What device on a heat pump reverses the flow of refrigerant when switching between cooling and heating?

The device that reverses the flow of refrigerant in a heat pump when switching between the cooling and heating modes is the reversing valve. This component is essential because it allows the heat pump to serve as both an air conditioner in cooling mode and a heater in heating mode by altering the direction of the refrigerant flow.

In cooling mode, the reversing valve directs the refrigerant to absorb heat from the indoor air (thus cooling it) and to release that heat outside. Conversely, in heating mode, the reversing valve changes the flow of the refrigerant so that it absorbs heat from the outdoor air and transfers that heat indoors. This dual functionality is what makes heat pumps efficient for both heating and cooling, contributing to their versatility in climate control applications.