Showing papers in "Journal of Heat Transfer-transactions of The Asme in 1960"
TL;DR: In this paper, a physical model for the bubble-flow regime of liquid-gas flow is proposed, where the mixture flows as a suspension of bubbles in the liquid, where radial gradients exist in the concentration of bubbles, and bubble concentration is assumed maximum at the center of the pipe, decreasing monotonically in a radial direction, and vanishing at the pipe wall.
Abstract: A physical model is proposed for the bubble-flow regime of liquid- gas flow which is in good agreement with the important features of the process. In this model it is conceived that the mixture flows as a suspension of bubbles in the liquid, where radial gradients exist in the concentration of bubbles. The bubble concentration is assumed maximum at the center of the pipe, decreasing monotonically in a radial direction, and vanishing at the pipe wall. An important concept introduced is that the gas and liquid have the same velocity at any radial position. The flow parameter assumes different forms for flow in circular pipes and for flow between two flat plates. (M.C.G.)
331 citations
293 citations
TL;DR: In this article, a graphical procedure was used to predict the heat transfer performance for combined natural and forced convection, based on experimental results, and compared with other investigations, including simulations.
Abstract: Experiments on heat transfer between spheres and airflow were carried out in the range of Reynolds numbers from 3.5to 1.44 x 10/sup 5/ and Grashof numbers from 1 to 10/sup 5/. Empirical formulas for forced, natural, and combined convection are presented and comparison made with other investigations. A graphical procedure, based on experimental results, is used to predict the heat- transfer performance for combined natural and forced convection. (auth)
264 citations
180 citations
TL;DR: In this article, the heat transfer problem of combined free and forced convection by a fully developed laminar flow in a vertical channel of constant axial wall temperature gradient with or without heat generations is approached by a new method.
Abstract: The heat-transfer problems of combined free and forced convection by a fully developed laminar flow in a vertical channel of constant axial wall temperature gradient with or without heat generations are approached by a new method. By introducing a complex function which is directly related to the velocity and temperature fields, the coupled momentum and energy equations are readily combinable to a Helmholtz wave equation in the complex domain. This greatly reduces the complexities of the problems. For illustrations, the cases of flows between parallel plates and in a rectangular channel are treated. Results show that this method is more direct and powerful than those of previous investigations. (auth)
162 citations
TL;DR: Theoretic equations governing steam slip effects in forced circulation of boiling water are derived in this article, which indicate that steam slip is dependent upon channel geometry, inlet water velocity, and rate of heat addition.
Abstract: Theoreticai equations governing slip effects in forced circulation oi boiling water are derived. The equations indicate that steam slip is dependent upon channel geometry, inlet water velocity, and rate of heat addition. A simplified momentam model is postulated which leads to equal friction and head losses of two phases. The model gives good agreement with available experimental results in horizontal and vertical test sections with and without heat addition at pressures from 12 to 2000 psia. Discussion of the model in terms of nonquasi steady-state unbalances of friction and head losses of the two phases explains experimental deviations from the predictions and the previously noted effects of water inlet velocity. It also gives trends for the effects of channel geometry and rate of heat addition. application of the simplified model to calculating two- phase pressure drops is included. (auth)
113 citations
TL;DR: In this article, the effectiveness and heat transfer coefficient of a film cooling system in which air was used both for the film and for the freestream fluids were investigated. But, as in past experience with such systems, separate specifications were needed for injection velocities greater and less than the free-stream velocity.
Abstract: Experimental results are presented for the effectiveness and heat- transfer coefficient of a film cooling system in which air was used both for the film and for the freestream fluids. Injection occurred at a single tangential slot near the leading edge of the plate, and the slot size was varied. All flows were turbulent, and the injection velocities covered a range from much less to much greater than the free-stream velocity. Correlations were realized for both the effectiveness and the heat-transfer coefficient and, as in past experience with such systems, separate specifications were needed for injection velocities greater and less than the free-stream velocity. (auth)
108 citations
83 citations
TL;DR: In this paper, local and average heat transfer coefficients and the temperatare field in the duct wall have been determined for the condition of constant heat generation per unit volume of the duct walls.
Abstract: Friction factors were measured for a duct whose cross section has the shape of an isosceles triangle witb a side ratio 5 to 1 in the fully developed now region ior laminar, transitional, and tarbulent conditions. In addition. local and average heat-transfer coefficients and the temperatare field in the duct wall have been determined for the condition of constant heat generation per unit volume of the duct walls. Friction factors in laminar flow agreed well with analytical predictions. In the turbulent flow range they were by 20 per cent lower than values calculated from relations for a round tube with the use of the "hydraulic diameter." Heat-transfer coefficients averaged over the circumference of the duct were only half as large as values calculated from round tube relations in the Reynolds number range from 4300 to 24,000. The measurements also revealed that thermal starting lengths were in excess of 100 diameters. In round tubes a length of 10 to 20 diame ters has been found sufficient to develop the temperature field. (auth)
77 citations
TL;DR: In this paper, a transducer originally devised for rapidly measuring high-intensity thermal radiation was adapted to measure the rate of heat transfer across the surface of a solid, and a thermocouple was obtained which measured directly the temperature difference of interest.
Abstract: A transducer originally devised for rapidly measuring high-intensity thermal radiation was adapted to measure the rate of heat transfer across the surface of a solid. This circular-foil heat-flow meter is designed so that a thermocouple is obtained which measures directly the temperature difference of interest. It differs from other transducers in that it is mounted in the body under study, not between the two media exchanging heat. Its small size permits the measured heat-flow rate to be associated with definite locations on the heat- transfer surface. (M.C.G.)
69 citations
TL;DR: In this paper, the constant property laminar boundary layer equations with free convection and mass transfer were considered and solutions to the equations in the form of skin fi- iction and heat-transfer parameters were presented for the constant wall temperature case for a fluid with Pr = 0.73.
Abstract: Consideration is given to the constant property laminar boundary layer equations with free convection and mass transfer. Similar solutions are possible for blowing rate distributions varying as the distance from the leading edge raised to the power (n -- 1)/4 where n is the exponent in a power law surface temperature distribution. Solutions to the equations in the form of skin fi- iction and heat-transfer parameters, and velocity and temperature profiles are presented for the constant wall temperature case for a fluid with Pr = 0.73. The cases considered range from strong suction to strong blowing. Mass transfer has a pronounced effect on the heat transfer but only a slight effect on the skin friction. In light of the solutions presented, these effects are shown to be physically rational. (auth)
TL;DR: In this article, a test facility is described that has been constructed to investigate local heat transfer and pressure drop for evaporating or condensing refrigerants, and the empirical method of B. Pierre [1] for correlating the average heat-transfer coefficients of refrigerants evaporating in horizontal tubes is presented in conjunction with the data of several authors.
Abstract: A test facility is described that has been constructed to investigate local heat transfer and pressure drop for evaporating or condensing refrigerants. The empirical method of B. Pierre [1] for correlating the average heat-transfer coefficients of refrigerants evaporating in horizontal tubes is presented in conjunction with the data of several authors [3–6]. Data on local heat-transfer coefficients and pressure drop are presented for Refrigerant-22 evaporating in two 4-ft-long, 0.343-in-ID straight horizontal tubes, and are correlated by a refinement of the curve proposed in [1]. The procedure of Martinelli-Nelson [9] correlated the data for local pressure drop within 15 per cent.
TL;DR: In this paper, the authors considered both black and diffuse gray-body radiation and obtained a simple relation between the two types of radiation, and solved the energy equation by three methods: use of a separable kernel, numerical integration, and variational methods.
Abstract: Thermal radiation was considered from the inside surface of a heated cylindrical enclosure. A specified heat input was imposed at the enclosure wall and the surface temperature distribution was determined. The analysis considered both black and diffuse gray-body radiation and obtained a simple relation between the two. The energy equation, a linear integral equation, was solved by three methods: use of a separable kernel, numerical integration, and variational methods. (auth)
TL;DR: In this article, a theoretical method for predicting the gap resistance is derived in terms of the fin and tube dimensions, their physical properties, the fluid temperatures and heat-transfer coefficients, and the initial contact pressure.
Abstract: Interference-fit finned tubes depend for their heattransfer capability upon a contact pressure between fin and tube. The bond resistance under such conditions is relatively small compared to the other resistances in the heatflow path. At elevated temperatures, however, differential thermal expansion between fins and tubes completely relaxes the contact pressure and introduces an additional gap resistance; this may become a significant part of the total resistance to heat transfer. A theoretical method for predicting the gap resistance is derived in terms of the fin and tube dimensions, their physical properties, the fluid temperatures and heat-transfer coefficients, and the initial contact pressure. Test data on five finned-tube units representing embedded, tension-wound, and muff-type fins are given in graphical and tabular form. Very good agreement is found between theory and test in two of the interferencefit units. The other two show only fair agreement. (auth)
TL;DR: In this paper, a variational method is presented for solving a class of integral equations which arise in radiation heat-transfer problems, and a system consisting of two nonblack, finite, parallel plates is considered.
Abstract: A variational method is presented for solving a class of integral equations which arise in radiation heat-transfer problems. First, to demonstrate the formulation of radiation problems in terms of integral equations, consideration is given to a system consisting of two nonblack, finite, parallel plates. After a general description of the variational method, its use is illustrated by application to the parallelplate system. Comparisons are made which show very good agreement with exact solutions. (auth)
TL;DR: In this article, the first-order deviations from the quasi-steady free convection heat transfer conditions were determined and a criterion developed to distinguish when heat transfer is essentially quasisteady.
Abstract: The first-order deviations from the quasi-steady free convection heat transfer conditions were determined and a criterion developed to distinguish when heat transfer is essentially quasi-steady. The system chosen for study was a vertical plate suspended in a gas. The surface temperature was spatially uniform but permitted to take on arbitrary, but continuously differentiable, variations with time. (M.C.G.)
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TL;DR: In this article, the results of an extensive experimental investigation of heat transfer to a turbulent incompressible boundary layer from a nonisothermal flat plate are summarizsd and extended the range of low-Mach-number confirmation of the von Karman analogy to Reynolds numbers of 4 x 10/sup 6/ for an isothermal plate.
Abstract: The results of an extensive experimental investigation of heat transfer to a turbulent incompressible boundary layer from a nonisothermal flat plate are summarizsd. Data presented extend the range of low-Mach-number confirmation of the von Karman analogy to Reynolds numbers of 4 x 10/sup 6/ for an isothermal plate. Data for a step wall-temperature distribution confirm experimentally the preferable expression for this important superposition kernel case. Data from a variety of other examples confirm the use of the superposition theories to predict heat transfer from nonisothermal surfaces. (auth)
TL;DR: In this paper, an analysis is made of the unsteady turbulent heat transfer in a circular tube whose wall temperature varies arbitrarily with time and the flow is steady and fully developed.
Abstract: An analysis is made of the unsteady turbulent heat transfer in a circular tube whose wall temperature varies arbitrarily with time. The flow is steady and fully developed. The formulation permits the heat-transfer coefficient to vary with time and position in accordance with the energy conservation principle. This is in contrast to previous transient analyses where it was standard to use steady-state, fully developed coefficients. The first step in the analysis yields the heat-transfer response to a step jump in wall temperaiure, and this is then generalized by a superposition technique to apply to arbitrary time variations. Use of the generalized results is illustrated by application to the case where the wall temperature varies linearly with time. Comparison is made between the unsteady heat-transfer results of the present theory and those computed using steady-state heat-transfer coefficients.
TL;DR: In this article, the Nusselt numbers for turbulent heat transfer in both the fully developed and thermal entrance regions of a circular tube are affected by two different wall boundary conditions.
Abstract: The purpose of this note is to examine in a more precise way how the Nusselt numbers for turbulent heat transfer in both the fully developed and thermal entrance regions of a circular tube are affected by two different wall boundary conditions. The comparisons are made for: (a) Uniform wall temperature (UWT); and (b) uniform wall heat flux (UHF). Several papers which have been concerned with the turbulent thermal entrance region problem are given. 1 Although these analyses have all utilized an eigenvalue formulation for the thermal entrance region there were differences in the choices of eddy diffusivity expressions, velocity distributions, and methods for carrying out the numerical solutions. These differences were also found in the fully developed analyses. Hence when making a comparison of the analytical results for uniform wall temperature and uniform wall heat flux, it was not known if differences in the Nusselt numbers could be wholly attributed to the difference in wall boundary conditions, since all the analytical results were not obtained in a consistent way. To have results which could be directly compared, computations were carried out for the uniform wall temperature case, using the same eddy diffusivity, velocity distribution, and digital computer program employed for uniform wall heat flux. In addition, the previous work was extended to a lower Reynolds number range so that comparisons could be made over a wide range of both Reynolds and Prandtl numbers.