EXPERIMENTAL INVESTIGATION ON THE HEAT TRANSFER PERFORMANCE OF HEAT PIPES IN COOLING HEV LITHIUM-ION BATTERIES

The lithium-ion battery, the energy source and storage device for an electric vehicle, is susceptible to operating temperature. Improper temperature control of the battery would lead to capacity and lifecycle degradation, and higher safety risks. Methods of controlling the temperature such as air cooling, liquid cooling, and PCM have been widely investigated but a few studied the use of heat pipes. The objective of this paper is to present experimental works conducted to investigate the feasibility of using heat pipes in the thermal management of lithium-ion battery cells. The battery cells were represented by two proxy cells with a heat source ranging from 5 W to 20 W/cell. The evaporator section of the heat pipes was attached to the surfaces of the cells, and the condenser section was exposed to air forced convection. The heat generation rate, the length of the condenser section, and the air velocity were varied, and the surface temperature of the proxy battery cells was recorded. The results showed that the heat pipes are able to reduce the battery cell temperature by at least 14.7 degrees C and improve the total thermal resistance by an average of 41.6%, when compared with the battery without any thermal management. It was also observed that the heat pipe thermal management system is able to control the temperature below 50 degrees C when the heat generated by each cell is less than 10 W. The temperature difference within the cell is also kept below the desired limit of 5 degrees C when the length of the condenser is 100 mm or less.