Qualitative analysis of the coupling effect of fluid velocity distribution in microchannels on the performance of water-cooling lithium-ion batteries system

Lithium-ion batteries are the direct power sources of electric vehicles, but their high heat flux density restricts their development. Microchannel heat sinks (MCHS) can assist in heat dissipation to overcome this. The distribution of fluid velocity among microchannels has a considerable effect on the performance of MCHS for a water-cooling lithium-ion batteries system. In this paper, a new microchannel heat sink with high depth to width aspect ratio is proposed and the influence of four different aspect ratios on the distribution of fluid velocity among microchannels and heat transfer performance of MCHS was numerically studied by computational fluid dynamics (CFD). The results showed that at the same inlet flow rate, the larger the aspect ratio of the microchannels, the better the uniformity of the internal fluid velocity. The heat performance of microchannel structures with four different aspect ratios for a water-cooling lithium-ion batteries is further investigated experimentally. Compared with the simulation results of the fluid velocity distribution, the coupling effect between the fluid velocity distribution in the microchannels and the heat dissipation performance of a water-cooling lithium-ion batteries is analyzed. The results fully demonstrated that a larger aspect ratio of the microchannels results in a better heat dissipation performance on the surface of the lithium-ion batteries. Optimizing the aspect ratio of the microchannels to facilitate a relatively uniform velocity distribution to improve heat dissipation performance of the water-cooling system may be a key factor to be considered, which provides a new idea for passive thermal management of batteries.