I am trying to optimize the area of a HEN using NLP optimization. My

code works well, above a certain range of dTmin, but gives an

unfeasible solution for the other lower dTmin’s.

Could someone help me out??

Also, could someone help me if this optimization is possible using any

other type of optimization (LP, MILP, MINLP etc…)?

\

I am trying to optimize the area of a HEN using NLP optimization. My

code works well, above a certain range of dTmin, but gives an

unfeasible solution for the other lower dTmin’s.

Could someone help me out??

Also, could someone help me if this optimization is possible using any

other type of optimization (LP, MILP, MINLP etc…)?

I am afraid no one can help you without the model.

Yan

\

What formulation are you using for HEN area optimization? It is possible that the network is infeasible below certain dTmin.

I could help you with this. Mail me with the relevant info and we can take it from there.

Rahul Anantharaman

On 18 May 2012, at 23:13, Neeraj wrote:

I am trying to optimize the area of a HEN using NLP optimization. My

code works well, above a certain range of dTmin, but gives an

unfeasible solution for the other lower dTmin’s.

Could someone help me out??

Also, could someone help me if this optimization is possible using any

other type of optimization (LP, MILP, MINLP etc…)?

–

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\

Is very possible to have HEN problem in MINLP especially if you are looking at simultaneous approach for network synthesis. However, the model is needed to understand why lower dtmin returns unfeasible solution.

On Saturday, May 19, 2012 12:13:13 AM UTC+3, Neeraj wrote:

I am trying to optimize the area of a HEN using NLP optimization. My

code works well, above a certain range of dTmin, but gives an

unfeasible solution for the other lower dTmin’s.

Could someone help me out??

Also, could someone help me if this optimization is possible using any

other type of optimization (LP, MILP, MINLP etc…)?

–

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@ elgazuz, Rahul Anantharaman:

The stream data is as follows:

Inline image 1

(Source: Chemical Process Design and Integration, 2nd Edition, Robin Smith)

My aim is to find the minimum area target for dTmin =10C. For dTmin=10C, the minimum cold utility required is 10kW and the minimum hot utility required is 7.5 kW. The NLP formulation for the area target runs at a value above dTmin=80C (i.e. min. CU=34 kW and min. HU=31.5 kW) . Below this value, I am obtaining an infeasible result. I have fixed the dTmin by giving the values of the minimum utilities required directly. hence, for dTmin too, I get an infeasible result. I am solving the NLP formulation using a MINOS solver. I have used a superstructure based model calculating with 2 stages.

Could you help me out?

Neeraj

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