Study On The Effects Of Air Supply Methods On Indoor Air Pollutants Removal In Non-residential Buildings

With the rapid development of China’s economy and industrialization,office buildings,industrial buildings and other non-residential buildings are landing on a large scale.Indoor environmental problems caused by the special characteristics of non-residential buildings have become the focus of people’s attention.For example,office buildings have high CO₂concentration due to high density of people,and industrial buildings have high concentration of particulate matter in the production process,which affects people’s physical and mental health and work efficiency.To address the issue of indoor environmental pollution,the main way taken is mechanical ventilation.However,the current mechanical ventilation system is generally poor efficiency and high energy consumption.How to improve the efficiency of mechanical ventilation is of great significance to improve indoor air quality（IAQ）and building energy saving.The aim of this paper is to investigate one of the main influencing factors（ventilation modes）of indoor ventilation design in non-residential buildings,to create a good airflow distribution,improve ventilation efficiency and reduce ventilation energy consumption.By means of experiments and numerical simulation,this paper takes office buildings and industrial buildings as research objects to study the effects of indoor airflow distribution on the diffusion and removal of pollutants under different ventilation modes.The effects of four aspect ratios and two different locations of inlet vent,and three kinds of ventilation rates on indoor CO₂diffusion and removal were studied for office buildings.A new ventilation design was proposed for industrial buildings,and then the effects of four supplied air velocities and three exhausted velocities on the indoor particulate matter diffusion and removal were studied.The main results of this study are as follows:（1）For the same area of the strip inlet vent,when the aspect ratio L/W is designed as 4,when the fresh air is provided into the room through the inlet vent,the airflow distribution is conducive to the removal of indoor CO₂,and the removal efficiency is at least 1.8 times higher than other aspect ratio（i.e.,L/W=2,6,8）.（2）When the inlet vent is located at the symmetrical position of the wall on the air supply side,the removal efficiency of CO₂by indoor airflow is higher than the condition of inlet vent at the asymmetric position.In this situation,changing the location of pollution source has little effect on the removal efficiency.（3）When the aspect ratio L/W of the inlet vent is large（e.g.,L/W=8）,the removal efficiency of indoor airflow on CO₂is low.With the air change rate per hour increases,the whole indoor CO₂concentration is relatively high.Under this circumstance,increasing the air change rate per hour is not conducive to CO₂removal,which not only wastes energy,but also fails to ensure IAQ.（4）For the integrated design of supplied air velocity and exhausted velocity,the average particle concentration C*in the indoor breathing zone can be reduced by 20%-40%by using reasonable exhausted velocity on top of the building compared with the condition of no exhaust velocity when the supply velocity keeps constant.（5）For the integrated design of supplied air velocity and exhausted velocity,the unreasonable design of supplied air velocity and exhausted velocity will lead to conflicting indoor airflow,which is not conducive to the removal of particulate matter.Welled design of supplied air velocity and exhausted velocity can save at least 58%energy with same ventilation efficiency.This study investigates the effects of aspect ratio and the location of inlet vent,coupled velocity of supplied and exhausted air velocity on indoor airflow distribution,selected indoor pollutants（CO₂and particulate matter）removal efficiency as evaluation index of airflow distribution,reveal their impact on the air distribution and indoor pollutants removal.These findings can provide theoretical basis and engineering reference for future ventilation design of non-residential buildings such as office buildings and industrial buildings in improving indoor air quality and reducing ventilation energy consumption.