## 4 Results and Discussion
### Air-Cooling BTMS without AFHS  
Figure 3a shows the temperature distribution of the battery without AFHS at the mass flow rate \(q_{m}=10\) gs\({}^{-1}\). It can be seen that the temperature downstream of the battery was  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Sample** & **Mass Flow Rate, gs\({}^{-1}\)** & **10** & **15** & **20** & **25** & **30** & **35** & **40** \\ \hline [PERSON] et al., \({}^{\circ}\)C & 34.9 & 33.5 & 32.3 & 31.6 & 31.5 & 31.2 & 30.8 \\
10 PPI 0.682 & Present Study, \({}^{\circ}\)C & 35.39 & 33.83 & 33.07 & 32.61 & 32.3 & 32.07 & 31.9 \\  & Error, \% & 1.4 & 0.99 & 2.38 & 3.2 & 2.54 & 2.8 & 3.58 \\  & [PERSON] et al., \({}^{\circ}\)C & 34.9 & 33.8 & 32.6 & 32.1 & 31.8 & 31.3 & 31.1 \\
20 PPI 0.774 & Present Study, \({}^{\circ}\)C & 35.66 & 34.1 & 33.3 & 32.89 & 32.56 & 32.33 & 32.15 \\  & Error, \% & 2.17 & 0.89 & 2.27 & 2.44 & 2.4 & 3.29 & 3.37 \\  & [PERSON] et al., \({}^{\circ}\)C & 35.2 & 33.8 & 32.7 & 32.1 & 31.8 & 31.6 & 31.5 \\
40 PPI 0.923 & Present Study, \({}^{\circ}\)C & 37.07 & 35.55 & 34.78 & 34.27 & 33.88 & 33.57 & 33.32 \\  & Error, \% & 5.33 & 5.18 & 6.37 & 6.76 & 6.55 & 6.25 & 5.78 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of battery temperature with AFHS [35].  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mesh No.** & **Mesh 1** & **Mesh 2** & **Mesh 3** \\ \hline No of element & 321,489 & 928,746 & 3,356,160 \\ T\({}_{\text{av}}\), \({}^{\circ}\)C & 31.80 & 31.82 & 31.82 \\ T\({}_{\text{max}}\), \({}^{\circ}\)C & 33.32 & 33.32 & 33.35 \\ T\({}_{\text{min}}\), \({}^{\circ}\)C & 29.67 & 29.70 & 29.69 \\ \(P_{d}\), Pa & 61.34 & 61.49 & 61.22 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Grid independency tests.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Mass Flow Rate, gs\({}^{-1}\)** & **10** & **20** & **40** & **60** & **80** & **100** \\ \hline [PERSON] et al., \({}^{\circ}\)C & 58.1 & 45.9 & 40.0 & 37.2 & 35.5 & 34.7 \\ Present Study, \({}^{\circ}\)C & 57.50 & 45.67 & 38.99 & 36.44 & 35.08 & 34.22 \\ Error, \% & 1.04 & 0.50 & 2.53 & 2.05 & 1.19 & 1.39 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Comparison of battery temperature without AFHS [35].  
higher than that upstream along the air flow direction. The reason for this phenomenon is that when the air flows through the battery surface, the air first transfers heat with the upstream of the battery, resulting in the rapid reduction of the cooling capacity of the air and reduces the heat transfer performance downstream. Hence, the battery temperature is not evenly distributed. Figure 3b shows the pressure drop \(P_{d}\) between inlet and outlet without AFHS; it can be seen that the \(P_{d}\) increased gradually with the increase of mass flow rate \(q_{m}\). The average temperature \(T_{av}\) and temperature difference \(T_{d}\) of the battery under different mass flow rates of cooling air are shown in Figure 3c,d, respectively. Obviously, there was a negative correlation between the \(T_{av}\) and the \(q_{m}\). The \(T_{av}\) decreased with the increase of \(q_{m}\). In order to keep the maximum temperature of the battery lower than 40 \({}^{\circ}\)C, at least 15 gs\({}^{-1}\) of cooling air is required. Similarly, the temperature difference \(T_{d}\) also decreases with the increase of \(q_{m}\), and the \(T_{d}\) is less than 3 \({}^{\circ}\)C at 15 gs\({}^{-1}\) of cooling air.