CO₂ Heat Pump with Ejector and Dual Evaporators

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 an advanced CO₂ vapor-compression heat pump incorporating an internal heat exchanger (IHX), an ejector, a flash drum, and two evaporators. The ejector uses the pressure energy of the high-pressure refrigerant to entrain a lower-pressure CO₂ stream, recovering part of the energy that would otherwise be lost during throttling. The flash drum separates the refrigerant streams and supplies liquid CO₂ to the lower evaporator through an expansion valve, while vapor is returned toward the compressor. The two evaporators provide cooling at different locations in the cycle, while the compressed CO₂ transfers heat to the hot-water stream, completing the heat-pump cycle.