Alternative Power sources

Author

Heat Storage

Randy

2007-11-19, 8:25 pm

Hi,

I have a Tarm wood furnace. I want to run the output of this furnace
(hot water) into my cistern (a large, to be insulated, water tank in
the basement, not used for anything right now) I'm looking for some
information on DIY heat exchangers (water to water) and have not had
much luck. The basic concept is a copper pipe, or coil of pipe, but
how do I determine the effectiveness (ie. how long a length, flow
rate, BTU transfer rate, etc.).

I have a number of hydronic baseboard heaters that I could use. Would
these be more effective in water than in air? I have the specs for
them - how would I determine (short of experimentation) their
performance in water? Is there a rule of thumb?

I have searched under every term I can imagine and have found very
little practical information. Surely I am not the first person down
this road. If you could point me in the right direction, I would be
very appreciative.

Thanks,

Randy

Arnold Walker

2007-11-20, 3:25 am

"Randy" <murray.randy@gmail.com> wrote in message
news:6d88329b-ef81-42b9-b1fa-ef1edfca7ac3@i37g2000hsd.googlegroups.com...
> Hi,
>
> I have a Tarm wood furnace. I want to run the output of this furnace
> (hot water) into my cistern (a large, to be insulated, water tank in
> the basement, not used for anything right now) I'm looking for some
> information on DIY heat exchangers (water to water) and have not had
> much luck. The basic concept is a copper pipe, or coil of pipe, but
> how do I determine the effectiveness (ie. how long a length, flow
> rate, BTU transfer rate, etc.).
>
> I have a number of hydronic baseboard heaters that I could use. Would
> these be more effective in water than in air? I have the specs for
> them - how would I determine (short of experimentation) their
> performance in water? Is there a rule of thumb?
>
> I have searched under every term I can imagine and have found very
> little practical information. Surely I am not the first person down
> this road. If you could point me in the right direction, I would be
> very appreciative.
Type Tarm wood furnace
then key heat storage with your mouse at the
Tarm site.
They tell you whether you need a 600 gal or 1200 tank with a 200'
of 1/2 inch copper(probably K series) tubing with your model.
The insulated tank size and flow rate is more important than tubing area.
The next question is do you have a circulation pump,popoff, and check valves
for this system.
You already have the hydronic wallboards and controls installed?
Do you know how to braze/silver soldier copper,since you are doing that for
both the connections and
coil holder rods.
Liquid is better than air on heat transfer.
Tarm also has a installer's corner on that site that has prints for your
piping ,etc.
If you can read plumber's blueprints .....you are in business on your DIY
project.
They make a really good product....as long you have it installed right.

>
> Thanks,
>
> Randy
>

nicksanspam@ece.villanova.edu

2007-11-20, 9:25 am

Randy <murray.randy@gmail.com> wrote:

>I have a Tarm wood furnace. I want to run the output of this furnace
>(hot water) into my cistern (a large, to be insulated, water tank in
>the basement, not used for anything right now) I'm looking for some
>information on DIY heat exchangers (water to water)...

Why use water-water heat exchangers, vs circulating tank water through
the Tarm to heat the tank and through baseboard radiators or a fan-coil
unit (eg a car radiator :-) to warm the house?

With one pump and a Taco 561 3-way zone valve to bypass the baseboards?

Nick

Loren Amelang

2007-11-20, 5:25 pm

On Mon, 19 Nov 2007 17:35:28 -0800 (PST), Randy
<murray.randy@gmail.com> wrote:

>I have a Tarm wood furnace. I want to run the output of this furnace
>(hot water) into my cistern (a large, to be insulated, water tank in
>the basement, not used for anything right now) I'm looking for some
>information on DIY heat exchangers (water to water) and have not had
>much luck. The basic concept is a copper pipe, or coil of pipe, but
>how do I determine the effectiveness (ie. how long a length, flow
>rate, BTU transfer rate, etc.).

Google "heat exchanger ntu technique"... That's the estimation method
I've found to be simple enough to use and still decently predictive. I
don't know how to add the effect of the fins you mentioned, but I've
had good luck with smooth pipe.

Loren

Jim

2007-11-22, 9:25 am

<nicksanspam@ece.villanova.edu> wrote in message
news:fhuj4n$art@acadia.ece.villanova.edu...
> Randy <murray.randy@gmail.com> wrote:
>
>
> Why use water-water heat exchangers, vs circulating tank water through
> the Tarm to heat the tank and through baseboard radiators or a fan-coil
> unit (eg a car radiator :-) to warm the house?
>
> With one pump and a Taco 561 3-way zone valve to bypass the baseboards?

I'm still very impressed by the heat of fusion of glauber's salt being
released at 90*F; think I'd throw a buttload of that into my plans
somewhere, if I was him.

>
> Nick
>

dak@dakx.com

2007-11-23, 1:25 pm

On Nov 20, 7:15 am, nicksans...@ece.villanova.edu wrote:
> Randy <murray.ra...@gmail.com> wrote:
>
> Why use water-water heat exchangers, vs circulating tank water through
> the Tarm to heat the tank and through baseboard radiators or a fan-coil
> unit (eg a car radiator :-) to warm the house?
>
> With one pump and a Taco 561 3-way zone valve to bypass the baseboards?
>
> Nick

Well, for burning efficiency (i.e. no smoke or creosote) the Tarm
likes to run around 180F and 10-15 psi. They recommend an automatic
thermostatic valve that mostly recirculates the boiler water until the
input is up to temperature. This also protects the boiler from the
thermal shock of a sudden cold input. Don't know whether their
thermovar would be up to the task of continuously dribbling cold
cistern water through the boiler. It could perhaps oscillate and cause
damage.

The pressure helps keep oxygen out of the water for longer boiler
life. Copper, iron, or oxygen barrier PEX piping is recommended for
water going through the boiler. It would be difficult to pressurize
or keep oxygen from a large storage tank.

Tarm's 800 gallon tank uses two 120' 3/4" coils of copper pipe in
parallel. Each is about 3' high and 2' diameter. They are used in
both directions, a flap valve keeps water from the boiler when the
heating loops are circulating. Each is rated 26,400 BTU/hr at 3gpm
for 120F tank water. Probably one coil would suffice if you burn
softwood. But it also depends on the max temperature you want to run
the reservoir at - Tarm voids the warranty above 180F. Don't forget a
thermosyphon loop to extract heat if the power fails!

Car and truck radiators work well, but discarded round air
conditioning condensors are more attractive and make toasty
footstools

nicksanspam@ece.villanova.edu

2007-11-23, 5:25 pm

<dak@dakx.com> wrote:

>
>... for burning efficiency (i.e. no smoke or creosote) the Tarm likes to
>run around 180F and 10-15 psi. They recommend an automatic thermostatic
>valve that mostly recirculates the boiler water until the input is up
>to temperature. This also protects the boiler from the thermal shock of
>a sudden cold input.

The thermal part might happen without a heat exchanger.

>Don't know whether their thermovar would be up to the task of continuously
>dribbling cold cistern water through the boiler. It could perhaps oscillate
>and cause damage.

What's a thermovar? You might run the pump with a 3-way heatmotor zone valve
for mixing.

>The pressure helps keep oxygen out of the water for longer boiler life.

You might use a cast iron pump with a 1/2% solution of ACI-100 corrosion
inhibitor from D. W. Davies.

>Tarm's 800 gallon tank uses two 120' 3/4" coils of copper pipe in parallel.

An STSS tank.

>... Tarm voids the warranty above 180F.

The EPDM tank liner only works to 170, long-term.

Nick

John Barry

2007-11-24, 5:25 pm

Randy,
Another factoid of note (TM):
Counter-flow heat-exchanger will be much more efficient than "normal"
parallel-flow, in that, if properly sized for flows & temps, the
discharge temp of each loop will closely approximate the input temp of
the other loop. (This is common with air-air exchangers I've looked at.)
Downside: need (2 ea) loops w/pumps, to run the coldest of the cold
reservoir into the exchanger, with the discharge of that loop to the top
of the cistern.
HTH,
John

Randy wrote:
> Hi,
>
> I have a Tarm wood furnace. I want to run the output of this furnace
> (hot water) into my cistern (a large, to be insulated, water tank in
> the basement, not used for anything right now) I'm looking for some
> information on DIY heat exchangers (water to water) and have not had
> much luck. The basic concept is a copper pipe, or coil of pipe, but
> how do I determine the effectiveness (ie. how long a length, flow
> rate, BTU transfer rate, etc.).
>
> I have a number of hydronic baseboard heaters that I could use. Would
> these be more effective in water than in air? I have the specs for
> them - how would I determine (short of experimentation) their
> performance in water? Is there a rule of thumb?
>
> I have searched under every term I can imagine and have found very
> little practical information. Surely I am not the first person down
> this road. If you could point me in the right direction, I would be
> very appreciative.
>
> Thanks,
>
> Randy

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