*2.5. Grid Independence Verification*

In order to verify that the numerical simulation results are not related to the number of grids, five grid numbers (234,149, 1,192,719, 1,457,725, 1,959,970 and 2,481,860) are selected for numerical simulation when the inlet mass flow is 0.002 kg/s. In Figure 4, we present a partial view of the grid of model 3. Hypermesh finite element meshing software and the hexahedral meshing method are used to encrypt the meshes to test the independence of meshes. The numerical simulation results show that when the grid number is 234,149, the numerical simulation results have the maximum deviation. Comparing the numerical simulation results of the models with the grid number of 1,959,970 and 2,481,860, it is found that the deviation between them is relatively small, and the numerical simulation results are very close, indicating that the grid number between 1,959,970 and 2,481,860 can be selected as the grid number of numerical simulation, but the larger the grid number is, the longer the calculation time will be. Considering the calculation accuracy and calculation time comprehensively, we select 1,959,970 here as the number of grids for numerical simulation. Table 3 shows the grid independence verification.

**Figure 4.** Local mesh of model 3.


**Table 3.** Grid independence verification.

#### *2.6. Model Verification*

In order to verify the reliability of the model, the research results of relevant materials are consulted, and the numerical simulation results are compared with the results of Baek's [40] research in Figure 5. In the numerical simulation, the Model F studied by Baek is used as the model, and the geometric structure and operating parameters (heat flux, inlet temperature, mass flow rate) were set to the same as the reference. It can be analyzed from the figure that when the inlet mass flow is 2 × <sup>10</sup>−<sup>3</sup> kg/s, the numerical simulation results in this paper are the lowest compared with those in the references. When the inlet mass flow rate is 6 × <sup>10</sup>−<sup>3</sup> kg/s, the numerical simulation results are the largest, approximately 10.1%. The results further verify the reliability of the numerical simulation method used in this study.

**Figure 5.** Model verification [36].
