ONSET OF NUCLEATE BOILING, HEAT TRANSFER, VOID FRACTION AND PRESSURE DROP IN SUBCOOLED CONVECTIVE BOILING WITH R12
Detailed knowledge of th physical phenomena involved in subcooled boiling is of great importance for the design of liquid-cooled heat generating systems with high heat fluxes. Experimental data of heat transfer, void fraction and pressure drop were obtained for forced convective boiling of dichloro- difluoroethane (R 12). The flow is circulated upwards through a concentric annular vertical channel. The reduced pressure studied were 0,24 ≤ p/pcritO,8, inlet subcooling varing from 10 to 75 K and mass fluxes from 500 to 3000 kg/m2s, which corresponds to Re numbers from 30 000 to 300 000. For correlating the void fraction in subcooled flow , the drift flux model by Zuber was extended, by introducing a new equation for the distribution factor Co with the Jakob- and Froude-number as variables.