How Does a Refrigerator Keep Food Cold?

0:00How does a refrigerator keep food cold? Hi, welcome to Curious Kids Every Day. I'm Josh. How are you doing today? It's so good to hear from you. Hey, have you ever been in the kitchen? And you wanted to get a snack out of the refrigerator. So you open the doors and you grab your snack. But a few minutes later your dad walks in and says, um, why is the refrigerator door open? And you look over and you notice, oh, no, I forgot to shut it. That happens around here all the time. I always tell my kids we have to keep the refrigerator closed. It can't keep the food in their cold if the doors are open. But even when the refrigerator door is open,

1:00it still seems like everything is pretty cold in there, right? It's really cold. So what's really going on in the refrigerator? How does it keep food cold? How do refrigerators work? Well, here's the interesting thing about refrigerators. It's not really that it's keeping food cold. Refrigerators are really good at moving heat. Refrigerators take heat from inside the fridge and dump that heat into the air in your kitchen. So how does it move heat? Well, it uses a special fluid called refrigerant. Can you say refrigerant?

2:05The refrigerant is great at changing back and forth between liquid and gas. And when it changes, it can carry heat with it. A refrigerator has a few main parts that work in a loop. They do this over and over again. The first part that's very important is the evaporator coil. Can you say evaporator coil? This coil is usually hidden behind a panel in the back or the walls. When the refrigerant flows through this coil, it is very cold. And it starts to evaporate, which means it turns from a liquid into a gas. When a liquid evaporates, it needs energy to make that change. So it pulls heat from the nearby air and surfaces. That is why the inside air gets cooler. That is why your food stays cold. The refrigerant is basically sucking the heat out of the area.

3:12After the refrigerant has picked up heat inside and turned it into a gas, it travels into something called the compressor. Can you say compressor? The compressor is usually near the bottom back of the fridge. The compressor squeezes the gas. And when you squeeze a gas, its temperature goes up. So now the refrigerant is a hot, high pressure gas. Next is the condenser coil. Can you say condenser coil? It's usually on the back or underneath the refrigerator. The hot gas flows through these condenser coils that are exposed to your kitchen air. The coils let heat escape into the room. As the refrigerant loses heat, it condenses, which means it turns from a gas back into a liquid. If you've ever noticed that the back or bottom of your fridge feels warm, this is why.

4:17Now the refrigerant is a liquid again, but it's still under high pressure. It passes through something called an expansion valve that drops the pressure quickly. And when the pressure drops, the refrigerant gets much colder. Then it returns to the evaporator coil inside the fridge and the cycle starts again. And there are two more things that help a lot as well. Do you know what insulation is? They put insulation in the walls and doors of a refrigerator. And that helps slow down heat from sneaking in from your kitchen air. They put insulation in the walls of your house too and that keeps your house from getting too hot in the summer and too cold in the winter. And then there's also a thermostat, which senses temperature and turns the cooling system on and off to keep things in a safe cold range. Have you ever been sitting in your house when all of a sudden you hear your refrigerator click on? That's because the thermostat decided, hey, we need to make the temperature a little bit chillier in here.

5:23So when the door is left open, warm air rushes in and the fridge has to remove that extra heat. That means it has to work harder to suck more heat out of the fridge. The fridge can stay cold for a little while, but the longer the door stays open, the more heat sneaks in the harder the refrigerator has to work. So that is how a refrigerator keeps food cold. It's basically just sucking the heat out of the air and then dumping it out into your kitchen and it does all this using a special fluid called refrigerant. All right, let's have a quick quiz. What is the main job of a fridge to create cold or to move heat out of the inside? Yep, it's trying to move heat out of the inside and when you move heat out of a space, what happens to that space?

6:32Yep, it naturally gets colder. All right, where does the refrigerant absorb heat? The inside coil or the outside coil? The inside coil, the evaporator, and what part squeezes is the refrigerant gas? That part is called the compressor and why can the back or bottom of a fridge get warm? Because the condenser coils are dumping heat into the kitchen air. Let's play true or false? True or false? A refrigerator mostly works by moving heat from inside the fridge to the outside. Yeah, that's true. True or false, leaving the fridge door open, let's heat sneak in fast because warm air rushes inside. That's true too. True or false, insulation makes heat travel into the fridge faster.

7:36No, that's false, insulation keeps the heat out. Would you rather have a refrigerator that always stays filled with food automatically or would you rather have a refrigerator the size of a house? Have you ever been inside of a walk in refrigerator? Those things are really, really cold. I'm not sure I would want to refrigerator that big, but having a refrigerator that kept food stocked up for me, that sounds good. I wouldn't have to go to the grocery store anymore. Okay, let's play around of what am I? What am I? And this is the main thing I want you to take away from this episode, okay? So let's see if we can get this right. What am I? I'm a special kind of fluid. I can quickly change from a liquid to a gas. And I absorb heat from the refrigerator air and transfer it out of the refrigerator.

8:37What am I? I am refrigerant. Okay, so here's how a refrigerator works. Inside, the evaporator coil is stealing heat from the air. Then the refrigerant carries that heat to the compressor and out of the condenser coils. That's where the heat gets dumped into your kitchen. And that is why the inside stays cold and the back can feel warm. So now you know why the door matters so much. The fridge is basically fighting a heat leak all the time. The doors are so important. Every time warm air rushes in, the fridge has extra heat to move back out again. So closing the door is like helping your fridge do its job and it's saving energy. That's why your parents want to keep that door shut so that the refrigerator can do its job as efficiently as possible. Don't forget to shut the refrigerator door, please.

9:40What kind of question do you think we'll ask tomorrow on curious kids every day? I can't wait to find out. So until then, keep asking questions and stay curious kids. And we've got a few birthdays today. Today is Rin's birthday. Rin is from Brooklyn and Rin is turning four. Happy birthday, Rin. Orion is from Oregon and Orion is turning five. Happy birthday, Orion. Caden is from California and Caden is turning four. Happy birthday, Caden. Julian is from Vermont and Julian is turning seven. Happy birthday, Julian. Gahan is from California and Gahan is turning five. Happy birthday, Gahan. To all the grownups listening, if you're curious kid wants their birthday mentioned on the show, please visit supportcuriouskids.com and join the Curious Kids Club. That's supportcuriouskids.com. See you tomorrow.