Abstract:
Heat-transfer experiment was conducted for condensation of steam-ethanol mixtures in vertical down flow over two horizontal, water-cooled, low-finned copper tubes at atmospheric pressure. Tube had a fin height of 1.6 mm, root diameter of 12.7, thickness of 0.3 mm and spacing between fins of 0.5 mm. Tests were conducted at atmospheric pressure. Effects of ethanol concentration on both retention angle and heat transfer were measured. The retention angle was strongly dependent on ethanol concentration, upstream vapour velocity, temperature of the condensate at the interface and consequently the surface tension. Mass fractions of ethanol used to conduct tests were 0.025, 0.05, 0.1, 0.5 and 1.0percent. Range of vapour velocity at approach to the condenser tube was 0.78 to 7.5 m/s. For each composition and vapour velocity, measurements were recorded for a range of vapour to surface temperature difference. As a result of Marangoni phenomenon obtained by using steam ethanol mixture,a maximum sustainable heat transfer enhancement up to 3 times as
compared to that of pure steam was obtained.
