Warren M. Rohsenow

An investigation of heat transfer and friction for rib-roughened surfaces

Abstract An investigation of rib-roughened surface was undertaken to determine the effects of rib shape, angle of attack and pitch to height ratio on friction factor and heat-transfer results. A parallel plate geometry was used. Based on the law of the wall similarity and the application of the heat-momentum analogy developed by Dipprey and Sabersky, a general correlation for friction factor and heat transfer was developed to account for rib shape, spacing and angle of attack. Ribs at a 45° angle of attack were found to have superior heat transfer performance at a given friction power when compared to ribs at a 90° angle of attack or when compared to sand-grain roughness.

On bubble growth rates

A simple general relation for bubble growth rates in a uniformly superheated liquid was derived. The relation is valid in both regions: inertia controlled and heat diffusion controlled growth, respectively. The derived relation is compared with the existing experimental results for bubble growth in a uniformly superheated liquid with very good agreement. The results are further extended to the bubble growth in a non-uniform temperature field which approximates the conditions present in a nucleate boiling from a heated surface.Abstract A simple general relation for bubble growth rates in a uniformly superheated liquid was derived. The relation is valid in both regions: inertia controlled and heat diffusion controlled growth, respectively. The derived relation is compared with the existing experimental results for bubble growth in a uniformly superheated liquid with very good agreement. The results are further extended to the bubble growth in a non-uniform temperature field which approximates the conditions present in a nucleate boiling from a heated surface.

Correlation of forced convection boiling heat transfer data

Abstract The method of superposition for correlating forced convection boiling heat transfer data is extended to cover subcooled to high quality ranges using single phase and two phase forced convection equations, a pool boiling equation, and an incipient boiling criterion. Only one empirically determined coefficient is needed. Agreement with water data is better than that provided by the Chen correlation.

Dispersed flow heat transfer

Abstract An experimental and theoretical analysis of the dispersed flow heat transfer has been performed. The transient experimental technique included a long tubular preheater section for creating a dispersed flow and a short tubular transient test section for collecting the heat-transfer data (heat flux vs wall superheat data). Liquid nitrogen was used as a test fluid. The mass velocities varied from 80 to 300 kg/s m2. The theoretical study included: the analysis of the structure of a dispersed flow (the analysis of a drop size and drop size distribution); the analysis of the deposition motion of liquid drops (the migration of drops toward the wall); the analysis of the possible successive states of drop-wall interaction, and heat transfer to a drop deposited on the heated wall. Based on the above analyses the expression for the heat flux from the wall to dispersed flow has been developed and it has given good agreement with the experimental data.

Condensation heat transfer in the presence of a non-condensable gas

Abstract Potassium vapor is condensed in the presence of various total amounts of argon or helium as non-condensable gases. It is shown that the rate of condensation is governed by the ordinary molecular diffusion equations, the effect of thermal diffusion is negligible. Some influence of natural convection was observed when argon, the heavier of the two non-condensable gases, was present.

Heat Transfer During Film Condensation of a Liquid Metal Vapor

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1964.

A porous body model for predicting temperature distribution in wire-wrapped fuel rod assemblies

Abstract A porous body model, new in its application for predicting temperature distributions in wire-wrapped fuel rod assemblies, has been developed. The model developed for thermal transport in wire-wrapped rod bundles is similar in principle to the one which has long been successfully used for heat transfer in fixed beds of packed solids. Although the model is applicable to bundles in forced and mixed (combined forced and free) convection, attention in this paper is confined to bundles operating in forced (negligible natural) convection only. The results obtained from this analysis were found to predict available data with as good a precision as does the more complex analysis.

Post dryout heat transfer prediction

Abstract A mechanistic model of post dryout heat transfer has been developed involving momentum and energy equations for both vapor and liquid, average drop diameter at the dryout location, and using heat transfer correlations for vapor-to-drop, wall-to-drop, and wall-to-vapor. This involves a computer calculation stepwise down the tube from dryout. This calculation was simplified making possible the heat transfer prediction at any position down the tube without the stepwise solution. The two solutions agree well with other. To make the predictions agree with data it was found necessary to multiply the wall-to-vapor heat transfer coefficient by a factor ranging from around 0.7 to about 2. At present this factor is found to be a function of bulk-to-wall viscosity ratio and quality. It may also be a function of liquid and vapor densities, tube and particle diameters and Reynolds number. A similar effect on wall-to-gas heat transfer is found in solid particle-gas flowing mixtures. The detailed explanation is a yet unknown, but appears to be due to turbulence suppression and enhancement resulting from particle motion.

Critical heat flux in flowing liquid films

Abstract Experimental results for the critical heat flux (CHF) and boiling curve in liquid films were found in substantial agreement with recently-reported findings of other investigators. The main liquid film was observed to separate from the heater surface below CHF, leaving a thinner flowing subfilm. Drop deposition from the main film replenished the latter. When this replenishment was insufficient to compensate for subfilm evaporation, CHF occurred. A model based on the trajectories of deposited drops is proposed to explain the form of the correlating equation to within a constant.

Viscosity induced non-uniform flow in laminar flow heat exchangers

Abstract Laminar flow heat exchangers which cool oil in non-interconnected parallel passages can experience non-uniform flows and a reduction in the effective heat exchanger coefficient in a range of Reynolds number which varies with tube length and diameter, tube wall temperature and fluid inlet temperature. The method of predicting the reduction in effective heat transfer coefficient and the range of Reynolds number over which these instabilities exist is presented for a particular oil, Mobil aviation oil 120. Included, also, is the prediction of the effect of radial viscosity variation on the constant property magnitudes of friction and heat transfer coefficient.