On 30 Jun 2006 17:20:16 -0700, "AndyS" wrote:



Here is a suggestion that you might consider.... Wall off a closet
sized part of your garage, either with cheap panelling or maybe
plastic curtains, and get a Home Depot $70 air conditioner to use
just for that part..... Also good for space heater in winter....

Isolating a small volume from the garage makes sense since now the
thermal resistance of the external wall and the closet walls are in
series, thus reducing the heat leakage from the outside to the
operating position and hence, reducing the heat that needs to be
removed by the air conditioner.

Since the closet walls are much smaller than the garage wall inside
dimensions, for a specific amount of isolation material (and cost)
much better isolation can be obtained by isolating the closet than
isolating the whole garage.

Perhaps you can make sliding curtains like they do around hospital
beds..... A little 5000 BTU unit will cool the hell out of a small
closet-like
area, even if it is poorly insulated and leaks like hell.... The air
condx
can be mounted on a little dolly or something......venting into the
rest
of the garage. And slid off on the side when not in use...

Venting into the rest of the garage does not make sense, especially
with light closet walls, since this would be equivalent to an electric
or acoustic short circuit.

If you look at the situation from the rest of the garage, the heat
from the closet will enter the larger garage space, as well as the
power required to run the air conditioner, as well as the leakage from
the outside world through the garage walls.

The rest of the garage will get very hot and if the closet walls are
light, leak back into the closet, requiring more air conditioner power
to remove it etc. The temperature of the rest of the garage will
continue to rise, until the temperature is sufficiently _above_ the
outside temperature and sufficient amount of thermal energy will flow
_out_ through the garage external walls.

Two ways to avoid this problem, one is to let the closet air
conditioner pump the heat to the outside air or if the heat is pumped
into the rest of the garage, at least open the garage door and use
sufficiently good isolation in the closet walls to keep the air
conditional power requirements at a reasonable level.

After all, air conditioning is a similar problem as thermal management
in any semiconductor systems, which use the analogies with
resistances/conductances (thermal isolation/conduction) and
capacitances (specific heat x mass).

Paul OH3LWR