Numerical analysis of internal recirculation into a radiant tube without internal ignition

This paper presents a numerical analysis using the CFD Fluent (6.3.26 version) program to identify the effects that can be generated when using radiant tubes with internal recirculation of combustion products, but with a pre-combustion chamber. The numerical results are validated with an experimental assembly based on the outlet deviation of gases temperature. These deviations were less than 5 % and are attributed principality to isolation deficiency in the re-radiant surface. To independently find the recirculation effect in this tube, the same operational characteristic in the tube were maintained and an analysis using different windows recirculation widths as well as one without windows was done. Through this analysis, it was possible to observe the little importance of recirculation effects when combustion doesn’t occur internally in the tube on the uniformity surface temperature on the external tube and the emitted energy, but it decrease the system pressure drop slightly although its magnitude order is very small.