What is the state of the refrigerant as it enters the metering device?

• A. Low pressure vapor
• B. High pressure vapor
• C. Low pressure liquid
• D. High pressure liquid

Answer: (D)

The state being tested is high-pressure liquid (often subcooled) as it enters the metering device. After the compressor, the refrigerant is forced through the condenser, where it releases heat and becomes a dense, high-pressure liquid. The metering device sits right after this high-pressure liquid, and its job is to reduce that pressure before the refrigerant enters the evaporator. If it were vapor, or if it were low-pressure liquid, it wouldn’t be prepared for the throttling process the metering device performs. The high-pressure liquid entering the metering device is ideal because the sudden pressure drop then allows rapid cooling and partial vaporization in the evaporator to absorb heat.