These are all great ideas! Keep 'em coming!
Here are some thoughts I have on ideas I saw
above, both the air-cooling and water-cooling
ones:
Butane and Recharging
I myself will definitely be sticking to the options
that don't involve silver soldering, recharging
the refigerant, etc...but I can certainly pass on
any ideas in that category to any folks here
who actually have tanks of nitrogen, torches,
etc!
Blowing Air Through the Evaporator Coils
In the category of cooling the air directly with
the fridge's evaporator, many of you are
doubtful that the amount of cooling offered
would be at all useful (or that the compressor
would die if it were). Fair enough.
It occurred to me that it's not actually
that hard to try and could be done without
disassembling the fridge at all. Refining
ideas from 2 posters above, one could:
1. take a typical cube-shape dorm fridge
that has a freezer tray,
2. place it in a window with the
condenser coil and compressor sticking
outside
3. seal the whole window area around the
fridge (as well as the rest of the room!)
4. remove the door of the fridge
5. replace the door with a thick, door-sized
piece of wood, sealed around the edge of the
fridge opening with weatherstripping or
the rubber gasket from the original door.
the piece of wood has one hole (say 4 in diameter)
about where the freezer cabinet is, and one hole
(say 4 in diameter) lower down.
6. blow the warm air from the room into the top
hole (e.g. with a short corrugated duct pipe going
up near the ceiling, and a blower)
7. place some sort of baffle inside the fridge
that forces that air to move over the freezer
tray before it can escape out the lower hole.
perhaps augment the freezer tray with
fins (gee just like the 50s).
8. theoretically cool air will come out the
bottom hole.
9. theoretically the compressor will be
running continuously
10. see if the compressor gets very hot and
if so rig up some kind of air or water cooling
mechanism outside.
This method has the advantage that we don't
have to take apart the fridge, and we can take
advantage of the fridge walls' insulating properties
to keep the outside heat out.
This method also gets around the problem one
poster mentioned--that many cheap fridges have
some of their evaporator coils embedded in the
fridge wall and are hard to get out.
Freezing Water with the Evaporator Coils
In the category of using the fridge to cool
water and then blowing air over copper tubes
or a grille full of the cool water, a similar,
slight refinement of an above idea occurred:
1. start with any fridge that has a freezer tray
2. place it in a window with the
condenser coil and compressor sticking
outside
3. seal the whole window area around the
fridge (as well as the rest of the room!)
4. find the largest bucket you can that fits
inside the fridge
5. fill the bucket with water [optional: put
in antifreeze, glycol, or salt for better chillin']
6. place the bucket inside the fridge such that
the freezer tray is submerged in the water.
this may involve slightly bending the freezer
try and evaporator coils wrapping the freezer tray,
or finding a wacky-shaped bucket.
7. now rig up a small circulation pump that pumps
water out of the bucket, sneaks through the
insulation of the fridge door, leads to
a copper coil or grille attached to the front
of a fan sitting right on top of the fridge,
and then sneaks back through the
fridge insulation to empty back into the bucket.
This is essentially a fridge-powered version of
this very funny college-dorm budget aircon unit:
http://www.eng.uwaterloo.ca/~gmilburn/ac/
The advantage of this is, again, there is no
need to disassemble the fridge (much :) ) and
we can use the fridge's insulation to perhaps
keep the ice cold longer if we intend to
"store up ice" overnight and then use it
the next day.
One slight problem might be if the entire bucket
freezes and there is no water to circulate!
Why is the water-based solution better?
There is a more general matter though that
I was hoping the engineers here could explain:
At an intuitive level there's something odd about
the water-based solution: assume for the moment
that we do NOT store up ice when it's cool
out, and only run the system when it's hot out.
It seems like any time we add more mechanism
between the evaporator coils and our air, we're
just going to add heat and waste potential cooling
(from 2nd law of thermodynamics). If the
compressor would die if we tried to blow warm air
past the evaporator coils, then that means
either a. the compressor would ALSO die with
our water-based solution, or b. our water-based
solution must cool much less effectively than
blowing the air right over the evaporator coils.
Have I missed something here? Is there something
magical about going via water/ice that makes
the water-based solution overall more effective?
Something about the operating temperature ranges
of the components involved? I'd like to understand
this better.
Does the water-based solution ONLY make sense
if we also take into account the ability to
"store up cold" overnight? Or would it offer benefits
over an air-based solution in either case?
Wells, underground tubes, and thermal mass
As to using the thermal mass of the ground
to cool (e.g. via a well or underground pipes),
yes I have also considered that and of course
it's always good not to require electricity for
cooling! Some, but not all, folks around here do
have wells.
I hadn't pursued that avenue much because
I was assuming that the cooling ability
of well water would always be significantly
less than that of a fridge (which in turn
would be significantly less than a real aircon
unit), but please correct me if I am wrong
there!
--
Thanks again, keep the cool ideas coming!