Evaporate air cooler

[g-lock_dk]

Hey eevblog forum

I hope you can help me out with this

When it is hot outside I hear lots of people talking about all these evaporate air coolers, are my intuition at fault here or are they really up to the job?

link to a ramdom cooler https://www.amazon.com/HOMFUL-Personal-Conditioner-Evaporative-Humidifier/dp/B07VPFGMC7

[wraper]

This is not an air cooler but crappy air humidifier.

[g-lock_dk]

hey wraper

ty for a quick reply I can all most hear it in your answer "don't buy that shit" but if you should put a little math and science into your answer what would you hit it with??

[HackedFridgeMagnet]

they work really well when there is low moisture in the air. eg. Central Australia.

Probably not the case for Denmark.

[KMoffett]

Evaporative coolers actually cool the air. But only work in very low humidity environments. It is the same principle as cooling in a refrigerator, but water evaporation in dry air.

[wraper]

Evaporative coolers actually cool the air. But only work in very low humidity environments. It is the same principle as cooling in a refrigerator, but water evaporation in dry air.

You can use a real non sneaky air humidifier in it will do the same but better.

[David Hess]

I have always heard them called "swamp coolers".  They are nice and even desirable where humidity is low like the high desert but almost useless anywhere else.

[John B]

Every time I have been inside a house with central evaporative cooling, they have made the air noticeably damp. Maybe there's more advanced models with some form of heat exchanger that keeps the cooled humidified air separate from the internal house air. I would be concerned about the negative health effects of the increased humidity.

[jogri]

Pros:
-cheap
-has a relatively good efficiency (cooling power vs consumed electrical energy) as they only have to power a fan

Con:
-will produce 100%air humidity when left running

If your question is if they are worth it the answer depends entirely on your definition of "up to the job":
Do you want a cheap, energy efficient air cooler and don't care about anything else? Go for it.
Do you care about getting a crapton of mold inside your house? Then maybe consider another solution (or direct the air through a drying system to get rid of the humidity)

Those devices cool the air by letting water evaporate: It takes a LOT of energy for water to change from its liquid state into a gas-> that energy (in the form of heat) is taken from the hot air that passes through-> air gets cold, water evaporates->air also gets humid. The higher the humidity of the inrushing air is the lower the amount of cooling gets: You can only get 100% relative humidity, if the hot air already has a lot of water vapour not as much water can evaporate ->less energy needed ->air doesn't get cooled as much.

Rather neat concept, but those devices have a massive flaw when used indoors: If your room gets cooler during the night the water condenses as colder air can't hold as much water ->perfect conditions for mold etc.

If you want to try out evaporative cooling just soak a towel in water and place it in front of a fan (or hang it over a box fan).

[Siwastaja]

Selling those things in countries where the problem isn't the temperature but the humidity, is borderline scam. And outside the Sahara desert, this is almost always the case.

They do not work here, and I bet they don't work in Denmark.

Say, if you can drop 35degC 10% RH to 30degC 30% RH, you'll make it more comfortable, but the problem is the opposite in many climates.

Here you tend to need cooling for maybe 2-3 weeks per year, and then the weather is like +28 degC and RH=70%. It feels like +35 degC because of the high humidity. Lowering the RH is #1 priority, reducing the temperature a bit is an extra benefit. Those humidifiers do the opposite, they increase the RH even further. The fact that the temperature could lower by a degree or two does not compensate for the decreased comfort.

Those cheap and crappy, but real compressor based things that have a flexible tube you use to blow hot air outside, work surprisingly well in the Nordic climate I think; I'm very happy at least. They are quite noisy and suck in hot outside air, but compared to the humidifier scams, these still do the real thing, namely dry the air and, at the same time, reduce the temperature easily by a few degrees. For really hot climates, proper air conditioner units are needed, but those cheapies work well enough here. Just be careful not to mix them up with nicely branded "water evaporation" scams.

[Connecteur]

When I lived in the southwest, mine worked great.  It used a fraction of the power of an air conditioner, and it blew a steady stream of nice, cool air.  But I knew it wouldn't work well on those few days when the air was humid, so I never had a problem.  I know a lot of people who hate them because they expect it to work all the time, even when the humidity is high. It's a very good trade-off.

They're also very cheap compared to air conditioners, and that's probably why so many dealers are against them, as well as dealing with complaints from customers who don't understand that the cooling depends on atmospheric humidity.

[Kleinstein]

It can work well in really dry air. The cheap way is just to produce some fine water mist inside.
When really dry even 35 C e.g. at < 10% RH are not that uncomfortable.
In such climate it is usually also quite cool at night - so ventilation at night is also very efficient.
In really dry air a little more humidity (e.g. 25% instead of 5%) can be a plus too. One would not like the humidity to go much above 50%.

I would not expect it to be very effective in Denmark. Chances are the evaporative cooling only makes sense below some 25% RH.  Even if it still cools down the temperature, high humidity can be worse than just warm. 

[Ground_Loop]

Evaporative coolers actually cool the air. But only work in very low humidity environments. It is the same principle as cooling in a refrigerator, but water evaporation in dry air.

I had several 'swamp coolers' in my warehouse in Las Vegas.  Typical summer humidity is around 5%.  These work really well, but as said before, only in low humidity conditions.

[Domagoj T]

A simple way to see if it would be any good for you at any point is to check the local dew point (if you're having trouble finding it, it's standard data for weather data in aviation so check you local airport weather service).
These things can only lower the temperature down to dew point and at that point relative humidity is 100%, which is not really comfortable and a good condition for mould growth, which I presume you don't want in your house.

[Labrat101]

They only work well if the ambient humidity is below 30%rh ..
They are good if u live in a desert.  Of dry area.
The original name for these cooler was
Desert Cool and came from the middle east.
Cheap to run .
They make the house damp . The mosquito's
Love them .. 
Get a heat pump AC.

[cliffyk]

Every 10 years or so a new springtime cycle of these in, various implementations, show up at "outdoor" flea markets and other similar venues--here, in June through October, all they do is make a bad situation worse. But it seems to take 2 or 3 months before the management at these places realise they got duped, turn them off and leave them to rot 'til the next cycle...

[CatalinaWOW]

As stated over and over again they work in appropriate climates.  And are far cheaper to buy and operate than air conditioning in those appropriate climates.  The mosquito problem is real, but can be controlled with BT and screens.

But there are additional drawbacks not mentioned previously.

1.  Most climates where these work have cool seasons where they are not needed, but which also have low humidity.  This means that wood and other materials absorb moisture and swell during the times when the cooler is operating, and then dry out and shrink in the drier seasons.  Leads to poor fits, warping, cracking and other damage.

2.  Many places where these work have limited water supplies, and that water is often quite hard (high in dissolved minerals).  So it may be unwise to use the water for cooling, and if you do use it, rapid buildup of mineral crusts everywhere in the system occurs.  The regular maintenance to control this (and the corrosion that occurs in highly humid, mineralized environments) is a nuisance and eats into the savings. 

3.  At least some of the climates where these work also have a hot humid season.  You either have to decide to suffer through that or add refrigeration air conditioning.  The much lower operating costs during the hot dry season can still make it pan out, but the de-humidification from refrigeration compounds problem 1.

[cliffyk]

As stated over and over again they work in appropriate climates.  And are far cheaper to buy and operate than air conditioning in those appropriate climates.  The mosquito problem is real, but can be controlled with BT and screens.

But there are additional drawbacks not mentioned previously.

1.  Most climates where these work have cool seasons where they are not needed, but which also have low humidity.  This means that wood and other materials absorb moisture and swell during the times when the cooler is operating, and then dry out and shrink in the drier seasons.  Leads to poor fits, warping, cracking and other damage.

2.  Many places where these work have limited water supplies, and that water is often quite hard (high in dissolved minerals).  So it may be unwise to use the water for cooling, and if you do use it, rapid buildup of mineral crusts everywhere in the system occurs.  The regular maintenance to control this (and the corrosion that occurs in highly humid, mineralized environments) is a nuisance and eats into the savings. 

3.  At least some of the climates where these work also have a hot humid season.  You either have to decide to suffer through that or add refrigeration air conditioning.  The much lower operating costs during the hot dry season can still make it pan out, but the de-humidification from refrigeration compounds problem 1.

Good points, all...

Years ago a friend in Lincoln, NB mounted a large truck radiator in his forced hot air heating systems plenum, and then pumped 55-60° F well water through it; the water was then used to irrigate corn (which as anyone who has been to Nebraska knows is everywhere--kinda' like oranges here). This worked quite well even with outdoor ambient temps of 100°+...

[coppercone2]

the small ones that run on ice cubes are great for watching a movie in a hot environment if you set them on a coffee table etc

The one you linked is good if you throw a cup of ice in the tank and use it for a few hours. It makes things pleasant. Obviously I recommend sitting in your under ware without a shirt.

[Raj]

Beware...These things are high maintenance...if you run em through the night, all of the water you fill in it gets evaporated and it leaves salts behind. If you don't clean those, and if the fan is fast enough to throw some of the water your way, where ever those droplets land, you'll get salt stains. I own one similar to this-https://www.google.com/search?q=symphony+cooler&newwindow=1&rlz=1C1CHBF_enIN884IN884&sxsrf=ALeKk03yJ4qbPgY8V3IcPPqQufs8eLa3Ag:1593406313683&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjV8LyKnabqAhVSgUsFHQNqBfcQ_AUoAnoECA8QBA&biw=900&bih=1297#imgrc=HO_NnCm_Z5meVM

[Bassman59]

As stated over and over again they work in appropriate climates.  And are far cheaper to buy and operate than air conditioning in those appropriate climates.  The mosquito problem is real, but can be controlled with BT and screens.

But there are additional drawbacks not mentioned previously.

1.  Most climates where these work have cool seasons where they are not needed, but which also have low humidity.  This means that wood and other materials absorb moisture and swell during the times when the cooler is operating, and then dry out and shrink in the drier seasons.  Leads to poor fits, warping, cracking and other damage.

2.  Many places where these work have limited water supplies, and that water is often quite hard (high in dissolved minerals).  So it may be unwise to use the water for cooling, and if you do use it, rapid buildup of mineral crusts everywhere in the system occurs.  The regular maintenance to control this (and the corrosion that occurs in highly humid, mineralized environments) is a nuisance and eats into the savings. 

3.  At least some of the climates where these work also have a hot humid season.  You either have to decide to suffer through that or add refrigeration air conditioning.  The much lower operating costs during the hot dry season can still make it pan out, but the de-humidification from refrigeration compounds problem 1.

My house here in Sunny Tucson has both swamp cooler and A/C. Both units are on the roof and feed a common duct. Barometric dampers are installed in the duct so the output of one unit doesn't go into the other.

And we love swamp coolers here! Between April and June when it's dry, the coolers work well and are much cheaper to run than A/C even considering the water use. Once monsoon starts, typically July, coolers are miserable so we switch on the A/C. And in the fall we switch back to the cooler. This year has been weird, we've had an "early" monsoon of sorts, so we switch to A/C earlier than usual.

Everybody complains about maintaining swamp coolers, but the devices are so simple and parts are so cheap that we just do it. It's our springtime ritual.

Many people do retrofit install A/C, so you'll see houses with A/C units on the roof and crazy ductwork to bring the cool air into the house and to provide a return.

That all said, no new construction has swamp coolers. New houses are all wood construction, not brick or slump block or adobe, and they are MUCH better insulated with real dual-pane windows and real insulation and the like. Running A/C in a newer home is cheaper than in an older home where the single-pane casement windows are just leaky as hell.

[CatalinaWOW]

Comment 3 came from twenty years I lived in Tucson.  Regular maintenance is a fact.  Some will mind it, others won't.  Just like the periodic refreshment of the white elastic reflective coating on your roof.  And both of those chores are often neglected making them much worse when they are finally attended.