This device comprises a hollow body, the hollow body defining: an internal conduit for distributing the first fluid, the internal conduit defining an inner volume; an external conduit or distributing the second fluid, the internal conduit and the external conduit extending coaxially along a longitudinal axis (AA′). It at least comprises one metal tube extending along the longitudinal axis (AA′) and being positioned in the inner volume of the internal conduit and/or in the downstream extension of the internal conduit and/or of the external conduit.