Experimental investigation of heat transfer characteristic and pump power analysis on PEMFC cooling plate with insulating coatings

Thermal conductivity of the coolant for liquid cooling fuel cell, which is one of the key factors determining the cooling performance of the cooling system. Nanofluid is considered as desirable coolant due to their high thermal conductivity property, but its electrical property also cause leakage current. In this study, the supersonic plasma spraying technique was used to spray Al₂O₃ on the inner wall of the cooling channels to make an insulating coating to eliminate leakage current. However, the rough coating surface possibly affect the flow and its thermal resistance also affect the heat transfer. Heat transfer characteristics and pump power of deionized water, alumina nanofluids, and graphene nanofluids were investigated. The results show that, before spraying insulation coating, graphene nanofluid has lowest maximum temperature and index of uniform temperature (IUT) at different pump power conditions, and it has the optimal cooling performance. As the pump power increasing, the effect of pump power on IUT gradually diminishes, the method of increasing pump power consumption to improve temperature uniformity is ineffective. The effective cooling coefficient of graphene nanofluid is highest at the same Re, and the convective heat transfer coefficient increases approximately linearly but not uniformly with increasing Re. After spraying the insulating coating, the maximum temperatures of the cooling plate are slightly reduced at different Re, the average reduction is 0.3 K, heat conduction from heat source by cooling channels slightly decreased, and the pump power of graphene nanofluid slightly increases, it increases by up to 2.7% at Re = 1500. It indicates that insulating coating do not have a significant effect on heat transfer and flow.