Impacts of Non-Uniform Border Temperature Variations on Time-Dependent Nanofluid Free Convection within a Trapezium: Buongiorno’s Nanofluid Model

Revnic Revnic,Ghalambaz Ghalambaz,Pop Pop,Sheremet Sheremet,Groşan Groşan

doi:10.3390/en12081461

Abstract

The present study develops the influence of inclined border temperature variations on the isotherms, streamlines, and isoconcentrations for unsteady free convection in a trapezoidal region filled with the water-based nanofluid. The considered mathematical nanofluid approach was formulated based on the Buongiorno’s model. The set of governing partial differential equations formulated using non-dimensional primitive variables such as velocity, pressure, temperature, and nanoparticles concentration volume fraction was solved numerically using the finite element method for various magnitudes of control characteristics. It was revealed that control characteristics affected the liquid circulation and energy transport coefficients. The Nusselt number is a growing function of wave number, amplitude, and the Rayleigh number.

Highlights

Thermogravitational convective energy transfer is a very significant transport mechanism in technical and natural systems owing to its wide applications in solar collectors, heat exchangers, chemical reactors, and building heating [1,2,3]
Nusselt number main results were: to a maximum value and became stationary, but its values had a small increase in respect of wave number
The present study studied the circulation as well as thermal and mass transmission of a nanofluid within a trapezoidal enclosure subject to a non-uniform hot border temperature

Summary

Introduction

Thermogravitational convective energy transfer is a very significant transport mechanism in technical and natural systems owing to its wide applications in solar collectors, heat exchangers, chemical reactors, and building heating [1,2,3]. It seems that the natural convection within a tilted trapezoidal enclosure filled with a viscous liquid was first studied by Lee [4]. The paper concludes that the average Nu varied sinusoidally with a growth of the wave parameter and obtained a maximum magnitude for a wide range of temperature differences 103 ≤ Ra ≤ 106.

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