The industrial release of submicron aerosol particles at workplace could cause undue health effect on workers. To effectively capture and remove airborne particles, we need to study the characteristics of various interactive particle motion forces (drag force, Brownian force, Saffman lift force, etc.) and the dispersion of these aerosol particles in indoor air. In this study, the dominant force of submicron particles was determined by calculating the acting forces with different particle sizes. Then, a Discrete Particle Model (DPM) was used to calculate the trajectory of particle movement in turbulent thermal plume flow. Horizontal dispersity ( DH) was defined to evaluate the horizontal diffusion of the particulate matter. The impact of different particle diameters, heat source temperatures and initial relative velocities on DH was investigated. This study showed that the main acting forces for submicron aerosol particles were drag force, Brownian force, Saffman lift force and thermophoresis force. Brownian force cannot be ignored when the particle diameter was below 0.3 µm, which would promote the irregular movement of particles in space and enhance their diffusion ability. The smaller the particle size, the higher the heat source temperature and the lower the particles' initial velocity would lead to the increase of DH.

The heat radiation in a residential kitchen was simulated by CFD (Computational-fluid-dynamics) to evaluate the cooling by a radiant cooling ceiling panel and pollution dispersion by the range hood and the air extraction system. The kitchen has a 2-hobs stove and a fume hood for removing waste heat and fumes. The simulation was validated by measurements in a domestic kitchen in a home in Changsha, China, where summer temperature is generally about 33 °C and often over 35–42°C. The simulation results show that the pollutant concentration in the kitchen during cooking was much lower than the Chinese standard criteria of GB/T18883-2002. A standard turbulence model was used, which indicated satisfactory distribution of temperature and airflow in the kitchen. The indoor airflow velocity was low. The airflow temperature when both hobs were used was slightly higher by 3–4°C than when a single hob was used. The temperature in the kitchen during cooking was about 28 °C, which was a degree lower than the living-room temperature, thus maintaining a comfortable thermal and healthy environment. The radiant cooling in the ceiling was shown to be a significant contributing factor. The ring suction type range hood has a sufficient capacity to remove the kitchen fume contaminants.

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This study evaluated the effect of ventilation rate and air supply angle of an air purifier using computational fluid dynamics to determine the dispersion of airborne COVID virus exhaled by an infected person. The risk of infection for an occupant was determined based on the virus concentration in the active area and accumulated particle dose within the breathing zone by varying the ventilation parameters. The air purifier was found to provide a local dilution and would block the development of an expiratory jet for a short time to reduce transmission risk. Compared to the case without an air purifier, the maximum reductions were 94.27% in the accumulated dose and 53.2% in the particle count concentration. In the breathing area, the larger air supply angle (90° > 60° > 30°) is better when the ventilation rate was 27.0 m3/h and 40.5 m3/h. Otherwise, 60° air supply angle is preferable where the ventilation rate was 54.0 m3/h. Assessing the results with the grey relational analysis revealed that the relational degree for particle count concentration was greater by varying the ventilation rate than by varying the air supply angle. However, the relational degree according to the accumulated dose was greater by varying the air supply angle than by increasing the ventilation rate. These findings may provide an important control strategy to effectively mitigate the risk of infection in a confined room by using an air purifier.