Diminishing vortex intensity and improving heat transfer by applying magnetic field on an injectable slip microchannel c
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Diminishing vortex intensity and improving heat transfer by applying magnetic field on an injectable slip microchannel containing FMWNT/ water nanofluid Aliakbar Karimipour1 · Dariush Bahrami2 · Rasool Kalbasi3 · Azam Marjani4,5 Received: 15 June 2020 / Accepted: 14 September 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract In this study, heat transfer and entropy generation were investigated in a microchannel containing FMWNT/water nanofluids given the slip condition. The main focus was on utilizing injection technique in the presence of the magnetic field. The injection from the upper high-temperature wall was incorporated into the flow field. Injection at high Reynolds number causes vortex formation, which ultimately reduces local heat transfer in the adjacent injection zone. By applying the magnetic field, the vortex intensity as well as boundary layer thickness was diminished which in turn improved the heat transfer. Based on numerical results, at higher nanoparticle volume fraction, the effect of the magnetic field on heat transfer enhancement was amplified. Moreover, at higher Reynolds numbers, the magnetic field efficacy is more obvious. The highest heat transfer occurred at the highest values of the Hartmann and Reynolds numbers and eventually the nanoparticle volume fraction. Owing to applying the magnetic field on the injectable microchannel containing nanofluid, heat transfer improvement can reach up to 79%. From the second law prospective, the entropy generation intensified by 82.8%. Keywords Microchannel · Magnetic field · Injection · Heat transfer · Nanofluid · Slip · Entropy generation List of symbols Bo Magnetic field strength (T) h Microchannel height (mm) H Dimensionless microchannel Ha Hartmann number l Microchannel length (mm) L Dimensionless microchannel p̄ Pressure (Pa) Re Reynolds number Ṡ f Viscous entropy generation * Azam Marjani [email protected] 1
Institute of Research and Development, Duy Tan University, Da Nang 550000, Vietnam
2
Department of Mechanical Engineering, Shahrekord University, Shahrekord, Iran
3
Depratment of Mechanical Engineering, Najaf Abad University, Esfahan, Iran
4
Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Vietnam
5
Faculty of Applied Sciences, Ton Duc Thang University, Ho Chi Minh City, Vietnam
Ṡ h Thermal entropy generation Ṡ t Total entropy generation U Dimensionless velocity ) ( horizontal us Slip velocity ms
Us Dimensionless slip velocity Sr Ratio of total entropy with magnetic field to total entropy without magnetic field
Greek symbols 𝛽 Slip coefficient (mm) 𝛽 ∗ Dimensionless slip coefficient 𝜑 Volume fraction of nanoparticles (%) θ Dimensionless temperature ( 2) 𝛼 Thermal diffusivity ms S 𝜎nf Nanofluid electrical conductivity cm
Super and subscripts ave Average h Hot c Cold nf Nanofluid
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Introduction Today, electronic components are manufactured in very small dimensions. In addition, the power consum
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