Calculation of Pollutant and Thermal Accumulation in Recirculating Ventilation Systems with Discrete High-Temperature Sources

The non-fixed location and intermittent emission of pollution sources are posing significant challenges for industrial ventilation and dust removal. Owing to its energy-saving and emission-reduction advantages, recirculating ventilation has emerged as a critical solution in industrial ventilation. However, the introduction of recirculated air leads to the accumulation of both pollutants and temperature in controlled environments. However, the accumulation situation and control methods within the recirculation air system are still not fully understood, especially for discrete pollution sources. Theoretical models were developed in this paper to quantitatively calculate these issues. Then, the spatiotemporal distributions of air temperature and pollutant concentrations were investigated within the controlled environment by numerical simulation. The result shows that upper limits exist for both pollutant and heat accumulation. Controlling the recirculation air ratio between 0% and 60% resulted in a corresponding increase in pollutant concentration ranging up to 28.58% and a temperature rise of up to 6.16%. At a 27.8% recirculation ratio, fresh air consumption decreased by 27.8%, mean pollutant concentration increased by 5.50%, and mean air temperature rose by 3.78%. In addition, the dynamic characteristics of pollutant concentration and temperature variation at different circulating air ratios were analyzed. The recirculating air system effectively conserves energy and reduces emissions. The quantitative calculation models can facilitate the adoption and promotion of such systems, thereby contributing to industrial green development.