In search of FREE btu's....(ME)

Mark Eatherton1

So there really is no such thing as free BTU's. The grey water waste heat recovery project (a.k.a. The Duncan tank), while admirable is not performing up to my expectations. I think its running a gross efficiency of around 50%. (I know, you told me so...) But hey, if a feller didn't try, he'd never know what his potentials were, right?

Upward and onward. I now have in my possesion a nice copper heat exchanger that is aching for a new home. When I get back from a badly deserved spring break in San Diego next weekend, I'm going to eliminate the grey water tank, and move the HXer to the exhaust gas pipe of my Munchkin T-50 condensing boiler! I will then have the first field model of a SUPER condensing hydronic heat source. This will be a quick conversion. Other than a few PVC fittings and some pipe, I have everything I need to make it work.

I will monitor the flue gas delta T, the water side delta T and the gallons of condensate, as well as its temperature to judge additional efficiency.

I am open to suggestions as it pertains to this project.

Fire away wallies.

ME

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Heatermon

Whatcha doin in my neighborhood ME

Where you headed down here? If you are doing some research on free B.T.U.'s, you're coming to the right place at the right time. Got my shop solar up to 180 degrees yesterday. If this is spring, I don't want to see summer. Have a great time here and if you've got some free time give me a call.

Heatermon

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Larry Weingarten

BTU storage?

Hello: A question(s). Where will you put those captured BTUs? Do they go into a tempering or pre-heat DHW tank? I've done a similar thing with exhaust from a generator. All that comes from the exhaust is cold condensate. Do you worry about heat exchanger corrosion like I do?

ps. If you feel like a side trip to Monterey, you could see it in person!

Constantin

The pink panther rides again.

... well, at least I thought your system diagrams showed pink connectors, but cranial cobwebs, a vivid imagination, and/or too much time spent reading neat articles on the Wall may have colored my memory.

More to the point, I think your previous and coming projects are great. It's well thought-out, impromptu research like yours that makes this place as interesting as it is. Please keep up the good work and keep us in the loop as far as your results go.

Speaking of which, do you suppose there may be a market for someone to develop a universal side-vent kit for non-condensing oil/gas boilers? If it's made of the right materials, it should withstand the corrosion and may be an interesting market opportunity considering how many oil-fired non-condensing oil boilers are in use today.

Glen

free btu

My first boss was a great "experimenteer" - and would wrap copper tube around darn near anything that was hot to glean the btus out of it. I think tinkering in this fashion is a prerequiste to this trade. Without going to too much expense - and I'm thinking out loud - could the condensate be used as a heat source for a mini geothermal type heat transfer/recovery? Perhaps that would depend on the volume of condensate available - so that the latent heat recovered would be equal to (or better than) the cost of recovery. Re your first example - our local hospital had just the same idea. Recover heat from waste water from the laundry - as it turned out - the liability of domestic water in close proximity to the laundry waste (and the potential for cross connection/contamination) was too much for the hospital board to continue with the practise.

Cliff Brady

GFX

Is that your copper GFX you are going to use on the exhaust? What water are you going to run through the half inch copper, return water? I didn't know copper was compatible with acidic condensate. Why didn't you leave the GFX on or put it on your waste stack? Do you think a gang of two GFXs on the stack would get the BTUs you are after at a lower investment?

hr

Vent your munchkin

With the AL 29 stainless then wrap coils around the vent? Can approved stainless vent be used on a Munchkin? Thought I heard it can be used onn the Viessmanns now?

Might be better transfer than PVC adapt-sions

hot rod

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Mark Eatherton1

I'm going with the wife...

She in A.W.W.A. conference. I'm planning on practicing becoming a beach bum:-)

We're staying at the Westin Horton Plaza hotel. Give a call if you'd like.

ME

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Mark Eatherton1

The captured BTU

> Hello: A question(s). Where will you put those

> captured BTUs? Do they go into a tempering or

> pre-heat DHW tank? I've done a similar thing

> with exhaust from a generator. All that comes

> from the exhaust is cold condensate. Do you worry

> about heat exchanger corrosion like I do?

>

> ps.

> If you feel like a side trip to Monterey, you

> could see it in person!





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Mark Eatherton1

The captured BTU

> Hello: A question(s). Where will you put those

> captured BTUs? Do they go into a tempering or

> pre-heat DHW tank? I've done a similar thing

> with exhaust from a generator. All that comes

> from the exhaust is cold condensate. Do you worry

> about heat exchanger corrosion like I do?

>

> ps.

> If you feel like a side trip to Monterey, you

> could see it in person!





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Mark Eatherton1

The captured BTU

will be stored in a preheat tank, 40 gallon. Yes, I worry about the pH of the condensate causing havoc with the HX. Thats why it won;t be there for more than a month or so. Just a little experiment.

ME

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Mark Eatherton1

Cliff...

the GFX was never installed in my main stack. Won't fit.

And you are correct, its NOT compatible with the pH of the condensate. I'm sure that 2 would be better than 1, but can only afford one.

I'm circing potable water through the 1/2" tube into a 40 gallon preheat tank.

ME

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Mark Eatherton1

That IS correct...

for vertical venting only. How much for the prototype HXer?? I like your style:-)

As we've stated before, its a DARNED good thing we don't live in the same neighborhood...:-)

Say hey to the missus and young mister.

ME

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hr

ME, that coil of stainless

is something I salvaged out of a soda dispenser, years ago. Never got around to doing anything with it. Be glad to sent it your way. It is a nice snug fit on that 3" ss vent pipe.

hot rod

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Kal Row

Real intelligence

is learning from other peoples experience, so keep these brainstorm projects coming, we love it and thank you

paul lessard_3

I was thinking

Along those lines with a voyager last week

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jerry scharf

do we have a chance for >100%

Mark,

I know it's not what you're doing, but it's worth a smile.

Hmmm, say you have combustion mix coming in at 70F and you have cold water coming in at 55F. With a longer exchanger with the water run from the exhaust side back toward the munchkin, you might be able to get the exhaust temp down to 69F. It's would require yet more plumbing, but being able to switch from a two stage system (flue to storage, storage to preheat) to a one stage system when the water's flowing and the burner's burning could give really nice numbers.

On a more practical vein, how much intake/exhaust pipe do you have on your munch right now? If you can afford the drag, mounting some vortex generators (VGs) in the exhaust pipe of the HX would make a big difference in the heat exchanged. With laminar flow and fairly high velocities, I'd worry that the center part might not get much cooling. If you're not familiar with VGs, they are those funny tabs you see on the tops of airplane wings. They produce turbulence which make the wings have better stall characteristics with modest drag.

If you want to go with the VGs, here are some rough numbers:
In a 3" pipe, you only need 1.5" turbulent layer to mix the whole thing. .5" high by 1" long tabs alternating pitched at about 10 degrees to airflow mounted on the pipe surface would do this. Given the small circumference, it's hard to imagine needing more than 4 tabs. I'd need to know the velocity to figure out how far down the tube the turbulence would propogate.

Another alternative would be to put two wires in a + across the face, put some tabs off the wire in an alternating form. It's easier to install and remove, but I'm less certain of the flow characteristics. I can work up some more on this if you're interested.

once again, it sounds like fun.

jerry