Page:Sheet Metal Drafting.djvu/228

214 (b) How many and what kinds of machines are to be served by the branch pipes? (c) Losses caused by friction, and the effects upon static and velocity pressures caused by changes in cross-sectional area of the duct.

Item (c) is a matter that largely concerns the engineer although the sheet metal worker would do well to have some understanding of these things.

Items (a) and (b), however, are matters of common arithmetic and the following problems are based on them.

Problem 52A.—The fan outlet measures 19"×35½". One branch of a split header is equal in area to 69 per cent of the area of the outlet. If both branch pipes are round, what are their diametrs?

Problem 52B.—A 20" pipe carries 75 per cent of the air from a split header. What is the diameter of the other round pipe?

Problem 52C.—A split header has one 15" and one 18" branch. What will be the dimensions of the rectangular opening 19" wide that will accommodate these two branches?

Problem 52D.—On one side of a fan the machines to be served require four 6", three 4", and two 3" pipes, while those on the other side require six 8", three 6", and two 4" pipes. What will be the area of the branch pipes that are needed to serve these machines? (Hint: Loss of head not considered.)