Pressure drop and heat transfer performance of microchannel heat exchangers with elliptical concave cavities

Abstract

For a microchannel heat exchangers (MHE) with an elliptical concave cavity, the ellipticity of the cavity has a significant effect on the pressure drop and heat transfer performance of the MHE. In this study, five types of MHEs with elliptical concave cavities were designed—with ellipticities of 0.4, 0.6, 0.8, 1.0, and 1.2—and the effects of ellipticity on pressure drop and heat transfer performance were investigated numerically and also measured experimentally, using a self-designed experimental platform. The results show that at the same inlet flow rate the pressure drop of an MHE with elliptical concave cavity becomes smaller and then larger as the ellipticity increases, and that the pressure drop at the inlet and outlet of the MHE with ellipticity 1.0 is the smallest, providing the best pressure-drop performance. When the inlet flow rate increased from 10 ml/min to 60 ml/min, the inlet-to-outlet pressure drop of the MHE with ellipticity 1.0 increased from 20.6 to 152.9 Pa, an increase of 132.3 Pa. As the inlet flow rate increases, the hot-water outlet temperature of the MHE with elliptical concave cavity first decreases and then increases, while the cold water outlet temperature behaves oppositely. When the inlet flow rate is 30 ml/min, the hot water outlet temperatures of all the MHEs with elliptical concave cavities reach their lowest values. These minimum outlet temperatures are 316.2 K for ellipticity 1.0, 317.9 K for ellipticity 0.8, 318.9 K for ellipticity 0.6, 320.4 K for ellipticity 0.4, and 319.9 K for ellipticity 1.2. Results indicate that among the configurations tested the MHE with ellipticity 1.0 exhibits the best heat transfer performance.