R. C. LONGSWORTH REFRIGERATION METHOD AND APPARATUS Filed Oct. 20. 1969 F IG. 3.
5 Sheets-Sheet 1 as 84 I g F IG. 4.
RALPH c. LONGSWORTH INVENTOR.
ATTORNEY Nov. 16, 1971 c. LONGSWORTH 3,520,029
REFRIGERATION METHOD AND APPARATUS Filed Oct. 20,1969 3- Sheets-Sheet 2 EXHAUST PRESSURE COLD VOLUME FIG. 5.
INLET PRESSURE PRESSURE SURGE VOLUME PRESSURE EXHAUST PRESSURE COLD VOLUME FIG. 6.
RALPH C. LONGSWORTH INVIL'N'I'UR.
w Xm nm ATTORNEY Nov. 16, 1971 R. c. LONGSWORTH 3,620,029
REFRIGERATION METHOD AND APPARATUS Filed Oct. 20. 1969 3 Sheets-Sheet :5
RALPH C. LONGSWORTH INVENTOR.
ATTORNEY United States Patent O 3,620,029 REFRIGERATION METHOD AND APPARATUS Ralph C. Longsworth, Allentown, Pa., assignor to Air Products and Chemicals Inc., Allentown, Pa. Filed Oct. 20, 1969, Ser. No. 867,594 Int. Cl. F25b 9/00 US. Cl. 626 13 Claims ABSTRACT OF THE DISCLOSURE There is provided a device for cooling refrigeration fluid by expansion, comprising a displacer within a closed housing, said housing communicating through an orifice to another closed chamber so that the displacer can force a fluid through the orifice thereby doing work in the refrigeration cycle and conversely, the fluid can return through the orifice to move the displacer in the opposite direction at the proper time in the cycle. The invention is characterized in that the refrigeration is accomplished in a simplified manner without auxiliary equipment such as connecting rods, crank shafts, or the like to cycle the displacer. Also disclosed is the method of producing refrigeration by directly dissipating the expander work to heat by cycling a fluid through an orifice. Cycling of the fluid through the orifice is also the operative means of actuating the displacer.
BACKGROUND OF THE INVENTION The present invention pertains to a method and apparatus for producing cryogenic refrigeration. In particular the apparatus employs a displacer that is driven by cycling a volume of a surge fluid through an orifice so that external driving means for the displacer are unnecessary. Work is expended by forcing the surge gas through the orifice into a surge volume chamber whereby the heat generated by such action can be removed by suitable heat exchange.
Devices for producing cryogenic refrigeration are disclosed in US. Pats. "2,567,454, 2,906,101, 3,074,244 and 3,321,926. These references disclose cryogenic refrigerators that cool a cryogenic fluid by expansion. The first three references require external means such as a motor with a suitable connecting rod to drive the expander. The last reference relies on a force of high pressure gas and snap-acting springs to cause cycling of the displacer.
The instant invention is an improvement over the prior art devices in that it neither requires an external driving force for the displacer nor does it require continuous high pressure gas and snap-acting spring devices to effect cycling of the displacer.
A refrigeration cycle of the type employed in the instant invention was first disclosed by Ernest Solvay in German Pat. 39,280 issued May 16, 1887. The Solvay cycle does not employ cycling of the displacer against a volume of surge gas that passes reversely through an orifice to effect cycling of the displacer. Solvay relied upon external moving forces to actuate the displacer in order to eifect refrigeration.
SUMMARY OF THE INVENTION The present invention comprises providing a volume of surge gas confined so that it can be cycled between a surge volume chamber and a chamber containing a displacer used to refrigerate or to cool a cryogenic fluid by expansion, the surge chamber and displacer chamber being connected by a small orifice so that the surge volume fluid can be forced reversably through the orifice to effect cycling of the displacer. Included in the apparatus are the necessary valves for admitting and venting the fluid to be cooled as well as regeneration devices to aid in the overall refrigeration cycle.
The refrigeration cycle disclosed is accomplished by expanding the refrigeration fluid against a volume of confining fluid similar to or other than the refrigeration fluid and separated therefrom.
Therefore, it is the primary object of this invention to provide an improved method and apparatus for producing cryogenic refrigeration.
It is still another object of the invention to provide a cryogenic refrigerator for cooling fluid by expansion wherein the displacer is not powered by external driving means.
It is yet another object of this invention to provide a cryogenic refrigerator with few moving parts.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing a first embodiment of an apparatus according to the present invention.
FIG. 2 is a schematic diagram of a second embodiment according to the present invention showing internal regeneration of the refrigeration fluid.
FIG. 3 is a schematic diagram of a two-stage displacer according to the present invention.
FIG. 4 is a schematic diagram of a different two-stage displacer according to the present invention.
FIG. 5 is a theoretical diagram of the cycle according to the present invention.
FIG. 6 is a P-V diagram of the actual cycle according to the present invention.
FIG. 7 is a cross-section diagram of a device constructed according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 there is shown a device according to the present invention comprising a fluid tight housing 10. The housing 10 comprises a first chamber 12 and a second chamber 14. Between the chambers 12 and 14 is an orifice 16. Disposed within chamber 12 is a displacer 18 with a sealing member 20 disposed near one end and surrounding the displacer 18 so that a fluid tight seal is achieved between the displacer 18 and walls of chamber 12, thereby separating the warm volume of gas from the volume of cold gas and to prevent leakage therebetween. The displacer is free to move between the bottom 22 of chamber 12 and the top 24 of chamber 12. The apparatus includes a supply of high pressure fluid (not shown) delivered through conduit 26. Disposed in conduit 26 is an inlet valve 28 for controlling the supply of high pressure fluid. Conduit 26 is in turn connected to conduit 30 which in turn is connected to a regeneration device 32 which in turn is connected to a conduit 34 and heat exchanger 36 and conduit 38 to the lower end 22 of chamber 12. The regenerator 32 is preferably a chamber containing metal screening of small aperture but can also be stacked particles of other materials such as lead spheres as iswell-known in the art.
Conduit 30 is in turn connected to an exhaust conduit 40, exhaust valve 42, heat exchanger 44 and conduit 46 serve to conduct the exhaust gas out of the system.
Deposed between the surge volume chamber 14 of housing 10 and conduit 30 is a capillary tube 48 for controlling the pressure of the surge volume chamber. The capillary tube is sized so that the pressure in the surge volume chamber is maintained approximately intermediate between the high and low pressure above the displacer 18 at either end of the cycle as will be explained subsequently.
In operation, the supply conduit 26 is connected to a source of high-pressure refrigeration fluid such as helium gas. The cycle starts with the displacer 18 in the position shown in FIG. 1 and low pressure gas in the regenerator 32. The exhaust valve 42 is closed and the inlet valve 28 is open admitting the refrigeration fluid through conduit 30 through the bottom of the housing 10. The gas causes the displacer 18 to rise until the pressure in the space 12, above the displacer 18, is equal to the pressure below the displacer 18. At this point the surge volume chamber 14, which is at an intermediate pressure deter mined by the capillary tube, begins to receive gas from above the displacer 18 through the orifice 16. This allows the displacer to rise filling the cold displaced volume with high pressure gas. The inlet valve 28 is closed when the displacer 18 reaches the top of its rise, then the exhaust valve 42 is open and the pressure underneath the displacer 18 begins to decrease. The expanding gas drops in temperature and is forced through conduit 38, heat exchanger 36, conduit 34, regenerator 32, conduit 30, conduit 40, valve 42, heat exchanger 44, and conduit 46 and away from the system. The gas leaving the cold displaced volume is lower in temperature on the average than the gas entering the volume and can thus extract heat from outside the system as it passes through heat exchanger 36. When the pressure below the displacer 18 decreases to a level less than the pressure of the surge volume chamber 14, the gas in the surge volume chamber 14 leaks back into chamber 12 forcing the displacer to the bottom 22 of the housing 10. When the displacer 18 reaches the bottom 22 of the housing 10, the exhaust valve 42 is closed, then the inlet valve 28 opened and the cycle is repeated continually thereby achieving continuous refrigeration. Heat exchanger 44 is included to remove the excess heat generated in the gas by forcing the gas through the orifice 16. The cooled gas passing out through the regenerator 32 cools the regenerator media so that the subsequently incoming gas is precooled thereby making the refrigeration capacity of the system available at a low temperature.
The capillary tube 48 is included so that the intermediate pressure of the surge volume chamber 14 is maintained at a fairly uniform level. It would be possible to replace the tube with poppet valves or other pressure control devices, however the capillary tube is preferred. The surge chamber volume is on the order of ten times greater than the displaced volume and the orifice 16 is sized so that the displacer can be cycled at any desired speed. Prior art devices employing gas pressurization or gas balancing can only be controlled by controlling the gas pressure in the incoming conduits or by using direct linkages to the displacer.
The embodiment of FIG. 2 is identical to the device of FIG. 1 except that the regenerator is contained within the displacer 18 in the area shown as 50. The cycle is identical as is the embodiment of FIG. 1 except that the fluid to be refrigerated is admitted and vented from the housing 10 through the side thereof. The incoming fluid is conducted to the regenerator 50 by conduit 52 in the displacer 18 and exited therefrom by conduit 54 to the bottom 22' of housing 10. A second annular seal 53 aids in directing the refrigeration fluid through the regenerator 50 during the inlet and exhaust portion of the cycle.
The P-V diagram shown in FIG. is an ideal cycle assuming that the displacer hits both the top 24 and bottom 22 of the chamber 12 in housing 10. However, this is not desirable since it would lead to excessive vibration of the refrigerator. Therefore, prior to hitting the top and bottom of the chamber 12, the respective valves are closed so that the displacer hits neither top nor bottom. This results in a P-V diagram as shown in FIG. 6 which is the actual cycle employed wherein the direction of the displacer is reversed prior to actually hitting either top 24 or bottom 22 of chamber 12 in housing 10.
There is shown in FIG. 3 a multiple stage refrigeration device employing a stepped dislacer 54. The displacer 54 contatins a large diameter section 56 and a small diameter section 53 and can be fabricated in a single piece. Sections 56 and 58 are disposed within complementary sections 60, 62 of housing 64 and are provided with a primary seal 66 and a secondary seal 68. The primary seal 66 prevents fluid from the Warm end from leaking to the cold end 72 of displacer section 56 while seal 68 serves to direct the gas from under displacer section 58 through regenerator 73. There is provided a separate regenerator 74 for the upper displacer section. The refrigerator of FIG. 3 is in essence two refrigerators similar to FIG. 1 joined in tandem with the important advantage of increased efficiency due to removing of heat from the refrigeration fluid in steps thereby lowering the lowest obtainable temperature. As an example the cold end temperature of displacer section 56 is about 30 K. and the cold end temperature of displacer section 58 is 6.5 to 7.0 K. Heat exchanger 44 serves to cool the surge chamber. Heat exchangers 75 and 36' provide means for using the refrigeration produced at the cold ends of displacer sections 56 and 58 respectively. The operating cycle is identical for that described in connection with FIG. 1.
It is well known that the degree of refrigeration is proportional to the volume of swept gas and that the swept volume is determined by the diameter and stroke of the displacer. FIG. 3 disclosed a method of varying the refrigeration by varying the diameter of the displacer. FIG. 4 shows another method of varying the swept volume by varying the stroke of the second stage of a two-stage displacer. In order to do this a slack coupling 76 is provided between the upper stage 78 and the lower stage 80 of the displacer 79. The operation of the device of FIG. 4 is the same as that described above for the device of FIG. 2 except that the gas is conducted to regenerator 84 of second stage 80 through a conduit 86 associated with coupling 76. The slack coupling enables a shorter stroke of section 80 in order to achieve the same refrigeration as a device of FIG. 3. Here again a minimum temperature of 6.5 to 7.0 K. can be achieved at end 88 of the refrigerator of FIG. 4. Refrigeration produced at end 88 of the refrigerator of FIG. 4 and also at end 22' of the refrigerator of FIG. 2 can be used by means of heat exchanges such as well known in the art and therefore not illustrated. One such heat exchanger is shown and described in connection with FIG. 7 below.
It is apparent from the foregoing description that the invention described above can be modified. One such modification is to add additional displacer stages with internal or external regenerators for each stage. Another modification would involve changing the displacement by varying the diameter or the stroke of the displacer either individually or together.
Shown in FIG. 7 is a cross-sectional diagram of a device actually constructed and operated according to the present invention. Referring to FIG. 7 the displacer is slidably disposed within housing 102. The displacer 100 is provided with a seal 104 so that the hot end 106 is sealed from the cold end 108 of housing 102. At the lower end of housing 102 there is provided a heat exchanger 110 for delivering the refrigeration produced by the displacer. At the upper end of housing 102 is a fluid tight cover 112 provided with an orifice 114 and filters 116. Mounted over cover 112 and in fluid tight relation thereto is a surge volume chamber housing 118 defining a surge volume chamber 120.
The displacer housing 102 and surge chamber housing are mounted on a base plate 122 to effect the fluid tight seal. Sealing members 124, 126 are provided for the displacer chamber 102 and surge chamber 118 to aid in maintaining the fluid seal with base plate 122.
Heat exchanger 110 is connected via conduit 124 to regenerator 126 mounted on base plate 122. Regenerator 126 is filled with a regenerator material 128 such as fine Wire screening. Regenerator 126 is fitted with the necessary passages 130 and 132 for conducting fluid through the regeneration chamber.
Mounted on base plate 122 above the regenerator and in fluid tight relation thereto is a valve assembly shown generally as 133 consisting of an upper housing 134 containing an inlet port 131 to be connected to a source of high pressure gas (not shown) and a lower housing 136 containing an exhaust port 137 for venting the cooled gas. Inlet port 131 communicates with chamber 138 in which is disposed rotary valve 140 for admitting gas to the system through conduit 135 and also for venting gas via port 137 in housing 136. A capillary tube 152 is connected between surge chamber 120 and conduit 135 for maintaining pressure in surge chamber 120.
Motor 146 is driven electrically by means of a source of power (not shown) delivered through electrical conduit 150. The motor 146 serves to drive the valve disc 144 to alternately admit high pressure gas to the bottom 108 of housing 102 through regenerator 128 and vent the cooled gas along the same path in accord with the refrigeration cycle described in connection with FIG. 1.
A device of the type shown in FIG. 7 was operated for 200 hours and produced 25 watts of refrigeration at 77 K. at heat exchanger 110 when operated at 144 revolutions per minute under 350/150 p.s.i.a. helium.
It is also within the scope of the inventive concept described above to provide for a separate system for maintaining the surge volume chamber at the desired temperature. This can be accomplished in any manner known to the art such as by employing a separate fluid circuit and thermostat control connected to the surge chamber.
Having thus described my invention, the following is desired to be secured by Letters Patent.
1. A refrigerator comprising:
a fluid tight housing having a generally circular crosssection; said housing divided into a displacer chamber and a fluid surge chamber with an orifice therebetween;
movably disposed within the displacer chamber, a displacer, said displacer having a cross-section configuration similar to said housing; sealing means disposed around said displacer so that the displacer chamber can have a hot end and a cold end, said hot end adjacent said fluid surge chamber;
means for admitting a stream of high pressure fluid to the cold end of said displacer chamber;
means for absorbing sensible heat generated at the hot end of said housing;
means for extracting heat from outside the housing; and
means for cycling the fluid admitted to said displacer chamber.
2. A refrigerator according to claim 1 wherein there is included means to control the surge volume pressure.
3. A refrigerator according to claim 2 wherein said regenerator includes a plurality of stacked small aperture screens.
4. A refrigerator according to claim 1 wherein the regenerator and the fluid path are disposed within the displacer.
5. A refrigerator comprising:
a fluid tight housing having a generally circular crosssection;
said housing divided into a fluid surge chamber, a first displacer chamber with an orfice therebetween and a second displacer chamber;
sealing means disposed around said first and second dipslacer sections so that the displacer chamber can have a cold end and a hot end associated with each displacer section;
means for admitting a stream of high pressure fluid to the cold end associated with each displacer section; regenerator means in circuit with said fluid means; means for absorbing sensible heat generated at said hot end of said first displacer chamber;
means for extracting heat from outside the housing;
means for cycling the fluid admitted to said displacer volumes.
6. A refrigerator according to claim 5 wherein there is included means to control the surge volume pressure.
7. A refrigerator according to claim 5 wherein said regenerator is provided with a regeneration medium selected from the group consisting of fine wire screening and metal spheres.
8. A refrigerator comprising:
a fluid tight housing having a generally circular crosssection;
said housing divided into a displacer chamber and a fluid surge volume chamber with an orifice therebetween;
movably disposed within the displacer chamber a displacer;
said displacer having a first section spaced apart from a second section and connected to it by slack coupling means;
sealing means disposed around said first and second displacer sections so that the displacer chamber can have a cold end and a hot end associated with each displacer section;
means for admitting a stream of high presure fluid to the cold end associated with each displacer section; regenerator means in circuit with said inlet fluid means; means for absorbing sensible heat generator at the hot end of such housing;
means for extracting heat from outside the housing;
means for cycling the fluid admitted to said displacer volume.
9. A refrigerator according to claim 8 wherein parts of said fluid circuit and said regenerators are included within said displacer sections.
10. A method of producing refrigeration comprising the steps of:
supplying a quantity of refrigeration fluid at a given temperature and at high pressure to a first end of an enclosed space containing a displacer;
causing the refrigeration fluid to move the displacer against a predetermined volume of a surge gas at a second end of the space until the pressure on the displacer is equalized;
continuing the supply of refrigeration fluid;
allowing the surge gas to escape through an orifice to an enclosure maintained at a constant presure so that the displacer draws in an additional quantity of gas at high pressure;
exhausting the high pressure refrigeration fluid from the enclosed space at the first end by allowing the surge gas to act on the displacer, thereby expanding and cooling the refrigeration fluid.
11. A method according to claim 10 wherein said refrigeration fluid enters said enclosed space and exits therefrom through a regenerator.
12. A method according to claim 10 wherein said cooled fluid is used to cool the surge gas chamber.
13. A method according to claim 10 wherein said supply of refrigeration fluid is controlled by an automatic timing device.
References Cited UNITED STATES PATENTS 3,045,436 7/1962 Gifford 626 3,119,237 1/1964 Giflord 6286 3,188,819 6/1965 Hogan 626 3,188,821 6/1965 Chellis 626 3,205,668 9/1965 Gifford 626 3,221,509 12/1965 Garwin 626 3,312,072 4/1967 Gifford 626 3,315,490 4/ 1967 Berry 626 3,421,331 1/1969 Webb 626 WILLIAM J. WYE, Primary Examiner US. Cl. X.R. 6286