Flow analysis of the effect of tube geometry on the performance of pre-coolers for turbine-based hypersonic air-breathing propulsion

In this work the effect of the tube geometry on the performance of a staggered tube cross-flow heat exchanger, similar to the inlet air pre-coolers in hypersonic aircrafts and air-breathing launch vehicles, is studied using computational fluid dynamics (CFD) at sea level conditions with air velocity of up to 50 m/s. Single tube simulations showed a decrease in drag coefficient and increased utilization of tube surface area for heat exchange when elliptical or obround tubes are used instead of a circular tube. In a tube bank, the heat transfer coefficient is enhanced and the friction factor is reduced by using the elliptical and obround tubes as compared to circular tubes. Overall, for the same heat duty, elliptical and obround tube pre-coolers are lighter and compact but the pressure drop is higher than a circular tube pre-cooler.