brock turbulator results for garn

[TCaldwell]

Received brock turbulator, 9' long came in 2 pieces , it fits in the last pass hx tube before it leaves the appliance, the tube is 5" diameter. the turbulator basically is a 3" piece of flat stock that is bent in a zig-zag pattern touching the hx pipe at each bend, about every foot. I used 2 thermocouples, one at each end of the last pass hx tube approx 10 ft apart from each other with the turb inbetween, i recorded temps of each thermocouple at 100deg intervals based upon a thermocouple in the secondary burn chamber, i used 1600, 1700, 1800,1900deg temps as markers for the turb readings cause this is the realistic range the garn operates. then i subtracted the 4 differential temps at each reading, added them together and divided by 4 , thus equaling the average differential temp between the two thermocouples in the last pass from burn at 1600, to 1900deg, i hope charts will explain.


no turb 4.5' turb 6.75' turb 9.turb
1600 413-344 425-324 409-288 414-286
1700 448-371 440-330 410-292 418-296
1800 458-378 454-336 427-299 437-301
1900 476-392 471-353 428-303 442-305
ave diff 77deg ave diff 111deg ave diff 123deg ave diff 130deg between 2 hx tube thermocouples

the 4.5' turb drops the ave flue temp by 34deg over the no turbulator , the 6.75 by 45deg and the 9' by a 52deg ave under the stock no turbulator set up. these were all run at 60hz/3450rpm. All of the different lengths were able to allow the garn to reach temps of over 2100deg in the secondary burn chamber, so i guess the added back pressure was minimal, however with th 6.75 and the 9' the flue stack condensation was present for almost the whole burn, maybe more efficient but for now with 20/25% mc wood i will stick with the 4.5' turb. also the starting boiler temps were around 160deg. Next week i will try the same tests monitored with a combustion analyzer and see what gives. thats all i got for now, would welcome any comments.

 

[heaterman]

What really is your purpose for installing the turbulators? I'm assuming efficiency and willing to grant that you can pick up a point or two....maybe more. The issue as you have already noted is gaining the efficiency at the risk of flue gas condensation. Anytime you start getting flue gas temps from a solid fuel fire near 300* you are on thin ice. There's too much variation in air dried wood to run that close to the edge....again, as you probably already know because you seem like a very intelligent person. So, are you like me? a hopelessly chronic tinkerer that just has to play with stuff? Or do you see some design flaw in the Garn that makes you think it's wasting a lot of wood?

 

[TCaldwell]

heaterman, no design flaw, just tinkering to understand the limitations as built. i do think that the 1 turb is a small safe increase again depandant on consistency of fuel. as you stated the other 2 longer turbs are too risky,

 

[jebatty]

As mentioned in past posts, turbulators should achieve 100+/- flue temp drop, which roughly translates to 2-4% increase in efficiency. I made my own from heavy chain, just hung in the hx tubes of my Tarm. Since I had old barn cleaner chain, the cost was $0. Operating flue temp with a probe thermometer is between 375-500, with 400-425 during the bulk of the burn, easily a 100 temp drop from pre-turbulator operation. I burn almost all pine. No problem with condensation, creosote, etc.

Really nice to see your actual data. Keep up the boiler research.

 

[steam man]

Good data collection. I was involved in a study one time to look at the tube metal temperatures in a dual fuel boiler water tube boiler. We just welded thermocouples to various points for data collection. It was interesting to see what really goes on. Sometimes you have to wonder how much the OEM guys study their own product for improvement. Since the boiler stack temp needs to stay above condensation I am sure the designer would usually try to keep a fudge factor and allow a certain amount of wasted energy especially since the wood fuel load is so variable. I've read the post on O2 trim control which can be somewhat pricey but the way we are probably heading. This post made me wonder if a boiler could be designed around turbulators that can be modulated somehow, maybe how much they are extended in the fire tube. That made me think that another possibility would be to just modulate the fire tubes by turning them on/off in sequence to control stack temp. Obviously there would be back pressure issues to solve. Comments on this?

Interesting.


There's nothing time and money can't solve.................

 

[jebatty]

Interesting idea; bimetallic turbulator strips which twist, untwist, in response to temperature. But I think turbulator design in theory is a little more complicated than this, as the theory is to maximize the highest temp temp gas molecules in contact with the walls of the hx. More/less twist may or may not actually accomplish this.

 

[steam man]

Interesting idea; bimetallic turbulator strips which twist, untwist, in response to temperature. But I think turbulator design in theory is a little more complicated than this, as the theory is to maximize the highest temp temp gas molecules in contact with the walls of the hx. More/less twist may or may not actually accomplish this.

I was thinking of ones that can adjust their length according to stack temp. But anything could be considered. As long as we are going out on a limb here everyone may as well see this: (broken link removed)

 

[TCaldwell]

steamman, i actually talked to fluemiser in november, he says these are very effective for 500deg + flue temps and marginal under that. They hold about 2 gallons of water.