1. The circumference of a round duct is about 37.5 inches. The average velocity
pressure (VP) of air flowing in the duct is 0.30 inch w.g. at standard conditions
(STP). Please calculate:
a) Duct diameter
b) Average Vduct
c) Air flowrate Q, and compare your Q with that on Chart 5 to determine the
2. The average air velocity pressure (VP) of an airstream in a duct is 0.90 inch w.g.
The temperature of the air is T = 75 ℉ and the duct is located 1,000 ft above sea
level. What is the actual average air velocity?
Hint: you need find B.P. online for df calculation.
3. Standard air (d=1) moves through a galvanized duct system at the velocity (Vaverage)
of 5,000 fpm and Dduct is 8 inches.
• List the three equations that you use to solve the problem.
• Please estimate VP
• Please find the loss factors K from the Charts, and then estimate static pressure
loss for each component in each branch (a-f).
• Please calculate the friction loss for the entire duct system, La-f = 50’, galv duct
a. Flanged hood (round)
b. Plain duct hood (round)
c. Elbow, 3-piece, R/D=1.5,
d. Elbow, 5-piece, R/D=1.0,
e. Elbow, 4-piece, R/D=2.0,
f. Branch entry, 60° included
Friction loss (FL), La-f = 50’,
Where can you find the K
4. Discuss how you can use blast gate method to balance the SP between branches.
You can give an example and/or use diagram.
5. A ventilation system has two branches: one branch requires to have SP of – 5.3”
w.g. and Q of 4.8 scfm, and the other needs -6.1 “w.g and 5.2 scfm. 1) Determine
the governing static pressure for a ventilation system; and 2) Determine the Qcorrect
and specify whether the Qcorrect you calculate is for governing or for non-governing
6. There are several limitations when using blast gate method. Please pick one
limitation of your interest, and discuss what method(s) YOU can use to solve the
7. A ventilation system with two branches: one branch requires to have SP of – 5” w.g.
and Q of 4.8 scfm. Determine the maximum range of SP for another branch that
allow you to determine the governing static pressure without a further design change
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