Integrating Multiple Tables with EES - kbka

[kbka]

Hi,

I'm aware that this post is regarding some engineering software, but since only mechies use EES (as far as I know) I'm posting my question here!:)

So I'm solving some first order DE's. My question is can I have multiple integration tables in EES?

The thing is I want to compress a gas from time=0 to time=10 and determine temperature and pressure. I got this part figured out.

and then from time=10 to time=20 I want to integrate using the last values of the former integration (Pressure and temperature), but using a new set of DE.

anybody have experience doing this?

regards,
kbka

 

[kbka]

I'm thinking that if I can make EES solve the first half of my program, and then afterwards solve the second half using the results from the first, that would solve my problem.

As of now EES is trying to solve the two DE simoltaneously which of course is my problem...

 

[h2oski1326]

I do have experience with this and my recommendation is to not use EES for this. I do compressor modeling and have attempted to implement a simple compressor model using EES at one point with only limited success.

To do what you are asking you will need to tell EES an order to solve things in using Modules and Subprograms (check the help files for examples).

EES is a very robust non-linear equation solver that is designed to solve many equations simultaneously. However, it is not a robust programming language and should be avoided for tasks that involve numerical stepping.

If it is a HW problem or something look into the modules and subprograms, if it is for a research project I would suggest moving away from EES.

 

[kbka]

Thank you!

It is a project, but with the amount of time remaining and my lack of experience in other languages (only one being a tad of MATLAB programming), I'd say sticking to EES is best for me.

I have another problem now though. The integral table doesn't show anymore, I have tried to place the command '$Integratable time:1;P;T' inside the module, below and above it. When I run the program A warning pops up saying
"TIME must be an integration variable in the equation-based integral. An integral Table will not be created"

The final temperature of each proces is calcuated and make sense but I'd like to be able to follow the temperature rise as the pressure is changed throughout the whole process...

Any solution to this?

 

[cargeo25]

Hello, my name's Carlos. I've come up with a similar problem of yours. I'm trying to use equation based integral functions to model the motion and drying of a particle dragged by air force while falling down in the inside of a rotary dryer. I need to do iterative integrations using the values of previous steps. I tried to use subprograms but it hasn't worked so far. Did you figure out how to do it? It's for research purposes.

Thanks a lot.