Experimental quantification of the particle–wall frictional forces in pseudo-2D gas fluidised beds

Abstract

Abstract:In this work a novel measurement technique for pseudo-2D fluidised beds is developed. The objective is to give an estimation of the overall frictional force between the solids and the front and rear walls of the bed. For doing this, the measured pressure signal in the bed is processed in combination with the solids distribution (i.e. centre of mass position, velocity and acceleration) obtained from digital image analysis of the optically accessible front view of the bed. This is performed by acquiring the pressure signal in the bed simultaneously to the digital images. Both the pressure and the digital images are connected through a simple force balance in the bed, and a particle-wall interaction coefficient is obtained assuming that the overall frictional force is proportional to the centre of mass velocity. The particle-wall interaction coefficient found using this technique is of the order of 40-120 kg/m 2 s in the bed tested, and the standard deviation of the frictional forces reaches more than 70% of the weight of the bed. Therefore, the results indicate that the contribution of the particle-to-wall friction on the fluctuation of the pressure drop in a pseudo-2D bed is not negligible.

Fully coupled TFM-DEM simulations to study the motion of fuel particles in a fluidized bed

“…Previous works have shown how these walls affect the dense phase motion in the simulation of pseudo-2D beds Hernández-Jiménez et al, 2011a;Li and Zang, 2013;Hernández-Jiménez et al, 2013, 2014. Nevertheless, the preliminary comparison performed here is aimed to study the basic interaction between the fuel particle and the dense and bubble phases, without taking into consideration other interactions such as particle or dense phase wall interactions.…”

Compressible-gas two-fluid modeling of isolated bubbles in a vertically vibrated fluidized bed and comparison with experiments

“…Similarly toFigure 3, the presence of the plenum in the simulated domain promotes a softening in the oscillating movement of the whole bed, which is also reflected through a decrease in the amplitude of the bubble diameter fluctuations. Differences between the phases and amplitudes of the compressible gas simulations and the experiment could be attributed to the friction caused by the front and rear walls in the experiments[41][42][43], which can retard the phase of the oscillation and diminish their amplitude. This effect is not present in the two-dimensional simulation since it lacks of front and rear walls.…”

Experimental study on the characteristic mixing time of solids and its link with the lateral dispersion coefficient in bubbling fluidized beds

“…Since no extra particles are added to the bed and observation is made through visualization from outside the bed, this method does not disturb the flow [6]. To allow the external visualization of the bed, most of these studies were conducted in pseudo-two-dimensional (pseudo-2D) beds, which has been fundamental for the understanding of the dynamics of gas-solid systems [8][9][10][11][12][13][14][15][16][17].…”