Five Flooded Ammonia Heat Pumps in Series – Prevessin

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. Ammonia (R717) is a natural refrigerant with excellent thermodynamic properties and is widely used in large industrial refrigeration and heat-pump systems. This advanced example demonstrates five flooded ammonia heat-pump cycles connected in series. Each cycle contains its own compressor, heat exchanger, expansion valve, flash separator, and flooded evaporator. The water streams pass successively through the five heat-pump stages, allowing the heating and cooling duties to be distributed across several temperature levels rather than handled by a single cycle. In each flooded evaporator, excess liquid ammonia keeps the heat-transfer surface well wetted while the flash separator separates vapor from the remaining liquid. The arrangement illustrates how several heat-pump modules can be combined to achieve a large overall temperature lift while maintaining favorable operating conditions in each individual cycle.