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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).
Nowadays, the vapor absorption cycle is used only where heat is more readily available than electricity, such as industrial waste heat, solar thermal energy by solar collectors, or off-the-grid refrigeration in recreational vehicles. The absorption cycle is similar to the compression cycle, but depends on the partial pressure of the refrigerant ...
However, absorption chillers, from an energy-efficiency point of view, excel where cheap, low-grade heat or waste heat is readily available. [9] In extremely sunny climates, solar energy has been used to operate absorption chillers. The single-effect absorption cycle uses water as the refrigerant and lithium bromide as the absorbent. It is the ...
The most common refrigeration cycle is the vapor compression cycle, which models systems using refrigerants that change phase. The absorption refrigeration cycle is an alternative that absorbs the refrigerant in a liquid solution rather than evaporating it. Gas refrigeration cycles include the reversed Brayton cycle and the Hampson–Linde cycle.
The operating principle of the refrigeration cycle was described mathematically by Sadi Carnot in 1824 as a heat engine. The most common types of refrigeration systems use the reverse-Rankine vapor-compression refrigeration cycle, although absorption heat pumps are used in a minority of applications. Cyclic refrigeration can be classified as:
A representative pressure–volume diagram for a refrigeration cycle. Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), [1] in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles.
The absorption cycle is the one limiting the choice of the refrigerant. The most common refrigerants for absorption systems are ammonia and water. [13] Both are good for combined absorption-compression heat pumps. [14] [15] Ammonia has an exceptionally good solubility in water. This is an important aspect that increases the performance and ...
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).