Flow and heat transfer characteristics of microchannel air-oil heat exchangers for aero-engine cooled cooling air system

This paper proposes the application of microchannel heat exchangers in the Cooled Cooling Air field of aero-engines. Numerical simulation on the flow and heat transfer characteristics of a microchannel air-oil heat exchanger was conducted. To enhance the heat transfer capability on the air side of the heat exchanger, the pin-fin structure was used and optimized. Studies indicate that airfoil-shaped pin-fins structure provide better heat transfer performance with lower pressure loss, achieving the highest overall heat transfer performance index, which is 33.2% higher than that of cylindrical pin-fins structure. The optimal longitudinal pin-fin spacing is 8 mm, yielding the highest overall performance. As pin-fin density increases, the rise in the Nusselt number (approximately 8.7%) is lower than the increase in the friction factor (approximately 15.3%), leading to a decline in overall performance. Additionally, as the air flow rate increases, the Nusselt number increases significantly more than the drag coefficient, leading to an improvement in overall heat transfer performance of microchannel heat exchangers.