In an HVAC system, what is the role of the expansion valve?

The expansion valve plays a critical role in an HVAC system by controlling the flow of refrigerant into the evaporator coil. Its primary function is to decrease the refrigerant pressure and temperature as it moves from the high-pressure side of the system to the low-pressure side. This reduction in pressure allows the refrigerant to expand and cool before it enters the evaporator, which is where heat exchange occurs. By lowering the pressure and temperature, the refrigerant can absorb heat from the indoor environment effectively, transforming from a liquid to a gas as it takes on heat. The expansion valve essentially enables the refrigerant to perform its function of absorbing heat and thereby facilitates the cooling process that maintains desired indoor temperatures. Understanding the function of the expansion valve is fundamental to grasping the overall operation of HVAC systems and their efficiency.