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Made available in DSpace on 2014-10-09T12:23:17Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:20Z (GMT). No. of bitstreams: 1 00920.pdf: 1737066 bytes, checksum: ce7d0235930bf48fbc0adb23cc0df89d (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Geociencias, Universidade de Sao Paulo - IG/USP

The aim of the current study is to model (non-wetting) liquid flow in a packed bed under the influence of gas flow. It has been observed experimentally that non-wetting liquid flows in a packed bed in form of small droplets and rivulets falling through the void regions. Continuum models have not been successful in predicting liquid flow paths when the liquid is injected through a point source in the packed bed. In the current study, we present a discrete deterministic model for modeling the liquid flow in a packed bed, under the influence of gas flow. When a high velocity gas blast in injected into a dry packed bed, a cavity or a void is formed in front of the nozzle. The cavity size increases with increasing gas velocity and exhibits hystersis in size upon increasing and decreasing gas flow rate. The cavity size is very important in determining the gas penetration into the packed bed. A proper gas flow profile prediction is necessary for determining it’s effect on the liquid flow behavior. Attempts at modeling cavity sizes have mostly been confined to experimental studies and development of correlations. Different correlations show different dependence on operating as well as bed parameters and a fundamental understanding of the cavity formation and hystersis phenomena is missing. We adopt a combined Eulerean-Lagrangian approach to study the above mentioned phenomena mathematically. Gas is modeled as a continua and solid as discrete (soft sphere D.E.M. approach). Hystersis and cavity formation studies are carried out in a 2D-slot rectangular packed bed. A discrete deterministic liquid flow model (developed and validated under structured packing conditions using x-ray radiography flow visualization technique), is used to study the effect of presence of liquid on the dry bed void size, when liquid is injected in a packed bed through a point source. It is found that the gas pushes the liquid away from the nozzle side wall. Also, the cavity sizes during gas velocity decreasing case are found to be larger in size than the void size obtained during velocity increasing case for the same inlet gas flow rate. This difference is void size leads to more gas penetration into the bed and thus more liquid shift away from the nozzle side wall. Presence of liquid is found to affect the void size (compared to dry bed size) negligibly.

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Diploma thesis analyses low-speed flow measurement. Thesis consist of 4 chapters. First chapter is about liquids and its attributes, flow meters, especially induction flow meter, which is very important for designed sensor. In second chapter is detailed process of designing sensor. Description of realization and measurement of flow is in the third chapter. Result summary is in conclusion.

Gas, liquid and powder flow in the lower part of a blast furnace is complex phenomena. In order to understand the aerodynamics of the blast furnace properly, these phenomena must be included in their advanced form. Previous studies have shown that the conditions of blast furnace resemble the cold model experiments which have been done in decreasing gas velocities. Also, the recent studies have shown that liquid flow in a blast furnace can be represented more realistically considering it discrete in nature. In the current study, both the phenomena have been considered along with the injection of powder through a nozzle while studying the fluid flow behaviour in a packed bed. The situation resembles the lower part of an ironmaking blast furnace. In this study, gas flow has been modelled using k-ε turbulent model and has been coupled with previously developed stress model to calculate the raceway size. Coal powder is treated as continuum and has been modelled in the similar way as gas flow. After this gas and powder flow model were coupled with previously developed discrete liquid flow model. Liquid flow model has been considered for structured bed only. The governing equations for gas phase were discretized. Finite Volume method was used for the solution. Co-located grid is used for the simulation. Blending of upwind difference scheme and central difference scheme (deferred correction approach) is used to achieve the stability of upwind scheme and accuracy of central difference scheme. Similar treatment was employed for powder phase. For the solution of volume fraction of powder, powder phase continuity equation was used along with pseudo time step scheme. Results obtained from gas and powder models have been validated against published experimental data. Similarly, gas-liquid flow results have been validated against published experimental data on gas-powder flow. Results obtained by gas-powder-liquid model could not be validated against any experimental or theoretical data as they are not available in the literature. The effect of various parameters on the fluid flow (gas/liquid/powder) behaviour have been studied like the effect of increasing and decreasing gas velocities, flow rates of liquid, gas and powder, size of powder and packing etc. It is found that the above mentioned phenomena have significant effect on the fluid flow behaviour in a packed bed.

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