Which statement best defines a fixed-orifice metering device?

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Multiple Choice

Which statement best defines a fixed-orifice metering device?

At its core, a fixed-orifice metering device uses a fixed restriction to control how much liquid refrigerant enters the evaporator. The flow is determined by the size of the orifice and the pressure drop across it, not by any sensing or adjustment for load or superheat. Because there’s no mechanism to respond to changing cooling demand, the device can’t adapt to varying conditions, which is why it’s described as a fixed restriction. This makes it different from devices that actively modulate flow based on evaporator superheat (which adjust to load) or that sense superheat to control flow. The fixed restriction approach was common in older high-pressure systems, where simplicity and reliability were prioritized over precise metering across a wide range of conditions.

At its core, a fixed-orifice metering device uses a fixed restriction to control how much liquid refrigerant enters the evaporator. The flow is determined by the size of the orifice and the pressure drop across it, not by any sensing or adjustment for load or superheat. Because there’s no mechanism to respond to changing cooling demand, the device can’t adapt to varying conditions, which is why it’s described as a fixed restriction.

This makes it different from devices that actively modulate flow based on evaporator superheat (which adjust to load) or that sense superheat to control flow. The fixed restriction approach was common in older high-pressure systems, where simplicity and reliability were prioritized over precise metering across a wide range of conditions.

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