Natural ventilation of underground shelters to improve indoor thermal and moisture environments in the various climates of China

Indoor moisture is a crucial aspect of the environment in naturally ventilated underground shelters that remain unattended for long periods of time. The objective of this study was to investigate the impact of natural ventilation on the indoor temperature and humidity of underground shelters using a multi-zone airflow simulation and thereby evaluate the ability of natural ventilation to maintain the indoor environment of shelters in various climates in China. Firstly, a multi-zone airflow model was coupled with the dynamic heat transfer in an underground shelter to simulate the natural ventilation rate and indoor environment. The accuracy of this coupled simulation was subsequently validated using the data measured at an actual shelter. Next, the verified simulation method was applied to analyse the seasonal fluctuations in the natural ventilation rate of underground shelters in the various climates in China; these results were applied to determine the corresponding annual variations in the indoor temperature and humidity. The analysed results show that the relationship between the ventilation rate and indoor humidity level is dependent on both season and climate, and that the influence of the ventilation rate can be negative during summer, especially in wet climate zone. Finally, these findings were evaluated to provide guidelines for regulating natural ventilation according to climate, informing the management of unattended shelters in China.