How does the refrigerant appear when it enters the evaporator of a vapor-cycle cooling system?

When the refrigerant enters the evaporator of a vapor-cycle cooling system, it is typically in the form of a low-pressure liquid. This is because, prior to entering the evaporator, the refrigerant is expanded through an expansion valve or device, which reduces its pressure. The low-pressure liquid then absorbs heat from the cabin air, which causes it to evaporate and change into a vapor as it circulates through the evaporator. This process effectively cools the air, as the refrigerant takes heat away from the cabin environment.

Understanding this process is key in recognizing the role of the evaporator in the cooling cycle, where the transition from liquid to vapor signifies the absorption of heat. This is essential for maintaining a comfortable cabin atmosphere.