Numerical simulation of natural convection in a porous cavity with internal hot and cold sources by lattice Boltzmann method

2021 ◽  
Author(s):  
Ying Zhang ◽  
Xuhui Huang ◽  
Yichen Huang ◽  
Meng Xu ◽  
Jie Lei
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Exchange ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Heat Transfer Performance ◽  
Size Ratio ◽  
Transfer Performance ◽  
Spacing Ratio ◽  
Boltzmann Method

Based on the non-orthogonal multiple-relaxation time lattice Boltzmann method (MRT-LBM), natural convection in a porous square cavity with a pair of isothermally hot and cold blocks inside has been studied numerically in the current study. The influence of arrangements (Case1, Case2, Case3, Case4, Case5), spacing ratio (S) and size ratio (A) of the hot and cold sources and the Rayleigh number (Ra) on the heat exchange efficiency has been studied. The results show that different arrangements produce different heat transfer effects. Hot and cold blocks placed horizontally (Case1) and hot block located in the upper left corner while cold block located in the bottom right corner (Case4) have better heat exchange performances than other three cases since the flow directions of hot and cold fluids are closer to that of heat transfer. Then the influence of spacing between blocks and size of blocks on heat transfer rate is further studied in Case1 and Case4. The heat transfer performance is improved with A increasing. Additionally, the variation of heat transfer performance with spacing is related to the arrangement and size ratio of blocks. For Ra=104, 105 and 106, the best heat transfer characteristic can be obtained in Case1 when S=0.05 and A=0.20. For Ra=107, Case4 exhibits the best heat transfer effect when S=0.35 and A=0.20.

Effect of Materials’ Wettability on the Heat Transfer Performance of Fluid Flowing through Microchannel by Lattice Boltzmann Method

2011 ◽  
Vol 320 ◽  
pp. 347-352
Author(s):  
Jing Cui ◽  
Wei Zhong Li ◽  
Yang Liu
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Heat Transfer Performance ◽  
Numerical Approach ◽  
Transfer Performance ◽  
Hydrophobic Property ◽  
Cold Walls ◽  
Boltzmann Method

The material’s wettability plays an important role in the field of micro-fluid flow. In this paper, the effect of material’s wettiability on heat transer performance of fluid flowing through the microchannel has been investigated by numerical approach. The process of the hot liquid flowing through a microchannel with cold walls, whose materials possess different wettabilities, is simulated by lattice Boltzmann method (LBM). The results indicate the heat transfer performance is deteriorated with surface hydrophobic property becomes better. It is because that, for thehydrophobic material, the attractive force of the fluid/solid interaction is small and the flow velocity will be larger which will lead to heat exchang become insufficient. Especially, for the ideal-hydrophobic material, the heat transfer coefficient will be reduced notably. In this case, a gas formed between liquid and soild surface will play a role of the heat insulating layer since the thermal conductivity of the gas is relatively small compared to that of liquid.

Lattice Boltzmann simulation of convective flow and heat transfer in a nanofluid-filled hollow cavity

2019 ◽  
Vol 29 (9) ◽  
pp. 3075-3094
Author(s):  
Qiang Pu ◽  
Farhad Aalizadeh ◽  
Darya Aghamolaei ◽  
Mojtaba Masoumnezhad ◽  
Alireza Rahimi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Rayleigh Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Boltzmann Method

Purpose This paper aims to to simulate the flow and heat transfer during free convection in a square cavity using double-multi-relaxation time (MRT) lattice Boltzmann method. Design/methodology/approach The double-MRT lattice Boltzmann method is used, and the natural convection fluid flow and heat transfer under influence of different parameters are analyzed. The D2Q5 model and D2Q9 model are used for simulation of temperature field and flow field, respectively. The cavity is filled with CuO-water nanofluid; in addition, the thermo-physical properties of nanofluid and the effect of nanoparticles’ shapes are considered using Koo–Kleinstreuer–Li (KKL) model. On the other hand, the cavity is included with an internal active hollow with constant thermal boundary conditions at its walls and variable dimensions. It should be noted that the dimensions of the internal hollow will be determined by as aspect ratio. Findings The Rayleigh number, nanoparticle concentration and the aspect ratio are the governing parameters. The heat transfer performance of the cavity has direct relationship with the Rayleigh number and solid volume fraction of CuO-water nanofluid. Moreover, the configuration of the cavity is good controlling factor for changing the heat transfer performance and entropy generation. Originality/value The originality of this work is using double-MRT lattice Boltzmann method in simulating the free convection fluid flow and heat transfer.

Lattice Boltzmann method for nanofluid flow and heat transfer in a curve-ended T-shaped heat exchanger

2019 ◽  
Vol 29 (1) ◽  
pp. 21-42 ◽  
Author(s):  
Alireza Rahimi ◽  
Hesam Bakhshi ◽  
Ali Dehghan Saee ◽  
Abbas Kasaeipoor ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Nanofluid Flow ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Boltzmann Method

Purpose The study aims to study the nanofluid flow and heat transfer in a T-shaped heat exchanger. For the numerical simulations, the lattice Boltzmann method is used. Design/methodology/approach The end of each branch of the heat exchanger is considered a curve wall that requires special thermal and physical boundary conditions. To improve the thermal performance of the heat exchanger, the CuO–water nanofluid, which has better heat transfer performance with respect to pure water, is used. The dynamic viscosity of nanofluid is estimated by means of KKL model. Several active fins and solid bodies are implanted within the heat exchanger with different thermal arrangements. Findings In the present work, different approaches such as heatline visualization, local and total entropy generation analysis, local and total Nusselt variation are used to detect the impact of different considered parameters such as Rayleigh number (103 < Ra < 106), solid volume fraction of nanofluid (φ = 0,0.01,0.02,0.03 and 0.04 vol. per cent) and thermal arrangements of internal bodies (Case A, Case B, Case C and Case D) on the fluid flow and heat transfer performance. Originality/value The originality of this work is to analyze the two-dimensional natural convection and entropy generation using lattice Boltzmann method.

Free convection analysis in a Γ-shaped heat exchanger using lattice Boltzmann method employing second law analysis and heatline visualization

2019 ◽  
Vol 29 (9) ◽  
pp. 3056-3074 ◽  
Author(s):  
HamidReza KhakRah ◽  
Mehdi Mohammaei ◽  
Payam Hooshmand ◽  
Navid Bagheri ◽  
Emad Hasani Malekshah
Keyword(s):  
Heat Transfer ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Nanofluid Flow ◽  
Content Type ◽  
Flow And Heat Transfer ◽  
Second Law Analysis ◽  
Boltzmann Method

PurposeThe nanofluid flow and heat transfer within a heat exchanger, with different thermal arrangements of internal active bodies, are investigated.Design/methodology/approachFor the numerical simulations, the lattice Boltzmann method is utilized. The KKL model is used to predict the dynamic viscosity of CuO-water nanofluid. Furthermore, the Brownian method is taken account using this model. The influence of shapes of nanoparticles on the heat transfer performance is considered.FindingsThe results show that the platelet nanoparticles render higher average Nusselt number showing better heat transfer performance. In order to perform comprehensive analysis, the heatline visualization, local and total entropy generation, local and average Nusselt variation are employed.Originality/valueThe originality of this work is carrying out a comprehensive investigation of nanofluid flow and heat transfer during natural convection using lattice Boltzmann method and employing second law analysis and heatline visualization.

Natural convection heat transfer of nanofluid inside a cavity containing rough elements using lattice Boltzmann method

2019 ◽  
Vol 29 (10) ◽  
pp. 3659-3684 ◽  
Author(s):  
Rasul Mohebbi ◽  
Mohsen Izadi ◽  
Nor Azwadi Che Sidik ◽  
Gholamhassan Najafi
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Aspect Ratio ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Convection Heat ◽  
Nanofluid Flow ◽  
Content Type ◽  
Boltzmann Method

Purpose This paper aims to study the natural convection of a nanofluid inside a cavity which contains obstacles using lattice Boltzmann method (LBM). The results have focused mainly on various parameters such as number and aspect ratio of roughness elements and different nanoparticle volume fraction. The isotherms and streamlines are presented to describe the hydrodynamics and thermal behaviors of the nanofluid flow throughout the enclosure. Design/methodology/approach The methodology of this paper consists of mathematical model, statement of the problem, nanofluid thermophysical properties, lattice Boltzmann method, LBM for fluid flow, LBM for heat transfer, numerical strategy, boundary conditions, Nusselt (Nu) number calculation, code validation and grid independence. Findings Natural convection heat transfers of a nanofluid inside cavities with and without rough elements have been studied. Lattice Boltzmann technique has been used as numerical approach. The results showed that at higher Rayleigh number (Ra = 106), there are denser streamlines near the left (source) and right wall (sink) which results in better cooling and enhances convective heat rejection to the heat sink. After a distinctive aspect ratio of rough elements (A = 0.1), change in streamline pattern which arises from increasing of aspect ratio does not have an important effect on isotherms. Results indicate that for lower Rayleigh number (Ra = 103), no variation in average Nu is observed with increasing in number of roughness, while for higher one (Ra = 106) average Nu decreases from N = 0 (smooth cavity) up to N = 4 and then remains constant (N = 6). Originality/value Currently, no argumentative and comprehensive extraction can be concluded without fully understanding the role of different arrangement of roughness. Some geometrical parameters such as aspect ratio, number and position of rough elements have been considered. Also, the effect of nanoparticle concentration was studied at different Ra number. Briefly, using LBM, this paper aims to investigate the natural convection of a nanofluid flow on the thermal and hydrodynamics parameters in the presence of rough element with various arrangements.

Nanofluid flow and heat transfer due to natural convection in a semi-circle/ellipse annulus using modified lattice Boltzmann method

2019 ◽  
Vol 29 (12) ◽  
pp. 4746-4763 ◽  
Author(s):  
Qingang Xiong ◽  
Arash Khosravi ◽  
Narjes Nabipour ◽  
Mohammad Hossein Doranehgard ◽  
Aida Sabaghmoghadam ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Lattice Boltzmann Method ◽  
Entropy Generation ◽  
Lattice Boltzmann ◽  
Temperature Fields ◽  
Shape Effect ◽  
Nanofluid Flow ◽  
Content Type ◽  
Boltzmann Method

Purpose This paper aims to numerically investigate the nanofluid flow, heat transfer and entropy generation during natural convection in an annulus. Design/methodology/approach The lattice Boltzmann method is used to simulate the velocity and temperature fields. Furthermore, some special modifications are applied to make the lattice Boltzmann method capable for simulation in the curved boundary conditions. The annulus is filled with CuO-water nanofluid. The dynamic viscosity of nanofluid is estimated using KLL (Koo-Kleinstreuer-Li) model, and the nanoparticle shape effect is taken account in calculating the thermal conductivity. On the other hand, the local/volumetric entropy generation is used to show the irreversibility under influence of different parameters. Findings The effect of considered governing parameters including Rayleigh number (103<Ra < 106); nanoparticle concentration (0<<0.04) and configuration of annulus on the flow structure; temperature field; and local and total entropy generation and heat transfer rate are presented. Originality/value The originality of this work is using of lattice Boltzmann method is simulation of natural convection in a curved configuration and using of Koo–Kleinstreuer–Li correlation for simulation of nanofluid.

Application of lattice Boltzmann method to curved boundaries for simulating nanofluid flow in an L-Shape enclosure

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shayan Naseri Nia ◽  
Faranak Rabiei ◽  
M. M. Rashidi
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Natural Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Curved Boundaries ◽  
Content Type ◽  
Curved Boundary ◽  
Shape Models ◽  
Boltzmann Method

Purpose This paper aims to use the Lattice Boltzmann method (LBM) to numerically simulate the natural convection heat transfer of Cu-water nanofluid in an L-shaped enclosure with curved boundaries. Design/methodology/approach LBM on three different models of curved L-shape cavity using staircase approach is applied to perform a comparative investigation for the effects of curved boundary on fluid flow and heat transfer. The staircase approximation is a straightforward and efficient approach to simulating curved boundaries in LBM. Findings The effect of curved boundary on natural convection in different parameter ranges of Rayleigh number and nanoparticle volume fraction is investigated. The curved L-shape results are also compared to the rectangular L-shape results that were also achieved in this study. The curved boundary LBM simulation is also validated with existing studies, which shows great accuracy in this study. The results show that the top curved boundary in curved L-shape models causes a notable increase in the Nusselt number values. Originality/value Based on existing literature, there is a lack of comparative studies which would specifically examine the effects of curved boundaries on natural convection in closed cavities. Particularly, the application of curved boundaries to an L-shape cavity has not been examined. In this study, curved boundaries are applied to the sharp corners of the bending section in the L-shape and the results of the curved L-shape models are compared to the simple rectangular L-shape model. Hence, a comparative evaluation is performed for the effect of curved boundaries on fluid flow in the L-shape enclosure.

Study of Adiabatic Obstacles on Natural Convection in a Square Cavity Using Lattice Boltzmann Method

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Pawan Karki ◽  
Ajay Kumar Yadav ◽  
D. Arumuga Perumal
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Transfer Rate ◽  
Square Cavity ◽  
Square Enclosure ◽  
The Core ◽  
Vertical Walls ◽  
Boltzmann Method

This study involves the effect of adiabatic obstacles on two-dimensional natural convection in a square enclosure using lattice Boltzmann method (LBM). The enclosure embodies square-shaped adiabatic obstacles with one, two, and four in number. The single obstacle in cavity is centrally placed, whereas for other two configurations, a different arrangement has been made such that the core fluid zone is not hampered. The four boundaries of the cavity considered here consist of two adiabatic horizontal walls and two differentially heated vertical walls. The current study covers the range of Rayleigh number (103 ≤ Ra ≤ 106) and a fixed Prandtl number of 0.71 for all cases. The effect of size of obstacle is studied in detail for single obstacle. It is found that the average heat transfer along the hot wall increases with the increase in size of obstacle until it reaches an optimum value and then with further increase in size, the heat transfer rate deteriorates. Study is carried out to delineate the comparison between the presences of obstacle in and out of the conduction dominant zone in the cavity. The number of obstacles (two and four) outside of this core zone shows that heat transfer decreases despite the obstacle being adiabatic in nature.

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