Your fridge heats your kitchen
Everything the fridge pulls out of its cabinet ends up in the room, plus the electricity it used to do it. So a fridge with its door left open still warms the kitchen overall, even though cold air spills out.
Explainer No. 4
The refrigerator
A fridge doesn't make cold. It picks heat up inside the cabinet and carries it out into your kitchen, using a liquid that boils below freezing and a pump to squeeze it. Follow the refrigerant round its loop.
Freezer−18.0°air, °C
Fridge3.5°air, °C
Kitchen22°°C
Fridge temperature · last 4 hours
Fridge air
Fridge food
Compressor running
Thermostat switches
Where the heat went · since you arrived
Pulled out of the cabinet0 Wh
Electricity used0 Wh
Dumped into the kitchen0 Wh
Show the readings as a table
| Model time | Fridge air | Fridge food | Freezer air | Compressor |
|---|
Thermostat
Door
Power
Time
Compressor on
Runs 0% of the time
Model time 0:00
×60
Every moving part
Point at a part to find it in the drawing. The defrost heater and its timer are left out.
- Refrigerantthe one that carries the heat
A fluid that boils far below freezing at low pressure. It soaks up heat as it boils inside, and gives it back as it condenses outside.
- Compressor×1
A motor-driven pump sealed in a steel can. It squeezes the cold vapor to high pressure, which also makes it hot. (Drawn here with a piston.)
- Evaporator fan×1
Pushes air over the freezer's cold coils and sends cold air down into the fridge.
- Thermostat×1
Switches the compressor on when the fridge air warms to the top of its band, and off when it reaches the bottom.
- Doors×2
Insulated like the walls, each with a magnetic seal around its edge.
- Evaporator
The cold coils in the freezer, where the refrigerant boils and soaks up heat.
- Condenser coils
On the back (or underneath). The hot refrigerant gives its heat to the room here and turns back into liquid.
- Capillary tube and drier
A very thin tube that lets the pressure drop. The drier in front of it catches any moisture.
- Insulation
Foam in the walls and door that slows down the heat leaking back in.
4 °C(40 °F) or colder in the fridge, says the FDA
−18 °C(0 °F) in the freezer
4stages: boil, squeeze, condense, release
1pump does all the lifting
Why it works
Why the back is warm
The coils on the back (or underneath) are where the heat leaves. The refrigerant arrives there hotter than the room, so heat flows out of it, and it condenses back to a liquid.
The food barely notices
Here the thermostat lets the air swing about a degree either way as the compressor clicks on and off. The food can soak up far more heat than the air can, so its temperature hardly moves. Watch the two lines on the chart.
Why a frost-free fridge has a heater
Moisture in the air freezes onto the evaporator coils. In a frost-free fridge a small heater near the coils melts it off now and then, on a timer, and the water drains away.
In a power cut, keep it shut
With no power, nothing carries the heat out, but the insulation and the cold food buy time. The FDA says an unopened fridge keeps food cold for about 4 hours, and a full freezer holds its temperature for about 48 hours (24 if it's half full).
Older than it looks
Jacob Perkins built the first working vapor-compression refrigeration system in 1834. Electric fridges for the home arrived in the 1910s and spread in the 1930s. Their CFC refrigerants were later phased out under the Montreal Protocol, agreed in 1987, because they damage the ozone layer.
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