Entropy Generation Between Two Rotating Cylinders with Magnetohydrodynamic Flow Using Nanofluids

In this paper, the effects of uncertainties in physical properties on predicting entropy generation for a steady laminar flow of Al2O3–ethylene glycol nanofluid (0≤φ≤6 %) between two concentric rotating cylinders are investigated. For this purpose, six different models by combining of three relations for thermal conductivity (Bruggeman, Hamilton–Crosser, and Yu–Choi) and two relations for dynamic viscosity (Brinkman and Maiga et al.) are applied. The governing equations with reasonable assumptions in cylindrical coordinates are simplified and solved to obtain analytical expressions for average entropy generation (NS)ave and average Bejan number (Be)ave. The results show that, when the contribution of heat transfer to entropy generation for the base fluid is dominant, a critical radius ratio (ΠC) can be determined at which all six models predict the reduction in entropy generation with increases of volume fraction of nanoparticles. It is also found that, when the contribution of viscous effects to entropy generation is adequately high for the base fluid (φ=0), all models predict the increase of entropy generation with increases of particle loading.

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Optimization of a magnetohydrodynamic flow based on the entropy generation minimization method

International Communications in Heat and Mass Transfer ◽

10.1016/j.icheatmasstransfer.2005.12.003 ◽

2006 ◽

Vol 33 (3) ◽

pp. 295-301 ◽

Cited By ~ 16

Author(s):

Guillermo Ibáñez ◽

Sergio Cuevas ◽

Mariano López de Haro

Keyword(s):

Entropy Generation ◽

Magnetohydrodynamic Flow ◽

Minimization Method ◽

Entropy Generation Minimization

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Analysis of the forced convection of two-phase Ferro-nanofluid flow in a completely porous microchannel containing rotating cylinders

Scientific Reports ◽

10.1038/s41598-021-97152-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Hamidreza Aghamiri ◽

Mohammadreza Niknejadi ◽

Davood Toghraie

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Porous Medium ◽

Forced Convection ◽

Entropy Generation ◽

Volume Fraction ◽

Rotating Cylinders ◽

Nanofluid Flow ◽

Two Phase ◽

Porosity Percentage

AbstractIn the present work, the forced convection of nanofluid flow in a microchannel containing rotating cylinders is investigated in different geometries. The heat flux applied to the microchannel wall is 10,000 W m−2. The effects of Reynolds number, the volume fraction of nanoparticles, and the porosity percentage of the porous medium are investigated on the flow fields, temperature, and heat transfer rate. Reynolds number values vary from Re = 250–1000, non-dimensional rotational velocities 1 and 2, respectively, and volume fraction of nanoparticles 0–2%. The results show that increasing the velocity of rotating cylinders increases the heat transfer; also, increasing the Reynolds number and volume fraction of nanoparticles increases the heat transfer, pressure drop, and Cf,ave. By comparing the porosity percentages with each other, it is concluded that due to the greater contact of the nanofluid with the porous medium and the creation of higher velocity gradients, the porosity percentage is 45% and the values of are 90% higher than the porosity percentage. Comparing porosity percentages with each other, at porosity percentage 90% is greater than at porosity percentage 45%. On the other hand, increasing the Reynolds number reduces the entropy generation due to heat transfer and increases the entropy generation due to friction. Increasing the volume fraction of nanoparticles increases the entropy generations due to heat transfer and friction.

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