Quote:
Originally Posted by Occasionally6
If you only compress air you don't need an evaporator, just an orifice through which the air can expand. That's a bit different to a conventional car (or building) A/C system which uses the change of state in a refrigerant to absorb and reject heat energy, and is a closed system.
A refrigerant based system can produce a cooling work (energy flow) that is a multiple (maybe 3-4x) of the compressor work. The air based system is only at 1:1 (ideally) but would be simpler to implement.
You do need the intercooler to bring the compressed air back to (near) ambient temperature and so to allow cooling below ambient when the air is expanded. If you search for "air standard refrigeration" you should find some more info.
I've mentioned it in another thread but if you've ever watched an F1 qualifying session you will have seen the drivers being cooled in their cars with air ejectors. The compressed air is released through a nozzle in a duct, which both allows the expansion cooling and entrains (extra) ambient air to provide the air flow.
To play around with the idea, a portable tank for holding compressed air is pretty inexpensive, as is a very basic 12V air pump (not wasted if it doesn't work as you can still use it to maintain tire pressures).
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If it is simpler, with less items to make it work, then I would imagine it *could* be cheaper for the auto companies to use an air-to-air system.
It makes sense to keep the intercooler/radiator as the heat picked up would still need to be released (or radiated) somewhere else, but with less obstacles within the system (e.g. evaporator).
So the big question then is if somebody was to get into otherwise identical cars, save for the a/c system, would they notice a difference? In other words, can an occupant be comfortable in an air-to-air system without noticing any negative effects as compared to a refrigerant system?
Also important is the efficiency of the system. Assuming we use a turbo to compress the air, would it be any more efficient than a standard refrigerant style a/c? That may be a hypothesis that needs to be determined through trial and error experimentation. If it doesn't improve engine efficiency (in any aspect: FE, power, etc.), then what would be the point?
I wonder if there is something other than air that the system could use that would be more efficient/have better cooling capacity. What about CO2? Or to expand (no pun intended) on that thought, what about exhaust gases (CO2, NOx, etc.)? What about pure oxygen?
I have not heard of the F1 style coolers, very interesting concept though. I would imagine it is similar to the compressed air in electronics dust cleaners, except the cold is transmitted out rather than at the nozzle/can itself. The idea does remind me of the water spray bottles with a fan attached that you see at amusement parks. I wonder if the concept can be used effectively in a duct and vent system that a car utilizes?
The experiment concept is pretty interesting and I already have a 12V tire air compressor for another project that didn't pan out, but as you know this experiment is going to go way down on the totem pole!
