## 4 Numerical Simulation Results on Heat Transfer Characteristics
### Different Volume Concentrations of Ethylene Glycol Aqueous Solution
#### 4.1.2 Ethylene Glycol Aqueous Solution of 50% and 30% Volume Concentration  
The maximum flow rate of the aqueous ethylene glycol solution with a volume concentration of 50% appeared in the first row of the cold plate, and the flow rates of the two adjacent T/R components were 0.0720 kg/s and 0.0727 kg/s. The minimum flow rate appeared in the eleventh row of the stubs, and the flow rates of the two adjacent components were 0.0537 kg/s and 0.0561 kg/s. The maximum flow rate of the 30% volume concentration of ethylene glycol solution appeared in the stubs. The maximum flow rate of the aqueous glycol solution with a volume concentration of 30% appeared in the third row of the cold plate, with flow rates of 0.0711 kg/s and 0.0725 kg/s in the two neighboring T/R assemblies, while the minimum flow rate appeared in the tenth row of the branch, with flow rates of 0.0524 kg/s and 0.0548 kg/s in the two neighboring assemblies. The reasons for the different locations of the maximum and minimum flow rates of different concentrations of ethylene glycol solutions are the different physical parameters of different volume fractions of ethylene glycol solutions, resulting in different flow resistance and flow pressure, which ultimately lead to different flow characteristics of the fluids in the cold plate. The flow rate of each component is within 20% error of the average flow rate. The method in Section 4.1.1 was used to demonstrate the effect of a 50% volumetric concentration of aqueous ethylene glycol and a 30% volumetric concentration of aqueous ethylene glycol on the heat exchange of the cold plate. The heat transfer method is forced liquid cooling with the heat flow density set to 48 W/cm\({}^{2}\). Figure 15a,b show the temperature changes on the surface and inside of the cold plate when the flow rate in the cold plate assembly is at a minimum of 50% glycol concentration, and the maximum temperature of the cold plate is 297.76 K and the minimum temperature is 293.56 K under the power of heat source of 48 W/cm\({}^{2}\). Figure 15a shows the temperature change on the contact surface between the cold plate and the T/R module, and Figure 15b shows the temperature inside the cold plate. It can be seen from Figure 15b that the heat distribution of the whole cold plate is relatively uniform, and the temperature of the coolant in the cold plate is low, which can exchange heat with the cold plate well and take away the heat in the cold plate. Figure 15c,d show the cooling medium for the 50% concentration of glycol solution in the cold plate at the maximum flow rate of the cold plate temperature distribution. Figure 15c shows the cold plate and the T/R components of the temperature distribution of the contact surface; Figure 15d is the temperature distribution inside the cold plate, the maximum temperature of 297.28 K, the lowest temperature of 293.38 K, and the temperature difference between the cold plate of 4 K.  
The same method was used to verify the effect of 30% concentration of aqueous ethylene glycol solution as a cooling medium on the heat exchange of the cold plate. It was found that the cooling effect of 30% concentration of glycol solution under the heat source power of 48 W/cm\({}^{2}\) was the same as that of 50% concentration of glycol aqueous solution. The maximum temperature of the surface of the cold plate at the maximum flow rate is 296.51 K, and the maximum temperature of 50% concentration of ethylene glycol solution is 297.28 K, with a difference of less than 1 K, which indicates that the concentration of ethylene glycol aqueous solution does not have much influence on the heat exchange effect of the cold plate under the heat source power of 48 W/cm\({}^{2}\). Figure 16 shows the temperature distribution of this surface of the cold plate when 30% concentration of glycol aqueous solution is used as the cooling medium; the temperature distribution inside the cold plate is the same as that inside the cold plate with 50% concentration of glycol aqueous solution, and the temperature distribution is more uniform.