Abstract: Mixing device for fluids of high, different and varying temperatures having a housing and a cylindrical, straight mixing tube open at both ends thereof and formed intermediate the ends thereof with numerous radial openings, the mixing tube being secured at one end thereof tightly to the housing and being mounted at the other end thereof so as to be displaceable longitudinally with respect to the housing, including a shock tube disposed between the mixing tube and the housing and being, at least at one end thereof, displaceable longitudinally with respect to the housing and the mixing tube, the mixing tube having an outflow end and being secured at least at the outflow end thereof tightly to the housing, the shock tube and the mixing tube defining an annular space therebetween, an inner pipe stub terminating in the annular space, the inner pipe stub being concentrically surrounded by a housing union tightly connected to the housing, the shock tube being formed with a radial opening through which the inner pipe