Refrigeration basic principle

Refrigeration basic principle named after two scientists, James Prescott Joule and William Thompson.This procedure is called a throttling process or Joule-Thomson.

The process where a gas or liquid change its temperature when it is forced through anexpansion valve or capillary tube in an insulated system where no ambient heat transfer. At STP (standard temperature and pressure) , all gases cool upon expansion by the Joule–Thomson process with the exception helium, neon and hydrogen gases.

Refrigeration basic principle applies on all system whether it's the smallest water cooler to largest walk-in freezer that ever built. Freon gas or the refrigerant absorbs heat inside the area to be cooled in the evaporator unit and transfers that heat to the refrigerator's condenser at exterior .

The Refrigeration basic principle is that with the aid of a heat pump, the refrigerant is being compressed to the condenser and capillary tube thus increasing its temperature (50-60°C) and pressure (750 kPa) in the refrigerator being cooled down by the condensing unit to 32°C depending the existing ambient temperature. Upon entering the evaporator unit the gas expanded and vaporized due to sudden enlargement of the evaporator tube cross-section eventually dropping its pressure to almost atmospheric value (120 kPa) and temperature from 32°C to -24°C. Heat absorption takes place from the evaporator and being pump-out by a heat pump to the condenser where being transformed from cool vapour to liquid state with higher temperature and pressure thus completing the heat transfer cycle.

Theoretically, after the cycle the amount of refrigerant will remain contained in the system. When leakage occurs in the closed circuit then efficiency of the refrigerator will gradually diminished till it stops cooling. By then, it requires servicing to be done by a qualified technician to locate its leakage or parts that are not functioning properly.


  2. Suction pipe or low pressure side with non-return valve.
  3. Liquid exit going to condensing unit with non-return valve.
  4. Water collector during defrosting process which gradually dries out.
  5. Freon or refrigerant charging point.
  6. Condensing unit usually in the form of serpentine tubes, with electro welded grill for effective ambient heat transfer.
  7. Vacuum application point to remove impurities and humidity prior to refrigerant charging.
  8. Capillary tube act as an orifice where inside diameter and length is being calculated to deliver the right flow of liquid to the evaporator unit. An alternative for capillary is expansion valve for large refrigeration and particular refrigerator units.
  9. Evaporator or collector unit usually in serpentine tube on plate OR fusion bonded aluminum plate evaporator.Serpentine tube on plate evaporator is widely used in refrigerator and freezers. Tube is in aluminum or copper. Copper has more heat transfer coefficient but it's heavier and more expensive compared to aluminium which is lighter. Aluminium tube on plate evaporator or absorber can improved the heat transfer coefficient like copper by just increasing the thickness of the aluminium plate.
  10. Accumulator, usually in copper or aluminium.


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