Exam 33: Air Flow Calculations

The air flow rate in a duct can be found by multiplying the area of the duct times the air speed in the duct.

The flow of air in a duct should stay less than 490 ft/min to keep the air flow from being too noisy. The dining room of a house is to have a flow of 150 cu ft/min to have proper air exchange. What should be the smallest duct area going to this room? Round answer to the nearer thousandths sq ft.

The air flow in a duct in a house should have a speed faster than 50 ft/ min so that it does not lose heat in the winter or gain heat in the summer before reaching the room. The dining room of a house is to have a flow of 150 cu ft/min to have proper air exchange. What should be the largest duct area going to this room?

A fan produces a flow of 3,400 CFM. What area duct will give an air speed of 350 ft/min in the duct? Round answer to the nearer hundredth square foot.

A 3,250 sq ft house with 8 foot ceilings has 3 return ducts. What size must the ducts be to handle 7 exchanges per hour with a flow of 350 ft/min? Round the answer to the nearer hundredth square foot.

What would be the smallest bedroom that should be supplied air by a 10-inch by 12-inch duct with a flow of 50 ft/min for 6 changes each hour? Round the answer to the nearer hundredth cubic foot if needed.

The units of air flow rate are given in square feet per minute.

A room in a house is 14 feet 6 inch by 12 feet 6 inches. It has 8-ft ceilings. What must the air flow into the room be in cubic feet per minute to have 6 air changes per hour? Round the answer to the nearer hundredth CFM if needed.

A fine dining restaurant wants quiet air flow in its dining room, so a duct flow of 250 ft/min is desired. The size of the room requires the duct to have a flow of 1,400 CFM to properly control the room's environment. What is the cross-sectional area of the duct to the nearer tenth square foot?

A distribution duct has an area of 2.1 sq ft and an air speed of 340 ft/ min. A side duct of 1.0 sq ft splits off. The main duct reduces in size to 1.4 sq ft. What is the air flow in the main duct after the split?