Which component in a heat pump is responsible for changing refrigerant from a liquid to a gas?

In a heat pump, the component responsible for changing the refrigerant from a liquid to a gas is the evaporator. This process occurs when the refrigerant flows through the evaporator coils, where it absorbs heat from the surrounding environment. As it absorbs heat, the refrigerant experiences a change in state and vaporizes, transitioning from a liquid to a gaseous form.

The evaporator operates by facilitating heat exchange, allowing the cooler refrigerant to absorb heat, often from outside air (in heating mode) or indoor air (in cooling mode), depending on the system's operation. This phase change is crucial in the heat pump cycle, as it enables the system to extract or release heat efficiently.

In contrast, the other components, while essential to the overall functioning of the heat pump, perform different roles. The compressor is responsible for pressurizing the gaseous refrigerant, the condenser changes the refrigerant from a gas back into a liquid by releasing heat, and the expansion valve controls the flow of refrigerant into the evaporator, but does not facilitate the phase change itself.