2007年7月31日星期二

Pump

A pump is a device used to move liquids or slurries. A pump moves liquids from lower pressure to higher pressure, and overcomes this difference in pressure by adding energy to the system (such as a water system). A gas pump is generally called a compressor, except in very low pressure-rise applications, such as in heating, ventilating, and air-conditioning, where the operative equipment consists of fans or blowers.
Pumps work by using mechanical forces to push the material, either by physically lifting, or by the force of compression.
The earliest type of pump was the Archimedes screw, described by Archimedes in the 3rd century BC, but used earlier by Sennacherib, King of Assyria, in the 7th century BC.[1] In the 13th century AD, al-Jazari described and illustrated different types of pumps, including reciprocating pumps, double acting pumps with suction pipes, water pumps, and pistons.[2][3]

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