Half a croissant, on a plate, with a sign in front of it saying '50c'
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Passive Aircon

Porous ceramic passive cooling
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Could cars have a passive air con (to save fuel use in normal a/c use) which kicks in at high speed and takes over from the normal a/c unit?

At high speed, warm filtered outside air is piped through a highly porous, wet ceramic block which sits in a reservoir of water. The air does not contact the ceramic block, so does not get dampened.

The latent heat evaporates water from the block, cooling the piped air which is then passed into the passenger compartment. The evaporated water can then be condensed (not sure how yet) and returned to the reservoir, which can be topped up when needed.

Or am I in cloud cuckoo land as usual?

cloudcuckoo, Jul 21 2004

Evaporative cooling for cars http://www.classicaire.com/RamAir.htm
Been around a while in a slightly different form [half, Oct 04 2004]


       Well, it wouldn't work in humid climates because evaporation would be too slow.   

       If you intend to keep the air that you're cooling separated from the damp air around the ceramic block, then you've got to have a lot of piping which needs good thermal contact, sufficient air flow, etc. Also, it requires two blowers - one for the passenger air and one to encourage evaporation.   

       I wouldn't bother trying to condense the evaporate.
Genki, Jul 23 2004

       I'm unsure about something too. How does the air go through the porous ceramic block without being humidified? Are there air passages which don't come in to contact with the water but are somehow cooled by the evaporation? Ceramic seems like it'd make a pretty lousy heat exchanger.   

       I'm visualizing a fairly fine porous structure in your ceramic. Minerals would eventually clog this structure unless maybe distilled water was used. Evaporative cooler pads build up minerals very quickly. The costlier ones (e.g. Master Cool cellulose pads) are sometimes cleaned with acid to dissolve the minerals. Not sure how that would affect the ceramic material though.   

       Ever seen the original evaporative cooling method for cars? It's not exactly new-fangled high-tech ceramic stuff. Works pretty well in the desert. (link)
half, Jul 23 2004

       Would this really save fuel? The device shown in the link seems like it would produce a lot of drag at highway speeds. The proposed idea still has a conventional airconditioning system-two systems means increased weight. Increased weight means more fuel...
gabe, Jul 24 2004


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