## 4 Discussions  
It is observed that the modules located at the back of the analyzed battery segment (I = 3, 4) have lower values for heat transfer coefficients, the explanation being the increase in air temperature as it crosses the domain, as seen in Figure 8. In comparison, the first module has on average 20.4% higher coefficient values than the last module. This causes a lack of uniformity in the temperature distribution inside the segment, with a temperature difference of over 2.5 \({}^{\circ}\)C at the end of the 1960 s and a maximum temperature above the desired limit. In Figure 9, the general tendency of higher heat transfer coefficient values at the end sections of a cell (\(j\) = 4, 5) can be observed, based on the illustrations seen in Figure 6. The explanation of this tendency is that the segment housing obstructs the air from cooling the front sections of a cell (\(j\) = 1, 2) and it only starts coming into contact with the accumulators at their middle section. This means that at the front sections of each module's cells, there is some static air that heats up and therefore considerably reduces the cooling capacity. When increasing the air flow, the front sections of the cells show a greater improvement in the heat transfer coefficient, according to Figure 13. On average, doubling the air flow caused an increase in the convective heat transfer coefficient in the first section of the cells by 80.1%, compared to only 21.7% in the last section. This is caused by the higher free stream air velocity, which creates bigger turbulences at each opening in the housing, where the cross-section of the flow suddenly increases. These turbulences help the extraction of static air trapped between the housing and the first section of the cells, therefore significantly increasing the heat transfer coefficient values in this region. Moreover, the differences in coefficient values between the first and last module are reduced to 8.1%. All these factors enhance the uniformity of temperature distribution inside a cell and inside the whole battery segment as well, which can be seen in Figure 14. The maximum temperature difference in the analyzed battery segment is reduced from 2.52 \({}^{\circ}\)C to 1.67 \({}^{\circ}\)C, meaning a reduction of 33.7%, while the maximum temperature difference recorded in a single cell is reduced from 1.37 \({}^{\circ}\)C to 0.92 \({}^{\circ}\)C, corresponding to a reduction of 32.8%. The performed simulations show that the minimum air flow necessary to not exceed the temperature limit of 50 \({}^{\circ}\)C is 1140 m\({}^{3}\)/h. One should also notice the differences between the proposed mathematical model and the non-sectioned one. As illustrated in Figure 12, the maximum temperatures for the non-sectioned model are 1.5-3 \({}^{\circ}\)C higher than for the proposed model. Equations (9) and (10) demonstrate that there is a non-linear relation between heat transfer coefficient and thermal resistance, in a way in which higher heat transfer coefficients have an increasingly bigger impact on the thermal resistance and therefore on the battery cell temperatures. This means that using an average heat transfer coefficient for the entire surface of an accumulator, as presented in the other mentioned studies, will result in higher temperature values. By reading the convective heat transfer coefficients locally, the proposed sectioned mathematical model is able to simulate the cooling of the areas with a good heat transfer capacity. The gain in heat transfer in these areas is more significant than the reduction in cooling capacity in the sections with lower heat transfer coefficient values. Moreover, the mathematical model allows a conductive heat transfer between neighboring sections, which means that part of the heat that cannot be transferred due to a poor convective cooling is passed to another section with a higher cooling capacity.