Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls
Gas flow and heat transfer in confined geometries at micro-and nanoscales differ considerably from those at macro-scales, mainly due to nonequilibrium effects such as velocity slip and temperature jump. Nonequilibrium effects increase with a decrease in the characteristic length-scale of the fluid f...
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doaj-16b518fc20104d329e056a423ff386b42021-04-16T23:05:45ZengMDPI AGApplied Sciences2076-34172021-04-01113602360210.3390/app11083602Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal WallsAmin Ebrahimi0Vahid Shahabi1Ehsan Roohi2Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The NetherlandsDepartment of Mechanical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Khorasan Razavi P.O. Box 91775-1111, IranState Key Laboratory for Strength and Vibration of Mechanical Structures, International Center for Applied Mechanics, School of Aerospace Engineering, Xi’an Jiaotong University, Xianning West Road, Beilin District, Xi’an 710049, ChinaGas flow and heat transfer in confined geometries at micro-and nanoscales differ considerably from those at macro-scales, mainly due to nonequilibrium effects such as velocity slip and temperature jump. Nonequilibrium effects increase with a decrease in the characteristic length-scale of the fluid flow or the gas density, leading to the failure of the standard Navier–Stokes–Fourier (NSF) equations in predicting thermal and fluid flow fields. The direct simulation Monte Carlo (DSMC) method is employed in the present work to investigate pressure-driven nitrogen flow in divergent microchannels with various divergence angles and isothermal walls. The thermal fields obtained from numerical simulations are analysed for different inlet-to-outlet pressure ratios (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>Π</mi><mo>≤</mo><mn>2</mn><mo>.</mo><mn>5</mn></mrow></semantics></math></inline-formula>), tangential momentum accommodation coefficients, and Knudsen numbers (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>.</mo><mn>05</mn><mo>≤</mo><mi>Kn</mi><mo>≤</mo><mn>12</mn><mo>.</mo><mn>5</mn></mrow></semantics></math></inline-formula>), covering slip to free-molecular rarefaction regimes. The thermal field in the microchannel is predicted, heat-lines are visualised, and the physics of heat transfer in the microchannel is discussed. Due to the rarefaction effects, the direction of heat flow is largely opposite to that of the mass flow. However, the interplay between thermal and pressure gradients, which are affected by geometrical configurations of the microchannel and the applied boundary conditions, determines the net heat flow direction. Additionally, the occurrence of thermal separation and cold-to-hot heat transfer (also known as anti-Fourier heat transfer) in divergent microchannels is explained.https://www.mdpi.com/2076-3417/11/8/3602Poiseuille micro-flowthermal field analysisheat flowdivergent microchanneldirect simulation Monte Carlo (DSMC) |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Amin Ebrahimi Vahid Shahabi Ehsan Roohi |
spellingShingle |
Amin Ebrahimi Vahid Shahabi Ehsan Roohi Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls Applied Sciences Poiseuille micro-flow thermal field analysis heat flow divergent microchannel direct simulation Monte Carlo (DSMC) |
author_facet |
Amin Ebrahimi Vahid Shahabi Ehsan Roohi |
author_sort |
Amin Ebrahimi |
title |
Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls |
title_short |
Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls |
title_full |
Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls |
title_fullStr |
Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls |
title_full_unstemmed |
Pressure-Driven Nitrogen Flow in Divergent Microchannels with Isothermal Walls |
title_sort |
pressure-driven nitrogen flow in divergent microchannels with isothermal walls |
publisher |
MDPI AG |
series |
Applied Sciences |
issn |
2076-3417 |
publishDate |
2021-04-01 |
description |
Gas flow and heat transfer in confined geometries at micro-and nanoscales differ considerably from those at macro-scales, mainly due to nonequilibrium effects such as velocity slip and temperature jump. Nonequilibrium effects increase with a decrease in the characteristic length-scale of the fluid flow or the gas density, leading to the failure of the standard Navier–Stokes–Fourier (NSF) equations in predicting thermal and fluid flow fields. The direct simulation Monte Carlo (DSMC) method is employed in the present work to investigate pressure-driven nitrogen flow in divergent microchannels with various divergence angles and isothermal walls. The thermal fields obtained from numerical simulations are analysed for different inlet-to-outlet pressure ratios (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>Π</mi><mo>≤</mo><mn>2</mn><mo>.</mo><mn>5</mn></mrow></semantics></math></inline-formula>), tangential momentum accommodation coefficients, and Knudsen numbers (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>.</mo><mn>05</mn><mo>≤</mo><mi>Kn</mi><mo>≤</mo><mn>12</mn><mo>.</mo><mn>5</mn></mrow></semantics></math></inline-formula>), covering slip to free-molecular rarefaction regimes. The thermal field in the microchannel is predicted, heat-lines are visualised, and the physics of heat transfer in the microchannel is discussed. Due to the rarefaction effects, the direction of heat flow is largely opposite to that of the mass flow. However, the interplay between thermal and pressure gradients, which are affected by geometrical configurations of the microchannel and the applied boundary conditions, determines the net heat flow direction. Additionally, the occurrence of thermal separation and cold-to-hot heat transfer (also known as anti-Fourier heat transfer) in divergent microchannels is explained. |
topic |
Poiseuille micro-flow thermal field analysis heat flow divergent microchannel direct simulation Monte Carlo (DSMC) |
url |
https://www.mdpi.com/2076-3417/11/8/3602 |
work_keys_str_mv |
AT aminebrahimi pressuredrivennitrogenflowindivergentmicrochannelswithisothermalwalls AT vahidshahabi pressuredrivennitrogenflowindivergentmicrochannelswithisothermalwalls AT ehsanroohi pressuredrivennitrogenflowindivergentmicrochannelswithisothermalwalls |
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1721524075543658496 |