I just did a google search for the following:
"water circuit" air conditioner
water tower air conditioning
I found information on two types of AC systems which use water circuits
to transfer heat. The first was used mostly in large boats / yachts.
These people use closed circuit fresh-water circuits to directly
distribute heat to / absorb heat from different parts of their yachts.
One such system is described at the following web page:
http://mail.veco.net:82/veco/sito/fai_da_te/eng/ac1.htm
On that web page, they describe three types of systems:
1) Direct expansion, single room unit. Pretty much a standard window AC
made for marine use.
2) Central compressor, direct expansion. Basically a multi-split.
3) "central systems with chilled (or heated) water distribution to
several fan coils "
The THIRD system is the one I am interested in. It would be equivalent
to putting almost everything AC-related outdoors. A water circuit would
just come indoors, and pass through a fan-assisted radiator. A small
radiator is capable of doing the job; I know of people who cool large
areas (sucessfully!) by passing well water through a truck radiator.
The water just has to be kept cold enough (well-water temperature is
fine). Anyway, onto the second type of system.
The second type of system relies on a cooling tower, and is often found
in large commercial buildings or hotels. I've actually seen these
before and talked to some people who service them, so I don't know why
I didn't remember them earlier. It's fairly similar to what we were
talking about with the cooling circuit on the porch, though there are
some differences. Here are the basic principles, which I've just copied
and pasted from another site:
- A cooling tower blows air through a stream of water so that some of
the water evaporates.
- Generally, the water trickles through a thick sheet of open plastic
mesh.
- Air blows through the mesh at right angles to the water flow.
- The evaporation cools the stream of water.
- Because some of the water is lost to evaporation, the cooling tower
constantly adds water to the system to make up the difference.
That is actually just one type. There are both direct (open circuit)
and indirect (closed circuit) versions. A good source of basic
information about them is:
http://www.cti.org/whatis/coolingtowerdetail.shtml
With an direct (open circuit) cooling system, only regular water can be
used in the circuit, because it will constantly be evaporating and
being replaced. So the fins would probably need to be plated with
something which is corrosion-resistant. With an indirect (closed
circuit) cooling system, the main cooling circuit doesn't have to be
filled with water, and an anti-corrosion additive could be used.
Now, the "usual" purpose of these cooling towers is to increase
efficiency. But for me, it has the side-effect of letting me place the
AC indoors, with the hot fins being cooled by the water stream. I have
a feeling that THIS system would be best in efficiency (rather than the
other system - used on boats). The water might be around 90 - 110
degrees (20 or so degrees above outdoor temp), and the fins might be
around 190 degrees. The difference in temperature between the water and
the hot fins would be rather large, so heat transfer would be rapid.
With the boat system described earlier, the cold water might be 60 - 70
degrees. The room temperature would only be about 10 - 20 degrees
hotter than this. So heat transfer wouldn't be as rapid.
The one advantage of the "boat system" is that the entire AC unit could
be placed outdoors. On the indoor side, there would be no tubing above
room temperature. Which eliminates the problem I have had with my
portable unit: heat leaking back into the room. As far as I'm
concerned, both systems are adequate; ease/difficulty in construction
will be the deciding factor.