Problem occuring while solving for a pfr in cofe

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Problem occuring while solving for a pfr in cofe

Postby sunny » 25 October 2017, 06:17

RWGS RXN_1.fsd
PFR model
(51.19 KiB) Downloaded 521 times
We are simulating a methanol synthesis process in cofe in which we are incorporating a PFR along with all the kinetics data, while solving for the PFR keeping on constant temperature of 540K, the simulator shows 0 Heat duty which should be some value as my reactions are exothermic, I am attaching the modelling file below. An error occurs when i am selecting the reactor to operate on heat balance using EnthalpyF, i am attaching it in screenshot(1).Please provide me some suggestions.
Attachments
Screenshot (119).png
Screenshot (119).png (93.91 KiB) Viewed 6785 times
Screenshot (1).png
Heat balance error
Screenshot (1).png (92.42 KiB) Viewed 6785 times
sunny
 
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Re: Problem occuring while solving for a pfr in cofe

Postby jasper » 25 October 2017, 07:57

The issue with switching to heat balance mode is fixed - thank you for reporting that. The fix is available via CUP.

In isothermal mode, the heat duty is not actually calculated, hence the value of 0 remains. I could hide this value altogether in isothermal mode, but if I were to populate it, it would be one of the following values:

(A) the difference between product and feed enthalpy; this value is available if you double click the unit and go to the balance page.

(B) the difference between product and feed enthalpyF; this value is also available if you double click the unit and go to the balance page. This value would account for the 'heat of reaction' by taking into account the heat of formation

(C) the integral of heat of reaction of the length of the reactor. Heat of reaction as taken from the reaction source may not be available, and if it is available, it is not used in this mode.

The value you are looking for is probably (B) as this would represent the amount of heat you would need to add/remove to keep the device at constant temperature. Would you agree?
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Re: Problem occuring while solving for a pfr in cofe

Postby jasper » 25 October 2017, 08:27

The convergence trouble in heat balance mode seems to be due to very high reaction rate of reaction WGRS. Can you check its implementation?

(note you can see the value at the first slice from the profiles report - even if it fails solving)
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