Which of the following best describes the typical relationship between evaporator outlet and inlet temperatures in a TXV system?

• A. The outlet is warmer than the inlet
• B. The outlet is colder than the inlet
• C. They are always equal
• D. The relationship cannot be determined from this data

Answer: (A)

In an evaporator, the refrigerant absorbs heat as it passes through, so its energy rises from inlet to outlet. The liquid entering from the expansion valve is cold and at low pressure. As it travels through the evaporator, it boils and turns into vapor, taking in heat in the process. By the time it exits, the refrigerant is a higher-energy vapor (often superheated), which means its temperature is higher than the temperature at the inlet. The thermostatic expansion valve helps maintain the desired superheat at the outlet, but the fundamental point is that heat absorption in the evaporator makes the outlet warmer than the inlet. The other options don’t fit because they would imply no heat transfer or cooling at the outlet, which contradicts how the evaporator operates.