Load & DesignQuestion 15 of 110
Friction rate in duct design is typically expressed in which units?
a.CFM per square foot
b.BTU per hour
c.Inches of water column per 100 feet of duct
d.Feet per minute
Explanation
Friction rate expresses the pressure loss per unit length of duct, in inches of water column per 100 feet. In Manual D, the available static pressure and total effective length set the design friction rate used to size ducts. A higher friction rate yields smaller, higher-velocity ducts.
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