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Abstract:

Abstract
In this paper, the pool boiling of ethanol was analyzed. The experiments were carried out at
atmospheric pressure. Heat transfer surfaces in the form of deep minichannels were made
of copper. The channels with a depth of 0.2 to 0.5 mm were milled in parallel. The width
of the minichannels was 0.6–1.2 mm, and the depth was 5.5, 6, and 10 mm. The highest
heat transfer coefficient, 52 kW/m2K, was achieved for the minichannels with a depth of
6 mm and a width of 0.8 mm. The maximum heat flux of 953 kW/m2 was produced using
minichannels 5.5 mm deep and 0.5 mm wide. An over threefold increase in the heat transfer
coefficient and over a twofold increase in the maximum heat flux in relation to the plain
surface were obtained. In the heat flux range 21.2–1035 kW/m2, the influence of channel
width and depth on the heat exchange process was determined. The diameters of the
detaching vapor bubbles were determined on the experimental setup using a high-speed
camera. An analytical model was developed to determine the diameter of the departing
bubble for the analyzed enhanced surfaces. The model correctly represented the changes in
bubble diameter with increasing heat flux.

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Pool Boiling Heat Transfer of Ethanol on Surfaces with Minichannels