Entropy generation calculation for laminar fully developed forced flow and heat transfer of nanofluids inside annuli

Document Type : Full Length Research Article

Author

Faculty of mechanical engineering, Semnan University, Semnan, Iran

Abstract

In this paper, second law analysis for calculations of the entropy generation due to the flow and
heat transfer of water-Al2O3 and ethylene glycol-Al2O3 nanofluids inside annuli is presented. The
physical properties of the nanofluids are calculated using empirical correlations. Constant heat
fluxes at inner surface of the annuli are considered and fully developed condition for fluid flow
and heat transfer is assumed. The control volume approach is selected for calculation of the
entropy generation. Total entropy generation for different values of the nanoparticles volume
fractions at different geometrical ratios is obtained and compared with those of the base fluid.
Also, the geometrical ratios at which the minimum entropy generation is achieved are presented.
The results show that when the ratio of the annuli length to its hydraulic diameter (L/Dh) exceeds
some critical values, adding of the nanoparticles is not efficient. For each value of the
nanoparticles concentration, there is a length ratio (L/Dh) at which the entropy generation is
minimized.

Keywords

References

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History

  • Receive Date: 03 June 2013
  • Revise Date: 07 September 2013
  • Accept Date: 07 September 2013

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