Boiling and condensation in a liquid-filled enclosure

Abstract

A combined experimental and analytical investigation of boiling and condensation in a liquid-filled enclosure, with water and Freon- 113 as the working fluids, is described. The operating characteristics of a boiling system, utilizing a condenser submerged in the fluid, are presented and related to specific operational modes and thermal transport mechanisms. A lower bound of operation, corresponding to natural convection heat transfer at both the heated and condenser surfaces, is identified. Similarly, for the commonly encountered range of system operation, a condensive upper bound is identified and shown to correspond to vapor space condensation. A nondimensional vapor bubble collapse length, L c/W, is found to govern the rate and mechanism of heat transfer at the submerged condenser surface. LValues of wC << are associated with natural convection heat transfer at the L c submerged condenser. For -~ I the presence of a substantial vapor frac- w tion in the bulk liquid leads to augmented convection, while for values of L C >> 1 condensation is found to dominate thermal transport at the condenser surface. 4 possible technique for augmenting condensation heat transfer on horizontal surfaces is examined in an attempt to raise the condensive upper bound of submerged condenser operation. A doubly-rippled surface with small, constant radius of curvature undulations is shown to yield a factor of two increases in the rate of vapor space condensation based on the projected area of the condenser surface.

(cont.) A systematic design procedure for submerged condenser systems utilizing the proposed models and correlations is described and related to typical design considerations.