**3. Simulation Results and Discussion**

#### *3.1. Temperature Distribution*

Figure 6 shows the center plane temperature distribution of six different flow fields, and the cooling plate area of six different flow fields is 180 mm × 180 mm, where b, c, d, e, f are arranged with four inlets and four outlets, and the inlet mass flow is 0.002 kg/s. Figure 6a is a traditional single-channel serpentine flow field cooling plate. As can be seen from the figure, the heat dissipation performance of the single-channel flow field is the worst. The temperature distribution in the upstream of the flow channel in Figure 6e is below the overall average temperature, but the local temperature in the middle and downstream regions is high. Because the obstruction of the uniform plate leads to the low flow rate of the cooling liquid, the waste heat absorbed by the coolant from the bipolar plate cannot be discharged in time, resulting in the high local temperature of the cooling plate. Figure 7 shows the velocity distribution of the flow field. It can be seen that the velocity of this flow field is smaller than that of other flow fields due to the blockage of

the uniform plate. In Figure 6b, due to the zigzag circling of a single channel, the local temperature distribution is uneven. Later, the optimization design will be carried out according to the design characteristics of the flow field. As can be seen from Figure 6c, the flow field temperature gradually increases from the left inlet to the right outlet. Figure 6f shows the temperature distribution of the honeycomb cooling flow field. It is observed that the overall temperature distribution upstream of the cooling plate is uniform and low, but the local temperature downstream is too high. Although the flow field of the honeycomb structure can make the coolant evenly distributed, it is still unable to avoid fluid blockage, resulting in a locally high temperature downstream. Figure 6d shows the temperature distribution of the multi-helical flow field. Due to the long length of the flow channel, there is an obvious temperature difference from inlet to outlet, but the overall situation is better than that of Figure 6a.

Figure 6d shows the temperature distribution of the multi-helical flow field. It can be seen from the figure that the temperature at the corner of the multi-helical flow field is slightly higher than that of the surrounding environment. This is due to the reflux phenomenon of the fluid at the corner of the cooling channel. As shown in Figure 8, due to the reflux phenomenon, a small part of the fluid stays at the corner and cannot be discharged in time, while the heat of the cooling plate is continuously transmitted to the remaining coolant, resulting in a local temperature difference.

**Figure 8.** Local velocity of multi-helical flow field.

Table 4 shows and compares the parameters of six different cooling plates, including pressure drop, temperature difference, maximum temperature and temperature uniformity index. The temperature difference is the difference between the maximum temperature and the minimum temperature of the cooling plate in the simulation steady state. It can be seen from the table that the maximum temperature and temperature difference of the traditional single-channel serpentine cooling flow field are the maximum values of the six cooling channels, and the temperature is also the most uneven, showing inefficient performance. As can be seen from Figure 9c, the overall pressure of model 2 is high and the coolant is blocked seriously, which is reflected in Table 4 with the maximum pressure drop.



The fluid of model 4 and model 5 has no obvious blockage, and the pressure drop of both is far less than model 0, model 1, model 2 and model 3. As can be seen from Figure 6, the flow rate of the coolant of model 4 and model 5 in the channel is small, in which the fluid uniform plate not only makes the coolant evenly distributed, but also hinders the transverse diffusion of the fluid body, making the flow rate of model 4 the minimum. It shows the highest temperature second only to the traditional single-channel serpentine flow field. The coolant flow rate of model 1, model 2 and model 3 in the channel is large and the pressure drop is high, but the higher flow rate promotes the discharge of waste heat, showing the minimum temperature difference and the minimum maximum temperature.

**Figure 9.** Pressure distribution.
