The Influence Of The Temperature Difference Between Indoor And Outdoor On The Natural Ventilation And The Diffusion Of Pollutants In The Surrounding Buildings Of The Street Canyon

As an energy-saving and efficient means to improve the indoor environment,natural ventilation is increasingly used in public buildings where modern buildings and populations gather.The article comprehensively summarizes the importance of natural ventilation,summarizes the current research methods of natural ventilation,the status quo of natural ventilation research at home and abroad,and introduces the main content of the research,introduces the basic theory of natural ventilation and numerical simulation theory.This paper uses Airpak3.0.16 modeling software to construct a Two-dimensional single-sided and cross-sided natural ventilation physical model,combined with Fluent software to study the effects of different outdoor wind speeds and indoor-outdoor temperature differences on the ventilation of rooms on both sides of the street canyon and the diffusion of indoor and outdoor pollutants.Influenced by the wind from the city,the airflow forms a large-scale clockwise vortex in the street canyon.As the wind speed increases,the vortex structure and intensity gradually increase to cover the entire street canyon.Leeward side eontaminant eoneentrations are higher than the windward side.When there is a temperature difference between indoor and outdoor,thermal buoyancy and wind pressure can change the indoor vortex intensity and direction,which affects the indoor ventilation efiiciency and pollutant concentration,but has little effect on the airflow and pollutant diffusion in the street canyon.When the building room is single-sided natural ventilation,the main vortex and the secondary vortex in the street valley have a great influence on the airflow in the room.The source of pollution is on the street,when the outdoor wind speed is low,the indoor-outdoor telperature difference makes the difference in ventilation efficiency between the windward and leeward sides of the street valley increase,and the difference in the personal pollutant intake fraction of the residents decreases.At high wind speeds,the indoor-outdoor temperature difference makes the difference in ventilation efficiency between the windward and leeward sides of the street valley decrease,and the difterence in the personal pollutant intake fraction of the residents decreases.When the outdoor wind speed increases,the indoor air flow is obviously increased by the action of wind pressure,the ventilation efficiency of each floor room is increased,and the indoor pollutant concentration is significantly reduced.Affected by street circulation,when the pollution source is located on the windward side of the street canyon,the room below the pollution source is greatly affected.When the pollution source is located on the leeward side of the street canyon,the room above the pollution source is greatly affected.When the building room is cross ventilation,the high-rise room and the low-rise room are easy to form an indoor "cross ventilation" under the action of the outdoor airflow,and the indoor airflow in the middle of the building is weak.The source of pollution is on the street,when the outdoor wind speed is low,the indoor-outdoor temperature difference makes the difference in ventilation efficiency between the windward and leeward sides of the street valley decrease,and the difference in the personal pollutant intake fraction of the residents decreases.At high wind speeds,the indoor-outdoor temperature difference makes the difference in ventilation efficiency between the windward and leeward sides of the street valley decrease,and the difference in the personal pollutant intake fraction of the residents increases.Affected by street circulation,when the pollution source is located in different rooms of the street canyon,its diffusion form is similar to that of single-sided natural ventilation.However,due to the natural characteristics of both sides of the natural vention,the phenomenon of interlayer transmission occurs when the pollutants diffiise.The indoor-outdoor temperature difference affects the distribution and concentration of pollutants by changing the state of the airflow.