Pressure influence on unsteady film boiling of water-ethanol mixtures

Abstract

Abstact Film boiling of subcooled liquid is a process important for many technologies. However, there exists the specific film boiling regime accompanied by an enormous heat transfer coefficients, which has no common physical explanation. This paper presents the new experimental results on influence of a liquid properties and its subcooling on this high intensive boiling regime. The quenching a stainless steel sphere in subcooled water-ethanol mixtures of different compositions at different liquid temperatures and pressures up to 0.5 MPa was an object for study. The cooling process considerably intensifies with increase of pressure and of water mass fraction in the mixture. At some conditions, the transition temperature corresponding to incipience of the intensive boiling regime noticeably exceeded the critical temperature of the liquid; as direct liquid-solid contact is impossible in this case, micro-bubble boiling regime obviously occurred. All results obtained are in qualitative agreement with the model of incipience of the intensive film-boiling regime of subcooled liquid published previously by the authors.