Evaporation heat transfer and pressure drop of R32 in a horizontal multiport tube with microfins.

This study investigated the evaporation heat transfer and pressure drop characteristics of refrigerant R32 in a horizontal multiport tube consisting of rectangular minichannels with straight microfins. The heat transfer coefficient and pressure drop were measured for a range of mass velocities from 100–400 kg*m-2*s-1 and range of heat fluxes from 5–20 kW*m-2 at a saturation temperature of 15°C. The frictional pressure drop during adiabatic two-phase flow was also measured for a range of qualities from 0.1–0.9 at the same saturation temperature. The heat transfer coefficient increased with increasing mass velocity in the high quality region. The effects of heat flux on the heat transfer coefficient were small except in the high quality region. The heat transfer coefficient values for the multiport tube with straight microfins were higher than the values for the multiport tube without microfins at lower mass velocity. The effects of mass velocity and microfins on the frictional pressure drop were clarified.