## 5 Conclusions  
This study analyzed the low-vacuum heat dissipation process of a levitation electromagnet module in a maglev train. An experimentally verified numerical model has been established. A complete levitation electromagnet module, which contains 12 individual units, is used for thermal profile characterization. The numerical study on static heating of the levitation electromagnet is carried out under vacuum levels ranging from 0.1 atm to 1.0 atm. The flow field, temperature field of the fluid \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Vacuum Level (atm)** & **0.1** & **0.3** & **0.4** & **0.5** & **1** \\ \hline \(h_{e}\) (W/(m\({}^{2}\cdot\)K)) & 0.44 & 1.37 & 1.80 & 2.27 & 4.11 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Effective convection heat transfer coefficient of the EMU under different vacuum levels. Figure 11: Influence of vacuum level on effective convection heat transfer coefficient (\(h_{e}\)) of EMUs. domain, the temperature distribution profile on the levitation electromagnet surface and heat transfer parameters during the heating process are characterized and analyzed. Throughout this study, the high-temperature region in the levitation electromagnet module surface has been identified. During the heating process, the high-temperature area is located around four upper corners of each electromagnet unit in the levitation electromagnet module. With the reduction of environmental pressure, the temperature rise rate at the solid-fluid interface is significantly increased. Compared to 1.0 atm, the 100 K temperature rise process under 0.1 atm is shortened by 15.5 min, which indicates a 23% decrease in heating time. Meanwhile, it is found that at 1.0 atm, the radiation heat flux and convection heat flux from the heated levitation electromagnets are approximately equal. With the decrease of environmental pressure, the radiation heat transfer gradually becomes the dominant cooling heat flux. Under 0.1 atm, the radiation heat transfer takes more than 80% of the total heat flux. Meanwhile, this study derived the effective convection heat transfer coefficient under low-vacuum conditions. It is found that under the vacuum levels used in this study, the effective convection heat transfer coefficient varies between 0.4 W/(m\({}^{2}\)-K) and 4.1 W/(m\({}^{2}\)-K). A regression analysis is conducted between the effective convection heat transfer coefficient and vacuum level. As a result, a linear relationship between these two factors is established. This study has pioneered the research on a maglev train cooling system capacity under low-vacuum conditions. The outcome of this research could serve as an important reference for the design of maglev trains in a VTT system. The temperature and heat transfer coefficient profile of the levitation electromagnet can help with the understanding on the influence of vacuum level on a maglev cooling system. Moreover, the high-temperature area on the levitation electromagnet module surface can guide the design and optimization of the maglev cooling system. The experimentally verified numerical method established in this study can serve as an efficient tool for analyzing the heat transfer of maglev trains under low-vacuum conditions. [PERSON] has executed the study, collected and analyzed data, wrote and revised the paper; [PERSON] and [PERSON] have provided guidance on numerical simulation; [PERSON] has acquired the funding, review and validated the methodology, [PERSON] has conceived, designed, and executed the study project, wrote, reviewed and finalized the manuscript; All authors have read and agreed to the published version of the manuscript. This research was supported by the National Key R&D Program of China (Grant number: 2016 YFB1200602-11), the Strategic Consultation Program from Chinese Academy of Engineering (Grant number: 2018-ZD-16), and the Graduate Student Independent Innovation Project of Central South University (Grant Number: 20192 zts548).