Experimental investigation on flow boiling characteristics of the ethanol-water mixture in conventional channels

The flow boiling heat transfer characteristics of the ethanol-water mixture (25%/75% by volume) and its pure constituents was experimentally investigated in conventional channels. The experiments were conducted for different ranges of mass flux, heat flux, subcooled inlet temperature and two different aspect ratios (AR). Flow patterns recorded by high-speed camera indicated that the bubble waiting and the growth period are minimum for the mixture and maximum for the ethanol, resulting in a higher heat transfer coefficient (HTC) for the mixture and lower HTC for ethanol in both the channels. For all the working fluids, high HTC was observed for the channel of AR = 1.25 in the forced convective region, whereas in the subcooled boiling region, high HTC was observed for the AR = 0.2 channel. The average subcooled HTC obtained for the 25% ethanol-water mixture was 15.75% and 38.85% higher than that of water and ethanol respectively for the AR = 0.2 channel. However, it was 18.11% and 41.2% higher than that of water and ethanol for the AR = 1.25 channel.