| 1. |
- Wiklund, Johan A., et al.
(författare)
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A comparative study of UVP and LDA techniques for pulp suspensions in pipe flow
- 2006
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Ingår i: AIChE Journal. - : Wiley. - 0001-1541 .- 1547-5905. ; 52:2, s. 484-495
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, noninvasive measurements in pulp suspensions at consistencies ranging from 0.74%(w/w) up to 7.8%(w/w) have been performed simultaneously using ultrasound velocity profiling (UVP) and laser doppler anemometry (LDA) in an experimental pipe flow loop. Results show that both techniques can be used to determine the plug flow velocity with good agreement in much more concentrated pulp suspensions than what has been reported so far in the literature. Instantaneous velocity profiles have been obtained noninvasively in pipe flow using the UVP technique, and it is shown that combined with simultaneous pressure drop measurements, the UVP technique can be used to determine the yield stress in-line. Results further show that LDA works, with limited penetration depth of up to several millimeters, even in strongly opaque systems, such as in 7.8%(w/w) pulp. Deviating results were however obtained in the near wall region and more work is needed.
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| 2. |
- Fock, Helena, 1979, et al.
(författare)
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Ultrasound Velocity profile (UVP) measurements of pulp suspension flow near the wall
- 2009
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Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 35:1, s. 26-33
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Tidskriftsartikel (refereegranskat)abstract
- An Ultrasound Velocity profiling (UVP) technique is used in this study to investigate the pipe flow of pulp suspensions in the near wall region. Four flow rates and two consistencies were investigated: 1.9 and 4.8% (w/w) consistency. The mean velocity profiles showed a distinct plug at the centre of the pipe, surrounded by a sharp velocity gradient. The plug size increased with increasing consistency or decreasing bulk velocity. The demodulated echo amplitude (DMEA) profile slowly rises from low values near the wall to a distinct maximum at the plug front before slowly decaying towards the pipe centre. Since only the fibres and fines contribute to the attenuation of ultrasound, the demodulated echo amplitude profiles thus indicate and support the hypothesis of the existence of a consistency profile in the near wall area, with a decreasing amount of fines and fibres close to the pipe wall.
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| 3. |
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| 4. |
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| 5. |
- Ström, Daniel, 1971, et al.
(författare)
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A new device for coating single particles under controlled conditions
- 2005
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 60, s. 4647-4653
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Tidskriftsartikel (refereegranskat)abstract
- A new device for coating a single levitated particle in a controllable environment is designed and tested. This enables fluidized bed processing to be simulated experimentally on a single-particle level. The device consists of a coating chamber, which contains a capillary tube for levitating the particle, a micro-dispenser for producing discrete drops of controlled size and velocity and a device for supplying gas with specified temperature and humidity. The coating chamber consists of two parts, a confined space where the particle is levitated and a droplet insertion cone where the coating solution is injected into the particle suspending gas flow. A capillary with a well-defined diameter connects the droplet insertion cone and the area where the particle is levitated. The device is equipped with a piezo-actuated flow-through micro-dispenser that has the ability to produce discrete droplets with high reproducibility in terms of droplet size and velocity. The gas required for the coating process is taken from a gas container where the water content is analysed and kept at a minimum. A liquid flow is then introduced into the gas flow at a well-defined flow rate, mixed and evaporated in a three-way mixing vault. The humidified gas flow is then split into two separate flows; a suspending gas flow and a protecting gas flow for the inside of the coating chamber. The device is equipped with a high-speed video camera for monitoring both droplet production and droplet impact. Temperatures and flow rates throughout the device are measured and logged. Preliminary results show the influence of solvent, gas quality and coating procedure on the quality of the coating.
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