Question

For a simple vapour compression refrigeration, which of the following thermodynamic cycles (1-2-3-4) are possible? Here, \( T \), \( P \), \( S \), and \( h \) indicate temperature, pressure, specific entropy, and specific enthalpy, respectively.

• A. A
• B. B
• C. C
• D. D

Hint:

In vapor-compression refrigeration, it is crucial to understand the typical behavior of the refrigerant in the thermodynamic cycles using different diagrams, such as \( T \)-\( S \) and \( P \)-\( h \).

Answer 1

The Correct Option is A, B

A vapor compression refrigeration cycle typically involves four major stages: compression, condensation, expansion, and evaporation. The correct thermodynamic cycle representation involves proper relationships between pressure, temperature, specific entropy, and specific enthalpy. - Option (A): This is a correct representation of a typical vapor-compression refrigeration cycle on the \( T \) vs \( S \) diagram. In this diagram:
- The curve from point 1 to point 2 represents the compression of the refrigerant.
- From point 2 to point 3, the refrigerant undergoes condensation.
- From point 3 to point 4, the expansion of refrigerant happens.
- From point 4 to point 1, the refrigerant undergoes evaporation.
This cycle represents a typical refrigerant working in the vapor-compression refrigeration system. - Option (B): This diagram on the \( P \) vs \( h \) diagram also represents a correct vapor-compression refrigeration cycle. In this diagram:
- Point 1 to 2 represents compression where the enthalpy rises.
- Point 2 to 3 shows the condensation process.
- Point 3 to 4 is the expansion process, showing a drop in enthalpy.
- Point 4 to 1 shows the evaporation process, where the enthalpy increases again.
This is another valid cycle representation that reflects the energy transformation within the refrigeration cycle. - Option (C): This cycle on the \( P \) vs \( h \) diagram is not typical for a refrigeration cycle as it does not properly represent the expected thermodynamic states of refrigerant during compression, condensation, expansion, and evaporation. The process in this diagram does not follow the expected order of events.
- Option (D): The cycle in this \( T \) vs \( S \) diagram is also not typical as it shows a non-standard relationship between the points that doesn't align with the typical behavior expected in vapor-compression refrigeration.
Thus, the correct answers are (A) and (B).