A Temperature Instability in 4 K Cryocooler Regenerators Caused by Real Fluid Properties

Published

April 1, 2021

Author(s)

Ryan Snodgrass, Vincent Y. Kotsubo, Joel Ullom, Scott Backhaus

Abstract

We report temperature profile measurements from a densely instrumented, commercial pulse tube refrigerator. Azimuthal temperature differences of 15 K were measured across its 3 cm diameter regenerator which was operated at cold end temperatures below 10 K. These asymmetries may appear and disappear with just 0.1 K changes to the cold end temperature, suggesting a potential thermofluid instability. Experiments and analysis suggest that real fluid properties of helium at low temperatures may be the driving mechanism of the instability. We sketch the beginnings of a linear perturbation analysis and show that small changes to regenerator temperature profiles are reinforced by accompanying changes to the component of power flow due to real fluid properties, particularly at temperatures less than 9 K. Our measurements show that temperature asymmetries are specific to particular sections within the regenerator and negatively affect cooling power at the cold end.

Proceedings Title

Cryocoolers 21

Conference Dates

December 7-10, 2020

Conference Location

Virtual/online, CO, US

Conference Title

21st International Cryocooler Conference

Pub Type

Conferences

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Keywords

Cryocooler, pulse tube refrigerator, real fluid effects, thermodynamics

Citation

Snodgrass, R. , Kotsubo, V. , Ullom, J. and Backhaus, S. (2021), A Temperature Instability in 4 K Cryocooler Regenerators Caused by Real Fluid Properties, Cryocoolers 21, Virtual/online, CO, US, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=931604 (Accessed December 2, 2024)