Lattice Boltzmann Method for Natural Convection Flows in a Full Scale Cavity Heated from Below

Abouricha, Noureddine; Alami, Mustapha El; Kriraa, Mounir; Souhar, Khalid

doi:10.7726/ajhmt.2017.1008

Cited by 7 publications

(6 citation statements)

References 19 publications

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“…The Lattice Boltzmann (LB) Model with single relaxation time (SRT) is used in this work is the same as that employed in (Dixit and Babu, 2006;Mohamad and Kuzmin, 2010;Abouricha et al, 2016Abouricha et al, , 2017Abouricha et al, , 2019. This model uses two single particle distribution functions: the first is f k (r, t) for dynamic while the second is g k (r, t) for thermal field simulations.…”

Section: Lattice Boltzmann Methodsmentioning

confidence: 99%

“…The difference between case 1(sinusoidal heating) and case 2 (mono alternative heating) is that, in the last case, the temperature is controlled using a booster when it becomes less than an average temperature that must be upper of the indoor temperature. Hence, the present study is a continuity of previous works Abouricha et al (2016Abouricha et al ( , 2017Abouricha et al ( , 2019, its objective is to study the effect of the amplitude "a" and the period "j " of the imposed temperature in both cases on the dynamic and thermal fields inside the cavity for turbulent natural convection model. This is done by using the Lattice Boltzmann method (LBM) for high Rayleigh number Ra = 10 8 .…”

Section: Introductionmentioning

confidence: 99%

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Lattice Boltzmann modeling of convective flows in a large-scale cavity heated from below by two imposed temperature profiles

Abouricha

Alami

Souhar³

2019

HFF

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Purpose The purpose of this paper is to model the convective flows in a room equipped by a glass door and a heated floor of length l = 0.8 × H and submitted to a sinusoidal temperature profile and mono alternative temperature profile. Design/methodology/approach The paper opts for a numerical study of convective flows in a large scale cavity using the Lattice Boltzmann Method (LBM) by considering a two dimensions (2D) square cavity of side H and filled by air (Pr = 0.71). All the vertical walls, the ceiling and the rest of the floor are thermally insulated, the hot portion of length l = 0.8×H is heated with two imposed temperature profiles of amplitude values 0.2 ≤ a ≤ 0.6 and for two different periods ζ = ζ0 and ζ = 0.4×ζ0. One of the vertical walls has a cold portion θc = 0 that represents the glass door. Findings A systematic study of the flow structure and heat transfer is carried out considering principal control parameters: amplitude “a” and period ζ for Rayleigh number Ra = 108. Effects of these parameters on results are presented in terms of isotherms, streamlines, profiles of velocities, temperature in the cavity, global and local Nusselt number. It has been found that an increase in amplitude or period increases the amplitude of the temperature in the core of cavity. The Nusselt number increases when the amplitude “a” of the imposed temperature increases, but this later is not affected by variation of the period. Originality/value The authors used LBM to simulate the convective flows in a cavity at high Ra, heated from below by tow imposed temperature profiles. Indeed, they simulate a local equipped by a solar water heater (SWH). The floor is subjected to a periodic heating: Sinusoidal heating (Case 1) for which the temperature varies sinusoidally (SWH without a supplement), and mono alternation heating (Case 2), the temperature evolves like a redressed signal (SWH with a supplement). The considered method has been successfully validated and compared with the previous work. The study has been conducted using several control parameters such as the signal amplitude and period in the case of turbulent convection. This allowed us to obtain a considerable set of results that can be used for engineering.

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Section: Lattice Boltzmann Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lattice Boltzmann modeling of convective flows in a large-scale cavity heated from below by two imposed temperature profiles

Abouricha

Alami

Souhar³

2019

HFF

Self Cite

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“…The time steps considered range between 10 -4 and 10 -3 . In our future work, we will consider the case of turbulent flows and we will use Lattice Boltzmann method [12] to treat this problem in the microscopic scale.…”

Section: Methodsmentioning

confidence: 99%

Numerical Study of Mixed Convection Flows in a U-shaped Channel: Application to the Canadian Well

Naoum¹,

Alami²

2017

AJHMT

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In the present work, we study, numerically, mixed convection flows in an open U-shaped channel as an application to a Soil -air exchanger (Canadian well). The channel is submitted to a vertical jet of fresh air from the right opening (ambient air) at a cold temperature (winter) Tc, while the walls are heated according to the depth of channel. We will detail the soil temperature values in this paper, using Kasuda model. Emphasis is given to detail the effect of the channel length variation on average temperature, average velocity and heat transfer at the channel outlet.Our study is based on the numerical volume control method, performed for Re=1000, Ra= 5×10 6 and Pr=0.72, 20m≤L≤60m. We will present thermal and dynamic fields, flow velocities, temperatures at the outlet and Nusselt number variation with L. Our results show that the Nusselt number becomes constant from a critical value of the channel length.

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“…By relying on this novel technique, the authors found that the heat transfer could be up to seven times higher compared to their non‐aspiration counterparts' cases. An enormous effort has been directed toward natural convection through extensive studies in the literature during the past years 6–8 …”

Section: Introductionmentioning

confidence: 99%

“…An enormous effort has been directed toward natural convection through extensive studies in the literature during the past years. [6][7][8] Unfortunately, the enhancement of natural convection heat transfer is accompanied by undesirable entropy generation. The concept of entropy generation, which derives from the second law of thermodynamics makes it possible to evaluate the loss of exergy (available work).…”

Section: Introductionmentioning

confidence: 99%

CFD‐based analysis of entropy generation due to mean and fluctuating fields during turbulent natural convection in a square enclosure

2022

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The current study aims to numerically investigate the entropy generation during the natural convection flow of air in a square cavity. The governing equations for the conservation of mass, momentum, energy, and turbulence are solved using a control volume‐based technique employing the commercial code Fluent. Runs have been performed for both laminar and turbulent flow regimes by varying the Rayleigh number (Ra) from 103 to 1010. On the other hand, various viscous distribution coefficients (ϕ = 10−4, 10−3, and 10−2) and constant Prandtl number (Pr = 0.71) were considered. Given the conflicting perspectives in the literature regarding the entropy generation under turbulent regimes, more research is needed to better understand the impact that the fluctuating flow has on entropy production. The four terms of entropy generation inherent to turbulent natural convection (entropy generation due to dissipation in the mean and the fluctuating velocity fields in addition to the heat flux due to the mean and the fluctuating temperature) are computed in the present work and compared to calculations based on only mean values of temperature and velocity gradients. It was found that taking into account the fluctuating terms of temperatures and velocities augment the total entropy generation by 10.10%, 14.43%, and, 17.70%, up to 32.60%, respectively, for Ra = 5 × 108, Ra = 109, Ra = 1.58 × 109, and Ra = 1010. The gain shows the tendency to increase with the Rayleigh number. Thus, the fluctuating terms cannot be neglected particularly for high Rayleigh numbers. Furthermore, unlike entropy production due to the mean flow field, numerical outcomes reveal that the generated irreversibilities due to fluctuating flow are located around the upper hot and the lower cold corners of the heated walls. In addition, a numerical relationship between the first and the second laws of thermodynamics has been derived. A promising result that emerged from this study has shown that the Nusselt number and therefore the first law of thermodynamics is sufficient to estimate the heat part of entropy generation without the necessity of using the second law.

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Lattice Boltzmann Method for Natural Convection Flows in a Full Scale Cavity Heated from Below

Cited by 7 publications

References 19 publications

Lattice Boltzmann modeling of convective flows in a large-scale cavity heated from below by two imposed temperature profiles

Lattice Boltzmann modeling of convective flows in a large-scale cavity heated from below by two imposed temperature profiles

Numerical Study of Mixed Convection Flows in a U-shaped Channel: Application to the Canadian Well

CFD‐based analysis of entropy generation due to mean and fluctuating fields during turbulent natural convection in a square enclosure

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