J. Heat Transfer 92, 307-332 (1970) (26 pages);   doi:10.1115/1.3449667

The vertical motion of balloon systems depends critically on the heat transfer to and from the gas inside because the temperature and pressure of the gas determines the lift of the balloon and its payload. In the past the thermal design of high-altitude balloons has largely been based on a combination of experience, empirical data, and approximate calculations. Recent advances in heat-transfer research have made it possible, however, to calculate the temperature of the lifting gas as a function of altitude and to predict the vertical motion with the aid of high-speed computers. This review presents the results of heat-transfer experiments and theory pertinent to the processes which affect the calculations of balloon performance and the thermal design of their instrument packages.

J. Heat Transfer 92, 333-344 (1970) (12 pages);   doi:10.1115/1.3449668

Boundary layer and heat transfer measurements are presented for flow through a cooled, conical nozzle with a convergent and divergent half-angle of 10 deg for a wall-to-total-gas temperature ratio of about 0.5. A reduction in heat transfer below values typical of a turbulent boundary layer was found when values of the parameter K = (μe /ρe ue2) (due /dx) exceeded about 2 to 3 × 10−6 . The boundary layer measurements, when viewed in conjunction with the heat transfer measurements, reveal the complicated nature of the flow and thermal behavior and their interrelationship when laminarization occurs.

J. Heat Transfer 92, 345-350 (1970) (6 pages);   doi:10.1115/1.3449669

Heat transfer to supercritical water (at 3400 psia in the pseudocritical region) by stable laminar free convection from an isothermal, vertical flat plate was analytically investigated. The actual variations with temperature of all or some of the thermophysical properties of supercritical water were taken into consideration. Fair agreement was found between the analytical values of this paper and existing experimental data.

J. Heat Transfer 92, 351-358 (1970) (8 pages);   doi:10.1115/1.3449670

The effects of surface tension and buoyancy on the convection stability of fluid layers with a mean parabolic temperature distribution is examined. A variety of free-surface, thermal boundary conditions are used. Quantitative values for the effect on the critical Rayleigh number of the free-surface boundary condition, fluid depth, and physical properties are given. The role of the mean temperature profile is also discussed. The results should be of value in judging experiments where a free surface is used to enhance the flow visualization. The numerical procedure used to find the eigenvalues was effective and easily altered to obtain results for similar stability problems.

J. Heat Transfer 92, 359-371 (1970) (13 pages);   doi:10.1115/1.3449671

Major differences exist in results published by investigators of film condensation of liquid metal vapors. In particular, the reported dependence of the condensation coefficient on pressure has raised questions about both the precision of the reported data and the validity of the basic interphase mass transfer analysis. An error analysis presented in this investigation indicates that the reported pressure dependence of the condensation coefficient at higher pressures is due to an inherent limitation in the precision of the condensing wall temperature measurement. The magnitude of this limitation in precision is different for the various test systems used. The analysis shows, however, that the primary variable affecting the precision of the wall temperature measurement is the thermal conductivity of the condensing block. To verify the analysis, potassium was condensed on a vertical surface of a copper condensing block. The copper block was protected from the potassium with nickel plating. Condensation coefficients near unity were obtained up to higher pressures than those previously reported for potassium condensed with stainless steel or nickel condensing blocks. These experimental results agree with the prediction of the error analysis. In addition, a discussion of the precautions used to eliminate the undesirable effects of both noncondensable gas and improper thermocouple technique is included. It is concluded from the experimental data and the error analysis that the condensation coefficient is equal to unity and that the pressure dependence reported by others is due to experimental error.

J. Heat Transfer 92, 372-384 (1970) (13 pages);   doi:10.1115/1.3449672

A theory for the heat transfer to the stagnation point of a hemisphere in a supersonic, high-enthalpy, low-density nitrogen plasma flow was developed. The theory assumed a flow that is frozen with respect to molecular dissociation and relaxing with respect to ionization. The calculations for this partially frozen flow yielded heat-transfer rates that were generally lower than predicted by other theories for both frozen and equilibrium flows. Experimental heat-transfer rates from measurements in a high-enthalpy constricted-arc tunnel agreed with the theoretical value within 10 percent in the mean.

J. Heat Transfer 92, 385-392 (1970) (8 pages);   doi:10.1115/1.3449673

The present study was performed in order to determine the effects of upstream mass injection on downstream heat transfer in a reacting laminar boundary layer. The study differs from numerous previous investigations in that no similarity assumptions have been made. The complete set of coupled reacting laminar boundary layer equations with discontinuous mass injection was solved for this problem using an integral-matrix technique. The effects of mass injection on heat transfer to both sharp and blunt-nosed isothermal flat plates were studied for a Mach 2 freestream. The amount of injection and the length of the injected region were varied for each body. Heat transfer rates were found to decrease markedly in the injected region. A sharp rise in heat transfer was found immediately downstream of the region of injection followed by an asymptotic approach to the heat transfer rates calculated for the case of no injection. An insulating effect was found to persist for a considerable distance downstream from the injection region. The distance required for this insulating effect to die out was found to depend on the length of the injection region as well as the rate of injection.

J. Heat Transfer 92, 393-398 (1970) (6 pages);   doi:10.1115/1.3449674

A quantitative picture of the effect of low-temperature exposure on the survival of living cells is presented through discussion of solutions to a differential equation relating the volume of intracellular water to the temperature, the cooling rate, and various cell parameters. It is found that for a given cell, a single parameter which depends on the cooling rate governs the behavior of the cell when it is exposed to low temperatures. The analysis develops relationships between solutions to the differential equation and the phenomena affecting cell survival, namely, intracellular freezing and cell dehydration. Theoretical predictions are found to agree well with existing experimental observations.

J. Heat Transfer 92, 399-404 (1970) (6 pages);   doi:10.1115/1.3449675

The radiative transfer between two infinite parallel metallic surfaces separated by a nonconducting ideal dielectric is calculated on the basis of electromagnetic wave theory. The solution is restricted to the case of large spacing (thick film) wherein the effects of interference and radiation tunneling can be neglected. The optical properties of the metals are predicted via the anomalous skin effect theory, the Drude single electron theory and the Hagen-Rubens relation. A comparison of the predicted radiative fluxes indicates the large disparities which result from the three different specifications of the optical properties of metals. For practical applications at cryogenic temperatures, approximations are obtained for the thick film solution using the anomalous skin effect theory of the optical properties.

J. Heat Transfer 92, 405-411 (1970) (7 pages);   doi:10.1115/1.3449676

An attempt is made on the basis of electromagnetic theory to predict spacing effects on the radiative transfer between two closely-spaced, semi-infinite metals separated by a nonconducting dielectric. Electromagnetic energy transmission factors are derived for a general, three-medium system and their simplification for the metal-dielectric-metal system is shown. The net energy flux is calculated with these transmission factors and the estimated intensities in the metals. Numerical results are given which exhibit the effects of metal spacing, metal type, temperature level, and type of dielectric. Variations in the heat flux of several orders of magnitude are shown to exist in a system whereas the Stefan-Boltzmann relation indicates a constant flux, independent of spacing.

J. Heat Transfer 92, 412-416 (1970) (5 pages);   doi:10.1115/1.3449677

Experimental measurements of the radiative heat flux between two parallel copper disks in the liquid-helium temperature range are presented. The temperature levels investigated were primarily for the higher temperature disk (emitter) at 10.0 deg K and 15.1 deg K and the lower temperature disk (receiver) at approximately 4.5 deg K. For the 15.1 deg K emitter temperature, the spacing was varied from 0.201 cm to 0.001 cm. For the 10 deg K emitter case, the spacing was varied from 0.044 cm to 0.005 cm. Experimental data at small spacings show a definite spacing dependence of radiative transfer which agree qualitatively with the predicted result. Based on the measurements at large spacings, an estimate of the total hemispherical emissivity for the copper surfaces in the liquid-helium temperature range indicates a value of 0.015, which is approximately one order of magnitude higher than predicted. The possible causes for the discrepancies are discussed.

J. Heat Transfer 92, 418-428 (1970) (11 pages);   doi:10.1115/1.3449680

Consideration is given to dispersed systems in which the particle behavior is a function of systematic motion. The following phenomena governing the movement of the particles are analyzed from the channel entrance: convective effects, translation due to gravity, fluid drag, and circulation induced by the flow. External lateral forces and mutual particle interactions are not considered. Results are obtained for the magnitude and overall effects of the lateral force due to circulation around the particles. The analysis is closely related to the author’s measurements of the deposition of micron-size water droplets in adiabatic vertical flow.

J. Heat Transfer 92, 429-437 (1970) (9 pages);   doi:10.1115/1.3449681

The effect of mechanical vibrations on natural convective heat transfer in an enclosure of rectangular cross-section was investigated experimentally. The enclosure was comprised of two vertical and opposed surfaces which were maintained at different temperatures, surrounded by four other adiabatic surfaces. Vibration stresses were applied to this heat transfer cell by mounting it vertically on the armature of an electrodynamic vibrator. Frequencies from 0 to 4000 Hertz and accelerations from 0 to 110 g’s were utilized in the investigation. The results show that vibration of a thermally active enclosure can have a significant effect on its heat transfer characteristics especially near the resonant natural frequency of the column of fluid contained within the enclosure. Increases in convective heat transfer coefficients of as much as 50 percent were obtained during this investigation. A correlation equation was developed by utilizing the dynamic response characteristics of the fluid column when considered as a seismic mass.

J. Heat Transfer 92, 439-445 (1970) (7 pages);   doi:10.1115/1.3449684

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

J. Heat Transfer 92, 447-455 (1970) (9 pages);   doi:10.1115/1.3449688

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.

J. Heat Transfer 92, 456-464 (1970) (9 pages);   doi:10.1115/1.3449689

The theory of moving heat sources is applied to two models to determine the effect of convective surface cooling on temperature distributions. The models chosen consist of a translating semi-infinite body and a rotating cylindrical body, each having a band heat source acting on a portion of the surface and convective cooling acting over the entire surface. The analytical results can be utilized to predict temperature distributions occurring in certain machining processes or other processes involving heat sources.

J. Heat Transfer 92, 465-471 (1970) (7 pages);   doi:10.1115/1.3449690

An investigation has been made of the factors governing the heat transfer coefficient to supercritical pressure fluids, particularly at high heat fluxes. The deterioration in heat transfer to supercritical carbon dioxide has been experimentally studied with reference to the operating conditions of mass velocity and heat flux, tube diameter, orientation, tape induced swirl, inlet temperature, and pressure. A detailed comparison has been made with the apparently contradictory results of other investigators, and operating regions, in which the heat transfer coefficient behaves differently, have been defined. The terms used to describe these regions are the Reynolds number, a heat-flux parameter, and a free-convection parameter.

J. Heat Transfer 92, 475-481 (1970) (7 pages);   doi:10.1115/1.3449694

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.

J. Heat Transfer 92, 483-489 (1970) (7 pages);   doi:10.1115/1.3449697

Heat transfer data are reported for partially ionized argon flowing in a water-cooled circular tube, 1/2 in. in dia. Experiments were run with initial mixed-mean temperatures up to 21,000 deg R at Reynolds numbers from 140–527 based on equilibrium properties evaluated at the entrance mixed-mean temperature. Measured plasma flow Nusselt numbers computed on an enthalpy basis correlate well with low temperature, constant property results after the first 5–10 diameters of the tube entrance region; closer to the entrance, Nusselt numbers were about 30 percent higher than constant property entrance region predictions. The tendency of the data to approach the constant property solution rapidly was predicted by a laminar finite-difference analysis for plasma flow published earlier [1]. The analysis was modified for the present study to improve its accuracy. The finite-difference theory under predicts the heat transfer in the first few tube diameters; two possible reasons for this discrepancy are the poor resolution in the inlet enthalpy profiles near the tube wall and nonequilibrium between electrons and heavy particles in this region.

J. Heat Transfer 92, 490-497 (1970) (8 pages);   doi:10.1115/1.3449698

Investigations of heat transfer to supercritical pressure fluids have been going on for some time, and correlations have been developed for both free and forced-convection conditions. In these investigations, unpredictable heat transfer performance has sometimes been observed when the pseudocritical temperature of the fluid is between the temperature of the bulk fluid and that of the heated surface. The unusual performance has been attributed to many causes, but one for which more evidence is being collected is that of a pseudofilm-boiling process similar to film boiling which occurs at subcritical pressures. This paper, which is an extension of work reported earlier on forced-convection heat transfer to supercritical pressure water, presents experimental evidence which suggests that a pseudofilm-boiling phenomenon can occur in smooth-bore tubes. During the period from 1963–1966, tubes with ID’s from 0.37 to 0.96 in. were tested at pressures from 3300–6000 psia and at heat fluxes and mass velocities in the range of interest in steam-generator design. The effects of heat flux, mass velocity, tube diameter, pressure, and bulk fluid temperature on both the occurrence and characteristics of pseudofilm boiling are discussed. Results of a second series of tests conducted in 1967, which show that ribbed tubes suppress pseudofilm boiling at supercritical pressure much like they do film boiling at subcritical pressures, are also discussed.

J. Heat Transfer 92, 499-505 (1970) (7 pages);   doi:10.1115/1.3449701

Experimental heat transfer data are presented for a series of asymptotic accelerated turbulent boundary layers for the case of an impermeable wall, and several cases of blowing, and suction. The data are presented as Stanton number versus enthalpy thickness Reynolds number. As noted by previous investigators, acceleration causes a depression in Stanton number when the wall is impermeable. Suction increases this effect, while blowing suppresses it. The combination of mild acceleration and strong blowing results in Stanton numbers which lie above the correlation for the same blowing but no acceleration. Velocity and temperature profiles are presented, from which it is possible to deduce explanations for the observed behavior of the Stanton number. A prediction scheme is proposed which is demonstrated to quite adequately reproduce the Stanton number results, using correlations derived from the profiles.

J. Heat Transfer 92, 506-512 (1970) (7 pages);   doi:10.1115/1.3449702

The results of a primarily experimental study of the transition from turbulent flow to laminar flow as a consequence of high heating rates are presented. Results are reported for hydrodynamically fully developed, low Mach number flows of air and helium through a vertical, circular tube. The electrically heated section was 100 diameters in length; entering Reynolds numbers ranged from 1700–40,000, and maximum wall-to-bulk temperature ratios reached 4.4. As a means of predicting the occurrence of a transition from turbulent flow to laminar flow, the experimental results are compared to the acceleration parameter suggested by Moretti and Kays and to a modified form of the parameter that is appropriate to a circular tube. It is suggested that the variable property turbulent flow correlations do not provide acceptable predictions of the Nusselt number and the friction factor if the value

4μq′′G2DTcp ≃ 1.5 × 10−6
based on bulk properties, is exceeded for an initially turbulent flow situation. It is further suggested that Nusselt numbers and friction factors at locations down-stream from the point
xDlaminar ≃ (2 × 10−8)(Tinlet)
  (Reb, inlet)2 TwTbmax−1
for bulk temperatures in degrees Rankine may be obtained from the laminar correlation equations even though the flow is initially turbulent.

J. Heat Transfer 92, 513-518 (1970) (6 pages);   doi:10.1115/1.3449703

Heat transfer and pressure-drop experiments have been performed for gas flow inside nine, 1/2 -in-OD, 0.035-in. wall thickness, A-nickel, spirally corrugated tubes. The corrugations, which varied from 0.003–0.028 in. deep, were formed by pulling the tubes through a rotating head containing four embossing tools; corrugation-spacing-to-corrugation-depth ratios (P/e) ran from 16–41. The data, for heat transfer to nitrogen, at approximately 200 psig, were correlated by an expression of the form NNu ,B (NPr ,B )−0.4 × (Tw /TB )0.5 = A(NRe ,B )m , where all the physical properties were evaluated at bulk gas conditions. The exponent, m, on the Reynolds number was observed to be consistently greater (0.854–0.900) than the value of 0.8 found for smooth tubes; the constant, A, varied from 0.0095–0.0195 with no apparent correlation with P/e. Friction factors, measured with adiabatic airflow, were found to be up to 1.7 times that for smooth tubes. Tubes of this geometry were found to be very effective in enhancing heat transfer. On an equal pumping power basis, for example, a tube with P/e = 22 had a heat transfer coefficient 22 percent greater than a smooth tube.

J. Heat Transfer 92, 520-527 (1970) (8 pages);   doi:10.1115/1.3449707
J. Heat Transfer 92, 528-535 (1970) (8 pages);   doi:10.1115/1.3449708

A method has been developed for coupling conduction in a solid with natural convection in a surrounding fluid. The problem investigated is that of steady, constant-property, two-dimensional, laminar natural convection from a vertical, heat-conducting flat plate of finite thickness with an arbitrary heating distribution in its surface. Using this method it is possible to predict the variation of temperature in the plate and the velocity and temperature profiles in the boundary layer as a function of the heating distribution and the thermal properties of the plate and fluid. The equations for conduction in the plate and convection in the boundary layer are written in finite difference form, coupled through the common heat flux at the plate-fluid interface, and solved numerically by an iterative technique. Experimental corroboration of the numerical results is provided by measuring temperatures, both with thermocouples and a laser holographic interferometer, along ceramic and glass plates heated by thin film resistance heating elements vacuum deposited on their surface. The results indicate that the degree of coupling between conduction in the plate and natural convection in the fluid is greatly influenced by the plate-fluid conductivity ratio.

J. Heat Transfer 92, 536-540 (1970) (5 pages);   doi:10.1115/1.3449709

Large amplitude acoustical pressure oscillations can be generated in a gas by a steady heat addition. The thermoacoustical oscillation known as the Sondhauss oscillation occurs in a pipe having only one closed end. Experiments were performed to determine thermoacoustic oscillator characteristics for different system geometries and for different operating conditions. Based on these experimental studies, a physical explanation of the mechanism causing Sondhauss thermoacoustical oscillations is presented. The driving mechanism consists of two separate components, that of driving by simple thermal expansion, and that of expansion by the mixing of hot and cold gas in the pipe. The initiation of the oscillations is discussed. Thermoacoustic oscillation phenomena are shown to be analogous to the interaction occurring in a regenerative heat engine, where a steady heat input causes an oscillating mechanical energy output. A comparison of experiment and generalized theory is presented.



J. Heat Transfer 92, 542-544 (1970) (3 pages);   doi:10.1115/1.3449713
Topics: Sound , Boiling
J. Heat Transfer 92, 546-548 (1970) (3 pages);   doi:10.1115/1.3449715
J. Heat Transfer 92, 548-550 (1970) (3 pages);   doi:10.1115/1.3449716
J. Heat Transfer 92, 550-553 (1970) (4 pages);   doi:10.1115/1.3449717
J. Heat Transfer 92, 553-555 (1970) (3 pages);   doi:10.1115/1.3449718
J. Heat Transfer 92, 555-556 (1970) (2 pages);   doi:10.1115/1.3449719
J. Heat Transfer 92, 557-558 (1970) (2 pages);   doi:10.1115/1.3449720
J. Heat Transfer 92, 558-559 (1970) (2 pages);   doi:10.1115/1.3449721
J. Heat Transfer 92, 559-562 (1970) (4 pages);   doi:10.1115/1.3449722
J. Heat Transfer 92, 562-564 (1970) (3 pages);   doi:10.1115/1.3449723
Topics: Temperature , Shapes
J. Heat Transfer 92, 565-567 (1970) (3 pages);   doi:10.1115/1.3449725

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