Experimental investigation and modeling of airside heat transfer characteristics based on dual-working-fluid for microchannel finned air-oil heat exchanger

To manage increasing thermal loads in aeroengines, this study proposes a novel surface air-oil heat exchanger (SAOHE) with microchannel fins that eliminates the need for high thermal conductivity materials. Compared to conventional titanium SAOHEs, the new design improves the comprehensive performance which defined as the ratio of heat transfer rate to pressure drop under high Reynolds number conditions (the ratio of the evaluation index R_p,f/R_p,mf exceeds 1). A new dual-working-fluid method is introduced to determine the airside heat transfer coefficient (HTC) without relying on accurate oil-side HTC measurements. Notably, when the thermal resistance ratio of the hot and cold sides exceeds 9 and 19, the deviation of the cold side thermal resistance calculated with and without accounting for hot side thermal resistance remains under 10% and 5%, respectively. Based on these findings, a new air-side Nusselt number correlation was developed. The experimental results significantly higher than the values predicted by Chang and Wang correlation for louvered fins and slightly lower than the values predicted by Gnielinski correlation, offering valuable guidance for the design of high-performance heat exchangers in aeroengine applications.