Experiments with Linear Compressors for Phase Shifting in Pulse Tube Cryocoolers

Published

June 13, 2011

Author(s)

Michael A. Lewis, Peter E. Bradley, Ray Radebaugh

Abstract

For the past year NIST has been investigating the use of mechanical phase shifters as warm expanders for pulse tube cryocoolers. Unlike inertance tubes, which have a limited phase shifting ability at low acoustic powers, mechanical phase shifters have the ability to provide nearly any phase angle between the mass flow and the pressure. We discuss our results with experiments and modeling on a commercially available miniature linear compressor operating as an expander on the warm end of a 4 K pulse tube, whose temperature is nominally about 35 K. We also present results on experiments with a linear compressor operating at room temperature but coupled to the 4 K stage through secondary regenerators and secondary pulse tubes. Experiments on a small pulse tube test apparatus with both 4He and 3He showed improved efficiency when using the mechanical expander over that of inertance tubes. Phase locking techniques using function generators and power amplifiers for phase angle control are detailed. The use of expanders demonstrates flexible control in optimizing phase angles for improved cryocooler performance.

Proceedings Title

"Experiments with Linear Compressors for Phase Shifting in Pulse Tube Cryocoolers

Conference Dates

June 13-16, 2011

Conference Location

Spokane, CO

Pub Type

Conferences

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DOI Link

Keywords

compressor, cryocooler, expander, hybrid, mechanical phase shifter, phase angle, phase-locking, pressure oscillator, PV power, secondary pulse tube, secondary regenerator

Citation

Lewis, M. , Bradley, P. and Radebaugh, R. (2011), Experiments with Linear Compressors for Phase Shifting in Pulse Tube Cryocoolers, "Experiments with Linear Compressors for Phase Shifting in Pulse Tube Cryocoolers, Spokane, CO, [online], https://doi.org/10.1063/1.4707091 (Accessed October 10, 2025)