Numerical study on the effect of buoyancy-driven pollution source on vortex ventilation performance

High-temperature buoyancy-driven pollutants that generally exist in industrial buildings and kitchens often be eliminated by local exhaust ventilation systems. The high-temperature pollutant plume driven by buoyancy significantly affects the local exhaust process, resulting in the change in the exhaust flow field and reduction of the pollutant capture efficiency. In this study, the effects of thermal buoyancy-driven pollution sources on the vortex flow field and pollutant removal efficiency of a vortex ventilation system are evaluated through experiments and numerical simulations. The results show that with an increase in the buoyancy flux of the pollution source, the minimum negative pressure and maximum tangential velocity in the vortex flow first increase and then decrease, that is, the buoyancy plume first enhances and then weakens the vortex flow. A critical buoyancy flux exists, and the value of the critical buoyancy flux increases with an increase in the vortex ventilation intensity. Furthermore, the capture of high-temperature pollutants by vortex flow can be categorized as “plume-dominated” and “vortex-dominated”. These two types exhibit significant differences in pollutant transport paths and pollutant capture times during pollutant removal. In addition, on the basis of the pollutant capture efficiency, the vortex airflow performance with respect to capturing high-temperature buoyancy-driven pollutants can be classified as low-efficiency, transition, high-efficiency, and invalid zones. In the process of capturing high-temperature pollutants, vortex ventilation systems should be avoided in the low-efficiency and invalid zones.