A device, system and method of mixing two fluids are described herein. A gaseous first fluid is distributed through a distribution zone to a mixing zone by a bundle of pipes parallel to an axis inside which the first fluid is uniformly distributed. A second fluid is uniformly distributed outside the pipes in the distribution zone. The mixing zone is separated from the distribution zone by a pipe-plate supporting the pipes. The pipe-plate has slits or openings to uniformly discharge the second fluid in an axial flow direction into the mixing zone. The pipes extend beyond the pipe-plate into the mixing zone to partialize an outlet flow of the first fluid. In one aspect, the pipes have different lengths to partialize the outlet flow. In another aspect, a terminal portion of the pipes partializes the outlet flow axially, radially, transversally or a combination thereof in the mixing zone.