What are the two types of metering devices?

What are the two types of metering devices?

• A. Orifice tube
• B. Orifice tube and TXVs
• C. TXVs
• D. Accumulator

Answer: (B)

Metering devices control how much refrigerant enters the evaporator, and there are two broad kinds: fixed restrictions and adjustable valves. The fixed type, like an orifice tube, provides a constant restriction so the flow depends mainly on the pressure difference across it. This simple setup works but doesn’t adapt to varying cooling loads. The adjustable type, such as a thermostatic expansion valve (TXV), senses evaporator conditions (superheat) and automatically opens or closes to maintain a desired superheat, letting the system respond efficiently to changes in load. The two together—the fixed orifice tube and the TXV—represent the two main metering device types. An accumulator isn’t a metering device, so it isn’t part of this distinction.

Metering devices control how much refrigerant enters the evaporator, and there are two broad kinds: fixed restrictions and adjustable valves. The fixed type, like an orifice tube, provides a constant restriction so the flow depends mainly on the pressure difference across it. This simple setup works but doesn’t adapt to varying cooling loads. The adjustable type, such as a thermostatic expansion valve (TXV), senses evaporator conditions (superheat) and automatically opens or closes to maintain a desired superheat, letting the system respond efficiently to changes in load. The two together—the fixed orifice tube and the TXV—represent the two main metering device types. An accumulator isn’t a metering device, so it isn’t part of this distinction.