A Correlation in Displacement Velocity of Liquid Film Boundary formed on a Heated Vertical Surface in Emergency Cooling

Abstract

Intense ebullition occurs at the liquid front heading a falling sheet of water over a heated vertical surface, as in the case of emergency cooling. It has been ascertained that the displacement velocity of this liquid front is nearly constant for the values of specified parameters such as wall temperature before cooling, flow rate of cooling liquid, and the physical properties of heated wall and cooling liquid. Observations were conducted on the liquid front velocity using a heated wall of stainless-steel and with tap water as cooling liquid. An analysis has been made on the basis of a two-dimensional transient heat conduction model, the result of which proves to be valid for explaining the liquid front behavior when account is taken of boiling heat transfer. The liquid front velocity is given by where N denotes a reference state. The above relation is applicable in the region of flow rate from 0.245 kg/m.sec to 2.45 kg/m.sec.