Lorentz force impact on hybrid nanofluid within a porous tank including entropy generation

https://doi.org/10.1016/j.icheatmasstransfer.2020.104635Get rights and content

Abstract

Computational analysis was performed to scrutinize the MHD hybrid nanofluid free convection with combination of entropy generation within a permeable tank. Flow pattern was reported for wide range of scrutinized parameters. Outputs reveal that convective flow intensity augments with rise of permeability and stronger thermal plume generates. Isotherms reveal that growth of Lorentz force leads to less intensive heating and isotherm with less distortion appears. Insertion of magnetic field makes weaker convective flow and lower temperature gradient. As temperature of heat source reduces with rise of Hartmann number, Nuave decreases and greater exergy loss occurs. Lower surface temperature is achieved with rise of permeability of zone which is led to greater Nuave.

Introduction

Entropy enhancement is utilized to clarify the presentation of different frameworks in modern and building applications. Hence as of late various researchers and engineers have concentrated they're focused on entropy streamlining issues. Entropy is imitative from Greek word entropia, which implies that “a moving in the direction of” or “change”. Entropy calculation is essential as it classifies the parameters for energy loss. Bejan [1] presented the idea of an entropy optimization problem. Ellahi et al. [2] explored the impact of entropy generation on mixed convective nanofluid flow flows. Compound turbulator has been employed by Sheikholeslami et al. [3] to augment mixing of nanomaterial within a pipe. They proved that thermal irreversibility enhances with rise of secondary flow. Nanofluid is a mixture of basis fluid and suspended nonmetallic or metallic nanoparticles lower than 100 nm. Before introducing nanomaterial, to augment the rate of conductivity of typical fluids, the suspension of micrometer o millimeter sized solid particles were investigated while the resulted sedimentation caused pressure fall in the stream channel to increase. Nanomaterials have gained much importance due to their wide-range applications in thermal insulations, food dispensation, geothermal processes, microelectronic device technologies, thermal power plants, and microelectronics [[4], [5], [6], [7], [8], [9], [10], [11]]. Colloidal suspension of nano-sized particles (oxides, metals, carbides, or carbon nanotubes) and conventionally working materials (water, oil and ethylene glycol) are known as nanomaterial. Nanomaterial has innovative behaviors that make them more significant in various applications in thermal transmission like medicinal procedures, domestic refrigerator, hybrid-powered engines, fuel cells, heat exchanger and automobile thermal management.

A complete study on the efficiency of heat conversion in the solar collector with the nanofluid was carried out by Chen et al. [12]. They found that the performance of photothermal conversion in the collector increased by 96.93% and 52% at 30 °C and 75 °C respectively which was very suitable fluid for solar collectors which have direct absorption in low-temperatures. Mebarek Oudina [13,14] scrutinized nanomaterial behavior inside an annulus with various configurations of heat sources. They utilized numerical approach and presented stability analysis. Mesoscopic approach for scrutinizing nanomaterial flow through porous domain was presented by Sheikholeslami et al. [15]. They employed Lorentz force to control the flow style within a cavity. Yadav et al. [16] demonstrated the effect of vertical external forces on the instability of the nanofluid. The authors considered a constant temperature at the boundaries, meanwhile, the nanoparticles flux was considered to be zero at the boundaries. Numerically, laminar free convection in a hole with an adiabatic square obstacle has been investigated by Kalidasan and Kanna [17]. The hole was full of hybrid nanomaterial. Based on their results, for all amounts of Re, there was a reduction in the strength of the primary vortex as adding nanoparticles. Alumina behavior within a porous region has been scrutinized by Sheikholeslami [18] and He concluded that lower temperature gradient can be achieved in absence of Lorentz forces. Chougule et al. [19] found that due to low connection of nano-powders, pressure drop is very significant in the round tube when they used nanofluid CNTs rather than pure water. Moreover, round tube with coil inserts improve better Nusselt number because the rate of energy exchange increase due to this fact that nano-powders have random and irregular motion in the fluids. Zhao et al. [20] have worked on the stability analysis of bioconvection and system was numerically solved using the one-term Galerikan technique. Their study implied that the layer becomes more unstable because of the heating and the stability can be achieved by increasing cell eccentricity. Ding et al. [21] described that nanofluids based on CNTs depends on the temperature of base fluid, and establish that when the fluid temperature is 25 °C, the thermal conductivity can be increased by up to 30%. The efficiency of alumina nanomaterial streaming within a complex tank has been investigated by Zhai et al. [22]. Improving hydrodynamic as well as temperature boundary layer can be disordered by periodic disorder of such holes, resulting to an improvement in temperature gradient. Copper made duct with alumina working fluid has been utilized by Sohel et al. [23] for surveying frictional and thermal entropy production. The thermal entropy production relies on the heat flux rate and fluid temperature. The frictional entropy production is associated with frictional coefficient and the nanofluid's velocity. In order to raise the mass concentration as well as stream rate, the friction entropy production increases while the thermal entropy declines. Numerically, the design examination of a swirl stream micro channel for great heat flux usages has been investigated by Hartmann-Priesnitz et al. [24] who modeled the operant fluids as Cu-H2O nanomaterial in laminar stream. Based on their results, as the height of microchannel decreases, the boundary layers might be combined and the entrainment impact is vanished. As a result, the total heat flux might not always grow when stream passage field reduces.

According to literature survey, magnetic force can be utilized as effective control parameter for nanofluid flow pattern. So, analysis of MHD hybrid nanomaterial flow in appearance of buoyancy forces is considered in this article. The goal of this investigation is a numerical analysis of Lorentz force effect on entropy generation and thermal treatment of nanomaterial. After providing present model and numerical approach details, outputs in terms of profiles and contours were demonstrated.

Section snippets

Problematic description

The corresponding boundary conditions and physical model were depicted in Fig. 1. Two inclined straight walls are adiabatic and up wall are kept cold temperature but the bottom surface is experienced uniform heat flux. Closed tank is filled with hybrid nanomaterial (Fe3O4- MWCNT)/H2O and properties was summarized in Ref. [25]. Thermal equilibrium exists between components of carrier fluid and properties were derived according to empirical correlations [25]. All surfaces are impermeable and

Results and discussion

Free convection is a main phenomenon of various engineering devices and closed domain is most practical shape of this devices. So, in current article, closed porous tank with insertion of magnetic field was presented. As mentioned in previous part, CVFEM has been employed to gain the solution and computational outputs in terms of contours and 3D shape distributions were reported in results. Not only the thermal behavior but also the irreversibility was described in current research.

Flow pattern

Conclusions

Computational report for entropy generation and free convection of hybrid nanomaterial with insert of magnetic force was investigated in current article. The equations were solved numerically and outputs were demonstrated in terms of profiles and contours. Computational outputs prove that the growth of permeability reduces the exergy loss while Nuave augments with rise of Da. In addition, it can be reported that impose of Ha makes the Be to increase which is attributed to greater temperature

Declaration of Competing Interests

The author declares that they have no competing interest.

Acknowledgements

The authors acknowledge the financial support provided by the Center of Excellence in Theoretical and Computational Science (TaCS-CoE), KMUTT.

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