CA1199190A - Fast cooldown miniature refrigerators - Google Patents

Fast cooldown miniature refrigerators

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Publication number
CA1199190A
CA1199190A CA000459961A CA459961A CA1199190A CA 1199190 A CA1199190 A CA 1199190A CA 000459961 A CA000459961 A CA 000459961A CA 459961 A CA459961 A CA 459961A CA 1199190 A CA1199190 A CA 1199190A
Authority
CA
Canada
Prior art keywords
refrigerator
plates
supply passage
gas
cooled
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
CA000459961A
Other languages
French (fr)
Inventor
William A. Little
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Leland Stanford Junior University
Original Assignee
Leland Stanford Junior University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leland Stanford Junior University filed Critical Leland Stanford Junior University
Priority to CA000459961A priority Critical patent/CA1199190A/en
Application granted granted Critical
Publication of CA1199190A publication Critical patent/CA1199190A/en
Expired legal-status Critical Current

Links

Abstract

ABSTRACT OF THE DISCLOSURE
A multilayer miniature low temperature rapid cooldown refrigerator in which a central cooling chamber for a device to be continuously cooled is connected to input and output refrigerant lines by micron sized channels formed in inter-faces of glass or like plates, the channels including a counterflow heat exchanger and a capillary section and the channels being so arranged as to assure rapid cooldown immediately in the region of the device to be cooled.

Description

FA.~T COOLDO~ IINIATURE REFRIGERATORS

This invention relates generally to refrigeration and more particularly to microminiature refrigerators which are aeneral-ly of the type disclosed in U. S. Patent Nos . ~,392,362 and 4,386,505.
As disclosed in greater detail in the above-identified applications the refrigerators with which the present invention is concerned are Joule-Thomson refrigerators formed bv a laminate of plates which are etched to provide inflow and out-flow ~as channels which form a counterflow gas heat exchanger,a capillary section, boiler region and the interconnecting passases between these sections. Refrigerators of this type have particular utility in providing extremely low temperature cooliny for chiPs or superconductor devices which are generally of small dimensions, for example, a centimeter square.
The refri~erators disclosed in the afore~entioned copending applications were developed for maximum efficiency in order to minimize aas flow rates required for various refrigeration capacities. There are, however, a number of cooling applica-tions which can tolerate hi~her gas flow rates to achieve theprimary objective of rapid cooldown. Such applications include cooling infra re~ detectors in tactical missiles and precision guided munitions. Fast cooldown de~ices might also be used to cool~sensitive detectors and low noise amplifiers in scientific instruments which are operated infrequently and for relatively short durations.
The principal purpose of the ~resent invention is to provide improved microminiature refrigerators of the type de-scribed which answer these re~uirements by providing extremely rapid cooldown.
It has been discovered that the limiting factor in rapid cooldown applications is the amount of heat which must be extracted from the material being cooled including the material in the refrigerator itself. In a~cordance with the present invention novel arran~ements, configurations and relationships of the inflow and outflow passages provide for maximum cooling at a small localized axea of the refrigerator.

... ..

It is a further object of the invention to provide improved microminiature refrigerators which will withstand the high vibration and acceleration forces wh:ich occur duriny launch of missiles and similar munitions.
It is a further object of the present invention to provide rapid cooldown microminiature refrigexators which can be packaged with the device to be cooled in small low cost hermetically sealed packages with internal cavities that may be evacuated or backfilled with an inert gas.
It is a further object of the present invention to provide improved East cooldown microminiature refrigerators which may be operated in normal atmosphere conditions.
Thus broadly, the invention contemplates a micro-miniature cryogenic refrigerator for cooling superconductor devices which comprises at least three plates of like thermal conductivity bonded together in pressure tight contact over an interace area to provide a stiff laminate with the plates having a central region and a peripheral region. An outermost one of the plates is adapted to carry a device to be cooled adjacent its central region, a means forming a low temperature chamber is at the central region of the laminate, a means forming a micron sized supply fluid passage is in the interface area between two of the plates connecting an input fluid port to the low temperature chamber, with the supply passage comprising a first section for conducting incoming highly compressed gas and a serially connected smaller diameter second capillary section opening into the low temperature chamber. The supply passage is of spiral configuration, and a means forming outflow passages is in another interface between two of the plates, with the outflow passages extending radially from the low temperature chamber to an exit pGrt adjacent the periphery of the refrigerator whereby the cooled gas flowing through the outflow passages is disposed in heat exchange relation with the incoming gas passing through the supply passage to effectively precool the gas passing through the supply passage.

Additional objec-ts and advantages of the present invention will become apparent as the description proceeds in connection wi-th the accompanying drawings in which:
Fig. 1 is an exploded view of three plates which comprise the major components of the refrigerator of the present inventlon prior to assembly.
Fig. 2 is a central transverse section through a refrigerator formed by the assembly of the components of Fig. 1.
Figs. 3, 4, and 5 are views similar to Fig. 2 showing further embodiments of the present invention.
Fig. 6 ls a view similar to Fig. 2 illustrating a further embodiment of the invention which reduces thermal stress induced in the device during cooling; and Figs. 7 and 8 are central transverse sections illustrating alternate constructions for hermetically packaging the refrigerators of the present invention.
DESCRIPTION OF THE PREF$RRED E~ODIMENTS
Referring now more particularly to the drawings and especially to Figs. 1 and 2 the principal components of the refrigerator there shown are three circular plates 20, 22 and 2q of glass or similar materials of low thermal conductivity having the same coefficient of thermal expansion.
Etched on the upper surface of the plate 20 is an in-flow channel 26 of spiral form leading from a through input port 23 to a central spiral capillary channel 30. The plate 20 is also provided with a through output port 32.

The plate 22 :is provided with a central through openiny 3~, the upper end of which opens into a circular recess 36 ln com-rnunication with a series of radial channels 38, the outer ends of which are in communication with an annular channel ~0 leading to an output port 42.
The plate 24, which functions as the top cover plate, has planar top and bottom surfaces.
The plates 20, 22 and 24 are assembled to form the refrig-erator as shown in Fig. 2 with the plate 22 overlying the plate 10 20 and the plate 24 overlying the plate 22.
In a typical case the plates 20, 24 are .7 inches in diam-eter and each approximately .010 inches thick. Typically the inflow channel 26 is .002 inches wide and about the same in depth. The capillaxy channel 30 is typically about .002 inches wide and about .00075 inches deep. The other channels and ports are correspondingly dimensioned.
These channels and ports in the plates 20 and 22 are pref-erably formed in the manner disclosed in detail in the aforesaid copending applications and the plates 20, 22 and 24 are sealingly 20 assembled in face-to-face contact also by the methods disclosed in these applications.
Gaseous refrigerant is supplied to the unit through an inlet tube 44 brazed or otherwise sealingly secured to a ring 46 sealingly secured to the undersurface of the plate 20 to dispose a through port 48 in alignment with the inlet port 28. The ring 46 also includes an outlet port 50 disposed in alignment with outlet ports 32 and 42 in the plates 20 and 22, the port 50 leading to a suitable outlet tube 52.
In operation, suitable gas, such as nitrogen, is supplied 30 to the inlet tube 44 at pressure in the range of 6,000 psi.
The compressed nitrogen passes through the inflow channel 26 to the capillary channel 30 which substantially reduces the pressure o~ the gas and produces the desired cooling, maximum cooling being effected in the region of the port 34 and the recess 36 which is located immediately beneath the device 54 to be cooled which is mounted centrally on the upper surface of the plate 24. The cooled gas then passes through the radial channels 38 in heat exchange relation with the incoming gas passing through the channel 26 and the capillary channel 30 to precool the incoming gas, further accelera~ing the cooldown rate. The gas then exits from the devlce to any convenient point of disposal.
The u~it is effectivetoproduceatemperature of 90~elvin in a few seconds after start-up, this temperature being achieved in the region of the port 34 and the recess 36, which, as noted above, is in the il~mediate region of the device 54 to be cooled.
A wide range of compressed gases can be used to achieve different cooldown rates for a range of minimum temperatures.
In the modified form of the invention shown in Fig. 3 the unit includes plates 55 and 56 similar to the plate 20, a plate 58 similar to the plate 22 and a modified top plate 60.
As in the previously described embodiment the plate 55 has a spirally arranged inflow passage 62 connected to a capillary section 64 and the plate 56 has a similar inflow passage 66 and capillary passage 68. The top plate 60 has a central through opening 69 which is vented to atmosphere through a series of radial channels 70 positioned immediately beneath the device 54.
In operation, gas flows from the inlet tube 44 through the passages 62 and 64 to a central port 72 in the plate 58 thence through radial channels 74 ~or exit from the device through the ali~ned outlet ports 76 and 78, thus cooling the central portion of the refrigerator unit. Additionally, a portion of the gas passes through aligned ports 80 and ~2 in the plates 58 and 56 for passage throuc~h the channels 66 and 68 ~or subsequent passage to the atmosphere directly through the port 69 and the channels 70.
Since the pressure of the gas as it leaves the capillary section 68 determinesthe minimum operating temperature of the refrigerator this embodiment of invention achieves the lowest possible operating tepmerature in the region of device 54.
The embodiment of Fig. 4 comprises a plate 84 similar to the plate 20 having a spiral inflow passage 86 and a capillary section 88, a top panel 24, a modified intermediate plate 89 and a bottom plate 90.
On operation, gas under pressure is supplied through sui~-able ports to the inflow channei 86, a portion of the gas then ,,i. ~
'.i~

passing through capillary section 88 thence through a central port 100 and radial channels 102 for passage through aligned outlet ports to the outlet tube 52. Additionally, a portion of the gas entering the capillary section 88 is tapped off through a port 4~ for passage through a relatively wide annular channel 106 to the exterior of the device. In this embodiment of the invention the incoming gas in channel 86 is effectively precooled by its passage in heat exchange relation with the cooled gas passing through the radial channels 102 and the annular channel 106.
The embodiment of Fig. 5 is similar to the embodiment of Fig. 4 and includes an additional plate to provide for addition-al precooling of the incoming gas. More specifically, the unit of Fig. 5 includes a top plate 24, an intermediate plate 89, a central plate 20 and lower plates 107 and 108, the latter having an inflow section 109 and a capillary section 110. The operation of the device of Fig. 5 is essentially the same as that of Fig.
4 except that a portion of the gas is delivered through the alternate inflow passage 109 and the capillary passage 110 for passage through a port 112 to radial channels 114 formed in the upper surface of plate 107 thence to the exterior of the device.
This embodiment of the in~ention thus provides additional pre-cooliny for the incoming gas to assure rapid cooldown.
~ s previously noted, all embodiments of the invention employ the san~e concept of cooling the central portion of the refrig-erator in order to minimi~e the amount of material being cooled.
This creates a large temperature gradient from the center of the reErigerator to its outside edges which remain at least initially at ambient temperaturesO This temperature gradient may produce severe stress in the refrigerator plates as the cooled central material attempts to contract while the warmer outer areas resist this contraction.
Fig. ~ illustrates a further form OI the invention incor-porating a unique configuration to eliminate the adverse effects of thermal stress. The refrigerator of Fig. ~ comprises three plates 120, 122, and 124 which are identical to the previously described plates 20, 22 and 24 except that the plates, at least in their central region, are upwardly convex~ This configuration enables the material in the cooled central region of the refrig-erator to contract without inducing stress in the outer region.
As noted above the refrigerators of the present invention may readily be incorporated in a hermetically sealed unit where desired.
E'or example, as shown in Fig. 7 an upper ring 126 sealingly secured to the upper surface of the plate 24 carries a top cover plate 128 to form a sealed space about the device 54.
Electrical leads 130 are printed or similarly deposited on the upper surface of the plate 24 and lead to the exterior of the device. Similarly a bottom cover plate 132 is sealingly secured to the lower surface of the ring 46 to complete the incapsula-tion of the entire refrigerator. The bottom plate 132 is provi-ded with a port 134 which permits the interior of the device to be evacuated or to be filled with an inert gas as desired.
In the embodiment of Fig. 8 a suitably apertured bottom cover plate 136 is sealingly secured to the lower surface of the plate 20 in lieu of the ring 46 previously described. The sealed housing for the unit of Fig. 8 is completed by an annular wall member 138 and a top cover member 140 suitably sealingly secured together. The electrical leads 142 for the device 54 may be conducted to the exterior of the housing through the bottom wall 136 as shown. As in the previously described embodiment the bottom cover member 136 may be ported as at 1~ to permit the intexior of the device to be evacuated or supplied with an inert ~as.
In each of the embodiments of Figs. 7 and 8 the refrigerator per se are supported around their outside perimeters which results in a rigid structure capable of withstanding the high vibration and shock forces which exist during the launch of tactical missiles and precision guided munitions.
The invention may be embodied in other specific forms with-out departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended calims rather than by the foregoing description~ and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (7)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A microminiature cryogenic refrigerator for cooling superconductor devices comprising at least three plates of like thermal conductivity bonded to-gether in pressure tight contact over an interface area to provide a stiff laminate, said plates having a central region and a peripheral region, an outermost one of said plates being adapted to carry a device to be cooled adjacant its central region, means forming a low temperature chamber at said central region of said laminate, means forming a micron sized supply fluid passage in the interface area between two of said plates connecting an input fluid port to said low temperature chamber, said supply passage comprising a first section for con-ducting incoming highly compressed gas and a serially connected smaller diameter second capillary section opening into said low temperature chamber, said supply passage being of spiral config-uration, and means forming outflow passages in another interface between two of said plates, said outflow passages extending radially from said low temperature chamber to an exit port adjacent the periphery of said refrigerator whereby the cooled gas flowing through said outflow passages is disposed in heat exchange re-lation with the incoming gas passing through said supply passage to effectively precool the gas passing through said supply passage.
2. The refrigerator according to claim 1 together with an additional plate, means forming a second supply passage in the interface between said additional plate and an adjacent plate, said additional supply passage being connected in parallel with said first mentioned supply passage and including a spirally arranged supply section serially connected to a spirally arranged smaller diameter capillary section, and means connecting the outlet end of said capillary section of said additional supply passage to conduct the cooled gas exiting therefrom to the exterior of the device in the region of the device to be cooled.
3. The refrigerator according to claim 1 together with additional passage means for conducting a portion of the gas delivered to said capillary section to the exterior of said device in heat exchange relation with the incoming gas passing through said supply passage.
4. The refrigerator according to claim 1 wherein said plates are circular in form and are upwardly convex in their central region.
5. The refrigerator according to claim 1 together with means forming a hermetically sealed housing enclosing said refrigerator.
6. The refrigerator according to claim 5 wherein said housing is provided with a port by which the housing may be evacuated or supplied with an inert gas.
7. The refrigerator according to claim 5 wherein said housing is directly secured to said refrigerator at a peripheral region thereof to provide structural support for said refrigerator.
CA000459961A 1984-07-30 1984-07-30 Fast cooldown miniature refrigerators Expired CA1199190A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA000459961A CA1199190A (en) 1984-07-30 1984-07-30 Fast cooldown miniature refrigerators

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA000459961A CA1199190A (en) 1984-07-30 1984-07-30 Fast cooldown miniature refrigerators

Publications (1)

Publication Number Publication Date
CA1199190A true CA1199190A (en) 1986-01-14

Family

ID=4128417

Family Applications (1)

Application Number Title Priority Date Filing Date
CA000459961A Expired CA1199190A (en) 1984-07-30 1984-07-30 Fast cooldown miniature refrigerators

Country Status (1)

Country Link
CA (1) CA1199190A (en)

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