Question

In a mechanical refrigeration system, the highest temperature of refrigerant occurs

• A. Between condenser and evaporator
• B. In evaporator
• C. Before expansion valve
• D. Between compressor and condenser

Hint:

In any vapor-compression cycle (refrigeration or heat pump), the compressor's discharge line always carries the hottest fluid, while the expansion valve's exit carries the coldest.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks to identify the location of the highest refrigerant temperature within a standard vapor-compression refrigeration cycle.


Step 3: Detailed Explanation:
Let's analyze the state of the refrigerant across the standard components of a refrigeration cycle:
• Compressor: The refrigerant enters as a low-pressure, low-temperature vapor. The compressor does mechanical work on the fluid, compressing it. This process is ideally isentropic, leading to a significant increase in both pressure and temperature. The refrigerant exits the compressor as a highly superheated vapor.
• Condenser: The hot, high-pressure vapor enters the condenser where it rejects heat to the environment. It cools down to its saturation temperature and condenses into a liquid. Thus, temperature decreases here.
• Expansion Valve: The high-pressure liquid undergoes an isenthalpic expansion, causing a sharp drop in both pressure and temperature.
• Evaporator: The cold, low-pressure mixture enters the evaporator, absorbs heat from the refrigerated space, and evaporates back into a vapor before returning to the compressor. The temperature is lowest here. Therefore, the highest temperature in the entire cycle is reached immediately after the compression process, right before any heat is rejected. This physical location is exactly between the compressor and the condenser.


Step 4: Final Answer:
The highest temperature occurs between the compressor and condenser.