The experiments conclude that at 21 rectangular copper micro-channels with 0.3847 mm in hydraulic diameter and 40 mm in length and with heat flux 2.3116 and 6.9443 W/cm2 .By keeping Liquid Superficial Reynolds Number respectivly 149.044 and 164.956, keeping Gas Superficial Reynolds Number respectivly 2.568 and 2.759. So, the two values in this experiment is good of heat transfer