ELECTRA: Enhanced Liquid cooling for ElectriC Traction systems in Recreational Aviation

The aim of this research project is to develop an innovative Power Supply Unit (PSU) for electric aircraft (EA) based on high efficiency thermal management system adopting two-phase fluids. Indeed, batteries in aircraft applications could be subjected to very stressful electric and environmental operating conditions. The PSU must be able to deliver high power that generates very high specific heat fluxes into the batteries with a consequent rapid increase of temperature that cause a sharp decrease in performance and lifetime. A solution to this problem may be the design and employment of an innovative Battery Thermal Management System (BTMS) with high efficiency. Nowadays, the aircrafts with Maximum Take-Off Mass (MTOM) lesser than 600 kg are widespread. In Italy these aircrafts are identified as “Apparecchi per il volo da diporto o sportivo (VDS)” but generally this category is named Light Sport Aircrafts (LSA). Our research project is devoted to this aircraft category and, in particular, in training LSA aircrafts requiring a limited flight time compatible with battery energy storage capability. In the proposed PSU the Li-Ion cells are submerged in a low boiling dielectric fluid (hereinafter main fluid) that allows an efficient heat transfer. The dielectric fluid transfers the heat generated by the battery to the enclosing frame which, in turn, dissipates it through the surrounding environment. Furthermore, Pulsating Heat Pipes (PHPs) are partially enclosed in the cells pack and they are submerged in the main fluid. The PHP device belongs to the category of passive two-phase capillary driven loops. From a technological point of view, a PHP is very simple and cost effective compared to other heat transport devices. Moreover, their compactness, flexibility, ability to work without an electrical energy input and the versatility to work in microgravity make them perfect for aircraft applications where size, weight and inertial forces values are crucial variables. The role of the PHPs implementation in the cooling system is to mainly dispose of thermal power peaks when the excessive load risks causing all the dielectric fluid to evaporate, thus producing a subsequent overheating of the gas phase and a consequent increase in pressure dangerous to the safety of the device. The PHPs will be specifically designed to support the heat transfer by the dielectric fluid before and during phase change. A combined numerical and experimental approach based on high-resolution/speed IR camera, CFD and inverse heat conduction problem solution techniques will be used to identify the local temperatures and heat fluxes. This will allow to optimize electric power unit for maximizing thermal performance.