• Energy Research

With the proposes of improving occupant's thermal comfort and reducing the air conditioning power consumption, the present research carried out a comprehensive study on the surface thermal conductions and their influence parameters. A numerical model was built considering the transient conduction, convective and radiation heat transfer inside a vehicle cabin. For more accurate simulation of the radiation heat transfer behaviors, the radiation was considered into two spectral bands (short wave and long wave radiation), and the solar radiation was calculated by two solar fluxes (beam and diffuse solar radiation). An experiment was conducted to validate the numerical approach, showing a good agreement with the surface temperature. The surface thermal conditions were numerically simulated. The results show that the solar radiation is the most important factor in determining the internal surface thermal conditions. Effects of the window glass properties and the car body surface conditions were investigated. The numerical calculation results indicate that reducing the transitivity of window glass can effectively reduce the internal surface temperature. And the reflectivity of the vehicle cabin also has an important influence on the surface temperature, however, it's not so obvious as comparison to the window glass.

Abstract The dosage of phase change material (PCM) used is a core parameter of the PCM-based thermal management module. In this paper, a PCM-based thermal management module is built, then its numerical model is established and validated by experimental data. To accurately evaluate the influence of PCM dosage on battery temperature, a parameter called “heat ratio” is proposed. The detailed parametric study of the PCM dosage and its effect coupled with the phase transition temperature, the thermal conductivity of PCM, and the heat transfer coefficient are systematically conducted under a single discharge process and discharge-charge cycle conditions. The results indicate that the “heat ratio” between 0.75 and 1 is relatively suitable for controlling the battery temperature in a single discharge process. Higher thermal conductivity of PCM is beneficial for improving the performance of cooling system as well as the utilization of PCM, and increasing the heat ratio of PCM can further reduce the temperature of the battery once the thermal conductivity reaches a threshold. The “heat ratio” bigger than 0.75 can guarantee the PCM with lower phase transition temperature exerts its advantage in controlling the operating temperature of battery in the case of short-term operation. On the other hand, under extreme working conditions or long-term operating cycles, a higher phase transition temperature will bring a better cooling performance. However, merely increasing the dosage of PCM is not feasible. To achieve a more stable and low power cooling effect, it is more effective to combine the passive and positive cooling strategy which has a reasonable convective heat transfer coefficient.

Abstract The hybrid thermal management scheme for lithium-ion battery combining the advantages of various thermal management strategies has been widely adopted. However, due to the complex influence parameters involved in the hybrid thermal management system, its optimal design has become a difficult problem. In this study, a hybrid thermal management system based on phase change material (PCM), liquid cooling, and heat pipe is first designed, and then a precise and reliable numerical heat transfer model is established. In order to optimize the system and improve the optimization efficiency, the Adaptive-Kriging-High dimensional model representation (HDMR) method is used to construct a surrogate model of the thermal management system, and the influencing factors sensitivity analysis and optimization design of the hybrid thermal management system are also conducted. The results show that the thermal conductivity of PCM, the thickness of PCM, the length of heat pipe and the velocity of inlet water have a significant influence on the maximum temperature and temperature difference of the battery system. According to the optimization design of these four factors based on the multi-objective particle swarm optimization (MOPSO), it is found that the optimized thermal management system has the best ability to dissipate heat and maintain temperature uniformity as compared to the original design. In addition, this optimization system has the ability to prevent thermal runaway propagation under the condition of thermal abuse conditions. With these prominent performances, the proposed method is expected to provide insights into the engineering design and optimization of the battery thermal management system for electric vehicle.