I have to design a propane evaporator. Propane is at -20 degrees C. The heating fluid is ambient air at 10 degrees C and 80% humidity. The evaporator will consist of several tube bundles equipped with extruded aluminum plain fins.
During the heat-transfer process water will condense on the outside finned surface. Do you have an easy formula to calculate the wet heat transfer coefficient on the outside finned surface?
Have an insight or suggestion?
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Re: Is there an easy formula to calculate the wet heat transfer coefficient?
10 March 2009 at 1:29pmThe conservative manner is to assume a gas only coefficient throughout. However, if you wish to be more accurate, the unit should be evaluated in the de-superheating regime (80%-100% humidity) and then using a wet surface coefficient for the remainder of the unit.
The following articles discuss this topic:
Determination of apparent heat transfer coefficient by condensation in an industrial finned-tube heat exchanger: prediction
Experimental and computational performances of heat exchangers functioning in wet regime by using the film method.
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