Secondary pulse tubes and regenerators for coupling to room temperature phase shifters in multistage pulse tube cryocoolers
a multi-stage pulse tube and regenerator technology, applied in gas cycle refrigeration machines, refrigeration machines, lighting and heating apparatus, etc., can solve the problems of large cryocooler, low efficiency of 4 k cryocooler, noisy compressors with high input power,
Inactive Publication Date: 2015-01-29
GOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SEC OF COMMERCE THE NAT INST OF STANDARDS & TEHCNOLOGY
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Benefits of technology
The present invention provides improved systems and methods for pulse tube refrigeration and cooling. The invention addresses previous problems and drawbacks associated with previously known systems.
Problems solved by technology
The low efficiency of 4 K cryocoolers causes these cryocoolers to have large, noisy compressors with high input powers.
The low operating frequency of the GM and GM-type pulse tubes also leads to large temperature oscillations at the cold end at the operating frequency of the cryocooler.
However, these higher frequencies generally lead to greater losses in a 4 K regenerator unless the operating parameters are near optimum conditions.
Inertance tubes are typically used for phase shifting, but with the small refrigeration powers of interest for electronics cooling, phase shifts of only a few degrees are possible at 30 Hz, even with the inertance tube and reservoir at a low temperature of 30 K. A double inlet configuration with a secondary orifice between the regenerator and pulse tube warm ends can only provide a practical phase shift of about 30° before the lost work in the secondary orifice greatly reduces the overall efficiency.
The double inlet approach also introduces the possibility of DC flow, which can reduce the efficiency.
Method used
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[0022]The present invention is based, at least in part, upon a discovery that by incorporating a secondary regenerator or a secondary pulse tube at a warm end (but still below room temperature) of a pulse tube, a phase shifter or expander in a pulse tube cooling system can be operated at room temperature. Furthermore, it has been discovered that a wide array of commercially available pressure oscillators can be used for the room temperature phase shifter or expander. These and other aspects are described in greater detail herein.
[0023]Generally, multistage pulse tube cryocoolers require separate phase shifters for each stage. For sufficiently high frequency and acoustic power, an inertance tube is typically used for such phase shifting. For Stirling-type multistage pulse tube cryocoolers, the warm end of the coldest pulse tube is often heat sunk to the cold end of a warmer stage rather than at room temperature to improve the figure of merit for the pulse tube and / or to achieve a lar...
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Pulse tube refrigeration or cooling systems are described which utilize a secondary regenerator or a secondary pulse tube. Use of such a secondary regenerator or pulse tube enables a commercially available pressure oscillator to be incorporated in the cooling system. The commercially available oscillator can be operated at room temperature or approximately so.
Description
[0001]The present invention is a divisional application and claims priority upon U.S. Ser. No. 13 / 012,040, filed Jan. 24, 2011 and it relates to pulse tube cooling systems and particularly, room temperature operation of pressure oscillators used in such systems.FIELD OF THE INVENTIONBackground of the Invention[0002]Small 4 K cryocoolers for the cooling of low temperature superconducting (LTS) electronic systems are necessary for broader commercial, military, or space applications of such devices. Typically these cryocoolers have been either Gifford-McMahon (GM) cryocoolers or GM-type pulse tube cryocoolers that operate at frequencies of about 1 Hz. The efficiency of these cryocoolers ranges from 0.5 to 1.0% of Carnot, whereas 80 K cryocoolers often achieve efficiencies of about 15% of Carnot. The low efficiency of 4 K cryocoolers causes these cryocoolers to have large, noisy compressors with high input powers. The low operating frequency of the GM and GM-type pulse tubes also leads ...
Claims
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IPC IPC(8): F25B9/14
CPCF25B9/145F25B9/06F25B9/10F25B2309/1406F25B2309/1407F25B2309/1411F25B2309/1413F25B2309/1426
InventorRADEBAUGH, RAYGARAWAY, ISAACBRADLEY, PETER E.
OwnerGOVERNMENT OF THE UNITED STATES OF AMERICA AS REPRESENTED BY THE SEC OF COMMERCE THE NAT INST OF STANDARDS & TEHCNOLOGY