The thermal management of next-generation hybrid electric regional aircrafts poses critical challenges due to extreme heat loads, which could reach more than 2 MW and must be dissipated. This rejected heat can be used in a passive system such as Thermoelectric Generators (TEGs), which can directly convert thermal energy into electrical energy. This work is carried out in the framework of the EU Clean Aviation-funded project TheMa4HERA and it numerically explores the possibility of integrating thermoelectric (TE) technology in the next generation of regional aircrafts. Two case studies are considered: energy recovery from the outflow valve originally used to control the pressure of the cabin and the integration of TEG modules in skin heat exchangers used to partially dissipate heat coming from the fuel cells and/or from the power electronics. The results will permit us to understand the feasibility of implementing TEG technology into these specific conditions in terms of overall power generation. The findings indicate that while TEG integration in the outflow valve offers limited power density, the skin heat exchanger shows significantly higher potential for effective energy recovery.

The development of future electrical aircraft, such as the Hybrid-Electric Regional Aircraft (HERA) platform, presents challenging cooling demands due to the heat generated by electric powerplants, fuel cells and power electronics. Traditional heat exchangers in ram air channels may not be sufficient, necessitating alternative solutions like Skin Heat Exchangers (SHXs) to enhance heat transfer and reduce parasitic drag. Aircraft drag reduction and efficiency increase are expected with the integration of SHXs in two-phase cooling systems. This study employs Computational Fluid Dynamics (CFD) models, specifically the Volume of Fluid (VOF) multiphase model together with the Lee model, to simulate the condensation process of two Hydrofluoroolefin (HFO) refrigerants in SHX channels (R1233zd(E) and R1234yf). An analytical model based on empirical equations is used to preliminarily correlate and validate the CFD results, showing deviations below 15%. The simulations reveal distinct flow behaviours for each refrigerant, influenced by the differences in liquid and gas densities. The study also establishes a basis for understanding and selecting the inverse of the relaxation time coefficient, which is crucial for multiphase CFD modelling. The CFD models used in this article could be of great importance for future SHX design optimization.