Flow boiling heat transfer enhancement in microchannels under needle electrode

To investigate the effect of electric field on flow boiling heat transfer in microchannels, a needle electrode arrangement was designed to introduce the electric field into the microchannels with designed capacity of system pressure at 140kPa and inlet temperature at 32.5℃ by using the refrigerant R141b as the experimental working fluid. The experimental results indicated that the electric field has a significant effect on the flow boiling heat transfer of the refrigerant R141b in microchannels, promoting onset of nucleate boiling (ONB) and enhancing heat transfer performance. Compared to the condition without electric field, the required superheat at ONB on 250V, 550V, 850V was reduced by 0.6℃, 1.26℃, and 1.78℃ respectively. The electric field can significantly enhance the boiling heat transfer in the downstream region after the ONB point. The local heat transfer coefficient increases with the increase of voltage and the partial boiling heat transfer coefficient increases by as much as 89.7% under the experimental conditions. Three heat transfer models were selected for comparison. It was found that the Sun-Mishima model has the best prediction and the model revised by introducing the voltage parameter U could better predict the experimental value of the heat transfer coefficient under the experimental conditions and the mean absolute error is 12.2%. © 2019, Chemical Industry Press. All right reserved.