A Moment of Science

The Rolling Boil That Cools Your Food

It sounds crazy, but household refrigerators keep food cold by bringing liquid fluorocarbon to a boil.

refrigerator coils

Photo: Grant Bierman (Flickr)

You've probably seen one set of coils behind the fridge, in back. That's where heat's released.

When you think of something boiling, you probably picture a pot on the stove, but there’s another kitchen appliance that brings liquid to a boil, not to heat food, but cool it. It sounds crazy, but household refrigerators keep food cold by bringing liquid fluorocarbon to a boil.

How Does This Work?

Fluorocarbon coolant flows through two sets of coils in your fridge, absorbing heat inside and releasing it outside, into your kitchen. You’ve probably seen one set of coils behind the fridge, in back. That’s where heat’s released. Hidden inside the fridge is the other set of coils, where heat’s absorbed.

It’s inside these hidden coils that liquid coolant comes to a boil. What makes the coolant boil? The secret is in the relationship between pressure and boiling point. When pressure changes, so does the temperature at which a substance comes to a boil.

Liquid Coolant

As the liquid coolant passes through a valve into the hidden coils, the pressure drops. This pressure change makes the coolant’s boiling point drop below the chilly temperature in the fridge. So, some of the coolant boils immediately and evaporates into a gas inside the coil. Evaporation uses up lots of heat energy. As the coolant continues to boil and evaporate, it absorbs heat from the air in the fridge, making it even colder inside. So that’s how boiling fluorocarbon cools your food.

Stay Connected

What is RSS? RSS makes it possible to subscribe to a website's updates instead of visiting it by delivering new posts to your RSS reader automatically. Choose to receive some or all of the updates from A Moment of Science:

Support for Indiana Public Media Comes From

About A Moment of Science

Search A Moment of Science