are a bit useless, as when you need most heat, they work less well
and at about minus 5, pack in altogether. This down to the
refrigerant gas used.
However there is a new technolgy one out now, runs on CO2 refrigerant
and works to much lower outdoor temperatures. Sanyo.
No it's not, it's down to the outside unit (evaporator) icing up.
Mine won't work effectively between about +5C and 0C outside because
it has to keep running defrost cycles, but once it's got down to -2C
and lower, it again works fine, because most of the moisture has
already dropped out of the air by then as frost or frozen fog, and
doesn't clog the evaporator. IIRC, I tried it down to something
like -8 or -10, and it still chucks out lots of heat inside.
[email address is not usable -- followup in the newsgroup]
On Wed, 22 Jun 2011 01:57:26 -0700 (PDT), Matty F wrote:
I can see the thinking but it can't be that simple can it?
Yes when you compress air it gets hot so extract that heat before
letting it go outside. But where has the energy that has made the air
hot come from? Do you get significantly more energy out of your "hot
air cooling radiator" than you have put in via the compressor?
I believe we are on to something here. The motor of course uses
energy. I'd have a motor that uses about a kilowatt and compress air
from inside the house and run that through radiators, then outside to
a nozzle where the air escapes and gets very cold. Need to allow for
icing up, and the hissing noise it would make.
My house is leaky enough that more air will come back in.
Or air could be piped in past a radiator.
I don't need a lot of heating. It's winter here and I have not used a
heater so far this year.
you ill indeed see gains. The clue is that the air going out is colder
It is in fact an air sourced heatpump.
Instead if the 'warm' air heating the regfrigerant you simply use the
warm air outside itself.
to collect heat from the outside it has to expand and cool below ambient
It then heats up in the heat exchanger that is outside.
You then compress it which makes it hotter and push it through the internal
heat exchanger where it cools.
Then you expand it again, repeating as required.
Now it would be possible to take in fresh air, expand it to cool, heat it in
the heat exchanger and then compress it and release it in the inside
However it has problems, including..
no lubrication for instance unless you plan on throwing away the oil every
condensation inside the expansion vessel as it cools.
noise caused by the release of the compressed air.
more difficult to control the flow rates so the air expands/compresses in
the right place.
There is no need for it condense.
If you expand a gas it cools (Boyles law), it is then colder than the
outside air so will absorb heat from the outside.
Then you have to pump it into the inside and compress it, this heats it up
and it releases the heat it had absorbed.
If you don't expand it first you wont get much heat transfer.
It is somewhat easier to make a system work if it does condense as it is
easier to control the flow rates, all you need is a capillary tube.
its a simple physics problem. There are three paths into and out of the
air in at outside temp.
air out, colder than outside.
Total heat is electricity in + (specific heat of air times air flow rate
times temp difference between inlet and exhaust air). As long as that
difference is there, then some heat has been pumped from outside to inside.
How you do it, is only a matter of efficiency.
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