Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions
We investigated the shear banding phenomena in the non-isothermal simple-shear flow of a viscoelastic-fluid-based nanofluid (VFBN) subject to exothermic reactions. The polymeric (viscoelastic) behavior of the VFBN was modeled via the Giesekus constitutive equation, with appropriate adjustments to in...
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MDPI AG
2022-02-01
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| Online Access: | https://www.mdpi.com/1996-1073/15/5/1719 |
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| author | Idrees Khan Tiri Chinyoka Andrew Gill |
| author_facet | Idrees Khan Tiri Chinyoka Andrew Gill |
| author_sort | Idrees Khan |
| collection | DOAJ |
| description | We investigated the shear banding phenomena in the non-isothermal simple-shear flow of a viscoelastic-fluid-based nanofluid (VFBN) subject to exothermic reactions. The polymeric (viscoelastic) behavior of the VFBN was modeled via the Giesekus constitutive equation, with appropriate adjustments to incorporate both the non-isothermal and nanoparticle effects. Nahme-type laws were employed to describe the temperature dependence of the VFBN viscosities and relaxation times. The Arrhenius theory was used for the modeling and incorporation of exothermic reactions. The VFBN was modeled as a single-phase homogeneous-mixture and, hence, the effects of the nanoparticles were based on the volume fraction parameter. Efficient numerical schemes based on semi-implicit finite-difference-methods were employed in MATLAB for the computational solution of the governing systems of partial differential equations. The fundamental fluid-dynamical and thermodynamical phenomena, such as shear banding, thermal runaway, and heat transfer rate (HTR) enhancement, were explored under relevant conditions. Important novel results of industrial significance were observed and demonstrated. Firstly, under shear banding conditions of the Giesekus-type VFBN model, we observed remarkable HTR and Therm-C enhancement in the VFBN as compared to, say, NFBN. Specifically, the results demonstrate that the VFBN are less susceptible to thermal runaway than are NFBN. Additionally, the results illustrate that the reduced susceptibility of the Giesekus-type VFBN to the thermal runaway phenomena is further enhanced under shear banding conditions, in particular when the nanofluid becomes increasingly polymeric. Increased polymer viscosity is used as the most direct proxy for measuring the increase in the polymeric nature of the fluid. |
| first_indexed | 2024-03-09T20:41:30Z |
| format | Article |
| id | doaj.art-121052ea3cd345719b2ae678272f0df9 |
| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-03-09T20:41:30Z |
| publishDate | 2022-02-01 |
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| series | Energies |
| spelling | doaj.art-121052ea3cd345719b2ae678272f0df92023-11-23T22:56:30ZengMDPI AGEnergies1996-10732022-02-01155171910.3390/en15051719Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic ReactionsIdrees Khan0Tiri Chinyoka1Andrew Gill2Department of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7701, South AfricaDepartment of Mathematics and Applied Mathematics, University of Cape Town, Cape Town 7701, South AfricaCentre for High Performance and Computing, Council for Scientific and Industrial Research, Cape Town 7700, South AfricaWe investigated the shear banding phenomena in the non-isothermal simple-shear flow of a viscoelastic-fluid-based nanofluid (VFBN) subject to exothermic reactions. The polymeric (viscoelastic) behavior of the VFBN was modeled via the Giesekus constitutive equation, with appropriate adjustments to incorporate both the non-isothermal and nanoparticle effects. Nahme-type laws were employed to describe the temperature dependence of the VFBN viscosities and relaxation times. The Arrhenius theory was used for the modeling and incorporation of exothermic reactions. The VFBN was modeled as a single-phase homogeneous-mixture and, hence, the effects of the nanoparticles were based on the volume fraction parameter. Efficient numerical schemes based on semi-implicit finite-difference-methods were employed in MATLAB for the computational solution of the governing systems of partial differential equations. The fundamental fluid-dynamical and thermodynamical phenomena, such as shear banding, thermal runaway, and heat transfer rate (HTR) enhancement, were explored under relevant conditions. Important novel results of industrial significance were observed and demonstrated. Firstly, under shear banding conditions of the Giesekus-type VFBN model, we observed remarkable HTR and Therm-C enhancement in the VFBN as compared to, say, NFBN. Specifically, the results demonstrate that the VFBN are less susceptible to thermal runaway than are NFBN. Additionally, the results illustrate that the reduced susceptibility of the Giesekus-type VFBN to the thermal runaway phenomena is further enhanced under shear banding conditions, in particular when the nanofluid becomes increasingly polymeric. Increased polymer viscosity is used as the most direct proxy for measuring the increase in the polymeric nature of the fluid.https://www.mdpi.com/1996-1073/15/5/1719finite-difference-methodsviscoelastic-fluid-based nanofluid (VFBN)non-isothermal viscoelastic fluid flowGiesekus modelnanofluid variable-thermal conductivityshear banding |
| spellingShingle | Idrees Khan Tiri Chinyoka Andrew Gill Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions Energies finite-difference-methods viscoelastic-fluid-based nanofluid (VFBN) non-isothermal viscoelastic fluid flow Giesekus model nanofluid variable-thermal conductivity shear banding |
| title | Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions |
| title_full | Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions |
| title_fullStr | Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions |
| title_full_unstemmed | Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions |
| title_short | Computational Analysis of Shear Banding in Simple Shear Flow of Viscoelastic Fluid-Based Nanofluids Subject to Exothermic Reactions |
| title_sort | computational analysis of shear banding in simple shear flow of viscoelastic fluid based nanofluids subject to exothermic reactions |
| topic | finite-difference-methods viscoelastic-fluid-based nanofluid (VFBN) non-isothermal viscoelastic fluid flow Giesekus model nanofluid variable-thermal conductivity shear banding |
| url | https://www.mdpi.com/1996-1073/15/5/1719 |
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