Technology and Engineering · High school

The refrigeration cycle of a fridge

The refrigerant boils at low pressure in the freezer and takes in heat, then condenses at the back and gives it off.

In the learning section below the figure, predict, try, complete the tasks and check yourself with short questions.

Fig. 1The refrigeration cycle of a fridge

Tap the door, the thermostat knob or the compressor, or take the fridge apart

Inside 5.2 °C · room 22.0 °C · compressor waiting: the fridge is cold enough

Parts and hidden mechanism

Separation0%

In the opened-up fridge, hover over a part, tap it, or pick it from the list.

Pick an assembly: what it does, and why a real fridge is built that way, appears here.

Inside the fridge

5.2 °C

Room

22.0 °C

Thermostat setting4.0 °CThe compressor starts at 5.0 °C and stops at 3.0 °C

Compressor: waiting: the fridge is cold enough

Time passed: 0 min (1 second on screen = 1 minute)

Heat budget (right now)

Heat taken from inside0 W
Electrical power of the compressor0 W
Heat given to the room0 W

While the compressor rests, the refrigerant does not circulate and no heat is carried.

Enter your own values

Thermostat

Room temperature

Compressor power

Points on the cycle

Compressor outlet · hot vapourpressure 1.85 bar · temperature 22 °C
Condenser outlet · warm liquidpressure 1.85 bar · temperature 22 °C
Capillary outlet · cold liquid + vapourpressure 1.85 bar · temperature 5 °C
Evaporator outlet · cold vapourpressure 1.85 bar · temperature 5 °C

Learn

Progress is kept on this page only; no points are given.

1Predict
2Try
3Explain

On a hot day, if you leave the fridge door open and keep it running, what happens to the room?

Gold tube: hot refrigerant · Purple tube: cold refrigerantSolid line: liquid · Dots: vapourThe numbers come from one simple model: the refrigerant is isobutane (R600a, common in household fridges), and pressures are absolute, in bar, from a curve close to this refrigerant’s real saturation curve. The default values are a 4 °C thermostat, a 22 °C room and a 60 W compressor; you can type your own values in the boxes. A stronger compressor cools the evaporator further and removes more heat, but the electricity it uses grows faster. The fridge and the room are each treated as one body at a single temperature, and heat stored in the tubes is ignored. In a real fridge the values depend on the model, the refrigerant and the surroundings.

How does a fridge keep things cold? The vapour-compression refrigeration cycleRead the article

The refrigeration cycle of a fridge

Parts and hidden mechanism

Heat budget (right now)

Enter your own values

Points on the cycle

Learn

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