Flue 'spirals'

[lennardhme]

Hi all,
I'm making a vertical boiler for a 7 1/4" Dewinton. The design rules in Oz. are fairly good, so no problems there.
I have seen copper spirals inserted in fire tubes of vertical boilers to help slow the gasses down. Can anybody help with specs on the twist - say per 6" for this type of boiler and are they suitable/worthwhile/ any other info appreciated.
many thanks,
lennard

 

[GWRdriver]

Lennard,
I can offer a few comments, worth what you paid for them. I don't know of anyone in 7+ga in the USA who use them. If your flues are properly proportioned to begin with they should have an acceptable balance between gas velocity and heat absorption and not need enhancements. Also, if coal is the fuel, I see no way they could be anything other than a royal PITA. In small scales (Ga1, etc) flue turbulators are sometimes used because as often as not small boilers don't have well-proportioned flues (or more commonly flue) and some gas velocity reduction can be beneficial but in those instances cross-tubes or thermic siphons are far more effective.

 

[Maryak]

Lennard,
I can offer a few comments, worth what you paid for them. I don't know of anyone in 7+ga in the USA who use them. If your flues are properly proportioned to begin with they should have an acceptable balance between gas velocity and heat absorption and not need enhancements. Also, if coal is the fuel, I see no way they could be anything other than a royal PITA. In small scales (Ga1, etc) flue turbulators are sometimes used because as often as not small boilers don't have well-proportioned flues (or more commonly flue) and some gas velocity reduction can be beneficial but in those instances cross-tubes or thermic siphons are far more effective.

IMHO 110% correct...........can't even begin to think of the corrosion problems with solid fuel and incomplete combustion.

Best Regards
Bob

 

[kvom]

I don't know of anyone in 7+ga in the USA who use them.

http://www.chaski.org/homemachinist/viewtopic.php?f=8&t=87252&p=185326&hilit=turbulator#p185326

 

[Dan Rowe]

Lennard,
You did not mention what fuel you are planning to use. The thread linked in the last post was for propane which burns clean.

Anything that leaves soot or deposits on the tubes will be an issue I think. Dirty tubes do not have good heat transfer and if soot and residue are alowed to build up the spirals might get stuck in place making cleaning the tubes a major PITA.

Dan

 

[lennardhme]

Thanks Dan & others!

I will be using char for fuel. Have spoken with a lot of people who use this system, mainly used for smaller boilers or gas fired in larger. Some people using coal report good results, one in particular who is using larger than normal firetubes.- may explain why they work so well.
General concensus is that [as mentioned] with a properly designed boiler they are not required.

thanks for input.
lennard

 

[steamboatmodel]

I have used flue turbulators on full size equipment and they were a real pain. They would corrode and fall apart and you were constantly cutting and nicking your hands on them.
Regards,
Gerald.

 

[terrywerm]

I've seen them in one small commercial boiler that was fired strictly on oil, and they were nothing but a big pain in the keister. They would collect all sorts of crud on them and they needed to be cleaned regularly, which was where the pain in the posterior came in. It was a big fight to get them knocked loose from the inside of the tube, then clean them up with an air powered wire brush or something similar. Then brush the tubes and clean up the resulting mess before putting it all back together. I was never so happy as when management said that we could start removal of that unit, and it didnt' take long for us to get it the heck out of the building, either!!