Investigation of the two-phase flow and heat transfer characteristics with different inlet and outlet arrangements in the ionic liquid compressor for the hydrogen refuelling station

The ionic liquid compressor is a prospective device for hydrogen pressurisation in the hydrogen refuelling station. Ionic liquids are introduced into the compressor chamber between hydrogen and the free piston for lubrication, sealing and cooling. Therefore, it is essential to investigate the two-phase flow and heat transfer since they impact the operational efficiency of the compressor. In this research, numerical simulation using the volume of fluid method was taken out to study the two-phase flow and heat exchange characteristics of hydrogen and ionic liquids in one compression process with four different inlet and outlet arrangements. The results showed that the inlet flow shock caused severe deformation of the phase interface, producing a large number of droplets and bubbles, which significantly enhanced the heat transfer. This deformation was greatly influenced by inlet and outlet arrangements. In general, the axial inlet design caused more obvious interface distortion than the radial one, enlarging the heat transfer area while also raising the risk of the piston being exposed. The recommended structure was the axial decentralised inlet form, which avoided piston exposure while maximizing the heat transfer area, with a hydrogen temperature rise of 16.24 K and a polytropic index of 1.11.