Abstract
The performance of perforated inflatable ducts was investigated, and practical equations and coefficients were derived to permit the design of such ducts for ventilation of greenhouses and livestock buildings.
1) A mean static pressure in a perforated duct was needed as high as 1.0 to 2.5mm water gauge, at above which the duct stayed inflated.
2) The critical factor in the performance of perforated inflatable duct was the ratio of total exit hole area to duct cross-sectional area, termed “aperture ratio”. With the duct having larger value of this ratio, the static pressure and discharge air velocity near the closed end were greater than those near the fan.
3) The distribution of the static pressure and discharge air velocity along the duct were determined with only aperture ratio when the duct length, duct diameter, and air flow rate of fan were given. These distribution were not influenced with the size and number of exit hole.
4) Air discharged from holes near the fan had considerable tangenitial and downstream components of velocity, but discharge air at the closed end was normal to the duct These tendencies were pronounced with the duct having larger aperture ratio.
5) Equations were derived to predict air velocity and static pressure in duct and discharge air velocity from the exit holes (Eq. (8), (9), and (10)).
6) Some coefficients required in above equations were determined (Tabl 3 and 4).
7) Calculated values using those equations and coefficients agreed with measurement when the aperture ratio ranged from 0.6 to 1.8.
