4 replies to this topic

[kaidlut]

Hi all，

 

currently I have one question puzzled me a lot.

 

When i do Hysys heat exchanger simulation，and when the cold stream outlet temperature is higher than the hot stream outlet temperature, there will be a error warnning "temperature cross".Usually,we try to avoid such situations. But i checked some of the process specifications of heat exchanger of my plant, this situation ( the cold stream outlet temperature is higher than the hot stream outlet temperature)does exist, is this normal ?

 

Thank you !

[latexman]

It is possible. Generally temperature crosses are best avoided with a single shell S&T exchanger. That is because the exchanger's effectiveness drops rapidly at the temperatures cross. However, there are configurations and strategies, including use of multiple shells, that can overcome this problem.

[Yogan]

Hello latexman,

 

I am facing a similat problem and I posted it here:https://www.cheresou...-exchanger-lng/

Basicaly I would like to avoid it controling the effectiveness of my HX. So I will have the highest effectiveness as possible without having a themperature cross. 

I am just facing troubles to implement it in HYSYS. Coulsd you assist me?
 

Thank you very much for your attention.

[latexman]

Hi Yogan,

 

I saw your post.  I have no experience with HYSYS.  I dabble in Aspen+, but don't consider myself to be anywhere near an expert in that.  Since I had/have no specific HYSYS advice on your issue, I did not reply.  It seems you understand what I was talking about in my reply above, so you just need some specific HYSYS advice.  Hopefully, someone will reply shortly.  Have you searched HYSYS's knowledge base?  Aspen+ has one.  Have you called/online chatted with HYSYS support?

[golegolegole]

Hey kaidlut, have you seen if the pressure of the fluid after it passes the heat exchanger dips down below the Vapour Pressure of the liquid? In that case, Aspen Exchangers (non-edr) do give the error of temperature cross. Hope this helps. 

Hi all，

 

currently I have one question puzzled me a lot.

 

When i do Hysys heat exchanger simulation，and when the cold stream outlet temperature is higher than the hot stream outlet temperature, there will be a error warnning "temperature cross".Usually,we try to avoid such situations. But i checked some of the process specifications of heat exchanger of my plant, this situation ( the cold stream outlet temperature is higher than the hot stream outlet temperature)does exist, is this normal ?

 

Thank you !