Brackish Water for Small-Scale Evaporative Cooling

1. Evaporative cooling works by the water absorbing heat from the air as it evaporates, so passing it through the wool, which will increase contact between the water and air will probably be more effective.
2. Brackish water is just fine as the salts will largely be left behind. Just don't leave anything that can corrode readily in the direct path of the air as microscopic particles of salt may be carried along by the wind.
3. Anything will do as long as it has high porosity so that the air can flow through it easily.

In addition to the above:

<...Should I take into consideration any effects that the salts might have on the evaporative cooling occuring?...>

1. The salts in the water will become more concentrated as evaporation takes place, and calcium and magnesium carbonates and sulphates, among other things that may be present, will precipitate out on convenient surfaces as the concentration rises. So some form of blow-down (changing the water) should take place at intervals. In the absence of any instrumentation, the blow-down point will need to be determined by experiment. Periodic cleaning of surfaces may become necessary.
2. There is a need to prevent excessive biological activity in the water, so that the air that is cooled does not transmit bugs, nor smells for that matter, around the room.

In an industrial cooling tower, these things are catered for by chemical dosing.

Evaporative cooling is a potentially hazardous activity that needs to be well-managed to become safe. The bacterium legionella pneumophila is the main hazard in commercial and industrial facilities, which is easily dispersed onto people and facilities in the surrounding area if present, causing illness if not guarded against in some way.

Ehh, who knew "wood wool" and excelsior were the same thing?

The first illustration here shows a typical.

Many of the problems involved are solved in this design by using a constantly refreshed supply of water, drawing through the wood wool so the salts that evaporate out stay on the wool.

Annually one changes or washes the pads depending on whether one used wood wool or poly fibers.

The most important question is, what kind of vacuum pump is causing this discharge. If it is a water ring vacuum pump you may as well forget about further cooling by evaporation, because the air is saturated. But if the dew point and temperature of the exhaust are lower than the ambient room temperature, some cooling is possible. Good luck with the bacteria, slime and mould on your wood wool. Keep it clean.

Interesting. I've never heard it called wood wool before. An evaporative cooler works by evaporation. The cooling pads (wood wool) are soaked with water from above and gravity ensures that the entire pad gets wet. Air flowing through the pads causes evaporation of the water and consequently cooling of the air (water absorbs heat from the air in order to evaporate).

Anyway, for an evaporative cooler you need a source of warm dry air. Humid air will not work. This air is cooled through the evaporation of water as the air is drawn through a filter of some sort, wood wool in your case, to increase the efficiency of the evaporation process (more contact between the air and water as stated by someone else already). If the output of your vacuum pump is very dry it should work OK. It is a rather unusual method for producing the air which is pumped into your home. A vacuum pump is energy-wise not an efficient method for this. If you are already using this continuously for some other home use purpose - fair enough. Also, a lot of (especially older) vacuum pumps have the nasty habit of misting the lubricative oils into the exhaust and require a filter to remove it so it is not expelled into the air. The other thing is that vacuum pumps are typically noisy, especially compared to the efficient high volume fans used in typical evaporative coolers.

As far as the water - the salts and lime will quickly begin to coat the wood wool, dramatically reducing the cooling capacity of your system and eventually clogging it up. One usually goes to great lengths to prevent salt and lime precipitation on the cooling pads, using household water and an inline filter as well as electrical means to plate the salts out and even chemical retardants. The cleaning process also involves using chemicals to remove the salt deposits from the pads. The other thing is, the source of the water. Does it contain bacteria, mold, algae, mosquito larvae etc? Does it smell? If it smells, that is how your house will smell. The cost of setting up the equipment to properly clean and filter the water for safe and reasonably efficient use in your cooler will probably cost you far more than just using your tap water. It is obvious you are making a noble effort to use resources readily available to you, but this may not be the wisest approach for the air you pump into your home for your family to breathe.

You also asked about screens. This depends on the porosity of your wood wool. If there are potential paths for small insects such as young mosquitos to crawl through, you will want to cover the outside with a fine netting to prevent entrance to such pests - otherwise you shouldn't have to worry about it.

Read the Wikipedia link that was listed in one of the responses. Good luck in your endeavors.

For closed, occupied areas, this function would be better-served by installing a geothermal pump directly to your heat pumps' condenser. Larger greenhouses use evaporative cooling (and I, too, once thought it advantageous-- till I looked into it), look what they have to deal with. Most that are in humid regions (I'm in ATL) must supplement it with geothermal (anyway).

Good Luck,

Craig Luce