Abstract: An atomizer wheel for use in a spray drying apparatus comprises an interior annular liquid supply chamber, from which a number of substantially radial ejection ducts extends towards the external surface of the wheel through a length constituting a considerable portion of the radius of the wheel. The ducts discharge into a downwardly open annular discharge slit at a comparatively short distance from an external wall connected with a wheel cover and whose inner wall surface forms an axial-symmetrical surface of revolution with a substantially linear generatrix forming an angle of not more than 15.degree. with the axis of revolution.