ESCO Air Conditioning Practice Exam 2026 – Complete Study Resource

In an air conditioning system that employs a thermostatic expansion valve, the primary function of the valve is to regulate the flow of refrigerant into the evaporator. This regulation allows for optimal temperature and pressure conditions, which are crucial for efficient cooling.

As refrigerant flows into the evaporator, it begins to absorb heat from the indoor air, resulting in a phase change where the refrigerant evaporates from a liquid to a gas. During this process, the refrigerant's temperature drops as it absorbs heat, which means that by the time it exits the evaporator, its temperature will be lower compared to when it entered. Consequently, the evaporator outlet temperature will typically be cooler than the evaporator inlet temperature. This cooling effect is vital for the system's efficiency and effectiveness in providing comfort cooling to the enclosed space.

This cooling of the refrigerant is essential because the more heat absorbed from the indoor space, the more effective the air conditioning system becomes at maintaining desired indoor temperatures. Thus, the characteristic of the evaporator outlet temperature being cooler than the inlet is a key aspect of how refrigerant systems are designed to function effectively.