User:Milton Beychok/Sandbox

An expansion turbine, also referred to as a turboexpander or turbo-expander, is a centrifugal or axial flow turbine through which a high pressure gas is expanded to produce work that is typically used to drive a gas compressor.

Because work is extracted from the expanding high pressure gas, the expansion is an isentropic process (i.e., a constant entropy process) and the low pressure exhaust gas from the turbine is at a very low temperature, often as low as 200 K (-100 °F) or less. Turbo-expanders are very widely used as sources of refrigeration in industrial processes such as the extraction of ethane and natural gas liquids (NGLs) from natural gas; the liquefaction of gases; and other low-temperature processes.

In 1939, Pyotr Kapitza of Russia suggested the use of a centrifugal turbine for the isentropic expansion of gases to produce refrigeration. Since then, centrifugal expansion turbines have takrn over almost 100 percent of the gas liquefaction and other low-temperature industrial requirements.