PEM Fuel Cell Multiphase System

A multi-phase thermal fluid has been investigated and developed for a Proton Exchange Membrane (PEM) fuel cell. The system has been developed specifically for a 1.5kWe stationary PEM to enhance the thermal stability within the system, and to improve the reliability and electrical efficiency. The multi-phase system is proposed to act as a novel method of heat recovery to buffer fluctuations in load and reduce parasitic loading by increasing fluid thermal capacitance and reducing flow velocities. The multi-phase thermal system is made up of a two component fluid. Phase change materials have been selected and processed using a novel method of micro-encapsulation. These have been mixed and suspended in a working fluid to form a slurry which was pumped around the system. Investigation into the additional thermal capacitance and improved thermal conductivity of the slurry was undertaken to assess reductions in pumping loads. Thermal analysis and experimental tests have revealed significant increase in thermal buffering which offers the potential to enhance system stability. This in conjunction with reduced pumping power could improve the overall electrical efficiency of the fuel cell. This work has built upon previous thermophysical development of multiphase fluids and has developed a suitable microPCM slurry for further experimental tests with a fuel cell.