US3729946A

US3729946A - Cryogenic liquid handling system

Info

Publication number: US3729946A
Application number: US00146903A
Authority: US
Inventors: A Massey
Original assignee: Individual
Current assignee: Individual
Priority date: 1971-05-26
Filing date: 1971-05-26
Publication date: 1973-05-01
Anticipated expiration: 1990-05-01

Abstract

A cryogenic liquid handling system for infrared detection or the like having a cryogenic liquid supply container which is insulated in part by the flow of cryogenic vapor existing above the liquid level, a two phase flow generator in the container, a heated delivery line to maintain the two phase flow and a separator at the point of use, including a vapor feedback passage to prevent the formation of frost in the lens of the infrared detection system.

Description

llnited States Patent 11 1 Massey 1 May 1, 1973 [5 CRYOGENIQ LIQUID HANDLING 3,006,157 10/1961 Haettingeret a]. ..62/DlG. 19 SYSTEM 3,120,600 2/1964 True ..I38/32 x 3,122,004 2/1964 Abe le ..62/D1G. 19 Inventor: Alton y, 485 Fries Road, 3,126,711 3/1964 M11121 ..62/55 x Tonawanda, NY 14150 3,203,477 8/1965 Collard ..62 259 [22] Filed: y 26, 1971 3,548,607 12/1970 Plllsbury, Jr. et a1 ..62/52 [21] Appl. No.: 146,903 Primary Examiner-Meyer Perlin Assistant ExaminerR0nald C. Capossela 52 us. c1. ..62/51, 62/55, 138/33, Mama-Allen "affe 62/128, 62/514, 62/DIG. 19 51 1111. C1. ,.Fl7c 7/02 [57] ABSTRACT [58] Field of Search ..62-/50.l, 514, 55, A cryogenic liquid handling system for infrared detec- 3 tion or the like having a cryogenic liquid supply container which is insulated in part by the flow of [5 R f r n es C t cryogenic vapor existing above the liquid level, a two phase flow generator in the container, a heated UNITED STATES PATENTS delivery line to maintain the two phase flow and a 3,418,822 12/1968 Massey ..62 55 p at r at t point of u ng a ap r f d- 3,378,673 4/1968 back passage to prevent the formation of frost in the 2,707,377 5 lens of the infrared detection system. 3,258,602 6/1966 2,244,635 6/1941 Williamson, Jr ..l38/103 21 Claims, 1 Drawing Figure Patented May 1, 1973 3,729,946

v CONTROL 2;

" 8 INVENTOR.

AmNAMmY ATTORNEY.

1 CRYOGENIC LIQUID HANDLING SYSTEM BACKGROUND OF THE DISCLOSURE The present invention relates to fluid handling systems and, more particularly, to an improved cryogenic fluid handling system. In my prior US. Pat. No. 3,418,822 a system is disclosed for transporting a stream of cryogenic liquified gas which is based on the Leidenfrost phenomena. According to the teachings of my prior patent, the cryogenic liquified gas is transported through a flexible or semi-rigid conduit without the usual deterioration thereof due to the low temperatures of the liquified gas. This is accomplished by converting a portion of the cryogenic liquid into a gaseous phase which surrounds the remaining liquid creating separate liquid spheroids which are propelled through the conduit by the gas. Near the point of use the gas is separated from the liquid spheriods whereby the liquid can be employed for its intended cooling purposes such as cryogenic surgery or infrared detection or the like.

The creation of the gas-liquid or two phase flow is accomplished. by the application of heat in the conduit near the source of cryogenic liquid supply. Once the two phase flow is created it must be maintained. In my prior patent the maintenance of such flow is accomplished by the heat added to the conduit by the environment. Thus, my prior system must be designed with a precise knowledge of the environment for most efficient operation. Should environmental conditions change either in temperature or pressure, the efficiency of my prior system is significantly effected. For example, if the temperature increases more gas phase is produced resulting in less usable liquid. Should the environmental temperature decrease significantly, as it would in space applications, less heat is supplied by the environment to the conduit which, in turn, supplies less heat to the vapor phase thereby reducing the shielding effect for the liquid spheroids. These spheriods would thus come into contact with the relatively hot conduit walls and would vaporize. This action would repeat until most of the liquid has vaporized and little or no liquid would be left to perform a useful cooling function. Additionally, since the conduit walls looses heat to the spheroids and the vapor, the temperature thereof is reduced until its low temperature properties are reached, whereupon deterioration takes place. It is therefore necessary for efficient operation of the system that the heat added to the conduit must be just that necessary for the maintenance of the two phase flow in just the right proportions; where the environmental conditions change it is not possible with my prior system to achieve such a balance.

SUMMARY OF THE INVENTION The foregoing disadvantages, as well as other, of prior systems are overcome according to the teachings of the present invention which provides an improved cryogenic fluid handling system that is simple, efficient, inexpensive, independent of environmental conditions, versatile and noise-free.

According to one aspect of the present invention a nonvacuum insulated cryogenic supply container incorporates a heat shield in the form of a heat exchanger having one end in communication with the vapor space in the container and the other end in communication with the environment whereby a portion of the heat from the environment is absorbed before it reaches the cryogenic supply container.

According to a second aspect of the invention, the cryogenic container itself incorporates means to generate the Leidenfrost flow in the form of a heater cooperating with structure which guides the cryogenic liquid spheriods and the transporting gas vapor through the supply line.

Additionally, the present invention provides thermostatically controlled means for heating the supply conduit means substantially along the entire length thereof from the supply container to a point of use, whereby the Leidenfrost flow is maintained and the conduit is completely protected from freezing along the entire extent thereof, independent of the particular environmental conditions under which the cryogenic system is operating.

The present invention also incorporates means for separating the liquid spheroids from the transporting or propelling vapor, which means is located at the point of use. Thus, no portion of the conduit means is subject to direct contact with the cryogenic liquid and the resulting frost which would be caused by such contact.

The present invention further provides means to prevent the formation of frost at the structure to be cooled by the cryogenic fluid at the point of use.

Further objects, features and advantages of the present invention will become apparent as the description thereof proceeds.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of the present invention, reference should be had to the following detailed description thereof taken in conjunction with the accompanying drawing wherein the only FIGURE is a schematic of the cryogenic handling system with parts thereof illustrated in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, the cryogenic supply apparatus is generally depicted by the numeral 10 and comprises a supply or storage container 12 fabricated of any suitable material, metallic or nonmetallic. Container 12 is surrounded by a layer 14 of a highly reflective material which functions as a radiation shield. Container l2 and layer 14 are suitably embedded in or surrounded by an insulating material 16 which may be urethane or any other suitable material.

Interiorly of container 12 is a chamber 18 in which is stored a cryogenic fluid 20 such as liquid nitrogen, hydrogen or the like. The vapor phase of the cryogenic liquid is located in volume 22 above the liquid level.

A supply conduit 24 delivers cryogenic fluid from a suitable source of supply (not illustrated) to chamber 18 through delivery valve 26, a coiled heat shield or heat exchanger tubing 28 embedded in insulation 16, and a delivery tube 30 communicating with the vapor space in chamber 18. Conventional

level sensing probes

32 and 34 are located in chamber 18 for developing high and low level signals via lines 36 and 38, respectively, to control the actuation of valve 26 to maintain a substantially constant level of liquid in container 12. Of course, valve 26 may be manually controlled, if desired.

Heat exchange means in the form of a coiled heat shield or tubing 40 embedded in insulation 16 has one end in communication with a vent conduit 42 located in the vapor space of chamber 18; the tubing 40 has its other end in communication with the environment at 44 through a pressure control and relief valve 46 of conventional construction. Valve 46 functions to maintain a predetermined back pressure in the chamber 18.

A cryogenic fluid outlet conduit 48 has one end in communication with a delivery valve 50 adjacent the exterior of apparatus 10. The other end of conduit 48 communicates with a Leidenfrost flow generator depicted generally by the numeral 52. Conduit 48 passes through coil 28 in heat exchange relation therewith. The portion of conduit 48 interiorly of chamber 18 is wrapped with a suitable insulating material 54.

The Leidenfrost generator 52 comprises a conically flared or funnel shaped input 56 adjacent the bottom surface of container 12; the narrow end section 58 of which is in communication with outlet conduit 54, the wide end section 60 of which is in communication with the cryogenic liquid via a plurality of slots or openings 62. A suitable heater 64 is located adjacent end section 60 in a recess 66 in insulation 16. Heater 64 may be of conventional construction such as one of the resistance heating type, for example.

A suitable baffle 68 is mounted to the wall of container 12 to prevent turbulence of the incoming cryogenic fluid from interfering with the generation of the liquid spheroid flow through generator 52.

A delivery conduit 70 is in communication with the outlet of valve 50 for supplying cryogenic fluid to a point of use depicted generally as 72. Conduit 70 may be flexible, semi-rigid or rigid and must be protected against deterioration by the freezing effects of the low temperature cryogenic flow. To this end, heating means 74 is provided in the form ofa resistance heating wire or coil 76 which is spirally wrapped about the conduit 70 along substantially the entire extent thereof from apparatus 10 to point of use 72. As illustrated schematically, the space between adjacent coils of wire 76 progressively increases from the valve 50 toward the point of use 72. Thus, the quantity of heat supplied to conduit 70 by the heating wire progressively decreases. The amount of heat required and the exact spacing of the coils will be dictated by the operating conditions as would be known to those skilled in the art.

Although a heating wire coil has been disclosed, other forms of heating means can be employed. For example, axially extending resistance elements can be embedded about the peripheral surface of the conduit. These elements can be sized differently to achieve the different heat inputs along the length of the conduit.

One or more heat sensing means, which may comprise thermostats 78 or the like, are provided in heat exchange relationship with conduit 70. Signals from thermostats 78 are transmitted by lines 80 to a heater control switch or the like 82 which actuates heater 64 via line 84 and heating wires 76 via lines 86.

Point of use 72 may typically comprise an insulated cryogenic fluid container in the form of a dewar or flask 88 which is closed by a suitable cap or stopper 90, through which pass an inlet tube 92, a vent tube 94 and a level sensing probe 96. inlet tube 92 communicates with and may be considered a part of conduit 70.

Mounted interiorly of container 88 is a spheroidvapor separator in the form of a conical collector 98 having an upper wide mouthed section 100 tapering into a lower narrow mouthed section or opening 102. The arrangement is such that the cryogenic liquid spheroids S drop through opening 102 whereas the lighter propelling gas vapor passes through vent tube 94. The sphereoids passing through opening 102 collect and form a volume of cryogenic liquid 106, the level of which is maintained by valve 50 in response to a signal from level sensor 96 via line 108.

Located adjacent the cryogenic liquid 106 and in heat exchange relationship therewith is the material to be cooled, which may typically comprise a light sensitive detector 110 such as an infrared detector. A spaced observation window or lens 112 is provided for allowing the sensed light to fall upon detector 110.

Vent tube 94 communicates with a conventional relief and regulator valve 114 which maintains a predetermined back pressure in dewar 88. After passing through valve 114 the vent vapor is delivered via tube 116 to the space-between detector 110 and lens 1 l2 and thence to waste via line 118.

OPERATION In operation, cryogenic liquid is delivered to chamber 18 via tube 30 through coil 28 until probe 32 makes contact with the liquid, at which time valve 26 closes. Valve 26 is reopened to deliver more liquid when the level drops to the height of probe 34. The cryogenic vapor in space 22 is exhausted through tube 42 and heat exchanger coils 40 through valve 46. Since this vapor is still at a much lower temperature than the environment, the vapor will absorb heat from the environment before transmission to the container 12. Thus, the coils 40 effectively function as a heat shield which, together with the insulation 16 and the reflective layer 14, prevents substantial temperature increases in the container 12.

The application heat from heater 64 adjacent funnel 56 causes the cryogenic liquid to form a two phase or Leidenfrost flow consisting of liquid spheroids S and a propelling cryogenic vapor which flow is guided and directed upwardly through funnel 56, insulated section 54, section 48 and valve 50 to delivery conduit 70.

To maintain the two phase flow through conduit 70 a controlled amount of heat must be supplied thereto. This is accomplished by the heating coils 76, which function under the influence of thermostats 78 and heater control 82 to supply just the right amount of heat to the conduit to maintain the proper balance between the liquid spheroid and vapor phase flowing therethrough. Since some heat may be supplied by the environment, the amount of heat supplied by coils 76 is variable with environmental conditions. it is however important to note that changing environmental conditions can be easily accommodated by simply varying the heat output of the coils as by changing the thermostat settings; thereby adding significantly to the versatility of the present system.

As the liquid spheroids are propelled downstream in conduit 70 they absorb heat from the surrounding transporting vapor, which in turn absorbs heat from the conduit walls due to the heat supplied from the coils 76. To prevent the establishment of a too large vapor to spheroid volume, it is necessary that less and less heat be supplied further and further downstream of valve 50. Thus, the spacing between adjacent heating coils progressively increases from a minimum at valve 50 to a maximum at dewar 88. The exact spacings will depend upon the temperatures that are to be maintained at the outer peripheral surface of conduit 70 which, in turn, are a function of particular system design and particular environmental conditions as would be known to those skilled in the art. It has been found that conduit outer wall temperatures in the range of 35F to 100F are suitable.

Upon entry into dewar 88 the two phase flow is separated; the heavier liquid spheroids falling by gravity through funnel 98 and puddling into a cryogenic liquid volume 106, whereas the lighter vapor rises through vent tube 94.

The volume of cryogenic liquid in dewar 88 is employed to cool material 110 which might typically comprise an infrared detector, which responds to rays impinging thereupon through window or lens 112. For proper operation, it is imperative that the lens 112 be free of frost so that transparency thereof is maintained. To this end, the exhausted propelling vapor is passed through conduit 116 to the space between the detector 110 and the lens 112. Since this gas vapor is substantially heated to environmental temperature before it reaches the space between detector 110 and lens 112, the vapor functions to maintain this space at or near environmental temperatures. The existenceof the same temperature on both sides of lens 112 will prevent the formation of frost.

Although a preferred embodiment of the present invention has been disclosed. and described, changes will obviously occur to those skilled in the art. It is therefore intended that the scope of the present. invention is to be limited only by the scope of the appended claims.

What is claimed is:

l. A cryogenic liquid handling system, comprising;

a. storage means for containing a cryogenic fluid,

b. conduit means for conveying said cryogenic fluid from said storage means to a point of use,

c. spheroid generator means for developing cryogenic liquid spheroids surrounded by a gas vapor for propelling said spheroid through said conduit means, and

d. means for maintaining the flow of said spheroids surrounded by said gas vapor along substantially the entire extent of conduit means from said storage means to said point of use, said means comprising first heater means for supplying heat to said conduit means along substantially the entire extent thereof from said storage means to said point of use.

2. The system according to claim 1, wherein;

e. said spheroid generator means is located in said storage means.

3. The system according to claim 1, further comprise. insulating means surrounding said storage means,

and

f. heat exchange means embedded in said insulating means for communicating the vapor space of said storage means to the environment whereby heat from said environment is absorbed by said heat exchange means to prevent its absorbtion by said storage means.

4. The system according to claim 1, wherein;

e. said first heater means is attached to said conduit 5 means in such a manner that the heat added thereto progressively decreases from a maximum at said storage means end to a minimum at said point of use end.

5. The system according to claim 4, wherein;

10 f. said first heater means comprises a plurality of resistance heating elements in surrounding relation to said conduit means.

6. The system according to claim 5, wherein; l 5 g. said heating elements are helically wrapped about said conduit means. 7. The system according to claim 6, further compriss;

h. heat sensing means responsive to the temperature of said conduit means, and

i. heater control means for'actuating said first heater means in response to signals from said heat sensing means. 8. The system according to claim 1, further comprise. heat sensing means responsive to the temperature of said conduit means, and

f. heater control means for actuating said first heater means in response to signals from said heat sensing means.

9. The system according to claim 8, wherein;

g. said first heater means is attached to said conduit means in such a manner that the heat added thereto progressively decreases from a maximum at said storage means end to a minimum at said point of use end.

10. The system according to claim 1, wherein;

c. said spheroid generator means comprises a flared frusto-conical opening in communication with said conduit means and second heater means adjacent said opening.

11. The system according to claim 10, further comprising;

f. heat sensing means responsive to the temperature of said conduit means, and

g. heat control means for actuating said first and second heater means in response to signals from said heatsensing means.

12. The system according to claim 11, wherein;

h. said first heater means is so related to said conduit means that the heat added thereto progressively decreases from a maximum at said storage means end to a minimum at said point ofuse end.

13. The system according to claim 12, wherein;

i. said first heater means comprises a plurality of resistance heating elements in surrounding relation to said conduit means.

14. The system according to claim 13, wherein;

j. said heating elements are helically wrapped about said conduit means.

15. The system according to claim 1, further com- 65 prising;

e. means for separating said liquid spheroids from said gas vapor at said point of use.

16. The system according to claim 15, wherein;

f. said means for separating comprises a funnel shaped member having an opening at the lowermost portion thereof for collecting by gravity the heavier liquid spheroids and a vent tube above said funnel shaped member for allowing the lighter gas I vapor to escape therethrough.

17. The system according to claim 1, wherein;

e. said point of use comprises a cryogenic liquid container adapted to cool an infrared detector, and there is further provided;

f. means in said container for separating said cryogenic liquid spheroids from said gas vapor.

18. The system according to claim 17, wherein;

g. said means for separating comprises a funnel shaped member having an opening at the lowermost portion thereof for collecting by gravity the heavier liquid spheroids and a vent tube above said funnel shaped member for allowing the lighter gas vapor to escape therethrough.

19. The system according to claim 18, further comprising;

h. an infrared detector assembly in heat exchange relation with said cryogenic liquid container, said assembly comprising;

i. an infrared detector,

j. a lens spaced from said detector, and wherein;

k. said vent tube communicates with the space between said detector and said lens whereby the temperature in said space is brought to substantially that of the environment to prevent the formation of frost on said lens.

20. A cryogenic liquid handling system, comprising;

a. a cryogenic liquid container,

b. a light sensitive detector in heat exchange relationship with said container,

c. transparent means spaced from said detector for transmitting light thereto,

d. a vent tube communicating with said container and the space between said detector and said transparent means whereby the temperature in said space is brought to substantially that of the environment to prevent the formation of frost on said transparent means and e. a funnel shaped separator in said container having and opening at the lowermost portion thereof for collecting by gravity cryogenic liquid flowing into said container.

21. A cryogenic liquid handling system, comprising;

a. a cryogenic liquid container,

b. conduit means communicating with said container for delivering liquid spheroids surrounded by a gaseous vapor to said container,

0. a funnel shaped separator in said container having an opening at the lowermost portion thereof for collecting by gravity said liquid spheroids, and

d. a vent tube communicating with said container for permitting said gaseous vapor to escape.

i II

Claims

1. A cryogenic liquid handling system, comprising; a. storage means for containing a cryogenic fluid, b. conduit means for conveying said cryogenic fluid from said storage means to a point of use, c. spheroid generator means for developing cryogenic liquid spheroids surrounded by a gas vapor for propelling said spheroid through said conduit means, and d. means for maintaining the flow of said spheroids surrounded by said gas vapor along substantially the entire extent of conduit means from said storage means to said point of use, said means comprising first heater means for supplying heat to said conduit means along substantially the entire extent thereof from said storage means to said point of use.

2. The system according to claim 1, wherein; e. said spheroid generator means is located in said storage means.

3. The system according to claim 1, further comprising; e. insulating means surrounding said storage means, and f. heat exchange means embedded in said insulating means for communicating the vapor space of said storage means to the environment whereby heat from said environment is absorbed by said heat exchange means to prevent its absorbtion by said storage means.

4. The system according to claim 1, wherein; e. said first heater means is attached to said conduit means in such a manner that the heat added thereto progressively decreases from a maximum at said storage means end to a minimum at said point of use end.

5. The system according to claim 4, wherein; f. said first heater means comprises a plurality of resistance heating elements in surrounding relation to said conduit means.

6. The system according to claim 5, wherein; g. said heating elements are helically wrapped about said conduit means.

7. The system according to claim 6, further comprising; h. heat sensing means responsive to the temperature of said conduit means, and i. heater control means for actuating said first heater means in response to signals from said heat sensing means.

8. The system according to claim 1, further comprising; e. heat sensing means responsive to the temperature of said conduit means, and f. heater control means for actuating said first heater means in response to signals from said heat sensing means.

9. The system according to claim 8, wherein; g. said first heater means is attached to said conduit means in such a manner that the heat added thereto progressively decreases from a maximum at said storage means end to a minimum at said point of use end.

10. The system according to claim 1, wherein; e. said spheroid generator means comprises a flared frusto-conical opening in communication with said conduit means and second heater means adjacent said opening.

11. The system according to claim 10, further comprising; f. heat sensing means responsive to the temperature of said conduit means, and g. heat control means for actuating said first and second heater means in response to signals from said heat sensing means.

12. The system according to claim 11, wherein; h. said first heater means is so related to said conduit means that the heat added thereto progressively decreases from a maximum at said storage means end to a minimum at said point of use end.

13. The system according to claim 12, wherein; i. said first heater means comprises a plurality of resistance heating elements in surrounding relation to said conduit means.

14. The system according to claim 13, wherein; j. said heating elements are helically wrapped about said conduit means.

15. The system according to claim 1, further comprising; e. means for separating said liquid spheroids from said gas vapor at said point of use.

16. The system according to claim 15, wherein; f. said means for separating comprises a funnel shaped member having an opening at the lowermost portion thereof for collecting by gravity the heavier liquid spheroids and a vent tube above said funnel shaped member for allowing the lighter gas vapor to escape therethrough.

17. The system according to claim 1, wherein; e. said point of use comprises a cryogenic liquid container adapted to cool an infrared detector, and there is further provided; f. means in said container for separating said cryogenic liquid spheroids from said gas vapor.

18. The system according to claim 17, wherein; g. said means for separating comprises a funnel shaped member having an opening at the lowermost portion thereof for collecting by gravity the heavier liquid spheroids and a vent tube above said funnel shaped member for allowing the lighter gas vapor to escape therethrough.

19. The system according to claim 18, further comprising; h. an infrared detector assembly in heat exchange relation with said cryogenic liquid container, said assembly comprising; i. an infrared detector, j. a lens spaced from said detector, and wherein; k. said vent tube communicates with the space between said detector and said lens whereby the temperature in said space is brought to substantially that of the environment to prevent the formation of frost on said lens.

20. A cryogenic liquid handling system, comprising; a. a cryogenic liquid container, b. a light sensitive detector in heat exchange relationship with said container, c. transparent means spaced from said detector for transmitting light thereto, d. a vent tube communicating with said container and the space between said detector and said transparent means whereby the temperature in said space is brought to substantially that of the environment to prevent the formation of frost on said transparent means and e. a funnel shaped separator in said container having and opening at the lowermost portion thereof for collecting by gravity cryogenic liquid flowing into said container.

21. A cryogenic liquid handling system, comprising; a. a cryogenic liquid container, b. conduit means communicating with said container for delivering liquid spheroids surrounded by a gaseous vapor to said container, c. a funnel shaped separator in said container having an opening at the lowermost portion thereof for collecting by gravity said liquid spheroids, and d. a vent tube communicating with said container for permitting said gaseous vapor to escape.