Flow boiling heat transfer and pressure drop of pure HFC-152a in a horizontal mini-channel

This study investigates boiling heat transfer and two-phase pressure drop of HFC-152a in a horizontal square mini-channel of 1 mm in diameter. Convection heat fluxes were obtained using an inverse heat transfer method. Tests were performed at a nearly constant system pressure of 600 kPa and under saturated conditions. Local heat transfer coefficients were determined as a function of vapor quality along the length of the test section. Tests were carried out for mass flux ranging from 200 to 600 kg/m2s and for heat flux ranging from 10 to 60 kW/m2. Experimental results were compared to predictive models from the literature for two-phase flow pressure drop and boiling heat transfer. The correlation of Müller-Steinhagen and Heck (1986) was found to give a good agreement for prediction of mini-channel frictional pressure losses. The heat transfer mechanism was found to be dominated by nucleate boiling, and the heat transfer coefficient independent of vapor quality and mass flux. A new correlation for Nusselt number was developed based on the Tran et al. (1996) correlation, which was able to predict the present experimental data with respective average and maximum absolute deviations of 3.7% and 11%.