Selecting a compressor type — identify the correct statement Which of the following statements about reciprocating air compressors and clearance effects is correct?

Introduction / Context:
Different compressor families suit different pressure and flow ranges. Reciprocating machines excel at high pressures and modest flows, while dynamic compressors (centrifugal/axial) excel at large flows and moderate pressures. Clearance effects also matter for capacity and power predictions.

Given Data / Assumptions:

• Idealized indicator diagram assumptions for power.
• Finite clearance ratio in positive-displacement compressors.
• Same delivery pressure and suction conditions used in comparisons.

Concept / Approach:
(a) Reciprocating units can achieve very high discharge pressures because the trapped gas is compressed in a closed cylinder; volumetric throughput is limited, fitting low-volume tasks. (b) In the ideal cycle without leakage, the indicated work per kg depends mainly on inlet/outlet states and polytropic index; clearance alters capacity (eta_v) but has negligible effect on indicated work per unit mass, so for a fixed mass delivery the power change is small in the ideal model.

Step-by-Step Solution:
Recognize application domains: high pressure → reciprocating; high flow → dynamic.Note that clearance reduces volumetric efficiency, not the ideal work per kg compressed.Thus statements (a) and (b) are both correct → choose (c).

Verification / Alternative check:
Textbook indicator diagrams show identical compression/expansion lines irrespective of clearance for the same end pressures, confirming negligible power change per kg.

Why Other Options Are Wrong:
(d) contradicts fundamentals; (e) reverses typical selection (centrifugal are for higher flows, not the highest pressures at tiny flows).

Common Pitfalls:
Equating reduced capacity from clearance with reduced power per kg—these are distinct.

Final Answer:
Both (a) and (b) are correct