Experimental investigation on condensation heat transfer in horizontal microfin and smooth tube with refrigerant R22

Local condensation heat transfer of R22 in a microfin tube and a plain tube are measured and compared.The two tubes have the same outer diameter of 9 mm,the active length of test tube is 1 104 mm,microfin tube is manufactured from the same plain tube.The test was measured at the condensation temperature of 38.6 ℃ with mass flux of 30 kg/h and 60 kg/h,quality of 0.2~0.8,and the constant heat flux of 15 kW/m2.The result indicates that the local heat transfer coefficients of microfin tube are about 1.7 times of those of the plain tube.But the enhancement of heat transfer coefficient is different with refrigerants mass flux.At lower refrigerant mass flux 30 kg/h,the augmentation of heat transfer is the same at different quality while increases with quality increase at higher mass flux 60 kg/h.