Heat Transfer 1970/4. [antikvár]

INTRODUCTION This paper is a report of an investigation of transient natural convection inside a long horizontal cylinder whose walls were maintained at a uniform temperature which changed at a steady rate. Although the phenomenon was a transient one, the heating (or cooling) rate was held constant long enough so that a quasi-steady state was approached, such that local temperature gradients, velocities, and other parameters were very nearly independent of time. If thermophysical properties are assumed constant, the equations describing this system are identical with those for a fluid with uniform heat sinks (or sources) in a long horizontal cylinder whose walls are held at a constant uniform temperature. Thus, the results of this study should apply as well to the uniform heat sink problem. Although natural convection in enclosures has stimulated much interest in recent years, transient natural convection in horizontal cylinders and related geometries has received very little attention. E. Schmidt [1] investigated transient heating of a sphere subjected to a step change in uniform wall temperature. Evans and Stefany [2] applied the same boundary conditions to short cylinders in both horizontal and vertical positions. The problem with geometry and boundary conditions most closely resembling the present work, that of transient heating in a horizontal cylinder with uniform heat flux at the wall, was studied by Maahs [3]. The results of these experiments are compared to the results of this investigation later in the paper. ^Publication from the Heat Transfer Laboratory, School of Mechanical and A^erospace Engineering, University of Minnesota. NC1.1