3 replies to this topic

[gauri]

For a 2 pass on tube side exchanger, we often design exchangers with pass partition plate horizontal. See figure 1 in the attached file.

Can we also design exchangers with vertical pass partition plates? It reduces the F Factor to zero. From the construction point of view, this might a problem because of the off centered nozzles on the channel side. But apart from that do you know any other reason for not having this type of arrangement?
Has any one ever come across an exchanger which looks like that in figure (2)?

 

 pass partition plate.doc   29.5KB   380 downloads

[Art Montemayor]

Gauri:

 

You cite the “F Factor” and I presume you mean the LMTD correction factor used in multiple tube pass shell & tube heat exchangers.  If so, then I believe you are seriously mixed up in regards to your heat exchanger background and application.

 

The F Factor is defined as the mean effective temperature difference divided by the LMTD.  It cannot have a value of zero.  Please refer to the attached information on the Mean Temperature Difference, page 27.  It is used in design to avoid a temperature cross in the exchanger.

 

Additionally, note that there is no mention of the nozzle orientations on a heat exchanger having any effect on the F Factor.  In fact, the only way to determine the F Factor is to employ the terminal temperatures as indicated on page 28.  Clearly, the terminal temperatures set the F Factor, and not the nozzle orientations.

 

I have fabricated shell and tube exchangers with the bonnet (or channel) partition baffle oriented in both vertical and horizontal positions – all depending on my piping configuration needs.  The operational results gave no problems.  I always located my nozzles on the bonnet such that they were perpendicular to the bonnet partition baffle.  I don’t recognize any of the problems you describe.

 

There may be a problem with inert gas accumulation in your channel or bonnet when using horizontal oriented nozzles.  For this effect, you need to have vent valves at the top of the channel or bonnet - one on either side of the partition baffle.

 The Mean Temperature Difference.pdf   390.66KB   2812 downloads

[AlertO]

Hi gauri
I think F factor you mentioned is F fraction distributed in the shell. This number can propably be high when the channel and baffle orientations arenot matched espicially with U-bend exchanger.
If your service is single phase, change the baffle cut to horiz, however, to change the channel to
vert is still OK , but quite less commonly used.

Hope this may help you.

[gauri]

Art, AlertO, 

 

I really appreciate your replies. But the "F- factor" I am referring to is the one from HTRI. It is associated with the pass lane clearance. To be precise it is the tube field pass partition bypass stream.

I should have mentioned it as F-stream instead of F- factor.

 

Regards,

Gauri