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Boiling Heat Transfer Coefficient In A Heat Exchanger

heat heat exchanger boiling heat transfer heat transfer coefficient hysys edr aspen hysys exchanger design and rating surface area

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#1 abolghasem202

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Posted 16 June 2019 - 04:29 AM

Dear all,

 

I have a problem in rating and simulation of a heat exchanger. I have used both software Aspen HYSYS and Aspen EDR.

 

The exchanger surface area is 260 m2, containing 961 tubes. I want to check if this exchanger can be used for a specific heat exchange task. 

 

A 220 tone/h propane stream at bubble point, 17 bar and 48 C enters the shell side. Also, a stream of 975 ton/h n-C11 (normal undecane) at 10 bar and 99 C enters the tubes. So, propane should begin boiling in shell side and exit the exchanger in two phase condition. Also, n-C11 should exit exchanger at 83 C.

 

My main problem is that Aspen HYSYS and Aspen EDR predict different heat transfer coefficients for the shell side (boiling propane). Aspen HYSYS predicts a heat trasnsfer coeffiient of 8430 Kj/hr.m2.C while EDR predicts 30650 Kj/hr.n2.C. Therefore, I can not determine whether the heat transfer area of 260 m2 is enough for this separation or not.

 

I do not know which value of heat transfer coefficient I should use and I would appreciate your helps.

 

 



#2 PingPong

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Posted 16 June 2019 - 06:40 AM

What matters is the U-value of the exchanger.

 

The heat transfer coefficient of the boiling propane will in this particular case have only a small impact on the U-value.

 

I expect that the main resistance for heat transfer will be on the n-C11 side, and the fouling coefficients.


Edited by PingPong, 16 June 2019 - 06:59 AM.


#3 abolghasem202

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Posted 16 June 2019 - 07:09 AM

PingPong,

 

Thank you so much for your response.

You are absolutely right. But overall heat transfer coefficient (U) is calculated based on local heat transfer coefficients (h). 

 

So, the calculated U values are also different. 



#4 Pilesar

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Posted 16 June 2019 - 07:44 AM

It is likely the programs have inconsistent inputs.

#5 PingPong

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Posted 16 June 2019 - 09:09 AM

But overall heat transfer coefficient (U) is calculated based on local heat transfer coefficients (h). 

 

So, the calculated U values are also different.

Yes, but we are in the dark what local h was calculated for n-C11, what fouling factors you used, and what U values were calculated.

#6 gegio1960

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Posted 16 June 2019 - 11:29 AM

Hi Abul.

Just to follow your question I tried to input your data in hysys.

Other data should be known but, as a starting point, you can find attached the 1st trial output of the HE.

When you say "Aspen HYSYS predicts a heat trasnsfer coefficient of 8430 Kj/hr.m2.C", do you refer to the U value shown in the picture? (it is 16320 in my case)

 

E100.JPG  


Edited by gegio1960, 16 June 2019 - 11:32 AM.


#7 abolghasem202

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Posted 18 June 2019 - 12:05 AM

 

 

Yes, but we are in the dark what local h was calculated for n-C11, what fouling factors you used, and what U values were calculated.

 

 

 

Actually, the heat transfer coefficients for n-C11 in Aspen HYSYSY and EDR are close. These values are 7150 and 7270 kJ/hr.m2.C in HYSYS and EDR, respectively. So I think that the difference in U is related to the propane side.

 

Also, fouling factors for shell and tube sides are 0.0003 m2.hr.C/kCal. 

 

The calculated overall U values in HYSYS and EDR are 2100 ans 2995 kJ/hr.m2.C, respectively. 


Edited by abolghasem202, 18 June 2019 - 12:15 AM.


#8 abolghasem202

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Posted 18 June 2019 - 12:13 AM

Hi Abul.

Just to follow your question I tried to input your data in hysys.

Other data should be known but, as a starting point, you can find attached the 1st trial output of the HE.

When you say "Aspen HYSYS predicts a heat trasnsfer coefficient of 8430 Kj/hr.m2.C", do you refer to the U value shown in the picture? (it is 16320 in my case)

 

 

 

 

Hi Gegio,

 

Thank you for your response.

I meant the heat transfer coefficient, signed by red color in the attached picture. I think the heat exchanger should be in rating mode to show the shell and tube heat transfer coefficient values.

 

The calculated U value in my simulation is 2100 kJ/m2.hr.C.

Attached Thumbnails

  • 12.jpg

Edited by abolghasem202, 18 June 2019 - 12:22 AM.





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