Decoupling Transient Effects Of Factors Affected By Air Recirculation Devices On Contaminant Distribution In Ventilated Spaces

The use of indoor air recirculation devices, such as air cleaners and air curtains, results in an airflow interaction between air supply jets and recirculated airflows. It is essential to quantify the independent effects of supply air, contaminant source, and initial condition in a ventilated room with air recirculation. In this paper, the transport process of a contaminant with air recirculation is mathematically derived based on a fixed flow field. A linear expression is established to describe the transient contributions of different influencing factors. The indices of revised transient accessibility of supply air (RTASA), contaminant source (RTACS), and initial condition (RTAIC), are defined to quantify the effect of each factor by incorporating the effect of air recirculation. The prediction accuracy is verified through a comparison with simulation results. The proposed indices are applied to evaluate a ventilated room with an air cleaner and recirculated air curtain. The results indicate that the recirculated airflows from both the air cleaner and air curtain increase the RTASA of each air supply inlet to distant areas. The purification effect (30%) occurs only after a certain period for RTASA and RTACS, while it operates from the initial stage for RTAIC owing to the initial high contamination. The RTACS in the protected zone is reduced significantly owing to the air curtain, with a decrease from 1.33 to 0.77 at 600 s at a height of 1.2 m in the curtain jet. The proposed method can be used to evaluate indoor environments with various air recirculation devices.