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Thermosyphon Modeling In Hysys Dynamic

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#1 lee1706


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Posted 29 May 2018 - 08:28 PM


I am trying to model pressure build up unit(heat exchanger) connected to tank by using hysys dynamic.

To be specific,

Feed line is normally closed(VLV-100), and tank(V-100) is initially filled with LNG at 85 volume %.

Once VLV-103 is opened,  heat exchanger(E-100) evaporates LNG and the evaporated vapors go back to tank(V-100) and pressuriz tank. Then, vapor in tank goes to consumer through stream 5.

I attached picture.


Can this process be modeled in hysys?


I have tried but the flow rate in stream 5 is very slightly increased in spite of te increased Q-100.

Could anyone help me out solving this issue?

Any tip will be appreaciated. Thanks for reading.




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#2 Bobby Strain

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Posted 29 May 2018 - 09:32 PM

Why do you want to attempt such an exercise?



#3 lee1706


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Posted 29 May 2018 - 10:17 PM

Hi Bobby,

I am working in ship industry, so I study LNG system being utilized on the ship.

I want to simulate the attached.


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#4 walidd_23


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Posted 31 May 2018 - 02:43 AM


I think if you are familiar with dynamic simulation , this would be simple exercise, please see below comments 


- Add some controllers to get a steady state case before to do any scenarios 

-Check the boundary pressure, if the pressure of stream 8 close to 5 , the flow will be small.

-Check the equipment size , small valve sizing will create large pressure drop and reduce the flow

-It is better the replace  the heater with heat exchange for better control of temp

-Enable the liquid head contribution.

-Fix the nozzle location

-Instead of using QV-100, use heat loss on the separator tab to estimate the heat transfer to environment under a fix ambient temp 




#5 lee1706


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Posted 31 May 2018 - 07:53 PM

Dear Walidd.

Thanks for your detailed advice.

I am not so familiar with dynamic simulation. however trying to learn. I will do as you suggested and come back if more queries.


In the meanwhile, I got problem.

When I click property tab on stream, there are warning messgage as following



Flash results are within tolerance, but may be unsatiffactory because extrapolated EOS vapor volume root was used for property calculations.



Stream composition is ;

Methane : 0.91

Ethane : 0.0571

Propane : 0.0214

Isobutane : 0.0046

Nitrogen : 0.0022

n-butane : 0.0047


Condition is -160C, 500kPa, 540kg/hr. EOS is PR.

Could you please let me know why this warning message comes?

When I change temperature -140C, then this  error is not shown, but the problem is other streams still come with this warning message.

#6 AlertO


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Posted 03 June 2018 - 09:03 PM

Hi Lee


For your HYSYS warning, it is probably your simulated temparature is out of the availvable range of binary system database (for PR) and it just remind you that the program has done the extrapolation.


For your simulation, i've never done the thermosyphon loop like this in HYSYS. Is the syphon loop calculated?  I think you need to ensure that the model is represented your process in steady state before turning it to dynamic.


Hope this may help you.

Edited by AlertO, 03 June 2018 - 09:04 PM.

#7 Tanhieungo


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Posted 09 July 2018 - 07:50 AM

To solve this problem you should active static head funtion at integrator of Hysys dynamic. And change k conducte constant you will see flow rate to evapor increase together increase k conducte ( tanhieungo@gmail.com)

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