5 replies to this topic

[NATU]

Dears,

 

Attached plz find the simulation file in which am trying to simulate the Thermosyphon reboiler.

 

In attached file I have built two cases;

 

For both the cases Feed inlet conditions are same only exchanger UA values are different.

 

Case I- This case is simulated by specifying service UA value (404273.11 kJ/Deg. C.hr) from exchanger datasheet. For this case exchanger is converged.

 

Case II- This case I want to simulate by using clean UA value (1212592.15 kj/Deg. C.hr) from datasheet. But for this value am not able to simulate this exchanger.

 

Basically this exchanger is Stabilizer Reboiler (Thermosyphon type). It is generating 0.28% of vapor from total stream in normal operation. Normal operating duty is calculated by using service UA.

 

I want to check the how much amount of this reboiler will generate if I use clean UA

BY KEEPING SAME STEAM & PROCESS SIDE FLOW.

 

Can you plz. look in to this & try to find out the way forward.

 

Thanks for your time,

Rajiv

Attached Files

•  New Folder.zip   125.52KB   141 downloads

Edited by NATU, 16 July 2013 - 02:34 AM.

[pavanayi]

NATU,

 

Reading through, just found something that does not sound right. Is the thermosyphon reboiler outlet vapour fraction 0.28% or 28%?

[NATU]

Sorry sir!!! It was typo error. Above stabilizer reboiler is generating 28% vapor from the total inlet stream.

[himant]

Dear Rajiv

 

I am still working on your problem. However, there are two concerns which need to be solved first

 

1. Pressure drop in both simulation cases are same. In clean case, pressure drop will be less.

2. Simulation doesn't show vapor generation of 28%.

 

Regards

Himant

[NATU]

Dear Himant,

 

As per HTRI Heat exchanger specification sheet, this reboiler is generating 28% of vapor from total inlet feed stream. However, simulation result does not showing the same. That may be because of different inputs. For HTRI am specifying Heat curve & in simulation am using the actual feed composition at the inlet.

 

My first intent is to understand the reasons behind not matching the results.

 

Second thing am trying to find out the maximum possible heat exchange rate for the same inlet conditions from the reboiler when it is new.  At that time "U" will be clean "U".

 

For the pressure drop values I have attached Stabilizer Reboiler specification sheet.

 

Thanks,

rajiv

Attached Files

•  Stabilizer Reboiler (Z99-E-0015)-RevP 5.pdf   101.02KB   131 downloads

[himant]

Dear Rajiv

 

Firstly, Regarding variation in results of Hysys and HTRI, difference is only due to input provided, If you input properties in HTRI by specifying composition, results will match as Hysys works only on composition provided.

 

Secondly, as the fouling occurs in exchanger, net heat transfer area decreases. And I don't see any UA value which you have taken in Hysys simulation.

 

Attached TEMA spec sheet shows only value of U (W/m2.K) (Clean as well as actual).

 

Now to how to calculate outlet temperature in case of non-fouled exchanger? Even we fix value of U, we can't fix value of A and Q for both cases. I am still unable to find feasible answer to above problem.

 

Regards

Himant