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

Xiong, Qingang; Khosravi, A.; Nabipour, Narjes; Doranehgard, Mohammad Hossein; Sabaghmoghadam, Aida; Ross, David

doi:10.1108/hff-03-2019-0273

Cited by 12 publications

(5 citation statements)

References 31 publications

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“…The findings depicted that both the total EG rate and the Bejan number augment with the rise of 𝑅𝑎. In a numerical investigation, Xiong et al [31] studied the free convection of water-CuO NF in a semi-circle/ellipse annulus using modified lattice Boltzmann method. The aim of this numerical assessment is to evaluate the free convection flow of a non-Newtonian nanofluid (NF) inside an eccentric horizontal annulus from the point of view of first-law and second-law of thermodynamics.…”

Section: Introductionmentioning

confidence: 99%

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RETRACTED: Free convection of non‐Newtonian nanofluid flow inside an eccentric annulus from the point of view of first‐law and second‐law of thermodynamics

et al. 2020

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The current work aims to perform the hydrothermal and entropy generation (EG) characteristics in a naturally cooled eccentric horizontal annulus filled with non‐Newtonian water‐magnetite/CNT nanofluid (NF). The wall temperature of both cylinders is constant and the temperature of the outer cylinder is lower than that of the inner cylinder. The impacts of vertical eccentricity, nanoadditive concentration (φ) and Rayleigh number (Ra) on the first and second‐laws performance features of the annulus are investigated numerically. It was found the average Nusselt number (Nu), the global thermal EG (TEG) and the global frictional EG (FEG) augment with boosting both the Ra and φ. In addition, it was depicted that the negative eccentricity is desirable and undesirable from the perspective of the first and second‐laws of thermodynamics. Moreover, the outcomes revealed that the first‐law/second‐law performance of the aqueous magnetite/CNT NF is better/weaker than that of the aqueous magnetite NF. Furthermore, for all the examined cases, the TEG rates are much higher than the FEG rates, and as a result, the pattern of total EG changes follows the TEG. Among all the studied cases, the minimum total EG was 4 W/K, which belonged to the case of φM= 0.9%, φCNT= 0%, Ra= 103 and e= 0.001.

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Section: Introductionmentioning

confidence: 99%

“…In a numerical investigation, Xiong et al. [31] studied the free convection of water‐CuO NF in a semi‐circle/ellipse annulus using modified lattice Boltzmann method.…”

Section: Introductionmentioning

confidence: 99%

RETRACTED: Free convection of non‐Newtonian nanofluid flow inside an eccentric annulus from the point of view of first‐law and second‐law of thermodynamics

et al. 2020

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“…Although more velocities of the lattice will occupy more memory and require higher computing requirements, considering the numerical stability and accuracy of turbulent flow, the D3Q27 velocity space discrete scheme was used in this study, as shown in Figure 2. By discretizing the Boltzmann equation in velocity space, physical space, and time, the lattice Boltzmann equation is given as [23] ,…”

Section: Lattice Boltzmann Methodsmentioning

confidence: 99%

Downwash airflow field distribution characteristics and their effect on the spray field distribution of the DJI T30 six-rotor plant protection UAV

Zhang¹,

Wen²,

Chen³

et al. 2023

International Journal of Agricultural and Biological Engineering

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Spray characteristics are the fundamental factors that affect droplet transportation downward, deposition, and drift. The downwash airflow field of the Unmanned Aviation Vehicle (UAV) primarily influences droplet deposition and drift by changing the spray characteristics. This study focused mainly on the effect of the downwash airflow field of the UAV and nozzle position on the droplet spatial distribution and velocity distribution, which are two factors of spray characteristics. To study the abovementioned characteristics, computational fluid dynamics based on the lattice Boltzmann method (LBM) was used to simulate the downwash airflow field of the DJI T30 six-rotor plant protection UAV at different rotor rotational speeds (1000-1800 r/min). A particle image velocimetry system (PIV) was utilized to record the spray field with the downwash airflow field at different rotational speeds of rotors (0-1800 r/min) or different nozzle positions (0, 0.20 m, 0.35 m, and 0.50 m from the motor). The simulation and experimental results showed that the rotor downwash airflow field exhibited the ' dispersionshrinkage-redispersion' development rule. In the initial dispersion stage of rotor airflow, there were obvious high-vorticity and low-vorticity regions in the rotor downwash airflow field. Moreover, the low-vorticity region was primarily concentrated below the motor, and the high-vorticity region was mainly focused in the middle area of the rotors. Additionally, the Y-direction airflow velocity fluctuated at 0.4-1.2 m under the rotor. When the rotor airflow developed to 3.2 m below the rotor, the Ydirection airflow velocity showed a slight decrease. Above 3.2 m from the rotor, the Y-direction airflow velocity started to drastically decrease. Therefore, it is recommended that the DJI T30 plant protection UAV should not exceed 3.2 m in flight height during field spraying operations. The rotor downwash airflow field caused the nozzle atomization angle, droplet concentration, and spray field width to decrease while increasing the vortex scale in the spray field when the rotor system was activated. Moreover, the increase in rotor rotational speed promoted the abovementioned trend. When the nozzle was installed in various radial locations below the rotor, the droplet spatial distribution and velocity distribution were completely different. When the nozzle was installed directly below the motor, the droplet spatial distribution and velocity distribution were relatively symmetrical. When the nozzle was installed at 0.20 m and 0.35 m from the motor, the droplets clearly moved toward the right under the induction of stronger rotor vortices. This resulted in a higher droplet concentration in the right-half spray field. However, the droplet moved toward the left when the nozzle was installed in the rotor tip. For four nozzle positions, when the nozzle was installed at 0 or 0.20 m from the motor, the droplet average velocity was much higher. However, the droplet average velocity was slower when the nozzle was installed in the other two ...

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“…Eslam performed a numerical simulation for studying the vorticity dynamics of a dipole colliding with the wall in a bounded flow and the wake structure and separated flow properties past a circular cylinder at the values of Reynolds numbers with LBM (Eslam Ezzatneshan, 2020). Xiong et al (2019) numerically investigate the nanofluid flow, heat transfer and entropy generation during natural convection in an annulus with LBM. The migration and deposition of microparticles in porous media were numerically simulated with the LB method by Lei et al , 2017.…”

Section: Introductionmentioning

confidence: 99%

Multi-phase lattice Boltzmann (LB) simulation for convective transport of nanofluids in porous structures with phase interactions

Xing¹,

Han

Huang

et al. 2021

HFF

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Purpose A combination of highly conductive porous media and nanofluids is an efficient way for improving thermal performance of relevant applications. For precisely predicting the flow and thermal transport of nanofluids in porous media, the purpose of this paper is to explore the inter-phase coupling numerical methods. Design/methodology/approach Based on the lattice Boltzmann (LB) method, this study combines the convective flow, non-equilibrium thermal transport and phase interactions of nanofluids in porous matrix and proposes a new multi-phase LB model. The micro-scale momentum and heat interactions are especially analyzed for nanoparticles, base fluid and solid matrix. A set of three-phase LB equations for the flow/thermal coupling of base fluid, nanoparticles and solid matrix is established. Findings Distributions of nanoparticles, velocities for nanoparticles and the base fluid, temperatures for three phases and interaction forces are analyzed in detail. Influences of parameters on the nanofluid convection in the porous matrix are examined. Thermal resistance of nanofluid convective transport in porous structures are comprehensively discussed with the models of multi-phases. Results show that the Rayleigh number and the Darcy number have significant influences on the convective characteristics. The result with the three-phase model is mildly larger than that with the local thermal non-equilibrium model. Originality/value This paper first creates the multi-phase theoretical model for the complex coupling process of nanofluids in porous structures, which is useful for researchers and technicians in fields of thermal science and computational fluid dynamics.

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

Cited by 12 publications

References 31 publications

RETRACTED: Free convection of non‐Newtonian nanofluid flow inside an eccentric annulus from the point of view of first‐law and second‐law of thermodynamics

RETRACTED: Free convection of non‐Newtonian nanofluid flow inside an eccentric annulus from the point of view of first‐law and second‐law of thermodynamics

Downwash airflow field distribution characteristics and their effect on the spray field distribution of the DJI T30 six-rotor plant protection UAV

Multi-phase lattice Boltzmann (LB) simulation for convective transport of nanofluids in porous structures with phase interactions

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