Design on intermittent ventilation strategy for radon removal in underground space.

Ventilation to reduce radon was one of the most widely used, important, and effective means to reduce radon concentration in underground engineering. The largest energy consumption of underground buildings was the building ventilation system. Taking the radon migration process in a room as an example, this paper built a numerical model that accounted for the mechanism of radon production, exhalation, and diffusion process, by proposing a novel intermittent ventilation strategy to mitigate radon concentration in underground space. Three ventilation strategies (no ventilation, continuous ventilation, and intermittent ventilation) were compared under various wind speeds and fresh air ratios. Under the same safe duration of radon concentration, when intermittent ventilation was operated with the same wind speed, the startup time was reduced by 79.4%, 86.0%, 90.8%, 92.8%, 91.25%, with compared with continuous ventilation. The higher the fresh air ratio, the lower the radon concentration limit, and the faster the dynamic equilibrium state of radon concentration will be reached. During intermittent ventilation, reducing the fresh air ratio can greatly increase the recovery and utilization of the return air heat, thereby reducing the power of the air conditioning unit. Considering the comprehensive energy-saving benefits of the ventilation system, the appropriate intermittent ventilation plan should be made to meet radon reduction requirements in the range of low wind speed. If low wind speed was selected, there existed advantages of low ventilation noise and more comfortable, as well.