You might be seeing a lot of Internet Influencer Hype Advertiser Content
You Won’t Believe They Don’t Want You To See! lately about these so-called
personal air conditioners.
You might have wondered if these might be too good to be true.
And today I’m here to tell you that you’re right to wonder,
and the answer to your question is an absolute,
unequivocal,
indisputable,
irrefutable
probably.
This thing, as well as most of the devices out there which emulate its design including the Blaux?…
Blaugh?
Bloerp?... is a miniature swamp cooler.
Note; not air conditioner!
Despite what it may claim on the box.
Swamp cooler.
By the way, swamp cooler seems to be a rather US-specific term;
evaporative cooler is the more technical and also less gross term.
But swamp is just one syllable so I’m saying that.
It’s also just more fun!
Swamp.
Swomp.
Swawmp.
See?
Deal with it.
Swamp coolers do work, in fact in parts of the world they’re genuinely wonderful and
can sometimes negate the need for air conditioning altogether.
But these are not replacements for air conditioning.
If you live in a region of the world where the role of air conditioning isn’t just to cool,
but indeed to provide dehumidification,
well then these thing are just silly!
You see, these aren’t air conditioners by any stretch of the imagination.
However, in a sort of odd twist, swamp coolers do in fact use the same general sort of principle
as a conventional air conditioner.
They exploit the fact that as water evaporates, it takes energy from the air in order to do so.
I talked a bit about latent heat in my video on rice cookers.
At a very basic level it's simply that in order for a substance to change phases from
liquid to gas, it requires a lot of energy.
Water is, believe it or not, a substance and you can see this in action when you boil it.
It doesn’t just disappear when it reaches boiling point because it takes *more* energy
to cause it to vaporize.
The same thing happens when water evaporates.
You don’t have to get water up to boiling point in order for it to change phases.
You probably knew that already, the water cycle is a thing and we have rain and stuff
and the oceans aren’t boiling.
In any body of water, the water molecules close to the surface can, depending on conditions,
have enough kinetic energy to free themselves from the liquid phase fairly easily.
Of course extra energy, for example from the sun, will help but the key thing is no matter
how water changes phases, it takes a little energy for itself.
A device like this is simply using that concept to provide *some* cooling.
All it is is a fan which blows air past some sort of absorbent material which holds water.
The forced airflow and the large surface area provided by these paper flute things helps
the water to evaporate quickly.
As it does so it takes some of the heat energy in the air with it and the effect is that…
well you get a bit of cooling.
This is, by the way, exactly how sweating cools you off.
Fun fact!
The name swamp cooler is thought to have originated from the musty smell these often develop as
algae and other fun lifeforms take refuge in their mightily moist matrices.
If you’ve never encountered a swamp cooler before, well we’ll get into why that might be in a short while,
but you’ve probably experienced the concept at work in one way or another.
Those misting fans that blow not just air but also a fine mist of water at you?
Their goal isn’t just to make you annoyingly damp,
in fact the hope is that you don’t get wet at all.
Instead, the spray nozzles atomize the water into a very fine mist, which will quickly
evaporate and cool the air, sometimes a dramatic amount.
Even without the fan, if you’ve seen those mister things in a garden or whatever -
well typically that's the goal.
Cooling.
And that’s the same sort of thing that these devices do.
But there’s a big, big, big big big big huuuuge caveat.
See, where I live, air conditioning isn’t there just to make a space cooler.
It’s also there to remove moisture from the air.
In fact that was the original purpose of air conditioning - to dehumidify the air in factories
and other industrial buildings where humidity was causing problems on the production line.
Human comfort was just a bonus.
Air conditioners can remove moisture because the refrigeration cycle relocates heat energy
via a liquid refrigerant, which creates a very cold surface which water vapor in the
air will condense on.
OK, time to bring this guy out again.
I’m going to explain what actual air conditioners do,
and if you’re not interested in this part go ahead and skip to here.
But, I think it will help to illustrate why these fad devices are…
fad devices.
This is a basic window air conditioner operating via the refrigeration cycle.
This is about as small as they come, but for larger systems everything just gets scaled up
and sometimes moved around a bit
The refrigeration cycle really is almost magical, so here’s a brief overview.
For now, the only things we need to focus on are these pipes.
Notice that it’s a sealed loop, starting and ending at the heart of the system,
the compressor.
All these various pipes are filled with a special chemical called a refrigerant.
What’s so special about refrigerants?
Well, I’ll show you!
This is a can of R134a
(also known as 1,1,1,2-tetrafluoroethane).
It’s typically used in cars but is currently being phased out.
Now you obviously can’t feel this through your screen but this can is clearly filled with a liquid.
You can shake it and tell that there’s definitely something sloshing around in there.
Maybe you can hear it.
[sloshy liquidy sounds]
Put it on a scale and you can see that it weighs what it says it does plus the can.
But here’s the key thing - this would really prefer to not be a liquid right now.
The boiling point of this chemical is -15° Fahrenheit, or -26°C
That’s really cold!
So why is it still a liquid?
It’s at room temperature but also not a gas.
How?
Well, because it’s trapped in this can.
It’s under pressure, and when you confine a gas into a small space
(and thus increase the pressure it’s under) you raise its boiling point.
Right now, at room temperature, the pressure in this can is about 70 psi.
Not tremendously high.
And so long as it’s in this can, it will stay a liquid.
It doesn’t have room to expand into a gas.
But, if I were to puncture a hole in this can,
which I’m not going to do because this chemical is environmentally problematic,
it would instantly begin boiling once the pressure is relieved.
And the key is, in order for it to do that, it has to remove energy from the space it's in.
The latent heat of vaporization doesn’t just go away when the refrigerant is at a
higher temperature than boiling - it still needs to get energy from some place to change phases
- or boil.
It will initially do that from itself, causing the liquid to get very cold very quickly,
but then it will actually pull energy from its surroundings to keep boiling.
It becomes an area devoid of heat energy, so ambient energy will naturally spill into it.
That makes the air around it get colder.
But, once it’s all expanded to a gas, we’ve achieved equilibrium and the energy transfer stops.
The single most important property of refrigerants is that they don’t need to be under very high pressures
in order for us to raise their boiling point above ambient temperature.
This can really isn't that strong at all and yet it’s able to keep the refrigerant a liquid.
In fact, fun fact!
Those cans of computer duster you can buy?
Those are filled with a refrigerant.
If you thought that was just compressed air
Nope! It’s a refrigerant.
You need very strong tanks to hold back compressed air.
Just look at this little three gallon air compressor.
This tank is made of thick steel and when charged to its max of 110 PSI,
it barely holds enough air to fill a tire.
Because selling a can of compressed air would require expensive steel cans
that can accomplish hardly any dusting work,
these cans are filled with a liquid refrigerant which expands into a gas as it is vented by the spray nozzle.
[ffffssssssstttt]
This allows for much more dusting to occur.
And is precisely why these cans get cold as you use them!
It’s a refrigerant briefly refrigerating.
If you spray them upside down you’ll release liquid refrigerant
and you can witness it boil away with your very eyes.
[phwwwwwoooooosssshhh]
A slightly terrifying thing about these is that many refrigerants are terribly potent
greenhouse gases, and the idea that we just sell cans of the stuff with the express intent
of venting directly to the atmosphere is more than slightly unsettling.
This particular can is full of R152a, or 1,1-Difluoroethane.
Now, as far as refrigerants go, it’s not *that* bad.
It has a global warming potential of 140,
which sounds pretty bad but it's about about an order of magnitude less than R134a,
and also its atmospheric lifetime is only slightly more than a year
(again, about an order of magnitude better than this).
So, in all likelihood it’s probably not that bad.
Still, I would highly encourage you to look up what refrigerant is used in your preferred duster
(if you have one)
or better yet find alternative means of dusting your computer junk.
And by the way, this very same chemical is often used as a propellant in products like
spray paint and hair spray, and we used to use good ‘ol R-12,
everyone’s least favorite ozone-depleting chlorofluorocarbon (CFC)
trade named Freon for that task.
Yeah, the ozone layer still hasn’t forgiven us for that one.
But anyway, because you don’t need terribly high pressures to hold refrigerants in liquid form,
we can easily build a machine which will force it to condense and evaporate
when and where we want it to.
And that’s what an air conditioner or refrigerator does.
The compressor, which by the way is the same sort of thing as any old air compressor
but it’s sealed in this black cylinder so that it’s surrounded by refrigerant and also doesn’t leak,
squeezes it into the confined space of this first heat exchanger known as the condenser.
That causes it to get quite hot but more importantly increases its boiling point dramatically
as pressure in the condenser builds.
With the aid of these fins and a fan forcing air through them,
it will get cooled back down as it travels through the pipes.
By the time it’s at the end, it has condensed into a liquid.
Let’s take a look at that with a thermal camera.
This has been off overnight so everything is close to room temperature.
It’s amazing how quickly the condenser heats up, and also how uniformly.
Almost instantly the pressure is high enough for some of the refrigerant to start condensing
on the inner walls of the pipes.
And just as an evaporating refrigerant steals energy from its surroundings to boil,
a condensing refrigerant releases energy as it becomes liquid again.
That’s why the condenser gets hot - the refrigerant is releasing a ton of heat energy
as it changes phases.
Liquid refrigerant will eventually start to build up at the end of the condenser,
and it will usually be cooled down a little further
(which, incidentally, is called subcooling in HVAC parlance)
before it reaches the metering device.
This ensures a decent volume of liquid refrigerant is at the metering device in preparation for the next step,
and is precisely why the amount of refrigerant inside any given refrigeration system,
known as the charge, is so critical for proper function.
The restriction created by the metering device facilitates a dramatic pressure imbalance
between the two sides of the system, because just as the compressor is creating high pressure
on its output side, its input side creates suction and thus low pressure.
The metering device can be as simple as a capillary tube which restricts the volume
of refrigerant that can pass through it, or it can be as complex as a thermal expansion valve
which reacts to changes in thermal load to ensure optimal refrigeration performance.
That’s deeper than we need to be going, but once liquid refrigerant passes into the next chamber,
another heat exchanger called the evaporator, its boiling point plummets.
Now that it’s in a low pressure environment, it starts to boil just like the refrigerant
you release from a can of computer duster.
And it needs energy in order to do that, so it takes it from the air around the evaporator,
making it get very cold.
Again, let’s take a look with a thermal camera.
As soon as it’s switched on, the evaporator becomes a sink of coldness,
a place where energy in the room will naturally go.
The refrigerant in here NEEDS energy to evaporate, and it MUST evaporate because the pressure
is too low for it to remain a liquid.
The fins of the evaporator help it to scavenge energy from the air, which ends up cooling the room.
Once the refrigerant has reached the end,
assuming the charge is correct, it will have absorbed all the energy it can.
It will then re-enter the compressor and the cycle repeats.
Now the energy it just picked up from inside the room can be expelled in the condenser.
The conditioning part of air conditioning happens thanks to the fact that the evaporator
gets very cold.
Moisture in the air will condense on cold surfaces.
You’ve seen that before when holding a glass of ice water on a humid day.
That happens because air’s ability to hold moisture is dependent on its temperature.
Drop the temperature and it can’t hold as much water, so the water that it’s in it
condenses out of it and onto the cold surface of the glass.
Fun fact!
That’s how clouds and storms and dew happen.
Because the evaporator gets so cold and air rushes through its fins,
that air will lose its ability to hold moisture so it loses its water and the evaporator will get very wet
as time goes on.
Thanks to surface tension and gravity, that collected water (called condensate) will travel
down the fins into either some sort of drip pan or in the case of many window units simply
the bottom of the machine where it can seep to the outside.
Newer models like this will intentionally collect it around the condenser, and the condenser fan’s blade
(or even, as is the case here, a specialized component of it)
splashes water onto the condenser, increasing the efficiency and effectiveness of the air conditioner
through, somewhat ironically, evaporative cooling.
In fact, in this one, the condenser is actually shaped so that part of it sits in collected condensate.
And it’s done quite cleverly at the very end of the condenser's loop.
The refrigerant should at this point already be liquid and piling up at the metering device,
but the water will cool it further making doubly sure this actually happens and also
increasing subcooling, again that’s the amount the refrigerant is able cool further
after it has condensed.
That increases efficiency and effectiveness by allowing the evaporator to absorb a little
more energy after the refrigerant boils.
Remember that when it boils it first takes energy from itself, so in general the
cooler you can make it before it re-enters the evaporator the better
(though there is some nuance there).
Some people claim that this practice reduces the life of the condenser through promotion
of corrosion but those are just some people who didn’t engineer the thing.
Also, the evaporator which is exactly the same sort of thing, made of the same materials
and everything, gets wet constantly as it operates but I digress.
So here’s the key thing - the refrigerant in here is trapped
and is making a continuous circuit.
We’re forcing it to boil, then condense, boil, condense, boil, condense, boil and condense
over and over and over and over and over again.
And over again.
And most importantly, we control where those two things happen.
We’re using the properties of latent heat to our advantage,
in a deliberate and controlled way.
We call this a heat pump.
With it we can collect and concentrate heat energy in one location,
and move it to another to be released.
In one direction this will cool a room by moving heat to outside,
but the cycle can be reversed, which is becoming increasingly common.
Since the refrigerant is actually performing the work when it changes phases,
it can move four or five times as much energy as the heat pump consumes in the compressor
(depending on conditions).
It’s the closest thing we have to free energy, and is very neat.
Every real air conditioner, even the terrible single-hose portable air conditioners
which you should avoid at all costs as I explained here
(feel free to skip around that video as we’re covering some of the same things again)
has a hot side and a cold side.
The cold side collects energy, and the hot side releases it.
Move energy out of a space and you cool it, move it into the space and you heat it.
This thing, though… you’ll find no sides at all.
It’s basically just a wet sponge and a fan which presents two giant flaws.
The first is that there’s no self-contained loop.
While you most certainly can use water to cool air, once it evaporates you need to add more.
Water generally isn’t scarce
(except for where it is)
so for the most part this is more of an annoyance than anything else but it is noteworthy.
And the second flaw?
Well, now it’s time to answer the question at hand.
Do these even work?
Well, as a concept these can technically work.
In fact, you can even see a slight cooling effect going on here in the thermal camera.
I’ll emphasize slight, but honestly it is pretty interesting how it manages to achieve
cooling with nothing but room-temperature tap water.
And it was more powerful than I expected, with the air leaving it being about 2 or 3° F
below ambient temperature.
Yes, my expectations were indeed that low.
But now here comes the gigantic caveat.
The real dealbreaker is that, if you haven’t figured this out already,
a swamp cooler doesn’t dehumidify - it adds humidity!
In order for a swamp cooler to do anything at all, it has to help water inside it evaporate.
And that makes the ambient humidity go up.
In case you thought, oh, well no big deal, at least it’s cooler
well here’s the other thing - if the ambient humidity is already high,
then swamp coolers just don’t work.
They can’t work.
It literally becomes impossible.
The air has to be able to take on more moisture in order for the cooling effect to even happen,
and if you’re at or near the saturation point well then you’re just SOL.
The air that comes from this feels a bit cooler than air coming from an ordinary fan but…
not by much.
In this test I pointed the louvers so it was blowing right on this thermostat
(because apparently I don’t have a thermometer)
so I could get a fairly accurate temperature reading.
And, well, 64 degrees was the best it could muster.
That’s down from an ambient temperature of about 67 maaaaaybe 68.
So at best it produced a 4 degree temperature drop.
This becomes even more damning when you consider that
this was in an air conditioned space already!
Relative humidity was about 50% when I tested this.
Outside, though, it was around 80%.
It flat out would not work if it were my only source of cooling.
To really drive home how much like air conditioners these aren't, I used the thermostat again
to see what the air exiting the air conditioner was and… yeah.
That’s actually cold.
In short, swamp coolers only work up to a point.
And, because we’re dealing with relative humidity (which itself affects how hot a given
temperature feels to us) it’s anything but simple.
As a general rule, a swamp cooler could, assuming it’s a good one, cool to within a few degrees
of the wet-bulb temperature.
Now, what is the wet-bulb temperature, you ask?
Heh, well annoyingly it is the lowest temperature that can be achieved through evaporative cooling.
I know.
It describes itself.
Hang on, I’ll try…
Basically, the wet-bulb temperature is what a thermometer which has its bulb wrapped in
wet cotton or the like will read.
It’s affected by how quickly the water evaporates from that little cotton ball.
It presents the theoretical minimum temperature an evaporative cooler can hope to obtain,
and as humidity goes up, so does the wet-bulb temperature.
When humidity is 100%, the wet-bulb temperature is the same as the dry-bulb
(also known as… normal) temperature because the air cannot take on more moisture.
Given my sense of humor I’m sure I’ve been called a dry bulb a few times.
Honestly, all you need to know is that as humidity goes up the ability for these to work goes down.
I mean, that makes sense, given that they’re basically little humidifiers,
and explains why calling these air conditioners is super dumb.
Now, are they without value?
Well… it depends.
It might be nice to use this on my desk as a supplement to central air conditioning.
Maybe I could run that a little less.
After all a three degree temperature drop is definitely noticeable.
But certainly it won’t make a dramatic difference and it definitely isn’t going to cool the room.
In arid places, swamp coolers work amazingly!
Many people have them to supplement traditional air conditioning and it dramatically lowers
energy needs (at the expense of increased water usage).
And, since you typically want a little more humidity in aird places anyway, they’re a win-win.
Swamp coolers can also help the efficiency of split air conditioning systems by cooling
the space around the condenser coils and thus increasing their effectiveness.
Kinda like how this one pools the condensate around the condenser.
You can see this in practice in this video made by HVACR videos.
You should check out that channel if you want to see some of the various commercial refrigeration
and air conditioning systems out there up close, as well as the various ways they fail
and how issues are diagnosed and repaired.
It’s really a great channel for that sort of thing.
But here in the Midwest where humidity can often be oppressive,
swamp coolers don’t do much and actually just make things worse.
Now, this little thing, to its credit, suggests that you put ice cubes in it.
Which is, well, somewhat hilarious because then you’re actually using your
refrigerator to cool you down and you know what?
I approve!
Not in any practical way, of course.
It’s absolutely silly.
Your refrigerator made that ice by pulling energy out of water and dumping into your kitchen.
But technically it would work at least a ‘lil bit.
But in general these desktop personal coolers are only sometimes able to do anything at all.
It depends entirely on where you live and also varies day to day.
Now just because I’m not a total jerk about these things, I have in fact tested this in a few scenarios.
And while I think that sure, it provides a cooling effect, it’s not the miracle product
that you HAVE TO BUY that all of the ads out there are proclaiming them to be.
And how on Earth this little thing managed to get all these five star reviews is …
Suspicious!
And also, right now, these are horribly overpriced!
It is literally a computer case fan, a hunk of cheap plastic, and a bit of paper
with a tiny control board for everything.
It’s powered over USB and they don’t even give you the courtesy of providing a power supply.
These should cost no more than $25 and even then, that’s a lot for what it is.
Plus, the water absorbing material should be replaced periodically.
It gets gross over time, and do any of these companies provide replacements?
Who knows!
Keep in mind also that by adding humidity you’re making your air conditioner work harder.
Getting water to condense removes heat energy that we can’t feel -
that’s the whole latent heat bit.
So if you have a lot of moisture in the air, your air conditioner needs to run longer to
provide the same amount of cooling thanks to all that water that’s condensing on the evaporator.
Using a mini-swamp cooler in an already-humid place makes your struggling air conditioner
struggle even more (though admittedly, not much given the small amount of water this
thing is capable of putting out over a day).
So - these things.
Are they a scam?
Well, they just barely pull off a no on a technicality.
I mean, calling it an air conditioner is an outright lie.
But if they’re sold as “personal cooling devices” then… well yeah I suppose that’s technically true.
But they’re only useful in certain places and certain situations.
This is not a personal air conditioner, and while I wish it was as easy as
Just Add Water! I regret to inform you that it is not.
If you’d like to take a little test drive of this concept,
I’d suggest you make your own evaporative cooler to see if it would even do anything for you.
You could probably just glue a few kitchen sponges to a dinner plate in an upright position,
with a bit of space between them,
add some water so the sponges absorb it, and put that contraption in front of a small
desk fan and get way more cooling than this thing could ever hope to produce.
Any time you see a cooling device for sale which doesn’t require either a hose for
exhaust or actual installation, it’s not an air conditioner.
There has yet to be a device you can just plop on your desk and actually get air conditioning from.
In fact, that’s impossible.
So while I can’t quite call this a useless device, it’s alarmingly disingenuous,
terribly overpriced,
and almost always not worth your time.
Thanks for watching!
This is now, I believe, the third time I’ve explained the refrigeration cycle without
actually making a video specifically about it.
It really is a remarkable achievement of humanity, and heat pumps are going to become increasingly
common and important as we move into the age of electrification.
For sure you’ll be seeing a video about that before too long, and I think then we’ll
get into the real nitty-gritty like all those terrible refrigerants we used to use
and how we can move forward with grace.
But for now, le bloops.
♫ disingenuously smooth jazz ♫
But swamp is just one syllabo…
syllabo…
But swamp is just one syllabo…
syllable!
I said “syllabo”... twice now
Now the energy it picked up from cooling the process….
From the cooling process…
uugghghhg
But!
I think it will help to illustrate why these
.... oh I need it here, ha!
In fact, fun fact!
[clink as the nozzle hits the table] The… shoot.
And if you’re not interested in this part, go ahead and skip to here.
But, I think it will help to…
that’s right in front of my face, that’s a bad idea.
The air that comes from this feels a little bit cooler than the air coming from an ordinary fan, but
not my much.
Not My much.
It’s not MY much it’s YOUR much!
The way these things are marketed?
Not cool.
Oh I regret not working that into the script somehow.
But now it's the secret end joke, so yay!