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dc.contributor.authorSwift, G. W.en_US
dc.contributor.authorBackhaus, S.en_US
dc.date.accessioned2011-05-05T19:55:54Z
dc.date.available2011-05-05T19:55:54Z
dc.date.issued2008-05
dc.identifier.isbn978-1-934021-02-6
dc.identifier.urihttp://hdl.handle.net/1853/38777
dc.descriptionPresented at the 16th International Cryocooler Conference, held May 17-20, 2008 in Atlanta, Georgia.en_US
dc.description.abstractThe typical low-frequency pulse-tube refrigerator loses significant cooling power when it is tipped with the pulse tube’s cold end above its hot end, because natural convection in the pulse tube loads the cold heat exchanger. Yet most high-frequency pulse-tube refrigerators work well in any orientation with respect to gravity. In such a refrigerator, natural convection is suppressed by sufficiently fast velocity oscillations, via a nonlinear hydrodynamic effect that tends to align the density gradients in the pulse tube parallel to the oscillation direction. Since gravity’s tendency to cause convection is only linear in the pulse tube’s end-to-end temperature difference while the oscillation’s tendency to align density gradients with oscillating velocity should be quadratic in that temperature difference, it is easiest to suppress convection when the end-to-end temperature difference is largest. Simple experiments demonstrate this temperature dependence, the strong dependence on the oscillating velocity, and little or no dependence on the magnitude or phase of the oscillating pressure. In some circumstances in this apparatus, the suppression of convection is a hysteretic function of oscillating velocity. In some other circumstances, a time-dependent convective state seems more difficult to suppressen_US
dc.language.isoen_USen_US
dc.publisherGeorgia Institute of Technologyen_US
dc.relation.ispartofseriesCryocoolers 16. Pulse tube analysis and experimental measurementsen_US
dc.subjectPulse tube analysis and experimental measurementsen_US
dc.subjectConvectionen_US
dc.subjectHigh frequency pulse tube cryocoolersen_US
dc.subjectOscillating velocityen_US
dc.titleWhy High-Frequency Pulse Tubes Can Be Tippeden_US
dc.typeProceedingsen_US
dc.contributor.corporatenameLos Alamos National Laboratory. Condensed Matter and Magnet Science Groupen_US
dc.publisher.originalICC Pressen_US


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