A numerical study of the effect of the magnetic field on turbulent fluid flow, heat transfer and entropy generation of h
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THE EUROPEAN PHYSICAL JOURNAL PLUS
Regular Article
A numerical study of the effect of the magnetic field on turbulent fluid flow, heat transfer and entropy generation of hybrid nanofluid in a trapezoidal enclosure Alireza Aghaeia , Hossein Khorasanizadeh, and Ghanbar Ali Sheikhzadeh Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran Received: 24 November 2018 / Revised: 11 March 2019 Published online: 28 June 2019 c Societ` a Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2019 Abstract. The purpose of this research is the numerical study of turbulent flow field, heat transfer and entropy generation of a Cuo-MWCNT-oil hybrid nanofluid in a trapezoidal enclosure under the influence of a magnetic field in natural convection. The enclosure side walls are insulated, the top wall is cold and the bottom one is hot. The study is done on Rayleigh numbers 107 to 1010 , Hartmann numbers 0 to 500, and volume fractions 0 to 1 percent of nanoparticles. The governing equations were solved numerically using a finite volume method and SIMPLER algorithm. According to numerical results, it was observed that the application and increase of a magnetic field increases the flow tendency to vortices. In all Rayleigh numbers and for all the studied Hartmann numbers, the stream function and average Nusselt number reduced by increasing the volume fraction of nanoparticles. It was also observed that for smaller Rayleigh numbers, increasing the Hartmann number will have a more tangible effect on reducing the average Nusselt number. By increasing the Rayleigh number in all the studied Hartmann numbers and volume fractions, the total entropy generated increased. The optimal mode for each Rayleigh number in terms of the minimum value of entropy generation is the least volume fraction and the most Hartmann number.
1 Introduction The heat transfer of natural convection in enclosure has always attracted attention due to its widespread use in engineering. Ventilation systems in buildings, electronic equipment cooling, food industry, double glazed windows, solar collectors and so on are samples of applications of the heat transfer process. Trapezoidal channels are used in metal smelting industries (production of copper wires) and production of some kind of heat exchangers. Turbulence modeling despite the progress of recent decades is still difficult. So far, many turbulence models have been provided, each of which is valid and accurate for specific flow regimes and even in a specific region of the flow field. There is no turbulence model that can be used for all engineering issues. Choosing a model from among existing models depends on a variety of things including geometry, boundary conditions, flow type, existing computational capabilities, and more. Various studies have been done on the turbulent flow of nanofluids. It should be noted that dispersion in the presented studies is related to the turbulent flow in terms of subject, geometry, and others. The dispersion is caused by a variety of studies on turbulent flow in ter
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