Advanced Numerical and Thermodynamic Modeling of CO2 Ejectors for their Integration in Refrigeration Systems by Antoine METSUE

In light of new environmental regulations restricting the use of traditional refrigerants, carbon dioxide (CO₂) is emerging as an environmentally-friendly alternative. However, traditional CO₂ refrigeration systems cannot match the performance of those using synthetic refrigerants. Ejectors are passive entrainment and compression devices that have attracted particular attention in this field, where they are used as passive compressors, and can thus palliate the poor performance of conventional CO2 systems. However, the design of these ejectors and the control of ejector cycles remain difficult, due to a still limited understanding of the internal physics of the flows and transfers. In particular, the flow is two-phase and flashing occurs in the primary nozzle, and depending on operating conditions, the metastable phase may also appear. Experimental installations are scarce, so the numerical modeling of these devices is a powerful tool for studying their internal physics and their operation within the cycle.

First, this research focuses on thermodynamic modeling to study the operation of the ejector within the cycle, and to determine the optimal performance and operating regime of the device. CFD tools allowing the two-phase and metastable features of the flow to be taken into account are then implemented.

Finally, the tools are combined in a multi-scale approach, enabling an in-depth study of the ejector integrated into the system in which it operates. The links between the performance of the ejector and the performance of the whole cycle are highlighted, as well as the impact of metastability, at both scales.

Jury members :

• Prof. Yann Bartosiewicz (UCLouvain, Belgium), supervisor
• Prof. Sébastien Poncelet (Université de Sherbrooke, Canada), supervisor
• Prof. Paul Fisette (UCLouvain, Belgium), chairperson
• Dr. Matthieu Duponcheel (UCLouvain, Belgium)
• Prof. Eckhard Groll (Purdue University, USA)
• Prof. Stéphane Moreau (Université de Sherbrooke, Canada)
• Dr. Hakim Nesreddine (Hydro-Québec, Canada)

Visio conference link : https://teams.microsoft.com/l/meetup-join/19%3ameeting_NTMxYjkyZmYtNjVmYy00ZDgwLWJkYTItNTZhM2U3YzI4Mjkz%40thread.v2/0?context=%7b%22Tid%22%3a%223a5a8744-5935-45f9-9423-b32c3a5de082%22%2c%22Oid%22%3a%220bc785a4-3e63-48ff-b718-0c7b8322eff6%22%7d  Meeting ID: 254 468 468 49  -  Passcode: qXwZWv