Pressure rise mechanism in a sliding vane blower: evaluate the two-stage explanation. Statement to evaluate: In a vane blower, the pressure increases first due to internal compression (decreasing cell volume) and then due to some backflow from the discharge until line pressure is reached. Choose whether the statement is correct.

Given / Device
Sliding vane rotary machines trap air between vanes and the casing; as the trapped pocket moves, its volume reduces, compressing the air.

Concept/Approach
In a vane compressor, internal compression occurs before the trapped air reaches the discharge port. When the pocket opens to the outlet, any remaining pressure difference is equalized by a brief backflow from the delivery line.

Contrast
A Roots blower has virtually no internal compression; pressure rise is primarily due to backflow/mixing at the outlet.

Final Answer
Agree.