What is the purpose of the expansion valve in a heat pump?

The purpose of the expansion valve in a heat pump is to regulate the flow of refrigerant and reduce its pressure before it enters the evaporator. This is a critical function in the refrigeration cycle. The refrigerant, after leaving the condenser, is in a high-pressure state, and its temperature is higher than what is needed for efficient heat absorption in the evaporator.

When the refrigerant passes through the expansion valve, its pressure drops significantly, which in turn lowers its temperature as it transitions into a low-pressure gas. This drop in temperature allows the refrigerant to absorb heat effectively from the surrounding air in the evaporator, creating more efficient heating or cooling as the cycle continues.

The expansion valve essentially acts as a control device that maintains the proper refrigerant flow and pressure in the system, which is essential for the overall efficiency and performance of the heat pump.