Optimization study on the vortex generator structure of an adaptive heat exchanger

Abstract

The fuel/oil heat exchanger is a critical component in the thermal management of aircraft engines. However, traditional heat transfer design for specific operating conditions can only meet thermal demands by adjusting external pipes and window openings, which is often insufficient. To address this issue, we propose an adaptive heat exchanger with shape memory alloy (SMA) as the thermal source generating structure. This study combines numerical simulations and flow heat transfer experiments to investigate the optimization of the adaptive heat exchanger by adjusting the SMA arrangement spacing and perforation design. The results show that reducing the SMA spacing ΔX (from 11 mm to 7 mm), the heat exchanger can significantly reduce the internal fluid dimensions and increase the secondary flow velocity. This not only enhances the heat transfer capability but also increases flow resistance. The maximum PEC value increased from 1.369 (Re = 2000) to 1.474, with a 7.7 % improvement in overall performance. Additionally, the heat transfer adjustment capability K_Nu and flow resistance adjustment capability K_f increased by 12.1 % and 38.0 % respectively (Re = 3000). Additionally, perforating the SMA strips improves the flow conditions between the SMA and the heat exchanger wall, significantly reducing the flow dead zone. Among the five perforation designs studied, elliptical perforation structures performed the best. When the SMA strips are fully deflected (ΔZ = 5 mm), the heat transfer adjustment capability of the elliptical perforation structure ΔX = 11 mm increased by 9.25 %, and the flow resistance decreased by 29.8 %. This study establishes a robust theoretical framework for optimizing adaptive heat exchangers and provides valuable insights for their future practical applications.