Rheological behaviour of two-phase flow of solid particles in a gas

The present investigation was concerned with the rheological behaviour of dilute suspensions of solid particles in a gas in a vertical cocurrent flow moving upwards. Starting from the experimentally determined dependence of the pressure drop on the concentration of solid particles and the Reynolds number of the carrier medium in the steady flow region, the rheological parameters were estimated using pseudo-shear diagrams. Air was the carrier medium and the dispersed phase was one of six fractions of polypropylene powder and five fractions of glass ballotini. The results show that the investigated two-phase systems have pseudoplastic character which becomes more pronounced with increases in concentration, equivalent diameter and density of solid particles in the flowing suspension.C_d coefficient of particle resistance - d_e equivalent diameter of particles - D column diameter - Fr Froude number - g gravitational acceleration - K rheological parameter - L length - n rheological parameter - p_t pressure drop due to friction - p_m total pressure drop - p_ag pressure drop due to acceleration of the gas phase - p_as pressure drop due to acceleration of the solid phase - p_g hydrostatic pressure of the gas phase - p_s specific effective weight of the dispersed phase - r radius - Re Reynolds number - Re_p Reynolds number of a particle - Re_G generalized Reynolds number - Re_G1 generalized Reynolds number relating to the end of the laminar flow region - Re_G2 generalized Reynolds number relating to the beginning of the turbulent flow region - w_z axial component of velocity - u_t steady free-fall velocity of a single particle - w average velocity - w_g average velocity of the gas phase - w_s average velocity of the dispersed phase of solid particles - relative mass fraction of solid particles - x_s volume fraction of solid particles - _g coefficient of pressure drop due to friction - µ dynamic viscosity - _g density of the gas phase - _m density of the suspension - _s density of solid particles - _ds density of the dispersed phase - _w shear stress at the wall