Shell and tube heat exchanger tube configuration

[Mech2325]

Hi all,
Q1)I need to know the selection basis of (1) traiangular (2) rotated triangular (3) square (4) rotated square tubes patterns of shell and tube heat exchangers.
Q2) When to use TEMA style "B" "C" and "D" style backing ring. I have always seem style "A" being used. On what basis are these backing ring styles selected??

 

[Jano6924]

You use squared or rotated squared arrangement when there is a need to mechanicaly clean outside surface of tubes, in such case you shall use a removable bundle design. If there is no need to clean outside of tubes then you can use triangular arrangement.

Same as you, I have only seen style A for backing rings so I cannot make a recommendation on this one.

Regards.

 

[Mech2325]

Jano6294: As per cleaning point of view, i know. My question is actually how to choose between rotated square and square. In rotated square, i have heard lesser number of tubes are accommodated pluse the pressure drop is more, so why employ rotated square??

 

[georgeverghese]

Believe 45 deg rot sq is easier to clean than 90deg sq. Also recommendation is to use 1.0inch tubes on 1.25inch pitch for cleaning considerations, rather than 3/4inch on 1.0inch pitch - in the oil and gas business.

 

[Mech2325]

georgeverghese: ok thanks. You mean to say that if the service is such that excessive mechanical cleaning is required, then the process department goes for rotated square and not square?
Plus what would be the selection criteria for triangular and rotated triangular??

 

[Afox88]

Sometimes rotated triangular fits more tubes than triangular. I go back and forth to see what fits better. I don't believe there is any other difference.

 

[SnTMan]

Generally correct that rating considerations drive square vs rotated square and triangle vs rotated triangle.

Style B, C, D backing rings are generally usable on any floating head unit. Style B may have larger required thickness than other styles, see the equations in RCB-5.141. Really, it is designers choice, but I have rarely seen other than style A used.

Regards,

Mike

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

 

[r6155]

Depends of mechanical or chemical cleaning. Also turbulence and heat transfer coefficient must be considered.

See

http://chemical-eng-world.blogspot.com.ar/2013/05/tube-arrangement.html.

Regards
r6155

 

[Jano6924]

You use rotated squared pattern when you want to increase the heat transfer coefficient on Shell side stream. Yes, with this pattern you will get higher pressure drop, but you have options such as modifying bafle type and bafle spacing and cut, or you can use a J Shell configuration.

Number of tubes between squared and rotated squared pattern is different, but it is a small difference.

When you design a heat echanger the goal is to get the smaller unit to do a given work (heat load). The primary "enemy" of designers is pressure drop, the lower allowable pressure drop the larger size of unit. You need to identify the "controlling" stream and that is the stream that will give you the smaller heat transfer coefficient, if this stream is in Shell side and need cleaning, the choices will be squared or squared rotated array only, this is true for Shell and tube exchangers.

Regards.

 

[Mech2325]

Thank you all for your valuable comments