Hot spot temperature optimization of turbulent heat convection systems: Application to battery thermal management systems

Abstract

Reduction of hot spot temperature is extremely important for power devices. Optimization equations using variational method are effective approaches to analyze convective heat transfer process. However, it is still lack of turbulent convective heat transfer optimization equations for minimization of hot spot temperature. In this work, the turbulent convective heat transfer optimization is investigated using variational method, with the aim of minimizing the hot spot temperature at customized regions. A continuous function that characterizes hot spot temperature is adopted as the objective function. The optimization equations with fixed total viscous dissipation are derived using the variational method, by solving which, the optimal flow field is obtained to achieve the minimum hot spot temperature. Subsequently, the developed optimization equations are applied to optimize the flow fields of the battery thermal management systems with different flow patterns. Numerical results demonstrate that the optimal flow fields from the developed optimization equations achieve lower hot spot temperature and temperature difference inside the battery pack, as compared to those obtained using extremum entransy dissipation in previous studies. Combined with the flow resistance network model, an iterative optimization strategy based on the optimal flow fields is further developed for structural design of the systems. The optimized systems exhibit superior performance in terms of hot spot temperature and temperature difference compared to the original systems before optimization. Finally, the effectiveness of this optimization strategy is validated by experiments. Compared with the systems before optimization, the experimental system with optimized parallel channel widths reduces the hot spot temperature and temperature difference by 6.3 K and 74 % respectively, and the system with optimized inlet defector reduces the hot spot temperature and temperature difference by 5.4 K and 67 % respectively. The optimal flow fields obtained from the developed optimization equations provide valuable insights for designing turbulent convective heat transfer systems which aim at reducing hot spot temperature, and the proposed strategy based on the optimal flow field shows great potential for efficient structural design of battery thermal management systems.