scholarly journals Comprehensive investigations of mixed convection of Fe–ethylene-glycol nanofluid inside an enclosure with different obstacles using lattice Boltzmann method

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chenqi Fu ◽  
Amin Rahmani ◽  
Wanich Suksatan ◽  
S. M. Alizadeh ◽  
Majid Zarringhalam ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Ethylene Glycol ◽  
Mixed Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Richardson Number ◽  
Attack Angle ◽  
Left Wall ◽  
Boltzmann Method

AbstractIn the present paper, nanofluid mixed convection is investigated in a square cavity with an adiabatic obstacle by using the Lattice Boltzmann method (LBM). This enclosure contains Fe–ethylene-glycol nanofluid and three constant temperature thermal sources at the left wall and bottom of the enclosure through a lateral wall. The fluid is incompressible, laminar, and Newtonian. The obtained results are presented in the constant Ra = 104 and a Pr = 0.71 for different Ri = 0.1, 1, and 10. The effects of the slope of the enclosure, volume fraction of nanoparticles $$\left( \varphi \right)$$ φ , the location of adiabatic obstacles, and nanoparticle diameter in the fluid are investigated on the value of heat transfer. A change in the attack angle of the enclosure leads to changes in the movement distance for fluid between hot and cold sources and passing fluid through case E, which affects the flow pattern strongly. In each attack angle, on colliding with an obstacle, the fluid heat transfers between two sources, which leads to uniform heat transfer in the enclosure. By increasing the velocity of the lid, the Richardson number decreases leading to improvement of the convective heat transfer coefficient and Nusselt number enhancement. The results so obtained reveal that by augmenting $$\varphi$$ φ value the effect of Richardson number reduction can augment Nusselt number and the amount of absorbed heat from the hot surface. Consequently, in each state where a better flow mixture and lower depreciation of fluid velocity components, due to the penetration of lid movement and buoyancy force, occurs higher heat transfer rate is accomplished. Furthermore, it is shown that when Ri = 0.1, the effect of cavity angle is more important but when Ri = 10, the effect of the position of obstacle is more visible.

Computation of Mixed Convection and Volumetric Radiation in Vertical Channel Based on Hybrid Thermal Lattice Boltzmann Method

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Soufiane Derfoufi ◽  
Fayçal Moufekkir ◽  
Ahmed Mezrhab
Keyword(s):  
Heat Transfer ◽  
Mixed Convection ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Richardson Number ◽  
Numerical Study ◽  
Vertical Channel ◽  
Governing Equations ◽  
Boltzmann Method ◽  
Thermal Lattice Boltzmann

The present paper presents a numerical study of mixed convection coupled with volumetric radiation in a vertical channel. The geometry of the physical model consists of two isothermal plates. The governing equations of the problem are solved using a hybrid scheme of the lattice Boltzmann method (LBM) and finite-difference method (FDM). The main objective of this study is to evaluate the influence of the Richardson number (Ri) and the emissivity of the walls (εi) on the heat transfer, on the flow, and on the temperature distribution. Results show that Richardson number and emissivity have a significant effect on heat transfer and air flow.

HEAT TRANSFER ENHANCEMENT IN A CHANNEL PARTIALLY FILLED WITH A POROUS BLOCK: LATTICE BOLTZMANN METHOD

2013 ◽  
Vol 24 (09) ◽  
pp. 1350060 ◽  
Author(s):  
M. NAZARI ◽  
M. H. KAYHANI ◽  
R. MOHEBBI
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Lattice Boltzmann Method ◽  
Heat Transfer Enhancement ◽  
Lattice Boltzmann ◽  
Block Size ◽  
Blockage Ratio ◽  
Transfer Enhancement ◽  
Porous Block ◽  
Boltzmann Method

The main goal of the present study is to investigate the heat transfer enhancement in a channel partially filled with an anisotropic porous block (Porous Foam) using the lattice Boltzmann method (LBM). Combined pore level simulation of flow and heat transfer is performed for a 2D channel which is partially filled with square obstacles in both ordered and random arrangements by LBM which is not studied completely in the literature. The effect of the Reynolds number, different arrangements of obstacles, blockage ratio and porosity on the velocity and temperature profiles inside the porous region are studied. The local and averaged Nusselt numbers on the channel walls along with the respective confidence interval and comparison between results of regular and random arrangements are presented for the first time. For constant porosity and block size, the maximum value of averaged Nusselt number in the porous block is obtained in the case of random arrangement of obstacles. Also, by decreasing the porosity, the value of averaged Nusselt number is increased. Heat transfer to the working fluids increases significantly by increasing the blockage ratio. Several blockage ratios with different arrangements are checked to obtain a correlation for the Nusselt number.

Lattice Boltzmann Method for Combined Natural Convection Surface Radiation in Open Cavity

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Ayoub Msaddak ◽  
Mohieddine Ben Salah ◽  
Ezeddine Sediki
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Lattice Boltzmann Method ◽  
Inclination Angle ◽  
Lattice Boltzmann ◽  
Surface Radiation ◽  
Surface Emissivity ◽  
Boltzmann Method

Lattice Boltzmann method (LBM) is performed to study numerically combined natural convection and surface radiation inside an inclined two-dimensional open square cavity. The cavity is heated by a constant temperature at the wall facing the opening. The walls normal to the heated surface are assumed to be adiabatic, diffuse, gray, and opaque while the open boundary is assumed to be black at ambient temperature. A Bathnagar, Gross and Krook (BGK) collision model with double distribution function (D2Q9-D2Q4) is adopted. Effects of surface radiation, inclination angle, and Rayleigh number on the heat transfer are analyzed and discussed. Results are presented in terms of isotherms, streamlines, and Nusselt number. It was found that the presence of surface radiation enhances the heat transfer. The convective Nusselt number decreases with increasing surface emissivity as well as with Rayleigh number, while the total Nusselt number increases with increasing surface emissivity and Rayleigh number. The inclination angle has also a significant effect on flow and heat transfer inside the cavity. However, the magnitude of total heat transfer decreases considerably when open cavity is tilted downward.

Flow and Heat Transfer Characteristics in Ribbed Channel Using Lattice Boltzmann Method

2013 ◽  
Author(s):  
Prateek Sharma ◽  
Bittagopal Mondal ◽  
Gautam Biswas
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Heat Transfer Characteristics ◽  
Ribbed Channel ◽  
Flow And Heat Transfer ◽  
Boltzmann Method

In order to improve the efficiency of the gas turbines and power plants, researchers have aimed to reach higher turbine inlet temperatures. There is always a metallurgical limit for highest temperature, as the materials pertaining to turbine cannot withstand very high temperature due to change in material properties. Deformation, creeping and even melting of turbine blades may occur. To alleviate these, researchers have been trying to evolve the cooling systems for turbine blades. Two major cooling strategies involve (a) external cooling and (b) internal cooling. In case of internal cooling, a layer of air or some coolant is made to flow through small passages inside the blade. Both the systems remove heat from the blade and keep the blade temperature under the metallurgical limit. The present work is aimed at modeling the internal cooling passages of the gas turbine blades. The same geometry can throw light on the performance of cooling passages used in electronic devices. Taking these two applications into consideration, it becomes necessary to study flow and heat transfer past bluff-bodies and in ribbed channels. In the present work, the fluid flow behavior and heat transfer characteristics in a rectangular channel with staggered ribs mounted on both walls are analyzed using the lattice Boltzmann method (LBM). This study is carried out for the fluid with Prandtl number Pr = 0.7 and a wide range of Reynolds numbers (10 ≤ Re ≤ 120). The computational strategy is applied in various test cases and validated with the results reported in the literature. The unsteady flow behaviors, such as, instantaneous streamlines, vortex shedding frequency and phase plots are reported. For the ribbed channel (with staggered ribs), the heat transfer is predicted with the help of isotherms, local Nusselt number distribution and average Nusselt number.

scholarly journals Numerical analysis of forced convection heat transfer in a rectangular micro-channel totally filled with Ag/ water nano fluid in slip flow regime using the lattice Boltzmann method

2021 ◽  
Vol 321 ◽  
pp. 04008
Author(s):  
Kaouther Ben Ltaifa ◽  
Annunziata D’Orazio ◽  
Arash Karimipour ◽  
Hacen Dhahri
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Slip Velocity ◽  
Temperature Jump ◽  
Micro Channel ◽  
Slip Coefficient ◽  
Nano Fluid ◽  
Boltzmann Method

Numerical simulation reported on heat transfer and fluid flow in a two-dimensional rectangular micro channel totally filled with Ag/water. The first –order slip/jump boundary conditions were uniformly imposed to the up and bottom walls. The governing conservation equations are translated in dimensionless form using the thermal Single Relaxation Time (T-SRT) modified Lattice Boltzmann Method (LBM) with double distribution functions (DDFs). The viscous dissipations effects are adopted into the energy equation. Effects of nanoparticle volume fraction φ, slip coefficient, B, on the flow of Nano fluid and heat transfer were studied. The results were interpreter in terms of slip velocity; temperature jump and Nusselt number. Based on the results found, it can be concluded that decreasing the values of slip coefficient enhances the convective heat transfer coefficient and consequently the Nusselt number (Nu) but increases the slip velocity at the wall and temperature jump values.

Nusselt Number Prediction for Slip Flow in Confined Porous Media Based on Lattice Boltzmann Method

2019 ◽  
Author(s):  
Ammar Tariq ◽  
Zhenyu Liu ◽  
Zhiyu Mu ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Nusselt Number ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Slip Flow ◽  
Flow And Heat Transfer ◽  
Prime Concern ◽  
Multiple Relaxation Time ◽  
Boltzmann Method

Abstract Understanding flow and heat transfer in porous media is a matter of prime concern for micro devices. In this work, slip flow and heat transfer of gaseous fluid through the confined porous media is numerically simulated using a multiple-relaxation-time lattice Boltzmann method. The method is employed using an effective curved boundary treatment based on non-equilibrium extrapolation and counter-extrapolation methods. Nusselt number prediction for varying porosity, Knudsen and Reynolds number are studied. Based on the obtained numerical results, it is proved that the current technique can be used to effectively model slip flow and heat transfer at pore-scale.

Investigation of Nanofluid Heat Transfer in a Microchannel Under Magnetic Field Via Lattice Boltzmann Method: Effects of Surface Hydrophobicity, Viscous Dissipation, and Joule Heating

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Ali Alipour Lalami ◽  
Hamid Hassanzadeh Afrouzi ◽  
Abouzar Moshfegh ◽  
Mohammad Omidi ◽  
Ashkan Javadzadegan
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Nusselt Number ◽  
Lattice Boltzmann Method ◽  
Viscous Dissipation ◽  
Joule Heating ◽  
Lattice Boltzmann ◽  
Slip Coefficient ◽  
Hydrophobic Surfaces ◽  
Boltzmann Method

In this paper, effect of Joule heating (JH), viscous dissipations (VD), and super hydrophobic surfaces on heat transfer of water–Al2O3 and water–CuO nanofluids in a microchannel has been investigated using lattice Boltzmann method (LBM). The microchannel is under a uniform and transverse magnetic field. The lower wall of the microchannel is insulated and a uniform heat flux has been applied to the upper wall. Results are generated at constant Reynolds number of 150, volume fraction of 2%, and a diameter of 25 nm with variable Hartmann numbers ranging from 0 to 20 and nondimensional slip coefficients from 0 to 0.05. The results of the developed code are in good agreement with other analytical, numerical, and experimental reports. Moreover, the results show that in such case, ignoring the JH and VD leads to a significant error in the prediction of Nusselt number up to 62% and 56%, respectively, for water–Al2O3 and water–CuO nanofluids. It has also been shown that using a super hydrophobic surface with a slip coefficient of 0.05 leads to a significant reduction in VD; however, it increases the effect of JH. On the other hand, it is found that, despite JH and viscous dissipation effects, using super hydrophobic surfaces (up to a slip coefficient of 0.05) leads to an increase in Nusselt number and decrease in shear stress for all the studied Hartmann numbers. Finally, it has been concluded that super hydrophobic surfaces can be used as a passive tool to enhance the heat transfer rate and simultaneously decrease the pumping power demand.

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