Theoretical and Experimental Investigation of the Minimum Wetting Rate of a Falling Water Film on the Vertical Grooved Plate

摘要

The minimum wetting rate, at which the falling film first wets the heating surface completely when increasing the liquid flow rate, is an important value for the safe and efficient performance of the falling film device and has been studied extensively on a vertical smooth plate. In this paper, the minimum wetting rate of a water film flowing on the vertical grooved plate was studied both theoretically and experimentally. A thermodynamic method was proposed to predict the minimum wetting rate concerning the effect of the groove structure and the equilibrium water contact angle. Six grooved aluminum plates with different groove structures were tested in the experimental setup, which found that the experimental results for the minimum wetting rate are 15% lower than the theoretical results. Based on these results, a correlation of the minimum water wetting rate on the grooved plate was developed for a clear illustration of the relations involved.

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