Which statement about capillary tubes is true?

Which statement about capillary tubes is true?

• A. They are adjustable by a valve
• B. They are electrically controlled
• C. They are fixed restriction devices
• D. They have internal moving parts

Answer: (C)

Capillary tubes are fixed restriction devices. The cooling effect comes from throttling the liquid refrigerant as it travels through a narrow bore, which drops pressure from the condenser side to the evaporator side and allows some vaporization to occur inside the evaporator. Because the restriction is built into the tube by its precise diameter and length, there are no moving parts inside and no external mechanism to adjust. They aren’t electrically controlled and there’s no valve to tune the flow. If you need to change capacity, you’d change the tube size/length or use a different metering method, since the throttling behavior is essentially fixed once the tube is manufactured.

Capillary tubes are fixed restriction devices. The cooling effect comes from throttling the liquid refrigerant as it travels through a narrow bore, which drops pressure from the condenser side to the evaporator side and allows some vaporization to occur inside the evaporator. Because the restriction is built into the tube by its precise diameter and length, there are no moving parts inside and no external mechanism to adjust. They aren’t electrically controlled and there’s no valve to tune the flow. If you need to change capacity, you’d change the tube size/length or use a different metering method, since the throttling behavior is essentially fixed once the tube is manufactured.