Study of Phase Change Thermal Management Architecture for Series-Hybrid Powertrain in Unmanned Aerial Vehicles 2023-01-0130

The applications of unmanned aerial vehicles (UAV) are growing exponentially with advances in hybrid powertrain architecture design tools. The thermal management system (TMS) as an integral part of the powertrain architecture greatly affects the system performance of aerial vehicles. In this study, a comparative analysis of two types of thermal management technologies for a UAV with a series-hybrid powertrain architecture was performed. Conventional TMS based on single-phase (no phase change) cooling technologies using air and liquid (e.g., antifreeze water mixture and oil) as heat transfer fluid has been commonly used because of simple design and operation, although it is considered to be inefficient and bulky. As advanced designs, phase change-based TMS is being slowly adopted although it promises superior cooling capabilities. A parametric study was performed to analyze UAV cooling performance in terms of weight, volume, and required pumping power of TMS by varying the heat dissipations of heat-generating components (ICE, generator, motor, and battery) at different ambient temperature varied by UAV altitudes. In this study, as a baseline design, liquid cooling was applied for internal combustion engine (ICE), electric generator and motor and air cooling was considered for rechargeable battery system. Furthermore, latent-energy thermal energy storage using a phase change material is considered for the TMS architecture study, which is specifically helpful in highly transient operations, to help reduce temperature fluctuations. The conventional TMS was compared, under fixed temperature constraints, with an advanced TMS using a pumped two-phase loop for the engine cooling by replacing the single-phase liquid cooling. From the analysis, it was found that the advanced TMS reduces the weight, volume, and pumping power consumption by 12, 10, and 23 %, respectively, as compared to the conventional TMS.