How does a capillary tube function in refrigeration systems?

The correct response highlights the function of a capillary tube in refrigeration systems as a fixed restriction. In these systems, a capillary tube is typically installed between the condenser and evaporator to control the flow of refrigerant. The tube's small diameter and specific length create a pressure drop that regulates the refrigerant's movement into the evaporator. This fixed restriction mechanism allows the system to maintain the necessary pressure and flow rate according to the cooling demands.

Because the capillary tube offers a constant restriction, it helps in providing a steady supply of refrigerant under various load conditions, which is essential for the efficient operation of the refrigeration cycle. This functionality distinguishes it from components with other roles, like heat exchangers or pressure relief valves, which serve different purposes in managing temperature and safety in refrigeration systems.