EFFECT OF AIR DEFLECTORS ON FAN PERFORMANCE IN TUNNEL-VENTILATED BROILER HOUSES WITH A DROPPED CEILING

摘要

Air velocity is a critical design parameter for modern commercial broiler houses, owing to the beneficial effects of increased cooling on live performance and thermal comfort in broiler chickens. As a result, design velocities have increased over the last 15 years and broiler growers have installed additional fan capacity or air deflectors in the ceiling peak to reduce building cross-sectional area. While deflectors have traditionally been recommended only for buildings with open ceilings, an increasing number of growers have installed deflectors in dropped ceiling houses to provide local increases in air velocity without additional fan capacity and improve air velocity uniformity across the house. However, adding additional restriction can increase static pressure and reduce fan performance. Fan flow rates were measured in three tunnel-ventilated commercial broiler houses equipped with air deflectors with the deflectors in the deployed (down) and retracted (up) positions. The broiler houses measured 15.2 x 144.8 m and were equipped with 12 tunnel exhaust fans (137.2 cm diameter) and nine air deflectors at 12.2 m intervals, beginning after the tunnel inlet area and ending 15.2 m before the fans. Flow rate and static pressure data were collected concurrently for each fan for each deflector position with all fans operating to simulate tunnel ventilation during warm weather. Data were analyzed using ANOVA and least square means were separated using Fisher's LSD. The results show that deploying air deflectors significantly reduced mean fan flow rate by 11% (p < 0.0001) and increased static pressure by 11.2 Pa (p < 0.0001). The results of the current study suggest that adding air deflectors is likely not appropriate in existing broiler houses with dropped ceilings when fan performance and energy use are taken into consideration