Consider a rectangular sheet-metal duct carrying air at 60 F at 100 kPa. The volume flow rate at the entrance to the duct is 1200 ft³/min. A portion of the air exits through a grille, as shown in the sketch. On the basis of noise considerations, the average velocity in the duct is to be limited to 600 ft/min. The height of the duct is 12 in.

A. Determine the minimum duct width required, subject to the constraint that the duct is only available with dimensions in even increments of 2 inches (e.g., 14, 16, 18 inches, etc.).

B. Determine the volumetric flow 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 inches by 15 inches.

C. Determine the mass flow 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.

Transcribed Image Text:

Air Air W = ? " NAMAZING WEINER Duct Duct Air Grille 12" Top view Side view