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Particles emitted from the kitchen have been proven as one of the major indoor particulate pollutants which could pose serious risk on human health. Thus, it is critical to study the migration of kitchen particles and the impact of kitchen particles on non-kitchen zones. Since Chinese domestic kitchens are equipped with exhaust hoods, the capture efficiency of an exhaust hood in real residence was first measured. The capture efficiency was about 48% with the air flow rate of 0.125 m3/s. Second, the relative occupant exposure was calculated to quantify migration characteristics of kitchen particles under different ventilation models. Results show that the meteorological environment had little effect on migration by infiltration but significant by natural ventilation. In the dwelling layout of this study, relative occupant exposures showed an upward trend in windward and a downward trend in leeward. When the wind direction was 225°, wind speed had the greatest impact on particle migration. Finally, the effect of the opening and closing situation of kitchen door on air quality was analysed. Results show that closing the kitchen door increased the exposure in the kitchen by 30–58%, while the exposure in the study dropped to 43% of the door open status. [ABSTRACT FROM AUTHOR]

• Interpolating hour-by-hour wind velocity from a meteorological station into minute-by-minute velocity. • CFD simulations of the outdoor wind velocity around an apartment building and the indoor cross-ventilation rate in an apartment. • Verification of the computed results with corresponding experimental data. Natural ventilation in buildings can improve indoor air quality and thermal comfort and reduce air-conditioning use except for highly polluted area. Traditionally, the inflow boundary conditions for calculating natural ventilation used weather data from a meteorological station that is often in a suburb. The use of hour-by-hour wind velocity from the station may give rise to some errors because of the large time step. This investigation proposed a correlation method for converting the hour-by-hour wind velocity from a meteorological station to minute-by-minute velocity, using data measured on the rooftop of the building of interest. A CFD simulation with the coupled modeling method using the unsteady RNG k-ɛ model was performed to calculate airflow around the building and airflow in an apartment simultaneously. The computed outdoor wind velocity and indoor ventilation rate were compared with the corresponding experimental data. The results showed that the simulations calculated the outdoor wind velocity on the building rooftop and the cross-ventilation rate through the apartment with acceptable accuracy. [ABSTRACT FROM AUTHOR]

Cross ventilation can effectively improve air quality with larger ventilation rate than single-sided natural ventilation. The measurement of ventilation rate is critical for research on indoor environmental maintenance and air quality control. This investigation compared four methods of obtaining the cross ventilation rate in a residence, including direct measurement by the tracer-gas-decay method, and indirect measurement with ultrasonic anemometers, from the wind speed at a reference position, and from the differential pressure between two sides of the residence. Furthermore, measured wind speed in the direction normal to the opening was used to analyze the unsteady and non-unidirectional flow characteristics, and the airflow consistency σ was found to be in the range of 50%–98%. The results show that when σ > 90%, the internal airflow was close to unidirectional flow, and the ventilation rates in all rooms were similar. As the ratio σ decreased, the error between the measured and calculated ventilation rate at the openings increased. When σ < 70% with severe non-unidirectional flow, the presumed ventilation volume based on the measured wind speed at one opening had a large deviation from the measured ventilation rate at the other. We then calculated the volume of air intake and outflow at the same opening. On the basis of volume conservation, the exchange ventilation rates between internal rooms were obtained by the tracer-gas-decay method combined with ultrasonic anemometers to measure the wind speed at the openings of the multi-zone dwellings. Therefore, single tracer-gas-decay method with ultrasonic anemometer at the openings can measure the cross ventilation rate and obtained the ventilation rate between internal rooms of the multi-zone residence. • Four methods were used to measure the cross-ventilation rate in urban multi-zone dwellings. • Airflow consistency ratio of cross ventilation in the direction normal to the opening was statistically 50%–98%. • The exchange ventilation rate between rooms was calculated by tracer-gas-decay method with anemometers at the openings. [ABSTRACT FROM AUTHOR]