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Engineering
Materials and Chemical Engineering
Modelling of two phase flow in packed bed using conservation equations
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[QUOTE="Chestermiller, post: 6560318, member: 345636"] This is a rather complicated problem, and attacking it will require good modeling strategy. The first principle of good modeling is to start simple and gradually build in complexity until you have a model that you are comfortable with. So starting with the most general mass, momentum, and energy balance equations that you have shown above and then trying to apply them to your situation is the opposite of what you should be doing. The first pair of equations you presented is much closer to where you should be heading. What is needed are some preliminary calculations using a very simple model (or an array of simple models) to get your feet wet and get the "lay of the land." Also, it would quickly give you some results under your belt. Do you have an idea of a starting design for this system, such as overall diameter, packing type, void fraction, length, bed orientation (vertical or horizontal), flow direction, etc? What is the gas/liquid, inlet fluid temperature, initial bed temperature, initial temperature and phase of fluid within bed, etc? Let's brainstorm some preliminary models to get us started. 1. Two phase flow of vapor and liquid in a bed is going to be pretty complicated, particularly if the pressure is changing and the residence time is large. Let's model what the isothermal behavior of the fluid would be (a) if it were all liquid and (b) if it were all gas. This would give us an idea of the residence time and the possible pressure variations in the bed. This is all designed to give us a handle on the relevance of the fluid flow to this system. 2. Consider a case in which the pressure of the fluid is constant and there is a huge amount of axial dispersion in the fluid, so that that the fluid is all at the same temperature within the bed, and the exit temperature is the same as the fluid temperature within the bed. This is a so-called lumped parameter continuous stirred tank model. Under these circumstances, the bed temperature would also be uniform at any time. Assume first no phase change, and determine the fluid and bed temperatures as functions of time. Then solve it for a mixture of liquid and gas exiting. Your turn to brainstorm some simplified models for this list. Also, let's see your formulation for the 2nd item on my list (at least for the no-phase-change case). If you have trouble with this, I will help. [/QUOTE]
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Materials and Chemical Engineering
Modelling of two phase flow in packed bed using conservation equations
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