Enhanced effect of a horizontal micro-fin tube for condensation heat transfer with R22 and R410A

This study presents the local heat transfer characteristics of R410A, a potential candidate for replacing R22, condensing in a horizontal smooth and a micro-fin tube. For a comparison, the R22 condensation heat transfer data are also shown, The test sections of the present experimental apparatus consist of 7 counter-flow heat exchanger type units. The refrigerant flows in a horizontal copper tube and the cooling water flows through the annular space outside of the tube. The in-tube condensation heat transfer coefficients were obtained from the measured overall heat transfer coefficient of each test unit and the annulus-side heal transfer coefficient. The annulus side heat transfer coefficients were determined from the correlation developed using a modified Wilson plot technique in this study. The experiment has been conducted with the refrigerant mass flux ranging from 97 to 202 kg/m(2)s, The condensation heat transfer coefficient of R410A in the smooth tube were compared to some existing correlations frequently referred to in open literature. The present data confirmed the applicability of the correlations to this alternative refrigerant for condensation heat transfer in smooth tubes. The enhancement ratio of the micro-fin tube ranged from 1.5 to 2.2 based on the nominal heal transfer area. It becomes higher with decreasing mass flux and increasing quality for both R22 and R410A.