Adsorption refrigeration


Adsorption refrigeration was invented by Michael Faraday in 1821. Adsorption, sometimes is referred to solid sorption.
It is very similar to absorption refrigeration. The difference is that in adsorption refrigeration, the refrigerant or adsorbate vapour molecules adsorb onto the surface of a solid instead of dissolving into a liquid. In adsorption system, an adsorber adsorbs the refrigerant vapour into a solid, while in absorption system, an absorber absorbs the refrigerant vapour into a liquid. Adsoprtion refrigeration also includes a generation process where refrigerant vapour molecules desorbing from the solid.
The characteristics of the adsorbate/refrigerant pair is crucial in determining the system performance of a adsorption refrigeration system. The typical system performance indicators for an adsorption refrigeration system are coefficient of performance and specific cooling effect.
The refrigerants used in adsorption systems are ammonia, water, or methanol, etc, which experiences phase changes between vapor state and liquid state - the same as in vapor compression refrigeration; while the adsorbent is a solid, such as silicone gel, activated carbon, zeolite, For example, an adsorption refrigeration device with active carbon fiber being a adsorbent and ammonia being refrigerant was designed.
The reasons adsorption refrigeration technology has been extensively researched in recent 30 years lie in that the operation of an adsorption refrigeration system is often noiseless, non-corrosive and environment friendly. The heat source for adsorption refrigeration can be: Fossil fuel, Bio fuel, Waste heat, Solar thermal energy.
Adsorption refrigerators are available in the marketplace and are mainly used to produce chilled water from waste heat. Gas adsorption heat pumps are not currently available in the UK, but are just being introduced in Europe as small water or ground source packaged units for providing domestic low temperature space heating.