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# Perancangan Ducting

Date post: 16-Nov-2015
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Author: arga-benny
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Perancangan Instalasi Ducting Dalam Gedung
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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

• DUCT LAYOUT

• SELECT AN INITIAL VELOCITYRECOMMENDED MAX DUCT VELOCITIES FOR LOW VELOCITY SYSTEMS

• Velocity dipilih 1700 fpm

• Duct area : 5400 cfm/1700 fpm = 3.18 sq.ft

• Duct size (TABLE 6)

• Duct size : 22 in x 22 in

• Circular equiv. diameter

• Initial friction rate

• Friction rate ; 0.145 in wg per 100 ft of eauivalent length

• Percent section area in branches

• Percent of cfm = air quantity in duct section/ total air quantity

• It appears that the duct run from the Fan to terminal 18 has the highest resistance

• Friction of rectangular Elbow

• 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

• 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

• Friction losses

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