Conjugated heat transfer and entropy generation of Al2O3–water nanofluid flows over a heated wall-mounted obstacle
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The present study reports numerical simulations of water-based Al2O3 nanofluid flowing in a 2D channel with a heated wall-mounted obstacle. The conjugated heat transfer problem including forced convection within the fluid and conduction inside the obstacle is numerically solved using the mixture model with temperature-dependent properties. The model has been first carefully validated against published data. Then, the fluid flow and heat transfer have been investigated for six nanoparticle volume fractions \(\varphi\) up to \(1.8\%\) and bulk Reynolds numbers within the range \(100 \le Re \le 1600\). The results show that only the Reynolds number has an influence on the hydrodynamic field, especially on the reattachment length behind the obstacle. The heat transfer rate increases with increasing nanoparticle concentrations and/or Reynolds number. The second law analysis is employed to study the heat transfer and fluid friction irreversibilities. The average entropy generation increases linearly with the Reynolds number. Increasing the nanoparticle volume fraction reduces the thermal entropy generation while the frictional one increases. Finally, the benefit of using this nanofluid is discussed regarding five merit criteria.
KeywordsNanofluid Conjugated heat transfer Laminar channel flow Heated obstacle Entropy generation Numerical simulation
The authors would like to thank the NSERC chair on industrial energy efficiency established at Université de Sherbrooke in 2014 and supported by Hydro-Québec, Natural Resources Canada (CanmetEnergy in Varennes) and Rio Tinto Alcan. Calculations have been done using the supercomputer Mammouth Parallèle 2 of Compute Canada’s network, which is also here gratefully acknowledged.
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