On the enhancement of heat transfer in pulsating combustion flows
(1998) 11th International Heat Transfer Conference In HEAT TRANSFER VOL 5  GENERAL PAPERS. p.381386 Abstract
 It has been observed and reported that in pulse combustors of Helmholtz type the heat transfer is two to five times higher than expected. From experiments, where the temperature profile in the tail pipe of a pulse combustor has been measured, we have no indication why the heat transfer should be enhanced. In the tail pipe of a pulse combustor the radial component of the temperature gradient vanishes in the main part of the of the crosssection of the tail pipe except close to the boundary of the pipe. Evidently, a temperature drop along the tail pipe of up to 500 degrees C/m, indicates that the classical linear constitutive assumption of heat conduction, i.e. Fourier's law, is incapable of describing the phenomenon observed. A powerful... (More)
 It has been observed and reported that in pulse combustors of Helmholtz type the heat transfer is two to five times higher than expected. From experiments, where the temperature profile in the tail pipe of a pulse combustor has been measured, we have no indication why the heat transfer should be enhanced. In the tail pipe of a pulse combustor the radial component of the temperature gradient vanishes in the main part of the of the crosssection of the tail pipe except close to the boundary of the pipe. Evidently, a temperature drop along the tail pipe of up to 500 degrees C/m, indicates that the classical linear constitutive assumption of heat conduction, i.e. Fourier's law, is incapable of describing the phenomenon observed. A powerful coupling between the oscillating velocity field and the oscillating temperature field might be able to explain the observed enhanced heat conduction.
In Fourier's law neither a direct dependence of the heat conduction on the velocity and the velocity gradient, nor an interaction between the velocity and temperature field is given. A first extension would be to introduce a more general constitutive relation for the heat conduction vector. For that reason, in order to describe the observed phenomenon, a new nonlinear constitutive relation for the heat conduction vector has been suggested. An additional term, dependent on the velocity gradient operating on the temperature gradient, will effect the heat transfer.
To be able to examine the consequences of the new nonlinear constitutive relation suggested, a thermomechanical pulsating flow between two parallel plates is considered. By approximating the general constitutive equations in the postulated general equations of motion, analytical solutions of the velocity and temperature fields can be found to be in good agreement with experimental results.
The analytical expressions for the velocity and temperature profiles can then be used in the estimation of the heat transfer, which can be compared with experimental observations. (Less)
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http://lup.lub.lu.se/record/1367122
 author
 Lundgren, Ebbe ^{LU} ; Marksten, Ulrik and Möller, SvenInge ^{LU}
 organization
 publishing date
 1998
 type
 Chapter in Book/Report/Conference proceeding
 publication status
 published
 subject
 in
 HEAT TRANSFER
 editor
 Lee, JS
 volume
 VOL 5  GENERAL PAPERS
 pages
 381  386
 publisher
 Taylor & Francis
 conference name
 11th International Heat Transfer Conference
 external identifiers

 Other:IDS Number: BQ70W
 language
 English
 LU publication?
 yes
 id
 8449c989756847bcb1d98d3924aa0db4 (old id 1367122)
 date added to LUP
 20090407 10:57:58
 date last changed
 20160416 08:03:46
@misc{8449c989756847bcb1d98d3924aa0db4, abstract = {It has been observed and reported that in pulse combustors of Helmholtz type the heat transfer is two to five times higher than expected. From experiments, where the temperature profile in the tail pipe of a pulse combustor has been measured, we have no indication why the heat transfer should be enhanced. In the tail pipe of a pulse combustor the radial component of the temperature gradient vanishes in the main part of the of the crosssection of the tail pipe except close to the boundary of the pipe. Evidently, a temperature drop along the tail pipe of up to 500 degrees C/m, indicates that the classical linear constitutive assumption of heat conduction, i.e. Fourier's law, is incapable of describing the phenomenon observed. A powerful coupling between the oscillating velocity field and the oscillating temperature field might be able to explain the observed enhanced heat conduction.<br/><br> In Fourier's law neither a direct dependence of the heat conduction on the velocity and the velocity gradient, nor an interaction between the velocity and temperature field is given. A first extension would be to introduce a more general constitutive relation for the heat conduction vector. For that reason, in order to describe the observed phenomenon, a new nonlinear constitutive relation for the heat conduction vector has been suggested. An additional term, dependent on the velocity gradient operating on the temperature gradient, will effect the heat transfer.<br/><br> <br/><br> To be able to examine the consequences of the new nonlinear constitutive relation suggested, a thermomechanical pulsating flow between two parallel plates is considered. By approximating the general constitutive equations in the postulated general equations of motion, analytical solutions of the velocity and temperature fields can be found to be in good agreement with experimental results.<br/><br> <br/><br> The analytical expressions for the velocity and temperature profiles can then be used in the estimation of the heat transfer, which can be compared with experimental observations.}, author = {Lundgren, Ebbe and Marksten, Ulrik and Möller, SvenInge}, editor = {Lee, JS}, language = {eng}, pages = {381386}, publisher = {ARRAY(0x87859e0)}, series = {HEAT TRANSFER}, title = {On the enhancement of heat transfer in pulsating combustion flows}, volume = {VOL 5  GENERAL PAPERS}, year = {1998}, }