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Vapor-compression refrigeration [6] For comparison, a simple stylized diagram of a heat pump's vapor-compression refrigeration cycle: 1) condenser, 2) expansion valve, 3) evaporator, 4) compressor (Note that this diagram is flipped vertically and horizontally compared to the previous one) [7] Temperature–entropy diagram of the vapor-compression cycle.
A cascade refrigeration cycle is a multi-stage thermodynamic cycle. An example two-stage process is shown at right. (Bottom on mobile) The cascade cycle is often employed for devices such as ULT freezers. [1] In a cascade refrigeration system, two or more vapor-compression cycles with different refrigerants are used.
A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporating coil, 4) compressor. The refrigeration cycle uses four essential elements to cool, which are compressor, condenser, metering device, and evaporator.
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 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:
The Hampson–Linde cycle differs from the Siemens cycle only in the expansion step. Whereas the Siemens cycle has the gas do external work to reduce its temperature, the Hampson–Linde cycle relies solely on the Joule–Thomson effect ; this has the advantage that the cold side of the cooling apparatus needs no moving parts.
Schematic diagram of a cryogen-free, or dry, dilution refrigerator precooled by a two-stage pulse tube refrigerator, indicated by the dotted rectangle. A 3 He/ 4 He dilution refrigerator is a cryogenic device that provides continuous cooling to temperatures as low as 2 mK , with no moving parts in the low-temperature region.