10 replies to this topic

[raajesh]

While defining a heat exchanger in hysys I came across 4 parameters..Exchanger design (weighted), exchanger design (end point), steady state rating & dynamic rating.
what are these? and what is to be selected?

[Zauberberg]

Hello,

This is quoted from HYSYS tutorials and it gives a full picture:

"The End Point model treats the heat curves for both Heat Exchanger sides as linear. For simple problems where there is no phase change and Cp is relatively constant, this option may be sufficient to model your Heat Exchanger.
The main assumptions of the model are:
• Overall heat transfer coefficient, U is constant
• Specific heats of both shell and tube side streams are constant

The Weighted model is an excellent model to deal with non-linear heat curve problems such as the phase change of pure components in one or both Heat Exchanger sides. With the Weighted model, the heating curves are broken into intervals, and an energy balance is performed along each interval. A LMTD and UA are calculated for each interval in
the heat curve, and summed to calculate the overall exchanger UA. The Weighted model is available only for counter-current exchangers, and is essentially an energy and material balance model. The geometry configurations which affect the Ft correction factor are not taken into consideration in this model.

The Steady State Rating model is an extension of the End Point model to incorporate a rating calculation, and uses the same assumptions as the End Point model. If you provide detailed geometry information, you can rate the exchanger using this model. As the name suggests, this model is only available for steady state rating.

Two models are available for Dynamic Rating using the Heat Exchanger unit operation: a Basic and a Detailed model.
The Basic model is based on the same assumptions as the End Point model, which uses the standard Heat Exchanger duty equation defined in terms of overall heat transfer coefficient, area available for heat exchange, and the log mean temperature difference. The Basic model is actually the counterpart of the End Point model for dynamics and dynamic rating. The Basic model can also be used for steady state Heat Exchanger rating.
The Detailed model is based on the same assumptions as the Weighted model, and divides the Heat Exchanger into a number of heat zones, performing an energy balance along each interval. This model requires detailed geometry information about your Heat Exchanger. The Detailed model is actually the counterpart of the Weighted model for
dynamics and dynamic rating, but can also be used for steady state Heat Exchanger rating."

I think everything should be clear after you read this info.
Best regards,

[raajesh]

thank u for giving such a detailed explanation. I'm clear with that now.
I came across the term "min. approach" when dealing with degrees of freedom. Can u tell me what it is?

[Zauberberg]

Again, this is from Hysys tutorials: minimum approach refers to minimum internal temperature approach. This is the minimum temperature difference between the hot and cold stream (not necessarily at the inlet or outlet). So, when you observe cumulative heat curves (Performance/Plot tab), you can actually track this difference from inlet to outlet conditions.

One should be very cautious when selecting various design/rating variables for heat transfer equipment, because they don't have the same meaning in all software applications. Temperature approach is one of these terms and sometimes is strictly related to exchanger inlet/outlet conditions, while in other applications it may refer to cumulative heat curves and internal temperature differences at any point(s) within heat exchanger.

Regards,

[raajesh]

can u give me any good link to download hysys tutorial so that i need not ask such questions again and again?

[Zauberberg]

They were available at public university of Korea, check this link if it is still active:

http://prosys.korea....e/hysys/manual/

I know that many companies actually do not have printed copies of HYSYS tutorials (and soft copies as well, which is even more surprising), but it looks like people are not so much interested in becoming familiar with fundamentals of software they use for different jobs. It was like that in my previous company, and I encountered this phenomenon again in the company where I work for the last six months. Very strange, and very difficult to explain in today's world of professionals... Software cannot do any magic by itself, and relying solely on software outputs without knowing the basic principles of equipment design and operation, and software capabilities/limitations, can lead you toward completely invalid conclusions. I know that, for example, one gas plant design was based on absolutely incorrect assumptions extracted from Aspen software outputs, but no one has noticed this and the plant is already in late detailed design stage. I wouldn't like to be the one who will push the START button when facility is erected and comissioned, that is for sure.

Best of luck,

[raajesh]

but the link is not active. anyway i understood the problems u r referring to.

best regards

[Zauberberg]

Raajesh,

If possible, find Clarkson University home page on the internet (I don't remember the direct link/address), there are a lot of quality materials related to HYSYS.

In addition, you could browse Student Forum and look for similar posts. I think you'll find some uploaded materials there.


Best of luck,

[missbk]

They were available at public university of Korea, check this link if it is still active:

http://prosys.korea....e/hysys/manual/

I know that many companies actually do not have printed copies of HYSYS tutorials (and soft copies as well, which is even more surprising), but it looks like people are not so much interested in becoming familiar with fundamentals of software they use for different jobs. It was like that in my previous company, and I encountered this phenomenon again in the company where I work for the last six months. Very strange, and very difficult to explain in today's world of professionals... Software cannot do any magic by itself, and relying solely on software outputs without knowing the basic principles of equipment design and operation, and software capabilities/limitations, can lead you toward completely invalid conclusions. I know that, for example, one gas plant design was based on absolutely incorrect assumptions extracted from Aspen software outputs, but no one has noticed this and the plant is already in late detailed design stage. I wouldn't like to be the one who will push the START button when facility is erected and comissioned, that is for sure.

Best of luck,

Give me your email address and I will send you the soft copy of Hysys Tutorial. This tutorial is for Hysys 3.1, but I think it's the basis and you can use that for all version of Hysys.

[raajesh]

my mail id is rajessh_giet@yahoo.co.in

thank you in advance sir.

[vinee]

They were available at public university of Korea, check this link if it is still active:

http://prosys.korea....e/hysys/manual/

I know that many companies actually do not have printed copies of HYSYS tutorials (and soft copies as well, which is even more surprising), but it looks like people are not so much interested in becoming familiar with fundamentals of software they use for different jobs. It was like that in my previous company, and I encountered this phenomenon again in the company where I work for the last six months. Very strange, and very difficult to explain in today's world of professionals... Software cannot do any magic by itself, and relying solely on software outputs without knowing the basic principles of equipment design and operation, and software capabilities/limitations, can lead you toward completely invalid conclusions. I know that, for example, one gas plant design was based on absolutely incorrect assumptions extracted from Aspen software outputs, but no one has noticed this and the plant is already in late detailed design stage. I wouldn't like to be the one who will push the START button when facility is erected and comissioned, that is for sure.

Best of luck,

Give me your email address and I will send you the soft copy of Hysys Tutorial. This tutorial is for Hysys 3.1, but I think it's the basis and you can use that for all version of Hysys.

Kindly send me the tutorial , my mail id is bvvinothkannan@yahoo.com, it will be help full for me
Regards
Vinee