Experimental study on a novel compact cooling system for cylindrical lithium-ion battery module

Lithium-ion batteries generally require adequate thermal management to achieve optimal performance and avoid thermal runaway. Compactness and light-weight are of critical importance to the lithium-ion power battery system. A novel compact cooling system for thermal management of cylindrical lithium-ion battery packs is proposed, which is a hybrid of phase change material and heat pipe cooling systems. The heat pipe and phase-change-material tube are manufactured with aluminum (which is light in weight) and are specially designed to fully utilize the empty space in-between cylindrical batteries in tight contact. Some annular thin fins are integrally molded to the heat pipe condensation section to enhance convective heat removal to the ambient. The phase change material used is paraffin and the working fluid of heat pipe is acetone. A module contains 40 18650-type batteries, 13 phase-change-material tubes and 14 heat pipes is assembled. Experiments conducted testify the effectiveness of the hybrid thermal management system and reveal as well the effects of heat pipe and phase-change-material tube. It is found that the well-equipped hybrid cooling system can control the highest temperature and the maximum temperature difference in the battery module at about 47.7 degrees C and 2.5 degrees C respectively, during 2C discharge process and under the condition of natural air convection to 25 degrees C ambient. The heat pipe is found to be more effective at lowering the battery temperature rise while the phase-change-material tube appears to be more effective at reducing the temperature non-uniformity in the battery module. Moreover, the effects of phase-change-material tube are found to be sensitive to the ambient temperature; the phase-change-material tube appears to be most effective if the ambient temperature makes the battery module in operating experience a temperature range that can rightly ensure a complete melting of the phase change material.