Hydraulic Machines MCQ with answer and solution

Concept

Work saved by air vessel in reciprocating pumps

Formula

NONE

Step-by-step solution

1. Air vessels in reciprocating pumps reduce friction head loss by maintaining continuous flow in connected pipes. 2. In a single-acting reciprocating pump, the work done against friction with an air vessel is 39.2% of work done without it. 3. The fraction of work saved by fitting an air vessel is 1 - 0.156 = 0.844 (or 84.4%). Answer: B

Explanation

An air vessel fitted to a single-acting reciprocating pump maintains a continuous and uniform flow rate in the suction and delivery pipes. This continuous flow significantly reduces the acceleration head and friction losses in the pipe network. Theoretical analysis proves that this reduction saves 84.4 percent of the work done against friction, which corresponds to 0.844.

Why the other options are wrong

A) The work saved by fitting an air vessel to a single acting reciprocating pump is 84.4%, not 39.2%. C) The value 48.8% represents the work saved for a double acting reciprocating pump. D) The theoretical maximum work saved for a single acting reciprocating pump is 84.4%.

Shortcut

Air vessel on single-acting pump saves 84.4% work (double-acting saves 39.2%).

Common mistake

Confusing the work saved in a single-acting reciprocating pump (84.4%) with a double-acting reciprocating pump (39.2%).