The two vertical halves of the wall of a 4.3-in. I.D. cylinder were maintained a t different uniform temperatures. The rate of circulation of air inside the cylinder and the local rate of heat transfer between the wall and air were derived from measurements of the velocity and temperature fields in the air for wall-temperoture differences from 3.5' to 367'F. The overall rate of circulation was found to increase quite rapidly and then to decrease slowly as the wall-temperature difference was increased. The over-all Nusselt number based on the walltemperature difference was found to have an approximately constant value of 7.0.Numerical solution of the partial differential equations describing the conservation of mass, momentum, and energy for this system was investigated with an IBM-650 magnetic drum computer. Instabilities in the computational procedure and limitations of this computer prevented solution of the general problem. However specification of the velocity field obtained from experiment yielded a numerical solution for the temperature field in good agreement with the experimental measurements.The importance of natural convection in space heating and meteorology has long been recognized. More recently attention has been given to such applications as the emergency cooling of nuclear reactors, the cooling of gas turbine blades, and the recombination of the oxygen and hydrogen involved in water-boiler types of nuclear reactors. Nevertheless natural convection, particularly in enclosed spaces, has been a relatively neglected field of investigation.Apparently natural convection in a horizontal cylinder has been studied experimentally only by Ostroumov ( l ) , who discussed the determination of the temperature gradients in glycerine by an optical method but did not present any data. Zhukhovitskii and others ( 2 , 3 , 4 ) outlined a method for the approximate solution of the mass, energy, and momentum equations describing natural convection. Results in agreement with the unpublished experimental work of Ostroumov were claimed. The method appears to be applicable only for low temperature differences and/or for fluids of high viscosity, and only for very special boundary conditions. In this investigation a long horizontal circular cylinder and a step function in temperature at the vertical diameter were chosen for simplicity.
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