Condensation heat transfer of ethanol-water vapor in a plate heat exchanger

Experimental investigation on ethanol-water vapor in a commercial plate heat exchanger (PHE) was carried out. In the experiment two vertical counter flow channels were formed in the exchanger by four plates with a corrugated sinusoidal of a chevron angle of 600. Local heat transfer coefficient (HTC) along the plate was investigated by welding thermocouple on the plate surface, a mean HTC was introduced along plate surface to evaluate the effect of ethanol concentration (1%, 2%, 5%, 10%, 20%), system pressure (30 kPa, 47 kPa, 83 kPa) and plate number (single condensation channel and double condensation channels) on condensation HTC. The results indicated that local HTC decreased in turn along vapor flow direction, the HTC increased almost linearly with the exit vapor quality of PHE for all concentrations vapor. Ethanol concentration exhibited stronger effect on HTC compared to other two factors. Local and mean HTC had higher value comparing with pure water steam for low concentration vapor (1%, 2%), and the mean HTC of 1% concentration could be augmented as much as 110% compared with steam. The mean HTC generally increased with increasing pressure for all concentrations of the ethanol-water mixtures. Moreover, visual observation was made and showed dropwise condensation occurred for mixed vapor owing to Marangoni effect. (C) 2016 Elsevier Ltd. All rights reserved.