Air Quality Monitoring And Application Of Fresh Air System In A Middle School Classroom In Shenyang

The classroom is the main place for students to stay in school.The air quality in the classroom is very important for students’study and health.In recent years,the number of middle school students in Shenyang has increased year by year,resulting in excessive student density in the classroom and worrying air environment in the classroom.Shenyang is located in the severe cold area.The outdoor low temperature weather and haze weather in winter are the factors restricting the natural ventilation of the classroom.In addition,in recent years,fresh air products with heat exchange have been applied in some buildings in severe cold areas,which makes it possible to improve the ventilation conditions in Shenyang middle school classrooms.At present,there are few studies on the air quality in Shenyang middle school classrooms and the application of different fresh air systems.Based on this situation,the author investigated the current situation and influencing factors of air quality in middle school classrooms in Shenyang through the subjective questionnaire survey of middle school students in Shenyang and the method of measuring the concentration of air pollutants in a middle school classroom.Airpak software is used to simulate and analyze the air distribution of different fresh air systems in the classroom,so as to provide reference for the future application of fresh air products in the classroom.First of all,a subjective questionnaire survey was conducted among students in different junior and senior high schools in Shenyang.According to the survey,middle school students are less satisfied with the air quality in the classroom.High school classrooms have more serious air quality problems than junior high school classrooms.Students often close doors and windows because of outdoor polluted air and noise,resulting in poor ventilation in the classroom.More than 80%of the surveyed students hope that the classroom can adopt the fresh air system.Then,through the comparative analysis of the fresh air volume,heat exchange efficiency and filtration efficiency of different fresh air products,it is found that the central fresh air system and the cabinet type fresh air fan have good applicability in the classroom.Secondly,a classroom with high student density in Shenyang was selected to test the CO₂concentration and PM2.5 concentration inside and outside the classroom.The test results show that when the doors and windows of the classroom are closed,the CO₂ concentration in the classroom exceeds the standard seriously;The correlation analysis of PM2.5 concentration inside and outside the classroom shows that when the outdoor haze pollution is serious,the PM2.5 concentration in the classroom exceeds 35g/m³.The number of school days accounted for 24%of school days.Finally,Airpak software is used to simulate the indoor air distribution when different central fresh air systems and cabinet fresh air fans are applied in the classroom when the doors and windows of the classroom are closed.The simulation results show that the air supply and return outlets in the central fresh air system are arranged parallel to the long side of the classroom,and the air supply direction is perpendicular to the classroom ground;In the cabinet type fresh air fan,4 air supply holes are parallel to the ground for air supply.Then,the minimum fresh air volume per capita that controls the CO₂ concentration in the classroom just below1000ppm is simulated and studied,and the central fresh air system is 20m³/（h·p）,The minimum per capita fresh air volume of cabinet type fresh air fan is 23m³/（h·p）.From the applicability study of fresh air system under different design temperatures in the classroom,it is concluded that the central fresh air system has a greater impact on the temperature in the classroom than the cabinet type fresh air fan,and the recommended indoor temperature for the classroom with the central fresh air system is 20℃or above.