Three-dimensional Enclosure Research Articles

Direct numerical simulation of three-dimensional particle-laden thermal convection using the Lattice Boltzmann Method

In thermal multiphase flows, the modulation in the heat transfer rate due to the presence of finite-size solid particles attract growing interest in recent years. This study focuses on developing a robust and efficient simulation method for particle-laden Rayleigh-Bénard convection. The present work utilizes the double distribution function-based thermal lattice-Boltzmann method (TLBM), which enables successful simulations of multiphase fluid-thermal interactions. The no-slip boundary of the moving solid particles is handled by the interpolated bounce-back scheme. Additionally, Galilean invariant momentum exchange and heat exchange approaches are employed for hydrodynamic force and heat transfer calculation at the solid boundaries. The accuracy of the current method is verified with several benchmark cases, including three-dimensional single-phase Rayleigh-Bénard convection, as well as the settling of hot and cold spherical particles in a three-dimensional enclosure. Furthermore, we explore the modulation of Rayleigh-Bénard flows due to the presence of freely moving finite-size particles. The simulations are conducted on a distributed memory cluster with a 3D domain decomposition technique facilitated by the MPI library. A brief discussion on the parallel performance of the simulations is provided for both particle-laden and single-phase flow scenarios. Finally, the effects of finite-size solid particles on the overall heat transfer efficiency and modulation to the flow field in three-dimensional particle-laden turbulent Rayleigh-Bénard convection are discussed. The results show that addition of solid particles results in a moderate increase in the overall Nusselt number, and this enhancement is mainly due to the increased heat flux transported by the particles.

Natural convection heat transfer in a three-dimensional enclosure under the effect of heated pin-fins of various shapes

Natural convection enhancement for heat sinks with the help of pin-fins has been extensively researched, but further investigations are still required regarding the technological development. In order to understand the effect of different pin-fins shapes on the heat transfer and fluid flow pattern in a three-dimensional air-filled enclosure, a numerical investigation is conducted. The enclosure is heated by the left wall, on which pin-fins are attached, and cooled by the right wall, while the other walls are considered adiabatic. A validation has been made with both experimental and numerical results from the literature, and a good agreement has been observed. Five pin-fins shapes with the same base surface area and length are tested: circular, triangular, square, pentagonal, and hexagonal. The findings show that the circular pin-fins exhibit the highest thermal performance. Furthermore, for different Rayleigh numbers, increasing the number of pin-fins improves the thermal performance of heat sinks.

Comment on the paper “Optimization and numerical investigation of the effect of wall conduction and magnetic field on the nanofluid flow inside a three-dimensional enclosure using the lattice Boltzmann method, Farhan Khan, Yang Xiao-Dong, Nudrat Aamir, Tareq Saeed, Muhammad Ibrahim, Chemical Engineering Communications, 2023, Vol. 210, No. 5, 955–969”

Some serious errors exist in the above paper.

Thermal evaluation of a room coated by thin urethane nanocomposite layer coating for energy-saving efficiency in building applications

Today, it is common to use thin-layer nanocomposite coatings as insulation to reduce heat loss through building walls. One of the important advantages of these coatings is preventing energy loss as a thermal barrier in low thicknesses and with high efficiency. Investigations on the energy loss and saving of coated buildings are often practiced using numerical and experimental approaches. In this study, numerical simulation and experimental evaluation consisting of modification of nanoparticles and preparation powder coating nanocomposite, are used to study the effects of coated polyurethane nanocomposite containing nano Al2O3 and nano ZrO2 on both sides of the walls of a sample room on temperature distribution and heat transfer. For this purpose, a three-dimensional enclosure was assumed as a room having a radiant cooling panel, which is modeled under various features of the walls' interior and exterior coating. To determine the flow and temperature fields, the governing equations that include the continuity, momentum, turbulence, and energy equations, which are coupled through the buoyancy term, have been solved using the Fluent software. The SIMPLE algorithm to accommodate the pressure-velocity coupling, the k-ε model for turbulence modeling, the Boussinesq approximation for buoyancy term modeling, and the DO model for radiation simulation, are employed. The results of the thermography of the samples showed that the temperature reduction in the samples containing zirconium oxide compared to aluminum oxide had a better performance in the thermal insulation of the coating and the lowest temperature was observed in the nanocomposite containing 3% zirconium oxide. Numerical studies showed that this thin layer nanocomposite coating reduces energy consumption by 4% and 13%, respectively, compared to pure polyurethane coatings and acrylic paints.

Optimization and numerical investigation of the effect of wall conduction and magnetic field on the nanofluid flow inside a three-dimensional enclosure using the lattice Boltzmann method

The LBM is used to investigate three-dimensional nanofluid (NFs) flow inside a square enclosure with a heat source in this research. The heat source is located in the enclosure's middle and operates at a high temperature. The sidewalls have a thickness, leading to heat transfer (HE-TR) from the sidewalls that are at low temperatures to the internal fluid due to their thermal conductivity. An inclined magnetic field (MF) uniformly affects the fluid flow. The effect of parameters such as Rayleigh number (Ra), thickness and thermal conductivity of the sidewall, dimensions of the heat source, Hartmann number (Ha), the volume fraction of nanoparticles (φ), and the angle of the MF on two- and three-dimensional field flow and HE-TR is investigated. Optimization is made on the parameters for maximum HE-TR. The lattice Boltzmann method has been used to simulate nanofluid flow. The results show that an enhancement in the Ha and the angle of the MF reduces the amount of HE-TR. HE-TR is improved by increasing the thermal conductivity of thick walls. The quantity of HE-TR is increased when nanoparticles are added to water.

Numerical Simulation of Free Convection in a Three-Dimensional Enclosure Full of Nanofluid with the Existence a Magnetic Field

Blood glucose automatic regulation achievement depends on the robustness of the used control algorithm. However, some constraints were encountered due to the human glucose-insulin regulatory system’s complexity. It is proposed to tackle such a goal through the development of a robust synergetic control algorithm. An adaptive approach is integrated into this synergetic control scheme to handle disturbances and parameters variations. Multiple meal disturbances often occur daily as well as some other stochastic noises making efficient glucose regulation a tough challenge addressed in this paper via a new synergetic scheme. Simulation results show a robust function during multiple meal disturbances with good noise rejection.

Numerical Simulation of Free Convection in a Partially Heated Three-Dimensional Enclosure Filled with Ionanofluid ([C4mim][NTf2]-Cu)

A numerical analysis was performed to study free convection in a stationary laminar regime in a partially heated cube filled with ionanofluid. To numerically solve the dimensionless equations, we applied the finite volume method using the SIMPLEC algorithm for pressure correction. All walls are adiabatic, except for the left and right side walls which are partially heated differently. At the end of this simulation, several results are given in the form of current lines, isotherms, and variations in the Nusselt number. These results are obtained by analyzing the effect of a set of factors such as Rayleigh number, particle volume fraction, cold and source position on the dynamic and thermal fields, and heat transfer. It has been shown that the percentage of nanoparticles and high Rayleigh numbers significantly increase heat transfer by ionanofluid. Two comparisons have been made, between ionic fluid and ionanofluid at isotherms and streamlines, and between nanofluid and ionanofluid at Nusselt number, which show the advantage of using ionanofluid in heat transfer.

Lattice Boltzmann simulation of natural convection melting in a cubic cavity with an internal cylindrical heat source

In this work, natural convection melting in a cubic cavity with an internal cylindrical heat source is studied numerically by employing the two-relaxation-time lattice Boltzmann (LB) method. In numerical simulations, natural convective melting of pure Gallium in a three-dimensional enclosure is first considered to validate the present LB model. Then, effects of some key parameters, including the thermal boundary conditions at the walls of the outer enclosure, the location and the placement direction of the inner cylinder are numerically studied and analyzed. It is found that the full melting time obtained for the case of the constant temperature boundary condition is larger than that obtained for the case of the adiabatic boundary condition. In addition, the variation of the location of the inner cylinder plays an essential role in full melting time, and when the inner cylinder is located at the center of the cavity, the full melting time obtained in such a case is always smaller than the other cases. Further, the streamlines as well as the distributions of the temperature obtained for different conditions are also presented and discussed.

Effect of Nanoparticles and Base Fluid Types on Natural Convection in a Three-Dimensional Cubic Enclosure

Convective heat transfer using nanofluids play an important role in thermal applications such as heat exchangers, automotive industries, and power generation. In this work, a numerical analysis is conducted to examine the heat transfer of nanofluid in three-dimensional differentially heated cavity. The finite volume method-based SIMPLEC algorithm is used to solve the system of the mass, momentum, and energy transfer governing equations. The left and the right vertical side walls of the cube are maintained at constant temperatures T C and T H , respectively. The remaining walls of the cube are insulated. Effective thermal conductivity and viscosity of the nanofluid are determined using Brinkman and Maxwell models, respectively. Studies are carried out for three types of nanoparticles and volume fractions of nanoparticles ( 0 – 5 % ). The effects of two binary liquid mixtures as a base fluid (propylene glycol-water and ethylene glycol-water) are also examined. Results show an enhancement of 13 % for Al2O3-EG in comparison to pure ethylene glycol in the case of Ra = 10 3 . In addition, heat transfer enhancement was increased with the rise of nanoparticle volume fractions.

Numerical Simulation of Free Convection in a Three-Dimensional Enclosure Full of Nanofluid with the Existence a Magnetic Field

A numerical analysis was performed to study the influence of a magnetic field in free convection in a cube full with nanofluid. To solve the equation, we appeal to finite volume method. The SIMPLEC algorithm is used for pressure-velocity coupling. All walls are adiabatic, except for the left and right walls that are heated differently. The effects of the Rayleigh and Hartmann numbers, as well as the volume fraction of nanometric particles were studied. Results are conveyed in the form of isotherms, streamlines, velocity curves and Nusselt numbers. It has been shown that as the percentage of nanoparticles increases and the number of Rayleigh increases, heat transfer improves. Hartman number has considerable influence on hydrodynamic and thermal field.

Numerical solutions of non-gray gases and particles radiative transfer in three-dimensional combustion system using DRESOR and SNBCK

The radiative intensity emitted by non-gray gases and particles can be captured by the charge-coupled device (CCD) camera with more than a thousand pixels in the combustion diagnostic. A solution to efficiently provide radiative intensity with high directional resolution in non-gray gases and particles medium is essential for the analysis of combustion system. In this paper, a three-dimensional enclosure filled with non-gray gases and particles was investigated and two real combustion cases were simulated to estimate the accuracy of the DRESOR method. The radiative heat flux, source term and radiative intensity with different directional resolutions were calculated by the DRESOR and DOM methods using SNBCK model. The results showed that the radiative heat flux and source were in good agreement with the reference results, and similar radiative intensities with low directional resolution were obtained by the DRESOR and DOM methods. For the non-isothermal case, the relative difference of maximum intensity between the results calculated with 288 and 13106 directions was 54.23% which was obviously larger than those in isothermal cases. A higher directional resolution was needed for the non-isothermal case. When the high directional resolution scheme was selected, the computational efficiency of the DREOSR method was significantly higher than that of the DOM method. The time consumed by the DOM method was about seven times of that consumed by the DRESOR method when the discrete directions were 800. The DRESOR method and SNBCK model which could obtain radiative intensity with high directional resolution efficiently for non-gray gases and particles medium, was more suitable for the analysis of three-dimensional combustion system.

Transition to doubly diffusive chaos

Doubly diffusive convection driven by horizontal gradients of temperature and salinity is studied in a three-dimensional enclosure of square horizontal cross section and large aspect ratio. Previous studies focused on the primary instability and revealed the formation of subcritical branches of spatially localized states. These states lose stability because of their twist instability, thereby precluding the presence of any related stable steady states beyond the primary bifurcation and giving rise to spontaneous temporal complexity for supercritical parameter values. This paper investigates the emergence of this behavior. In particular, chaos is shown to be produced at a crisis bifurcation located close to the primary bifurcation. The critical exponent related to this crisis bifurcation is computed and explains the unusually abrupt transition. The construction of a low-dimensional model highlights that only a few requirements are necessary for this type of transition to occur. As a consequence, it is believed to be observable in many other systems.

Thermal Convection Inside Three-Dimensional Differentially Heated Cavity Under Laminar and Transitional Flow Conditions

The study presents the heat transfer phenomena of steady buoyancy driven flows inside a three-dimensional square enclosure. The thermal boundary condition of this enclosure are the vertical side walls are maintained at constant temperature difference and all the other walls are adiabatic. Reynolds averaged Navier stokes (RANS) equations are used to model the flow phenomena inside the enclosure, these equations are discretized using finite difference method (FDM) based Fortran code which was developed in house. The study is done for varying Grashof numbers 105 ≤ Gr ≤ 107 and a constant Prandtl number 6.2. The results indicated that as the Grashof number increases the temperature along the enclosure decreases by 24.2% and the rate of transfer of heat inside the enclosure increased by 26%.

Thermal Convection Inside Three-Dimensional Differentially Heated Cavity Under Laminar and Transitional Flow Conditions

The study presents the heat transfer phenomena of steady buoyancy driven flows inside a three-dimensional square enclosure. The thermal boundary condition of this enclosure are the vertical side walls are maintained at constant temperature difference and all the other walls are adiabatic. Reynolds averaged Navier stokes (RANS) equations are used to model the flow phenomena inside the enclosure, these equations are discretized using finite difference method (FDM) based Fortran code which was developed in house. The study is done for varying Grashof numbers 105 ≤ Gr ≤ 107 and a constant Prandtl number 6.2. The results indicated that as the Grashof number increases the temperature along the enclosure decreases by 24.2% and the rate of transfer of heat inside the enclosure increased by 26%.

Three-dimensional analysis of magnetohydrodynamic transverse mixed convection of nanofluid inside a lid-driven enclosure using MRT-LBM

In the current study, an in-house parallel multi-relaxation time lattice Boltzmann method (MRT-LBM) code is developed to resolve and investigate the mixed convection magneto-hydrodynamic (MHD) Cu-water nanofluid flow inside a three-dimensional enclosure with lid-driven walls. The lid-driven walls are moving in different directions with various velocities to form 3D mixed convection (including natural caused by temperature difference and forced convection effects) with a complex mixing within the enclosure. In addition, the magnetic body force effects on the 3D mixed convection flow are observed in terms of the heat transfer and flow characteristics. Accordingly, the complex mixing of flow and heat transfer due to natural convection, moving wall and magnetic field effects is investigated in 3D. In order to scrutinize these three forces effects on the flow characteristics and heat transfer, results are presented and analyzed for various moving wall directions, nanoparticle concentrations (0, 0.2, 0.4, 0.6), Richardson numbers (0.5, 1, 5), Rayleigh numbers (103, 104, 105) and Hartmann numbers (20, 40). It has been shown that the transverse and opposed mixed convection modes have significant negative impacts on the heat transfer. While, the concurrent mixed convection mode remarkably improves the heat transfer. Moreover, the 3D mixing of the transverse mixed convection mode is better than the other cases. Also, though the magnetic field has an undesirable impact on Nusselt, especially in high Ha numbers, but, aligning the MHD force direction and the natural convection circulation plane alleviates this negative impact and makes it ignorable. A comprehensive comparison is made between different cases, and in some situations 30% reduction in heat transfer is observed in comparison with the best case.

Numerical study on convective flow in a three-dimensional enclosure with hot solid body and discrete cooling

The aim of the present numerical study is to analyze the effect of cooler location and aspect ratio and position of the hot solid body inside the enclosure on three-dimensional natural convection flow in a cubical enclosure. The cooler and heater positions and aspect ratio of the heater in a cavity are examined under different combinations of partially cooling vertical sidewalls and, hot solid body in the cubical cavity. That is, (i) different cooler locations with a fixed size of the hot solid body, and, (ii) centrally located hot solid body with different aspect ratio. The three-dimensional convective flow and thermal arrangements in the enclosure are analyzed using the distribution of streamlines, isosurfaces, and Nusselt number. It is found that the cooler location and aspect ratio of hot solid body play a key role on convective cooling and energy transport inside the enclosure. The unit aspect ratio of hot solid body provides higher energy transport inside the enclosure for all cooler positions.

Numerical simulation of natural convection in a horizontal enclosure: Part I. On the effect of adiabatic obstacle in middle

In this study, an effect of a three-dimensional obstacle of natural convection in a horizontal enclosure was discussed. Geometry which was taken into account was horizontal enclosure with unit aspect ratio and length of π along spanwise direction. The enclosure was heated from the bottom wall, and then was cooled down from above. An obstacle was located in the middle of the enclosure to examine its effect. A three-dimensional solution was obtained using Chebyshev spectral multi-domain methodology for different Rayleigh number at which the thermal behavior was evolved from a steady state to a chaotic pattern. As the geometry was elongated in conjunction with periodic boundary conditions to allow lateral freedom for the convection cells, longitudinal geometry along spanwise direction was discretized through a Fourier series expansion with a uniform mesh configuration. An adiabatic obstacle played a different role in determining the thermal behavior: No-slip condition of the surface of the obstacle disturbed the overall plume behavior in terms of the momentum transfer, whereas the adiabatic boundary condition did not influence significantly in terms of energy transfer. At a low Rayleigh number, thermal behavior in three-dimensional enclosure showed steady invariant solution along spanwise direction which is identical to two-dimensional result. With increasing buoyant force, spanwise invariance of longitudinal roll cell was collapsed and three-dimensional mode was obtained following flow regime transition. After undergoing periodically oscillatory phase, a chaotic flow transition occurred. At a high Rayleigh number, three-dimensional thermal plume oscillates freely in elongated geometry and consequently yields higher heat transfer rate. In addition, the thermal flow field was captured by visualizing the three-dimensional vortical structure. The chaotic three-dimensional flow behavior was quantitatively examined by obtaining the turbulent statistics.

Internal heat generation/or absorption phenomena in three-dimensional natural convection flow within enclosure filled with different working fluids

PurposeThe purpose of this study is to investigate the effects of heat generation or absorption on heat transfer and fluid flow within two- and three-dimensional enclosure for homogeneous medium filled with different metal liquid. Numerical results are presented and analyzed in terms of fluid flow, thermal field structures, as well as average Nusselt number profiles over a wide range of dimensionless quantities, Grashof number (Gr) (104 and 105), SQ (varied between −500 to 500) and Prandtl number (Pr = 0.015, 0.024 and 0.0321). The results indicate that when the conductive regime is established for a Grashof number Gr = 104, the 2D model is valid and predicts all three-dimensional results with negligible difference. This was not the case in the convective regime (Gr = 105) where the effect of the third direction becomes important, where a 2D-3D difference was seen with about 37 per cent. Also, in most cases, the authors find that the heat absorption phenomena have the opposite effect with respect to the heat generation.Design/methodology/approachNumerical results are presented and analyzed in terms of fluid flow, thermal field structures, as well as average Nusselt number profiles over a wide range of dimensionless quantities.FindingsGrashof number (Gr) (104 and 105), SQ (varied between −500 to 500) and Prandtl number (Pr = 0.015, 0.024 and 0.0321).Originality/valueThe results indicate that when the conductive regime is established for a Grashof number Gr = 104, the 2D model is valid and predicts all three-dimensional results with negligible difference.

On the three-dimensional effect for natural convection in horizontal enclosure with an adiabatic body: Review from the 2D results and visualization of 3D flow structure

In this study, effect of three-dimensionality of natural convection in horizontal enclosure was discussed. Geometry which was taken into account was horizontal enclosure with radially unit aspect ratio and π of longitudinal direction. The enclosure was heated from the bottom wall, and then was cooled down from above. In addition, obstacle was located in middle of the enclosure to examine an effect of the existence of it. A two-dimensional solution was obtained using Chebyshev spectral multi-domain methodology for different Rayleigh number at which the thermal behavior was evolved from steady state to chaotic pattern. As the geometry was elongated in conjunction with periodic boundary conditions to allow lateral freedom for the convection cells, longitudinal direction was discretized through a Fourier serious expansion with a uniform mesh configuration. Prior to investigate thermal behavior of fluid layer in three-dimensional simulation, two-dimensional results were reviewed with respect to spatial resolution. Whereas coarse resolution provoked thermal instability at intermediate Rayleigh number to have subharmonic solution, fine spatial resolution yielded stably steady convection mode. Thermal behavior in three-dimensional enclosure at low Rayleigh number showed two-dimensional pattern invariant to longitudinal direction. As increasing of buoyant force, longitudinal invariance was collapsed and onset of three-dimensional thermal plume occurred. At high Rayleigh number, three-dimensional thermal plume oscillates freely in elongated geometry and consequently yields higher heat transfer rate. In addition, thermal flow field was captured by visualizing the three-dimensional vortical structure. The chaotic three-dimensional flow behavior was quantitatively examined by obtaining turbulent statistics and compared with those from two-dimensional simulation.

Combination of Dual-MRT lattice Boltzmann method with experimental observations during free convection in enclosure filled with MWCNT-MgO/Water hybrid nanofluid

In the present investigation, the natural convection heat transfer is analyzed numerically and experimentally in a three-dimensional enclosure filled with MWCNT-MgO (75–25%)/Water hybrid nanofluid using an experimental setup. In addition, the thermal conductivity and dynamic viscosity of nanofluid are measured in five different solid volume fractions (φ=0.25%,0.5%,1%,1.5%,and2%) and a temperature range of 20 °C–40 °C, and two correlations are developed. These correlations are utilized in the 3D numerical simulations to obtain the three-dimensional temperature field and validate the experimental results. The temperature distribution, average heat transfer coefficient based on five solid volume fractions of nanofluid plus pure water and four different temperature difference of side walls are presented comprehensively. The comparisons of experimental and numerical data reveal a close agreement with each other.