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A Cryocooler is a standalone cooler, usually of table-top size. It is used to cool some particular application to cryogenic temperatures. A recent review is given by Radebaugh.〔R. Radebaugh, J. Phys.: Condens. Matter, Vol.21, 164219 (2009)〕 The present article deals with various types of cryocoolers and is partly based on a paper by De Waele.〔A.T.A.M. de Waele, Basic operation of cryocoolers and related thermal machines, Review article, Journal of Low Temperature Physics, Vol.164, pp. 179-236, (2011), DOI: 10.1007/s10909-011-0373-x.〕 == Ideal heat exchangers and regenerators == Heat exchangers are important components of all cryocoolers. Ideal heat exchangers have no flow resistance and the exit gas temperature is the same as the (fixed) body temperature ''T''X of the heat exchanger. Note that even a perfect heat exchanger will not affect the entrance temperature ''T''i of the gas. This leads to losses. An important component of refrigerators, operating with oscillatory flows, is the regenerator. A regenerator consists of a matrix of a solid porous material, such as granular particles or metal sieves, through which gas flows back and forth. Periodically heat is stored and released by the material. The heat contact with the gas must be good and the flow resistance of the matrix must be low. These are conflicting requirements. The thermodynamic and hydrodynamic properties of regenerators are very complicated, so one usually makes simplifying models. In its most extreme form an ''ideal'' regenerator has the following properties: * large volumetric heat capacity of the material; * perfect heat contact between gas and matrix; * zero flow resistance of the matrix; * zero porosity (this is the volume fraction of the gas); * zero thermal conductivity in the flow direction; * the gas is ideal. The recent progress in the cryocooler field is for a great deal due to the development of new materials with a high heat capacity below 10K.〔T. Kuriyama, R. Hakamada, H. Nakagome, Y. Tokai, M. Sahashi, R. Li, O. Yoshida, K. Matsumoto, and T. Hashimoto, Advances in Cryogenic Engineering 35B, 1261 (1990)〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cryocooler」の詳細全文を読む スポンサード リンク
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