The paper reported heat transfer coefficients of R22 during condensation in a horizontal stainless steel rectangular microchannel with the hydraulic diameter of 0.952 mm. Tests were conducted with saturation temperatures of 40-50℃

mass fluxes of 200-800 kg/m2 s and vapor qualities from 0 to 1. The results show that heat transfer coefficients of R22 increase with mass flux and vapor quality especially in high vapor quality regions while decrease with the saturation temperature. The data were compared with three existing heat transfer correlations. Heat transfer coefficients of R152a are larger than the data of R22 when compared with the same experimental conditions.