Experiments were carried out to determine the characteristics of bubbles originated in still tap water by a porous polyethylene pipe used as an air sparger. Local bubble populations were sampled at various regions of the pipe cross-section and at various air flow-rates to assess the effects of the surface local orientation and flow conditions on bubble dimensions. It was discovered that at the bottom of the pipe the size distribution of the bubbles is almost invariant with respect to air flow. On the contrary, at other locations bubble dimensions increased with the air flow-rate and the surface inclination. Statistical analyses proved that the distributions of bubble diameters and their mean values are better modeled by the Gamma distribution than the Log-Normal distribution. Local populations were merged to get the corresponding global populations. It was discovered that the bubbles from the upper half of the pipe cross-section have a higher weight in determining the properties of global populations. Global bubble populations from the whole crosssection of the pipe were directly measured at low air flow-rates. Their mean diameters were used to validate the merging procedure. Two Koide-like correlations were successfully implemented to model as a function of the Froude and Weber numbers the dimensionless mean diameter and the dimensionless Sauter mean diameter of the global bubble populations. The Froude and Weber numbers were computed based on the flow of air through the porous wall, which was successfully modeled with the Forchheimer equation for compressible fluids. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.
Experimental investigation on bubbles generated by porous pipes
Coletto, A;Poesio, P
2022-01-01
Abstract
Experiments were carried out to determine the characteristics of bubbles originated in still tap water by a porous polyethylene pipe used as an air sparger. Local bubble populations were sampled at various regions of the pipe cross-section and at various air flow-rates to assess the effects of the surface local orientation and flow conditions on bubble dimensions. It was discovered that at the bottom of the pipe the size distribution of the bubbles is almost invariant with respect to air flow. On the contrary, at other locations bubble dimensions increased with the air flow-rate and the surface inclination. Statistical analyses proved that the distributions of bubble diameters and their mean values are better modeled by the Gamma distribution than the Log-Normal distribution. Local populations were merged to get the corresponding global populations. It was discovered that the bubbles from the upper half of the pipe cross-section have a higher weight in determining the properties of global populations. Global bubble populations from the whole crosssection of the pipe were directly measured at low air flow-rates. Their mean diameters were used to validate the merging procedure. Two Koide-like correlations were successfully implemented to model as a function of the Froude and Weber numbers the dimensionless mean diameter and the dimensionless Sauter mean diameter of the global bubble populations. The Froude and Weber numbers were computed based on the flow of air through the porous wall, which was successfully modeled with the Forchheimer equation for compressible fluids. (c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
