A Mathematical Model for the Pressure Drop Along a Positive Pneumatic Transport Line of Flour

摘要

Positive pneumatic transport of flour has been adopted in china for nearly 20 years. However, up to now, there have been no satisfactory methods for the calculation of the pressure drop. In order to provide a basis for the design of positive pneumatic transport, this study is devoted to develop an accurate mathematical model for the pressure drop along a positive pneumatic transport line of flour. Based on some basic relationships of governing the flow of gas and flour particles in a pipe and the momentum equation for one-dimensional compressible gas flows, we first solve two important theoretical problems in the positive pneumatic transport system of flour, namely, establish a differential equation of motion for gas-particle two-phase flow in a pipe and deduce an expression for additional pressure coefficient of flour (λ_z). Through the differential equation of motion, the equation of state for a perfect gas, and the continuity equation for particles and gas, a mathematical model for pressure drop along a positive pneumatic transport line of four is developed. We use the mathematical model to compute the pressure drop along a vertical pneumatic transport line of flour. The computed pressure drop agrees well with the experimental datum.