Thermal properties of cooling tube battery pack embedded with triangle umbrella-shaped cellular structure

Abstract

To further enhance heat dissipation efficiency and temperature uniformity of battery pack, a novel cooling tube battery pack embedded with triangle umbrella-shaped cellular structure (TUCS) with negative Poisson’s ratio (NPR) is proposed. Firstly, heat generation models of battery cell are derived and temperature rise tests are conducted to verify the accuracy of heat generation theory and simulation models of lithium battery cell. Meanwhile, cooling tube battery pack with bidirectional serpentine tube is established, and the influences of different flow rates and directions of coolant, diameter of cooling tube and spoiler columns on heat dissipation efficiency of cooling tube battery pack are investigated through simulation analysis. Moreover, relative density of TUCS is calculated and thermal conductivity expressions of TUCS are derived by Maxwell-Eucken model. Subsequently, the embedded TUCS is taken as the medium to conduct heat between cooling tubes and battery modules. Then, the influences of structural parameters of TUCS on heat dissipation efficiency of cooling tube battery pack are determined. Further, the optimal TUCS with the needs of high heat dissipation efficiency, superior temperature uniformity and more lightweight space of battery pack is achieved. Similarly, density gradient of the TUCS can be defined and impacts of TUCS with density gradient distribution on thermal performances of battery pack are investigated. Eventually, the highest temperature and maximum temperature difference of the optimal cooling tube battery pack, cooling tube battery pack embedded with the optimal TUCS and cooling tube battery pack embedded with the optimal gradient distribution TUCS are obtained. Compared with the optimal cooling tube battery pack, the highest temperatures of another two cooling tube battery packs decrease 16.50 % and 16.48 %, and the corresponding maximum temperature differences decrease 93.06 % and 93.20 %, respectively. Meanwhile, the highest temperature and maximum temperature difference of another two battery modules are 303.76 K and 3.76 K at 5C discharge rate. The proposed cooling tube battery pack with the optimal gradient distribution TUCS can decrease the highest temperature and maximum temperature difference effectively.