Abstract
Natural ventilation can be categorized into single-sided ventilation and cross-ventilation. Based on the air flow mechanism of a single-sided wind-driven natural ventilation, the effective ventilation flow rates in buildings are different from the air flow rates through openings. The mixing coefficient or ventilation efficiency is defined by the ratio of these flow rates, indicating the effective ventilating ability of a single-sided ventilation, similar to the effect of penetration depth of fresh air. This paper provides a detailed analysis of ventilation effectiveness in a building with a single opening based on numerical simulations. The simulation was validated by a study of an existing case. By numerical calculation, the air flow rates through openings and the effective ventilation flow rates in buildings were compared. Effects of various influencing parameters, such as wind speed, opening location, opening area and aspect ratio of windward wall on ventilation efficiency were evaluated. An estimated mixing coefficient has been established by the modelling, which would be beneficial for the predication of the short-circuit ratio of ventilation rate through openings.
Highlights
Due to the demand for the lowering energy consumption and reducing greenhouse gas emissions, there have been increasing attention by the building industry and research academics on passive technology of natural ventilation for buildings (Yik and Lun, 2015; Abdullah and Alibaba, 2020), when the outdoor ambient air is suitable
Effects of various influencing parameters, such as wind speed, opening location, opening area and aspect ratio of windward wall on effective ventilation flow rate, mixing coefficient and penetration depth of fresh air were investigated by numerical simulation
The ventilation efficiency or mixing coefficient was discussed by a series of numerical simulation
Summary
Due to the demand for the lowering energy consumption and reducing greenhouse gas emissions, there have been increasing attention by the building industry and research academics on passive technology of natural ventilation for buildings (Yik and Lun, 2015; Abdullah and Alibaba, 2020), when the outdoor ambient air is suitable. Da Graça (2018) pointed out that the wind driven SS1 flows in small one zone buildings may be caused by static pressure change across the opening area, and he presented a calculation model considering turbulent mixing in SS1 flows The ratio between the effective air flow rate and the bulk airflow rate across openings is defined as the mixing coefficient or ventilation efficiency (Cockroft and Robertson, 1976; Bu and Kato, 2016), which is the core research objective of this study
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