What does the sensing bulb on a TXV monitor?

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Multiple Choice

What does the sensing bulb on a TXV monitor?

The sensing bulb on a TXV monitors the temperature of the refrigerant as it leaves the evaporator. Placed on the suction line at the evaporator outlet, the bulb senses the outlet temperature (which reflects the evaporator’s superheat). A temperature change in the bulb changes the pressure inside the bulb and through the capillary to the valve’s diaphragm. When the evaporator outlet gets hotter (higher superheat), the bulb pressure rises and the valve tightens to reduce refrigerant flow; when it gets cooler, the bulb pressure falls and the valve opens more to increase flow. This feedback keeps the evaporator outlet at the desired superheat, preventing liquid refrigerant from reaching the compressor and promoting efficient heat transfer. It isn’t measuring discharge pressure, ambient temperature, or suction pressure directly.

The sensing bulb on a TXV monitors the temperature of the refrigerant as it leaves the evaporator. Placed on the suction line at the evaporator outlet, the bulb senses the outlet temperature (which reflects the evaporator’s superheat). A temperature change in the bulb changes the pressure inside the bulb and through the capillary to the valve’s diaphragm. When the evaporator outlet gets hotter (higher superheat), the bulb pressure rises and the valve tightens to reduce refrigerant flow; when it gets cooler, the bulb pressure falls and the valve opens more to increase flow. This feedback keeps the evaporator outlet at the desired superheat, preventing liquid refrigerant from reaching the compressor and promoting efficient heat transfer. It isn’t measuring discharge pressure, ambient temperature, or suction pressure directly.

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