Natural refrigerant as replacement for conventional refrigerant is more intensively used for reducing environmental damage. This research aims were to flow pattern mapping and study heat transfer, pressure drop of two-phase flow boiling with natural refrigerant in microchannel. Experimental method used evaporative process in test section on tube diameter 500 μm and length 0.5 meter. Observation parameter used mass flux 681 – 766 kgm-2s-1, heat flux 5.28 – 7.66 kWm-2 and saturation temperature 31.96 – 33.14 oC. Result experiment showed single flow regime and two-phase flow regime with low vapor quality to 0.15. Frictional pressure drop was higher than acceleration pressure drop, where the resulting acceleration pressure drop has been calculated with small value from total pressure drop (0.5%). Mass flux contributed a strong effect on coefficient of heat transfer convective. Heat flux more effected to heat transfer of two-phase flow nucleate boiling. Wang map were used to plot flow patterns of two-phase in microchannel.
Keywords: flow pattern; two-phase; pressure drop; heat transfer; microchannel