Questions about efficiency.

[warno]

As many of you know I recently built and started using my homemade boiler Found here https://www.hearth.com/talk/threads/im-building-a-homemade-boiler.145689/

My questions are about air flow and turbulators.

My heat exchange in the boiler is basically a 6" X 10" box about 7 feet long total. I'm wondering if I put some type of turbulator plates in my HX if that would help effeincy on my type of HX? What do you guys think? I would basically make up some stainless steel plates and put them in there standing up at an angle to slow down the flow of flue gases.

I'm also wondering if too much air flow is possible. I'm not sure how much CFM my current fan is running but it's a little draft inducer from a forced air furnace. I'm wondering if I add more air flow would help get a hotter burn? I have a way to get hot air up over top of my fire into the "smoke cloud" but my current fan doesn't have enough flow to drive it through up into the top of the box. I'm wondering about adding one of the following fans.

This one http://m.ebay.com/itm/Dayton-Model-...M-115V-60-50hz-4C446-/181950768455?nav=SEARCH

Or this one http://m.ebay.com/itm/181834044920

So my main question is it possible to have too much air flow?

Thanks for any advice in advance.

 

[maple1]

I'd say maybe to the turbs, and yes it's possible to have too much air flow.

The first would relate to heat transfer efficiency, the second would relate to burn efficiency. With a conventional unit (non-gassifying), you will be compromised in both by the basic design, so it would be a balancing act to tune it as best you can. e.g, too much air & you'll blow too much heat out the smoke pipe. Without an insulated (from the water jacket) secondary chamber, you likely won't get much of the smoke to burn.

Couple of things to measure to try to get a handle on those things - stack temps, & draft.

 

[warno]

Stack temps are easy to get but how would I go about getting draft measurements?

 

[velvetfoot]

I thought you had a barometric damper?

 

[maple1]

You can measure draft with a manometer - Dwyer Mark II Model 25 is a popular inexpensive one.

But to tell you the truth, I wouldn't know what it should be on a rig like yours. You could hook it up semi-permanently, and see what certain changes do to it. That together with stack temps might help you get things balanced. The price of having a unique beast, I guess.

 

[warno]

I thought you had a barometric damper?

No I did not add a damper of any kind on my chimney. Only air control in or out is my induction fan.

I will start taking temp readings as soon as I get my new infrared temp gun. And I'll go from there as a starting point.

 

[TCaldwell]

as stated above you will need the ability to monitor flue temps, combustion temps would be helpful as well. Too much mass air from your inducer can cause too much excess air, high flue temp but in certain situations can actually start to put the fire out causing combustion temps to drop. I don't remember the specifics of your combust or but if you have a insulated burn chamber you might be able to introduce secondary air to it. With what you have now i would consider a small vfd, 1 hp and under can be supplied with 120v single phase and a small 3ph motor. Both can be had from automation direct for about 300$, then you can experiment with fan speeds and watch your flue and combustion temps. You will see that you should be able to make a correlation between fan speed and combustion temp and control it with a pid controller. If you think you want to add secondary air, call me and I'll help you set it up. The temp measurements should be real time with thermocouples to watch the effects of fan speed changes at different stages of the burn.

 

[tom in maine]

A turbulator is very likely needed. Your hx is going to warrant some experimentation. The general idea is to get it stirred up and impinging on the hx walls. The stack temp will tell you how well you are doing.
A combustion analyzer is a great tool to give you a pretty accurate picture of what is going on. If you know anyone who owns one that tests wood combustion.

 

[STIHLY DAN]

Do they make a combustion analyzer for wood?

 

[TCaldwell]

Do they make a combustion analyzer for wood?

Sure do, my testo 329 does several fuels

 

[brenndatomu]

All this talk about turbulators here the last couple days got me to wondering about them, so I googled it. This is the first thing that came up. Some interesting designs and info on the different styles...http://fuelefficiencyllc.com/
(no affiliation with these people, i just found their site interesting)
I think I may look into some turbs for our 600k BTU gas boiler at work...tons of heat up the stack!

 

[TCaldwell]

you might try the folks at fuel effiency inc, clyde ny. They custom fab to your specs.