Performance improvement of NH3–H2O absorption chiller with a combined generator

•A combined generator including a double function of ammonia vapor generation and purification is developed and integrated in an NH3-H2O absorption chiller.•The impact of operating parameters at the inlet of the combined generator is investigated.•A design of experiments is defined to determine the effects of operation conditions on the combined generator performances.•The impact of the solution mass flowrate and the heating temperature on the machine performance is investigated. The present experimental work investigates the impact of an innovative falling-film and plate combined generator, associating vapor production and purification, on the performance of an NH3–H2O absorption chiller of 5-kW cooling capacity. The impact of the flooding of the lower part of the exchanger on the performance of the machine is investigated: It decreases the COP by 33% and cooling capacity by 38%. Solution sub-cooling at the combined generator inlet improves the purity of the ammonia vapor produced, but degrades the performance of the chiller. A design of experiments is defined to characterize the performance of the combined generator, which is highly impacted by the solution mass flowrate and concentration. Then, two correlation forms are used to predict the performance, and the adapted NTU model yields better results. Finally, for an air-conditioning application, a low solution mass flowrate allows the energy consumption to be reduced by approximately 15% but it requires a higher temperature for the heat source; while the increase in the solution mass flowrate degrades the performance but enables the machine to self-regulate at a low heat source.