HEAT EXCHANGER DIMENSIONS

[picasa]

A shell and tube heat exchanger is typically denoted with dimensions like 23 X 240. I guess 240" is the tube length. Is 23" the shell I.D.? I am seeing several heat exchanger drawings where there this style is followed a little inconsistently. Sometimes the first number matches with the shell I.D. while sometimes in does not. For example for a shell with 25 1/8" I.D., it is denoted as 25 X 240

Please let me know as to how to decide these numbers.

 

[johnnymist2003]

Hi Picasa,
designation should be "x"-"y" where x=shell inside diameter and y=tube straight length (for u-tubes up to the the bend tan line).
John

 

[picasa]

So even if the ID is 25 1/16", the designation should be 25 1/16" - 240". For convenience you can not say 25" - 240".

Where is this rule written? Or is it just an accepted practice?

 

[asv80]

Picasa,
It is according to TEMA recommended practice. HX are designated with nominal diameter and nominal length.

Nominal diameter - inside diameter of shell, rounded off to the nearest integer.

Nominal length - actual length for straight tubes and approximae straight length from end to bend tangent in U tube.

 

[rmw]

Picasa,

Be careful. There is no guarantee that any mfg'r uses any particular standard or convention when giving the "nominal" dimensions of a Hx.

While some Hx mfgr's live and die by TEMA standards, others hardly use them, if at all.

While I think most are fairly consistent with respect to the diameter, the length can, as has already been noted, refer to the straight length only, ignoring the u-bends, or can include the overall outside dimension of the u-bends, but it also might be just the effective length of the straight portion of the tubes or the overall shell inside dimension, which might be essentially the same as the outside dimension of the longest u-tube bend.

I have seen all of the above over the years.

I always clarify with the mfg'r what their size denotes if I am unsure.

rmw

 

[picasa]

I think ASME should make strict rules on this issue to avoid confusion.

 

[rmw]

The problem is that no one standards propagating entity has total responsibility for all Hx's. A given Hx's construction might be governed by a combination of ASME, HEI, HTRI, TEMA, MIL-Specs, or possibly more, and potentially even none of the above.

rmw

 

[asv80]

This is only my guess, I maybe wrong.

TEMA designates size of exchanger to reflect the overall heat transfer area. The shell ID and the straight length of the tubes may indicate it. In some cases the U bends are not considered effective heat transfer surface area and that maybe why it is not included in the nominal length.

As TEMA is only a standard there is not legal binding on it and so manufacturers have varying representations possibly.

rmw and picasa - your comments please.