Experimental Analysis Of The Effect Of Natural Ventilation On The CO₂ Concentration In Campus Classroom

As colleges and universities are incubators of new forces and knowledge of society, concern the interior environment of universities is not only a social care and respect of new forces, but also for the guarantee of social development to join health power. Many study show that the mainly problem of classroom air quality is the insufficient indoor air, affecting the efficiency of student's learning and health. Most of teaching time focus on the spring or autumn period, the classroom with no fresh air system, the main way to provide fresh air is to open the window. Therefore, the study of the characteristics of natural ventilation in the classroom by using CO2 concentration, so as to put forward feasible and effective measures to improve the indoor air quality.Based on the characteristics of the influencing factors of natural ventilation, this article choose three teaching buildings in different campus in Chongqing University as the research objects. Firstly, classroom space size, attendance rate, window size and the ratio of window to the floor and other information including the personal control behavior of the doors and windows are statistically analysed, determining the main factors and levels affecting the natural ventilation. Secondly, tested the wind speed at 1.5m distance of outdoor windows according to the height, orientation, layout characteristics of different location of the classroom of the teaching buildings, then define the range of speed of outside the window with different meteorological level. Thirdly, based on major factors and levels get from comprehensive survey, indoor CO2 are measured and single factor analysis under different levels of attendance rate, window size, window position, convection ventilation.To find multiple factors how influence indoor natural ventilation, at first, design Interactive orthogonal experiment on window strategy(open time, size and position) to typical classrooms, use range analysis and variance analysis and get the importance order of factors followed by time, size, location, and except location, the others are significant factor. Secondly, considering the complexity of the experimental and practical significance, design non-interactive orthogonal experiment with the main influencing factors: attendance rate, window area and meteorological conditions, and repeated tests on three typical classroom. The result show that the two Regular classrooms had attest the order of factors followed by window area, weather conditions, and attendance rate. However, the trapezoidal classroom shows the weather conditions is more important than window area. Finally, analyse the frequent conditions of the classroom, including the closed classroom with the use of air conditioning, statistical analysis of the range of CO2 concentration with random weather. Put forward measures include decrease attendance rate, enlarge opened window, convection ventilation by door or cross window, and to set up a new wind system is considered.