Pool boiling heat transfer—II. Thickness of liquid macrolayer formed beneath vapor masses

Abstract

The macrolayer thickness was determined on the basis of the energy balance relation q CHF = δ 1 ϱ 1 H fg f, which was derived from the dryout model for liquids, proposed by Katto and co-workers. The critical heat flux (CHF) and the detachment frequency were measured on 20 mm diameter horizontal and vertical heated disks at pressures of 0.03–0.4 MPa with water, ethanol, methanol and acetone. Two semi-empirical correlations for the macrolayer thickness were derived by dimensional analysis of a model in which primary or coalesced bubbles form a macrolayer. The proposed correlations arrange the data of macrolayer thickness obtained from CHF measurements well.