Heat transfer in the boiling regime

摘要

Numerous metallurgical systems use water cooling to control heat extraction. While water is an excellent medium in many cases, it can, nonetheless, pose problem in high heat flux applications, especially if localized boling is encountered. Moreover, the result may be catastrophic if the heat transfer is dominated by film boiling. A series of tests were devised to study the transition between nucleate (free) boiling and film boiling in closed systems. While calssical studies of boiling are configured to examine a heated solid surface in a body of fluid, the present study used a novel approach whereby the water formed the working fluid of a heat pipe. Nucleate and film boiling were clearly discernible. Moreover, during the course of the study we discovered an interesting streategy for averting film boiling. Het flux measurements show that heat transfer can be enhanced by an order of magnitude or more with the modification we developed. These results can have important implications in some water cooled systems currently in use. This paper briefly reviews boiling heat transfer theory and then details the experiments that were conduced to illustrate how boiling heat transfer can be enhanced and how film boiling can be avoided.