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Although there have been studies on gravitational settling of non-spherical particles, only few studies have incorporated the diffusion of non-spherical particles into particle deposition. Non-spherical particles occupy a large proportion of particles in indoor environments, and their deposition is a key factor that influences the level of indoor particulate matter pollution. In this study, we modified drag coefficient and diffusion coefficient based on settling experiment and Langevin equation to fulfill a semi-analytical modeling of particle deposition on indoor surfaces. The modified diffusion coefficient and deposition velocity agree well with the experimental results for fibers. With the modified diffusion coefficient, we further modeled the deposition of non-spherical particles on indoor surfaces under typical air friction velocity conditions. The results showed that the deposition velocity between spherical and non-spherical particle deviated by 10–25% with the same aerodynamic diameter for diffusion-controlled region, while the application of aerodynamic diameter would lead to 10% to over 100% deviation with 10 μm particle for particle depositing on side walls. However, the deposition of non-spherical particle can be estimated rightly through spherical particle with the same aerodynamic diameter when gravitational settling dominates the deposition process. The modification of the diffusion coefficient and deposition velocity of non-spherical particles is expected to help in understanding the effect of particle shape on its deposition and may be further applied to indoor particle pollution modeling. Copyright © 2022 American Association for Aerosol Research

The discharge capacity of the range hood for cooking-related pollution under current exhaust airflow rate (EAR) standard of 300–500 m 3 /h is limited when cooking temperature near the smoke point of edible oil. This study endeavored to determine appropriate EAR for cooking temperature varies from 200 to 300 °C, which comprised smoke points of different edible oils, considering whether the kitchen was ventilated with the adjacent room or not, and the cooking position of the left/right stove. Particles generated from a simplified cooking process of oil heating test, tracer gas experiment, and flow visualization experiment were conducted. CFD simulation with capture efficiency as an evaluation index was performed. Evidence is presented that when the cooking temperature is 200 °C, the pollutant control effect does not change much when the EAR is above 700 m 3/h, while an EAR of 800 m3 /h may be necessary at 300 °C. For open-door and closed-door cooking, a minimal difference exists in demand for a suitable EAR in this local ventilation system . However, the hood continues to exhaust air during post-cooking period, thereby showing that a higher EAR is necessary to control the pollutants in open-door cooking. The primary and secondary cross draft airflows caused by different air supply positions are observed, which play a vital role in selecting suitable left/right cooking position. The location of the left stove is conducive to the elimination of cooking-related pollutants due to primary cross draft, while it is the right stove due to secondary cross draft.

This paper presents the effect of a personalized air curtain on respiratory protection. Influencing factors (opening angle, tilt angle, velocity, and width) and the impact from real respiratory process were considered by conducting experiments and computational fluid dynamics (CFD) simulations. Results showed that the entrainment and diffusion of contaminants occurred around the air curtain with varying parameters. Opening angle of 180° and tilt angle of 0° are recommended due to good protection factor (PF). Without interference, width of 30 mm and low velocity (0.8–0.9 m/s) were most beneficial for PF because of the good protection against contaminants both inside between the air curtain and the face and outside of the curtain. With respiratory interference, PF decreased under the same air curtain parameters due to the disruption of the air curtain jet by inhalation, and the interference became increasingly weak at velocities above 1.5 m/s. PF reached 220 when the parameters were width of 30 mm, velocity of 1.5 m/s under respiratory interference. This study reveals the potential of using personalized air curtains for personal respiratory protection in industrial air-contaminated environments.

This study proposed a novel integrated design combing an air cleaner with the conventional exhaust hood for the improvement of indoor air quality in the residential kitchen. Airflow interaction between the exhaust confluence of the range hood and the strong momentum induced by air cleaner was investigated for this kind of compact configuration. The potential of energy saving by using the air cleaner was discussed. Firstly, numerical simulation was employed to obtain well-organized recirculation purification parameters under different air outlet widths and angles and experiments were conducted to verify the control effect of pollutant concentration in the kitchen space with the good design. Results show that the oblique upward air supply of the air cleaner was found significantly better to clean the kitchen space than horizontal and oblique downward supply. The relative purification effect of the integrated air cleaner is less affected by the exhaust flowrate of the hood. The PM 2.5 concentration reduction rate by the air cleaner at the breathing zone is near 60%, while the TVOC concentration reduction approximately 30%. Secondly, concentration decay rate at post-cooking period with/without the integrated air cleaner was measured and compared. It was found that the concentration decay rate achieved by the integrated air cleaner with 100 m3/h and oblique upward air supply is close to the decay rate of exhaust hood with 200 m3/h. It means that the integrated design proposed in this study is effective in reducing human exposure to cooking-related pollutants and has a significant energy-saving potential.

The function of air curtain range hood in improving human exposure was investigated by conducting experiment and CFD simulation. The intake fraction was estimated to reflect the effect of the air curtain. Factors affecting human exposure, including the exhaust rate, heat source intensity, air supply angle, air supply velocity, and slot width of the air curtain, were incorporated according to an orthogonal design. To comprehend the roles that the air curtain performed, the characteristics of flow and concentration field were captured through visualization experiment and CFD method. Furthermore, the effect of using an air curtain to resist the impact of human walking on human exposure was examined. The exhaust rate, heat source intensity, and air supply angle were significant factors that affect human exposure with a significance level of 0.01. Compared with the traditional range counterpart, air curtain range hood could decrease the intake fraction by factor of 1.5–5. Air curtain could reduce turbulent intensity around the range hood and improve local airflow organization. Meanwhile, air curtain would considerably protect walking humans from exposure to pollutants. The outcome of this study could help us understand the effect of air curtain range hood with a comprehensive perspective.