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A Non Symmetric Interfacial Area Density Formulation for Transcritical CO2 Ejectors CFD Modeling

Abstract : The reduction of global warming potential gases emissions in industrial refrigeration devices requires the development of efficient cycles using low GWP gases. The supercritical C02 cycle assisted by a transcritical two phase ejector is a nice example of such cycles. The design of such ejectors is not obvious and an intense development of performance prediction tools is observed in literature especially regarding two-phase CFD modeling. The two phase flow CFD models are limited today by their lack of flexibility and difficulties to empirically calibrate them. The main drawback of classical Hertz-Knudsen or HRM phase change models is their difficulty to simultaneously predict the mass flow rate and the outlet velocity of the primary flow of the ejector. These two parameters are responsible of the entrainment ratio an ejector at given operating conditions and geometry. This paper presents a thermal phase change model that introduces a non symmetric interfacial area density formulation for two-phase liquid-gas CO 2 ejectors. This formulation describes the gas-liquid interface as bubbles at low void fractions and as droplets at high void fractions. The model results are compared to experimental results of literature. It appeared that bubbles number density affects mainly the primary flow rate and the droplets number density affects the outlet velocity of the primary nozzle and thus the mixture pressure and the secondary flow rate.
Keywords : Ejector two-phase CO2
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Conference papers
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https://hal-mines-paristech.archives-ouvertes.fr/hal-03238075
Contributor : Egoi Ortego Sampedro <>
Submitted on : Wednesday, May 26, 2021 - 10:46:26 PM
Last modification on : Tuesday, July 13, 2021 - 3:09:32 AM
Long-term archiving on: : Friday, August 27, 2021 - 9:03:40 PM

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Egoi Ortego Sampedro. A Non Symmetric Interfacial Area Density Formulation for Transcritical CO2 Ejectors CFD Modeling. 18th International Refrigeration and Air Conditioning Conference at Purdue, May 2021, Purdue, United States. ⟨hal-03238075⟩

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