Which component is designed to ensure the refrigerant flows in only one direction?

The component that ensures refrigerant flows in only one direction is the check valve. Its primary function is to prevent backflow, which can lead to inefficiencies and potential damage within the refrigeration system. Check valves are strategically placed in the refrigerant lines to allow the refrigerant to flow towards the desired direction while blocking any reverse flow that might occur when the system is not active or during operational changes.

In contrast, other components like the expansion valve, condenser, and compressor serve different purposes in the refrigeration cycle. The expansion valve regulates the flow of refrigerant into the evaporator, the condenser is responsible for rejecting heat and converting the refrigerant from gas back to liquid, and the compressor compresses the refrigerant, increasing its pressure and temperature to facilitate its movement through the system. These components do not inherently control the direction of refrigerant flow; that specific function is the domain of the check valve.