Performance characterization of R134a and R245fa in a high aspect ratio microchannel condenser

An experimental study on parametric characterization of two-phase condensing flows of refrigerants R134a and R245fa in a single microchannel was carried out utilizing a microchannel with a cross-section of 0.4 mm × 2.8 mm (7:1 aspect ratio) and length of 190 mm. The study investigated parametric effects of variations in saturation temperatures between 30 °C and 70 °C, mass flux between 50 and 500 kg m−2 s−1, and inlet superheats between 0 °C and 20 °C on the average heat transfer coefficient and overall pressure drops in the microchannel. The results of the study suggest that while the saturation temperature and mass flux have a significant effect on both the heat transfer and overall pressure drop coefficients, the inlet superheat has little or no effect. In addition, the applicability of the Dobson–Chato correlation for heat transfer coefficient and Lockhart–Martinelli correlation for pressure drop for the range of parameters was investigated.