Study on Flow Boiling of Refrigerants in Micro/Mini-Channels

Abstract The flow boiling heat transfer in micro/mini-channels is encountered in many compact heat exchangers such as the once-through steam generator in nuclear reactors due to its high heat transfer efficiency and thus accurately predicting the heat transfer coefficients is of great importance. Nowadays, for the high saturation temperature of water, refrigerants are more widely used in the flow boiling heat transfer experiments and a lot of heat transfer correlations are raised based on the data of refrigerants. Therefore, the accuracy of heat transfer correlations for refrigerants in flow boiling micro/mini-channels are analyzed in this paper. Firstly, five commonly used heat transfer correlations are summarized which can be simply divided into Chen type and Nusselt type and nearly 1000 experimental data of refrigerants conducted in the micro/minichannels are collected from 5 separate experiments. Then, due to the relatively low predicting accuracy of current heat transfer correlations, a new non-dimensional heat transfer correlation has been proposed by analyzing the experimental data with the application of Bond number in the range of 0.42–9.61, liquid Reynold number in the range of 34–8793, Boiling number in the range of 0.55 × 10−4 – 20.66 × 10−4. Finally, this new correlation is applied to water in different working conditions and the predicting accuracy has been analyzed.