Abstract
Dryout process appearing near critical heat flux for water boiling on an upward heating surface was investigated with conductance probes with tip diameter below 5μm. 2-D distribution of dryout void fraction was obtained by analyzing the dryout signals which were measured at 3〜5μm above the heating surface at 121 grid points in an area of 1×1[mm^2]. It was found that the dryout void fraction increased rapidly near critical heat flux and the dryout occurred in specific area of the heating surface. The liquid layer thicknesses were estimated based on the time from formation of vapor mass to start of dryout. and agreed well with the previously reported thicknesses which was determined from the height at which the vapor mass signal disappear.
