3. Experimental results
The first step in the analysis of the experimental data was to define the initial acceleration region were the gas solid flow is under transient conditions and the final steady state conveying region. This was carried out by observing how the pressure drop per unit length of conveying pipe changed along it. This pressure drop per unit length has initially low values as corks are moving away from the curve separating the horizontal portion of the conveying pipe from the vertical one. In the first portion of the vertical pipe, particles are moving slowly and the velocity differential between
the gas and the solid phase is high, increasing the drag effect upon the particles that start to be re-accelerated. However, this phenomenon is just starting and thus the overall pressure drop corresponding to the first measurement still indicates a lower value. Afterwards, the pressure drop rises up to a maximum around 1 or 2 meters away from the curve and then diminishes slowly until reaching an almost constant value beyond 3 to 3.5 m, where steady state conveying conditions predominate. Figure 3 presents, for some experimental runs, such evolution of the pressure drop.