Characteristics of Pressure with Respect to Heterogeneous Flow Structure in Fluidized Beds

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The characteristics of pressure in gas/solids fluidization is measured with respect to the heterogeneous structure typified as lateral core/annulus segregation and local two-phase coexistence. Experiments are carried out in two circulating fluidized bed risers with bed diameters of 0.09 m and 0.15 m, respectively. Particles FCC (Geldart A) and silica sand (Geldart B) are used in the experiment, and are fluidized by air. It is found that the dynamic changes of the particle-rich dense phase (clusters or emulsion) and the fluid-rich dilute phase (broth or bubbles), as well as the alternations between these two distinct phases, can create a serious imbalance of instantaneous pressures among different radial locations at a same bed height. However, only a subtle time-mean pressure difference can be detected between the bed wall and the bed center with the higher pressure residing on the bed wall. It is observed that this wall-to-axis pressure difference is less than 30 Pa in a typical fast fluidized bed, while it reaches at most about 150 Pa for usual bubbling fluidization. The intra-phase pressures in both the dense phase and the dilute phase are also demonstrated to be subject to a dynamic variation other than a particular relation.
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