Assessment of an inverse organic Rankine cycle system for the ECS of a large rotorcraft adopting a high-speed centrifugal compressor and a low GWP refrigerant

This study concerns the assessment of a novel concept for the Environmental Control System (ECS) of large rotorcraft, based on Vapour Compression Cycle (VCC) technology. Its uniqueness stands in the adoption of an electrically driven high-speed 6-8 kW centrifugal compressor, in place of the traditional volumetric machine. A steady-state model of the system has been developed and implemented using the Modelica acausal modelling language. The working fluids selected for this investigation belong to the class of low-Global Warming Potential (GWP) refrigerants. The results show that to obtain feasible compressor designs, and in particular sufficiently large flow passages, a high molecular complexity fluid must be employed as it results in adequate volume flow rate. However, compared to fluids made of simpler molecules, heat exchangers are larger and possibly heavier. The tradeoff between thermodynamic performance, weight, volume, aircraft drag penalty and system integration in general is being investigated.