Experimental analysis of an operational 10 kW ammonia-water absorption heat transformer

The decarbonization of industrial processes is crucial to reduce significantly greenhouse gases emissions. A large share of industries requires heat at temperature above 100°C and emits waste heat while operating. Thermodynamic cycles such as NH 3 -H 2 O absorption heat transformers (AHT) have the potential to upgrade waste heat. This paper introduces an operational 10 kW NH 3 -H 2 O AHT producing heat at temperatures above 100°C from 80°C waste heat. The prototype was built using plate heat exchangers to be easily scalable for further industrial requirements. Optimal operating conditions, heat transfer fluid (HTF) inlet temperatures of 15°C and 90°C at the condenser and absorber respectively, resulted in a COP elec close to 30. An experimental study was carried out to test the variations of operational parameters, including the heat exchangers HTF temperatures and mass flow rates. The most striking result emerging from the experimental analysis is that the flow rate ratio of poor solution over refrigerant has an optimal value allowing for reaching maximum thermodynamic performances. However, the hydrodynamics of the system driven by the prototype design and the charge of fluid are limiting to reach the optimal operational ratio. Together these results provide important insights to improve the performances of NH 3 -H 2 O AHT and perspectives to move toward their implementation in industries. • Operational 10 kW NH 3 -H 2 O absorption heat transformer able to generate heat > 100°C from 80°C waste heat with a COP elec ~ 30. • Experimental characterization and data analyses allowed for identifying the optimal operating conditions: inlet heat transfer fluid temperature < 20°C at the condenser and of 90°C at the absorber. The flow rate ratio of poor solution to refrigerant has an optimal value experimentally verified of 4.5 for which performances peak. • The operating conditions, including the fluid charge and heat exchangers temperatures, influences the hydrodynamics of the system, which drive the performances and can be improved through prototype design considerations.