6 replies to this topic

[Aref-Gh]

Hi

sometimes in the simulation mode of HTRI there is some overdesign!

What is that mean? Is it related to divergence in calculation?

Thank you all

[Pilesar]

In simulation mode the overdesign approaches zero. Because of the internally iterative nature of the calculations, the final overdsign reported  may be slightly off from zero due to the allowed solution tolerance. If you are seeing simulation mode results far away from zero, then there are additional problems in the model.

[Said Salim]

Usually overdesign is shown whenever you select Rating mode. It should not be shown in simulation mode unless the software is assuming specific duty of exchanger or outlet temperature.

[horatorres]

Overdesings not intrinsically into the simulators.

 

We usually set the overdesign to cover process deviations or lost of efficiencies of the equipments in the conceptual design

 

horacio

[Aref-Gh]

In simulation mode the overdesign approaches zero. Because of the internally iterative nature of the calculations, the final overdsign reported  may be slightly off from zero due to the allowed solution tolerance. If you are seeing simulation mode results far away from zero, then there are additional problems in the model.

thank you

what kind of problems?

do you have any ideas? 

[Aref-Gh]

Usually overdesign is shown whenever you select Rating mode. It should not be shown in simulation mode unless the software is assuming specific duty of exchanger or outlet temperature.

but I didn't specify any additional information of process conditions, so how the software assume this duty additional conditions? 

[Pilesar]

Instead of simulation mode, I often stay in rating mode and vary my input parameters until the overdesign approaches zero. It usually takes just a few iterations and I get more insight into how changing parameters affect the performance of that particular exchanger. You might also try that approach. There is a video I have not watched but might be helpful to you on the htri.net website 'Beyond the Basics: Rating, Simulation, or Design? Understanding Case Modes in HTRI Xchanger Suite.' You should have HTRI customer support available to you as part of your license if you want someone to review your model or suspect a bug in the software.