A correlation for forced convective boiling heat transfer of pure refrigerants in a horizontal smooth tube

An experimental study is reported on the boiling heat transfer of HFC134a, HCFC22, CFC114 and CFC12 flowing inside a 7.9 mm ID horizontal smooth tube. Using a water-heated, double-tube type evaporator, the local heat transfer coefficients are measured for both counter and parallel flows. Based on the supposition of Chen that the total heat flux is represented as the sum of forced convective contribution and nucleate boiling contribution, a correlation equation is proposed for the data in the annular-flow regime. The mean deviation between the calculated and measured heat transfer coefficients is 12.2% for the present experimental data and 9.5% for the data available from literature. The proposed correlation shows that the nucleate boiling is not fully suppressed even in the high-quality region in the case of counter flow, while convective evaporation is dominant in the high-quality region with uniform heat flux condition.