Analysis of Heat Pipe Impact on PCM Based Battery Thermal Management

We have performed a numerical and experimental study on the impact of adding heat pipes to a PCM based battery thermal management system. Phase change materials (PCMs) are used as a battery thermal management system to absorb heat by melting in a specific temperature range, leading to a temporary constant and uniform temperature around battery cells. They also can be used as mechanical support for battery cells and safety measure to prevent fire propagation in case of thermal runaway. The main drawback of these materials is their low thermal conductivities. Our proposed approach is the integration of heat pipes with PCM as a hybrid system to take advantage of both technologies including the temperature peak absorption and structural support of PCM along with very high effective thermal conductivity, temperature uniformity and passive operation of heat pipes. Flat heat pipes integrated with PCM are tested with 18650 cells under various C-rates and ambient temperatures. A heat sink is attached to the condenser side of the heat pipe and the whole battery pack is covered with thermal insulating material to allow heat transfer only from the heat pipes. We have also performed numerical simulation on the system to simulate the heat pipe performance and have demonstrated that heat pipes contribute to transport of 40% of the pack heat to the ambient in a typical duty cycle. Moreover, it is shown that a after a typical intense duty cycle at high ambient temperature, the maximum pack temperature is still in the acceptable range allowing for an immediate charge.