Research on the Mechanism of Delayed Expansion Process in a CO2 Two-phase Nozzle
In this paper, the motive nozzles of a CO2 ejector with a diverging angle ranging from small to large (0.076°, 0.306°, and 0.612°) were investigated. Coupled models for the homogeneous equilibrium (HEM), delayed equilibrium (DEM), and wall friction model were presented and compared with the experime...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | zho |
| Published: |
Journal of Refrigeration Magazines Agency Co., Ltd.
2020-01-01
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| Series: | Zhileng xuebao |
| Subjects: | |
| Online Access: | http://www.zhilengxuebao.com/thesisDetails#10.3969/j.issn.0253-4339.2020.01.056 |
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| Summary: | In this paper, the motive nozzles of a CO2 ejector with a diverging angle ranging from small to large (0.076°, 0.306°, and 0.612°) were investigated. Coupled models for the homogeneous equilibrium (HEM), delayed equilibrium (DEM), and wall friction model were presented and compared with the experimental data from related literature to analyze the dominant effects of the two flow mechanisms, non-equilibrium phase change, and wall friction on the delayed expansion process in the nozzle at corresponding angles. The results showed that within the ranges of this study, wall friction was the dominant mechanism of the delayed expansion process in the nozzle with a small diverging angle at the θ1 of 0.076°. Furthermore, the non-equilibrium phase change was the dominant mechanism in the nozzle with a middle diverging angle at the θ2 of 0.306°. In addition, the expansion process of the two-phase flow in the nozzle is close to the isentropic process for the large diverging angle at the θ1 of 0.612°. It is necessary for the design and optimization of the nozzle to choose a reliable model considering the dominant mechanism. When the diverging angle is small, the simulation results of the DEM coupled with a friction model indicated that the flow could choke the downstream of the minimum-area throat; this is verified by our experimental results. In addition, the critical mass flow rate predicted by the above model was lower than those of the HEM and DEM. The critical mass flow rates predicted by the three models indicated a barely noticeable difference for the larger diverging angle |
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| ISSN: | 0253-4339 |