Turbulator Performance Test

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What will be the flue temp w/o turbulators


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    18
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Nofossil

Moderator Emeritus
I'm going to do a test of turbulator performance, and I'll try this as a poll just for fun. Here's the setup:

I have a small EKO gasifier that predates the factory turbulators. I built my own - see picture below. I want to compare combustion vs. flue temperatures, with and without the turbulators. I've included a chart from last night's fire. Combustion is regulated (via fan speed) to stay close to 1200 degrees. Flue temp was about 500 degrees.

For my next fire, I won't have the turbulators installed. I'm looking for guesses, predictions, or bets about about how much warmer the flue temps will be for the next fire - probably tomorrow or Thursday.

Be brave. Be bold. Vote early and often.

turs.png

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Nofossil

Moderator Emeritus
Those numbers are for how much lower the temps will be?

I'm going 50 to 75.

What will I win? :)
What will you win? Lifelong honor and respect if not outright adulation!

Actually, the poll is for how much *warmer* the flue will be *without* the turbulators. Clarified in original post.
 

DaveBP

Minister of Fire
May 25, 2008
1,157
SW Maine
I also made some turbulators of my own. 2" wide zig-zag of some scrap 304 stainless sheet metal. My average flue temps dropped very nearly 100F.
 

huffdawg

Minister of Fire
Oct 3, 2009
1,457
British Columbia Canada
close to 100f if I recall correctly. I have chain turbs installed.. but it was a couple years ago now. I do get quite a lot of fly ash built up on them, almost to the point of blockage on the two middle firetubes at the bottom. need to clean out once a week or so.
 

chewy

Member
Nov 7, 2009
188
Indiana
I went against my normal urge to pick c and went with b.

I know I have had 900* stack temps on the smoke dragon before. The fire chamber must be close to 5000* with stack temps that high.
Erin
 
My estimate is turbulators will drop it by half.
I hope you get a chance to do chains.
Not sure how easily you can do this, but I appreciate the information. Testing with different diameter chains as well as stock turbulators is valuable information.
 
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taylorfarms

Member
Aug 1, 2015
35
new boston, il
I might have your suitable chain, i think the links are 1 1/4 or 1 1/2 across and 2 1/2 or 3" long, i think it is made out of 5/8 material. if you want them let me know how long and how many, we can give the usps flat rate box a whipping
 

rkusek

Minister of Fire
Mar 19, 2008
589
Nebraska
close to 100f if I recall correctly. I have chain turbs installed.. but it was a couple years ago now. I do get quite a lot of fly ash built up on them, almost to the point of blockage on the two middle firetubes at the bottom. need to clean out once a week or so.
100 vs. nothing or 100 vs. stock ones? I know yours would have had stock ones vs. Nofo's which came with nothing. His homemade ones look thicker than my stock. I have sworn my next cleaning will involve removing the claptrap and either re-hanging these or chains for easier removal.
 

jebatty

Minister of Fire
Jan 1, 2008
5,792
Northern MN
The chain turbs in my Tarm drop the maximum flue temp in the range of 100F + at high burn. The Tarm is operated normally, at fixed draft fan speed, no attempt to modulate the draft fan at all, the same as a normal burn. The maximum flue temp reached with turbs is about 235C (455F). I have a temp controller which is set to shut down the draft fan if it reaches 250C, as it cannot otherwise reach this temp based on the draft fan damper setting unless there is a run-away fire, such as could occur if I fail to close the bypass damper or fail to close the firebox door, both of which (embarrassed to say so) I have done.

The max flue temp occurs at high burn on a wood reloading during about the first 1/3 of the burn, with a good wood coal bed from a prior loading, internal boiler water in the 140F+ range, return water from storage at 140F+, so effectively little if any preheating of boiler return water.

During a burn flue temp also increases in relationship to the rise in temp of boiler return water, which is logical: hotter water in means hotter water out and also means hotter exhaust gases into the flue.

The chain I use likely is about what taylorfarms describes and is old barn cleaning chain. I haven't seen any place to buy chain like that.
 

huffdawg

Minister of Fire
Oct 3, 2009
1,457
British Columbia Canada
100 vs. nothing or 100 vs. stock ones? I know yours would have had stock ones vs. Nofo's which came with nothing. His homemade ones look thicker than my stock. I have sworn my next cleaning will involve removing the claptrap and either re-hanging these or chains for easier removal.
I havent tried the boiler with no turbs , I,ll give it a shot next cleaning.
 

Fred61

Minister of Fire
Nov 26, 2008
2,444
Southeastern Vt.
I used 3/8 chain from the hardware store because I didn't want to cut up my logging chains. Could be a little larger. 5/8 sounds about right.
Attached a large ring as a stop and a loop to catch them with a hook.

boiler turbs 001 resized.jpg
 
From what little testing I have done, I think the chain should be close to the tube diameter. Smaller is not a terrible thing, but you are trying to disrupt the boundaries of the flue gas stream. I suspect a chain works well because it is more irregular than a twisted turbulator.
I had some small chain and doubled it up in each tube in one test. It worked about the same as a much larger diameter chain that fit close but dropped in easily.
 

Nofossil

Moderator Emeritus
Fred - you have the same boiler I do, but newer I think. That chain is a lot bigger than what I have.

Tom - I don't have enough chain to double it up. My chain is about 1 1/4" wide, and the HX tubes are about 1 7/8" diameter.

I'll run the test with what I have, after the 'no turbs' test.
 

Nofossil

Moderator Emeritus
Moment of truth is unfolding!
I have a fire going now and it's reached 1200 degrees - the controlled combustion target. Watch on the 'Live control panel' link in my sig. Looks like flue temp is hovering around 570 - about 70 degrees above the last time. Still need to give it time to settle down.
 
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velvetfoot

Minister of Fire
Dec 5, 2005
10,091
Sand Lake, NY
Is 500F representative of wood boilers in general? That's a whole bunch above what my pellet boiler does.
 

Nofossil

Moderator Emeritus
Is 500F representative of wood boilers in general? That's a whole bunch above what my pellet boiler does.
I don't know. In this case, the EKO 25 has *very* short HX tubes. For some reason they made the firebox smaller when they made the nozzle smaller. If I were redesigning it, I'd add a little height to the secondary chamber and a *lot* of height to the primary chamber. Longer burns and longer HX tubes sounds like the right direction to me.

This temp is also measured in the center of the flue directly at the outlet of the boiler. My little magnetic flue temp gauge reads a lot lower - it's at about 275 right now.
 

Nofossil

Moderator Emeritus
Still plenty more fire to go, but it looks like 70 degrees is a pretty good number. When it's over, I'll pull both datasets into a spreadsheet and calculate the average for each. Here's a pair of screenshots with and without turbs. The dip is fueling after initial fire start.

With turbulators:
turbs2.png

Without Turbulators:
noturbs.png
 
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jebatty

Minister of Fire
Jan 1, 2008
5,792
Northern MN
Is 500F representative of wood boilers in general?
I can't answer for all boilers, but can provide some insight as to a Tarm Solo Plus 40 (140,000 Btu, my boiler), a Wood Gun E500 (500,000 Btu on a continuous burn basis), a Garn WHS3200 (500,000 Btu on a continuous burn basis), and a Froling FHG L50 (170,000 Btu).

First, keep in mind how logwood burns: low temp start, increasing temp to high burn (about 1/3 of wood load), temp starts to drop as move into mid-burn, low-burn, coals, fire out. Also, wood is of variable burn composition: moisture content, density, species, knots, etc.).

Second, some boilers have fixed draft fan speed (Tarm, Wood Gun, Garn) and some have variable speed draft fans (Froling). The amount of draft air through the burn has a great impact on burn rate and flue temp.

As mentioned above, my Tarm reaches a maximum flue temp of about 455F. About 1/3 of the burn will be in the 400-430F range, then falling into the 300'sF. I normally reload at about 350-380F if additional burn is needed. The Tarm reaches its rated 140,000 Btuh output at a flue temp around 420F. Flue temp above that results in higher than rated Btuh output, below that less than 140,000 Btuh output.

Both the Wood Gun and Garn experience a similar flue high temp, but both also tend to have a longer sustained burn time in the high 300'sF to low 400'sF, somewhat lower than the Tarm, and both typically are reloaded when flue temp drops into the low 300'sF, lower than the Tarm.

The Froling has a variable speed draft fan (and other fancy/sophisticated controls). During a sustained burn test period the Froling maintained flue temp in the 220-235C (430-455F) range, none of the much wider temperature swings of the other boilers.

About the only thing I know about pellet boilers is that the pellet fuel is quite consistent in btu content and burn characteristics, and therefore it is probable that a much more consistent burn profile can be engineered into a pellet boiler.
 
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