Question

4. (3 pt) Compute the required size of a new, clean Schedule 40 steel pipe that will carry 0.8 ft3/s of water at 50°F and limit the pressure drop to 3.80 psi over a length of 100 ft of pipe if one end of the pipe is 30 ft higher than the other. Specify the nominal size and ID of your chosen Schedule 40 Pipe (reference Table F.1).

Answer 1

Apply energy equation b/w two ends of pipe. p/gamma + V^2/2g + 2 z = p/r + V^2/2g + z h_L Delta p/r + Delta z = h_L 3.80 (144)/62.4 + 30 = f L V^2/2gD 38.769 = 0.02 (100) (0.8)^2/2(32.2) (pi/4)^2 (D)^5 D = 0.242 ft. D = 2.905 in. Therefore Nominal size of pipe = 3 inches ID = 3.5 2(0.216) ID = 3.5 - 2(0.216) ID = 3.068 in. Nominal size = 3 inches.