Consider a rectangular sheet-meta! duct carrying air at 60 F at 100 kPa. The vol

Question

Consider a rectangular sheet-meta! duct carrying air at 60 F at 100 kPa. The volume flow rate at the entrance to the duel is 1200 ft3/min. A portion of the air exits through a grille as shown in the sketch. Based on noise considerations, the average velocity in the duct is to be limited to 600 ft/min. The height of the duct is 12 in. Determine the minimum duct width required, subject to the constraint that the duct is only available with dimensions in even increments of 2 in. (e.g., 14, 16, 18 in, etc.). Determine the volumetric How rate through the grille if the velocity of the air entering the room is 35 ft/min, the maximum value for comfort. The dimensions of the grille are 10 by 15 in. Determine the mass How rate through the duct downstream of the grille. Assume that all pressure drops in the duct system are sufficiently small that a uniform pressure is a reasonable approximation.

Explanation / Answer

A) Volumetric Flow Rate=1200 ft^3/min =Velocity*Area (1200 ft^3/min)/(600 ft/min)=2 ft^2

Area=2 ft^2 h=1 ft, w=2ft

B) 35 ft/min*(10 in* 15 in)/144=36.4583 ft^3/min

C) mass flow rate=density*velocity*area you're going to have to use your book to find the density of air at those state

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