Which statement is not true of a capillary tube metering device?

Which statement is not true of a capillary tube metering device?

• A. They maintain constant evaporator pressure
• B. They are fixed restriction devices
• C. They have no moving parts
• D. They meter refrigerant based on differential pressure across the tube

Answer: (A)

Capillary tubes are fixed, passive restrictions that meter refrigerant solely by the pressure drop from the high-pressure side to the low-pressure side. They have no moving parts and do not actively regulate or hold the evaporator pressure. The amount of refrigerant that flows depends on the differential pressure across the tube and the refrigerant’s properties, so the evaporator pressure will vary with load and operating conditions rather than be kept constant. This is why the statement about maintaining constant evaporator pressure is not true. The capillary tube does, however, have fixed restriction, no moving parts, and meter based on the differential pressure across the tube.

Capillary tubes are fixed, passive restrictions that meter refrigerant solely by the pressure drop from the high-pressure side to the low-pressure side. They have no moving parts and do not actively regulate or hold the evaporator pressure. The amount of refrigerant that flows depends on the differential pressure across the tube and the refrigerant’s properties, so the evaporator pressure will vary with load and operating conditions rather than be kept constant. This is why the statement about maintaining constant evaporator pressure is not true. The capillary tube does, however, have fixed restriction, no moving parts, and meter based on the differential pressure across the tube.