Air coolers - any good or waste of money?

[jgkgolf]

My wife wants to buy this

AIR.htmto cool our toddlers room.It's a relatively small double room about 12 feet by ten feet.

Will it be any more effective than a fan?

[dmc]

Is some ways, yes. I'm assuming from the minimal description that this is an evaporative cooler - while they do work they have serious disadvantages...

The cool the air buy blowing it over a damp surface - this causes the water to evaporate which obviously has the side effect of raising the humidity of the air...this isn't great.

Personally, I don't like the heat but I'd prefer hot and dry over cooler and humid anyday.

Although the temp of the room may drop a bit the increase in humidity will not always make the room feel any more pleasant - and possibly worse.

I wouldn't buy one myself. YMMV

Darren

[Bob Mannix]

AIR.htm> to cool our toddlers room.It's a relatively small double room about 12

Overall probably not worth it (IMHO) but it does dehumidify. Toddlers can get hot and sweaty in weather as at present - if it helps him/her sleep cooler/drier/better, you might think it's worth it! But probably only effective for that with the window shut and the noise might keep him/her awake. You can't, in the end, put energy into a closed room and not make it hotter, even if you make it drier.

[John Rumm]

AIR.htm> to cool our toddlers room.It's a relatively small double room about 12

These coolers are best in hot dry climates where the extra humidification might be desired. In this country where hot and wet is the norm, they can actually make it harder to get cool.

[Bob Mannix]

AIR.htm>> to cool our toddlers room.It's a relatively small double room about 12

Ah, too late in the day - of course it makes the air wetter not drier, that's how it cools it. Forget everything I said, waste of money!

[Harry Bloomfield]

[e-mail] used his keyboard to write :

AIR.htm> to cool our toddlers room.It's a relatively small double room about 12

The way they operate is as follows...

You fill a tank with water, the water is drawn up onto a material which is in the air flow which causes the moisture to evaporate. The process of evaporation needs energy, the energy being obtained from the air - which is cooled as a result by 2 or 3 deg.

So far, so good - now the bad points... The moisture ends up in the air, increasing the humidity. We always notice hot days most, when it is humid because high humidity prevents us from disposing of body heat by sweating.

So in a closed room using one of these you swap temperature for higher humidity. You could get a quite similar cooling result by hanging wet towels up and using an ordinary fan to blow air across them.

[Rob]

AIR.htm> to cool our toddlers room.It's a relatively small double room about 12

A fan, maybe cieling fan, will be far more effective. Just put the cieling fan high enough or get one with a guard around it. That unit looks like a dehumidifier, which will use a lot of electricity. A cieling fan would be far better.

[Onetap]

They are excellent........

.......in Arizona or in Foreign Legion forts in the Sahara.

However, in the UK they're a complete pile of poo.

Simply cooling the air makes the Rh higher. You can get something like

80% Rh indoors by simple cooling (no dehum) and this is extraordinarily uncomfortable, clammy, close and muggy.

These things don't do simple cooling, though; they cool the air AND they add moisture. And Argos sell them. To people who can't read a psychrometric chart.

The legionnaires' disease should soon reduce the numbers of the psychrometrically illiterate.

[Dave Liquorice]

The only way to effectively cool a room, ie bring the actual temperature down, is to have some form of heat pump and dump the heat else where. An evaporative cooler doesn't does this indeed the energy it consumes gets dumped into the room as well so if anything it makes it hotter.

A large, slow, ceiling fan will be much more effective and quieter as the very gentle flow of air enables the bodies own cooling system to work properly. Rooms feel uncomfortable when the air isn't moving and your sweat isn't evaporating as it should to cool you.

A normal fan blasts small amounts of air around quickly, a ceiling fan makes the entire air in the room slowly circulate.

When I was back pack travelling through the Far East most rooms didn't have air con just a ceiling fan. That on low was enough to make the 90deg heat and 90% humidty perefectly acceptable turn it off and you "melted". Just remember to keep your fluids up, in this case the fluids of the toddler.

[The Medway Handyman]

Interesting. We have them in every room apart from kitchen & bathroom and they do work very well. Now I understand why.

Cool!

[david.cawkwell]

Useless. A complete waste of money. Doesn't give any benefit in even mildly warm weather. Get a proper air conditioner. You can air con a small room a unit for =A3300 off ebay. I fitted a double unit last year. One outdoor unit two indoor units for two rooms. =A3600 it's great cool in summer hot in winter.

[Onetap]

At the risk of sounding pedantic, they do cool the air.

The moisture absorbs the latent heat of evaporation that it needs to change from a liquid to a vapour from the air, so the air temperature does go down. The amount of latent energy involved in getting moisture into, or out of, the air is large and it can be a larger load than the sensible heat gains (sunshine, lights, computers, etc.). An evaporative cooler should produce 2 or 3 degC (at a guess, I've never used one) of cooling. Relative humidity goes up, which is the huge, unanticipated catch.

An arrangement I once saw advertised, for commercial air handling units, divided the supply air into multiple narrow ducts and the evaporative cooling pads were on the outside of these, with the extract air stream blowing over them. It should have worked in theory, but I never saw any in use so I'd assume there were other unanticipated catches involved (insignificant cooling, lime scale, corrosion, etc.).

[Dave Liquorice]

But only some of the air leaving the unit, the air cooling the motor will be hotter. you are pumping in several hundred watts of electrical energy most of which will end up as heat. Yes the latent heat of evaporation will takes some of it, until the water condenses else where...

As I said the only real way to cool a room is to have a heat pump and shift the heat from the room to somewhere else.

Yes that should have worked but there is an important difference between that and an in room evaporative cooler. The heat is being dumped outside via the extract air flow...

[Colin Stamp]

Not always. In fact, in the UK, it's rarely the case.

Specifically in the case of the OP (cooling a UK bedroom at night), no heat pump is needed to dump the heat out of the room. Just ventilating with outside air will give all the temperature drop you need on all but the very hottest of UK nights.

I'd start by opening a window. If there isn't enough wind to make that work, come up with some cunning arrangement to make a fan pull in outside air.

If you go down the fan route, you could even put a thermostat on it...

Cheers,

Colin.

[Onetap]

They do cool the air.

There is one here, for example;

electrical power input is 690 W.

The rate of evaporation is 53 litres in 10 hours =3D 0.001472 kg/s.

The latent heat of vaporization at (let's say) 21 degC is 2451 kJ/kg.

The cooling effect due to evaporation is (0.001472 x 2451) kJ/s =3D 3.61 kW.

The net cooling effect is (3610 =96 690) W =3D 2918 W approximately.

Got that?

They cool the air, as anyone could show with a thermometer, so you couldn't demand your money back because it doesn't cool. Not many people would have a hygrometer handy.

We are agreed that they're a waste of money.

[dennis]

I would like to see it evaporate anything when the Rh is 100%, which it is for a fair portion of the time.

[Andrew Gabriel]

Yes.

Trouble is that humans really don't care much about the actual temperature, but do care about the wet bulb temperature, as we're actually all damp when we're too hot. Cooling by raising the humidity doesn't reduce the wet bulb temperature, so although a (dry bulb) thermometer will show a temperature reduction, you won't feel it, and you won't be able to cool yourself any better (often quite the opposite).

Evaporative and swamp coolers work really well in hot dry climates. They don't work in the UK climate.

[Dave Liquorice]

Not indoors... In the winter with the CH on the indoor RH is around 30%. In summer with the CH off it is aroond 50%. But then we don't have an evoporative air "cooler" chucking out 1.1 gallons of water an hour...

We have a 25' long 2' thick and 20' high lump of stone through the middle of the house, keeps the place cool in summer and warm in winter.

[Pete C]

I think they're OK for spot cooling in a limited range where there's a good throughflow of air.

Would be best for cooling face and body of one person if up on a nearby table/shelf.

cheers, Pete.

[whisky-dave]

Well I'm not sure, but I have brought one of these :-

L35AK

And I certainly felt cooler while it was blowing air using just the water. I'd assume the air would be further cooled by the addition of the ice packs.

In fact my one was in use in the store where the staff were using it behind the till point so I guessed it must work, and I got a used discount too . So ended up paying £35, so I considered it a worth while buy.

I'm not sure what the Maplin one is but it does seem to work. I assume that blowing warm air over cold water that the this warms the water and cools the air, which is what I want.

I'd like to give it a good test on a hot day and measure humidity and temp.