Refrigeration fundamentals — identify the correct statements. Which of the following statements about absorption/compression systems and sub-cooling is/are correct?

Introduction / Context:
Refrigeration systems can be broadly classified into vapour compression and vapour absorption types. Sub-cooling in the condenser is another practical aspect that affects system capacity and performance. This question checks basic conceptual understanding.

Given Data / Assumptions:

• Idealized descriptions are acceptable (e.g., adiabatic/isentropic compression as a model).
• Condenser sub-cooling refers to cooling the liquid below its saturation temperature at the condensing pressure.

Concept / Approach:
Absorption systems replace mechanical compression by thermal “compression” using an absorber, pump, generator, and rectifier. Sub-cooling increases the net refrigerating effect by raising the enthalpy difference across the expansion device. In vapour compression, the compressor indeed draws vapour and compresses it (ideally adiabatically/isentropically) to the condensing pressure.

Step-by-Step Solution:
(a) True: absorption cycle avoids mechanical compression of the refrigerant itself.(b) True: better condenser heat transfer (e.g., more water flow or lower coolant temperature) raises sub-cooling.(c) True: fundamental description of the compression process.Hence, all statements are correct.

Verification / Alternative check:
Cycle diagrams show no compressor in absorption systems; instead, a solution pump is used. p-h charts demonstrate the benefit of sub-cooling.

Why Other Options Are Wrong:
Choosing anything other than “all of the above” wrongly denies one or more correct fundamentals.

Common Pitfalls:
Assuming sub-cooling is fixed; it depends on condenser performance and ambient conditions.

Final Answer:
all of the above