The enhancement of heat transfer in the tail pipe of a pulse combustor

For pulse combustors of the Helmholtz type, a heat transfer of the order two to five times higher than expected has been reported. Experiments, where the temperature profile in the tail pipe of a pulse combustor has been measured, give Ilo indication why the heat transfer should be enhanced. The interaction between the oscillating velocity field and the oscillating temperature field might explain the observed enhanced heat conduction.
In order to examine this interaction, a thermomechanical pulsating flow between two parallel plates has been considered. The governing equations were coupled with the classical constitutive assumptions of linearly viscous fluid and Fourier's law for heat conduction. The pressure and temperature gradients in the axial direction were approximated as harmonically oscillating functions in time, where the coefficients were estimated from experimental data. By neglecting the viscous net power term in the energy balance equation, the postulated general equations of motion were solved analytically in the transversal direction. The solutions obtained for the velocity and temperature fields were found to be in good agreement with experimental results.

The analytical expression for the temperature field was then used to determine the heal transfer at the plates. The heat transfer at the plates was found to be dependent on the phase difference between the pressure and temperature gradients.