Tube pattern effect on thermalhydraulic characteristics in a two-rows finned-tube heat exchanger

Abstract

The present study deals with thermalhydraulic characteristics and entropy production analysis in a two-rows Plate Fin-and-Tube Heat Exchanger (PFTHE). Using Unsteady-RANS simulations, the effect of the iso-sectional tube shape modification (from circular to elliptic) on the air-side thermalhydraulic characteristics and entropy production rate was studied in three geometrical configurations of PFTHE and two airflow velocities. Spanwise and time-averaged representative quantities as well as the flow structure were used for local characterization of heat transfer, pressure drop, thermal and viscous volumetric entropy production rates. A global analysis of the thermalhydraulic performances and entropy production was also performed. This study highlights the direct relationship between the flow structure, local heat transfer, wall shear stress and the different components of the volumetric entropy production rate. It is shown that the reduction of the tube ellipticity significantly increases the thermalhydraulic performance of the heat exchanger up to 80% when compared to circular tube shape. Similarly a reduction of the thermal and viscous irreversibilities respectively down to 15% and 50% was observed in the modified shapes when compared to circular ones.