What happens to pressure and temperature of a refrigerant as it passes through an expansion valve?

As a refrigerant passes through an expansion valve, it undergoes a process known as throttling. During this process, the refrigerant experiences a rapid decrease in pressure as it transitions from the high-pressure side of the system (where it has been condensed into a liquid) to the low-pressure side (where it will begin to evaporate).

When the pressure drops, the refrigerant’s ability to hold heat also changes. As a result, the temperature of the refrigerant decreases as it expands and moves into an area with lower pressure. This is a fundamental principle in thermodynamics, where a decrease in pressure often leads to a decrease in temperature, especially in the context of refrigeration cycles.

Thus, the correct statement is that as the refrigerant passes through the expansion valve, both pressure and temperature decrease. This cooling is essential for the refrigeration cycle, as it prepares the refrigerant to absorb heat in the evaporator, allowing for effective cooling in the overall system.