scholarly journals Analytical solution of thermally developing microtube heat transfer including axial conduction, viscous dissipation, and rarefaction effects

2015 ◽  
Vol 67 ◽  
pp. 81-88 ◽  
Author(s):  
Murat Barışık ◽  
Almıla Güvenç Yazıcıoğlu ◽  
Barbaros Çetin ◽  
Sadık Kakaç
Keyword(s):  
Heat Transfer ◽  
Analytical Solution ◽  
Viscous Dissipation ◽  
Axial Conduction ◽  
Rarefaction Effects

Roughness Effect on the Heat Transfer Coefficient for Gaseous Flow in Microchannels

2010 ◽  
Author(s):  
Metin B. Turgay ◽  
Almila G. Yazicioglu ◽  
Sadik Kakac
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Nusselt Number ◽  
Flow Regime ◽  
Viscous Dissipation ◽  
Slip Flow ◽  
Roughness Height ◽  
Working Fluid ◽  
Axial Conduction ◽  
Slip Flow Regime

Effects of surface roughness, axial conduction, viscous dissipation, and rarefaction on heat transfer in a two–dimensional parallel plate microchannel with constant wall temperature are investigated numerically. Roughness is simulated by adding equilateral triangular obstructions with various heights on one of the plates. Air, with constant thermophysical properties, is chosen as the working fluid, and laminar, single-phase, developing flow in the slip flow regime at steady state is analyzed. Governing equations are solved by finite element method with tangential slip velocity and temperature jump boundary conditions to observe the rarefaction effect in the microchannel. Viscous dissipation effect is analyzed by changing the Brinkman number, and the axial conduction effect is analyzed by neglecting and including the corresponding term in the energy equation separately. Then, the effect of surface roughness on the Nusselt number is observed by comparing with the corresponding smooth channel results. It is found that Nusselt number decreases in the continuum case with the presence of surface roughness, while it increases with increasing roughness height in the slip flow regime, which is also more pronounced at low-rarefied flows (i.e., around Kn = 0.02). Moreover, the presence of axial conduction and viscous dissipation has increasing effects on heat transfer with increasing roughness height. Even in low velocity flows, roughness increases Nusselt number up to 33% when viscous dissipation is considered.

The Effect of Viscous Dissipation on Two-Dimensional Microchannel Heat Transfer

2006 ◽  
Author(s):  
Jennifer van Rij ◽  
Tim Ameel ◽  
Todd Harman
Keyword(s):  
Heat Transfer ◽  
Viscous Dissipation ◽  
Slip Flow ◽  
Second Order ◽  
Slip Boundary Conditions ◽  
Pressure Work ◽  
Axial Conduction ◽  
Slip Boundary ◽  
Nusselt Numbers ◽  
Slip Flow Regime

Microchannel convective heat transfer characteristics in the slip flow regime are numerically evaluated for two-dimensional, steady state, laminar, constant wall heat flux and constant wall temperature flows. The effects of Knudsen number, accommodation coefficients, viscous dissipation, pressure work, second-order slip boundary conditions, axial conduction, and thermally/hydrodynamically developing flow are considered. The effects of these parameters on microchannel convective heat transfer are compared through the Nusselt number. Numerical values for the Nusselt number are obtained using a continuum based three-dimensional, unsteady, compressible computational fluid dynamics algorithm that has been modified with slip boundary conditions. Numerical results are verified using analytic solutions for thermally and hydrodynamically fully developed flows. The resulting analytical and numerical Nusselt numbers are given as a function of Knudsen number, the first- and second-order velocity slip and temperature jump coefficients, the Peclet number, and the Brinkman number. Excellent agreement between numerical and analytical data is demonstrated. Viscous dissipation, pressure work, second-order slip terms, and axial conduction are all shown to have significant effects on Nusselt numbers in the slip flow regime.

Pressure Work and Viscous Dissipation Effects on Heat Transfer in a Parallel–Plate Microchannel Gas Flow

2017 ◽  
Vol 35 (02) ◽  
pp. 243-254 ◽  
Author(s):  
K. M. Ramadan
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Viscous Dissipation ◽  
Convective Heat ◽  
Parallel Plate ◽  
Gas Flow ◽  
Combined Effect ◽  
Rarefaction Analysis ◽  
Pressure Work ◽  
Axial Conduction

ABSTRACTConvective heat transfer in a parallel plate microchannel gas flow is investigated analytically and numerically, considering the effects of viscous dissipation, pressure work, shear work, axial conduction and rarefaction. Analysis is performed with constant wall temperature and constant wall heat flux boundary conditions for both gas cooling and heating. The results presented demonstrate the significance of the combined effect of pressure work and viscous dissipation, shear work, rarefaction degree and axial conduction on microchannel convective heat transfer, in both the thermally developing and fully developed flow regions. Viscous dissipation and pressure work in a pressure-driven microchannel gas flow are of comparable magnitudes and may not be neglected from the energy equation. The shear work at the wall, which is effectively the combined effect of viscous dissipation and pressure work, needs to be included in the Nusselt number for better predictions of heat transfer.

Numerical Investigation of the Viscous Dissipation Term on 2D Heat Transfer

2014 ◽  
Vol 348 ◽  
pp. 279-284
Author(s):  
M.D. de Campos ◽  
E.C. Romão ◽  
L.F. Mendes de Moura
Keyword(s):  
Heat Transfer ◽  
Temperature Field ◽  
Velocity Field ◽  
Finite Difference ◽  
Analytical Solution ◽  
Finite Difference Method ◽  
Viscous Dissipation ◽  
Heat Transfer Equation ◽  
Dissipation Term ◽  
High Order Finite Difference

In this paper are analyzed, using high-order finite difference method, applications in which the viscous dissipation term can be neglected or not in the heat transfer equation. Some examples using various numerical values for the velocity field show that the viscous dissipation does not affect significantly the temperature field. Using the L2 norm, the numerical solution is compared with some examples that have an analytical solution.

Analysis of Single Phase Convective Heat Transfer in Microchannels With Variable Thermal Conductivity and Viscosity

2010 ◽  
Author(s):  
Arif Cem Go¨zu¨kara ◽  
Almıla G. Yazıcıoglu ◽  
Sadık Kakac¸
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Viscous Dissipation ◽  
Gas Flow ◽  
Single Phase ◽  
Variable Thermal Conductivity ◽  
Parallel Plates ◽  
Scaling Effects ◽  
Axial Conduction ◽  
Temperature Variable

The need for maximizing the performance of micro-mechanical systems and electronic components has resulted in a trend of minimization. Minimized sizes and dimensions have come along with a complex heat transfer and fluid problem within these devices and components. For a variety of fields in which these devices are used, such as; biomedicine, micro fabrication, and optics, fluid flow and heat transfer at the microscale needs to be understood and modeled with an acceptable reliability. In general, models are prepared by making some extensions to the conventional theories by including the scaling effects that become important for microscale. Studies performed in the last decade have shown that, some of the effects that are thought to become significant for a microscale gas flow are; axial conduction, viscous dissipation, and rarefaction. In addition to these effects, the temperature variable thermal conductivity and viscosity may become important in microscale gas flow due to the high temperature gradients that may exist in the fluid. Therefore, effects of variable thermal conductivity and viscosity in microscale gas flow and convection heat transfer are investigated in this study. For this purpose, simultaneously developing, single phase, laminar and incompressible air flow in a micro gap between parallel plates is numerically analyzed. In the analyses, scaling effects such as rarefaction, viscous dissipation, and axial conduction are taken into account in addition to the temperature variable thermal conductivity and viscosity.

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