2-PHASE CROSS-FLOW AND BOILING HEAT-TRANSFER IN HORIZONTAL TUBE BUNDLES

An experimental study has been conducted to determine the void fractio n, frictional pressure drop, and heat transfer coefficient for vertica l two-phase crossflow of refrigerant R-113 in horizontal tube bundles under saturated flow boiling conditions. The tube bundle contained 5 X 20 tubes in a square in-line array with pitch-to-diameter ratio of 1. 3. R-113 mass velocity ranged from 50 to 970 kg/m(2)s and test pressur e from 103 to 155 kPa. The void function data exhibited strong mass ve locity effects and were significantly less than the homogeneous and in -tube flow model predictions. They were found to be well correlated in terms of the dimensionless gas velocity, j(g). The two-phase frictio n multiplier data could be correlated well in terms of the Lockhart-Ma rtinelli parameter The validity of these correlations was successfully tested by predicting the total pressure drop from independent R-113 b oiling experiments. The two-phase heat transfer coefficient data were found to agree well with existing pool boiling correlations, implying that nucleate boiling was the dominant heat transfer mode in the heat flux range tested.