EXPERIMENTAL HEAT-TRANSFER COEFFICIENTS DURING CONDENSATION OF HALOGENATED REFRIGERANTS ON ENHANCED TUBES

The development of enhanced surfaces for condensation of refrigerants is fundamental to improve the efficiency of condensers and of refriger ation systems. The present work experimentally investigates the combin ed effect of geometry and vapour shear stress on heat transfer during condensation of pure refrigerant vapour on the outside of a single hor izontal enhanced tube. Two different series of tests are taken: the fi rst using a 2000 fpm (fins per meter) integral-fin tube, the second us ing a commercial enhanced tube (Hitachi Thermoexcel). Experimental dat a includes R11 and R113 runs taken with vapour pressure ranging from 1 11 to 190 kPa, average condensation temperature difference varying fro m 3.4 to 18.5 degrees C and maximum vapour velocity from 0.8 to 37.9 m /s. The present experimental results are compared with data previously obtained by the authors with a 1333 fpm tube and with the smooth tube trend. Also the comparisons with theoretical models for the predictio n of condensation heat transfer coefficients oil finned tubes are repo rted.