Which metering device uses a sensing bulb to maintain superheat by adjusting flow?

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The thermostatic expansion valve uses a sensing bulb placed on the evaporator outlet to keep the refrigerant leaving the evaporator at a set superheat by throttling flow. The bulb contains a small amount of refrigerant that responds to temperature: when the evaporator outlet warms, the bulb pressure rises and acts on a diaphragm to reduce the valve opening, cutting refrigerant flow; when it cools, the pressure drops and the valve opens more to allow additional flow. This feedback maintains a desired superheat, ensuring the refrigerant is fully vaporized in the evaporator and preventing liquid from reaching the compressor. Other devices don’t adjust flow based on evaporator conditions: fixed restrictions like an orifice or capillary tube provide a constant flow, and a receiver-drier is simply storage/moisture removal, not a metering element.