Evaporative heat transfer and pressure drop in a rib-rou-ghened flat channel. Vertical upflow and downflow in a cross-ribbed channel.

Abstract

Studies on evaporative heat transfer and pressure drop in a vertical smooth and a cross-ribbed channel were conducted using R-12 as a working fluid. Experimental data were obtained for upflow and downflow at mass velocities between 50 and 140 kg/m2s and mass qualities between 0.1 and 0.8. Comparison of these data indicates that in the cross-ribbed channel the heat transfer coefficient increases by as much as a factor of about 3 above the smooth channel under the same conditions, and the heat transfer coefficient for upflow is better than that for downflow by 30 to 70% both in the smooth and ribbed channels. In addition, evaluation of these channels using the volume goodness factor shows that the heat transfer performance of the cross-ribbed channel is superior to that of the smooth channel by 20 to 80% under the same pumping power condition.