Advanced

On the enhancement of heat transfer in pulsating combustion flows

Lundgren, Ebbe LU ; Marksten, Ulrik and Möller, Sven-Inge LU (1998) 11th International Heat Transfer Conference In HEAT TRANSFER VOL 5 - GENERAL PAPERS. p.381-386
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 cross-section 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 cross-section 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 non-linear 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 thermo-mechanical 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)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Chapter in Book/Report/Conference proceeding
publication status
published
subject
in
HEAT TRANSFER
editor
Lee, JS and
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
8449c989-7568-47bc-b1d9-8d3924aa0db4 (old id 1367122)
date added to LUP
2009-04-07 10:57:58
date last changed
2016-04-16 08:03:46
@inproceedings{8449c989-7568-47bc-b1d9-8d3924aa0db4,
  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 cross-section 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 non-linear 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 thermo-mechanical 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, Sven-Inge},
  booktitle    = {HEAT TRANSFER},
  editor       = {Lee, JS},
  language     = {eng},
  pages        = {381--386},
  publisher    = {Taylor & Francis},
  title        = {On the enhancement of heat transfer in pulsating combustion flows},
  volume       = {VOL 5 - GENERAL PAPERS},
  year         = {1998},
}