After quite a bit of experimentation I came up with an efficient design for the DIY cooling system. The design involves a U-shaped heat exchanger, through which a fan pushes air. The heat exchanger is immersed in an ice-water mixture which allows heat exchange to take place. As a result the air exits the heat exchanger significantly cooler than its temperature going in.
For pictures and explanation of this design have a look at the link below.
The key to this design is maintaining a balance between the size of "gap" and flow length of the heat exchanger. The gap controls the rate of heat transfer. The narrower the gap the greater the rate of heat transfer. And the longer the flow length the greater the total heat transfer that takes place. The factor which must be accounted for is the resistance to air flow which increases when the gap decreases, and increases when the flow length increases.
Fortunately, I am able to get as much as a 10 degree Celsius temperature drop with my choice of dimensions, while still maintaining an acceptable level of air speed through the heat exchanger. The fan I used is a store-bought fan.
Ice is the most effective means to create the cooling medium. But you can also use tap water, if it's cold enough, say 10-15 degrees Celsius.
However, you can also make ice in your freezer provided it is an efficient model. As it turns out, it would still cost quite a bit less to operate the homemade a/c (plus make ice) than to operate a store-bought a/c. The difference, of course, is that the homemade a/c is best suited for local cooling only, i.e. you just want to keep yourself cool, such as at night when you're sleeping, which is likely all you really care about. Just place it beside you and you're taken care of for a few hours. And it's better than having a stand-alone fan running.
Copyright © 2008 Vittorio Norman
Vittorio Norman explains how to make a homemade air conditioner, on his website at http://assortedtips.blogspot.com/2008/05/homemade-air-conditioner-version-3.html
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