Modelling of near isothermal liquid piston gas compressor employing porous media for compressed air energy storage systems

The liquid piston gas compressor (LPGC) is a method of compressing gases with improved efficiency. Key to the success of this device is its operation in as close to an isothermal state as possible. This paper presents high-fidelity, three-dimensional, unsteady Reynolds-averaged Navier-Stokes (uRANS) simulations to better understand the heat transfer and fluid physics involved in the liquid-piston-driven compression process. Furthermore, the uRANS is coupled with conjugate heat transfer to study using porous media inserts to manage the temperature increase. We simulate the entire cylinder/porous media arrangement using the volume of fluid (VOF) method to analyse the turbulent, multiphase physics and the fluid-structure interaction, providing a greater understanding of this process. It also investigates how porous media inserts perform against the no- insert (baseline) cases in producing a near-isothermal process. The porous mediums used are parallel plates, interrupted plates, and metal foam, all produced from aluminium. Results show that temperature rises within the cylinder can be reduced by as much as 120 K, depending on the choice of porous insert. This temperature reduction translates to an increase of up to 13% in compression efficiency.