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Subject Author Date
Mount Best nicksanspam 07-21-2005
---> Re: Mount Best no_child_left_unleashed07-22-2005
| ---> Re: Mount Best Anthony Matonak07-22-2005
| | ---> Re: Mount Best no_child_left_unleashed07-22-2005
| |       `--> Re: Mount Best no_child_left_unleashed07-23-2005
  ---> Re: Mount Best no_child_left_unleashed07-22-2005
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Posted by on July 21, 2005, 10:56 am


There's a lot more than the lovely chest fridge at
http://tinyurl.com/cay4t.

The 80% wood stove might be more efficient with a concentric pipe chimney
with flue gas traveling up the inner pipe and room air traveling back
towards the stove in the space between the inner and outer pipes to make
a counterflow air-air heat exchanger with condensation, which might add
about 15% to woodstove efficiency and reduce air pollution and allow
burning wood with a higher moisture content with no efficiency penalty
(or maybe a gain :-) We might pressurize the stove air inlet slightly with
a small fan to assure adequate draft (given the cooler chimney) and to
regulate the heat output, and use a CO detector in case the inner pipe
develops a leak and the room air fan fails.

A heat pump with a 4-6 COP is nice, but a good solar heating system might
have a COP of 50 or more. John Christopher's CSI building in cold, cloudy
New Hampshire is heated with "98% solar power and 2% fan power." PE Norman
Saunders calculates that some of his solar houses will only need "purchased
heat" for a few hours every 35 years. No wood. No heat pumps.

The reflective solar heating system might lose lots of heat through windows
at night and on cloudy days. A low-thermal mass sunspace with an insulated
wall between the sunspace and the living space and warm air circulating
between the two and no airflow at night might be a lot more efficient. The
Barra system stores heat from sunspace hot air in ceiling thermal mass,
with little heat loss at night. A slow ceiling fan and thermostat might
bring warm air down from a low-e ceiling when a room is occupied.

As an alternative to a massy ceiling. Fin-tube pipes near the ceiling
could both collect and distribute heat from a stratified storage tank,
with the help of a ceiling fan. The tank might also have a $60 1"x300'
pressurized PE pipe spiral near the top to make hot water for showers.

Nick



Posted by on July 22, 2005, 1:30 am


> in the space between the inner and outer pipes

a tri-axial pipe? are you advising people to fabricate their own,
or you know a source?



Posted by Anthony Matonak on July 22, 2005, 2:21 am


no_child_left_unleashed@yahoo.com.sg wrote:
>> in the space between the inner and outer pipes
>
> a tri-axial pipe? are you advising people to fabricate their own,
> or you know a source?

Is it so difficult to fabricate such a thing? Take two single-walled
flue pipes of different enough diameters and place one inside the other.
Space them apart using bent pieces of metal or spring clips made from
coat hangers or the like.

Anthony


Posted by on July 22, 2005, 6:50 am


> Take two single-walled
> flue pipes of different enough diameters and place one inside the other

that's a co-axial pipe. A dozen commercial products use it. Flue
gases flow out, exchanging heat with combustion air.

Nick sounded as if (sometimes he posts without proofreading, I can
show you some posts where he confuses the dimensions of thermal
conductivity and thermal conductance) he was proposing a THIRD airflow
that would bring vent air into the living space.... a pipe inside a
pipe, inside a third pipe.

And yes, George, it's not a "new" idea. He didn't claim it was. By the
way, what's YOUR track record vis-a-vis optimizing thermal designs? If
you post half the tutorial material I've learned from Nick, I'll sing
your praises too.



Posted by on July 22, 2005, 2:42 pm



>> Take two single-walled flue pipes of different enough diameters
>> and place one inside the other
>
>that's a co-axial pipe. A dozen commercial products use it. Flue
>gases flow out, exchanging heat with combustion air.

Some gas appliances and pellet stoves work that way.

>Nick sounded as if (sometimes he posts without proofreading, I can
>show you some posts where he confuses the dimensions of thermal
>conductivity and thermal conductance)

Interesting. I don't recall those mistakes. I archive most of my postings at
http://www.ece.villanova.edu/~nick. If you send me a list, I'll fix 'em.

>he was proposing a THIRD airflow that would bring vent air into the
>living space.... a pipe inside a pipe, inside a third pipe.

No... just 2 pipes, with room air vs outside air flowing back to the
stove in the space between them.

>And yes, George, it's not a "new" idea. He didn't claim it was.

It may be new, but it seems obvious to someone "skilled in the art."

>By the way, what's YOUR track record vis-a-vis optimizing thermal designs?

George says he's an expert. Let's try an extremely simple test. If 10 cfm
of 70 F combustion air warms to 800 F before it exits a woodstove to enter
a perfect conterflow heat exchanger and 560 cfm of 70 F room air enters
the other end, what's the temperature of the room air at the other end
of the heat exchanger?

Anyone can answer, but it would be fun to let George give it a try first.

Nick



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