CRITICAL HEAT FLUX AND FLOW CHARACTERISTICS OF SUBCOOLED FLOW BOILING IN NARROW TUBES.

Abstract

The critical heat flux (CHF) of subcooled flow boiling in narrow tubes and its flow characteristics were investigated, and the bubble boundary layer concept was discussed. For subcooled flow boiling in narrow tubes of 1 mm inside diameter, the void fraction was estimated to be several ten percent smaller than that predicted by the subcooled void fraction correlations for large-inside-diameter tubes. This caused the CHF in the narrow tubes to increase and the friction pressure drop multiplier to decrease. The Tong CHF correlation based on the bubble boundary layer separation model was examined. Considering the dependence of pressure on the empirical parameter C in the Tong correlation, a modified correlation was proposed.