environmental impact of a pipeline can be assessed.
Time-Dependent Double-Diffusive Instability in a Density-Stratified Fluid along a Heated Inclined Wall
Authors: Chen C. F.
Published: November 2010

We consider a stably stratified fluid contained between two parallel sloping plates. At t = 0, the lower plate is given a step increase in temperature; a time-dependent convective flow is generated. Stability of such a flow with respect to double-diffusive mechanism is analyzed. The method is the same one used by Chen [6] in treating a similar problem with vertical walls. The predicted critical values of Rayleigh number and wavelength compare favorably with those observed experimentally. No overstability is encountered up to 75 deg of inclination of the heating wall to the vertical. For a horizontal layer, however, instability starts in an overstable mode. The frequency of the overstable mode compares favorably with that predicted by Veronis [7] for a free-free layer.
Boundary Layer Closure and Heat Transfer in Constant Base Pressure and Simple Wave Guns
Authors: Anderson A. D. , Dahm T. J.
Published: November 2010

Solutions of the two-dimensional, unsteady integral momentum equation are obtained via the method of characteristics for two limiting modes of light gas launcher operation, the “constant base pressure gun” and the “simple wave gun”. Example predictions of boundary layer thickness and heat transfer are presented for a particular 1 in. hydrogen gun operated in each of these modes. Results for the constant base pressure gun are also presented in an approximate, more general form.
Thermal Diffusivity of Dispersed Materials
Authors: Lee T. Y. R. , Taylor R. E.
Published: November 2010

Measurements have been made of the effective thermal diffusivity at room temperature of composites consisting of one phase randomly dispersed in a second phase. The method is based on the flash technique. Data are presented for four types of composites ranging in particle-to-matrix diffusivity ratios from 0.48 to 1137, in volume specific heat ratios 0.04 to 1.16, and in volume fraction of dispersed particle from zero up to 34 percent. The results show that the limitations of the concept of an effective thermal diffusivity are far beyond the situations to which it is currently applied in the transient state heat conduction problems. Values of effective diffusivities derived from values of the effective thermal conductivity calculated from the Bruggeman variable-dispersion equation are found to agree well with the measured diffusivity values.