Nucleate Boiling Heat Transfer Coefficients of Pure Halogenated Refrigerants

초록

Nucleate pool boiling heat transfer coefficients (HTCs) of HCFC123, CFC11, HCFC142b, HFC134a, CFC12, HCFC22, HFC125 and HFC32 on a horizontal smooth tube of 19.0 mm outside diameter have been measured. A cartridge heater was used to generate uniform heat flux on the tube. Data were taken in the order of decreasing heat flux from 80 kW m-2 to 10 kW m-2 with an interval of 10 kW m-2 in the pool of 7？aC. It was found that nucleate boiling heat transfer correlations available in the literature were not good for certain alternative refrigerants such as HFC32 and HCFC142b. Hence, a new correlation was developed by a regression analysis taking into account the variation of the exponent to the heat flux term as a function of reduced pressure and some other properties. The new correlation showed a good agreement with all measured data including those of new refrigerants of significantly varying vapor pressures with a mean deviation of less than 7%.