How a Refrigerator Works

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Slide 1

How Refrigerators and Freezers Work

A refrigerator is a machine that can make its inside colder

A refrigerator is also called a “fridge”

Slide 2

A short history of refrigerators

Before the refrigerator was invented, some people would use ice from frozen lakes to keep food cool, but it was difficult and expensive to move so much ice

The first refrigerator used by many people was the "Monitor-Top" refrigerator starting in 1927

Home freezers started being used in the U.S. in 1940

A Monitor-Top refrigerator

Slide 3

How it works

: Step 1

When the temperature inside the refrigerator is above a certain set temperature, the thermostat turns on a compressor

A thermostat is a thermometer that can turn something on

A compressor is a machine that can squeeze a gas, which makes it have a smaller volume

The compressor is what you hear humming

A thermostat may look like this

A compressor is like an electricity-powered bicycle pump

Slide 4

Step 1 continued

The compressor then squeezes the refrigerant, which is a fluid used for cooling. The refrigerant is a gas at this time

This squeezing of the refrigerant causes it to increase in pressure and temperature

This shows how a gas can be compressed (squeezed)

Slide 5

Step 2

The very warm refrigerant goes through a coil outside (usually behind) the refrigerator where it loses heat to the air outside

A coil is a long, snake-like tube

This outside coil is called the “condenser coil” because as it cools, the refrigerant changes from a gas to a liquid (condenses) and gives off heat

Left: compressor

Right: condenser coils

Slide 6

Step 3

After the refrigerant has cooled down from giving heat to the air outside the fridge, the “expansion valve” opens to let the liquid refrigerant pass through it, into the coils inside the refrigerator

A “valve” is a small hole that can be opened or closed, and “expansion” means getting bigger, so what does “expansion valve” mean?

This is an expansion valve

Slide 7

Step 4

The pressure on the other side of the expansion valve in the evaporator coils is low

The pressure is low because the compressor has pulled the refrigerant out of that side in step 1

This low pressure makes the refrigerant change from a liquid to a gas (evaporate) and take in heat