Turbulator Performance Test

[Nofossil]

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.

 

[maple1]

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

I'm going 50 to 75.

What will I win?

 

[Nofossil]

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.

 

[NateB]

My guess is the flue temp will rise to 590.

 

[DaveBP]

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.

 

[Nofossil]

If I can find some suitable chain, I'll also do a test with chain style turbs. In that case, I'll post the results for this test, then start a new thread for the chains.

 

[huffdawg]

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]

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

 

[tom in maine]

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.

 

[taylorfarms]

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]

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]

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.

 

[Nofossil]

The only chain I have here might be a bit small. Here's a picture of it next to a turbulator and a tape measure. How does this compare with what others are using?

I need six pieces 18" or so. Donations happily accepted.

 

[huffdawg]

I use 3/8" chain. I welded the top link sideways to hang it in place.

 

[huffdawg]

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]

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.

 

[tom in maine]

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]

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]

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.

 

[maple1]

70, eh?

 

[velvetfoot]

Is 500F representative of wood boilers in general? That's a whole bunch above what my pellet boiler does.

 

[Nofossil]

Seems to be floating around 570 to 580 most of the time. I'll let it run a bit longer and post a two-hour screencap of the last fire (with turbs) and this fire.

 

[Nofossil]

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]

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:


Without Turbulators:

 

[jebatty]

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.