We were exploring the Wonderopolis kitchen one day in search of snacks when we overheard an interesting conversation between an unidentified caller and the head chef:
Chef: Wonderopolis kitchen! This is Chef Boyoboy speaking. How can I assist you?
Caller: Yes, sir, I was WONDERing…is your refrigerator running?
Chef: The refrigerator? Of course, it’s running!
Caller: Well, you’d better go catch it! Ah ha ha ha ha ha ha!
Chef: Grrr…
Alright, so that’s an old, old joke, but we still enjoy it! However, it did make us WONDER…exactly how does a refrigerator work?
Before delving into the science and mechanics of refrigerators, let’s first take a moment to be grateful for their existence. In the past, people had to rely on iceboxes and large blocks of ice to keep things cold. Even then, it was often only the very wealthy who could afford such a luxury.
Today, refrigerators are found in every home, and we’re certainly glad they are. Besides keeping drinks at a refreshing temperature, they also ensure our food is safe to consume. Without refrigeration, most foods would spoil within a matter of days, if not hours. Refrigeration slows down the growth of bacteria to the point where foods can last for weeks and even months if frozen.
So how do refrigerators keep all that food cool? Do they blow cold air over the food? Nope! They operate much like the air conditioning system in your home: they continually remove the warm air inside the refrigerator, releasing it outside until the air inside becomes cool. To achieve this, they rely on the principles of gas.
The cooling system of a refrigerator consists of five main components: fluid coolant (known as refrigerant), a compressor, condenser coils (located outside), evaporator coils (located inside), and an expansion valve. The compressor takes the vaporized refrigerant (more on this later) and compresses it, increasing its pressure as it pushes it through the condenser coils outside the refrigerator.
In the condenser coils, the hot gas releases its heat to the outside air. As this happens, it cools down and transforms back into a liquid. It continues to cool as it flows into the interior of the refrigerator. When it reaches the expansion valve, the liquid expands and converts into a gas.
As it passes through the evaporator coils, the vaporized refrigerant absorbs heat from inside the refrigerator, cooling the air inside in the process. Upon exiting the evaporator coils, it reenters the compressor and the cycle begins anew.
This cycle continues until a device called a thermocouple (essentially a sophisticated thermometer) detects that the air inside the refrigerator has reached the desired temperature. At this point, it cuts off power to the compressor. When you open the refrigerator door and let more heat inside, the thermocouple senses a rise in temperature and restarts the compressor.
Although all of this may sound a bit complex, it’s actually quite simple, and you’ve probably encountered the same principles of gas in your everyday life. For instance, have you ever gotten out of a swimming pool and felt a slight chill despite being in bright sunshine? This occurs because the water on your skin is evaporating, drawing heat away from your skin in the process.
Give it a Try
Are you prepared for a snack? Make sure to explore the following activities with a companion:
- How effective is your refrigerator at keeping your food cool? Get a thermometer and find out! Place the thermometer in the fresh food area of your refrigerator and let it sit for a few minutes. Take note of the temperature, and then move the thermometer to the freezer. Once again, let it sit for a few minutes before noting the temperature. What is the temperature difference between the freezer and the fresh food area?
- Ask an adult family member or friend to assist you in examining your refrigerator up close. Hint: they will probably be more excited about this learning opportunity if you assist them in cleaning out the refrigerator at the same time! If possible, pull out the refrigerator to get a look at the external coils. Can you identify any of the other parts of the system? Double-check the temperature settings to ensure that you are minimizing energy usage!
- How would your everyday life change without a refrigerator? Consider the foods you typically eat on a weekly basis. How would your meals change if you only relied on non-refrigerated foods in the cupboard? How do you think you would have enjoyed living in the past when refrigerators were not common?
Sources of Wonder
- http://www.explainthatstuff.com/refrigerator.html
- http://energyquest.ca.gov/how_it_works/refrigerator.html
- http://www.realsimple.com/food-recipes/tools-products/appliances/how-does-refrigerator-work
FAQ
1. How does a refrigerator work?
A refrigerator works by using a refrigeration cycle to remove heat from the inside of the refrigerator and release it to the outside. This cycle involves a refrigerant, which is a chemical compound that can easily change between a gas and a liquid. The refrigerant absorbs heat from the food and air inside the refrigerator, causing it to evaporate into a gas. The gas is then compressed, which increases its temperature even further. Finally, the compressed gas is condensed back into a liquid, releasing the heat it absorbed. This process continues in a loop, continuously cooling the inside of the refrigerator.
2. What is the role of the compressor in a refrigerator?
The compressor is an essential component of a refrigerator. It is responsible for compressing the refrigerant gas, which increases its temperature and pressure. By compressing the gas, the compressor helps to remove heat from the inside of the refrigerator. The compressed gas then flows to the condenser where it releases the heat it absorbed. Without the compressor, the refrigeration cycle would not be able to function properly, and the refrigerator would not be able to cool down the contents inside.
3. How does the thermostat control the temperature in a refrigerator?
The thermostat in a refrigerator is a temperature-sensitive switch that controls when the compressor turns on and off. It is set to a desired temperature, and when the temperature inside the refrigerator rises above that set point, the thermostat signals the compressor to start. Once the temperature reaches the set point, the thermostat stops the compressor. This cycle repeats as needed to maintain a consistent temperature inside the refrigerator. The thermostat ensures that the refrigerator cools down when necessary and prevents it from overcooling or wasting energy by running constantly.
4. What is the purpose of the condenser in a refrigerator?
The condenser in a refrigerator is responsible for releasing the heat that was absorbed from the inside of the refrigerator. The compressed refrigerant gas flows into the condenser, where it is cooled down and condensed back into a liquid state. As the gas condenses, it releases heat to the surrounding environment, usually through metal fins or coils. This heat transfer process allows the refrigerant to release the heat it absorbed and become ready to start the cycle again. Without a functioning condenser, the refrigerator would not be able to cool down effectively.
5. How does the evaporator coil work in a refrigerator?
The evaporator coil in a refrigerator is located inside the freezer or the refrigerator compartment. It is responsible for absorbing heat from the food and air inside the refrigerator. The refrigerant gas enters the evaporator coil after leaving the compressor. As the gas flows through the coil, it expands and becomes colder, causing it to absorb heat from the surroundings. This process cools down the interior of the refrigerator. The evaporator coil is designed with thin metal fins to maximize the surface area for heat exchange, allowing for efficient cooling.
6. Can a refrigerator work without electricity?
No, a refrigerator cannot work without electricity. It relies on electricity to power the compressor, which is essential for the refrigeration cycle. The compressor requires electricity to compress the refrigerant gas and remove heat from the inside of the refrigerator. Additionally, the fan inside the refrigerator, which helps circulate the cold air, also requires electricity to operate. Without a constant source of electricity, a refrigerator would not be able to function and keep the contents cool. Therefore, during power outages or in areas without electricity, refrigerators may lose their cooling capabilities.
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