Question

The COP of a reversed Carnot cycle is most strongly depend up on __________.

• A. Evaporator temperature
• B. Condenser temperature
• C. Refrigerant
• D. Specific heat

Hint:

In refrigeration, raising the evaporator temperature closer to the condenser temperature always dramatically increases the system's efficiency (COP).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
A reversed Carnot cycle represents the idealized thermodynamic cycle for vapor-compression refrigeration systems.
The Coefficient of Performance (COP) is the ratio of desired cooling effect to the required work input.

Step 2: Detailed Explanation:
The thermodynamic COP of a reversed Carnot refrigeration cycle operating between a lower evaporator temperature (\(T_L\)) and a higher condenser temperature (\(T_H\)) is expressed as:
\[ \text{COP} = \frac{T_L}{T_H - T_L} \] where temperatures are expressed in Absolute Kelvin (\(\text{K}\)).
Let us analyze how changes in these temperatures affect the COP:
- For a fixed condenser temperature (\(T_H\)), decreasing the evaporator temperature (\(T_L\)) causes the numerator to decrease and the denominator (\(T_H - T_L\)) to increase, resulting in a very sharp drop in COP.
- For a fixed temperature difference (\(T_H - T_L\)), any change in the lower evaporator temperature (\(T_L\)) has a much more pronounced mathematical effect on the overall value of the COP than a corresponding change in \(T_H\).
Therefore, the operating evaporator temperature is the most critical parameter that determines the thermodynamic efficiency (COP) of the refrigeration system.
- The specific refrigerant and its specific heat do not affect the idealized Carnot COP, which depends strictly on operating temperatures.

Step 3: Final Answer:
Thus, the COP of a reversed Carnot cycle most strongly depends on the Evaporator temperature.