Abstract
When a utilities underground conduit is ventilated and a Partition Type Damper (PTD) is installed to provide a conduit with an air volume damper, pressure losses occur as reported in Part 1 of this paper. Outlined are the experimental results regarding pressure loss when a pair of PTDs is installed at specified intervals inside a circular duct. Under the condition that the ratio of the length of partition (Y_b) to the diameter (D) in the center of the air duct (C_r=2Y_b/D) is 0.245, when the length of the interval (SP) is more than twenty times the duct diameter, the pressure loss becomes twice as large as that of one PTD. However, when the length of interval is less than this value, the amount of pressure loss changes according to the length of interval. The authors see this cause is considered to be attributable to the location between the two PTDs which interferes with the downward airflow from the head PTD. Therefore, Providing coefficient of interference (ψ_<dx>) caused by the length of interval, the pressure loss in this case is expressed in terms of the following equation; (dP_d)_<dx>=0.202ψ_<dx>・P_v ψ_<dx>=2{C_0+X(C_1+C_2・X)} X=(SP/D-a)/b where, (dP_d)_<dx>: pressure loss when a pair of PTDs with C_r=0.245 is installed at a specified interval inside circular duct [Pa] P_v: kinematic pressure in air duct [Pa] D: diameter of circular duct [m] SP/D: nondimension length of interval a, b, C_0, C_1, C_2: constant value caused by SP/D (Refer to Table 1) Table 1 Values of application at C_r=0.245 [table]
