Critical Heat Flux in Open Concentric thermosyphon : Effect of Flow Aspect

Abstract

Critical heat flux (CHF) in two-phase thermosyphon can be improved about 8 times by inserting a tube into the thermosyphon and controlling a flow situation near its exit, where a counter-current flow of vapor and liquid always takes place. The critical heat flux can be improved by the counter-current flow there. The present experiment has been made to elucidate an effect of inserted tube on CHF by inserting either a rod or tube, which is extruded into a vapor space and then through which the vapor only flows out. For the case of the inserted rod, the CHF is gradually decreased with increasing the rod diameter and is found to be predicted by a method of maximum falling film liquid rate. For the case of the inserted tube, the CHF is also gradually decreased until a tube diameter, beyond which the CHF is again increased approaching the CHF for natural convection flow in annular channel.