UHX Scope and Air Cooled HX tubesheet design

[Morcuse]

Greetings,

I would like to ask a question that has been bugging me for a few days.

I believe UHX-1 defines the minimum requirements for Shell and Tube Heat Exchangers. I'm guessing this means that for Air Cooled Heat Exchangers, the procedure of tubesheet design doesn't necesarily have to be followed. Is this correct?

PV Elite is asking me for Shell and Channel parameters while using the ASME Tubesheet option in CodeCalc. However, I don't think these will apply given that this is a forced draft air cooled heat exchanger.

How can I deal with the tubesheet component of the header? I understand that, since this is an equipment that will have to be ASME Section VIII Div. 1 "U" Stamped, it will have to be designed according to code, so I'm thinking of running calculations as per ASME Section VIII Div. 1 Appendix 13. I'm not entirely sure this covers the expansion aspect of the tubesheet design though.

What do you think? I've been looking for answers for a while, but most of the materials cover shell and tube heat exchangers only.

 

[SnTMan]

Morcuse, if your air cooler geometry, etc, is not within the scope of Part UHX (i.e. nominally circular tubefield, for one), you are wasting time fooling with it. Apx 13 does include provisions for perforated plates, i.e. tubesheet and plugsheet, see 13-6. PVE /Codecalc handles this reasonably well in my experience. Although differential expansion is not included in these calculation if I am not mistaken.

Maybe one of the aircooler guys will weigh in as well, I don't much mess with 'em.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[Morcuse]

Thank you for your reply SnTMan. This site has been incredibly valuable to me, since I'm an entry level mechanical engineer slowly falling in love with the pressure vessel code.

Now, regarding the Section VIII Div. 1 App 13, I understand it has its own limitations as well. If the header component of the Air Cooled Heat Exchanger has more than 2 stay plates, it seems to be outside the App 13-7(c) scope as well.

I'm curious to know if these types of headers have to be analyzed per ASME Section VIII Div. 2 with FEA software, because the equations don't seem to be applicable, for example, to an air cooled heat exchanger with 10 passes. PV Elite doesn't seem to be able to handle more than 2 pass partitions inside the header because these equations aren't described/defined in the App 13 of the code.

What do you think about this?

Roberto

 

[SnTMan]

Morcuse, again I am not that familiar with aircooler design, but I do know that box headers were successfully designed and built for many, many years without resorting to FEA techniques. Possibly the pass plates may be disregarded as stays in the header design.

As to the limitations of any particular software, well it's just software. It does what the programmers set it up for, no more and maybe way less

And welcome to the world of PV engineering. Warning, it can hook you

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[D2HANDLE]

Morcuse,

I think you need to look at 13-9 of App 13 which covers the calculation for rectangular vessels with stayed construction (partition plates act as stays).
Moreover, please read 13-9 (f)(2)which allows you to calculate vessels with multiple compartments by selecting the maximum dimensions of the compartment.

When you do codecalc , you need to consider the largest value of dimension "h" for the calculation.

Read the above clauses again and come back if you need further clarifications.

D2HANDLE