Air Conditioning

We had a digital thermostat in our cabin. Guests were always getting it into strange states. I ripped it out and put in a dumb analog unit. I also disappeared the HEAT/OFF/AC switch and left it permanently in HEAT mode, so's not to freeze the plumbing. Analog things like this are hackable.

VF drives can be an option but one has to make sure the compressor is happy with that and also gets enough of a jolt to start up.

But there is something else that could make them a ton more efficient in most areas, and definitely during a heat wave: Evaporative pre-cooling on the outside. But don't expect A/C manufacturers to understand that, progress takes a loooong time in that market. Sometimes it just doesn't happen at all.

Speaking of which, I've also wondered what would happen if you used a turbine instead of an expansion valve / capillary. Thermodynamics says it has to be the same: hot, high pressure fluid in; cold, low pressure fluid out; it doesn't matter if it expands through friction (heat work) or performing mechanical work.

Disadvantages: 1. to keep the pressure balanced, you can't use a synchronous pump-unpump. One or the other needs to be controlled to regulate high or low side pressure; 2. more parts means potentially lower reliability; 3. regulating pressure (which requires yet more parts) changes the temperature or refrigerant characteristics of the system (for better or worse?).

That, and the evaporative cooling Joerg mentioned, ought to do wonders...

Tim

-- Deep Friar: a very philosophical monk. Website:

Couldn't a simple evaporative system even be retrofitted onto a plain old window air conditioner? Like a water fountain pump forcing water over the heat expeller (fins) side of the compressor and an evap tray right below the outside end of the window unit?

I was thinking about just spritzing down the heat expeller fins with a garden hose, just to see if it starts to chill better inside.

A very fine jet misting the expeller side and collected and routed to the garden or spread over the lawn might be worth it if it boosts the BTU delta result.

Would an evap booster kit sell?

A lot of window units use the condensation from the evaporator to cool the condenser - the drain path takes the water to where the condenser fan can dip in and splash it onto the condenser. Works ok because the condensed water is pretty clean, just whatever dust got past the filter. With an outside condensing unit like central ac you would have to use tap water and face massive mineral buildup and corrosion. I remember reading about people trying this many years ago and the answer seemed to be it was cheaper not to do it than it was to keep replacing the condenser coil, but I can't give you any cites for that memory. Current house-sized air handlers are using vfd's to save energy, but I've only heard about 2 speed compressors, not continuously variable (again, in house sized units).

Couldn't a simple evaporative system even be retrofitted onto a plain old window air conditioner? Like a water fountain pump forcing water over the heat expeller (fins) side of the compressor and an evap tray right below the outside end of the window unit?

I was thinking about just spritzing down the heat expeller fins with a garden hose, just to see if it starts to chill better inside.

A very fine jet misting the expeller side and collected and routed to the garden or spread over the lawn might be worth it if it boosts the BTU delta result.

Would an evap booster kit sell?

No you have

-and-

A whole product line here

The other problem: evaporative plants were noticed to grow Legionella. They use these on big buildings, not the kind of thing for household use anyway.

When I leave my tapwater out for a long time (i.e., weeks, not days), it starts growing things (gray mold, algae). Despite being Milwaukee's well-chlorinated Best. :-/

Tim

-- Deep Friar: a very philosophical monk. Website:

I understand they make manufacture a type of slightly yellowish water there that has a small amount of alcohol content, which might do to keep such organisms away.

Best regards, Spehro Pefhany

puleeeezzzz....

It's not that dramatic:

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I recall a company, Rovac, doing exactly that back in the '70's for automotive A/C. They used a pair of coupled rotary vane pumps for both compression and expansion of plain old air. They made plenty of claims about it, includig it being patented but apparently it was rejected by the automakers. Art

Sure doesn't do much for the humans that drink it :-)

Tim

I had forgotten about Legionella.

Is alcohol the main Legionaire's disease preventative solution for those huge evap systems?

Wouldn't the alcohol evap before the water?

Wouldn't other disinfectants work better?

Would the disinfectant effect of copper trays be enough?

It lookes to me like a refence to "Schlitz".

The beer that make Milwaukee famous

I have met people who said they saved about 30% electricity with a pre-cooler. That is substantial.

If you completely switch it's much more dramatic. We still have our A/C, it just doesn't get used anymore. Got to remind myself to turn it only once though so the bearings won't gunk up. Anyhow, when keeping the cooling to moderate temps inside (mostly out thermostat was at 83-86F if the A/C was on) the regular central A/C used about $250 worth of electricity in mid-summer. Now we have an evaporative cooler, temps rarely get above 80F inside because of it, and the total utility costs caused by it (electricity plus water) are around $50.

Some (most?) liquid air/oxygen plants do it that way. They use the expansion engines to drive generators supplying plant loads, The incoming supply only drives the (humongous, 1000+HP ) compressor.

The plant I saw (1960s) used reciprocating expansion engines. Big, clacking, poppet valves covered in ice. How they lubricated them, I dunno. They claimed to make several tons of liquid oxygen every week, most of which was piped directly into a steel mill.

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I know people who have said they saved money with "Watt Savers", water pipe magnets, and such, too. Some even claim to save money with PV cells and electric cars, too. ;-)

OTOH, if it causes other problems (from Legionella to premature equipment failure), it's likely not worth it.

If it worked here, I might try it. I just found out one of our evaporator coils in the new house is bad. $1500. The entire system really needs to be replaced but I'll try to get it to go another five years (it's only five years old).

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What kind of humidity levels are we talking about here? RH in excess of 70%= at temps in excess of 70o and water content of wood products 17% or more c= onverge to produce mold growth, and it will grow. A 1998 experiment by PG&E= specifically evaluating mist pre-cooling concluded a SEER 10 becomes an 11= or something, a little improvement but not earth-shattering.

That sounds like the 'Air Products & 'A-K Steel' setup in Middeletown, Ohio.