Unsteady natural convection and statistical analysis in a CNT–water filled cavity with non-isothermal heating

We propose a new self-propelled nanofluid having advantageous thermal and rheological properties at the same time. The nanofluid consists of a low volume fraction of self-propelled particles known as Artificial Bacterial Flagella (ABF), which will swim as pushers in a manner similar to the swimming of E-coil microorganisms with flagella. A theoretical model is introduced, describing the mechanisms responsible for the reduction of viscosity. The model shows that the swimming velocity of the particle and its geometry play an essential role in the reduction of the suspension viscosity. The results obtained from the theoretical model compare qualitatively with experiments in the literature. The model shows a significant decrease in viscosity at very low volume fractions, and that the viscosity of the suspension is reduced as the volume fraction of the particles increases. Using an in-house finite volume code, we numerically simulate natural convection effects in our ABF self-propelled nanofuid inside a square cavity heated from its vertical sides. Simulations are conducted at volume fractions of 0.7%, 0.8% and 0.83%, comparing the performance of a self-propelled nanofluid with conventional non-active nanofluids (i.e. carbon nanotubes in water). The results show that the heat transfer rate measured by the Nusselt number is three times higher than for the case of classical nanofluids and pure water at the same operating conditions and 0.83% volume fraction of particles. Also, due to the very dilute volume fractions of particles in the proposed nanofluid, their stability can endure for long operating times. There is also a significant decrease in the viscosity (around 25 times lower than water) which will result in a significant reduction in the pumping power.2

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“…The thermo-physical properties of the pure water (solvent) and the carbon nanotubes are obtained from [41], [42] and are listed in Table 1.…”

Section: Mixture Relations and Effective Thermophysical Transport Promentioning

confidence: 99%

Self-propelled nanofluids a path to a highly effective coolant

Hasadi

Crapper

2017

Applied Thermal Engineering

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“…They noticed that the thermal conductivity of nanofluid increase with the nanoparticles volume concentration. Rahman et al [20] numericallyinvestigated the natural convective heat transfer and fluid flow in a square cavity filled with CNT-water nanofluid with non-isothermal heating. They founded that there is an optimum value for nanoparticles volume fraction to control heat transfer, temperature distribution and flow field.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation of three-dimensional thermo-solutal convection of micropolar multi-walled carbon nanotubes water nanofluid stabilized by lignin and sodium polycarboxylate

Manaa

Abidi

Estellé

et al. 2021

J Therm Anal Calorim

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A computational analysis has been performed in this study to solve three-dimensional thermo-solutal natural convection in a differentially heated cubical enclosure filled with micropolar CNT-water nanofluid stabilized by two types of surfactants lignin and sodium polycarboxylate. The work is carried out for different pertinent parameters as Rayleigh number (10 4 Ra 10 6 ), micropolar parameter (0 K 10), buoyancy ratio (-1 N 0) and nanoparticles's volume fraction (0.0055% 0.557%).It is observed that the heat and mass transfer rates are lower for a micropolar nanofluid model when compared to the pure nanofluid model. In fact, the enhancement of micropolar parameter results a decrease of average Nusselt and Sherwood numbers. The use of lignin as a surfactant ameliorates heat and mass transfer rate and nanofluid flow better than the use of sodium polycarboxylate as a surfactant. The nanoparticles volume fraction can be used as a control element for heat rate and fluid flow. Thus, for a nanoparticles volume concentration less than the critical value, the flow intensity is ameliorated and is deteriorated when it exceed this value.

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“…The references of these studies can be classified according to their character: experimental [1][2][3], theoretical [4,5] or numerical [3,. In this last case, solutions are in the steady or unsteady state [32][33][34] and the space is twodimensional [6][7][8][9][10][11][12][13][14][15][16][17][18][19][23][24][25][26][27][28][29][30][31][32][33][34] or tridimensional [20][21][22]25]. The enclosures have various geometries, rectangular or cubical [6-21, 32, 34], cylindrical [33], spherical [22] or also in the form of cylindrical annulus [23][24][25][26] and elliptical [27][28]…”

Section: Introductionmentioning

confidence: 99%

Improvement of Free Convection Heat Transfer in a Concentric Cylindrical Annulus Heat Exchanger Using Nanofluid

Mihoubi¹,

Bouderah²,

Tayebi³

2019

MMEP

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A numerical study based on the analysis of laminar natural convection in a concentric cylindrical annulus heat exchanger is investigated. The operating fluid is confined between two horizontal concentric cylinders which are maintained at different uniform temperatures. The governing equations the flow (of continuity, momentum and energy) are numerically solved via finite volume method (FVM). The investigation is performed for Rayleigh number and volume fraction of nanoparticles in the range of 10 3-10 5 and 0-12%, respectively. The effective thermal conductivity and viscosity of the nanofluids mixture are calculated via Maxwell-Garnett model (MG-model) and Brinkman model, respectively. The results are presented in terms of isotherms, fluid flow patterns and Nusselt number distribution function of Rayleigh number and the volume fraction of silver nanoparticles. The results are also discussed in detail. Results are discussed in detail. It is found that a very good agreement exists between the present results and those from the literature. It is found that fluid flow intensity and heat transfer rate increase with the increase of the nanoparticles volume fraction and Rayleigh number, Also, the thermal effectiveness depends on the Rayleigh number and the volume fraction of the nanoparticles.

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Unsteady natural convection and statistical analysis in a CNT–water filled cavity with non-isothermal heating

Cited by 33 publications

References 23 publications

Self-propelled nanofluids a path to a highly effective coolant

Self-propelled nanofluids a path to a highly effective coolant

Numerical simulation of three-dimensional thermo-solutal convection of micropolar multi-walled carbon nanotubes water nanofluid stabilized by lignin and sodium polycarboxylate

Improvement of Free Convection Heat Transfer in a Concentric Cylindrical Annulus Heat Exchanger Using Nanofluid

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