Electrohydrodynamic Enhancement of Falling Film Evaporation Heat Transfer and its Long-Term Effect on Heat Exchangers

Electrohydrodynamic (EHD) enhancement of vertical falling film evaporation heat transfer has been experimentally studied using HCFC123, which is an alternative working fluid for CFCs. This research verified that EHD enhancement of HCFC123 condensation was as effective as that of conventional working fluids. The electrodes used for EHD enhancement of vertical falling film evaporation utilized the following two EHD phenomena: extracting the liquid by a nonuniform electric field, and surface granulation by a nearly uniform electric field. As a result, an electrode with vertically arrayed offset-slits that is suitable for industrial applications has been developed that showed a six-fold enhancement of evaporation heat transfer over that for a smooth tube. The long-term effects of the high voltages associated with EHD on heat exchanger performance have been evaluated. Operation of EHD heat exchangers for 1000 hours indicates they do not sustain serious damage, and are, therefore, suitable for industrial applications.