scholarly journals Viscous dissipation and temperature dependent viscosity effects in simultaneously developing flows in flat microchannels with convective boundary conditions

2006 ◽  
Author(s):  
S. Del Giudice ◽  
S. Savino ◽  
C. Nonino
Keyword(s):  
Boundary Conditions ◽  
Viscous Dissipation ◽  
Convective Boundary Conditions ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Convective Boundary ◽  
Viscosity Effects ◽  
Dependent Viscosity

Entrance, Viscous Dissipation and Temperature Dependent Viscosity Effects in Microchannel Flows With Convective Boundary Conditions

2006 ◽  
Author(s):  
C. Nonino ◽  
S. Del Giudice ◽  
S. Savino
Keyword(s):  
Boundary Conditions ◽  
Viscous Dissipation ◽  
Circular Cross Section ◽  
Laminar Flows ◽  
Projection Algorithm ◽  
Convective Boundary Conditions ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Convective Boundary ◽  
Dependent Viscosity

The effects of viscous dissipation and temperature dependent viscosity in simultaneously developing laminar flows of liquids in straight microchannels of circular cross-section are studied with reference to convective boundary conditions. Viscosity is assumed to vary linearly with temperature, in order to allow a parametric investigation, while the other fluid properties are held constant. A finite element procedure, based on a projection algorithm, is employed for the step-by-step solution of the parabolized momentum and energy equations. Axial distributions of the local overall Nusselt number and of the apparent Fanning friction factor are presented with reference to both heating and cooling conditions for three different values of the Biot number. Examples of temperature profiles at different axial locations are also shown.

Temperature-Dependent Viscosity and Viscous Dissipation Effects in Simultaneously Developing Flows in Microchannels With Convective Boundary Conditions

2006 ◽  
Vol 129 (9) ◽  
pp. 1187-1194 ◽  
Author(s):  
C. Nonino ◽  
S. Del Giudice ◽  
S. Savino
Keyword(s):  
Boundary Conditions ◽  
Viscous Dissipation ◽  
Laminar Flows ◽  
Projection Algorithm ◽  
Convective Boundary Conditions ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Convective Boundary ◽  
Radial Temperature ◽  
Dependent Viscosity

The effects of viscous dissipation and temperature dependent viscosity in simultaneously developing laminar flows of liquids in straight microchannels are studied with reference to convective boundary conditions. Two different geometries, namely the circular tube and the parallel plate channel, are considered. Viscosity is assumed to vary with temperature according to an exponential relation, while the other fluid properties are held constant. A finite element procedure, based on a projection algorithm, is employed for the step-by-step solution of the parabolized momentum and energy equations. Axial distributions of the local overall Nusselt number and of the apparent Fanning friction factor are presented with reference to both heating and cooling conditions for two different values of the Biot number. Examples of radial temperature profiles at different axial locations and of axial distributions of centerline velocity and temperature are also shown.

Analysis of the Effects of Joule Heating and Viscous Dissipation on Combined Pressure-Driven and Electrokinetic Flows in a Two-Parallel Plate Channel with Unequal Constant Temperatures

2018 ◽  
Vol 233 (4) ◽  
pp. 871-879 ◽  
Author(s):  
Harshad Sanjay Gaikwad ◽  
Pranab Kumar Mondal ◽  
Dipankar Narayan Basu ◽  
Nares Chimres ◽  
Somchai Wongwises
Keyword(s):  
Viscous Dissipation ◽  
Entropy Generation ◽  
Joule Heating ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Local Entropy ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Dependent Viscosity ◽  
Local Entropy Generation

In this article, we perform an entropy generation analysis for the micro channel heat sink applications where the flow of fluid is actuated by combined influences of applied pressure gradient and electric field under electrical double layer phenomenon. The upper and lower walls of the channels are kept at different constant temperatures. The temperature-dependent viscosity of the fluid is considered and hence the momentum equation and energy equations are coupled in this study. Also, a hydrodynamic slip condition is employed on the viscous dissipation. For complete analysis of the entropy generation, we use a perturbation approach with lubrication approximation. In this study, we discuss the results depicting variations in the velocity and temperature distributions and their effect on local entropy generation rate and Bejan number in the system. It can be summarized from this analysis that the enhanced velocity gradients in the flow field due to combined effect of temperature-dependent viscosity and Joule heating and viscous dissipative effects, leads to an enhancement in the local entropy generation rate in the system.

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