Computation of thermo-solutal convection with Soret-Dufour cross diffusion in a vertical duct containing carbon/metallic nanofluids

Umavathi, JC; Beg, OA

Abstract

Duct flows constitute an important category of modern thermal engineering. Optimizing efficiency has
become a significant objective in the 21st century in, for example, heating ventilation and air-conditioning
(HVAC), coolant or heat transfer fluid flows in a nuclear power reactor, heat exchanger design etc, and this
has been achieved by either new materials (improved thermal insulation properties) constituting the duct
walls, novel geometric designs or improved working fluids. Nanotechnology has infiltrated into duct design
in parallel with many other fields of mechanical, medical and energy engineering. Motivated by the
excellent potential of nanofluids, a subset of materials engineered at the nanoscale, in the present work, a
new mathematical model is developed for natural convection in a rectangular vertical duct containing
nanofluid. The left and right walls of the duct are maintained at constant and unequal temperatures, while
the front and rear walls of the duct are insulated. Thermo-solutal (double-diffusive) natural convection of
aqueous nanofluid containing various metallic nanoparticles (e. g. copper, titanium oxide) or carbon-based
nanoparticles (e. g. diamond, silicon oxide) is simulated. The Tiwari-Das nanoscale volume fraction model
is used in addition to the Brinkman and Maxwell models for defining the properties of the nanofluid. The
partial differential conservation equations for mass, momentum and energy are non-dimensionalized via
appropriate transformations and the resulting boundary value problem is solved with a second-order
accurate implicit finite difference technique employing Southwell-Over-Relaxation (SOR). Mesh
independence tests are conducted. Extensive visualization of the solutions for velocity, temperature,
nanoparticle concentration (volume fraction) are presented for five different nanoparticles (silicon oxide,
diamond, copper, titanium oxide and silver), thermal Grashof number, nanoparticle species (solutal)
Grashof number, volume fraction of nanoparticles (i.e. percentage doping), Dufour number, Soret number,
Prandtl number, Schmidt number and duct aspect ratio. It is observed that the heat transfer rate (Nusselt
number) at both the walls is maximized for diamond nanoparticles and minimized for silicon oxide
nanoparticles. Further the heat transfer rate for clear fluid is lower when compared with nanofluid,
confirming that nanoparticles achieve the desired thermal enhancement at the boundaries also. The mass
transfer at both walls (Sherwood number) however is not significantly influenced by any particular type of
nanoparticle, thermal and concentration Grashof number and is depleted with higher values of Dufour,
Prandtl, Soret and Schmidt numbers in addition to aspect ratio. However, Sherwood numbers at both the
left and right duct walls are substantially boosted with greater solid volume fraction of nanoparticles.

Citation

Umavathi, J., & Beg, O. (2022). Computation of thermo-solutal convection with Soret-Dufour cross diffusion in a vertical duct containing carbon/metallic nanofluids. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 236(13), 7456-7472. https://doi.org/10.1177/09544062211072693

• Journal Article Type: Article
• Acceptance Date: Jan 4, 2022
• Online Publication Date: Jan 27, 2022
• Publication Date: Jan 27, 2022
• Deposit Date: Feb 4, 2022
• Publicly Available Date: Feb 4, 2022
• Journal: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science
• Print ISSN: 0954-4062
• Electronic ISSN: 2041-2983
• Publisher: SAGE Publications
• Volume: 236
• Issue: 13
• Pages: 7456-7472
• DOI: https://doi.org/10.1177/09544062211072693
• Publisher URL: https://doi.org/10.1177/09544062211072693
• Related Public URLs: http://www.uk.sagepub.com/journals/Journal202017
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