Evaluation of elliptical finned-tube heat exchanger performance using CFD and response surface methodology

Abstract

The elliptical tube has long been considered as an alternative of the circular tube in finned-tube heat exchangers (FTHE). Most of the previous studies evaluated the two tube shapes only based on the air-side performance of FTHE, and did not consider any interaction effect of the axis ratio with other parameters. We proposed a numerical model to simultaneously predict the fluid flow and heat transfer on both air-side and water-side of elliptical FTHE. The numerical results agree well with the reported experimental data. Response surface methodology was applied to understand the interactions among seven design factors including number of rows, axis ratio, transversal tube pitch, longitudinal tube pitch, fin pitch, air velocity, water volumetric flow rate. Response surface analysis was used to evaluate the axis ratio effect on the overall thermal–hydraulic performance which was quantified by the heat transfer rate per unit power consumption. The results indicate that the axis ratio strongly interacts with air velocity and water volumetric flow rate. The increase of axis ratio improves the overall thermal–hydraulic performance at higher air velocity or lower water volumetric flow rate, but the opposite effect is observed at lower air velocity or higher water volumetric flow rate.