Nucleate Boiling Heat Transfer: Temperature Pulsations or Local Thermal Shocks

Abstract This paper discusses thermo-mechanical consequences of the pumping effect of growing bubble (PEGB) resulting in surface thermal stresses during nucleate boiling. Unfortunately, the unavailability of boiling heat transfer studies specifically addressing the scope and duration of the PEGB effect, including lack of models and universal correlations of boiling heat transfer, has hindered the overall understanding of nucleate boiling heat transfer to date. As a result, specific types of cyclic thermal stresses at the surface which are capable of producing thermal shocks in some boiling regimes and that are attributable to PECB have remained unexplored. This has prevented complete theoretical determination of the service life of heating surfaces of boiling systems such as boiling water reactors (BWR) and metal quenching technology. In this paper, some preliminary estimates of the tasks required for experimental studies required for further theoretical development are presented. With regard to the quenching processes, discussions regarding the probable negligible consequences of thermal stresses caused by the PEGB are presented.