Question

A compound pipe (new cast iron) system consists of pipes of length 1800 m and diameter 50 cm, length 1200 m and diameter 40 cm and length 600 m and diameter 30 cm connected in series. The equivalent length of 40 cm diameter pipe will be nearly

• A. 4300 m
• B. 4400 m
• C. 4500 m
• D. 3600 m

Answer 1

The correct option is A 4300 m

The equivalence of head loss in compound pipe and equivalent pipe is the basis for finding the equivalent length.

$\frac{L_1}{D_1^5}+\frac{L_2}{D_2^5}+\frac{L_3}{D_3^5}=\frac{L_e}{D_e^5}$

$\therefore L_e[\frac{1800}{(50{)}^5}+\frac{1200}{(40{)}^5}+\frac{600}{(30{)}^5}]\times (40{)}^5$

$=4318.2m$