6 replies to this topic

[charlie_KC]

Hi all.

 

Apologies if this is in the wrong forum, as I am a student but I have a question directly relating to heat exchangers. 

 

I'm struggling to find information about the design of commercial/industrial helical coil heat exchangers online. Do helical coil heat exchangers used on plants usually have more than one tube? This seems like a stupid question, but all of the design papers I have read online (and most images of HCHE I have seen), only take into account the heat exchanger having one tube when performing calculations for the overall heat transfer coefficient. I am unsure whether this may just be because they are small-scale projects/laboratory experiments, or whether this is a common design for helical coil heat exchangers.

 

Many thanks.

[breizh]

Hi ,

Consider this paper.

Breizh 

[latexman]

From what I've seen inside the business unit I'm in, one helical coil heat exchanger has one tube/pipe.  I assume ours are medium size, and we have two types.  One type is installed vertically into a 20-24" flange.  They are made from 1.5" Sch. 10S SS pipe and are constructed onto a 20-24" blind flange.  They are 30-75 ft² each.  We do put multiple units into one vessel.  The other type is built permanently in a vessel.  I've seen 2" and 3" pipe used.  A helical coil is constructed with diameter greater than the agitator diameter and less than the vessel diameter.  Again, we do put multiple units in one vessel.  Bigger vessels get more units.

[IGC]

I've sized smaller heat exchangers with multiple coils e.g. < 20 ft2 each per coil.  In this case it was a pure-counter current LNG vaporiser (lng coil, water / glycol shellside). 

 

Coil wound heat exchangers can have thousands of tubes...

[Art Montemayor]

Helical and Spiral heat exchangers used to be some of my favorite items in applying heat transfer in the compressed gas industry as well as later when I went into cryogenics and subsequently into specialty chemical production.  I was intrigued by the heat transfer efficiency I could derive from them.  However, as usual, I discovered some trade offs as usual.

 

I've always found visual communications to be more accurate and specific than oral or written descriptions and for that reason, I've searched my personal engineering files and found the attached document.  I hope this helps to visually address your query.  I've designed and used the double Helical design and I presume that 3- and even 4-tube designs can be designed and employed - especially when compactness and higher capacities are needed.

 

The article that Breizh has presented is a good one and  was one that I used in the past and wanted to convert into a personal computer program to calculate future applications.  That was in the days of DOS and BASIC.  I never got the time or found the priority to do it in QuickBasic or later applications.  I would presume some one has by now.

 

I hope this helps.

Attached Files

•  How to Quickly Calculate the Length of a Helical Curve.docx   538.49KB   411 downloads

[M K]

Hi,

 

What about the velocity criteria for helical coil design, for heating and cooling purpose?

 

Thanks

[remi100]

Hi, 

take a look at the external heat convection correlation: Nu=C*Re^a*Pr^b*(mu/mu)^c

The values of constant C and the indices a, b, and c depend on the type of agitator.

 

Re depends of the velocities of the agitator.

 

its from chemical engeneering design, Gavin Towler, Ray  Sinnott p942 (12.18.3. Agitated Vessels)

 

Regards,