Abstract
The present investigation addressed the entropy generation, fluid flow, and heat transfer regarding Cu-Al 2 O 3 -water hybrid nanofluids into a complex shape enclosure containing a hot-half partition were addressed. The sidewalls of the enclosure are made of wavy walls including cold isothermal temperature while the upper and lower surfaces remain insulated. The governing equations toward conservation of mass, momentum, and energy were introduced into the form of partial differential equations. The second law of thermodynamic was written for the friction and thermal entropy productions as a function of velocity and temperatures. The governing equations occurred molded into a non-dimensional pattern and explained through the finite element method. Outcomes were investigated for Cu-water, Al 2 O 3 -water, and Cu-Al 2 O 3 -water nanofluids to address the effect of using composite nanoparticles toward the flow and temperature patterns and entropy generation. Findings show that using hybrid nanofluid improves the Nusselt number compared to simple nanofluids. In the case of low Rayleigh numbers, such enhancement is more evident. Changing the geometrical aspects of the cavity induces different effects toward the entropy generation and Bejan number. Generally, the global entropy generation for Cu-Al 2 O 3 -water hybrid nanofluid takes places between the entropy generation values regarding Cu-water and Al 2 O 3 -water nanofluids.
Highlights
The investigation concerning convective heat transfer in enclosures and close cavities is an important issue that has enormous variety regarding purposes toward engineering and industry equipment, including heat exchangers [1], HVAC [2], cooling of electronic devices [3], and renewableEnergies 2020, 13, 2942; doi:10.3390/en13112942 www.mdpi.com/journal/energiesEnergies 2020, 13, 2942 energies [4]
The results indicate that the change of the geometrical aspect of the cavity can notably change the portion of entropy generation in solid plus liquid regions
The values of local and average Nusselt numbers are determined toward several values Ri and R
Summary
Energies 2020, 13, 2942 energies [4] In these applications, the selection of the heat transfer liquid is a crucial step to ensure an optimal heat transfer. The selection of the heat transfer liquid is a crucial step to ensure an optimal heat transfer In this regard, the use of pure liquids, such as water and oil, has shown an obstacle due to their low thermal conductivity. The use of pure liquids, such as water and oil, has shown an obstacle due to their low thermal conductivity To overcome this disadvantage, nanoparticles (less than 100 nm in diameter) of materials with high thermal conductivity are combined with the carrier fluid to change its thermal properties and enhance heat transfer [5].
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