Document Type : Full Lenght Research Article
Faculty of Mechanical Engineering, Semnan University, Semnan
Over time, many studies have proven the advantages of using chilled ceiling (CC) systems as an assistant device for covering the barriers of the stratified air distribution (STRAD) systems. However, previous investigations are still insufficient, particularly in analyzing indoor air quality (IAQ). With the aid of the computational fluid dynamics (CFD) techniques and AIRPACK software, we attempted to determine the possible effects of the chilled ceiling in the performance of displacement ventilation (DV) on contaminant removal, ventilation effectiveness, the freshness of air, and air change efficiency (ACE). In addition, we tried to find a solution to maintain the stratified form of the contaminant profile and reduce the impact of the negative buoyant flow (inversion phenomenon) caused by the chilled surface. In order to investigate, the study was analyzed with variable exhaust vent location. The relults indicated that air change efficiency index (ACE) in case 1 (local exhaust) is 0.64 for displacement ventilation (DV) and it has best operation among other cases, whereas ventilation effectiveness index in case 2 (exhaust vent near top of wall) for DV was 1.46 and it was best scenario among others. According to the results, when the exhaust vent was placed near the contaminant sources, the inversion phenomenon caused by chilled surface minimized and the contaminant concentration was safer at the inhaled zone than in the other cases. In addition, the chilled ceiling had entirely adverse effects on the mean age of air at the inhaled zone and ACE index regardless of the exhaust vent location. Nevertheless, the disturbance effect was lower when the exhaust vent placed local compared to the other cases.