SWIRL FLOW POST-CHF HEAT-TRANSFER WITH REFRIGERANT-113

Heat transfer rate was experimentally determined in the post-CHF regio n of a steady-state two-phase flow of a refrigerant in a vertical tube with swirl induced by twisted-tape inserts. Experiments were performe d with the vertical flow of refrigerant-113 in a tube with inside diam eter of 7.75 mm, a heated length of 3.66 m and mass flux of 375-535 kg /m(2)s for swirl flow at a pressure of 0.184 MPa. Four tapes were used with twist-ratio of 2.5 to 9.2 for swirl flow. Liquid heating produce d the low wall-superheat in the post-CHF region at steady-state, which is typical of heat exchanger operation. Superheated vapor measured at the test section exit in most tests ensured that entire post-CHF regi on was included. All refrigerant-113 data were compared with the data of water and refrigerant-12. The existing post-CHF heat transfer corre lation of swirl now was modified to predict the magnitude and trends o f the data of the three fluids such as water, R-12 and R-113.