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Pulse Tube Coolers (Cycle, Engines, Cryogenics Refrigerators, Cryocoolers)
Fig 1- Analogy between Pulse Tube and Stirling Cycle.
Figure 1 shows the analog between the Stirling cooler and the pulse tube. As the compressor piston compresses from 1) to 2), the pressure in the system increases. During this phase, very little gas is transferred into the surge volume via the orifice, as the initial pressure difference across the orifice is small. As the piston compresses further from 2) to 3), more working gas passes through the orifice into the surge volume. The end result is very close to an isochoric process in a Stirling cycle (with the expansion of the displacer). The net effect is that the working gas is displaced across regenerator with heat transfer between the gas and the matrix material. As the compressor piston reaches its maximum stroke and becomes stationary 3) to 4), expansion occurs because gas continues to flow into the surge volume, which is at a lower pressure and the pressure within the pulse tube system drops. Finally, a combination of gas exiting the surge volume and the expansion of the compression space result in another near-isochoric process, 4) to 1) that completes the cycle. As a result, an amount of heat, QH=THdS is rejected from the system while QC=TCdS is absorbed at the coldtip (Fig 2).
Fig 2- The Stirling Cycle.
"Design and Preliminary Testing of BEIs CryoPulse 1000, the Commercial One Watt Pulse Tube Cooler", Proceedings of the 10th International Cryocooler Conference, P191, 1998. (with D.T.Kuo and A.S.Loc) Abstract Download
"Design of a 0.5 Watt Dual Use Long-Life Low-Cost Pulse Tube Cooler", in Proc. of Advances of Cryogenic Engineering Conference, vol. 43B, P2039, 1997. (with D.T.Kuo, A.S.Loc and A.L. Johnson) Abstract Download
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About the author- Dr. Sidney Yuan is a consultant in the field of Low Temperature Physics and Cryogenics, and has written a Book on Cryogenics and published extensively in the field. E-Mail.
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