ABSTRACT
Flow boiling is distinguished from pool boiling by the presence of fluid flow caused by natural circulation in a loop or forced by an external pump. In both systems, when operating at steady state, the flow appears to be forced; no distinction will be made between them, since only the flow pattern and the heat transfer are of interest. In fully developed nucleate flow boiling, the heat flux is affected by pressure and wall temperature but not by flow velocity. Brown noted that a vapor bubble in a temperature gradient is subjected to a variation of surface tension which tends to move the interfacial liquid film. To maintain nucleate boiling on the surface, it is necessary that the wall temperature exceed a critical value for a specified heat flux. The stability of nucleate boiling in the presence of a temperature gradient is also valid for the suppression of nucleate boiling with decreasing wall superheat in the two-phase region.
