Study of Different Flow Configurations and Heat Pipe Combination Effects in Air Cooling Systems

Abstract

The present work investigates the combined effect of flow rate pattern configuration and the presence of localized passive cooling systems such as heat pipes to improve the thermal performance of an air-cooling system. The combined heat pipe air-cooling system consists of 10 blocks (batteries) arranged in parallel and surrounded by 10 to 11 air passage channels; the blocks are subjected to variable heat generations. Previous studies have shown that air cooling systems do not provide a uniform temperature distribution when loaded with constant heat generation. Three flow configurations were numerically investigated: the U, Z, and I configuration, respectively. A three-dimensional numerical simulation was conducted to solve the continuity, momentum, and energy equations of the working fluid. The numerical model also included the presence of the ten blocks, heat pipe, and related boundary conditions. The heat pipe was modeled as a solid material with high effective thermal conductivity. The results from the three air configurations without the presence of heat pipes depict an increase in the temperature field in blocks 5, 6, 7, 8, and 9 for the Z-configuration; blocks 2, 3, 8, and 9 for the I-configuration; and blocks 3, 4, 5, and 6 for the U-configuration. The I-configurations show a better temperature distribution on the blocks compared with the U and Z configuration. Different flow airflow rates were also investigated to reduce the hot spot temperature fields on the blocks. No significant difference was found in increasing the air mass flow rate. After placing a heat pipe closed to the air channels of the block with a high peak in temperature for the three air cooling configurations, the performance of the air-cooling system improved. The number of blocks with higher spot temperature was reduced to blocks 7 and 8 for Z-configuration, blocks 3 and 8 for the I-configuration and blocks 4 and 5 for the U-configuration. The presence of the heat pipe increased the pressure drop between the inlet and outlet for the three configurations. The results have shown that the U-configuration experienced the lowest pressure drop, and the I-configuration presented the most uniform temperature distributions of the block. The results revealed potential thermal performance improvement by using heat pipes in localized hot spot regions in air cooling systems for Li-Ion batteries or other cooling systems subjected to continuous or intermittent heat generation.