[en] In the design of gas-solids contact systems, it has been of great concern the pressure drop and flow regime determination, being known solids and gas flow rate, the tube diameter and solids characteristics (density, diameter and shape). From the fundamental equations has been possible on this work to predict the transition velocity between countercurrent and concurrent flows (choking velocity), and these prediction were compared with the results obtained from Leung semi-empirical correlation. The mathematical formulation utilized is valid for systems on which the acceleration of the gas and solids has been considered. This acceleration hasn't been considered in many studies about two phase flow. The proposed formulation gives important informations on the flow parameters of gas-solids flow especially on the entrance region of momentum transfer. Aiming the better understanding of the influence of the dynamics variables, giving fundamental informations to scale up purposes on systems that involve gas-solids mixture, have been realized a study of parameter sensibility to obtain the quantitative dependence of the pressure drop on the superficial velocities of gas, mass flow rate of solids, initial pressure, initial void fraction, tube diameter and tube length