Impact Of The Air Movement On Thermal Comfort During Summer In Classrooms

The human society has been committed to create healthy and comfortable living environment. Air conditioning systems have been widely used in the new production, office and residential building. However, humans have paid too much attention to the controlling of indoor air temperature and humidity, ignoring other factors that play positive role for thermal comfort. For example, the widely use of air conditioning degenerates the idea of the using of air velocity. The energy crisis and global warming problem arises the new attention to the positive role of air movement in summer. Chongqing locates in the hot summer and cold winter climate region and classrooms are important places for the college students to study in. It is an important measure to use the mechanical ventilation to improve the thermal comfort. And this paper is about the research work in classroom.Firstly, the paper reviewes the present study of ventilation both at home and abroad, and then determines the scheme and methods, both fieldy study and laboraty study will be conducted in this paper.During the summer, a large-scale survey in Chongqing University was conducted. We found the thermal environments with high air temperature, high humidity and high air velocity. The classroom doors, windows and fans were always open, the indoor air velocity have a significant relationship with air temperature. When the air temperature was below 28℃, the indoor air velocity of the researchers chose to focus on 0.2 m/s or so, and when the air temperature was higher than 28℃, the air velocity increases.It was found that students had the strong feeling of discomfort in the summer., Tthe acceptable air temperature was got throuth three different methods, and the upper limit was set to 30℃. The PMV model couldn't predict the thermal sensation well in the hot or high velocity thermal environment, and the paper analyzed the reason from three factors.Air movement sensation had strong negative correlation with the thermal sensation. The prefferd air movement was analyzed throuth the air temperature, air velocity and overall thermal sensation. It was found that students had high requirements on air velocity. The air movement acceptability was high in the summer.Based on the field study, a laborary study was conducted, which verified the results of fiely study and confirmed that air velocity can make the cooling effet of air temperature. Then a new method of determing the optimum velocity was put forward that should not only satisfy the thermal comfort but also meet the acceptability of air movement. In the end, a control strategy of air movement was put forward-when the air temperature was below 28℃, the air velocity could be kept at a minimum level that natural ventilation would meet the requirements of human thermal comfort; when the air temperature was between 28℃and 30℃, the appropriate mechanical ventilation can be used to increase the air velocity; and when the air temperature was higher than 30℃,the strategy of air conditioning or the mixed used of air conditonning and mechanical ventilationg should be used.