perancangan ducting
DESCRIPTION
Perancangan Instalasi Ducting Dalam GedungTRANSCRIPT
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EQUAL FRICTION METHOD EXAMPLEDuct system for general office ;
Total air quantity5400 cfm18 air terminals300 cfm eachOperating pressure for all terminals-0.15 in.wgRadius elbowsR/D = 1.25
Find ;Initial duct velocity, area, size and friction rate in the ductTotal equivalent length of duct run, with highest resistance Total static pressure required at Fan discharge
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DUCT LAYOUT
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SELECT AN INITIAL VELOCITYRECOMMENDED MAX DUCT VELOCITIES FOR LOW VELOCITY SYSTEMS
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Velocity dipilih 1700 fpm
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Duct area : 5400 cfm/1700 fpm = 3.18 sq.ft
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Duct size (TABLE 6)
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Duct size : 22 in x 22 in
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Circular equiv. diameter
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Initial friction rate
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Friction rate ; 0.145 in wg per 100 ft of eauivalent length
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Percent section area in branches
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Percent of cfm = air quantity in duct section/ total air quantity
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It appears that the duct run from the Fan to terminal 18 has the highest resistance
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Friction of rectangular Elbow
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The total friction loss in the ductwork frfom the Fan to terminal 18 :
Loss= total equiv length x friction rate
= 229 ft x (0.145/100 ft) = 0.332 in. wg
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Total pressure at Fan DischargeThe sum of the terminal operating pressure and the loss in the ductwork
0.332 in. wg + 0.15 in.wg = 0.482 in.wg
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Friction losses