Abstract A method has been devised to fabricate a uniform channel parallel plate heat exchanger suitable for high frequency low temperature regenerative cryocooler applications. The low porosity matrix design theoretically optimizes heat transfer and operating efficiency while minimizing losses, including thermodynamic losses in the matrix void volume, at higher operating frequencies than are currently achievable in regenerative cryocoolers designed for cooling below 15 K. Higher operating frequencies would enable efficient low mass valveless compressors to drive the coolers. To ensure that the thermal penetration depth is much larger than the matrix depth or inter-channel thickness at operating frequencies of about 30 Hz and at porosities as low as 10%, the channel small dimension must be less than about ~50 μm (0.002 inches) for typical matrix materials. For optimum heat exchanger effectiveness the deviation of the channel small dimension must be less than about 3 % from nominal to avoid significant flow maldistribution within the matrix gas volume. A simple and cost-effective fabrication method for reproducibly constructing such a matrix is discussed in terms of preliminary flow test results and predicted thermal performance as a function of matrix porosity. The method as currently implemented produces a continuum of high aspect ratio rectangular channels along a spiral length within a thin matrix disk component. The method also enables the design of a variable porosity matrix along the regenerator temperature gradient. Preliminary flow tests with disks having nominal 38 μm flow channels are consistent with the as-measured channel dimensions and matrix geometry.
A Low Porosity Regenerator Matrix for High Frequency Low Temperature Cryocoolers
Cryocoolers 13 ; 395-404
2005-01-01
10 pages
Aufsatz/Kapitel (Buch)
Elektronische Ressource
Englisch
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