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Solution Strategies For Starting The Simulation


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#1 kushagra2103

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Posted 05 June 2017 - 03:36 PM

Hello all,

For starting a simulation we need an initial guess value to the decision variables that may ultimately reach the optimum point. For example in distillation columns, suppose we want to set the initial temperature values so one solution will be to do a linear interpolation of the temperature upper and lower bound values and then correspondingly we take those initial guess values. So I need such solutions strategies for various unit operations so that the distance between the guess value and the optimum point is less.

 

Regards  


Edited by kushagra2103, 05 June 2017 - 03:39 PM.


#2 Bobby Strain

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Posted 05 June 2017 - 04:27 PM

You need to be more specific as to your objective. And, we are not going to do your work for you. Show us what you have and where you need guidance. Your example is not a good one. We don't usually take the approach to distillation that you infer.

 

Bobby



#3 kushagra2103

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Posted 06 June 2017 - 06:42 PM

Thanks for the reply. I am sorry for not being clear. I am just asking as for how we can refrain ourselves from taking a poor initial guess in an iteration in general. 

 

Regards


Edited by kushagra2103, 06 June 2017 - 07:10 PM.


#4 Bobby Strain

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Posted 06 June 2017 - 07:30 PM

I think the correct answer is experience. Don't be afraid to try many things with simulations. And, it's always best to study tutorials available on the simulator owner's support site. You should know the details of the process you are simulating before you attempt your simulation. You can't create something from nothing.

 

Bobby



#5 Pilesar

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Posted 07 June 2017 - 06:55 AM

  Sequential modular simulators compensate well for lack of initial solution estimates. When recycles are highly integrated into the model, make your best guess at initial estimates for the recycle streams and let the convergence algorithm do its work. If the model does not reach convergence, investigate the solution path and tweak the algorithm. Usually the lack of solution is due to improper specifications. There are a few techniques to break recycles to avoid convergence problems which you will need to learn for complicated models.

  Simultaneous equation simulators are much more influenced by initial estimates. Seeding simultaneous equation models with the results from a sequential modular solution is common practice.



#6 kushagra2103

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Posted 07 June 2017 - 12:33 PM

Thanks for the input @Pilesar, @bobby. 

 

Regards






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