What role does the expansion valve play in a heat pump system?

The expansion valve plays a crucial role in a heat pump system by regulating the flow of refrigerant to maintain the desired pressure. As the refrigerant flows through the expansion valve, it experiences a drop in pressure, which allows it to expand and cool before entering the evaporator coil. This cooling effect is essential for the heat absorption process, where the refrigerant evaporates and absorbs heat from the environment. By controlling the flow of refrigerant, the expansion valve ensures that the heat pump operates efficiently, maintaining optimal pressure and temperature conditions within the system.

The other choices do not accurately describe the primary function of the expansion valve. While it does influence refrigerant pressure by regulating flow, it does not directly increase refrigerant temperature, remove moisture, or convert gaseous refrigerant into liquid. Each of these actions is performed by different components within the heat pump system, highlighting the specific and vital function of the expansion valve in maintaining overall system efficiency.