Investigation of Heat Transfer of Non-Newtonian Pseudo-Plastic Fluids in Porous Heat Exchangers

Document Type : Research Article

Authors

1 Mechanical Engineering Department, Faculty of Engineering, Shahid Chamran of Ahvaz University, Ahvaz, IRAN

2 Mechanical Engineering Department, Faculty of Engineering, Shahid Chamran of Ahvaz University, Ahvaz, Iran

3 Assistant professor, Department of Mechanical Engineering, Dezful Branch, Islamic Azad University, Dezful, Iran

Abstract

In this paper, the natural heat transfer of Rayleigh-Benard's non-Newtonian Pseudo-Plastics fluid in a tube heat exchanger with its left wall lined with a porous layer of a thickness l is considered numerically for an unstable state of laminar. The lower wall of the heat exchanger is at constant temperature Thand the upper wall at Tc temperature (Th>Tc). The walls are left and right insulated. The dimensionless governing equations are solved by the finite element method and the accuracy of the results is compared with previous studies. The results show that, in a large Rayleigh number, the average Nusselt number increases due to the fact that the natural heat transfer is more than conduction heat transfer. Also, in small Darcy numbers, the flow permeability is very low which causes reduce natural heat transfer convection. The results show that by decreasing the Power-law index, the non-dimensional temperature is reduced and the lowest non-dimensional temperature is obtained for the lowest Power-law index. On the other hand, with the increase of the Power-law index in a constant Rayleigh number and the passage of time, the increase of natural heat transfer occurs in the tube. Also, the Rayleigh number decreases with the increase of the Power-law index to start the natural convection in the heat exchanger.

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References

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Amirkabir Journal of Mechanical Engineering
Volume 53, Issue 1
April 2021
Pages 241-258

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