Simple CO₂ Heat Pump

Heat pumps transfer heat from a low-temperature heat source to a higher-temperature heat sink and are widely used for space and water heating, industrial heat recovery, and simultaneous heating and cooling. CO₂ (R744) is a natural refrigerant with attractive thermodynamic and environmental properties for many heat-pump applications. This example demonstrates a simple CO₂ vapor-compression heat pump in which CO₂ evaporates by absorbing heat from a water stream at approximately room temperature, thereby cooling the water. The refrigerant is then compressed to a higher pressure and temperature and transfers heat to a second water stream. After heat rejection, the CO₂ is expanded through a valve and returned to the evaporator, completing the cycle.