28
1 Introduction
tools applied. In addition, the responses of a bubble flow to different pulsing conditions are investigated through a parametric study. It provides a comparison across
structured pulsed beds, unstructured pulsed beds and conventional fluidised beds in
terms of characteristics of bubbles, such as bubble size, bubble rising velocity, and
corresponding distribution.
It is essential to understand whether the structured flows possess any practical
advantage which promotes the overall performance over steady flow fluidisation.
Chapter 3 discusses and provides insights into the features of structured flows. A
regularity indicator is introduced to quantify the degree-of-order and guide the reproducibility of experimental bubbles dynamics. The quantification identifies the operating regimes of structured flows through comparisons across varying flow conditions
and bed heights.
The particulate phase dynamics are critical to the understanding of pattern formation, but often difficult to be accessed with direct experimentation. Chapter 4 presents
a study comparing experimental and computational flow patterns using both the
Eulerian-Lagrangian and the Eulerian-Eulerian modelling approaches, in order to
gain fundamental insights into the onset and stabilisation of structured flows. Both
the gas and solid phase dynamics, during a patterned state, are studied and related
to the pulse synchronised nucleation of bubbles. Besides, the unique appearance of
structured flows serves as a tool for multiphase flow model validation and development. As a proof of concept, experimentally observed flow patterns are applied as
a “fingerprint” to evaluate the performance of Eulerian-Eulerian two-fluid models
under its common implementations.
Chapter 5 then provides a comprehensive study of the simulated patterns of
different multiphase models as well as the experimental observations, in terms of
bubble size, wavelength, rising velocity and solid circulation. It allows identifying
the important factors and also revealing their effects on the onset and stabilisation of
structured flows.
Additional relevant information of applied correlations, methodology and calibration are provided in the appendix, which is considered not essential for understanding
the content of this thesis.
References
1. Ajbar A, Alhumazi K, Asif M (2005) Improvement of the fluidizability of cohesive powders
through mixing with small proportions of group A particles. Can J Chem Eng 83(6):930–943
2. Akhavan A, van Ommen JR, Nijenhuis J, Wang XS, Coppens M-O, Rhodes MJ (2008)
Improved drying in a pulsation-assisted fluidized bed. Ind Eng Chem Res 48(1):302–309
3. Alamian R, Baniassadi A, Tabrizi HB (2011) An experimental study on effects of applying
the pulsating flow to a gas-solid fluidized bed. World Acad Sci Eng Technol 73:977–981
4. Ali SS, Asif M (2012) Fluidization of nano-powders: effect of flow pulsation. Powder Technol
225:86–92
5. Ambrosio-Ugri MCB, Taranto OP (2007) Drying in the rotating-pulsed fluidized bed. Braz J
Chem Eng 24(1):95–100
1 Introduction
tools applied. In addition, the responses of a bubble flow to different pulsing conditions are investigated through a parametric study. It provides a comparison across
structured pulsed beds, unstructured pulsed beds and conventional fluidised beds in
terms of characteristics of bubbles, such as bubble size, bubble rising velocity, and
corresponding distribution.
It is essential to understand whether the structured flows possess any practical
advantage which promotes the overall performance over steady flow fluidisation.
Chapter 3 discusses and provides insights into the features of structured flows. A
regularity indicator is introduced to quantify the degree-of-order and guide the reproducibility of experimental bubbles dynamics. The quantification identifies the operating regimes of structured flows through comparisons across varying flow conditions
and bed heights.
The particulate phase dynamics are critical to the understanding of pattern formation, but often difficult to be accessed with direct experimentation. Chapter 4 presents
a study comparing experimental and computational flow patterns using both the
Eulerian-Lagrangian and the Eulerian-Eulerian modelling approaches, in order to
gain fundamental insights into the onset and stabilisation of structured flows. Both
the gas and solid phase dynamics, during a patterned state, are studied and related
to the pulse synchronised nucleation of bubbles. Besides, the unique appearance of
structured flows serves as a tool for multiphase flow model validation and development. As a proof of concept, experimentally observed flow patterns are applied as
a “fingerprint” to evaluate the performance of Eulerian-Eulerian two-fluid models
under its common implementations.
Chapter 5 then provides a comprehensive study of the simulated patterns of
different multiphase models as well as the experimental observations, in terms of
bubble size, wavelength, rising velocity and solid circulation. It allows identifying
the important factors and also revealing their effects on the onset and stabilisation of
structured flows.
Additional relevant information of applied correlations, methodology and calibration are provided in the appendix, which is considered not essential for understanding
the content of this thesis.
References
1. Ajbar A, Alhumazi K, Asif M (2005) Improvement of the fluidizability of cohesive powders
through mixing with small proportions of group A particles. Can J Chem Eng 83(6):930–943
2. Akhavan A, van Ommen JR, Nijenhuis J, Wang XS, Coppens M-O, Rhodes MJ (2008)
Improved drying in a pulsation-assisted fluidized bed. Ind Eng Chem Res 48(1):302–309
3. Alamian R, Baniassadi A, Tabrizi HB (2011) An experimental study on effects of applying
the pulsating flow to a gas-solid fluidized bed. World Acad Sci Eng Technol 73:977–981
4. Ali SS, Asif M (2012) Fluidization of nano-powders: effect of flow pulsation. Powder Technol
225:86–92
5. Ambrosio-Ugri MCB, Taranto OP (2007) Drying in the rotating-pulsed fluidized bed. Braz J
Chem Eng 24(1):95–100