Experimental study on heat transfer characteristics of graphite powders based composite phase change materials

Phase change material has become a research hotspot in the field of passive thermal management for lithium-ion batteries due to its low price and high latent heat. However, the low thermal conductivity limits the thermal efficiency of thermal management system. In this paper, the graphite powders/paraffin binary composite with a superior ratio suitable for battery thermal management was prepared, and the ternary composite was obtained by introducing nickel foam. The temperature fields during melting were visually observed through thermal imaging, and the influence mechanism of graphite powders and nickel foam on the movement pattern of the phase transition interface was investigated through comparative experiments. The results showed that the addition of nickel foam significantly accelerated the pushing rate of the phase transition interface in the lower and middle regions. The temperature difference along the height direction of both paraffin and binary composite increased with the increase of distance from the heating surface, while that of ternary composite showed no significant correlation with the distance. At a distance of 75 mm from the heating surface, the maximum temperature difference along the height direction of the ternary composite was 47.58 % and 25.43 % lower than that of the paraffin and binary composite, respectively. This paper also discussed the recovery periods for the thermal storage capacity of phase change materials. The ternary composite was the fastest to recover its thermal storage capacity, with its recovery period being 22 % shorter than that of the other materials. It also exhibited the best temperature uniformity. Its maximum temperature difference was 28.77 % lower than that of the other materials.