Single-acting reciprocating air compressor (no clearance): nature of compression In a single-acting reciprocating air compressor without clearance volume, the thermodynamic path of compression can be considered as which of the following under different cooling conditions?

Introduction / Context:
The idealized thermodynamic path of compression in a reciprocating compressor depends on the heat transfer during the process. Recognizing the limiting and practical cases is essential for estimating power and for sizing cooling equipment.

Given Data / Assumptions:

• No clearance volume (simplifies suction/exhaust dynamics).
• Same suction and discharge pressures for comparison.
• Variable degree of heat removal during compression.

Concept / Approach:
Compression can approach isothermal if heat is removed continuously and effectively (e.g., very slow compression with excellent cooling). It approaches isentropic if the compression is rapid and well insulated (negligible heat exchange). The real-world case most often lies between these extremes and is modeled as polytropic with p v^n = C, where n is between 1 (isothermal) and k (isentropic exponent).

Step-by-Step Solution:

Verification / Alternative check:
Power expressions W_iso, W_poly, and W_isentropic show distinct values; measured indicator diagrams typically align with polytropic modeling but can approach the limits under controlled experiments.

Why Other Options Are Wrong:

Restricting to only one path ignores the role of heat transfer; real machines vary with speed, cooling water rate, and materials.

Common Pitfalls:
Assuming “adiabatic” by default. In many plant compressors with good jackets and intercooling, the effective exponent can be well below k.

Final Answer:

any one of these (isothermal, polytropic, or isentropic)