Three-dimensional modelling of natural convection and entropy generation in a vertical cylinder under heterogeneous heat flux using nanofluids

Abstract

Purpose This study aims to investigate a three-dimensional computational modelling of free convection of Al2O3 water-based nanofluid in a cylindrical cavity under heterogeneous heat fluxes that can be used as a thermal storage tank. Design/methodology/approach Effects of different heat flux boundary conditions on heat transfer and entropy generation were examined and the optimal configuration was identified. The simulation results for nanoparticle (NP) volume fractions up to 4 per cent, and Rayleigh numbers of 104, 105 and 106 were presented. Findings The results showed that for low Ra (104) the heat transfer and entropy generation patterns were symmetric, whereas with increasing the Rayleigh number these patterns became asymmetric and more complex. Therefore, despite the symmetric boundary conditions imposed on the periphery of the enclosure (uniform in Ɵ), it was necessary to simulate the problem as three-dimensional instead of two-dimensional. The simulation results showed that by selecting the optimal values of heat flux distribution and NP volume fraction for these systems the energy consumption can be reduced, and consequently, the energy efficiency can be ameliorated. Originality/value The results of the present study can be used for the design of energy devices such as thermal storage tanks, as both first and second laws of thermodynamics have been considered. Using the optimal design will reduce energy consumption.

Investigation of the novelty of latent functionally thermal fluids as alternative to nanofluids in natural convective flows

“…The correlations (Eqs. [5][6][7][8][9][10][11][12] are derived in the present work, using curve fitting technique by the method of least squares. The R 2 value is 99.8% and a maximum error is 1%.…”

“…Several studies reported the effect of adding nanoparticles, without liquid-solid phase change in the core, on the enhancement of convective heat transfer flows. Examples can be found in [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] . Other work studies on nanofluids can be also found in [23][24][25][26][27][28][29][30] .…”

Entropy production and mixed convection within trapezoidal cavity having nanofluids and localised solid cylinder

“…Natural convection heat transfer and total entropy generation of nanofluid in a square cavity in presence of a refrigerant rigid body was considered by Rahimi et al 17 . Recently, Rashidi et al 18 investigated a three-dimensional free convection and entropy generation of water-based nanofluid in a cylindrical cavity. Natural convection and entropy generation in an air-filled cubical cavity with active lateral walls was studied by Alnaqi et al 19 .…”

Control of the free convective heat transfer using a U-shaped obstacle in an Al2O3-water nanofluid filled cubic cavity

“…It was found that the MHD effect opposes the nanofluid effect and reduces the heat transfer. Rashidi et al (2020) studied the effect of nanofluid concentration on the irreversibility production in a cylindrical cavity subjected to various boundary conditions. It was found that the addition of nanoparticles can be used as an entropy generation optimizing parameter.…”