Thoughts on HX movement/modification ...

[mole]

Since I'm about 1/2 way thru the burning season I decided to take the back panel off the Seton and clean the tubes. I was pleasantly surprised to see very little buildup on them. I really believe by lowering and moving forward the HX I'm getting better heat transfer and less buildup on the tubes. The horizontal tubes are much easier to clean now also, and less chance of snagging the kaowool while doing so. Oh, and the kettling problem I used to have has not returned, even with 500F stack temps at times.

Pat

That's great it's working out so well! I gave up on brushing the top side of the upper row of horizontal tubes because I was tired of trying to stuff those hanging kaowool chunks back up into place. It irks me knowing they are dirty on top and I'm knowingly giving up some efficiency there.

 

[PassionForFire&Water]

something easy to do on your HX is to weld the return pipe on the left of the square header and the supply on the right side of the header. Now you have equal flow going in all the HX pipes.
It's called equalised reverse flow.

If the connections are in the middle of the header then the water will pe pumped in the most easy way. The flow pattern will most likely follow a Gauss distribution. Most of the water going in the middle pipes, less water in the outside pipes. This does not maximise the use of your heat exchanger surface.

It will not gain you 10% on efficiency, but it is easily done timewise and money wise

 

[ISeeDeadBTUs]

Not sure how I missed this thread last year, but it's a GREAT one!!

I think trying to force the smoke path along the ENTIRE length on the tubes and asCLOSE tothe tubes as possible are both great ideas.

I am contemplating a refractory topfor the primary combustion chamber (also becomes the bottom of the secondary) with a hole near the front. Yes, this part is similar to the 'new & improved" GW design. But where it differs is. . .

1)refractory COMPLETELY surrounds the tubes

2)Bypass isolates the tubes during damper closed and also during load door open

3)All rockwool/kaowool goes outside the refractory(Ideally, the insulation is enclosed within removable panels. Yep,this idea was borrowed from someone here )

4)Introduce secondary air near the front of the secondary combustion chamber.

I don't have a CAD program to draw this thing out. Might make more sense than my description does.

Back to the OP . . . I definitlyagree Patthat having the insulation touching the HX was a bad idea when they made these things. Refractory stays clen; insulation does not. What's your take on your improvements so far?

 

[Pat53]

Not sure how I missed this thread last year, but it's a GREAT one!!

I think trying to force the smoke path along the ENTIRE length on the tubes and asCLOSE tothe tubes as possible are both great ideas.

I am contemplating a refractory topfor the primary combustion chamber (also becomes the bottom of the secondary) with a hole near the front. Yes, this part is similar to the 'new & improved" GW design. But where it differs is. . .

1)refractory COMPLETELY surrounds the tubes

2)Bypass isolates the tubes during damper closed and also during load door open

3)All rockwool/kaowool goes outside the refractory(Ideally, the insulation is enclosed within removable panels. Yep,this idea was borrowed from someone here )

4)Introduce secondary air near the front of the secondary combustion chamber.

I don't have a CAD program to draw this thing out. Might make more sense than my description does.

Back to the OP . . . I definitlyagree Patthat having the insulation touching the HX was a bad idea when they made these things. Refractory stays clen; insulation does not. What's your take on your improvements so far?

Well, when I first went to clean the HX on this thing, I found the back (vertical) section of the tubes basically fused to the kaowool. Had to replace the whole back sheet of kaowool and that stuff is expensive. I noticed that when I put the back panel on after we built the unit, there was only a tiny airspace between the tubes and the kaowool, but I didn't really think it would be a problem. And the top row of tubes is also laying right against the kaowool, basically no airspace between them at all.

When you look inside the firebox, the tubes are ,for the most part, as far away from the exhaust path as they can be...why? Why not get them more into the flame path? I think the biggest reason the vertical tubes get so plugged up on these units is because it stays much cooler there and precipitates more creosote formation. . So my thinking was that changing the position of the HX to be moe directly in the flame path would increase heat transfer and keep the tubes cleaner. And it would obviously make cleaning the overhead tubes a lot easier as well.

After the modification, I have about 1.5" between the kaowool and the top row of horizontal tubes, and almost 2" between the vertical tubes and the kaowool. So far this is working well. I seem to be able to heat the storage tank up quicker and the tubes are definitely staying cleaner than in the past.

So I guess I would call the HX modification a success?

Pat

 

[Pat53]

Since I'm about 1/2 way thru the burning season I decided to take the back panel off the Seton and clean the tubes. I was pleasantly surprised to see very little buildup on them. I really believe by lowering and moving forward the HX I'm getting better heat transfer and less buildup on the tubes. The horizontal tubes are much easier to clean now also, and less chance of snagging the kaowool while doing so. Oh, and the kettling problem I used to have has not returned, even with 500F stack temps at times.

Pat

That's great it's working out so well! I gave up on brushing the top side of the upper row of horizontal tubes because I was tired of trying to stuff those hanging kaowool chunks back up into place. It irks me knowing they are dirty on top and I'm knowingly giving up some efficiency there.

Yup, I know what you mean, it was driving me nuts too. Since I was having the kettling problem last year anyway, it was a good excuse to pull the HX and hopefully fix the kettling problem, and change the HX position to try to maximize its efficiency at the same time.
Pat