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Investigation and Numerical Simulation of Two-Phase Ejectors for Use in the Water Desalination Cycle

Ahmadiani, Maryam | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 57718 (58)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Shafiei, Mohammad Behshad; Sani, Mahdi
  7. Abstract:
  8. Energy efficiency in desalination systems is primarily hindered by high-energy-consuming equipment, such as compressors. This study explores a novel cycle of combined ejector desalination involving a two-phase state and a solar vacuum tube collector designed to generate saturated steam at a lower temperature. The mechanism involves water entering the ejector's primary nozzle in the liquid phase, pulling steam generated by the collector at a reduced pressure and temperature. This process facilitates the separation of desalinated water from saltwater, resulting in purified water in a variable phase. The performance of the ejector was thoroughly evaluated, including how primary and secondary inlet pressures influence the entrainment ratio and their impact on the fluid's hydrodynamic characteristics, such as velocity, temperature, quality of saturated steam and liquid, and flow rate. These evaluations were conducted using Fluent software's computational fluid dynamics (CFD). Furthermore, the proposed cycle was modeled transiently over a year in Tehran using TRNSYS software. The investigation covered secondary inlet pressures ranging from 7000 Pa to 39000 Pa and primary nozzle pressures between 2 bar to 5 bar, studying their impact on fluid behavior. The findings suggest that, at a constant primary nozzle pressure, an increase in secondary nozzle pressure can enhance the flow rate of saturated steam in the secondary nozzle by 77 % and augment the inlet velocity of the secondary nozzle by 60 %. Additionally, under constant conditions and in Tehran's context, the peak output rate is 1.35 kg/m² per hour, the maximum daily yield is 8.47 kg/m², and the total annual output is 767 kg/m²
  9. Keywords:
  10. Numerical Simulation ; Ejector ; Entrainment Rate ; Reverse Flow ; TRNSYS Software ; Evacuated Tube Collector ; Combined Desalinator

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