Computation of metallic nanofluid natural convection in a two-dimensional solar enclosure with radiative heat transfer, aspect ratio and volume fraction effects

Kuharat, S; Beg, OA; Kadir, A; Vasu, B

Abstract

As a model of nanofluid direct absorber solar collectors (nano-DASCs), the present article describes
recent numerical simulations of steady-state nanofluid natural convection in a two-dimensional
enclosure. Incompressible laminar Newtonian viscous flow is considered with radiative heat transfer.
The ANSYS FLUENT finite volume code (version 19.1) is employed. The enclosure has two adiabatic
walls, one hot (solar receiving) and one colder wall. The Tiwari-Das volume fraction nanofluid model
is used and three different nanoparticles are studied (Copper (Cu), Silver (Ag) and Titanium Oxide
(TiO2)) with water as the base fluid. The solar radiative heat transfer is simulated with the P1 flux and
Rosseland diffusion models. The influence of geometrical aspect ratio and solid volume fraction for
nanofluids is also studied and a wider range is considered than in other studies. Mesh-independence
tests are conducted. Validation with published studies from the literature is included for the copperwater nanofluid case. The P1 model is shown to more accurately predict the actual influence of solar
radiative flux on thermal fluid behaviour compared with Rosseland radiative model. With increasing
Rayleigh number (natural convection i.e. buoyancy effect), significant modification in the thermal flow
characteristics is induced with emergence of a dual structure to the circulation. With increasing aspect
ratio (wider base relative to height of the solar collector geometry) there is a greater thermal convection
pattern around the whole geometry, higher temperatures and the elimination of the cold upper zone
associated with lower aspect ratio. Titanium Oxide nano-particles achieve slightly higher Nusselt
number at the hot wall compared with Silver nano-particles. Thermal performance can be optimized
with careful selection of aspect ratio and nano-particles and this is very beneficial to solar collector
designers.

Citation

Kuharat, S., Beg, O., Kadir, A., & Vasu, B. (2020). Computation of metallic nanofluid natural convection in a two-dimensional solar enclosure with radiative heat transfer, aspect ratio and volume fraction effects. Arabian Journal for Science and Engineering, 45, 9075-9093. https://doi.org/10.1007/s13369-020-04678-1

• Journal Article Type: Article
• Acceptance Date: May 29, 2020
• Online Publication Date: Jun 10, 2020
• Publication Date: Nov 1, 2020
• Deposit Date: May 27, 2020
• Publicly Available Date: Jun 10, 2021
• Journal: Arabian Journal for Science and Engineering
• Publisher: Springer Verlag
• Volume: 45
• Pages: 9075-9093
• DOI: https://doi.org/10.1007/s13369-020-04678-1
• Publisher URL: https://doi.org/10.1007/s13369-020-04678-1
• Related Public URLs: http://link.springer.com/journal/13369