How does a capillary tube function in a refrigeration system?

A capillary tube functions in a refrigeration system as an expansion device, controlling the flow of refrigerant between the high-pressure and low-pressure sides of the system. Its primary role is to regulate the amount of refrigerant that enters the evaporator coil, thereby allowing for the proper absorption of heat.

As the refrigerant passes through the capillary tube, it undergoes a pressure drop due to the narrow passage. This pressure drop is essential because it converts the refrigerant from a liquid state to a low-pressure, low-temperature mixture of liquid and vapor when it enters the evaporator. By controlling the flow rate of the refrigerant based on system demands, the capillary tube ensures efficient refrigeration cycle operation and contributes to maintaining the desired cooling effect within the system.

In contrast, the other options do not accurately represent the functions of a capillary tube. It does not compress refrigerant or act as a heat exchanger, which are roles performed by other components in the system. Additionally, while filtering impurities is an important task within refrigeration systems, this function is typically handled by filters or driers, not by the capillary tube itself.