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3D CFD analysis of a twin screw expander for small scale ORC systems

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Abstract
Among a number of solutions to generate electricity from low temperature heat sources, the Organic Rankine Cycle (ORC) is the most widely used. In small scale ORC systems (below 300 kWe) with a low temperature heat source (from 55◦C till 150◦C), twin screw expanders are commonly used to recover the mechanical power. In this paper, 3D CFD (Computational Fluid Dynamics) calculations of a twin screw expander, with R245fa as a working fluid, are performed. The mesh motion is handled by an in-house code which generates a block-structured grid with the help of solutions of Laplace problems. Since the ideal gas equation of state shows big deviations in the ORC working conditions, the cubic Aungier Redlich-Kwong equation of state has been used because of its relative simplicity and low computational cost. The performance of the expander is evaluated for different pressure ratios and for two different designs. It is observed that the leakage flows have a significant effect on the screw expander’s efficiency. In order to evaluate the effects of individual clearance gaps on the performance of the expander, diagrams with the mass flow rate as a function of the rotation angle are provided.
Keywords
R245fa, Screw expander, ORC, Redlich-Kwong, real gas

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Chicago
Papeš, Iva, Joris Degroote, and Jan Vierendeels. 2014. “3D CFD Analysis of a Twin Screw Expander for Small Scale ORC Systems.” In Proceedings of the 11th World Congress on Computational Mechanics, 7207–7217.
APA
Papeš, I., Degroote, J., & Vierendeels, J. (2014). 3D CFD analysis of a twin screw expander for small scale ORC systems. Proceedings of the 11th World Congress on Computational Mechanics (pp. 7207–7217). Presented at the 11th World Congress on Computational Mechanics (WCCM XI - 2014).
Vancouver
1.
Papeš I, Degroote J, Vierendeels J. 3D CFD analysis of a twin screw expander for small scale ORC systems. Proceedings of the 11th World Congress on Computational Mechanics. 2014. p. 7207–17.
MLA
Papeš, Iva, Joris Degroote, and Jan Vierendeels. “3D CFD Analysis of a Twin Screw Expander for Small Scale ORC Systems.” Proceedings of the 11th World Congress on Computational Mechanics. 2014. 7207–7217. Print.
@inproceedings{5701087,
  abstract     = {Among a number of solutions to generate electricity from low temperature heat sources, the Organic Rankine Cycle (ORC) is the most widely used. In small scale ORC systems (below 300 kWe) with a low temperature heat source (from 55\unmatched{25e6}C till 150\unmatched{25e6}C), twin screw expanders are commonly used to recover the mechanical power. In this paper, 3D CFD (Computational Fluid Dynamics) calculations of a twin screw expander, with R245fa as a working fluid, are performed. The mesh motion is handled by an in-house code which generates a block-structured grid with the help of solutions of Laplace problems. Since the ideal gas equation of state shows big deviations in the ORC working conditions, the cubic Aungier Redlich-Kwong equation of state has been used because of its relative simplicity and low computational cost.
The performance of the expander is evaluated for different pressure ratios and for two different designs. It is observed that the leakage flows have a significant effect on the screw expander{\textquoteright}s efficiency. In order to evaluate the effects of individual clearance gaps on the performance of the expander, diagrams with the mass flow rate as a function of the rotation angle are provided.},
  author       = {Pape\v{s}, Iva and Degroote, Joris and Vierendeels, Jan},
  booktitle    = {Proceedings of the 11th World Congress on Computational Mechanics},
  isbn         = {9788494284472},
  keyword      = {R245fa,Screw expander,ORC,Redlich-Kwong,real gas},
  language     = {eng},
  location     = {Barcelona, Spain},
  pages        = {7207--7217},
  title        = {3D CFD analysis of a twin screw expander for small scale ORC systems},
  url          = {http://www.wccm-eccm-ecfd2014.org/frontal/Ebook.asp},
  year         = {2014},
}