March 25, 2013 • 51 mins
What’s the history of refrigerators? How is a refrigerator like an air conditioner? How does vapor compression work? Learn the cold, hard facts about refrigeration with Jonathan and Lauren.
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Speaker 1 (00:02):
In text with Technology with text style from how Stuff,
what's that coming? Hey then, everyone, and welcome to tex Stuff.
I am Jonathan Strickland, one of the two hosts of
the show, and I'm Lauren vocal Bon, the other of
the two hosts of the show. And today we wanted
(00:23):
to talk about something that's pretty cool. Oh no, yeah,
already started. We're gonna talk about refrigerators. And and here's
the interesting thing, guys, if you listen to the episode
that Chris Pallette and I did quite some time ago
about air conditioners, this podcast is going to sound very
similar to that because the technology is used in air
(00:43):
conditioning systems and the technologies used in refrigerators are essentially
the same, just one is a more small and controlled
and um not for people usually, right, No, there's some
notable exceptions to that. We are not going to talk
about those, guys, because that's creepy and probably belongs in
another podcast. Okay, so we're not talking about people in
(01:06):
refrigerators today, although now I can't think of anything else. Um,
but no, no, no, First, let's start with what the
definition of refrigeration is. So it's defined as the process
of achieving and maintaining a temperature below that of the surroundings.
And the aim of it is to cool some sort
of space or object to a required temperature, right, because
(01:29):
bacteria grow most rapidly in this and it's it's called
the danger zone. Actually in between I now I have
a new thing filling up my head. But okay, yes
that I debatably better than than Archer really and so okay,
well excellent, but so yeah, the danger zone is in
between forty degrees fahrenheit and a hundred and forty degrees fahrenheit,
(01:52):
which is a four point four to sixty degrees celsius.
And and in that temperature range, bacteria really just groove out.
They can they can more than double in in twenty minutes.
That population just explodes. And and bacteria and for things
like you know, food stuff that that we would consume,
that's not necessarily a great mix. That can lead to
(02:14):
u some pretty nasty contamination. Uh, it can lead to
some really serious health problems. And uh, and this is
why refrigeration is such a big deal. I mean, clearly,
before we had any kind of refrigeration, we had to
look at different ways to preserve food. Otherwise you pretty
much had to get food from the source and consume
it right away, immediately or as close to immediately as possible.
(02:38):
Or you had to cook it so that it would yeah,
so it wouldn't spoil as quickly. Or you had to
salt it like crazy so that again the salting would
would inhibit the bacteria from from uh from reproducing so quickly.
And even in refrigeration, we still have that uh, that process.
It's just slowed down quite a bit, which is why
(02:58):
you cannot leave food in a refrigerator uh indefinitely. It
will eventually go bad. Um. And then just like in
that great Far Side cartoon, the potato salad will hold
up the catchup when potato salad goes bad. So the
trick here, though, is how do you create this cool environment?
(03:19):
This this cold environment? Because adding heat two things is easy.
Taking heat away not as easy, less easy. And also,
before I get all my physicist friends sending in messages
about the use of the word heat, I do apologize
we're going to be using it in the vernacular quite
(03:40):
a bit because that's really what everyone's familiar with. But
to be clear, an object does not possess heat. It
has a temperature, but it doesn't possess heat, and objecos
will have internal energy as a result of molecular motion.
And heat is really the description of an energy transfer process.
And uh, you go from a high temperature object to
(04:03):
a lower temperature one. That is the basic concept of heat.
It's really an energy transfer. So when we say, like,
this object's got a lot of heat to it, uh,
that's a that's a completely colloquial way by saying it.
So I do acknowledge that. I apologize. But if you
really want someone who's going to be a stickler for science,
(04:24):
go bug Robert Lamb because he loves that the stuff
to blow your mind. Gay, Um, Robert's awesome. I love Robert. So, yeah,
that's the way heat works. Though you have high temperature
low temperature, then heat moves from the high temperature to
the low temperature. It does not go the other way around,
right without without some sort of external force working on
(04:47):
the system. Uh. This is essentially one of the basic
laws of thermodynamics. And so you've got this, Uh, you've
got a way. You have to find a way of
creating a lower temperature or environment to pull heat from
or to for heat to transfer from the objects that
(05:08):
are inside a refrigerator to make them cool. So that's
the basis of refrigeration. But you know, to get to
that point, we had to do a lot of stuff
and we had to understand a lot about physics for
this to become what we now all kind of take
for granted. Yeah, So to to get started, I guess
(05:29):
we can talk about what the predecessor was to the
modern refrigerator, which was the ice box, right, or you know,
going going way back in time, you had you had
people not even making ice boxes, but yes, just collecting
ice and putting it next to stuff. Yeah, or like
maybe you know, you might have a seller that you'd
put ice into, or you might just have a hole
in the ground, or you may just like if you
(05:50):
were in a part of the world where there was
a significant amount of snowfall. Uh, we here in Georgia
are not in that part of the world. We did
have some know the other day, I could see a
bare trace of it next to my steps. Some of
it landed in my hair when I walked my dog.
That was that was about it. But if you were
in a place where they get a significant amount of
(06:11):
snow and they're large snow banks, then one of the
things you might do is store some food inside the snow.
They're bury it in the snow and just hope that
nothing comes along to to grab that food. Or Yeah,
if if you've got an ice house, you can preserve
some of the ice with a sawdust or wood shavings.
Later on, cork was used to insulate it for a
few months anyway, until temperatures warmed up enough. Right right, Yeah,
(06:34):
you could. You could definitely slow the process, insulated enough
from the heat of the outside environment so that it
would preserve you wouldn't lose too much in melt off.
It took a while before people started to figure out
the best ways to keep ice from from melting too quickly.
And it's interesting because just as they were really getting
getting very good and making sure they kept ice uh
(06:58):
cold for as long as pas well, even in hot environments. Uh,
that's when the mechanical refrigeration technology had started to really
take off and it became less important. And these were
happening simultaneously, which is really fascinating to me. It was
in seventive that the first refrigerating machine was produced. I
believe it could make small amounts of ice in the lab. Yeah, yeah,
(07:21):
to to really understand well, first of all, the word refrigerator,
I found the I found the earliest use of it,
which was or at least earliest recorded use that I
could find, which was from fifteen fifty. But it was
all about using chemicals in water. People were discovering that
if they added certain chemicals to water for some reason,
the temperature of the water would drop. So if you
were to put something in a container of water that
(07:43):
had this chemical in it, you could cool that's something. Now,
if that's something was unprotected food and that chemical was poisonous,
that was not necessarily a great thing. But if that's
something were I don't know, a bottle of wine and
you happen to be French, this was a great way
to cool your wine. And in fact, in the Renaissance,
these cooled drinks became very popular, to the point where
if you added chemicals to water, it would drop the
(08:06):
temperature enough that if you put something in it that
that you could turn on a regular basis, you could
actually make ice this way. Um. Yeah, So this was
kind of an early ice maker, not efficient, not good
for producing ice on any kind of large scale, but
it was one of those things that the rich people
really enjoyed, and really those were the only ones who
had any chance of getting at it. Um. But yeah,
(08:30):
it was just before your the refrigerator unit type thing
you were talking about from the seventeen seventies. Seventeen fifty
five is pretty much when we talk about the origin
of the idea. That's when William Cullen made his machine
with which you used a vacuum UH and UH ether
(08:51):
to UH to create this UH environment where he would
put water into a container, put a smaller amount of
ether in there, put a essentially a vacuum bell jar
on top, you know, with a pump on it. By
creating the vacuum, the ether would start to boil off.
(09:11):
And when the ether was boiling off, when it was vaporizing,
he noticed that the temperature was going down in the
water and in fact, but when the ether would continue
to boil off, the water would start to turn into ice.
Now we'll talk about why that is a little bit later,
but this was one of those early observations that started
to lead people into thinking, you know, if we harness
(09:34):
this in some way, pretty cool. Yeah, there's no way
to avoid it. Voco boumb Join us together, we will
rule the galaxy. Jonathan. We need to we need to
chill out, Yes we do. Okay, all right, now too fast,
too fast. You gotta gotta pace yourself here. Um. So anyway,
(09:56):
this does form the basis. This, this idea of UH
vapor pulling out heat somehow, that is what was the
very basis of mechanical refrigeration. It would be quite a
while before the mechanical refrigerators would start to become a
real thing. Uh, I have a in eighteen o three,
you have a Thomas Moore obviously not that one different
(10:20):
Thomas Moore UH of Maryland. In fact, he received a U. S.
Patent for a refrigerator. Now this was not the same
thing as the mechanical refrigerators that would come later. But
that same year that was when the domestic ice box
was invented. So three you get the domestic ice box.
This was usually a wooden cabinet that you would put
(10:41):
a block of a large block of ice into the
top and then you would keep your food and and
and consumables in the bottom part of this cabinet, and
convection would essentially keep because because heat rises and cold sinks,
that which is which we know is the generalization was generalization, yes,
(11:01):
but but in general in this particular case, yeah, you've
got you've got the dense the dense cold air going
down and the and the less dense warm air moving up.
Because yeah, but we we understand that is a gross
over generalization. But for the purposes of this podcast, it's
effective enough. Yeah, you kept that ice on top. You
have a like a drip tray on underneath, because hey,
(11:22):
that ice is melting um, and so you would collect
the water which you would not just pour into the
top where it would magically become ice again. Essentially, once
that ice was gone, you had to go out and
buy more ice. And actually the ice trade was really
huge right around that time. In eighteen o six, I
think Frederick Tudor began his his ice empire. He was
called the Ice King. Yeah, um, when he started cutting
(11:45):
chunks out of the Hudson River in various ponds around
Massachusetts and then exporting it as far as China and Australia.
In India India. Yeah. Also what's interesting is that India
was the way the way they were producing ice in
India at this time was through a process called nocturnal
radiative cooling. Right, I was reading about this this it
(12:05):
took me a while to grasp how that work. I
still did not understand it. So, I mean what I
w I understand that basically they were doing was putting
water in shallow clay trays and setting it outside under
the open sky overnight and then in the morning ice
would be there. Yeah, what what essentially is happening is
that the uh, it's there is another physical process going
(12:27):
on here. But you've got you've got a tray of
water outside. The sky needs to be clear because what's
happening is the heat is radiating from the water out
into the atmosphere and escaping that way. Now, if there
are clouds, then the heat can radiate back down too,
because it's like an insulator. It'll it'll end up insulating
the earth and you end up you don't get enough. Right.
(12:53):
But otherwise, even if the the ambient temperature outside is
still right around freezing or just above freezing, you can
still freeze water that way. Under a clear sky also
helps if it's a very dry climate. Right, And and
from what I understand that it's important that it's a
it's an earthenware tray because that way you get some
of the uh, well, you have to have that insulated
(13:15):
effect there as well. It's the earthen tray and there's
usually hay underneath it, Yeah, some kind of compressed Yeah.
So it's it's interesting that that was the way that
India was producing ice, but that was not a very
again and a very efficient way of producing ice. You
couldn't produce a lot of it, and uh there was
a big demand. So Tutor was really raking it in
(13:36):
by harvesting ice in the United States, just natural ice.
Not he's not producing it in any mechanical means. He's
actually going out and digging it up, packing it in
wood shavings and that sort of stuff, cork, that kind
of thing, shipping it to the other side of the world,
and making huge bank off of it, huge bank. And
I want to mention that also right around this time,
(13:56):
in UH seven, ammonia was first liquefied in a laboratory, right,
which will becoming point um, So just keep that in
your heads for a second. And um. And then also
in eighteen o five, right before Tutor began his big
ice trade, UM, Oliver Evans described did not create but
described a closed at their vacuum refrigeration system. Yeah. So
(14:17):
this is the same sort of of mechanical system that
would eventually become what we use in refrigerators, most refrigerators,
I'm saying refrigerators in general, but there are different types. Yeah, well,
we'll mention a few, but but the we're focusing on
what most of us have available in like in our kitchens, uh,
(14:39):
and maybe our basement if Okay, I'm not going to
go back there. It's dark base to a dark placed
voco bomb really early on, I'm very fond of that
of that documentary American Psychos. Okay, that's fair. In eighteen twenty, Uh,
this is interesting that the Michael Faraday was working again
(15:00):
with liquid ammonia, and that's when he started realizing that
liquid ammonia, which ammonia is naturally at room temperature, is
a gas, right because it boils it at like negative
twenty seven degrees fahrenheits. So, so to to liquefy it,
you have to compress it, you have to pressurize it
to make it a liquid. And he realized that when
(15:20):
it went from liquid back to gas, it caused cooling
and so again another important part of this mechanical refrigeration. Now,
in one a German physicist by the name T. J.
Cbeck discovered that if you have two junctions of dissimilar
metals kept at two different temperatures, it induces electromotive force
(15:44):
or electric currents. So what that means is that, let's
say that you have a junction of a copper wire
and an iron wire, all right, and then you have
a second junction where the iron wire is attached to
a second copper wire. And let's say you were to
heat up that, uh, that first junction and cool down
the second junction, perhaps put some ice on it, you
(16:05):
would actually induce electricity to flow through that wire. Now
that's important because in eighteen thirty four, uh Peltier discovers
that if you do the opposite, if you put electricity
through a series of wires that have these kind of junctions,
one side will heat up and the other side will
cool down exactly and then by up to I think
(16:25):
forty degrees fahrenheit. It all depends on what kind of
material material you're using. Uh. In fact, this sort of
is called the Peltier effect. Actually, but this sort of
effect is dependent upon the types of metals or or
materials you're using and uh, their purity. If you're using
pure metals, the effect is is pretty small, so small
(16:47):
as to not be very useful. It's interesting in the
laboratory setting, but not terribly useful. Also, if you're using
pure metals, they tend to be very good thermal conductors,
which means that that that difference in temperature will not
mean taine itself for very long. You will eventually have
the the heat will move from the high temperature to
the low temperature and balance that out. Uh. Meanwhile, if
(17:10):
you were to use an insulator, then you wouldn't get
the effect, So it would take years before anyone would
find a way to make that useful. But that is
used that That same technique is used in some electric
little portable refrigerators, things like the kind of stuff you
might plug into your your car outlet. Yeah, basically, you
(17:31):
just get a whole bunch of these junctions set up.
You put the hot ones outside the unit, the cool
ones inside the unit. Fridge. Yep, that's exactly it. So
so spoiler alert, that's how that one works. But we
thought if i'd be interesting to talk about that. But
that's that was what caused was the basis of that
sort of refrigerator. UM. And that same year, in thirty four,
Jacob Perkins developed a vapor compression cycle refrigerator using ether.
(17:55):
So you got a lot of people working on patent
for it. Happened that year m H and UH eighteen
forty four you had John Gory proposing an air cycle
refrigerating machine for making ice. UH. Eighteen fifty you had
Rudolph Clauseus who said heat can never pass from a
colder to a warmer body without some other change connected
(18:15):
there with occurring at the same time. This is what
I was talking about at the top of the podcast.
It's kind of a rewording of the second law of thermodynamics.
It's related to that. So UH, that's one of the
the principles that guided refrigeration as well. UH. In eighteen
fifty one, our buddy John Gory from back when he
had proposed that air cycle refrigerating refrigeration machine to to
(18:38):
create ice. In eighteen fifty one, that's when he got
the another patent for mechanical refrigeration. And in eighteen fifty
five Alexander Twining starts his first commercial ice making plant
using vapor compression refrigeration. We'll explain what that is in
more detail in a little bit. Eighteen fifty six, commercial
refrigeration begins in industries like brewing and meat packing. Now,
(19:01):
commercial refrigeration did not necessarily mean they were using mechanical refrigeration.
They could be using natural refrigeration, as in going out
and buying lots and lots of money and packing stuff. Um.
It's interesting to me that brewing picked up on this
really quickly, like like the brewing companies were like, we
want beer that tastes good. It's as though alcohol technology
is something that drives industry in some way. Yeah. Meat
(19:24):
the meat packers were slower to follow suit, which is disturbing.
Spoiled meat was something everyone was used to write and
if you're drunk enough, you don't care. Okay, got it.
I understand now. As someone who does not imbube alcohol,
it was just completely foreign to me. But I don't
eat meat either, so what do I care? Um. Also,
we're no longer in the eighteen fifties, as it turns out.
(19:46):
But yeah, meat packing was slow to adopt this technology,
but it did start it back in the eighteen fifties,
and the majority of plants wouldn't switch to mechanical refrigeration
until about nineteen fourteen, and by then you were getting
into a really like a booming time of refrigeration. But
backtracking just touch in. In eighteen fifty nine we had
a Ferdinand car of France who developed an ammonious slash
(20:10):
water refrigeration machine. Eighteen sixty eight you had Peter van
der Wide. Uh. He patents thermostatically controlled refrigeration systems. That's
going to be important when we get to the modern refrigerator.
Eighteen seventy Carl Lynn publishes a paper called the Extraction
of Heat at Low Temperature by Mechanical Means, and he
designs the first practical portable compressor refrigeration machine in eighteen
(20:33):
seventy three. Uh. In eighteen seventy seven, that was the
peak of the ice trade, so in the US that
it hit its peak right And the late eighteen seventies
the United States was exporting almost almost a quarter of
a million tons of ice to other countries. So uh, yeah,
(20:54):
a lot of ice leaving the United States. Um and uh,
it's interesting to me that at this point where the
ice trade is at its peak, but mechanical refrigeration is
already in its infancy. The only reason that mechanical refrigeration
even started to take off, it wasn't because the technology
(21:15):
was getting great. It's because the ice trade was starting
to encounter problems. Once it gets to about the eight
nineties or so, like, if the ice trade had not
encountered problems, then even with the technological advances in mechanical refrigeration,
we may not have seen refrigerators in the United States
(21:36):
for another you know, I don't know four or five decades,
but so, yeah, and that what happened was was that
as people were essentially mining ice, you know, cutting away
ice from these rivers and ponds, they were starting to
uh exhaust the clean sources of water and so more
(22:01):
and more of the ice. The demand was growing, right,
and the supply was diminishing. Not that we were running
out of lakes and rivers and stuff. It's just the
demand was so great that there wasn't enough to go around. Yeah,
there's not there's only that are frozen, and the Hudson
is really big and stuff. But yeah, I mean when
you're talking about a quarter of a million tons, right,
so you're talking about tons of ice that might have
(22:23):
things like sewage in Uh, not so great when you're
using it in the meat packing industry as it not
maybe not such a big advantage over spoiled meat. Um yeah, so. Uh.
It's because the ice industry was starting to have these
issues that we began to see the rise of mechanical refrigeration.
(22:45):
Was when a trade journal called Ice and Refrigeration began
to publish. Nineteen o four was when the American Society
of Refrigerating Engineers was founded. By the way, the American
Society of Refrigerating Engineers, I learned, was about engineers who
were experts in refrigeration. It was not a society that
would actually refrigerate engineers. Because the way it was worded
(23:07):
it was confusing. I find that difficult to believe, Jonathan.
I think you should check your sources. American Society of
Refrigerating Engineer. It does sound like you're just shoving a
guy with a hard hat into a fridge, and that
brings us back to American Psycho. Nineteen eleven, General Electric
introduced the first domestic refrigerator. Depending upon whom you ask, right,
(23:27):
we should also point out that when we've got these
dates and saying who brought out the first one, etcetera, etcetera. Uh,
there's some dispute in them, and it all, like I've
seen conflicting time. The history and especially uh scientific incorporate
history tends to be written by the victors and um.
So therefore sometimes you know, you have in different reports
(23:48):
differ about exactly who won that right and you know
exactly n according to some sources, that's the first electric refrigerator.
According to actually frigid Air's timeline tell you specifically, nineteen
sixteen was when models like the Kelvinator and Servel were introduced,
and in nineteen eighteen General Motors purchased Guardian Refrigerator Company
(24:10):
and renamed it Frigidair. So nineteen eighteen was when frigid
Air as a thing became a thing like it existed before,
but it didn't exist in like, it didn't have the
frigida name. And frigid is where we get the word
fridge from. I do believe, I believe so. And it's
also they that's the company that developed free on, which
we will talk about a little bit in just a moment. Yeah, yeah,
(24:30):
so way up in the nineteen thirties, we've got like
one other point to cover before then I've got I've
got a couple more. Actually, because i've got I've got three.
In the twenties, here we go, Oh goodness. In the
USA there were about twenty five million domestic refrigerators, only
seventy thousand of which were mechanical. So these refrigerators, some
of them were more like the ice box refrigerator. Um.
(24:52):
I remember, I remember watching like Lassie growing up, that
that the mom and Lassie had an icebox, not not
a fridge. Random mom in the last Sie, not the
mom and Lassie. From all I thought, Lastie had its
own fridge, and like that dog was luckier than I was.
Seven was the first porcelain on steel cabinet refrigerator, which
is that's the one I always think of, like the
(25:13):
nineteen fifties refrigerator, the big porcelain ones. It looks a
little bit like a rocket. Yeah mine, mind is mind's
a steel refrigerator. I've got the sameless steel thing going now. So,
but I don't I remember the one, the porcelain ones. Uh.
THEE was when Frigidair introduced the first home food freezer,
and it was a chest style freezer, so you know,
not the not the upright type, not not incorporated into
(25:36):
a refrigerator. Um. And that was right around that time
is when uh, Frigida starts to introduce chloro floral Carbon's right,
I believe that DuPont had developed it's also called a
free on. Yeah, that's the patented specific lora flora carbon
that Frigida introduced. Um. And yeah, before then, UM, some
(25:57):
of the very early fridges I believe, were you using
sulfur dioxide, Yeah, sulfur dioxide, methyl chloride, ammonium. Yeah. And
these are all chemicals that are toxic, toxic, so whenever
there were accidents, and you know where human accidents happened, uh,
then uh, sometimes people were really badly injured or even
they died even as a result of being exposed to
(26:20):
these sort of chemicals. And so there was a big
incentive for companies to develop refrigerants that were not toxic.
And so that was the reason why companies were looking
into something like a chloral fluora carbon. Now, later on
we would learn other downsides to chloro fluora carbons, which
we'll talk about in a second, um, which is why
(26:40):
we don't use them anymore. Now. In nineteen thirty one,
that was the first use of free on as a refrigerant,
So it was kind of introduced in nineteen twenty nine,
and by it was being incorporated into the design and
mechanical refrigerators. In the first refrigerator freezer combo with the
freezer having its own separate section was introduced, so you
(27:01):
that was where you know, you would open up the
fridge part or you would open up the freezer part. Um.
And in nineteen nine, Soviet engineers discovered a way to
create thermoelectric refrigeration systems using the the Peltier effect by
using semiconductor material because you know, like I said, those
pure metals weren't producing enough of an effect for it
(27:21):
to be useful in any way. They found that by
using semiconductor materials they could create a temperature differential that
was effective enough for it to be used for something science.
So yeah, they actually started creating refrigerators using that thermoelectric
system rather than the vapor compression system that was being
used pretty much everywhere else. Also in in ninety nine,
(27:43):
the business was so booming that seven million refrigerators were
being produced in the US annually. Nice and in fact,
my timeline ends at nineteen nine, because I didn't write
down specifically the bit about the nineteen seventies where right
around nineteen sent was when we started figuring out the
chloral fluora carbon we're starting to accumulate in the atmosphere, Yeah,
and eat through the ozone layer, which is not the
(28:04):
science for that, that's right, right, but that it was
it was in fact harming the ozone layer, and that
was what gave the incentive for us to develop something
besides that, which is why these days hydrofloor carbons or
isoputane or yeah, those are the those are the main
too uh to be used because they don't have the
same environmental impact nor that they have the same toxicity
(28:28):
levels as the previous refrigerants before free on. Yeah, ammonia
and things are still used in industrial capacity because they
assume that someone who has you know, um, five thousand
dollars to drop on a refrigerator is going to or
five thousand dollars more on top of what you would
normally spend, is going to take a little bit better
care with the care of it and not you know,
let the dog eat through the back end. It's it's
(28:48):
it's one of those things. Also where you're talking about
efficiency as well. Ammonia is a very efficient refrigerants. So
that's that's you know, when you're talking about a large
scale production, efficiency ends up being the difference between a
profitable year and a disaster. Yeah, especially when you've got
health inspectors coming through making sure that you do not
have any food that is entering that danger zone that
I talked about. Right, So that that kind of brings
(29:11):
us up to speed to the general refrigerator of today.
Let's take a quick break to thank our sponsor. Okay,
so I think it's time we start talking about the
actual process of refrigeration and how the modern day refrigerator
in general works. Do you mean the technology of it,
like we're like we're at tech as if we were
(29:32):
talking about the stuff that is techy. So, so you're
using essentially the refrigerator cooling system is a closed system, right,
It's a closed system. Think of it as a series
of tubes, so it's its own Internet, but a series
of tubes that are all connected to one another. There
(29:53):
there's no external you know, venting or anything or intake.
So you've got a system where you're using a refrigerant
Like we were talking about in those early days. Yes,
some sort of some some sort of of material that
at room temperature is a gas. But when you pressurize it,
(30:13):
you can make it a liquid. And that's the key.
So Um, if you if you're having trouble understanding how
this works, think about like you get some rubbing alcohol
and put a little bit on your skin, and you're
gonna feel that it it feels very cool. And that's
not because the rubbing alcohol itself is at a cool temperature. Yeah,
(30:33):
that the liquid in the bottle, when you hold the bottle,
it can feel like it's the simply of the same
temperature as the room. Right. But but the thing is
that rubbing alcohol will start to evaporate at room temperature.
So when you put it on your skin, as it evaporates,
you're gonna feel your skin cool down. That evaporative effect,
it's as the the liquid is turning into a vapor,
it's pulling heat. Uh through part of that physical reaction,
(30:57):
and the reaction the energy that is required to turn
something from a liquid to a vapor. UM sucks in
energy heat energy from right around and you've got the
higher temperature generated by your body. So that's where that
heat can come from it can pull the heat from
there to help fuel this reaction. Essentially, again we're kind
(31:18):
of oversimplifying, but yeah, but we're also not not physicists,
and so we also don't have visual effects to show
you what we mean, which makes aside from our own gesticulation,
which is really only benefiting us. Yes, we can. We
can also do the safety dance in here. Apparently that's
that's what looks like whenever I start talking, Um, that's
just the way I am. But okay, So you've got
(31:39):
the coolant in your refrigerator, which is called a refrigerant.
The coolant moves through a series of coils and through
different parts of the system that the coolant is either
going to be in a liquid state or a gas state.
Now you have to think of this system in its
various parts so on. It's kind of hard to say
(32:00):
on one end of the system because really, in a way,
this is kind of like a big circle, So you
don't have a start and an end. Really, I think
it's easy to start with that with the compressor compressor.
So I've got a compressor. The compressor is, of course
does what it sounds like. It does It compresses compresses
the gas. So it's uh, well, it compresses the cooling
at the at the time. Yes, it's a gas, it's
(32:23):
compressing it. So it's coming in through Uh, it's pulling
in gas and compressing it. Now, remember we said that
heat is not a thing that an object possesses. Instead,
an object possesses some sort of internal energy. So if
you were to pressurize something like a gas, If you
were to pressurize a gas, uh, or you were to
(32:45):
heat up that gas, you would increase the molecular movement
there and just from being just from observing the gas itself,
without having any knowledge of how it got that way,
you would be unable to tell whether it a cheat,
its internal motion through heat, pressurization, or some combination between
the two. They would be indistinguishing. Look the same, right,
(33:07):
So essentially what I'm saying is that compression and heat
gets you the same result. So you are compressing this
gas and as a result, the temperature of that gas
up all right, So you then create this long series
of coils. This is on the outside of the fridge.
(33:29):
The compressor is right ready to edge of the fridge.
It it draws the air in it draws the gas, right, sorry,
draws the gas from the fridge out to the outside,
compresses it and then yeah, and then it proceeds up
through the series of coils coils. Yeah. And you keep
in mind, like I said, this is totally a closed system.
This this gas is not exposed to the interior of
(33:50):
your refrigerator. There's it's always in in tubes essentially, it's
always in pipes. So it's going through after it gets compressed,
it's heat heats up. It doesn't it isn't heated up.
It heats up through the compression. Uh, and then it
goes through this series of coils. As it goes through
the series of coils and the outside the refrigerator, it
starts to lose some of that it you know, the
(34:12):
heat moves from the coils to the surrounding atmosphere. Right.
That that that is the purpose of these coils to
to cool down this air to the point that it's
going to gas. Okay, I just don't want it to
be too too vague, but yes, yes, exactly, it's it's
cooling down the gaseous coolant, right because because at this
(34:35):
point that that compressed gas is at a higher temperature
than the ambient air around it. So if you were
to touch one of these coils, you would feel it
was very hot. We don't necessarily recommend doing no, don't
do it. And this also shows that the refrigerator is
only going to work if it's in an environment that
is cooler than what the coils are. Like if if
(34:56):
for some reason you put a refrigerator in the middle
of a volcano then they degrees, it probably wouldn't do
well because because then you have the temperature of the
surrounding environment is higher than the temperature of the coils,
the heat transfer would move in the opposite direction. Gas
would never cool down. So so clearly you have to
have a cooler temperature in your environment. In this case,
(35:18):
it's in your kitchen, and your kitchen, while even when
you're cooking full blast feels like it gets pretty warm,
is nowhere near as hot as those those coils are. First,
when the gas is compressed, so as it moves through UH,
it starts to cool down and it begins to condense
and under that compression, under that pressure, this condensed cooler
(35:39):
gas becomes a liquid. Because as you increase the pressure
on a liquid, you also increase its boiling point. So
if you were to take a uh, let's let's take water. Okay,
So water boils at two and twelve degrees fahrenheit or
one hundred degrees celsius, So much easier to talk in
terms of celsius. Although I'm totally I'm so used to
(36:03):
everything else being in fahrenheit that water is the only
thing that makes sense to me in celsius. So, but
that's because I'm an ignorant American, alright, So uh and
I'm not saying all Americans are ignorant. I'm saying I
am so. Anyway, Um, So, at a hundred degrees celsius,
that's normally when water would boil, right of water under
one atmosphere of pressure. If you were to increase the
(36:24):
pressure on that pot of water, Let's say, let's say
we somehow put a pressure cooker around this, this pressure
canister around this pot of water and increase the pressure
on that water. That would also increase the boiling point.
So you would actually have to go over a hundred
degrees celsius in order to get that water to boil.
The same sort of idea here, you've got this compressed gas,
you've got condensed down into a liquid. That means the
(36:46):
boiling point has gone up. So as long as that
that liquid is under pressure, the boiling point is higher
than it normally would be. That's why it can be
a liquid. All right. So you've got this liquid it
would normally be a gas at this temperature. How do
you make this liquid suddenly magically make everything cool again? Well,
you've got to have a valve, an expansion valve Jule
(37:09):
Thompson or our Juel Kelvin, depending on on how how
you want to say. Uh, Lord Kelvin, Lord Kelvin, Yes,
came up with this with this ingenious little valve concept
where if you have a high pressure liquid on one
side and a very tiny hole and a low pressure
area on the other side, stuff happens. Right. What happens
(37:30):
is that liquid will pass through that expansion valve once
it gets to the area of low pressure. Now you
don't have the pressure on there anymore. Once the pressure
is gone, that boiling point goes back down to where
it normally would be. Now again, with the refrigerants you're
using in the refrigerator, that boiling point is way lower
than room temperature. Yeah, yeah, negative twenty eight degrees fahrenheit
or negative thirty three degrees celsius. So that's when this
(37:53):
liquid would normally boil off into a gas. Okay, here's
the other the cool thing about boiling points. Let's say
that you are magically inside an oven. Don't ask me
why you went in there, but you're okay, for some
of you, you're very heat resistant. Okay. Now you've got
you have that pot of water from the pressure experiment earlier,
(38:13):
because you don't like to waste, right, so especially not water.
It's a it's a precious resource. So you've you've taken
that pot of water with you into the oven, and
you're watching the water and the temperature inside the oven
is four hundred degrees and you're watching the water boil,
and you you have a thermometer inside the water. It
doesn't have any contact with the metal or anything. It's
just measuring the temperature of the water. The temperature of
(38:34):
the water. Even though the oven is four hundred degrees temperature,
the water is still going to be assuming regular pressure
two twelve degrees fahrenheit one degrees celsius, because that water
cannot physically cannot go above that temperature. Not not a
liquid form, no because as when you're in liquid form,
you can go only up as high as the boiling
point and then you turn into again. So so the
(38:56):
water itself is at one hundred degrees celsius so to you,
because you know you're in the four hundred degree air,
to you, the water would actually seem cold, right. So
that's the whole idea is that once it goes down
to this boiling point, the temperature actually drops dramatically. So
it goes through the expansion valve. The liquid, the highly
pressurized liquid, goes through this expansion valve, hits the area
(39:18):
of low pressure, immediately boils off and because most of it,
from what I've read about half of it boils off. Well, yeah,
because again you're getting into this low pressure system, which
means that now that that uh that it's no longer
confined by the high pressure, which means now it can
it can boil off into its vapor form, which means
that it starts pulling in the heat to essentially be
(39:43):
part of this uh this uh this process. Yeah. Yeah,
as as the process happens, it pulls in heat necessarily
because that is where the energy for the process comes from.
So what what that means for your refrigerator. Is that
the interior of your refrigerator, all the heat that's contained
within the interior brigerator moves to these sucked into the pipes. Yeah.
So that the same series, the same source series of
(40:05):
coils that you would find on the outside of refrigerator,
something similar to that is on the inside of your refrigerator,
only there, instead of putting heat out, it's pulling heat in.
Because it's pulling heat in from the interior of your
your refrigerator and freezer. There's just there's really just more
length of it and your freezer than there is in
your refrigerator. That's the difference there. Yeah, so so so yeah,
(40:28):
this liquid, this half liquid half gas, is running through
the coils inside the body of the fridge, and fans
are blowing air across the coils through the food part
of the fridge, which which continues to to vaporize the
rest of the liquid into gas and continues to pull
more heat, more heat. Yep. And that's what makes the
refrigerator cold. So really it's not that it's not that
(40:50):
the refrigerators pushing cold in, it's pulling heat out. So
that's something because I mean, which is so cool Yeah,
when you open up refrigerator and you feel that little
blast of cold air, you just think, oh, there's something
magically Yeah, that's not what's happening. So but it is
really neat to think about that that's all going on
at the same time. So you're really you're talking about
too closed systems. The closed system of the interior of
(41:12):
the refrigerator where all your food is, and the closed
system of the actual coolant that's moving through And um, yeah,
that's that's the basic idea. Oh and once it gets
once the gas gets to the end of that part
of the cycle, you know it's it's completely in gas form,
it's no longer pressurized. That's when the compressor pulls that
gas through to move it all the way through the
system again. So it's reusing the same coolant over and
(41:35):
over and over again with with no waste. Right, assuming
there are no leaks in the system, you're good to go.
If you've ever had to have a refrigerator or freezer unit,
if you had to have coolant added to it, this
happens frequently I've seen with air conditioning systems, uh climate systems.
Then that means there's probably there has to be a
leak somewhere in there because it is a closed system,
(41:56):
and otherwise you shouldn't really have any loss, at least
not any appreciable loss. Yeah. So that's the basic way
of fridge works. I find it super interesting. I almost
said cool, I almost did it. I almost said I
didn't want to do that. I think, did I do
that a second ago? I apologize. I apologize for accidental
puns guys, But uh, you might be wondering, Okay, well,
(42:19):
my refrigerator allows me to set a temperature, right like
I can choose to either go super cold. Yeah, for
for my freezer, I wanted to be as cold as possible.
Or you might think, well, no, that's gonna use up
a lot of energy. I'm gonna be a little When
when when the stuff in your cheese rawery starting to
frost over and you start going like, yeah, this is bad.
(42:40):
So what what governs that is what's called a thermo couple,
which is essentially a thermometer and a switch. So the
thermometer detects the temperature the interior of the refrigerator, and
when it drops below whatever the temperature is set to,
it turns off electricity to the compressor, so the compressor stops,
which means this whole cycle that we've been talking about stops,
(43:03):
and then if the temperature creeps up above it again,
it turns electricity back on. Yeah. So that's when if
you've ever heard your refrigerator just kind of kick on,
that's what's going on in you know. The more modern
ones do this really efficiently, so you don't have it
happen as frequently or as dramatically. I remember an old
refrigerator I had where you thought that, you know, perhaps
Steven Spielberg was filming Poltergeist for in your kitchen every
(43:26):
time I kicked in. Yeah. Modern fridges also do contain small,
low wattage heaters which just keeps the evaporator coils at
the correct temperature and not frosted over um, which which
I find also fascinating. Just yeah, like like fridges contain heaters,
that's the thing that they do. Yeah, And you know,
obviously refrigerators can have lots of other bells and whistles
on them. Of course. Sometimes literally, my my refrigerator does ding,
(43:49):
uh if I like, if I am using the there
has a water dispenser, right, so it intakes water from
my my house's water system and puts it through a filter,
and then I can get a nice clean glass of water.
But if you open up a the other door, it's
a it's a double door refrigerator. Do you open up
the other door, it cuts the water off. You can't.
(44:10):
You can't dispense water while the door is open, and
if you have depressed the water dispenser, it will bring
at you and mercilessly chide you for trying to do
two things that are not compatible. Because I frequently forget
while I'm getting a glass of water. I'm thinking, you
know what would go great with this water, That enormous
hunk of cheese that's in my refrigerator, and then my
(44:32):
refrigerator tells me that, yes, indeed, that would be lovely.
But you need to wait until you've either gotten the
cheese or finished getting your glass of water. You cannot
do both at the same time. That's great. I love
it with electronics. Chide man. By love, I mean hate,
I hate that thing well. And there are other kind
of interesting like additions you can get. LG has a
beer chiller. That's so, this is this thing. I actually
(44:55):
got to see this in person at the one like
the innovator or yes, it did. It did. It won
one of the Innovation awards. Uh and uh so this
is like a tiny little thing chamber within the refrigerator
part itself. It's called a blast chiller. Yeah, it's designed
it's designed to take a well, the demo was a
(45:17):
can of beer from room temperature to ice cold within
about five minutes. And uh and essentially it's doing the
same process we talked about right here. It's just that
I imagine there are more of those coils. It's a
very small chamber and very controlled. Yeah, there's their fans involved.
I mean, it's it's they're they're they're trying to increase
the circulation of air and the h and the surface
(45:40):
area that the cold coils have so that it pulls
heat as efficiently as possible, so that you can have
your frosty beverage when you want it, or at least
five minutes after you thought about it. Um. And that's
assuming you want one can. If you want to, it's
gonna take about eight minutes because it's more for it
to more heat for it to disperse. Um. But yeah,
(46:01):
there's there's stuff like that, and then they're smart refrigerators. Right, Yeah,
now you can you can have your fridge tell you
what's in it and what kind of recipes you can
make with that, and yeah, and send information to other
elements in your home, assuming that they are made by
the same company and are compatible, are willing to talk
to each other. Yeah. So the the idea here, of course,
(46:21):
is that it's not a new idea. It's one of
those things that people have been trying various to implement
in various ways. But now that we have smartphones, it's
a little bit it's a little easier, Yeah, because you
can you can connect a smartphone to a refrigerator and
scan things in that way. That was that was the
big issue, right, was that how do you tell a
refrigerator what's inside of it? If you have to stay
in there and manually input onto probably a really miserable
(46:44):
touch pad on the refrigerators surface, exactly like how many
bananas you have? I don't. I never want to do that.
I don't put bananas in the refrigerator. I do not. Thinking. Okay, well,
Foco bomb, I've found your problem. Uh no, but you
are you are correct that that's that's the barrier, right,
How do you make it so easy. And you know,
there were people who are talking about, why don't you
(47:05):
put r F I D chips and or strips of
some sort onto various products and then you could just
have it scanned when you put it in. But then
other people were saying, wait, if you have r F
I D chips, you can end up tracking everything that
someone buys, whether they want to be part of a customer,
you know, or not. Yeah, and there are people who
are very sensitive about that, and I can completely understand.
(47:27):
You know, I personally I don't worry about it that much,
but that's just because that's who I am. I'm waiting
to do it so that I can get sent yogurt coupon, right,
you know. But but I'm I totally understand the people
who are like, no one has any business knowing what
I buy. I go out and I buy it. I
buy it with my money. It's my exchange. That's all that.
That's where it should end. And I totally respect that.
(47:50):
But so that that the r F I D thing
never really I mean, I've seen some implementations of it,
but I don't expect that off the ground. Yeah, because
it would also require the entire food industry to change, right,
all the packaging would have to change. And that's when
you look at that across every single company that makes
food that's designed to go into a refrigerator. That's a
(48:10):
lot of money that that would require billions of dollars
of investment from various companies. Yeah, for for relatively low
usage point, I think, yeah, especially right now because we're
talking about you know, right now, I don't think there
are that many people who have smart refrigerators, and again,
like to get one that's really useful that can work
with something else. Like say you're your oven so that
(48:30):
you know, you pull up a recipe on your refrigerator
and it's it's telling you what you can make based
upon the ingredients that you that it knows that you
have available, and you say, yes, that's what I want.
I'm gonna make a chicken ala king, and you have
pushed the button, and then it could actually again if
it's part of this, this sort of network system could
send information to the oven so that the oven starts
to preheat to the correct temperature to make chicken ala king,
(48:53):
right while you are actually pulling the materials out so
that you can prep them for for cooking. So this way,
it ends up making the whole experience more of fishing
and could even potentially, uh, you know, send another note
out to your cell phone the next time that you're
in a shopping market and and say, hey, by the way,
you really like this one thing because you but you
made it like fourteen times in the last two months,
but maybe you want it again, or or maybe you're
(49:15):
out of chicken, uh, and we're planning on doing something
else later this week. Maybe you need to buy more chicken. Yeah,
it just tells you go out there and buy more chicken. Now.
The the thing that I find interesting is that we're
talking about this. These are kind of future applications. They're
really coming into practice now, uh, and we'll probably see
more of that in the next maybe five or ten years.
It's gonna take a while before this technology to to
(49:36):
get out there far enough for it to be pervasive.
Especially you know, once you buy a big appliance like
a refrigerator, you want that to last for a while,
not something you replace every couple of years, thirty year
kind of can it definitely can't be. So I think
this is one of those those things that we're gonna
see kind of played around with like high end homes
(49:56):
and that kind of stuff. I don't I don't imagine
I'll be buying a smart frigerator anytime the near future
unless I just when the lottery or something. I'm like,
I don't know what else to do with everyone, right,
like just knock on random doors, guess what you want today? Yeah,
I don't know otherwise, but it is interesting to me
because I sit there and I think about the time
(50:18):
back when people were like, well, we could buy a
mechanical refrigerator, but ice is so available, so who knows
what will happen? Um anyway, So that's that's how refrigerators work.
This was a particularly fun episode to kind of talk about.
We haven't done a how something works episode in this
kind of level for a while, and uh, and we
(50:39):
really do enjoy doing them. There they are challenging, so
but we we enjoy the challenge. So, guys, fans, you know,
I love you that you just had a moment with
the microphone. That was very that that was very sweet.
He was He meant it when he said that, everybody.
But yeah, So so if you have suggestions for episod
(51:00):
zodes of future text stuff, extravaganza type stuff. Let us
know you get in touch with us, send us an email,
Our addresses tech Stuff at Discovery dot com, or let
us know on Facebook. Our Twitter are handled there as
tech Stuff hs W. Also keep in mind episode five
hundred of tech Stuff is coming up very soon, so
(51:21):
if you have a suggestion that we need to cover
in that episode five, definitely let us know, and Lauren
and I will talk to you again really soon. For
more on this and thousands of other topics, visit how
stuff works dot com.
In text with Technology with text style from how Stuff,
what's that coming? Hey then, everyone, and welcome to tex Stuff.
I am Jonathan Strickland, one of the two hosts of
the show, and I'm Lauren vocal Bon, the other of
the two hosts of the show. And today we wanted
(00:23):
to talk about something that's pretty cool. Oh no, yeah,
already started. We're gonna talk about refrigerators. And and here's
the interesting thing, guys, if you listen to the episode
that Chris Pallette and I did quite some time ago
about air conditioners, this podcast is going to sound very
similar to that because the technology is used in air
(00:43):
conditioning systems and the technologies used in refrigerators are essentially
the same, just one is a more small and controlled
and um not for people usually, right, No, there's some
notable exceptions to that. We are not going to talk
about those, guys, because that's creepy and probably belongs in
another podcast. Okay, so we're not talking about people in
(01:06):
refrigerators today, although now I can't think of anything else. Um,
but no, no, no, First, let's start with what the
definition of refrigeration is. So it's defined as the process
of achieving and maintaining a temperature below that of the surroundings.
And the aim of it is to cool some sort
of space or object to a required temperature, right, because
(01:29):
bacteria grow most rapidly in this and it's it's called
the danger zone. Actually in between I now I have
a new thing filling up my head. But okay, yes
that I debatably better than than Archer really and so okay,
well excellent, but so yeah, the danger zone is in
between forty degrees fahrenheit and a hundred and forty degrees fahrenheit,
(01:52):
which is a four point four to sixty degrees celsius.
And and in that temperature range, bacteria really just groove out.
They can they can more than double in in twenty minutes.
That population just explodes. And and bacteria and for things
like you know, food stuff that that we would consume,
that's not necessarily a great mix. That can lead to
(02:14):
u some pretty nasty contamination. Uh, it can lead to
some really serious health problems. And uh, and this is
why refrigeration is such a big deal. I mean, clearly,
before we had any kind of refrigeration, we had to
look at different ways to preserve food. Otherwise you pretty
much had to get food from the source and consume
it right away, immediately or as close to immediately as possible.
(02:38):
Or you had to cook it so that it would yeah,
so it wouldn't spoil as quickly. Or you had to
salt it like crazy so that again the salting would
would inhibit the bacteria from from uh from reproducing so quickly.
And even in refrigeration, we still have that uh, that process.
It's just slowed down quite a bit, which is why
(02:58):
you cannot leave food in a refrigerator uh indefinitely. It
will eventually go bad. Um. And then just like in
that great Far Side cartoon, the potato salad will hold
up the catchup when potato salad goes bad. So the
trick here, though, is how do you create this cool environment?
(03:19):
This this cold environment? Because adding heat two things is easy.
Taking heat away not as easy, less easy. And also,
before I get all my physicist friends sending in messages
about the use of the word heat, I do apologize
we're going to be using it in the vernacular quite
(03:40):
a bit because that's really what everyone's familiar with. But
to be clear, an object does not possess heat. It
has a temperature, but it doesn't possess heat, and objecos
will have internal energy as a result of molecular motion.
And heat is really the description of an energy transfer process.
And uh, you go from a high temperature object to
(04:03):
a lower temperature one. That is the basic concept of heat.
It's really an energy transfer. So when we say, like,
this object's got a lot of heat to it, uh,
that's a that's a completely colloquial way by saying it.
So I do acknowledge that. I apologize. But if you
really want someone who's going to be a stickler for science,
(04:24):
go bug Robert Lamb because he loves that the stuff
to blow your mind. Gay, Um, Robert's awesome. I love Robert. So, yeah,
that's the way heat works. Though you have high temperature
low temperature, then heat moves from the high temperature to
the low temperature. It does not go the other way around,
right without without some sort of external force working on
(04:47):
the system. Uh. This is essentially one of the basic
laws of thermodynamics. And so you've got this, Uh, you've
got a way. You have to find a way of
creating a lower temperature or environment to pull heat from
or to for heat to transfer from the objects that
(05:08):
are inside a refrigerator to make them cool. So that's
the basis of refrigeration. But you know, to get to
that point, we had to do a lot of stuff
and we had to understand a lot about physics for
this to become what we now all kind of take
for granted. Yeah, So to to get started, I guess
(05:29):
we can talk about what the predecessor was to the
modern refrigerator, which was the ice box, right, or you know,
going going way back in time, you had you had
people not even making ice boxes, but yes, just collecting
ice and putting it next to stuff. Yeah, or like
maybe you know, you might have a seller that you'd
put ice into, or you might just have a hole
in the ground, or you may just like if you
(05:50):
were in a part of the world where there was
a significant amount of snowfall. Uh, we here in Georgia
are not in that part of the world. We did
have some know the other day, I could see a
bare trace of it next to my steps. Some of
it landed in my hair when I walked my dog.
That was that was about it. But if you were
in a place where they get a significant amount of
(06:11):
snow and they're large snow banks, then one of the
things you might do is store some food inside the snow.
They're bury it in the snow and just hope that
nothing comes along to to grab that food. Or Yeah,
if if you've got an ice house, you can preserve
some of the ice with a sawdust or wood shavings.
Later on, cork was used to insulate it for a
few months anyway, until temperatures warmed up enough. Right right, Yeah,
(06:34):
you could. You could definitely slow the process, insulated enough
from the heat of the outside environment so that it
would preserve you wouldn't lose too much in melt off.
It took a while before people started to figure out
the best ways to keep ice from from melting too quickly.
And it's interesting because just as they were really getting
getting very good and making sure they kept ice uh
(06:58):
cold for as long as pas well, even in hot environments. Uh,
that's when the mechanical refrigeration technology had started to really
take off and it became less important. And these were
happening simultaneously, which is really fascinating to me. It was
in seventive that the first refrigerating machine was produced. I
believe it could make small amounts of ice in the lab. Yeah, yeah,
(07:21):
to to really understand well, first of all, the word refrigerator,
I found the I found the earliest use of it,
which was or at least earliest recorded use that I
could find, which was from fifteen fifty. But it was
all about using chemicals in water. People were discovering that
if they added certain chemicals to water for some reason,
the temperature of the water would drop. So if you
were to put something in a container of water that
(07:43):
had this chemical in it, you could cool that's something. Now,
if that's something was unprotected food and that chemical was poisonous,
that was not necessarily a great thing. But if that's
something were I don't know, a bottle of wine and
you happen to be French, this was a great way
to cool your wine. And in fact, in the Renaissance,
these cooled drinks became very popular, to the point where
if you added chemicals to water, it would drop the
(08:06):
temperature enough that if you put something in it that
that you could turn on a regular basis, you could
actually make ice this way. Um. Yeah, So this was
kind of an early ice maker, not efficient, not good
for producing ice on any kind of large scale, but
it was one of those things that the rich people
really enjoyed, and really those were the only ones who
had any chance of getting at it. Um. But yeah,
(08:30):
it was just before your the refrigerator unit type thing
you were talking about from the seventeen seventies. Seventeen fifty
five is pretty much when we talk about the origin
of the idea. That's when William Cullen made his machine
with which you used a vacuum UH and UH ether
(08:51):
to UH to create this UH environment where he would
put water into a container, put a smaller amount of
ether in there, put a essentially a vacuum bell jar
on top, you know, with a pump on it. By
creating the vacuum, the ether would start to boil off.
(09:11):
And when the ether was boiling off, when it was vaporizing,
he noticed that the temperature was going down in the
water and in fact, but when the ether would continue
to boil off, the water would start to turn into ice.
Now we'll talk about why that is a little bit later,
but this was one of those early observations that started
to lead people into thinking, you know, if we harness
(09:34):
this in some way, pretty cool. Yeah, there's no way
to avoid it. Voco boumb Join us together, we will
rule the galaxy. Jonathan. We need to we need to
chill out, Yes we do. Okay, all right, now too fast,
too fast. You gotta gotta pace yourself here. Um. So anyway,
(09:56):
this does form the basis. This, this idea of UH
vapor pulling out heat somehow, that is what was the
very basis of mechanical refrigeration. It would be quite a
while before the mechanical refrigerators would start to become a
real thing. Uh, I have a in eighteen o three,
you have a Thomas Moore obviously not that one different
(10:20):
Thomas Moore UH of Maryland. In fact, he received a U. S.
Patent for a refrigerator. Now this was not the same
thing as the mechanical refrigerators that would come later. But
that same year that was when the domestic ice box
was invented. So three you get the domestic ice box.
This was usually a wooden cabinet that you would put
(10:41):
a block of a large block of ice into the
top and then you would keep your food and and
and consumables in the bottom part of this cabinet, and
convection would essentially keep because because heat rises and cold sinks,
that which is which we know is the generalization was generalization, yes,
(11:01):
but but in general in this particular case, yeah, you've
got you've got the dense the dense cold air going
down and the and the less dense warm air moving up.
Because yeah, but we we understand that is a gross
over generalization. But for the purposes of this podcast, it's
effective enough. Yeah, you kept that ice on top. You
have a like a drip tray on underneath, because hey,
(11:22):
that ice is melting um, and so you would collect
the water which you would not just pour into the
top where it would magically become ice again. Essentially, once
that ice was gone, you had to go out and
buy more ice. And actually the ice trade was really
huge right around that time. In eighteen o six, I
think Frederick Tudor began his his ice empire. He was
called the Ice King. Yeah, um, when he started cutting
(11:45):
chunks out of the Hudson River in various ponds around
Massachusetts and then exporting it as far as China and Australia.
In India India. Yeah. Also what's interesting is that India
was the way the way they were producing ice in
India at this time was through a process called nocturnal
radiative cooling. Right, I was reading about this this it
(12:05):
took me a while to grasp how that work. I
still did not understand it. So, I mean what I
w I understand that basically they were doing was putting
water in shallow clay trays and setting it outside under
the open sky overnight and then in the morning ice
would be there. Yeah, what what essentially is happening is
that the uh, it's there is another physical process going
(12:27):
on here. But you've got you've got a tray of
water outside. The sky needs to be clear because what's
happening is the heat is radiating from the water out
into the atmosphere and escaping that way. Now, if there
are clouds, then the heat can radiate back down too,
because it's like an insulator. It'll it'll end up insulating
the earth and you end up you don't get enough. Right.
(12:53):
But otherwise, even if the the ambient temperature outside is
still right around freezing or just above freezing, you can
still freeze water that way. Under a clear sky also
helps if it's a very dry climate. Right, And and
from what I understand that it's important that it's a
it's an earthenware tray because that way you get some
of the uh, well, you have to have that insulated
(13:15):
effect there as well. It's the earthen tray and there's
usually hay underneath it, Yeah, some kind of compressed Yeah.
So it's it's interesting that that was the way that
India was producing ice, but that was not a very
again and a very efficient way of producing ice. You
couldn't produce a lot of it, and uh there was
a big demand. So Tutor was really raking it in
(13:36):
by harvesting ice in the United States, just natural ice.
Not he's not producing it in any mechanical means. He's
actually going out and digging it up, packing it in
wood shavings and that sort of stuff, cork, that kind
of thing, shipping it to the other side of the world,
and making huge bank off of it, huge bank. And
I want to mention that also right around this time,
(13:56):
in UH seven, ammonia was first liquefied in a laboratory, right,
which will becoming point um, So just keep that in
your heads for a second. And um. And then also
in eighteen o five, right before Tutor began his big
ice trade, UM, Oliver Evans described did not create but
described a closed at their vacuum refrigeration system. Yeah. So
(14:17):
this is the same sort of of mechanical system that
would eventually become what we use in refrigerators, most refrigerators,
I'm saying refrigerators in general, but there are different types. Yeah, well,
we'll mention a few, but but the we're focusing on
what most of us have available in like in our kitchens, uh,
(14:39):
and maybe our basement if Okay, I'm not going to
go back there. It's dark base to a dark placed
voco bomb really early on, I'm very fond of that
of that documentary American Psychos. Okay, that's fair. In eighteen twenty, Uh,
this is interesting that the Michael Faraday was working again
(15:00):
with liquid ammonia, and that's when he started realizing that
liquid ammonia, which ammonia is naturally at room temperature, is
a gas, right because it boils it at like negative
twenty seven degrees fahrenheits. So, so to to liquefy it,
you have to compress it, you have to pressurize it
to make it a liquid. And he realized that when
(15:20):
it went from liquid back to gas, it caused cooling
and so again another important part of this mechanical refrigeration. Now,
in one a German physicist by the name T. J.
Cbeck discovered that if you have two junctions of dissimilar
metals kept at two different temperatures, it induces electromotive force
(15:44):
or electric currents. So what that means is that, let's
say that you have a junction of a copper wire
and an iron wire, all right, and then you have
a second junction where the iron wire is attached to
a second copper wire. And let's say you were to
heat up that, uh, that first junction and cool down
the second junction, perhaps put some ice on it, you
(16:05):
would actually induce electricity to flow through that wire. Now
that's important because in eighteen thirty four, uh Peltier discovers
that if you do the opposite, if you put electricity
through a series of wires that have these kind of junctions,
one side will heat up and the other side will
cool down exactly and then by up to I think
(16:25):
forty degrees fahrenheit. It all depends on what kind of
material material you're using. Uh. In fact, this sort of
is called the Peltier effect. Actually, but this sort of
effect is dependent upon the types of metals or or
materials you're using and uh, their purity. If you're using
pure metals, the effect is is pretty small, so small
(16:47):
as to not be very useful. It's interesting in the
laboratory setting, but not terribly useful. Also, if you're using
pure metals, they tend to be very good thermal conductors,
which means that that that difference in temperature will not
mean taine itself for very long. You will eventually have
the the heat will move from the high temperature to
the low temperature and balance that out. Uh. Meanwhile, if
(17:10):
you were to use an insulator, then you wouldn't get
the effect, So it would take years before anyone would
find a way to make that useful. But that is
used that That same technique is used in some electric
little portable refrigerators, things like the kind of stuff you
might plug into your your car outlet. Yeah, basically, you
(17:31):
just get a whole bunch of these junctions set up.
You put the hot ones outside the unit, the cool
ones inside the unit. Fridge. Yep, that's exactly it. So
so spoiler alert, that's how that one works. But we
thought if i'd be interesting to talk about that. But
that's that was what caused was the basis of that
sort of refrigerator. UM. And that same year, in thirty four,
Jacob Perkins developed a vapor compression cycle refrigerator using ether.
(17:55):
So you got a lot of people working on patent
for it. Happened that year m H and UH eighteen
forty four you had John Gory proposing an air cycle
refrigerating machine for making ice. UH. Eighteen fifty you had
Rudolph Clauseus who said heat can never pass from a
colder to a warmer body without some other change connected
(18:15):
there with occurring at the same time. This is what
I was talking about at the top of the podcast.
It's kind of a rewording of the second law of thermodynamics.
It's related to that. So UH, that's one of the
the principles that guided refrigeration as well. UH. In eighteen
fifty one, our buddy John Gory from back when he
had proposed that air cycle refrigerating refrigeration machine to to
(18:38):
create ice. In eighteen fifty one, that's when he got
the another patent for mechanical refrigeration. And in eighteen fifty
five Alexander Twining starts his first commercial ice making plant
using vapor compression refrigeration. We'll explain what that is in
more detail in a little bit. Eighteen fifty six, commercial
refrigeration begins in industries like brewing and meat packing. Now,
(19:01):
commercial refrigeration did not necessarily mean they were using mechanical refrigeration.
They could be using natural refrigeration, as in going out
and buying lots and lots of money and packing stuff. Um.
It's interesting to me that brewing picked up on this
really quickly, like like the brewing companies were like, we
want beer that tastes good. It's as though alcohol technology
is something that drives industry in some way. Yeah. Meat
(19:24):
the meat packers were slower to follow suit, which is disturbing.
Spoiled meat was something everyone was used to write and
if you're drunk enough, you don't care. Okay, got it.
I understand now. As someone who does not imbube alcohol,
it was just completely foreign to me. But I don't
eat meat either, so what do I care? Um. Also,
we're no longer in the eighteen fifties, as it turns out.
(19:46):
But yeah, meat packing was slow to adopt this technology,
but it did start it back in the eighteen fifties,
and the majority of plants wouldn't switch to mechanical refrigeration
until about nineteen fourteen, and by then you were getting
into a really like a booming time of refrigeration. But
backtracking just touch in. In eighteen fifty nine we had
a Ferdinand car of France who developed an ammonious slash
(20:10):
water refrigeration machine. Eighteen sixty eight you had Peter van
der Wide. Uh. He patents thermostatically controlled refrigeration systems. That's
going to be important when we get to the modern refrigerator.
Eighteen seventy Carl Lynn publishes a paper called the Extraction
of Heat at Low Temperature by Mechanical Means, and he
designs the first practical portable compressor refrigeration machine in eighteen
(20:33):
seventy three. Uh. In eighteen seventy seven, that was the
peak of the ice trade, so in the US that
it hit its peak right And the late eighteen seventies
the United States was exporting almost almost a quarter of
a million tons of ice to other countries. So uh, yeah,
(20:54):
a lot of ice leaving the United States. Um and uh,
it's interesting to me that at this point where the
ice trade is at its peak, but mechanical refrigeration is
already in its infancy. The only reason that mechanical refrigeration
even started to take off, it wasn't because the technology
(21:15):
was getting great. It's because the ice trade was starting
to encounter problems. Once it gets to about the eight
nineties or so, like, if the ice trade had not
encountered problems, then even with the technological advances in mechanical refrigeration,
we may not have seen refrigerators in the United States
(21:36):
for another you know, I don't know four or five decades,
but so, yeah, and that what happened was was that
as people were essentially mining ice, you know, cutting away
ice from these rivers and ponds, they were starting to
uh exhaust the clean sources of water and so more
(22:01):
and more of the ice. The demand was growing, right,
and the supply was diminishing. Not that we were running
out of lakes and rivers and stuff. It's just the
demand was so great that there wasn't enough to go around. Yeah,
there's not there's only that are frozen, and the Hudson
is really big and stuff. But yeah, I mean when
you're talking about a quarter of a million tons, right,
so you're talking about tons of ice that might have
(22:23):
things like sewage in Uh, not so great when you're
using it in the meat packing industry as it not
maybe not such a big advantage over spoiled meat. Um yeah, so. Uh.
It's because the ice industry was starting to have these
issues that we began to see the rise of mechanical refrigeration.
(22:45):
Was when a trade journal called Ice and Refrigeration began
to publish. Nineteen o four was when the American Society
of Refrigerating Engineers was founded. By the way, the American
Society of Refrigerating Engineers, I learned, was about engineers who
were experts in refrigeration. It was not a society that
would actually refrigerate engineers. Because the way it was worded
(23:07):
it was confusing. I find that difficult to believe, Jonathan.
I think you should check your sources. American Society of
Refrigerating Engineer. It does sound like you're just shoving a
guy with a hard hat into a fridge, and that
brings us back to American Psycho. Nineteen eleven, General Electric
introduced the first domestic refrigerator. Depending upon whom you ask, right,
(23:27):
we should also point out that when we've got these
dates and saying who brought out the first one, etcetera, etcetera. Uh,
there's some dispute in them, and it all, like I've
seen conflicting time. The history and especially uh scientific incorporate
history tends to be written by the victors and um.
So therefore sometimes you know, you have in different reports
(23:48):
differ about exactly who won that right and you know
exactly n according to some sources, that's the first electric refrigerator.
According to actually frigid Air's timeline tell you specifically, nineteen
sixteen was when models like the Kelvinator and Servel were introduced,
and in nineteen eighteen General Motors purchased Guardian Refrigerator Company
(24:10):
and renamed it Frigidair. So nineteen eighteen was when frigid
Air as a thing became a thing like it existed before,
but it didn't exist in like, it didn't have the
frigida name. And frigid is where we get the word
fridge from. I do believe, I believe so. And it's
also they that's the company that developed free on, which
we will talk about a little bit in just a moment. Yeah, yeah,
(24:30):
so way up in the nineteen thirties, we've got like
one other point to cover before then I've got I've
got a couple more. Actually, because i've got I've got three.
In the twenties, here we go, Oh goodness. In the
USA there were about twenty five million domestic refrigerators, only
seventy thousand of which were mechanical. So these refrigerators, some
of them were more like the ice box refrigerator. Um.
(24:52):
I remember, I remember watching like Lassie growing up, that
that the mom and Lassie had an icebox, not not
a fridge. Random mom in the last Sie, not the
mom and Lassie. From all I thought, Lastie had its
own fridge, and like that dog was luckier than I was.
Seven was the first porcelain on steel cabinet refrigerator, which
is that's the one I always think of, like the
(25:13):
nineteen fifties refrigerator, the big porcelain ones. It looks a
little bit like a rocket. Yeah mine, mind is mind's
a steel refrigerator. I've got the sameless steel thing going now. So,
but I don't I remember the one, the porcelain ones. Uh.
THEE was when Frigidair introduced the first home food freezer,
and it was a chest style freezer, so you know,
not the not the upright type, not not incorporated into
(25:36):
a refrigerator. Um. And that was right around that time
is when uh, Frigida starts to introduce chloro floral Carbon's right,
I believe that DuPont had developed it's also called a
free on. Yeah, that's the patented specific lora flora carbon
that Frigida introduced. Um. And yeah, before then, UM, some
(25:57):
of the very early fridges I believe, were you using
sulfur dioxide, Yeah, sulfur dioxide, methyl chloride, ammonium. Yeah. And
these are all chemicals that are toxic, toxic, so whenever
there were accidents, and you know where human accidents happened, uh,
then uh, sometimes people were really badly injured or even
they died even as a result of being exposed to
(26:20):
these sort of chemicals. And so there was a big
incentive for companies to develop refrigerants that were not toxic.
And so that was the reason why companies were looking
into something like a chloral fluora carbon. Now, later on
we would learn other downsides to chloro fluora carbons, which
we'll talk about in a second, um, which is why
(26:40):
we don't use them anymore. Now. In nineteen thirty one,
that was the first use of free on as a refrigerant,
So it was kind of introduced in nineteen twenty nine,
and by it was being incorporated into the design and
mechanical refrigerators. In the first refrigerator freezer combo with the
freezer having its own separate section was introduced, so you
(27:01):
that was where you know, you would open up the
fridge part or you would open up the freezer part. Um.
And in nineteen nine, Soviet engineers discovered a way to
create thermoelectric refrigeration systems using the the Peltier effect by
using semiconductor material because you know, like I said, those
pure metals weren't producing enough of an effect for it
(27:21):
to be useful in any way. They found that by
using semiconductor materials they could create a temperature differential that
was effective enough for it to be used for something science.
So yeah, they actually started creating refrigerators using that thermoelectric
system rather than the vapor compression system that was being
used pretty much everywhere else. Also in in ninety nine,
(27:43):
the business was so booming that seven million refrigerators were
being produced in the US annually. Nice and in fact,
my timeline ends at nineteen nine, because I didn't write
down specifically the bit about the nineteen seventies where right
around nineteen sent was when we started figuring out the
chloral fluora carbon we're starting to accumulate in the atmosphere, Yeah,
and eat through the ozone layer, which is not the
(28:04):
science for that, that's right, right, but that it was
it was in fact harming the ozone layer, and that
was what gave the incentive for us to develop something
besides that, which is why these days hydrofloor carbons or
isoputane or yeah, those are the those are the main
too uh to be used because they don't have the
same environmental impact nor that they have the same toxicity
(28:28):
levels as the previous refrigerants before free on. Yeah, ammonia
and things are still used in industrial capacity because they
assume that someone who has you know, um, five thousand
dollars to drop on a refrigerator is going to or
five thousand dollars more on top of what you would
normally spend, is going to take a little bit better
care with the care of it and not you know,
let the dog eat through the back end. It's it's
(28:48):
it's one of those things. Also where you're talking about
efficiency as well. Ammonia is a very efficient refrigerants. So
that's that's you know, when you're talking about a large
scale production, efficiency ends up being the difference between a
profitable year and a disaster. Yeah, especially when you've got
health inspectors coming through making sure that you do not
have any food that is entering that danger zone that
I talked about. Right, So that that kind of brings
(29:11):
us up to speed to the general refrigerator of today.
Let's take a quick break to thank our sponsor. Okay,
so I think it's time we start talking about the
actual process of refrigeration and how the modern day refrigerator
in general works. Do you mean the technology of it,
like we're like we're at tech as if we were
(29:32):
talking about the stuff that is techy. So, so you're
using essentially the refrigerator cooling system is a closed system, right,
It's a closed system. Think of it as a series
of tubes, so it's its own Internet, but a series
of tubes that are all connected to one another. There
(29:53):
there's no external you know, venting or anything or intake.
So you've got a system where you're using a refrigerant
Like we were talking about in those early days. Yes,
some sort of some some sort of of material that
at room temperature is a gas. But when you pressurize it,
(30:13):
you can make it a liquid. And that's the key.
So Um, if you if you're having trouble understanding how
this works, think about like you get some rubbing alcohol
and put a little bit on your skin, and you're
gonna feel that it it feels very cool. And that's
not because the rubbing alcohol itself is at a cool temperature. Yeah,
(30:33):
that the liquid in the bottle, when you hold the bottle,
it can feel like it's the simply of the same
temperature as the room. Right. But but the thing is
that rubbing alcohol will start to evaporate at room temperature.
So when you put it on your skin, as it evaporates,
you're gonna feel your skin cool down. That evaporative effect,
it's as the the liquid is turning into a vapor,
it's pulling heat. Uh through part of that physical reaction,
(30:57):
and the reaction the energy that is required to turn
something from a liquid to a vapor. UM sucks in
energy heat energy from right around and you've got the
higher temperature generated by your body. So that's where that
heat can come from it can pull the heat from
there to help fuel this reaction. Essentially, again we're kind
(31:18):
of oversimplifying, but yeah, but we're also not not physicists,
and so we also don't have visual effects to show
you what we mean, which makes aside from our own gesticulation,
which is really only benefiting us. Yes, we can. We
can also do the safety dance in here. Apparently that's
that's what looks like whenever I start talking, Um, that's
just the way I am. But okay, So you've got
(31:39):
the coolant in your refrigerator, which is called a refrigerant.
The coolant moves through a series of coils and through
different parts of the system that the coolant is either
going to be in a liquid state or a gas state.
Now you have to think of this system in its
various parts so on. It's kind of hard to say
(32:00):
on one end of the system because really, in a way,
this is kind of like a big circle, So you
don't have a start and an end. Really, I think
it's easy to start with that with the compressor compressor.
So I've got a compressor. The compressor is, of course
does what it sounds like. It does It compresses compresses
the gas. So it's uh, well, it compresses the cooling
at the at the time. Yes, it's a gas, it's
(32:23):
compressing it. So it's coming in through Uh, it's pulling
in gas and compressing it. Now, remember we said that
heat is not a thing that an object possesses. Instead,
an object possesses some sort of internal energy. So if
you were to pressurize something like a gas, If you
were to pressurize a gas, uh, or you were to
(32:45):
heat up that gas, you would increase the molecular movement
there and just from being just from observing the gas itself,
without having any knowledge of how it got that way,
you would be unable to tell whether it a cheat,
its internal motion through heat, pressurization, or some combination between
the two. They would be indistinguishing. Look the same, right,
(33:07):
So essentially what I'm saying is that compression and heat
gets you the same result. So you are compressing this
gas and as a result, the temperature of that gas
up all right, So you then create this long series
of coils. This is on the outside of the fridge.
(33:29):
The compressor is right ready to edge of the fridge.
It it draws the air in it draws the gas, right, sorry,
draws the gas from the fridge out to the outside,
compresses it and then yeah, and then it proceeds up
through the series of coils coils. Yeah. And you keep
in mind, like I said, this is totally a closed system.
This this gas is not exposed to the interior of
(33:50):
your refrigerator. There's it's always in in tubes essentially, it's
always in pipes. So it's going through after it gets compressed,
it's heat heats up. It doesn't it isn't heated up.
It heats up through the compression. Uh, and then it
goes through this series of coils. As it goes through
the series of coils and the outside the refrigerator, it
starts to lose some of that it you know, the
(34:12):
heat moves from the coils to the surrounding atmosphere. Right.
That that that is the purpose of these coils to
to cool down this air to the point that it's
going to gas. Okay, I just don't want it to
be too too vague, but yes, yes, exactly, it's it's
cooling down the gaseous coolant, right because because at this
(34:35):
point that that compressed gas is at a higher temperature
than the ambient air around it. So if you were
to touch one of these coils, you would feel it
was very hot. We don't necessarily recommend doing no, don't
do it. And this also shows that the refrigerator is
only going to work if it's in an environment that
is cooler than what the coils are. Like if if
(34:56):
for some reason you put a refrigerator in the middle
of a volcano then they degrees, it probably wouldn't do
well because because then you have the temperature of the
surrounding environment is higher than the temperature of the coils,
the heat transfer would move in the opposite direction. Gas
would never cool down. So so clearly you have to
have a cooler temperature in your environment. In this case,
(35:18):
it's in your kitchen, and your kitchen, while even when
you're cooking full blast feels like it gets pretty warm,
is nowhere near as hot as those those coils are. First,
when the gas is compressed, so as it moves through UH,
it starts to cool down and it begins to condense
and under that compression, under that pressure, this condensed cooler
(35:39):
gas becomes a liquid. Because as you increase the pressure
on a liquid, you also increase its boiling point. So
if you were to take a uh, let's let's take water. Okay,
So water boils at two and twelve degrees fahrenheit or
one hundred degrees celsius, So much easier to talk in
terms of celsius. Although I'm totally I'm so used to
(36:03):
everything else being in fahrenheit that water is the only
thing that makes sense to me in celsius. So, but
that's because I'm an ignorant American, alright, So uh and
I'm not saying all Americans are ignorant. I'm saying I
am so. Anyway, Um, So, at a hundred degrees celsius,
that's normally when water would boil, right of water under
one atmosphere of pressure. If you were to increase the
(36:24):
pressure on that pot of water, Let's say, let's say
we somehow put a pressure cooker around this, this pressure
canister around this pot of water and increase the pressure
on that water. That would also increase the boiling point.
So you would actually have to go over a hundred
degrees celsius in order to get that water to boil.
The same sort of idea here, you've got this compressed gas,
you've got condensed down into a liquid. That means the
(36:46):
boiling point has gone up. So as long as that
that liquid is under pressure, the boiling point is higher
than it normally would be. That's why it can be
a liquid. All right. So you've got this liquid it
would normally be a gas at this temperature. How do
you make this liquid suddenly magically make everything cool again? Well,
you've got to have a valve, an expansion valve Jule
(37:09):
Thompson or our Juel Kelvin, depending on on how how
you want to say. Uh, Lord Kelvin, Lord Kelvin, Yes,
came up with this with this ingenious little valve concept
where if you have a high pressure liquid on one
side and a very tiny hole and a low pressure
area on the other side, stuff happens. Right. What happens
(37:30):
is that liquid will pass through that expansion valve once
it gets to the area of low pressure. Now you
don't have the pressure on there anymore. Once the pressure
is gone, that boiling point goes back down to where
it normally would be. Now again, with the refrigerants you're
using in the refrigerator, that boiling point is way lower
than room temperature. Yeah, yeah, negative twenty eight degrees fahrenheit
or negative thirty three degrees celsius. So that's when this
(37:53):
liquid would normally boil off into a gas. Okay, here's
the other the cool thing about boiling points. Let's say
that you are magically inside an oven. Don't ask me
why you went in there, but you're okay, for some
of you, you're very heat resistant. Okay. Now you've got
you have that pot of water from the pressure experiment earlier,
(38:13):
because you don't like to waste, right, so especially not water.
It's a it's a precious resource. So you've you've taken
that pot of water with you into the oven, and
you're watching the water and the temperature inside the oven
is four hundred degrees and you're watching the water boil,
and you you have a thermometer inside the water. It
doesn't have any contact with the metal or anything. It's
just measuring the temperature of the water. The temperature of
(38:34):
the water. Even though the oven is four hundred degrees temperature,
the water is still going to be assuming regular pressure
two twelve degrees fahrenheit one degrees celsius, because that water
cannot physically cannot go above that temperature. Not not a
liquid form, no because as when you're in liquid form,
you can go only up as high as the boiling
point and then you turn into again. So so the
(38:56):
water itself is at one hundred degrees celsius so to you,
because you know you're in the four hundred degree air,
to you, the water would actually seem cold, right. So
that's the whole idea is that once it goes down
to this boiling point, the temperature actually drops dramatically. So
it goes through the expansion valve. The liquid, the highly
pressurized liquid, goes through this expansion valve, hits the area
(39:18):
of low pressure, immediately boils off and because most of it,
from what I've read about half of it boils off. Well, yeah,
because again you're getting into this low pressure system, which
means that now that that uh that it's no longer
confined by the high pressure, which means now it can
it can boil off into its vapor form, which means
that it starts pulling in the heat to essentially be
(39:43):
part of this uh this uh this process. Yeah. Yeah,
as as the process happens, it pulls in heat necessarily
because that is where the energy for the process comes from.
So what what that means for your refrigerator. Is that
the interior of your refrigerator, all the heat that's contained
within the interior brigerator moves to these sucked into the pipes. Yeah.
So that the same series, the same source series of
(40:05):
coils that you would find on the outside of refrigerator,
something similar to that is on the inside of your refrigerator,
only there, instead of putting heat out, it's pulling heat in.
Because it's pulling heat in from the interior of your
your refrigerator and freezer. There's just there's really just more
length of it and your freezer than there is in
your refrigerator. That's the difference there. Yeah, so so so yeah,
(40:28):
this liquid, this half liquid half gas, is running through
the coils inside the body of the fridge, and fans
are blowing air across the coils through the food part
of the fridge, which which continues to to vaporize the
rest of the liquid into gas and continues to pull
more heat, more heat. Yep. And that's what makes the
refrigerator cold. So really it's not that it's not that
(40:50):
the refrigerators pushing cold in, it's pulling heat out. So
that's something because I mean, which is so cool Yeah,
when you open up refrigerator and you feel that little
blast of cold air, you just think, oh, there's something
magically Yeah, that's not what's happening. So but it is
really neat to think about that that's all going on
at the same time. So you're really you're talking about
too closed systems. The closed system of the interior of
(41:12):
the refrigerator where all your food is, and the closed
system of the actual coolant that's moving through And um, yeah,
that's that's the basic idea. Oh and once it gets
once the gas gets to the end of that part
of the cycle, you know it's it's completely in gas form,
it's no longer pressurized. That's when the compressor pulls that
gas through to move it all the way through the
system again. So it's reusing the same coolant over and
(41:35):
over and over again with with no waste. Right, assuming
there are no leaks in the system, you're good to go.
If you've ever had to have a refrigerator or freezer unit,
if you had to have coolant added to it, this
happens frequently I've seen with air conditioning systems, uh climate systems.
Then that means there's probably there has to be a
leak somewhere in there because it is a closed system,
(41:56):
and otherwise you shouldn't really have any loss, at least
not any appreciable loss. Yeah. So that's the basic way
of fridge works. I find it super interesting. I almost
said cool, I almost did it. I almost said I
didn't want to do that. I think, did I do
that a second ago? I apologize. I apologize for accidental
puns guys, But uh, you might be wondering, Okay, well,
(42:19):
my refrigerator allows me to set a temperature, right like
I can choose to either go super cold. Yeah, for
for my freezer, I wanted to be as cold as possible.
Or you might think, well, no, that's gonna use up
a lot of energy. I'm gonna be a little When
when when the stuff in your cheese rawery starting to
frost over and you start going like, yeah, this is bad.
(42:40):
So what what governs that is what's called a thermo couple,
which is essentially a thermometer and a switch. So the
thermometer detects the temperature the interior of the refrigerator, and
when it drops below whatever the temperature is set to,
it turns off electricity to the compressor, so the compressor stops,
which means this whole cycle that we've been talking about stops,
(43:03):
and then if the temperature creeps up above it again,
it turns electricity back on. Yeah. So that's when if
you've ever heard your refrigerator just kind of kick on,
that's what's going on in you know. The more modern
ones do this really efficiently, so you don't have it
happen as frequently or as dramatically. I remember an old
refrigerator I had where you thought that, you know, perhaps
Steven Spielberg was filming Poltergeist for in your kitchen every
(43:26):
time I kicked in. Yeah. Modern fridges also do contain small,
low wattage heaters which just keeps the evaporator coils at
the correct temperature and not frosted over um, which which
I find also fascinating. Just yeah, like like fridges contain heaters,
that's the thing that they do. Yeah, And you know,
obviously refrigerators can have lots of other bells and whistles
on them. Of course. Sometimes literally, my my refrigerator does ding,
(43:49):
uh if I like, if I am using the there
has a water dispenser, right, so it intakes water from
my my house's water system and puts it through a filter,
and then I can get a nice clean glass of water.
But if you open up a the other door, it's
a it's a double door refrigerator. Do you open up
the other door, it cuts the water off. You can't.
(44:10):
You can't dispense water while the door is open, and
if you have depressed the water dispenser, it will bring
at you and mercilessly chide you for trying to do
two things that are not compatible. Because I frequently forget
while I'm getting a glass of water. I'm thinking, you
know what would go great with this water, That enormous
hunk of cheese that's in my refrigerator, and then my
(44:32):
refrigerator tells me that, yes, indeed, that would be lovely.
But you need to wait until you've either gotten the
cheese or finished getting your glass of water. You cannot
do both at the same time. That's great. I love
it with electronics. Chide man. By love, I mean hate,
I hate that thing well. And there are other kind
of interesting like additions you can get. LG has a
beer chiller. That's so, this is this thing. I actually
(44:55):
got to see this in person at the one like
the innovator or yes, it did. It did. It won
one of the Innovation awards. Uh and uh so this
is like a tiny little thing chamber within the refrigerator
part itself. It's called a blast chiller. Yeah, it's designed
it's designed to take a well, the demo was a
(45:17):
can of beer from room temperature to ice cold within
about five minutes. And uh and essentially it's doing the
same process we talked about right here. It's just that
I imagine there are more of those coils. It's a
very small chamber and very controlled. Yeah, there's their fans involved.
I mean, it's it's they're they're they're trying to increase
the circulation of air and the h and the surface
(45:40):
area that the cold coils have so that it pulls
heat as efficiently as possible, so that you can have
your frosty beverage when you want it, or at least
five minutes after you thought about it. Um. And that's
assuming you want one can. If you want to, it's
gonna take about eight minutes because it's more for it
to more heat for it to disperse. Um. But yeah,
(46:01):
there's there's stuff like that, and then they're smart refrigerators. Right, Yeah,
now you can you can have your fridge tell you
what's in it and what kind of recipes you can
make with that, and yeah, and send information to other
elements in your home, assuming that they are made by
the same company and are compatible, are willing to talk
to each other. Yeah. So the the idea here, of course,
(46:21):
is that it's not a new idea. It's one of
those things that people have been trying various to implement
in various ways. But now that we have smartphones, it's
a little bit it's a little easier, Yeah, because you
can you can connect a smartphone to a refrigerator and
scan things in that way. That was that was the
big issue, right, was that how do you tell a
refrigerator what's inside of it? If you have to stay
in there and manually input onto probably a really miserable
(46:44):
touch pad on the refrigerators surface, exactly like how many
bananas you have? I don't. I never want to do that.
I don't put bananas in the refrigerator. I do not. Thinking. Okay, well,
Foco bomb, I've found your problem. Uh no, but you
are you are correct that that's that's the barrier, right,
How do you make it so easy. And you know,
there were people who are talking about, why don't you
(47:05):
put r F I D chips and or strips of
some sort onto various products and then you could just
have it scanned when you put it in. But then
other people were saying, wait, if you have r F
I D chips, you can end up tracking everything that
someone buys, whether they want to be part of a customer,
you know, or not. Yeah, and there are people who
are very sensitive about that, and I can completely understand.
(47:27):
You know, I personally I don't worry about it that much,
but that's just because that's who I am. I'm waiting
to do it so that I can get sent yogurt coupon, right,
you know. But but I'm I totally understand the people
who are like, no one has any business knowing what
I buy. I go out and I buy it. I
buy it with my money. It's my exchange. That's all that.
That's where it should end. And I totally respect that.
(47:50):
But so that that the r F I D thing
never really I mean, I've seen some implementations of it,
but I don't expect that off the ground. Yeah, because
it would also require the entire food industry to change, right,
all the packaging would have to change. And that's when
you look at that across every single company that makes
food that's designed to go into a refrigerator. That's a
(48:10):
lot of money that that would require billions of dollars
of investment from various companies. Yeah, for for relatively low
usage point, I think, yeah, especially right now because we're
talking about you know, right now, I don't think there
are that many people who have smart refrigerators, and again,
like to get one that's really useful that can work
with something else. Like say you're your oven so that
(48:30):
you know, you pull up a recipe on your refrigerator
and it's it's telling you what you can make based
upon the ingredients that you that it knows that you
have available, and you say, yes, that's what I want.
I'm gonna make a chicken ala king, and you have
pushed the button, and then it could actually again if
it's part of this, this sort of network system could
send information to the oven so that the oven starts
to preheat to the correct temperature to make chicken ala king,
(48:53):
right while you are actually pulling the materials out so
that you can prep them for for cooking. So this way,
it ends up making the whole experience more of fishing
and could even potentially, uh, you know, send another note
out to your cell phone the next time that you're
in a shopping market and and say, hey, by the way,
you really like this one thing because you but you
made it like fourteen times in the last two months,
but maybe you want it again, or or maybe you're
(49:15):
out of chicken, uh, and we're planning on doing something
else later this week. Maybe you need to buy more chicken. Yeah,
it just tells you go out there and buy more chicken. Now.
The the thing that I find interesting is that we're
talking about this. These are kind of future applications. They're
really coming into practice now, uh, and we'll probably see
more of that in the next maybe five or ten years.
It's gonna take a while before this technology to to
(49:36):
get out there far enough for it to be pervasive.
Especially you know, once you buy a big appliance like
a refrigerator, you want that to last for a while,
not something you replace every couple of years, thirty year
kind of can it definitely can't be. So I think
this is one of those those things that we're gonna
see kind of played around with like high end homes
(49:56):
and that kind of stuff. I don't I don't imagine
I'll be buying a smart frigerator anytime the near future
unless I just when the lottery or something. I'm like,
I don't know what else to do with everyone, right,
like just knock on random doors, guess what you want today? Yeah,
I don't know otherwise, but it is interesting to me
because I sit there and I think about the time
(50:18):
back when people were like, well, we could buy a
mechanical refrigerator, but ice is so available, so who knows
what will happen? Um anyway, So that's that's how refrigerators work.
This was a particularly fun episode to kind of talk about.
We haven't done a how something works episode in this
kind of level for a while, and uh, and we
(50:39):
really do enjoy doing them. There they are challenging, so
but we we enjoy the challenge. So, guys, fans, you know,
I love you that you just had a moment with
the microphone. That was very that that was very sweet.
He was He meant it when he said that, everybody.
But yeah, So so if you have suggestions for episod
(51:00):
zodes of future text stuff, extravaganza type stuff. Let us
know you get in touch with us, send us an email,
Our addresses tech Stuff at Discovery dot com, or let
us know on Facebook. Our Twitter are handled there as
tech Stuff hs W. Also keep in mind episode five
hundred of tech Stuff is coming up very soon, so
(51:21):
if you have a suggestion that we need to cover
in that episode five, definitely let us know, and Lauren
and I will talk to you again really soon. For
more on this and thousands of other topics, visit how
stuff works dot com.
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