EHD ENHANCED CONVECTIVE BOILING OF R-134A IN GROOVED CHANNELS - APPLICATION TO SUBCOMPACT HEAT-EXCHANGERS

Electrohydrodynamically (EHD) enhanced flow boiling of refrigerant R-1 34a inside grooved channels of approximately 1-mm hydraulic diameter w as investigated with the objective of addressing the applicability of the EHD technique in highly compact heat exchangers, Two sets of exper iments were performed. The first set included experiments in a channel with a smooth heat transfer wall, whereas in the second set a corruga ted (enhanced) surface was used. In each case experiments were conduct ed as a function of the applied electrical field strength, electric fi eld polarity, flow Reynolds number, inlet test section vapor quality, and flow direction (upward, downward, or horizontal). It is demonstrat ed that in all cases the EHD effect can substantially increase the hea t transfer coefficient particularly at low Reynolds numbers and when a pplied over the enhanced heat transfer wall.