Numerical Study on Liquid-Film Cooling at High Pressure

Abstract

Physical and mathematical models for film cooling at high pressure are established, in which the solution of gas in liquid, real gas property, and its variable thermophysical properties are taken into account. Gas-liquid equilibrium at the interface is presumed based on which interface condition and thermodynamics properties of fluid at supercritical pressure are investigated. Model study has been performed for liquid film emission spanning the mixed critical line, as well as the film cooling performance at high pressure. It has been found that the cooling mechanism of liquid film at high pressure is different from that at low pressure. At high pressure, the effect of latent heat, which plays a dominant role in liquid film cooling at low pressure, becomes weakened because the latent heat of vaporization decreases with an increase in pressure. Furthermore, liquid film at high pressure possibly transfers to supercritical emission regime before dryout, in which the interface vanish and the latent heat of vaporization reduces to zero. In the supercritical regime, all of the thermal energy transferred from the hot gases is devoted to heating up the film.