Question

Which of the following device maintains constant level of refrigerant in the evaporator by supplying quantity of liquid refrigerant required to take the load in the evaporator ?

• A. Condenser
• B. Capillary tube
• C. Float valve
• D. Filter

Hint:

Float valves are classified into:
- Low-side float valves: Maintain a constant level of liquid in the evaporator.
- High-side float valves: Maintain a constant level of liquid in the receiver.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
In large flooded evaporators, it is necessary to maintain a constant liquid refrigerant level to optimize boiling heat transfer and prevent liquid carryover into the compressor suction line.
Detailed Explanation:
Let us analyze the functions of the devices listed:
- Float Valve (C): A float valve uses a buoyant ball floating on the liquid refrigerant surface to regulate flow.
As the refrigerant boils and evaporates due to the cooling load, the liquid level drops.
The falling float opens the valve, allowing more high-pressure liquid refrigerant to enter.
Once the target liquid level is restored, the float rises and closes the valve.
This mechanism maintains a constant liquid level, matching the refrigerant supply to the thermal load on the evaporator.
- Capillary Tube (B): A fixed-bore expansion device that regulates flow based on pressure drop, but cannot adjust to maintain a constant liquid level under variable loads.
- Condenser (A): A component that rejects heat and condenses refrigerant, but does not control the evaporator level.
- Filter (D): A device that removes debris and moisture from the refrigerant loop.

Step 2: Final Answer:
The device used to maintain a constant level of refrigerant in the evaporator is a Float valve.