Why High-Frequency Pulse Tubes Can Be Tipped

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dc.contributor.author Swift, G. W. en_US
dc.contributor.author Backhaus, S. en_US
dc.date.accessioned 2011-05-05T19:55:54Z
dc.date.available 2011-05-05T19:55:54Z
dc.date.issued 2008-05
dc.identifier.isbn 978-1-934021-02-6
dc.identifier.uri http://hdl.handle.net/1853/38777
dc.description Presented at the 16th International Cryocooler Conference, held May 17-20, 2008 in Atlanta, Georgia. en_US
dc.description.abstract The 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 suppress en_US
dc.language.iso en_US en_US
dc.publisher Georgia Institute of Technology en_US
dc.relation.ispartofseries Cryocoolers 16. Pulse tube analysis and experimental measurements en_US
dc.subject Pulse tube analysis and experimental measurements en_US
dc.subject Convection en_US
dc.subject High frequency pulse tube cryocoolers en_US
dc.subject Oscillating velocity en_US
dc.title Why High-Frequency Pulse Tubes Can Be Tipped en_US
dc.type Proceedings en_US
dc.contributor.corporatename Los Alamos National Laboratory. Condensed Matter and Magnet Science Group en_US
dc.publisher.original ICC Press en_US

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