The amount of inlet required will also be 14·6 square inches per head. Theoretically it ought to be slightly less than that required for outlet, as the outgoing air is more expanded than that entering the room; but practically no allowance need be made for this fact.
The total amount of inlet and outlet required per head = 29·2 square inches.
If the mean temperature of a room is 61°, the external temperature 45°, while the heated column of air is 50 feet, and the required delivery of air 2,000 cubic feet per hour, find the size of inlet and outlet.
v = 8·2√(h(t - t1) ∕ 492)
= 8·2√(50(61 - 45) ∕ 492)
= 10·55 feet per second.
= 37,980 feet per hour.
If we make no allowance for friction, then
a = q ∕ v
= 2,000 ∕ 37,980 square feet.
= 2,000 × 144 ∕ 37,980 = 7·58 square inches.
This gives the required size of outlet. The size of inlet and outlet together = 15·16 square inches.
If 3,000 cubic feet of air are supplied in one hour through an aperture of 12 square inches to a room containing 1,000 cubic feet of space, at what rate does the air enter the room?
12 square inches = 1 ∕ 12 square foot.
a = q ∕ v
1 ∕ 12 = 3,000 ∕ v
Therefore
v = 36,000 feet per hour.
= 10 feet per second.
If a room is supplied with 3,000 cubic feet of air per hour, through a single opening, what must be its area, if the rate of movement of the air is 5 feet per second?