Condensation of R-410A in a horizontal rectangular channe

In order to establish a database for the use of alternative refrigerants and design of new heat exchangers, an experimental setup to measure the condensation heat transfer coefficient of R-410a (HFC32 + HFC125 mixture, 50%/50% by weight) was designed, built, and calibrated. The test section was a 10 feet (3.05 m) long horizontal tube-in-tube heat exchanger with a rectangular brass (63% Cu and 37% Zn by weight) channel inside a Plexiglas channel. Experimental tests were conducted to measure the regionally averaged heat transfer coefficient and pressure drop during the condensation of R-410a. Both uncertainty analysis and energy balance calculation between condensing refrigerant and cooling water were used to check the accuracy of each set of experimental data.;This study focused primarily on measurement and prediction of condensation heat transfer coefficients and the relationship between heat transfer coefficients and two-phase flow regimes. Flow pattern studies showed that the condensation is predominantly in the wavy stratified flow regime at a mass flux of less than 200 kg/s-m$sp2$. For higher mass flux rates, the condensation is in the annular flow regime. The regionally averaged heat transfer coefficient for condensing R-410a in a rectangular channel decreases with a decrease in quality, and increases with an increase in mass flux. Using the experimental database a correlation was developed to predict the local condensation heat transfer coefficient. The effect of oil contamination on the heat transfer performance of R-410a was also investigated in this study. Condensation experiments were conducted with two different oil concentrations (1.26% and 2.51% by weight). Results indicated that the presence of oil decreased the condensation heat transfer coefficient.;An analytical model was developed to predict the local heat transfer coefficient during the condensation of refrigerant R-410a in the rectangular channel. Heat transfer through the top, the side, and the bottom walls was considered separately because the governing heat transfer mechanism for each wall was different. Comparison of the analytical model prediction with the experimental data showed that this analytical model predicted the heat transfer coefficients within 10% of the experimental results.