AIRFLOW IN DUCT SYSTEM AT THE NON-OPERATIONAL CASE BY TEMPERATURE DIFFERENCES OF ROOMS : Contamination on the inside wall of air conditioning duct

Contamination on the inside wall of air-conditioning duct is one of the source of indoor air pollution. On this paper, airflow generation in the non-operational duct is reported as the reason of duct contamination by inflow of airborne particles to the duct. The driving force of airflow is caused by the temperature difference of rooms connected by the duct system. Followings were obtained by experimental result. 1) Airflow of more than 20cm/s was measured in the non-operational duct of an office building when there were temperature differences of 4- 5K between rooms. 2) Model chamber experiments show that the air velocity is proportional to the square root of the temperature difference and the height of chamber.