In an environmental control system, which component meters the flow of refrigerant into the evaporator?

In an environmental control system, which component meters the flow of refrigerant into the evaporator?

• A. Condenser
• B. Receiver-drier
• C. Expansion valve
• D. Compressor

Answer: (C)

Metering the refrigerant entering the evaporator is the job of the expansion valve. This device throttles the high-pressure liquid refrigerant, dropping its pressure (and temperature) so it can flash evaporate as it enters the evaporator. By controlling how much refrigerant can flow into the evaporator, it matches the evaporator load and helps maintain proper superheat, preventing both liquid carryover back to the compressor and insufficient cooling. The condenser simply rejects heat from the high-pressure side and does not regulate the amount of refrigerant flowing to the evaporator. The receiver-drier stores liquid refrigerant and removes moisture and contaminants, but it does not meter flow. The compressor circulates and pressurizes the refrigerant, but it does not throttle or meter the amount that enters the evaporator.

Metering the refrigerant entering the evaporator is the job of the expansion valve. This device throttles the high-pressure liquid refrigerant, dropping its pressure (and temperature) so it can flash evaporate as it enters the evaporator. By controlling how much refrigerant can flow into the evaporator, it matches the evaporator load and helps maintain proper superheat, preventing both liquid carryover back to the compressor and insufficient cooling.

The condenser simply rejects heat from the high-pressure side and does not regulate the amount of refrigerant flowing to the evaporator. The receiver-drier stores liquid refrigerant and removes moisture and contaminants, but it does not meter flow. The compressor circulates and pressurizes the refrigerant, but it does not throttle or meter the amount that enters the evaporator.