US3257823A - Expansion and liquefying apparatus employing the joule-thomson effect - Google Patents

Description

June 28, 1966 w. H. HOGAN 3,257,823

EXPANSION AND LIQUEFYING APPARATUS EMPLOYING THE JOULE-THOMSON EFFECT Filed June 17. 1964 HIGH-PRESSURE INITIALLY COOLED FLUID FROM REFRIGERATOR LOW PRESSURE FLUID TO REFRIGERATOR 1 l 1 28 gg I9 25 7 25 28 g 3| 26 -25 A as 43 35 5? --29 42 33 4a 3e i N2 23 47 so 44 F|g.7

INVENTOR. 6 Walter H. Hogun Attorney many liquefying apparatus.

United States Patent i 3,257,823 EXPANSION AND LIQUEFYING APPARATUS EM- PLOYING THE JOULE-THOMSON EFFECT Walter H. Hogan, Wayland, Mass., assignor to Arthur D.

Little, Inc., Cambridge, Mass., a corporation of Massa- Filed June 17, 1964, Ser. No. 375,722 5 Claims. (Cl. 62467) This invention relates to an apparatus suitable for liquefying a cold gas through expansion and more particularly to an improved Joule-Thomson valve.

The liquefaction of a cold, high-pressure gas through expansion to a lower pressure has long been known and so-called Joule-Thomson valves are regularly used in These valves are normally an integral part of the refrigeration apparatus and as such are constructed within the refrigerator or are directly connected to it. (See for example U.S.P. 2,716,333 which describes an apparatus for the liquefaction of helium and employs a Joule-Thomson valve of the prior art type to efiect the final liquefaction.) In typical liquefying apparatus it is necessary to draw offthe liquefied gas from the liquefier to store it in a suitable vessel such as a dewar, or to remove it for refrigeration purposes so that it might effect out-of-contact heat exchange with an external load. This in turn means that the liquefied gas must be continuously or periodically removed from the liquefier and transferred as a liquid into a suitable storage vessel or heat exchanger. In some liquefiers the capacity may be such that this removal and transfer of the liquefied gas must be accomplished relatively often, thus requiring that an attendant be present to monitor the liquefaction process and to perform the transfer of the liquefied gas to the storage vessel periodically. In the absence of such an attendant the liquefier can be run only long enough to fill the liquid storage container within the liquefier to capacity. This means that the liquefier must be shut down and then started again which in turn nor mally requires a cool-down period. It would therefore be desirable to have available a Joule-Thomson valve which could be operated outside a refrigerator and be inserted directly into a storage vessel or an external load, eliminating the necessity for periodic transfer of the liquefied gas from the liquefier. This would then enable a refrigerator or liquefier to run continuously unattended until the storage vessel was 'full or contained the desired amount of liquid.

Liquefaction of a gas at a point remote from the environment in which the gas has been precooled by out-ofcontact heat exchange is not merely a matter'of placing a Joule-Thomson valve in its prior art form in a storage vessel, or the like, and connecting it with a suitable fluid conduit. An expansion-liquefaction valve used at a remote point must be associated with an efiicient heat exchanger which etfects out-of-contact heat exchange between the cold high-pressure gas which is to be liquefied and the returning even colder low-pressure gas which did not liquefy in the storage vessel or which boiled off from the stored liquefied gas. Thus, such a valve must be one which is capable of being turned off to seal all of the gas and fluid passages while the refrigerator continues operation.

This in turn requires a Joule-Thomson valve in which there is a double closure in order that no outside air may leak in or any internally circulated gas (e.g., helium) may leak out. Thus it is necessary to be able in the Joule- Thomson valve itself to close both lines to and from the refrigerator including the high-pressure and the low-pressure fluid lines. It should be pointed out that although while still operating the refrigerator.

the Joule-Thomson valve of this invention is particularly suited for accomplishing liquefaction at a point remote Patented June 28, 1966 from the normal heat exchange environment and initial gas expansion, it is also suitable for incorporation in a refrigerator or a liquefier.

It is therefore a primary object of this invention to provide an improved Joule-Thomson valve which can be used externally of a refrigerator to liquefy gas at a point remote from the refrigerator. It is another object of this invention to provide a Joule-Thomson valve of the character described which can be accurately controlled at a point remote from the actual point of liquefaction. It is another object of this invention to provide such Joule- Thomson valve which can be closed in order that both the low-pressure and high-pressure passages of the lines delivering and returning the fluid can be effectively closed thus making it possible to close the Joule-Thomson valve Another object is to provide an improve Joule-Thomson valve which is efficient in expanding cold high-pressure gas and liquefying it. It is yet another object to provide an improve Joule- Thomson valve which is capable of liquefyinghelium.

Other objects of the invention will in part be obvious and will in part be apparent hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth and the scope of the invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to the following detailed description taken in connection with the accompanying drawings in which FIG. 1 is a cross-section of the Joule-Thomson valve constructed in accordance with this invention showing the valve in a partly opened condition;

FIG. 2 is a cross-section of the valve of FIG. 1 along FIG. 3 is a cross-section of the valve of FIG. 1 along line 33;

FIG. 4 is a cross-section of the valve of FIG. 1 along line 44;

FIG. 5 is a cross-section of the valve of FIG. 1 alon line 55;

FIG. 6 shows the lower portion of the valve in a fully closed position; and

FIG. 7 shows the lower portion of the valve in a fully opened position.

In the use of the Joule-Thomson valve of this invention high-pressure gas flows up out of the refrigerator or liquefier, which is not a part of this invention, through a vacuum insulated dual concentric flow passage tube with a Joule-Thomson valve located on the end .of the transfer tube. This tube is inserted in a suitable dewar and the Joule-Thomson expansion and liquefaction takes place within the dewar. The valve has a spring loaded selfcentering needle and is designed so that in the fully closed position not only the supply circuit but also the return passage is shut off. This prevents contaminating fluids from entering the system when the tubeis removed from the helium dewar. The valve adjustment is accomplished by means of an adjusting head which is so arranged as to result inan effective sixty turns per inch and therefore a fine degree of adjustment.

The valve transfer tube and adjustment mechanism are:

shown in cross-section in FIG. 1. It is presumed that a portion of the transfer tube and the valve are within the dewar as shown by a fragmentary cross-section of the mouth of the dewar 10. The tube is held within the dewar and'temporarily sealed thereto through a flexible joining member 11 which may conveniently be an elastic collar. 7

The transfer tube itself consists of an inner high-pressure tube 12 which defines a high-pressure fluid passage 13. Concentric with tube 12 and surrounding it is lowpressure tube 14 which with tube 12 defines an annular passage 15 through which the cold low-pressure fluid is returned for out-of-contact heat exchange with the incoming high-pressure fluid. Surrounding this low-pressure return tube 14 is an outer tubing 16 which with this lowpressure tube defines a concentric annular insulation space 17 which is evacuated. This evacuation is achieved by means not shown and this insulation may extend the length of the liquid transfer tube, i.e., from the refrigerator to the beginning of the Joule-Thomson valve. Finally, surrounding the entire transfer tube is an outer adjusting sheath 18 which with the outer Wall of the transfer tube 16 forms an annular passage 19 extending the length of the sheath and terminating at the point where the adjusting means is located as will be described below.

The annular space 17 is sealed by plug 22 to make it vacuum tight. The bottom portion within this insulation space contains absorbing charcoal 23. Inasmuch as this space 17 is maintained at a very cold temperature by virtue of its being surrounded on both sides by cold gas, some cryopumping takes place and the charcoal serves as an absorbent surface for any of the gases which are solidified within the evacuated space.

Attached to plug 22 is the upper end of the main valve seat 25 which will be seen to extend downwardly and to terminate in an elongated narrow extension 26 which has a very small diameter high-pressure channel 27 in fluid communication with and effectively sealed to the highpressure fluid line 13. As will be seen in FIGS. 1 and 2 the main valve seat 25 has two radial ports 28 which permit the entrance of the cold low-pressure fluid into the low-pressure return passage 15 as will be described in more detail below. Joining the main valve seat 25 and extension 26 is a conicalsection 29.

The remaining portion of the Joule-Thomson valve is an extension of the sheath 18. It consists of a sheath plug 30 which defines with the main valve seat 25 an annular passage 31 which in turn is in fluid communication with radial ports 28 in the main valve seat 25. The sheath plug also defines an annular passage ,33 with the main valve seat extension 26 and access to passage 33 from the interior 36 of the dewar is afforded by means of radial passages (FIGS. 1 and 3) in plug 30. The closable passage 34, which is between the conical section 29 of the main valve seat 25 and shoulder 37 of the sheath plug, completes the path by which cold low-pressure gas can be returned from the dewar to the refrigerator by means of annular passage 15.

In the central portion of the sheath plug 30 is a narrow channel 40 in which the valve seat extension 26 is movable. Channel 40 opens into a chamber 41 drilled in the plug. The outer portion of the upper wall of chamber 41 provides a force applying ring 42, the purpose of which will subsequently be made apparent. Two radial grooves 43 (see FIG. 4) are cut in the upper wall of chamber 41 and two narrow passages 44 are cut along opposite sides of the chamber to provide a conduit for liquefied gas into the storage dewar vessel (see FIG. 5). Chamber 41 is closed at its lower end, except for the two passages, by a threaded end plug 46.

i The needle 47 of the valve, the up and down movement of which controls the opening and closing of the passage 27 and hence the expansion and liquefaction of the gas, is mounted on a horizontal base which can be brought into force applying relationship with the force applying ring 42. A vertical support and aligning means 49 is in effect an extension of base 48, and is slidably movable through end plug 46. A spring 50 is located within chamber 41 and is adapted to apply an upward force against the bottom of needle base 48 to cause the needle to engage the valve seat except when the valve is forced open.

If desired, a diffuser 51 may be afiixed to the end of the plug to provide separation of liquefied and unliquefied gas. The diffuser illustrated in FIG. 1 contains bronze 4 wool 52 for this purpose and it is held within the difiuser by means of a foraminous retaining member 53 (e.g., screen) which permits the liquid and gas to flow through it.

Adjustment of the Joule-Thomson valve and its opening and closing are controlled through the sheath 18 fixed to the end plug 30 which contains the needle portion of the valve. The movement of plug 30 and its associated components must be only up and down without effecting any rotation. This movement is done through the use of the adjusting mechanism illustrated in FIG. 1. This comprises first a threaded collar 55 which is permanently affixed to the sheath 18. Inasmuch as the annular passage 19 is closed it is necessary to provide a suitable sealing ring 56 within the collar 55 so that the sheath may be moved up and down and still maintain a fluid-tight seal for annular space 19.

A similar threaded collar 58 is permanently aflixed to the tubing 16 and associated with the two threaded collars is a threaded adjusting ring 59. The threads on the collar 58 which is attached to the tubing 16 are 14 threads per inch while those which are on the threaded collar 55 permanently aflixed to the sheath 18 are 18 threads per inch. It will be appreciated that when the threaded adjusting ring 59 is turned the net result is to obtain extremely fine adjustments in the upward and downward movement of the sheath. This particular combination is the equivalent of one adjusting ring having 60 threads per inch which makes very fine adjustments possible. It is not of course practical to cut 60 threads per inch, but the differential between the threads in collar 58 and in collar 55 makes possible extremely fine adjustment of the sheath and hence of the movement of the needle within the valve seat. FIG. 6 illustrates the I oule-Thomson valve of this invention in a completely closed condition. It will be noted that under these circumstances the sheath has been raised to its uppermost position with respect to the remaining portion of the transport tube assembly and shoulder 37 of the sheath plug 30 engages the conical wall 29 of the main valve seat 25. This in effect closes off passage 34 which communicates by way of passage 31 and radial ports 28 into the low-pressure return channel 15. Therefore no cold, low-pressure gas can be returned to the system by way of annular passage 15 and no contaminating gas can enter the low-pressure side of the transfer tube or the annular channel 19. Simultaneously needle 47 is completely engaged by the opening in channel 27 to block off channel 27 so that no high-pressure gas can pass through to be expanded and liquefied. This means that no cold high- -pressure gas can leak out. In the closed condition illustrated in FIG. 6, the transfer tube and expansion valve may be removed from the dewar without having to shut off the refrigerator.

In the condition illustrated in FIG. 1 it is possible for low-pressure cold gas to return to the refrigerator from the interior of the dewar by way of radial passage 33, closable passage 34, annular passage 31, radial passages 28 and thence into the annular low-pressure cold gas return passage 15. Under these conditions although liquefaction is not taking place the out-of-contact heat exchanger made up of the various channels of the transfer tube is being maintained in its cold condition so that when high-pressure cold gas is again introduced by way of inner passage 13 into the small passage 27 to be liquefied it will require little if any cooling down.

Finally FIG. 6 illustrates the condition which obtains when the valve is fully open and liquefaction is taking place. It will be seen that it is possible then for the highpressure cold fluid to flow through passage 13 into passage 27 and out around the needle 47 for further expansion and liquefaction. Under these circumstances the liquefied gas, along with any unliquefied gas, passes down through grooves 43 and 44 to enter the interior 36 of the dewar. That portion of the gas which is liquefied accumulates in the dewar while the cold low-pressure gas which is not liquefied, or which has boiled off in the dewar, is returned through the transfer tube and the Joule- Thomson heat exchanger by means of radial passages 35 as explained in conjunction with the description of FIG. 1.

An important feature of the valve system of this invention is that both the high-pressure and low-pressure sides are opened by a positive action, thus always insuring accurate and reliable control over the fluid flow.

It will therefore be seen that there is provided a unique Joule-Thomson valve which is capable of being inserted into a suitable container such as a dewar vessel for liquefaction of a gas remote from the point at which the first cooling takes place. The Joule-Thomson valve is also so constructed as to make it possible to close it and remove it from the dewar or to cease liquefaction while retaining the valve and the out-of-contact' heat exchanger transfer tube in a cold condition thus requiring essentially no cool down before liquefaction is begun again. Further the Joule-Thomson valve of this invention provides for extremely fine adjustments of the valve which is important in this type of liquefaction.

Although the Joule-Thomson valve of this invention may be used with any cryogenic apparatus capable of supplying high-pressure, cold fluid to it, it is particularly suitable for use with the cryogenic liquefier described in copending application Serial No. 375,854 filed in the names of Robert W. Stuart, Fred F. Chellis and Walter H. Hogan and assigned to the same assignee as this application.

It will thus be seen that the objects set forth above among those made apparent from the preceding description are efficiently attained and, since certain changes may be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

I claim:

1. An apparatus suitable for expanding and liquefying a high-pressure cold gas at a point remote from the refrigerator in Which said gas was initially cooled, comprising in combination (a) a transfer-heat exchanger tube adapted at one end for attachment to a refrigerator to deliver initially cooled high-pressure gas from said refrigerator to said remote point and to return cold low pressure gas from said remote point in out-of-contact heat exchange with said high-pressure gas, comprising,

(1) an inner high pressure channel,

(2) an annular low-pressure passage surrounding said high-pressure channel, and

(3) an outer tube defining an annular insulating channel surrounding said low-pressure passage; (b) an adjusting sheath surrounding at least a portion of said transfer-heat exchanger tube and extending to its other end;

(0) a valve seat permanently affixed to said transferheat exchanger tube, having a small diameter highpressure channel in fluid communication with said inner-high pressure channel of said tube and radial fluid ports communicating with said annular lowpressure passage of said tube;

((1) a .plug surrounding a-t-least a portion of said valve seat .adapted to seal said sheath and to define with said valve seat a fluid passage into said annular lowpressure passage of said tube via said radial fluid ports, said fluid passage being closable by the movement of said sheath relative to said tube, and said plug having radial passages communicating between the volume surrounding it and said closable fluid passage;

(e) a needle operable within said plug and adapted for movement to open and close said small diameter highpressure channel in said valve seat to provide with it a controllable expansion valve;

(f) means within said end plug for moving said needle;

(g) fluid passage means adapted to discharge liquefied and cold expanded gas to a liquid collection zone;

(b) means for moving said adjusting sheath with respect to said transfer-heat exchanger tube whereby the movement of said needle is effected and the flow of fluid is regulated through said closable fluid pas- -sage.

2. Apparatus in accordance with claim 1 including a spring adapted to exert a force upon said needle to close said small diameter high-pressure channel, and wherein said means for moving said needle comprises means for applying -a positive force, opposed to the force exerted by said spring, when said adjusting sheath is moved to i open said closable fluid passage.

3. Apparatus in accordance with claim 1 wherein said .valve seat has a conical section and said plug has a shoulder engageable with said conical section of said valve seat thereby-in their engaged position to eflect closing of said closable passage. V

4. Apparatus in accordance with claim 1 wherein said means for moving said adjusting sheath with respect to said transfer-heat exchange tube comprises (a) a first threaded collar aflixed to the end of said adjusting sheath and movable in fluid-tight contact along the outer surface of said annular insulating channel to seal the passage between said tube and said sheath;

(b) a second threaded collar aflixed to said outer tube above said first threaded collar and having a lesser number of threads per inch than said first threaded collar; and

(c) an adjusting ring having a first threaded portion adapted to turn on said first collar and a second threaded portion adapted to turn on said second collar thereby to provide precise movement of said adjusting sheath with respect to said transfer-heat exchange tube and to open and close said high-pressure channel and low pressure passage in said tube.

5. Apparatus in accordance with claim 1 including a diffuser associated with said fluid passage means adapted to discharge liquefied and cold expanded gas.

References Cited by the Examiner UNITED STATES PATENTS 2,909,908 10/1959 Pastulov 62-5l4 MEYER PERLIN, Primary Examiner.

Claims (1)

1. AN APPARATUS SUITABLE FOR EXPANDING AND LIQUEFYING A HIGH-PRESSURE COLD GAS AT A POINT REMOTE FROM THE REFRIGERATOR IN WHICH SAID GAS WAS INITIALLY COOLED, COMPRISING IN COMBINATION (A) A TRANSFER-HEAT EXCHANGER TUBE ADAPTED AT ONE END FOR ATTACHMENT TO A REFRIGERATOR TO DELIVER INITIALLY COOLED HIGH-PRESSURE GAS FROM SAID REFRIGERATOR TO SAID REMOTE POINT AND TO RETURN COLD LOW-PRESSURE GAS FROM SAID REMOTE POINT IN OUT-OF-CONTACT HEAT EXCHANGE WITH SAID HIGH-PRESSURE GAS, COMPRISING, (1) AN INNER HIGH-PRESSURE CHANNEL, (2) AN ANNULAR LOW-PRESSURE PASSAGE SURROUNDING SAID HIGH-PRESSURE CHANNEL, AND (3) AN OUTER TUBE DEFINING AN ANNULAR INSULATING CHANNEL SURROUNDING SAID LOW-PRESSURE PASSAGE; (B) AN ADJUSTING SHEATH SURROUNDING AT LEAST A PORTION OF SAID TRANSFER-HEAT EXCHANGER TUBE AND EXTENDING TO ITS OTHER END; (C) A VALVE SEAT PERMANENTLY AFFIXED TO SAID TRANSFERHEAT EXCHANGER TUBE, HAVING A SMALL DIAMETER HIGHPRESSURE CHANNEL IN FLUID COMMUNICATION WITH SAID INNER-HIG PRESSURE CHANNEL OF SAID TUBE AND RADIAL FLUID PORTS COMMUNICATING WITH SAID ANNULAR LOWPRESSURE PASSAGE OF SAID TUBE; (D) A PLUG SURROUNDING AT LEAST A PORTION OF SAID VALVE SEAT ADAPTED TO SEAL SAID SHEATH AND TO DEFINE WITH SAID VALVE SEAT A FLUID PASSAGE INTO SAID ANNULAR LOWPRESSURE PASSAGE OF AID TUBE VIA SAID RADIAL FLUID PORTS, SAID FLUID PASSAGE BEING CLOSABLE BY THE MOVEMENT OF SAID SHEATH RELATIVE TO SAID TUBE, AND SAID PLUG HAVING RADIAL PASSAGES COMMUNICATING BETWEEN THE VOLUME SURROUNDING IT AND SAID CLOSABLE FLUID PASSAGE; (E) A NEEDLE OPERABLE WITHIN SAID PLUG AND ADAPTED FOR MOVEMENT TO OPEN AND CLOSE SAID SMALL DIAMETER HIGHPRESSURE CHANNEL IN SAID VALVE SEAT TO PROVBIDE WITH IT A CONTROLLABLE EXPANSION VALVE; (F) MEANS WITHIN SAID END PLUG FOR MOVING SAID NEEDLE; (G) FLUID PASSAGE MEANS ADAPTED TO DISCHARGE LIQUEFIED AND COLD EXPANDED GAS TO A LIQUID COLLECTION ZONE; (H) MEANS FOR MOVING SAID ADJUSTING SHEATH WITH RESPECT TO SAID TRANSFER-HEAT EXCHANGER TUBE WHEREBY THE MOVEMENT OF SAID NEEDLE IS EFFECTED AND THE FLOW OF FLUID IS REGULATED THROUGH SAID CLOSABLE FLUID PASSAGE.

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