In this chapter the pressure drop for pneumatic conveying pipe flow is studied. The conventional calculation method is based on the use of an additional pres­sure loss coefficient of the solid particles. The advantage of this classical method is that in principle it can be applied to any type of pneumatic flow. On the other hand, its great disadvantage is that the additional pressure loss coef­ficient is a complicated function of the density and the velocity of the convey­ing gas. Also, it is difficult to illustrate the additional pressure loss coefficient and this makes the theoretical study of it troublesome.

The new pressure loss equation presented here is based on determining two parameters: the velocity difference between gas and conveyed material and the falling velocity of the material. The advantage of this method is that no additional pressure loss coefficient is needed. The two parameters are phys­ically clear and they are quite easily modeled for different cases by theoretical considerations, which makes the method reliable and applicable to various ap­plications. The new calculation method presented here can be applied to cases where solids are conveyed in an apparently uniform suspension in a so-called lean or dilute-phase flow.