2 replies to this topic

[Alaaeldin55]

Hello,

 

I have a problem in calculating the heat transfer area required in a shell and tube heat exchanger. The problem states that only 90% of heat given up by hot fluid is recovered by cold fluid. I have calculated the overall heat transfer coefficient (U) and the logarithmic mean temperature difference (delta T). The quetion is, should I use equation 1 or 2 to find the area ?

 

 aa.jpg   24.5KB   2 downloads

 

Many thanks

Edited by Alaaeldin55, 23 May 2016 - 05:49 AM.

[emmanuelv2012]

use equ 1 because the heat given off by the hot fluid is given off on the heat transfer surface area after which 90% of the heat on that area is transferred to the cold fluid......the 90% should be used when dealing with heat gained by the cold fluid...as d heat gained by the cold fluid would now be 90% of the amount of heat on the heat transfer surface area.

I hope this helps...

[Mahdi1980]

Alaaeldin

You should study enough about shell and Tube heat exchangers.

In designing a desire HX, the below items to be considered:

1- F which is a correction coefficient for Heat exchangers and it depends on the number of tube pass and Shell and also direction of flow regimes.

 It could be found in heat exchangers handbooks: So, it introduces in the first formula : Q =F.U.A. DT_ln

2- Fouling factor has a significant role in determining the proper surface area.

   The fouling factor impacts on the overal heat transfer coefficient and reduces it. So, from the first equation the area will be increased.

Finally, concerning the above parameters, you can calculate the real area to recover the total heat from the hot fluid.

 

Mahdi