How does it work - Refrigerator

How does it work - Refrigerator

This animation demonstrates how a refrigerator works.

Technology

Keywords

refrigerator, fridge, household appliance, cooling, heat reduction, heat release, compressor, condenser, refrigerant, electric, thermodynamics, technology, physics

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Scenes

Refrigerator

Construction

  • condenser - While the hot vapour flows through this, it releases heat into the environment and condenses.
  • compressor - It compresses warm vapour flowing out of the food compartment, making it hot and therefore releasing heat while flowing into the condenser.
  • expansion valve - It reduces the previously high-pressure of the warm liquid, therefore some of the liquid evaporates and it cools down. The resulting cold vapour-liquid mixture flows in to the evaporator inside the food compartment.
  • evaporator - While the cold refrigerant flows through this pipe system, it draws heat away from the refrigerator compartment. Meanwhile it completely evaporates, which draws away more heat.
  • heat reduction (cooling)
  • heat release

The refrigerator is fundamentally a heat pump that transfers heat from its interior to its surroundings.

Its principle of operation is as follows: A compressor keeps a volatile liquid, usually isobutene, flowing through a closed pipe system. There is a valve in the pipe system that partially restricts the flow of this liquid, called the refrigerant. When the liquid reaches the valve, it is under high pressure, but as it passes through the valve, its pressure drops, and it partially evaporates.

Evaporation results in heat reduction, and the temperature will thus be lower here. The evaporator part of the system is placed inside the refrigerator.

Once the evaporated liquid passes through the compressor and approaches the valve, it is compressed again, causing it to condense, which in turn results in heat release, so its temperature will be higher. That is why we experience that the back of the refrigerator is warm. After the refrigerant passes through the valve, the process starts from the beginning.

The air conditioner works on the same principle as the refrigerator. If the direction of the flow of the liquid were reversed, the warm and the cool side would change too, meaning that we could even heat with the heat pump. In fact, some air conditioners are suitable for heating as well.

Even though the interior of the refrigerator is cold, the refrigerator will heat the flat as it draws energy from the electrical outlet to operate the compressor. It is therefore not worth leaving the door of the refrigerator open and using it as an air conditioner as long as the heat exchanger (or condenser) on the back is also in the room.

Expansion valve

  • warm liquid
  • cooled refrigerant - A mixture of cold vapour and liquid, cooling the refrigerator compartment.
  • high pressure
  • low pressure
  • expansion valve - The warm liquid enters the expansion valve, flowing through it the pressure decreases and some of the liquid evaporates and meanwhile it cools down.

Compressor

  • warm vapour - The warm and vaporised refrigerant leaving the refrigerator compartment.
  • hot vapour - It compresses the warm vapour flowing out of the evaporator inside the refrigerator compartment. This causes it to warm up and therefore release heat while flowing into the condenser.

Animation

  • condenser - While the hot vapour flows through this, it releases heat into the environment and condenses.
  • compressor - It compresses warm vapour flowing out of the food compartment, making it hot and therefore releasing heat while flowing into the condenser.
  • expansion valve - It reduces the previously high-pressure of the warm liquid, therefore some of the liquid evaporates and it cools down. The resulting cold vapour-liquid mixture flows in to the evaporator inside the food compartment.
  • evaporator - While the cold refrigerant flows through this pipe system, it draws heat away from the refrigerator compartment. Meanwhile it completely evaporates, which draws away more heat.
  • heat reduction (cooling)
  • heat release
  • hot vapour
  • warm liquid
  • cooled refrigerant - The cold vapour-liquid mixture leaving the expansion valve which cools the refrigerator compartment.
  • warm vapour
  • warm vapour - The warm and vaporised refrigerant leaving the refrigerator compartment.
  • hot vapour - It compresses the warm vapour flowing out of the evaporator inside the refrigerator compartment. This causes it to warm up and therefore release heat while flowing into the condenser.

Principle of operation

  • condenser - While the hot vapour flows through this, it releases heat into the environment and condenses.
  • compressor - It compresses warm vapour flowing out of the food compartment, making it hot and therefore releasing heat while flowing into the condenser.
  • expansion valve - It reduces the previously high-pressure of the warm liquid, therefore some of the liquid evaporates and it cools down. The resulting cold vapour-liquid mixture flows in to the evaporator inside the food compartment.
  • evaporator - While the cold refrigerant flows through this pipe system, it draws heat away from the refrigerator compartment. Meanwhile it completely evaporates, which draws away more heat.
  • heat reduction (cooling)
  • heat release
  • hot vapour
  • warm liquid
  • cooled refrigerant - The cold vapour-liquid mixture leaving the expansion valve which cools the refrigerator compartment.
  • warm vapour

Narration

While a refrigerator cools down food stored inside, it draws heat away from the food compartment and releases it outside. Let's follow the phases of this process starting in the food compartment.

The refrigerant - a cold mixture of vapour and liquid - flows into the pipe system of the evaporator. Due to the difference in temperatures, the refrigerant draws heat away from the food compartment. The refrigerant becomes hot and fully evaporates, which draws away more heat.

The vapour from the food compartment flows into the compressor, which compresses it and causes its pressure and temperature to rise.

The resulting hot vapour is conducted into the condenser, where the temperature difference between the vapour and its surroundings causes the vapour to release heat. The vapour flowing in the pipe condenses and becomes liquid.

This partly cooled, warm liquid then enters the expansion valve. Here it collects and therefore the pressure in the incoming pipe is high, while the pressure in the outgoing pipe is low. As the liquid flows through the expansion valve, its pressure drops suddenly and therefore it partly evaporates and cools down.

The resulting cold mixture of vapour and liquid is conducted back into the evaporator.

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