Effects of Surface Conditions on Transient Pool Boiling CHF in Various Liquids with Different Mechanisms Depending on Pressure and Subcooling

Abstract

Boiling CHF was assumed to happen based on hydrodynamic instability, and the value was thought to be unaffected by the surface condition of heater so far. However, it has been understood that the CHF value changes systematically depending on experimental conditions according to a series of experiment of the authors. As the reason, it is assumed that CHF occurs based on heterogeneous spontaneous nucleation (HSN). Especially, it appears remarkably in transient boil CHF. Moreover, it is thought that HSN physically influences the surface condition. In this study, the transient pool boiling CHF for exponential heat generation rates with various periods for saturated and subcooled liquids at various pressures were investigated to clarify the effects of surface conditions such as commercially-available and roughly-finished surface cylinders in water, ethanol and FC-72. It was clarified that the trend of CHF for the shorter periods was significantly affected by the surface conditions.