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Common absorption refrigerators use a refrigerant with a very low boiling point (less than −18 °C (0 °F)) just like compressor refrigerators.Compression refrigerators typically use an HCFC or HFC, while absorption refrigerators typically use ammonia or water and need at least a second fluid able to absorb the coolant, the absorbent, respectively water (for ammonia) or brine (for water).
The most common combinations are ammonia (refrigerant) and water (absorbent), and water (refrigerant) and lithium bromide (absorbent). Absorption refrigeration systems can be powered by combustion of fossil fuels (e.g., coal, oil, natural gas, etc.) or renewable energy (e.g., waste-heat recovery, biomass combustion, or solar energy).
The Einstein–Szilard or Einstein refrigerator is an absorption refrigerator which has no moving parts, operates at constant pressure, and requires only a heat source to operate. It was jointly invented in 1926 by Albert Einstein and his former student Leó Szilárd , who patented it in the U.S. on November 11, 1930 ( U.S. patent 1,781,541 ).
The refrigerants used in absorption systems are ammonia, water, or methanol, etc, which all experience phase changes between the vapor and liquid states - the same as in vapor compression refrigeration; while the adsorbent is a solid, such as silica gel, activated carbon, or zeolite. [1]
The first gas absorption refrigeration system using gaseous ammonia dissolved in water (referred to as "aqua ammonia") was developed by Ferdinand Carré of France in 1859 and patented in 1860. Carl von Linde, an engineering professor at the Technological University Munich in Germany, patented an improved method of liquefying gases in 1876.
The main difference with absorption cycle, is that in adsorption cycle, the refrigerant (adsorbate) could be ammonia, water, methanol, etc., while the adsorbent is a solid, such as silica gel, activated carbon, or zeolite, unlike in the absorption cycle where absorbent is liquid.
However, there are some typical examples for multicomponent based technologies such as Kalina cycle which uses water and ammonia mixture, or absorption refrigerators which also use water and ammonia mixture besides water, ammonia and hydrogen, lithium bromide or lithium chloride mixtures in a majority. Some scientific papers deal with the ...
There is an increasing use of cascade refrigeration systems that contain both ammonia and carbon dioxide. [26] Absorption chillers with a water/ammonia mixture are also cost effective in some applications such as combined chilling, heat and power systems. [1] Advancing technology also makes ammonia an increasingly viable option for small-scale ...