Numerical study of multiphase heat transfer through liquid films in a heat exchanger channel

Abstract

Designing thermal management systems (TMS) for hydrogen fuel cell-based electric aviation applications presents significant challenges, often requiring huge liquid-to-air heat exchangers (HEX) that utilize ambient air to cool and maintain the fuel cells at their operating temperature. Multiphase heat transfer offers substantial improvements over conventional single-phase systems by leveraging the latent heat of the liquid-gas phase change process. In this context, the spray injection of liquid water into the HEX duct, configured in an open loop, can provide significant improvements by wetting and forming a thin liquid film at the air side of the heat exchanger. We investigate this multiphase heat transfer phenomenon considering a single passage of a plate heat exchanger. The study aims to extrapolate these findings for the design of larger heat exchangers by providing crucial data on the local Nusselt numbers and their variations with various parameters like temperature, channel geometry, surface treatment, wetted area, and air mass flow rate.