## 1 Introduction
However, for the problem of thermal uniformity caused by mass maldistribution in cooling plates used in EV batteries, there are still few papers focusing on it. The significance of mass maldistribution on temperature uniformity can be shown in a micro-channel heat sink used in electric devices and other systems. [PERSON] et al. [14] presented a multi-pass serpentine flow-field that could maximize under-rib convection in a given cell area and was expected to enhance under-rib convection and transport, thereby improving the performance and temperature uniformity of polymer electrolyte membrane fuel cells. [PERSON] et al. [15] conducted a detailed numerical study on the effect of five different inlet/outlet configurations on flow distribution through comparison of temperature contours. [PERSON] et al. [16] developed different parallel channels using a manifold with baffles and found the design with one to six bends could improve heat transfer and temperature uniformity significantly, but temperature non-uniformity was not improved by using more than four bends. [PERSON] et al. [17] investigated the comprehensive performance of pressure drop and heat transfer based on rectangular parallel mini-channels with three different section surface areas and found that large ratios of height to width manifested a better comprehensive performance. [PERSON] et al. [18] employed numerical simulation to study the uniformity of velocity and temperature fields in parallel channel heat sinks and found the channels with derangement presented better performance when considering pressure drop and mean temperature of heat surfaces. [PERSON] et al. [19] carried out extensive experiments to study the parameters affecting pressure drop and temperature distribution across parallel channels, such as channel hydraulic diameter, flow configurations (U, Z, I type), and chip power, and found the configuration of inlet and outlet was important for heat performance. [PERSON] et al. [20] analyzed the temperature distribution inside a Lytron CP20 microchannel cold plate under constant heat flux. The pressure drop across the first microchannel was very low due to the resistance to the flow caused mainly by the impact of the fluid to the wall of the outlet tube. Conversely, the pressure drop across the last channel was high because, due to the wall effect, the fluid coming from the previous channels pushed the fluid from the last one to the exit. [PERSON] et al. [21] carried out an experimental evaluation of the combined effect of void volume and inlet flow maldistribution to the thermal performance of active magnetic regenerators and found that the negative impact of inlet flow maldistribution on the regenerator effectiveness was more significant than that of void volume. According to literature above, few have researched the effect of mass maldistribution on temperature uniformity of cooling plates, although many have researched micro-channels; however, their results cannot be applied directly to battery cooling as they are working at a much smaller scale dimension. The mass maldistribution can be induced by the variations of the amount of flowing mass, inlet and outlet arrangement, coolant flowing status (laminar or turbulent), and flowing channel configuration, which is considered to be the most important factor according to the studies of micro-channel and other systems. Therefore, the objective of this paper is to apply numerical analyses on different flowing channels in order to improve thermal uniformity (in terms of mass uniformity). The effect of channel configuration on mass maldistribution and pressure drop is compared, and serpentine channel is selected for further optimization by orthogonal experiment and range analysis methods due to its comprehensive performance. The study aims to reveal design principles about how channel configuration acts on mass maldistribution, and to demonstrate that significant performance gains can be realized with optimization techniques that can be utilized in battery cooling plates.