Phase Change and Heat Transfer Analysis of Different Refrigerants During Condensation in Minichannel Using a Novel Numerical Approach

Abstract

This paper analyses the condensation heat transfer phenomena in minichannel using acetone, ammonia, propylene, and R134a as the working fluids used in new-age space applications. A novel numerical model is developed considering the changes in local vapor pressure in the channel established due to shrinking in the flow passage by the gradual formation of the liquid layer. The present developed numerical model is compared with the available numerical and experimental results. The impacts of different inlet mass fluxes (250, 500, and 750 kg/m2 s), channel heights (1, 4, 6, and 8 mm), applied heat loads (10, 100, 250, and 500 W), and channel orientations (0 deg, 30 deg, 45 deg, 60 deg, and 90 deg) on the performance of the condensation heat transfer process are investigated. The formation of the thin liquid film layers and evaluation of the liquid–vapor interface profiles are examined. The study reveals that the channel orientation has a marginal influence on the flow pattern for the considered channel length of 20 mm. The maximum change in pressure loss is found at the channel orientation of 45 deg, and the average heat transfer coefficient is almost the same for all the considered orientations. The flow pattern is affected by the increase in mass flux resulting in the delay of heat transfer coefficient fluctuations. The average heat transfer coefficient decreases with increasing heat load, and the minimum average heat transfer coefficient is obtained for heat load, Q = 500 W.