The benefit of droplet injection on the performance of an ejector refrigeration cycle working with R245fa


Power demand has proportionally increased with surging global population. This has put significant strain on existing energy systems and calls for higher efficiency as the search for alternative sources continues. In the cooling industry, high power usage can be cut down via the use of Heat Driven Ejector Refrigeration Systems (HDRS). The main advantage of these cycles is their capacity to be activated using low-grade energy sources such as solar power or waste heat as primary input. Particularly, HDRS are known for their reduced maintenance requirements, fewer moving parts, lower operating costs and minimal electricity consumption. However, HDRS do suffer from one main drawback; their relative low performance. Typical coefficient of performance (COP) values for a HDRS using either R134a or R245fa lie indeed in the range [0.1–0.5]. Integrating an ejector in a HDRS can lead to COP improvement by up to 40%. In the past, researchers have employed thermodynamic models based on perfect gas behavior credit to their simplicity and generally good experimental agreement. Moreover, attempts have been made to enhance ejector performance by droplet injection inside the ejector, although mixed results have been reported.

On this account, researchers from the University of Constantine: Mehdi Bencharif (PhD candidate) and Professor Said Zid, in collaboration with Dr. Hakim Nesreddine at Hydro-Québec, Dr. Sergio Croquer Perez and Professor Sébastien Poncet at Université de Sherbrooke, proposed to use droplet injection to enhance the performance of HDRS but with a different approach: to inject the droplets in between the ejector and the condenser. Technically, their idea was to avoid flow perturbations in the ejector and to reduce the condenser inlet temperature, while at the same time maintaining a relatively simple cycle configuration. Their work is currently published in the research journal, International Journal of Refrigeration.

In their approach, the researchers explored their hypothesis using a combined experimental and thermodynamic modelling analysis on the effects of droplet injection on the performance of an ejector-based HDRS working with R245fa. Thermodynamic models were developed within MATLAB for each component of the cycle. The developed models were then validated against experimental data of an R245fa test rig installed at Hydro-Québec’s Energy Technologies Laboratory (LTE).

The authors reported that the numerical models agreed fairly well with the experiments. In fact, the results demonstrated that injecting R245fa droplets at the end of the ejector diffuser with different glycol temperatures ranging from 20 to 26 °C had a significant impact on the performance of the ejector itself and more interestingly, on the performance of the whole cycle.

In summary, the study presented the use of a combined numerical and experimental approach to study the influence of droplet injection on the performance of an ejector-based refrigeration cycle working with R245fa. The ejector was modelled by solving the conservation equations across each section of the device. Remarkably, the model was reported to predict quite well the temperature profile and heat capacity along the heat exchanger. In a statement to Advances in Engineering, Professor Sébastien Poncet highlighted that based on their work, droplet injection between the ejector and the condenser might be a simple and feasible alternative for increasing the heat driven ERS performance.

The benefit of droplet injection on the performance of an ejector refrigeration cycle working with R245fa - Advances in Engineering

About the author

Mehdi Bencharif is a Ph.D. Candidate at Laboratoire de Génie Climatique Constantine (LGCC) of University frères Mentouri Constantine 1 and visiting PhD at the Mechanical Engineering Department of Université de Sherbrooke. His researches focus on the modeling and optimization of ejector refrigeration cycles, refrigeration and air conditioning systems, energy and environment and artificial intelligence.

He obtained his Master of Science degree at the University of Constantine 1 in Algeria in 2014, and was a lecturer at the civil engineering department of University frères Mentouri Constantine 1 between 2015 and 2017.

Laboratoire de Genie Climatique Constantine(LGCC) :

About the author

Sergio Croquer is a Postdoctoral Researcher at the Laboratoire de Mécanique des Fluides, Thermique et Énergétique of Université de Sherbrooke, where he finished his Ph.D. on the numerical modelling of supersonic ejectors for alternative refrigeration cycles in 2018.

His research is focused on the use of computational fluid dynamics for the optimization of energy systems and structures, with specific applications in wave-structure interactions, supersonic ejectors, refrigeration cycles and turbomachinery. He obtained his Master of Science degree in Universidad Simón Bolívar, Venezuela in 2011 and was lecturer at the Mechanical Energy Department of this University between 2012 and 2013.

Laboratoire de Mécanique des Fluides, Thermique et Énergétique de l’Université de Sherbrooke
ResearchGate, Scopus

About the author

Hakim Nesreddine is a holder of a BSc in climate control engineering, an MSc and a Ph.D in mechanical engineering. He also earned a Master of Business administration (MBA) in project management. He worked as a maintenance engineer in textile industry at the beginning of his career before joining Hydro-Quebec as a research scientist at IREQ. Over the course of his 23 years working in a major electricity company, he has acquired a vast experience in energy activities and business. During the last decade, Dr. Nesreddine led multidisciplinary teams for co-development of cutting-edge technology and application in partnership with leading companies. His research interests include distributed power generation, waste heat recovery, energy conversion and advanced refrigeration. He co-authored many scientific papers with academia and he is frequently invited as a plenary speaker in international conferences.

Dr. Nesreddine sits on steering Committees of Canada Green Building Council and NSERC Chair on energy efficiency in industry. In addition, he serves on technical committees and working groups of the Canadian Standard Association (CSA). He is a member of ASME International Gas Turbine Institute IGTI- ORC Power Systems and Consortium for Energy Efficiency (CEE).

About the author

Sébastien Poncet received his engineering diploma and his master degree in physical oceanography from Seatech (Toulon, France) in 2002 and the Ph.D. degree in complex systems from Aix-Marseille University (Marseille, France) in 2005, for a thesis on turbulent rotor-stator interdisk flows (two national awards). He was then assistant lecturer for one year before getting a position of assistant professor at Aix-Marseille University in 2006. He joined the University of Sherbrooke as an Associate Professor of Mechanical Engineering in 2014, where he currently is the chairholder of the NSERC/Hydro-Québec/Natural Resources Canada/Emerson Industrial Research Chair in Industrial Energy Efficiency. He is now full professor in the mechanical engineering department and the director of LMFTEUS lab.

His research interests include the experimental characterization of the thermophysical properties of complex heat transfer fluids (nanofluids, slurries, PCMs) and the advanced numerical modelings of thermal systems (supersonic ejector, vortex tube, magnetocaloric refrigeration, heat exchanger, turbomachineries…). He is the coauthor of about 250 research papers whose more 100 in international journals.

Laboratoire de Mécanique des Fluides, Thermique et Énergétique de l’Université de Sherbrooke
ResearchGate, Google Scholar

About the author

Said Zid is a full professor at the university frères Mentouri Constantine 1, where he holds the position of researcher professor for more than 30 years. He is also the director of Laboratoire de Genie Climatique Constantine (LGCC) since 2005; he finished his Ph.D. on the Energy system and renewable energy in Bucharest Romania 1985. He is the team leader of a research team composed of doctoral students.

His research interests are focused on refrigeration cycles, food science, heat pump, energy conversion and advanced refrigeration, renewable energy. Professor Zid participates in several seminars and conferences on the national and international scale. He was the chairman of the organizing committee of the first and second International Seminar on Climate Engineering and Energy (SIGCLE’2010) and (SIGCLE’2015).

Laboratoire Genie Climatique Constantine LGCC
Universite frere Mentouri Constantine 1 


Mehdi Bencharif, Hakim Nesreddine, Sergio Croquer Perez, Sébastien Poncet, Said Zid. The benefit of droplet injection on the performance of an ejector refrigeration cycle working with R245fa. International Journal of Refrigeration, volume 113 (2020) page 276–287.

Go To International Journal of Refrigeration

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