This ever happen to you? You open up the refrigerator, and you touch something that feels kinda warm
or maybe even kinda hot. Maybe this gasket around the rim of the door. And you think:
What the heck? I thought refrigerators were supposed to make cold, not heat.
Fact is, this appliance actually contains some heaters in addition to its coolers. That
apparent self-defeating contradiction is not a Sisyphean exercise in futility devised as
a cruel philosophical joke by nihilistic engineers.
It's actually just one of several brilliant pieces of engineering that have made these
ubiquitous boxes utterly transformative forces in our lives.
Life is so different now than it was just a hundred years ago because of these things.
The basic physics phenomenon that makes it cold in here has been known to humanity for
thousands of years, and that is evaporative cooling.
It takes a lot of energy — heat energy — to transform a liquid into a gas. Heat from the
surrounding liquid and solids moves into the molecules as they evaporate into a gas. The
liquid and solids the gas leaves behind are now cooler.
This is why sweating, or really any means of getting wet, cools down our bodies. The
water on our skin undergoes a phase change from liquid to gas, taking heat from our skin
Refrigerators work by containing that process in a closed system that continuously recirculates
that evaporating liquid, called a refrigerant. It's never released into the air, unlike the
steam coming off that sauce. In the closed system, the evaporating liquid stays in the
Heat energy that's stored in the food you're trying to cool down will evaporate a liquid
into a gas. That liquid is coursing through here in a system of pipes, probably in the
wall behind you. The refrigerator then compresses that gas and condenses it back down into a
liquid again by ditching its heat into the surrounding environment — that's why refrigerators
or air conditioners blow out hot air. The heat that I'm feeling on my hand right now
is the heat that was formerly in my house, plus the heat generated by the compressor
and the fans and all the other electrically powered gizmos in there.
And then the process just repeats itself on an endless loop. This is called the vapor
compression cycle, and it was first described as early as 1805 by an American engineer named
Oliver Evans, though he never actually built one. It was a century-long process for multiple
inventors to turn this idea into a product we would all eventually buy.
One reason why it took mechanical refrigeration so long to catch on was that there was already
a pretty good alternative — natural ice. I have a whole video about this linked in
the description. People used to harvest blocks of ice from ponds and lakes in the wintertime.
You could then store it in insulated ice houses all year long. You could even ship it to parts
of the world that don't have cold winters. In the 19th century, ice from the U.S. region
of New England made it all the way to India.
The first thing in people's homes that they called "refrigerators" were what we would
call "ice boxes" — literally just insulated food pantries into which you would load a
big block of natural ice.
As you can imagine, that system had its disadvantages, but it definitely would not poison you or
explode. Both of those things could happen with mechanical refrigeration. Why?
Because something harmless like water would be a terrible refrigerant inside a refrigerator.
It takes way too much energy to make water evaporate. Nah, buddy. What you want in here
Actually there were a few refrigerants used in early vapor-compression cycles but ammonia
was the most efficient. Still is. Under normal atmospheric pressure, anhydrous, or "water
free" ammonia has a boiling point of -28 degrees F, -33 C. The temperature inside a refrigerator
is more than enough to evaporate anhydrous ammonia, and when it does, it absorbs a huge
amount of energy.
The problem is that no closed system is ever completely closed. Some of the refrigerant
is gonna leak out, and if a lot of ammonia leaks out and you breath it in, you die. This
still happens, to this day, in big industrial refrigerators where ammonia remains a popular
refrigerant because it's so efficient. It takes less power to run an ammonia refrigerator,
and every now and then some poor worker breaths it in and dies.
A refrigerator also relies on an electrical compressor like that one to squeeze the refrigerant
down to a state of high pressure. And theoretically, any vapor under compression could explode,
violently. That's not something you ever want to have happen, and it's definitely not something
you want to have happen at the World's Columbian Exposition in Chicago in 1893, when you're
trying to convince a skeptical public that mechanical refrigeration is effective and
safe. But that is exactly what happened.
There was a fire in the elaborately disguised smoke stack rising above the cold storage
building. Chicago firemen climbed up on the tower to put it out, then the building exploded
beneath them. Thousands and thousands of fairgoers watched as the men now trapped high above
them had to decide, one by one, if they'd rather burn to death or jump.
Nobody knows for sure what caused the explosion, but it could have been the pressurized ammonia
in the refrigerator, and certainly that's what almost everybody believed at the time.
After that explosion, nobody wanted one of those in their kitchen. So what changed?
"The people who actually were in the auto industry for the most part started getting
interested in creating home refrigerators, and they started experimenting with different
This is Dr. Jonathan Rees, historian at Colorado State University Pueblo, and author of many
books on his topic, including the one we've been looking at, "Refrigeration Nation." He
describes how profoundly the world was changed by a global network of refrigerated supply
lines called the cold chain. And that is a network that enables, among other things,
the sponsor of this video, HelloFresh, whom I'll now briefly thank.
HelloFresh is America's #1 meal kit. You don't have to go to the grocery store. You don't
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Now, how did we all end up with an appliance in our homes that runs on something as dangerous
as anhydrous ammonia? Well, as Dr. Rees explains, we didn't.
"I mean, ammonia was good, and actually it remains good for large industrial refrigeration,
but you can't make an ammonia home refrigerator. So they started experimenting with different
refrigerants. This is eventually gonna lead to Freon in the 1920s, the real innovation
that makes refrigeration safe for everybody — maybe not the ozone layer, but safe for
not having poisonous gas leak out of the refrigerator in your kitchen."
Yep. Freon is a brand name for chlorofluorocarbons. CFCs and some similar chemicals are relatively
nontoxic to us, but when they inevitability rise to the upper atmosphere, they spark a
chain reaction that literally destroys the layer of O3, ozone, that protects us from
much of the sun's dangerous ultraviolet radiation, which eventually lead to various global bans,
and the gradual replacement of CFCs with similar chemicals that also have their own environmental
hazards, but they're still not ammonia. The fact that they found something to run these
things on other than ammonia means that we could all get these in our house — that
and the miniaturization of the machinery involved in running these things. Refrigerators used
to be huge.
"The first modern refrigerator is 1927. A lot of the models before that required you
to cut a hole in your kitchen and put the machinery in the basement, and there'd be
a belt that would be running. And it was just not viable for anybody who wasn't really rich.
But when they figured out a way to put the machinery and the cabinet in the same object
around '27, and then to mass-produce that object, home refrigerators took off really
quickly. And by WWII a majority of Americans had home refrigerators."
It still took some effort to convince consumers to ditch their old ice boxes, which worked
pretty well. But one of the marketing strategies that seemed work was, "Hey, buy an electric
refrigerator and then you won't have to let Adam's dirty Italian grandpa into your house."
Grandpa Ragusea was was an ice man who delivered blocks of ice to people's houses in New York.
"Sorta the image of the ice man is somebody with dirty feet who'll mess up your rug and
be a huge pain, or miss a day and all your food is gonna be spoiled. Electric refrigerator
manufacturers were arguing that you should get rid of the ice man, and there was good
reason to get rid of the ice man."
Poor grandpa. Refrigerators also eventually developed another killer feature that allowed
them to kill the ice man, and that was the ability to actually freeze things in here,
not just keep them cold.
The temperature in an ice box is well above freezing. In the 1940s, electric fridge manufacturers
started putting a little compartment in the corner where you could actually freeze water
into ice cubes, which is all people used it for at first.
The industry also made standalone electric freezers of course, and then in the 1950s,
combination refrigerator freezers, like mine here.
"The '50s is about the time when frozen food takes off."
Until home freezers over there, you actually had to cook the meals that you had at home.
But now you could buy totally prepared foods at the store, keep them frozen at home, thaw
them and eat them whenever you want. This probably did as much as anything to disrupt
the systems of gender and racial supremacy in which people like, well, me relied upon
other kinds of people to spend basically all day in here cooking.
But there was one major design flaw of the home refrigerator-freezer, and it brings us
back to where we started, to the heaters on the fridge.
"The big problem with early refrigerators is the frost, right?"
The air in your kitchen has water in it. The food that you put in there has water in it
too. That water is gonna condense on the cold surfaces and turn into frost — eventually,
thick layers of frost that block the transfer of heat from your food into the circulating
It used to be that every now and then you would have to defrost the fridge. Take everything
out — maybe try to eat everything that you had left — and then unplug the thing, open
the doors and let it all melt.
"You don't get frost-free refrigerators until 1957. It's an automatic mechanism that like
melts it from the outside. That's why the back — it's part of the reason why the back
of your refrigerator is hot, even though obviously the container is cold."
And that includes a little heater that runs through this gasket or air seal on the door.
It keeps this from getting gunked up with frost. But other than little gizmos like that,
this refrigerator is basically the same machine that rolled off the assembly lines about a
hundred years ago.
Though Dr. Rees says something big is coming — some different way of keeping stuff cool
that doesn't rely on hazardous refrigerants — and that is keeping stuff cool with magnets.
But that's a conversation for another day.