Some considerations on thermal boundary condition of slip flow

Accurate modeling of gas microvection is crucial for a lot of MEMS applications (microheat exchangers, pressure gauges, fluidic microactuators for active control of aerodynamic flows, mass flow and temperature microsensors, micropumps, and microsystems for mixing or separation for local gas analysis, mass spectrometers, vacuum, and dosing valves…). Gas flows in microsystems are often in the slip flow regime, characterized by a moderate rarefaction with a Knudsen number of the order of 10 À2 -10 À1 . In this regime, velocity slip and temperature jump at the walls play a major role in heat transfer. This paper presents a state of the art review on convective heat transfer in microchannels, focusing on rarefaction effects in the slip flow regime. Analytical and numerical models are compared for various microchannel geometries and heat transfer conditions (constant heat flux or constant wall temperature). The validity of simplifying assumptions is detailed and the role played by the kind of velocity slip and temperature jump boundary conditions is shown. The influence of specific effects, such as viscous dissipation, axial conduction and variable fluid properties is also discussed.

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“…(43) can be found in Ref. [57]. This condition has not been, however, often implemented in slip flow heat transfer analysis.…”

Section: Effects Of Viscousmentioning

confidence: 99%

Gas Microflows in the Slip Flow Regime: A Critical Review on Convective Heat Transfer

Colin

2011

Journal of Heat Transfer

132

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Section: New Temperature Jump Condition In Cfdmentioning

confidence: 99%

“…The heat conduction generating by the sliding friction (shear work) should be involved in conservation of energy at the surface. It has been considered to contribute to the component of the total conduction of heat at the surface that is due to the approaching molecules [20], seen in Figure 1. The shear work per unit area is -(S • (n • Π ))• (u − u w ) (positive inwards), where u is the gas velocity at near the surface; the symbol "•" denotes the inner product.…”

Section: New Temperature Jump Condition In Cfdmentioning

confidence: 99%

New temperature jump boundary condition in high-speed rarefied gas flow simulations

Loc

et al. 2017

Vietnam J. Mech.

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Abstract. The effect of the sliding friction has been important in calculating the heat flux of gas flow from the surface since there is some slip over the surface. There has not been any the temperature jump condition including the sliding friction part so far. In this paper, we will propose a new temperature jump condition that includes the sliding friction. Our new temperature jump condition will be evaluated for NACA0012 micro-airfoil in highspeed rarefied gas flow simulations using the CFD method, which solves the NavierStokes equations within the OpenFOAM framework with working gas as air. The airfoil case is simulated with various Knudsen numbers from 0.026 to 0.26, and the angles-ofattack (AOAs) from 0-deg to 20-deg. The surface gas temperatures predicting by our new temperature jump condition give good agreements with the DSMC data, especially the NACA0012 micro-airfoil cases with the high Knudsen numbers, Kn = 0.1, and Kn = 0.26 with AOA = 20-deg. for the lower surface.

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“…The authors usually considered either a constant heat flux boundary condition or an isothermal condition to analyze the heat transfer characteristics of gaseous flows in various geometries such as: parallel plate microchannels and micropipe. In addition to the effect of rarefaction [10][11][12][13][14], various issues such as: viscous dissipation [15][16][17][18][19][20], axial conduction [21,22], thermal creep [23,24], compressibility [25][26][27][28], shear work [29][30][31], roughness [32,33], fluid property variation [34,35], and thermal boundary conditions affect the heat transfer characteristics of gaseous flows in microdevices. However, it is observed that viscous dissipation acts as an internal heat source in the fluid and significantly affects the temperature field and subsequently the Nusselt Number.…”

Section: Introductionmentioning

confidence: 99%

“…The effect of shear work on boundary is mainly due to the slip velocity, while it is considered to be zero at macroscale. The shear work is found to play a significant role at solid boundaries in small-scale gaseous flows especially when the slip effect is present [29][30][31]. Studies have been reported that consider the role of surface roughness on heat transfer performance [32,33].…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Analysis of Convective Heat Transfer in Parallel Plate Microchannel with Viscous Dissipation and Constant Heat Flux Boundary Conditions

Kushwaha

Sahu

2016

J. Inst. Eng. India Ser. C

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This paper reports the hydrodynamically and thermally fully developed, laminar, incompressible, forced convective heat transfer characteristics of gaseous flows through a parallel plate microchannel with different constant heat flux boundary conditions. The first order velocity slip and viscous dissipation effects are considered in the analysis. Here, three different thermal boundary conditions such as: both plates kept at different constant heat fluxes, both plates kept at equal constant heat fluxes and one plate kept at constant heat flux and other one insulated are considered for the analysis. The deviation in Nusselt number between the model that considers both first order velocity slip and temperature jump and the one that considers only velocity slip is reported. Also, the effect of various heat flux ratios on the Nusselt number is reported in this analysis. In addition, the deviation in Nusselt number between first and second order slip model is discussed in this study.

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Some considerations on thermal boundary condition of slip flow

Cited by 54 publications

References 17 publications

Gas Microflows in the Slip Flow Regime: A Critical Review on Convective Heat Transfer

Gas Microflows in the Slip Flow Regime: A Critical Review on Convective Heat Transfer

New temperature jump boundary condition in high-speed rarefied gas flow simulations

Comprehensive Analysis of Convective Heat Transfer in Parallel Plate Microchannel with Viscous Dissipation and Constant Heat Flux Boundary Conditions

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