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
blocks
blurp 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 u.s
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
swamp swamp 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 things 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 once 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 life forms 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
huge 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
okay 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 one one one two
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
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
minus 15 degrees fahrenheit or minus 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 those were 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
the 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
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
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 one one
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
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 hairspray
and we used to use good ol r12
everyone's least favorite
ozone-depleting chlorofluorocarbon trait
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 refrigerants 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 sub cooling 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 on 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'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 sub cooling again
that's the amount the refrigerant is
able to 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 although 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 are 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 are
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 the room by
moving heat to the 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 the 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 two
or three degrees fahrenheit below
ambient temperature
yes my expectations were indeed that low
but now here comes the gigantic caveat
the real deal breaker 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
maybe 68. so at best it produced a four
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 percent when i tested this
outside though it was around 80 percent
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 a 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
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 arid 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
kind of 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 it into your kitchen
but technically it would work at least a
little 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 well i think that sure it provides a
cooling
effect it's not the miracle product that
you have to buy that all 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 bucks
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 the water that's
condensing on the evaporator
using a mini swamp cooler and an already
humid place makes your struggling air
conditioners 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 the
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 les bloops
[Music]
but swamp is just one syllabus
syllable but swamp is just one syllabus
syllable i said syllable twice now
now the energy get picked up from
cooling the process from the cooling
process
[Music]
uh but i think it will help to
illustrate why these
oh i need it here in fact
fun fact like 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 mutt not my much it's not my much
it's your much
[Music]
[Applause]
you