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Micro-bubble analysis images on some measured cases: left, micro-bubbles in deionised water, 0.2% CMC solution, solution of 0.2% CMC and 0.15% fibres, and on right bubbles in 0.125 M nbutanol.
Source publication
This paper studies hydrodynamic drag forces acting on freely rising microbubbles
in dilute paper machine suspensions under turbulent flow conditions.
Dissolved, colloidal and numerous solid materials i.e. process chemicals, wood
extractives, fillers and wood fibre fractions present in these suspensions disturb
the rise of micro-bubbles increasing t...
Contexts in source publication
Context 1
... that the chemical and physical properties of these white waters have little effect on the formed bubble size distribution. White waters produce micro-bubbles with similar size distribution to 0.125M n-butanol solution that has similar surface tension and apparent viscosity. However, the generated micro-bubble concentrations differ significantly. Fig. 4 shows sequences of three consecutive images overlaid on top of each other. The circles on top of the images present the detected in-focus bubbles and the blue arrows correspond to their velocities. Fig. 4 demonstrates how already the experimental images reveal the differences of suspensions. For example, CMC solution produces large ...
Context 2
... solution that has similar surface tension and apparent viscosity. However, the generated micro-bubble concentrations differ significantly. Fig. 4 shows sequences of three consecutive images overlaid on top of each other. The circles on top of the images present the detected in-focus bubbles and the blue arrows correspond to their velocities. Fig. 4 demonstrates how already the experimental images reveal the differences of suspensions. For example, CMC solution produces large bubbles that have higher tendency to attach on solid surfaces. The stagnant bubbles remain undetected and are not analysed. with respect to bubble Reynolds number (Re B ) and the measured rise velocities with ...
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Citations
... After the introduction of high-resolution digital cameras, this technique has been developed intensively [40][41][42][43][44]. To date, direct optical imaging has been utilized in numerous scientific and industrial applications-mainly for bubbly liquids [45][46][47][48][49][50][51], but also for foams [52]. ...
Foam forming is an intricate option to lessen fiber flocculation and to get better energy and water efficiency when making fiber-based products. Developed during the 1970s, this approach has recently received renewed attention, mainly because it also offers possibilities to widen the fiber-based product portfolios with novel and more valuable products. In addition to air content, bubble size is the most important property of foam. Foam quality control is essential for building real-world foam forming processes. In this work, we show how bubble size can be monitored with direct optical imaging in real time in real process conditions, and how such analysis helps adjust foam quality and discover process faults in foam forming.
