Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
  • F25B9/02—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point using Joule-Thompson effect; using vortex effect

Definitions

• This invention relates generally to refrigeration and more particularly to microminiature refrigerators which are general ⁇ ly of the type disclosed in copending applications Serial Nos. 259,687; 259,688 and 354,616.
• the refrigerators with which the present invention is concerned are Joule-Thomson refrigerators formed by a laminate of plates which are etched to provide inflow and out ⁇ flow gas channels which form a counterflow gas heat exchanger, a capillary section, boiler region and the interconnecting passages between these sections.
• Refrigerators of this type have particular utility in providing extremely low temperature cooling for chips or superconductor devices which are generally of small dimensions, for example, a centimeter square.
• the refrigerators disclosed in the aforementioned copending applications were developed for maximum efficiency in order to minimize gas flow rates required for various refrigeration capacities.
• Such applications include cooling infra red detectors in tactical missiles and precision guided munitions.
• Fast cooldown devices 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 present invention is to provide improved microminiature refrigerators of the type de ⁇ scribed which answer these requirements by providing extremely rapid cooldown.
• Fig. 1 is an exploded view of three plates which comprise the major components of the refrigerator of the present inven ⁇ tion prior to assembly.
• Fig. 2 is a central transverse section through a refriger ⁇ ator formed by the assembly of the components of Fig. 1.
• Figs. 3, 4, and 5 are views similar to Fig. 2 showing fur ⁇ ther embodiments of the present invention.
• Fig. 6 is a view similar to Fig. 2 illustrating a further embodiment of the invention which reduces thermal stress induced in the device during cooling;
• Figs. 7 and 8 are central transverse sections illustrating alternate constructions for hermetically packaging the refrig ⁇ erators of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Figs. 1 and 2 the principal components of the re ⁇ frigerator there shown are three circular plates 20, 22 and 24 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 inflow channel 26 of spiral form leading from a through input port 28 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 opening 34, the upper end of which opens into a circular recess 36 in com ⁇ munication with a series of radial channels 38, the outer ends of which are in communication with an annular channel 40 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 20 and the plate 24 overlying the plate 22.
• the plates 20, 24 are .7 inches in diam ⁇ eter and each approximately .010 inches thick.
• the inflow channel 26 is .002 inches wide and about the same in depth.
• the capillary channel 30 is typically about .002 inches wide and about .00075 inches deep.
• the other channels and ports are correspondingly dimensioned.
• 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.
• suitable gas such as nitrogen
• suitable gas such as nitrogen
• suitable gas such as nitrogen
• the compressed nitrogen passes through the inflow channel 26 to the capillary channel 30 which substantially reduces the pressure of 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
• the unit is effectivetoproduceatemperature of 90° Kelvin 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 immediate 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.
• 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.
• 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.
• 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 for exit from the device through the aligned 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 82 in the plates 58 and 56 for passage through the channels 66 and 68 for subsequent passage to the atmosphere directly through the port 69 and the channels 70.
• 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.
• 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 invention thus provides additional pre ⁇ cooling for the incoming gas to assure rapid cooldown.
• all embodiments of the invention employ the same concept of cooling the central portion of the refrig ⁇ erator in order to minimize the amount of material being cooled. This creates a large temperature gradient from the center of the refrigerator to its outside edges which remain at least initially at ambient temperatures. 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. 6 illustrates a further form of the invention incor ⁇ porating a unique configuration to eliminate the adverse effects of thermal stress.
• the refrigerator of Fig. 6 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
• OMPI IP «'- » -- - • - • - * - - enables the material in the cooled central region of the refrig ⁇ erator to contract without inducing stress in the outer region.
• refrigerators of the present invention may readily be incorporated in a hermetically sealed unit where desired.
• 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.
• 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.
• 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.
• the bottom cover member 136 may be ported as at 144 to permit the interior of the device to be evacuated or supplied with an inert gas.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)

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• 1983
  • 1983-12-01 EP EP19840900220 patent/EP0128196A4/de not_active Withdrawn
  • 1983-12-01 WO PCT/US1983/001885 patent/WO1984002177A1/en not_active Application Discontinuation

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