Is there an easy formula to calculate the wet heat transfer coefficient?
Q: 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? A: The 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.