Here in Southwest New Mexico (USA), evaporative coolers are common. The coolers for homeowners are single stage. They trickle water over a fiber pad and blow air over the pad into the house. Unevaporated water trickles back into a reservoir in the bottom of the cooler. A float valve admits fresh water to replace the evaporated water.

I've read that there is such a thing as as a "two stage" evaporative cooler. The first stage uses evaporative cooling to cool the surface of a heat exchanger. Air is pulled though the exchanger and cooled without gaining humidity. Then this air enters an evaporative cooler that works like the single stage cooler previously described.

I think two-stage coolers would be large bulky machines. So I was wondering if a makeshift two stage cooler could be fabricated as follows: Run the water in the reservoir of the single stage cooler through a car radiator before it trickles on the pad. Have the incoming air pass through the radiator and be cooled.

Admittedly this sounds suspiciously like one of those perpetual motion schemes where you convert energy back and forth between systems and claim to have a net gain. The water in the reservoir of the single stage cooler would be warmed by the trip through the radiator. Would evaporation on the pad be "better" since the water was warmer? I think the radiator would remain below the ambient temperature of the air since fresh water is admitted. This isn't a closed system. The analysis seems complicated. It might be simpler just to try it.

Opinions?

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Radiators allow heat from the working fluid to escape; not heat it up.

Or are you talking about mixing water with warmed water running through a car radiator???

I think what you're thinking is closer to the Two-Stage Evaporative Cooling idea already outlined here:
http://en.wikipedia.org/wiki/Swamp_cooler

You could do like the Egyptians, and make those seven feet high water jars of terra cotta. Unglazed but fired pottery loses water through evaporation from pores in it's sides (and by gravity through it's bottom)...albeit slowly. the evaporative cooling in a windy shady area outside a tent, or awning of a small hut, keeps drinking water a lot cooler than ambient...10-20 degrees is my OTOMH recollection, but I'd like to see a personal demo. pete

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Radiators allow heat exchange.

If the water going into the radiator is colder than the air blowing through the radiator, then the water will be warmed.

Nothing about the radiator makes the heat transfer "one-way".

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I see what you're getting at, and it's essentially the same thing as some intercooler designs for turbochargers.

To restate your proposal (just to be certain I understand it), you have two airflows: Outside-Outside (OO), and Outside-Inside (OI).

OO evaporates water, and becomes cool and moisture-laden. OI is cooled by a heat exchanger from OO, and as a result, OO is dumped outside at near ambient temps while OI is dumped inside at cooler (by 20 to 30 deg) temps.

What you're proposing is pre-cooling the water using the OO airstream to obtain cooler water going into the mix than warmer water. While cooler water evaporates more slowly than warmer water, it takes more heat to evaporate it, but would also require a larger surface area to achieve saturation with the same flow rate.

On the other hand, the water flow would be counter-flowed to the OO flow. Thus, the tail end of the OO flow, the one being used to cool the OI flow, would wind up being warmer...

I think it's a zero-sum game, tashirosgt, and might even be less efficient due to the greater surface area required for evaporation to saturation.

On the other hand, if you had two parallel OO flows, one to pre-cool the water, and a second to coo the OI stream, you might have something...

There are multi-stage designs for evaporative coolers, but with multiple stages comes increased costs with diminishing returns, as there is a limiting factor for evaporative coolers, namely, not the temperature of the ambient air, but it's relative humidity (a combination of it's temperature and absolute humdity).

On the other hand, heat-pumps can be made significantly more efficient by using swamp coolers to cool the air used to cool the evaporative (freon) coils of the heat pump. The problem is that this does use water, and water in most dry climates is in fairly short supply.

If water is no factor, and price is no object, a multi-stage swamp cooler feeding cool air to the coils of a heat pump is the most efficient approach so far as the electrical cost of air-conditioning. But again, the cost of water may be high.

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If I set the budget, we'd have Ares and more. Unfortunately, I don't set the budget, and Ares is just too expensive and too far out for us to accomplish our goals within the budget we were given.

If we halt the ISS, all versions of Ares, and transport Orion and Altair aboard DIRECTv3's Jupiter family of Shuttle-Derived Launch Vehicles, we just might make it back to the Moon by 2020.

As I understand your teminology (O-O, O-I), your first description agrees with my description of a two stage evaporative cooler. I think this is a well know technology but the two stages make the units too bulky for home use.

The only airflow propelled by a blower in my idea is the outside-to-inside (O-I) air.

In theory ( in one stage-cooling) the water supply to the cooler reservoir can be rather slow since it only replaces evaporated water. However there are reasons to run it "too fast" and overflow water from the reservoir. (I and many other home owners do this and use the overflow for slow irrigation.) For one thing, the water in the area is very "hard" and a slow flushing of the reservoir prevents mineral scale from building up. It also keeps the reservoir from becoming stagnant..

My idea can be realized by rerouting either the flow of water from the reservoir to the pads or the flow of water from the man line into the reservoir. I say to run this water through a radiator. Run the O-I air flow over the radiator before it hits the evaporating pad.

The flow of water from reservoir to pads is rather rapid when the cooler is running since excess water runs off the pads. The flow from the main line into the reservoir is slower.

I agree that my idea sounds like a zero-sum procedure.. However, I see no way to dismiss it with straightforward analysis. Take the simplest case where the inflow to the reservoir only replaces the evaporated water and the water through the radiator comes from the flow from the reservoir to the cooling pad. What reasoning can be applied to analyze that?

( I mention a "car radiator" since that is the part that is handy to use. I'm not saying that there is running automobile and that water is going through it's radiator to be warmed up!)

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It works quite well. We used to use earthernware pots to keep water cool when we were camping.

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Although I am not trained in the use of evaporative cooling techniques-- I wonder ... if the use of dessicant agents could possibly be re-cycled in lieu of terra cotta. Since terra cotta seems much too bulky to be effective for a large scale cooling (?)--

This is obviously some speculation on my part.............

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The primary reason they went to two-stage cooling was to reduce the humidity of the interior air from 70-80% (mold-supporting) down to 40-50% (comfortable).

Original bota bags are leather bags or bladders made to hold water or wine. They had no plastic liners back then, and evaporative cooling was a part of their effect.

The other week, while at REI, I saw a modern evaporative cooling bladder, but I'm not sure who makes it. Could have just been a bottle holder that you wet and let dry, cooling the bottle.

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If I set the budget, we'd have Ares and more. Unfortunately, I don't set the budget, and Ares is just too expensive and too far out for us to accomplish our goals within the budget we were given.

If we halt the ISS, all versions of Ares, and transport Orion and Altair aboard DIRECTv3's Jupiter family of Shuttle-Derived Launch Vehicles, we just might make it back to the Moon by 2020.

The trouble is that they didn't go to two-stage cooling - at least not in the evaporative coolers available to homeowners in the Southwest (USA). I can't complain that single stage evaporative coolers don't work. I prefer warm temperatures and my cooler keeps the house comfortable (to me) most of the year. In the rare case of a few days of rainy weather and high outdoor humidity, the cooler doesn't work well. It also doesn't work well if the temperature climbs up near 100 F for extended periods since the max temperature drop it can achieve is limited. Fortunately, I don't live in Death Valley!

...and besides, I have some spare car radiators sitting in the garage.

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When I was a kid (only a couple years after rest stops were invented and were frowned upon as a waste of taxpayer money ), it was common to see square canvas bags hung on the front of cars driving down the road--for cool drinking water. O yeah, did I mention the cars didn't have air conditioning, nor seat belts neither?

I've seen large water bags made out of a heavy canvas-like material used for drinking water. They are hung from a tree in the shade and are porous (but not enough to lose much water) - the evaporation keeps the drinking water pretty cool.

A post idea whose time has come

Well, there you go!

Now I'd imagine if you had a nice cold creek running through your backyard, you could filter it and pump that water through your radiators, modified to sit in the house, with fans blowing through them, and substantially lower your electric bills, particularly if you used PV's to power the pumps and the fans.

Alternatively, you could set up a dual-radiator set, one inside, one outside, with...

Nah, that gets too complicated. A lot cheaper just to hydrade the air and pump it inside, if you don't mind the humidity.

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If I set the budget, we'd have Ares and more. Unfortunately, I don't set the budget, and Ares is just too expensive and too far out for us to accomplish our goals within the budget we were given.

If we halt the ISS, all versions of Ares, and transport Orion and Altair aboard DIRECTv3's Jupiter family of Shuttle-Derived Launch Vehicles, we just might make it back to the Moon by 2020.