In process design, the state of flow in a disperse system must be taken into consideration not only with respect to the aerodynamic resistance, but also with respect to heat and mass transfer as well as chemical reactions. According to the state-of-the-art, convective heat transfer, for example, is usually described by relations of the form of Nu = Nu(Re, Pr). From the definition of the Reynolds number, it follows conclusively, that unique functions Nu = Nu(Re, Pr) are obtained only for geometrically similar systems. With disperse systems, however, geometrical similarity is lost in two ways : with a change in the particle shape, and also with a change in the void fraction. These peculiarities result in a corresponding complexity, e.g. the observed heat transfer phenomena. An alternative approach is proposed as following : For the description of the aerodynamic resistance R of the elements of a disperse system as usual the Reynolds number Re = (ud)/nu, but also a new drag number, Dr = (6 rho(f)R)/(pi mu(2)) are introduced, i.e. it is proposed to represent the aerodynamic resistance of disperse systems in the form of Dr = Dr(Re) instead of the usual form c(D)(Re), because the drag number is free from the kinematic variables u, and d of the flow field. In particular, within reasonable limits of accuracy, two geometrically dissimilar systems exhibit the same Nusselt number, when their drag numbers coincide, i.e. the alternative form Nu = Nu(Dr, Pr) seems to be more appropriate. This latter feature will be shown in detail by the prediction of the heat transfer coefficients between submerged surfaces and fixed as well as fluidized beds percolated by a gas at higher Reynolds numbers.