Numerical study of nanofluid natural convection in a square cavity with a hot obstacle using lattice Boltzmann method

Abstract

In the present work, for the first time, laminar natural convection of water-TiO 2 nanofluid around a hot obstacle in a square cavity is simulated by Lattice Boltzmann Method (LBM). The effect of Rayleigh number, obstacle dimension, volume fraction of nanofluid, cavity dimensions, surface ratio and various models for computing of thermal conductivity coefficient and viscosity coefficient on Nusselt number and heat transfer around hot obstacle in enclosure has been investigated. The results show that by increase in Rayleigh number and volume fraction, average Nusselt number will increase. The average Nusselt number will increase when obstacle dimensions increase to 0.5 L but it will decrease when the obstacle dimensions increase to 0.7 L. Vortexes will create in 0.8 L and it causes to increase heat transfer. By reduplicating the obstacle width, heat transfer is better than reduplicating the obstacle length. The average Nusselt number increases by increase in cavity length and it will decrease by increase in cavity wide. All results are equal in Hamilton-Crosser and Maxwell-Garnett model when the surface ratio is one. But heat transfer will increase by decreasing surface ratio. The average Nusselt number in Wang model is less than Nusselt number in Brinkman model. Ó 2017 Faculty of Engineering, Alexandria University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Three-Dimensional Numerical Study of the Effect of Protective Barrier on the Dispersion of the Contaminant in a Building

“…Comparison of the obtained average Nusselt number with the results of Rahmati et al[24] at Ra = 10 6 .…”

“…The numerical code was then verified by comparing the results with those obtained in two different simulation cases: the first case concerns a three-dimensional cavity with a horizontal gradient of temperature and concentration filled with an aqueous solution Pr = 10, Le = 10 and Ra = 10 5 developed by Sezai and Mohamad [23], and the second one is related to a square cavity of dimension L filled with nanofluids containing a square hot obstacle centered in the cavity with a width W. The Prandtl number is equal to 6.2 and the Rayleigh number is equal to 10 6 . The nanofluid is water-Cu with a fraction of 0.04 [24] (Table 3). It is clear that the results of our code are in good agreement with those proposed by Rahmati and Tahery [24].…”

“…The nanofluid is water-Cu with a fraction of 0.04 [24] (Table 3). It is clear that the results of our code are in good agreement with those proposed by Rahmati and Tahery [24]. Indeed, the maximum deviation is of the order of 1.8%.…”

Augmentation of convection heat transfer from a horizontal cylinder in a vented square enclosure with variation of lower opening size

“…The results displayed Nu increased proportionally with the vent size at low enclosure widths and it is inversely proportional with vent size for high enclosure widths. Rahmati and Tahery [14] investigated the effect of Ra, obstacle dimension, nanofluid volume fraction, cavity dimensions, surface ratio and various models for thermal conductivity coefficient and viscosity coefficient on Nu and heat transfer around hot obstacles in an enclosure for laminar natural convection of water-TiO2 nanofluid using the Lattice Boltzmann Method. The results indicated that the average Nu increased with the increase in Ra and volume fraction.…”

A Characteristic-based Numerical Simulation of Water-titanium Dioxide Nano-fluid in Closed Domains

“…Different nano-particle with water was considered. Rahmati and Tahery [8] simulated the laminar natural convection in the cavity flow numerically. They studied water-TiO2 nano-fluid with Lattice-Boltzmann method.…”