Shell & Tube SIZING [tube velocity problem]

[baba33]

Dear all
I'm designing a shell & tube heat exchanger which it is supposed to be AES.
and it should only be 1 in parallel and series.
In periliminary design its sizes shell and Tube are 539-5500 mm respectively.
and its tube count is 367 with 0.75" Diameter. And my design spec do'nt let me to use 0.5" Diameter tube.
Tube velocity is 0.21 ft/s which is too low.
And also I know that may F type shell help, but F also has its difficulties. What can I do for this exchanger?

 

[SNORGY]

Hi baba33.

On what basis do you make the statement that 0.21 ft/s is too low?

If you have looked at the inside and outside film coefficients and the overall heat transfer coefficient and have indeed determined that you want to increase the Reynolds Number on the tube side, you might try reducing the overall number of tubes or, allowable pressure drop permitting, install tube inserts. Google Wolverine Tube for examples of good tube inserts.

 

[Latexman]

Take a look at 2 or more tubeside passes with less tubes.

Good luck,
Latexman

Need help writing a question or understanding a reply? forum1529

 

[srfish]

Is there a temperature cross? Can a u-tube be used? If so I may have an answer for you.

 

[baba33]

HI SNORGY

0.21 ft/s is low because heat transfer resistance in Tube side, more than 75%. and also it is much lower than recommended tube velocity 2 ft/s. I can reduce number of tubes but with reducing NO. of TUBES, heat transfer area also will be reduced.
And 0.5" tube diameter and tube internals are not allowed in the spec file.

U tube could not be used because Ft Correction to low for 2 pass tube.

I think only F type shell can help. Does anyone know what are main problems with this type.

Fluid quantity, Total kg/h 9735----10082
Vapor (In/Out) kg/h 0/0----4/9
Liquid kg/h 9735/9735----10078/10073
Temperature (In/Out) C 197.85/109.89----75.3/162.8

is there any minimum Reynolds for tube side? Because tube Reynolds is in the range of 300.

 

[Latexman]

If you can afford the pressure drop, N_Re > 10,000 is an accepted rule of thumb for turbulent design. What is the tube side fluid and properties?

Good luck,
Latexman

Need help writing a question or understanding a reply? forum1529

 

[srfish]

That is definitely a temperature cross which means there will have to be multiple shell passes. You asked about problems with F shells. The main problem is leakage across the long baffle that decreases heat transfer.