What is the purpose of the metering device in a vapor-compression refrigeration cycle?

• A. To compress refrigerant.
• B. To condense refrigerant.
• C. To control refrigerant flow into the evaporator to maintain the proper pressure drop.
• D. To cool the refrigerant.

Answer: (C)

The main concept is that the metering device regulates how much liquid refrigerant enters the evaporator by creating a controlled pressure drop from the high-pressure side to the low-pressure evaporator side. This throttling lowers the refrigerant’s pressure and temperature so it can begin to boil in the evaporator, absorbing heat from the space being cooled. By modulating or restricting flow, it helps prevent flooding the evaporator with liquid or starving it of refrigerant, ensuring the right amount evaporates to match the load. The device does not compress the refrigerant (that’s the compressor), nor does it condense it (that’s the condenser), and while expansion causes cooling, the metering device’s primary role is to control flow and pressure, not to actively cool.