Question

1) Figure 1 shows a typical duct layout. Design the duct system using equal friction method. Take the velocity of air in the main duct (A) as 8 m/s. Estimate the static pressure in the index run of the duct network. There is a pressure drop of 20 Pa each at the outlet grilles. Assume the resistance of the fittings at 10 Pa for elbow and 15 Pa for Tee. (10 marks) E 2 m Fan 2m 6 m 4 m F D 4 ms G 2 m/s с Figure 1

Answer 1

+ 3 m/s A m B 6m Fan D m 2m C 4m . 1m/s. For Section AB * volume flow rate (Qi) 4 + 3+1 = 8 m/s. velocity in moun durt 8 mls. (v)A > 8 Diantes 4A DAE 4XL T DA - 1.128m rate. AP 1.852 0.00 2268 Qv L D 4.973 0.002267 4.473 (1-128) 4. * velocity pressure. (8).852 H2olm 0.05 86 mm = 8 Puna )-( 4.04 4.04 s 3.921 mm Heo CS Scanned with CamScanner

Foo seckon BD Since we or using an using eaver friction method farction rate remans same for all Sechon ДР. 0.00 0.367 (Birhen 0.0586 mmasom 4.447 Dos from figuer (ar) ao = 3+1 = 4 mils. 4.913 0.002268 [4]'.857 D 0.0586 Dros 0.8714 m Aoo 71 0² 714* 0.8714 0.5963 m2 Coo- a 4 05463 6.907 ms velocity pocasus PVAD 16.701 2.256 mm 120 . (5.00) o ? 4.04 CS Scanned with CamScanner

for section of 1.352 APA 0.0022,63(Qw)" 0.0 586 mm Holm D4.93 (Qu)orga imo/s. 0.5200m A. 1/40R: 44 (0.52) 0.2123 me velocity (Cores) - 9 0.212 3 4.708 mis. 51.3580 mm H₂O velocity pocsuse (Posy ( ) ( 4.703 4.04 For section (BC) (Quec = 4 m/s 0.002267 Quyl-452 APE L = 0.0586 4.943 D: 0.9714 m QUAE Ara (A) = 71460%) = 0.5963 m² 4 6.tot mis velocity (C): 0.5463 velocity pocasux ) 6.707 12 4.04 = 2.756 mm H2O CS Scanned with CamScanner

Seekon DE 3 mls. 1.853 Qv= - 0.00 2.267 0.05 86 = 0.913. 03 0.782.8 m Asca= A= 914601): 0.48)3 m2 velocity (C)- 3 0.4313 6.233 MIS Velouty pressur 6.237 Poe: (4.00) 2.380 H20. 4.04 AB BD DES BC DE Section (m/s) 8 4 1 3 Lim) 4 २ 1.128 0723 0.1719 0.8914 0.510 2.16 1.357 Ry mno) 3.921 Q.256 2370 23.339 13.31 27.0Lt Pr (Pal 38.5 22.07 fonction pressure = doop n longes dut. A to y 024 = op de ho 0.0886 (12) = 0.7033 mm H2O = 6.89 Pa CS Scanned with CamScanner

Dynare possua doop. fitting (Acto Bo) = 0.25( 35-45- 24.027) - 2.15 pa Asting (Boto DFG) = 0.25 (27.027 - 13.312) 3.420 Pa elbow (F) 10 pa outlet goles = 20 pa... Total = 36.272 PM Total Presux at fan outent Aff& Ded = 284 + 6.89+ 36.224 PT = 43.167 pal Pro Ps+ Pu. Index run of dutt is Section AB CP: 38.45) AS- PT PY = 43.169- 38.45 IPs - 4.717 pa Static Pressure 21 cat inden sun. CS Scanned with CamScanner
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