Final answer:
A heat pump transfers thermal energy from a cooler to a warmer environment using a cycle that involves an evaporator, compressor, condenser, and expansion valve. It is highly efficient, able to move heat with less work per Joule of energy transferred, suitable for both heating and cooling.
Step-by-step explanation:
How Does a Heat Pump Work?
A heat pump is a device that moves thermal energy from one location to another by doing work. Contrary to natural heat flow from hot to cold spaces, it transfers heat from cooler spaces to warmer ones. This is achieved using a cycle involving four main components: the evaporator, compressor, condenser, and expansion valve.
In the heating mode, the process starts in the evaporator where the working fluid, typically a non-CFC refrigerant, absorbs heat (Qc) from the cold outside air and turns into a gas. The compressor then increases the temperature and pressure of this gas and pumps it into the condenser coils located inside the space to be heated. Here, because the gas is now at a higher temperature than the indoor air, heat energy is released into the room as the gas condenses back to a liquid. Finally, the working fluid, slightly cooled now, passes through an expansion valve and returns to the outdoor evaporator coils, ready to begin the cycle anew. Heat pumps are very efficient as they use less work to move each Joule of heat, making them highly effective for both heating and cooling purposes.