Numerical Investigation on Internal Structures of Ultra-Thin Heat Pipes for PEM Fuel Cells Cooling

Proton exchange membrane fuel cell (PEMFC) powered propulsion has gained increasing attention in urban air mobility applications in recent years. Due to its high power density, ultra-thin heat pipe technology has great potential for cooling PEMFCs, but optimizing the limited internal cavity of the heat pipe remains a significant challenge. In this study, a three-dimensional multiphase model of the heat pipe cooled PEMFC is built to evaluate the impact of three internal structures, layered, spaced, and composite, of ultra-thin heat pipes on system performance. The results show that the heat pipe cooling with the composite structure yields a lower thermal resistance and a larger operating range for the PEMFC system compared to other internal structures because of more rational layout of the internal cavity. In addition, the relationship between land to channel width ratio (LCWR) and local transport property is analyzed and discussed based on composite structural heat pipes. The heat pipe cooled PEMFC with a LCWR of 0.75 has a significant advantage in limiting current density and maximum power density compared to the LCWRs of 1 and 1.33 as a result of more uniform in-plane distributions of temperature and liquid water within its cathode catalyst layer.