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[Bal]

Hello every1,

 

I'm facing 2 problems while running the hysys optimizer:

1st one is that the "optimization method fails" when i used the "mixed" optimization method (the default) but it works when i used the quasi newton method. Now, my question is how to select the suitable method for optimization?

2nd, I have a heat exchanger network, and while optimizing I set the constraints to be as the following. The outlet temperature of the hot stream should be higher than the outlet temperature of the cooling stream. However, (when) the optimizer works, it doesn't satisfy one of these constraints.

 

Now a general question about the shell and tube HE, I specified the hot stream to enter through the tube, is that correct? hysys converges because the ft is higher than 0.75 but I'm suspecting a temperature cross because the outlet of the hot stream is lower than the outlet of the cold stream. I tried switching the streams entering the shell/ tube and I obtained the same results.

 

Thanks in advance

 

[farnaz sanandaji]

Dear Bal

 

For specifying suitable optimization method you should know the essence of goal function and also constraint. The convergence also is affected by remoteness of answer. Of course this study is complicated and it is completely math operation. So you can just try hysys method. If the optimization work, it means that is the best method. 

It seems there is no temperature cross in your simulation. Whats wrong with cold outlet temp higher than hot outlet temp??? your HE is counter current . Hence cold outlet temp is higher than hot outlet temp. If hysys don't care about your constrain may be some inconsistency in constraint definition is happened.