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Performance Improvement of Hybrid Ejector-Vapor Compression Refrigeration Cycle

Beyarami, Javid | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52923 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Hakkaki-Fard, Ali
  7. Abstract:
  8. The annual increase in electricity consumption has led to several problems, including greenhouse gas emissions and global warming. Refrigeration systems are one of the main electricity consumers in the world. Ejector refrigeration systems use waste heat from industries or renewable sources such as solar energy to create the cooling effect. One of the main problems with these systems is the inefficiency of the cycle by the change of the ambient conditions including temperature rise. In ejector vapor compression refrigeration cycles, the compressor increases the pressure to an intermediate pressure. and the rest of the pressure increase is provided by the ejector. These systems can provide the required cooling power at much wider temperature conditions. In the present study, the ejector vapor compression refrigeration cycle is modeled thermodynamically and the modeling of the ejector inside the cycle performed through computational fluid dynamics. Numerical modeling of the ejector will increase the accuracy of simulations. First, the conjugate effect of primary flow pressure and geometric parameters on cycle performance is investigated. It is demonstrated that the cycle optimization using geometric parameters and primary flow pressure can lead to a 73 percent improvement in coefficient of performance. Then, the ejector vapor compression cycle is designed and the optimal intermediate pressure between the compressor and the ejector is determined. According to the obtained results the cycle designed with the proposed method increases the performance coefficient of the compression refrigeration cycle by 47.5 percent. Another problem with ejector refrigeration systems is their dependance on the generator heat. This problem is more severe in solar ejector systems. In this study, an ejector vapor compression refrigeration cycle with two ejectors is provided. This cycle can provide a constant amount of refrigeration even of the provided heat is reduced up to 42%
  9. Keywords:
  10. Supersonic Ejector ; Vapor Compression ; Performance Improvement ; Computational Fluid Dynamics (CFD) ; Refrigeration

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