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Vertical Thermosiphon Static Head Calculation


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#1 Beergson

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Posted 07 March 2019 - 01:33 PM

Dear Members

I'd like to know your approach regarding to vertical thermosiphon static head calculation. Do you calculate it in reference to columns bottom Normal Liquid Level, or Low Liquid Level? 

Thank You in advance for sharing yours opinion

Best regards



#2 Bobby Strain

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Posted 07 March 2019 - 11:40 PM

You want the performance at normal level. Check for low level. I have never seen a universal agreement. And, as you know, it's rarely mentioned.

 

Bobby



#3 Beergson

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Posted 08 March 2019 - 06:14 AM

Bobby,

yes, its rarely mentioned,

I found that some Licensors (ie UOP) design thermosiphons taking into account 0 column level (elevation of bottoms level controller nozzle) in theirs hydrualic tabulation, and this approach is conservative, but closer also to me.

 

Especially if you meet a process operators or even process foremans who ask you what level to maintain in reflux drum or column's bottom - you can not count on that they will always run at i.e. 50% (NLL) ;)

 

Regards



#4 srfish

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Posted 08 March 2019 - 01:55 PM

Kern doesn't refer to liquid level but 5-10 minutes of holdup time. Hewitt,Shires and Bott  say " The liquid level in the bottom of the distillation column is maintained well above the bottom tubesheet of the exchanger".


Edited by srfish, 08 March 2019 - 01:55 PM.


#5 Beergson

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Posted 08 March 2019 - 03:20 PM

Kern doesn't refer to liquid level but 5-10 minutes of holdup time. Hewitt,Shires and Bott say " The liquid level in the bottom of the distillation column is maintained well above the bottom tubesheet of the exchanger".

Srfish,
Are these quotation referred directly to thermosiphon design static head? It is not a problem to maintain liquid level well above bts (LLl o NLL in column bottom) of reboiler but in this topic we are considering detailing approach.

Edited by Beergson, 08 March 2019 - 03:23 PM.





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