Which component has no moving parts and is commonly used as a fixed restriction in metering?

Which component has no moving parts and is commonly used as a fixed restriction in metering?

• A. Electronic vacuum gauge
• B. Bourdon gauge
• C. Capillary tube
• D. Piston-type regulator

Answer: (C)

Capillary tubes are fixed throttling devices with no moving parts, so the flow they allow is set by the tube’s tiny diameter and length. When high-pressure liquid refrigerant enters the capillary, it experiences a large pressure drop as it passes through, expanding into the lower-pressure evaporator side. This constant, nonadjustable restriction metering the refrigerant helps achieve the desired cooling without any moving components. In contrast, devices like Bourdon gauges, piston-type regulators, or electronic vacuum gauges involve moving parts or sensing elements, so they aren’t fixed restrictions.

Capillary tubes are fixed throttling devices with no moving parts, so the flow they allow is set by the tube’s tiny diameter and length. When high-pressure liquid refrigerant enters the capillary, it experiences a large pressure drop as it passes through, expanding into the lower-pressure evaporator side. This constant, nonadjustable restriction metering the refrigerant helps achieve the desired cooling without any moving components. In contrast, devices like Bourdon gauges, piston-type regulators, or electronic vacuum gauges involve moving parts or sensing elements, so they aren’t fixed restrictions.