Heat Transfer Enhancement, Secondary Flows and Change of Type of Vorticity Transport in Non-Circular Tube Flow of Non-linear Viscoelastic Fluids

Siginer Dennis, Mario F. Letelier

Research output: Contribution to conferencePaper

Abstract

Heat transfer enhancement in steady pressure gradient driven laminar flow of a class of non-linear viscoelastic fluids in straight tubes of non-circular cross-section at constant temperature is discussed together with the flow structure, and the physics is clarified. The variation of the average Nusselt number Nu with the Weissenberg Wi and Reynolds Re numbers in cross-sections with n axes of symmetry is analysed. A continuous one-to-one mapping is used to obtain arbitrary tube contours from a base tube contour ∂D0. The analytical method presented is capable of predicting the velocity and temperature fields in tubes with arbitrary cross-section. The base flow is the Newtonian field and is obtained at the lowest order. Heat transfer enhancements represented by average Nusselt numbers of an order of magnitude larger as compared to their Newtonian counterparts are predicted as a function of the Reynolds and Weissenberg numbers even for slightly non-Newtonian dilute fluids. The asymptotic independence of Nu = f(Pe,Wi) → Nu= f(Pe) with increasing Wi is shown analytically for the first time. The implications on the heat transfer enhancement of the change of type of the vorticity equation is discussed in particular for slight deviations from Newtonian behaviour where a rapid rise in enhancement seems to occur as opposed to the behaviour for larger values of the Weissenberg number where the rate of increase is much slower. The coupling between viscoelastic and inertial nonlinearities is crucial to enhancement. Fluid vorticity will change type when the velocity in the centre of the tube is larger than a critical value defined by the propagation of the shear waves. The asymptotic independence of Nu from elasticity with increasing Wi is related to the thickness of the supercritical region around the tube axis controlled by the interaction of the viscoelastic Mach number M and the Elasticity number E. The physics of the interaction of the effects of the Elasticity E, Viscoelastic Mach M, Reynolds Re and Weissenberg Wi numbers on generating the heat transfer enhancement is discussed.
Original languageEnglish
Pages1-8
DOIs
Publication statusPublished - 2008
Event5th European Thermal Sciences Conference - Eindhoven, Netherlands
Duration: May 18 2008May 22 2008

Conference

Conference5th European Thermal Sciences Conference
CountryNetherlands
CityEindhoven
Period5/18/085/22/08

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secondary flow
vorticity
heat transfer
tubes
augmentation
fluids
elastic properties
Nusselt number
cross sections
vorticity equations
base flow
physics
laminar flow
pressure gradients
Mach number
S waves
temperature distribution
velocity distribution
nonlinearity
interactions

Cite this

Dennis, Siginer ; Letelier, Mario F. / Heat Transfer Enhancement, Secondary Flows and Change of Type of Vorticity Transport in Non-Circular Tube Flow of Non-linear Viscoelastic Fluids. Paper presented at 5th European Thermal Sciences Conference, Eindhoven, Netherlands.
@conference{d291a444a787428d8a3461ceb92b5c74,
title = "Heat Transfer Enhancement, Secondary Flows and Change of Type of Vorticity Transport in Non-Circular Tube Flow of Non-linear Viscoelastic Fluids",
abstract = "Heat transfer enhancement in steady pressure gradient driven laminar flow of a class of non-linear viscoelastic fluids in straight tubes of non-circular cross-section at constant temperature is discussed together with the flow structure, and the physics is clarified. The variation of the average Nusselt number Nu with the Weissenberg Wi and Reynolds Re numbers in cross-sections with n axes of symmetry is analysed. A continuous one-to-one mapping is used to obtain arbitrary tube contours from a base tube contour ∂D0. The analytical method presented is capable of predicting the velocity and temperature fields in tubes with arbitrary cross-section. The base flow is the Newtonian field and is obtained at the lowest order. Heat transfer enhancements represented by average Nusselt numbers of an order of magnitude larger as compared to their Newtonian counterparts are predicted as a function of the Reynolds and Weissenberg numbers even for slightly non-Newtonian dilute fluids. The asymptotic independence of Nu = f(Pe,Wi) → Nu= f(Pe) with increasing Wi is shown analytically for the first time. The implications on the heat transfer enhancement of the change of type of the vorticity equation is discussed in particular for slight deviations from Newtonian behaviour where a rapid rise in enhancement seems to occur as opposed to the behaviour for larger values of the Weissenberg number where the rate of increase is much slower. The coupling between viscoelastic and inertial nonlinearities is crucial to enhancement. Fluid vorticity will change type when the velocity in the centre of the tube is larger than a critical value defined by the propagation of the shear waves. The asymptotic independence of Nu from elasticity with increasing Wi is related to the thickness of the supercritical region around the tube axis controlled by the interaction of the viscoelastic Mach number M and the Elasticity number E. The physics of the interaction of the effects of the Elasticity E, Viscoelastic Mach M, Reynolds Re and Weissenberg Wi numbers on generating the heat transfer enhancement is discussed.",
author = "Siginer Dennis and Letelier, {Mario F.}",
year = "2008",
doi = "DOI: 10.13140/RG.2.1.1990.4248",
language = "English",
pages = "1--8",
note = "5th European Thermal Sciences Conference ; Conference date: 18-05-2008 Through 22-05-2008",

}

Dennis, S & Letelier, MF 2008, 'Heat Transfer Enhancement, Secondary Flows and Change of Type of Vorticity Transport in Non-Circular Tube Flow of Non-linear Viscoelastic Fluids' Paper presented at 5th European Thermal Sciences Conference, Eindhoven, Netherlands, 5/18/08 - 5/22/08, pp. 1-8. https://doi.org/DOI: 10.13140/RG.2.1.1990.4248

Heat Transfer Enhancement, Secondary Flows and Change of Type of Vorticity Transport in Non-Circular Tube Flow of Non-linear Viscoelastic Fluids. / Dennis, Siginer; Letelier, Mario F.

2008. 1-8 Paper presented at 5th European Thermal Sciences Conference, Eindhoven, Netherlands.

Research output: Contribution to conferencePaper

TY - CONF

T1 - Heat Transfer Enhancement, Secondary Flows and Change of Type of Vorticity Transport in Non-Circular Tube Flow of Non-linear Viscoelastic Fluids

AU - Dennis, Siginer

AU - Letelier, Mario F.

PY - 2008

Y1 - 2008

N2 - Heat transfer enhancement in steady pressure gradient driven laminar flow of a class of non-linear viscoelastic fluids in straight tubes of non-circular cross-section at constant temperature is discussed together with the flow structure, and the physics is clarified. The variation of the average Nusselt number Nu with the Weissenberg Wi and Reynolds Re numbers in cross-sections with n axes of symmetry is analysed. A continuous one-to-one mapping is used to obtain arbitrary tube contours from a base tube contour ∂D0. The analytical method presented is capable of predicting the velocity and temperature fields in tubes with arbitrary cross-section. The base flow is the Newtonian field and is obtained at the lowest order. Heat transfer enhancements represented by average Nusselt numbers of an order of magnitude larger as compared to their Newtonian counterparts are predicted as a function of the Reynolds and Weissenberg numbers even for slightly non-Newtonian dilute fluids. The asymptotic independence of Nu = f(Pe,Wi) → Nu= f(Pe) with increasing Wi is shown analytically for the first time. The implications on the heat transfer enhancement of the change of type of the vorticity equation is discussed in particular for slight deviations from Newtonian behaviour where a rapid rise in enhancement seems to occur as opposed to the behaviour for larger values of the Weissenberg number where the rate of increase is much slower. The coupling between viscoelastic and inertial nonlinearities is crucial to enhancement. Fluid vorticity will change type when the velocity in the centre of the tube is larger than a critical value defined by the propagation of the shear waves. The asymptotic independence of Nu from elasticity with increasing Wi is related to the thickness of the supercritical region around the tube axis controlled by the interaction of the viscoelastic Mach number M and the Elasticity number E. The physics of the interaction of the effects of the Elasticity E, Viscoelastic Mach M, Reynolds Re and Weissenberg Wi numbers on generating the heat transfer enhancement is discussed.

AB - Heat transfer enhancement in steady pressure gradient driven laminar flow of a class of non-linear viscoelastic fluids in straight tubes of non-circular cross-section at constant temperature is discussed together with the flow structure, and the physics is clarified. The variation of the average Nusselt number Nu with the Weissenberg Wi and Reynolds Re numbers in cross-sections with n axes of symmetry is analysed. A continuous one-to-one mapping is used to obtain arbitrary tube contours from a base tube contour ∂D0. The analytical method presented is capable of predicting the velocity and temperature fields in tubes with arbitrary cross-section. The base flow is the Newtonian field and is obtained at the lowest order. Heat transfer enhancements represented by average Nusselt numbers of an order of magnitude larger as compared to their Newtonian counterparts are predicted as a function of the Reynolds and Weissenberg numbers even for slightly non-Newtonian dilute fluids. The asymptotic independence of Nu = f(Pe,Wi) → Nu= f(Pe) with increasing Wi is shown analytically for the first time. The implications on the heat transfer enhancement of the change of type of the vorticity equation is discussed in particular for slight deviations from Newtonian behaviour where a rapid rise in enhancement seems to occur as opposed to the behaviour for larger values of the Weissenberg number where the rate of increase is much slower. The coupling between viscoelastic and inertial nonlinearities is crucial to enhancement. Fluid vorticity will change type when the velocity in the centre of the tube is larger than a critical value defined by the propagation of the shear waves. The asymptotic independence of Nu from elasticity with increasing Wi is related to the thickness of the supercritical region around the tube axis controlled by the interaction of the viscoelastic Mach number M and the Elasticity number E. The physics of the interaction of the effects of the Elasticity E, Viscoelastic Mach M, Reynolds Re and Weissenberg Wi numbers on generating the heat transfer enhancement is discussed.

U2 - DOI: 10.13140/RG.2.1.1990.4248

DO - DOI: 10.13140/RG.2.1.1990.4248

M3 - Paper

SP - 1

EP - 8

ER -