HEAT-TRANSFER IN PULSE COMBUSTOR TAILPIPES

A heat transfer model for the flow in the tailpipe of pulse combustors, Nu = 0.028 ($$$) over bar Re-3/4[1 + 0.21 U-0/($) over bar U(1 + 7.36(omega-omega(0))D/($) over bar U)](3/4) is proposed. The model is developed by following a novel approach resting on the microscales appropriate for oscillating (on the mean) turbulent flows. Here Nu denotes the Nusselt number based on the hydraulic diameter D of the tailpipe, ($$$) over bar Re denotes the Reynolds number based on the mean velocity ($) over bar U, U-0 denotes the amplitude of velocity oscillations, and (omega - omega(0)) D denotes the velocity related to the frequency omega of the oscillations and omega(0) is the frequency below which quasi-steadiness holds (omega(0) = 46 for the above correlation). The model is least-squares fitted to the experimental data available in the recent literature. The agreement between the data and the model is remarkably good.