5 replies to this topic

[uetian98]

Hi All,

I am given a task to generate a linear as well as a nonlinear dynamic model of a process.
All that I am given is a differential equation.

Now Situation is that, I dont know the procedure and/or steps to generate thus models.
Can anyone help me please ?

Thanks

[uetian98]

any one

[Doggert]

Awais,

We need a lot more information to be helpful. What you've given us here is not much to work with at all.

What type of process? You were given a differential equation - I would think that it is tied to at least one type of unit operation.

What level of schooling is this class - is it an undergraduate course or a graduate course? This will help us determine the level of detail required in looking at this.

What are your givens (the equation, yes - but is there not more?)

What type of answer is required of you? You say you need a model - so I'm assuming you need a differential equation or set of differential equations?

There are quite a few very intelligent people that frequent these boards - well versed in many different types of issues a chemical engineer might face. At this point, however, it's impossible for us to know what type of help you actually need.

Please give us as much information as possible.

[gvdlans]

Awais,

I fully support Doggert's remarks.

Furthermore, when I first saw your post, the obvious question came up: How come you have been given a task to make a model while you "don't know the procedure and/or steps to generate these models". Normally you are teached something and next thing is that you have to demonstrate that you understood it...

For now, all I can do is recommend the following book:
B. Wayne Bequette, Process Dynamics Modeling, Analysis and Simulation, Prentice Hall (1998), see http://www.rpi.edu/d...quette/edu.html

Via this link you can also find some example Matlab/Simulink files that may be useful...

[uetian98]

thanks for you much interest. well here is the problem itself,


Let me paste the equations here. V(dC0/dt) = FW (C1-C0) – NAV
Here only V & C1 are the only constant -

V.....................Volume of tank
C0.....................Outlet conc. of Oxygen in Water
C1.....................Inlet conc. of Oxygen in Water
FW.....................Volumetric Flow rate of Water
NA.....................Mass Transfer rate (NA = KLA(C0-C*)
KL.....................Liquid Film Mass Transfer Coefficient
A.....................Surface Area of Bubbles / Unit Volume
C*.....................Equilibrium Conc. of Oxygen in Water

Actually I am working on a pilot scale rig. This pilot rig consists of a water filled glass walled Jar with an impeller (vertically mounted) in there. Water enters the Jar near the bottom and leaves (overflows) from a point near the top.

Nitrogen is bubbled via a sparger sitting on the botom of the jar to disturbed the already dissolved oxygen (resulting in desorbing the Oxygen out of water body). We have analysers installed that measure the oxygen contents in the water body

I have the equation as above. now considering all the parameters like Water flowrate, extra extra.... I need a dynamic model taking care of all the changes and disturbances.

I need to build both linear and non linear models.
I have a feeling that I need to consider partial differential of the above stated equation wrt ever variable in system, e.g. water flow, kLa, etc. that would give me a dynamic approach (taking into account all the parameters and then solving it).
is that true? if true then how to proceed transferring into a simulink model?

thanks again gvdlans & Doggert

[gvdlans]

Awais,

I refer to my previous post and advise you to get a copy of the book and to check out the website. The book and the website contain examples of Simulink models that are similar to your problem. You should be capable of adjusting them to fit your needs.

I could probably solve your problem but a) I am not going to do your homework and b) I don't have time for it