An experimental study of evaporative coolers using elliptic tubes

This paper reports on the investigation of the heat/mass transfer and pressure drop performance characteristics of an evaporative cooler using elliptic or circular tubes. From the experimental results, correlations of the water film heat transfer coefficient and air-water mass transfer coefficient are developed. The experimental results show that the smaller contraction ratio of circular tube bundle results in higher air velocity between the tubes, and increases the fluid film waviness with water spraying outside the tubes. Consequently, the heat and mass transfer performance of the circular tube bundle is better than that of the elliptic one at the same air flow rate. However, the elliptic tube bundle yields only 1/3 pressure drop as compared with the circular one. Both the water film heat transfer coefficient and air-water mass transfer coefficient of elliptic and circular tube bundles increase with increasing air Reynolds number.