EHD BOILING HEAT-TRANSFER ENHANCEMENT OF R123 AND R11 ON A TUBE BUNDLE

The results of an experimental study of electrohydrodynamic (EHD) enha ncement of pool boiling are presented in this paper. A high intensity de electric field was applied to R123 and R11 boiling on the shell sid e of a smooth five-tube shell and tube heat exchanger. The tubes were electrically heated and were arranged in three rows. The electrode sys tem carrying the high voltage comprised fourteen mild steel rods place d in between and around the tubes. Experiments were performed at heat flux values of 20-5 kW m(-2) and applied voltages of 0-25 kV. The enha ncement ratio for R123 increased linearly with an applied voltage of u p to 15 kV and was strongly dependent on heat flux. Increasing the vol tage beyond 20 had no effect on the enhancement ratio at heat flux val ues greater than 10 kW m(-2). At lower heat flux, some further increas e in the enhancement ratio was obtained when increasing the voltage fr om 20 to 25 kV, The enhancement with R11 was marginal, indicating the importance of fluid properties to electrohydrodynamic enhancement. The effect of pressure on the enhancement was also examined. (C) 1998 Els evier Science Ltd. All rights reserved.