WO2008086407A2

WO2008086407A2 - Apparatus for transferring fluid under cryogenic conditions

Info

Publication number: WO2008086407A2
Application number: PCT/US2008/050606
Authority: WO
Inventors: Alexandre N. Terentiev; Sergey Terentyev
Original assignee: Levtech, Inc.
Priority date: 2007-01-09
Filing date: 2008-01-09
Publication date: 2008-07-17
Also published as: WO2008086407A3

Abstract

An apparatus is provided for intended use in agitating a fluid under cryogenic conditions. In one embodiment, the apparatus includes a fluid-agitating element for placement in contact with the fluid. The fluid-agitating element includes a superconductor, and a motive device is provided for causing the fluid-agitating element to agitate the fluid. In the case where fluid pumping is the desired outcome, an associated vessel may be provided including an inlet for receiving the fluid and an outlet for discharging the fluid as a result of the action of the fluid- agitating element. Related methods are also described, as is an impeller for use in connection with fluids under cryogenic conditions.

Description

APPARATUS FOR TRANSFERRING FLUID UNDER CRYOGENIC CONDITIONS

This application claims the benefit of U.S. Provisional Patent App. Ser. No. 60/884,047, filed January 9, 2007, the disclosure of which is incorporated herein by reference.

Technical Field

The present invention relates generally to fluid processing and, more particularly, to an apparatus for agitating a fluid under cryogenic conditions.

Background of the Invention

A number of applications exist in which process fluids, and especially liquids, must be transferred (e.g., pumped) from one location or vessel to another while maintained under cryogenic conditions. For example, re-circulation of liquid nitrogen at a temperature of about 77 Kelvin is necessary in environmental chambers simulating the low temperatures of outer space. Likewise, recirculating liquid/gaseous Helium at around 4 Kelvin is necessary for cooling superconducting magnets widely used in particle accelerators. Liquid hydrogen at approximately 20 Kelvin is considered as potential fuel for vehicles in the near future. This application would require storage, transportation and distribution infrastructures including hydrogen pumping stations, which could be used to fill vehicles with liquid hydrogen.

Despite these commercially important applications, the pumping of cryogenic fluids such as liquid nitrogen, liquid helium, liquid hydrogen as well as the same substances in the gaseous form presents a challenge. Pumps incorporating standard seals and mechanical bearings generally cannot operate in a cryogenic environment, at least not without a significant reduction in their service life. Drive shafts penetrating into the pumping chambers also result in the heat influx into the cryogenic fluid, enhancing the boiling-off rate of the liquid cryogenic gases.

Accordingly, a need exists for a reliable apparatus capable of pumping extremely cold or cryogenic fluids, and especially those in the range of about 2 Kelvin to about 90 Kelvin.

Summary of the Invention In accordance with a first aspect of the invention, an apparatus for intended use in agitating a fluid under cryogenic conditions is provided. The apparatus comprises a vessel for receiving the fluid and the fluid-agitating element. A fluid-agitating element for placement in contact with the fluid includes a superconductor. A motive device is also provided for causing the fluid- agitating element to agitate the fluid, such as for example by rotating as the result of a magnetic coupling. As a result of the positioning in the cold fluid, the superconductor of the fluid-agitating element may be brought to a transition temperature in which levitation is induced in trie presence of an external magnetic field. Preferably, the vessel includes an inlet for receiving the fluid and an outlet for discharging the fluid. Most preferably, an upper portion of the vessel comprises the inlet and a lower portion of the vessel comprises the outlet.

The superconductor of the fluid-agitating element preferably includes an opening, and is most preferably arranged in an annular configuration. Although not required, it is also preferable to include one or more blades in order to enhance the level of fluid-agitation created if the fluid-agitating element is rotated.

In one embodiment, the motive device comprises a rotary motor for rotating a plurality of driving magnets forming a magnetic coupling with the superconductor. Preferably, the plurality of driving magnets have opposite polarities adjacent the superconductor of the pumping or mixing element. Most preferably, at least six driving magnets are provided, arranged in a circumferential configuration.

The apparatus may further include a stability magnet for forming a magnetic coupling with the superconductor. This stability magnet is preferably arranged such that it creates a symmetrical magnetic field. The stability magnet may be positioned internal or external to the vessel, and may optionally receive the vessel or be affixed to it.

In another aspect of the invention, the apparatus is provided for intended use in pumping a fluid under cryogenic conditions. This apparatus includes a vessel including an inlet for receiving the fluid and an outlet for discharging the fluid. A pumping element is provided for placement in the vessel in contact with the fluid. The pumping element includes a superconductor maintained at or below a transition temperature by the fluid. A motive device external to the vessel creates a magnetic field for forming a first magnetic coupling with the superconductor and causing the pumping element to agitate the fluid. The apparatus may optionally include a stability magnet for forming a second magnetic coupling with the superconductor of the pumping element.

In accordance with another inventive aspect, an apparatus for agitating fluids under cryogenic conditions is provided. The apparatus comprises an impeller including a superconductor.

Yet a further inventive aspect disclosed herein is a method of pumping or mixing a fluid under cryogenic conditions. In its broadest terms, the method comprises agitating the fluid using a fluid-agitating element comprising a superconductor. The method preferably includes the step of field cooling the superconductor using the fluid before the agitating step. Most preferably, the agitating step comprises rotating the fluid-agitating element via a magnetic coupling with motive device external to a vessel for receiving the fluid. The method may still further include the step of positioning a stabilizing magnet so as to form a magnetic coupling with the superconductor and further enhance the stability of the fluid-agitating element. Brief Description of the Drawings

Figure 1 is a partially schematic, partially cross-sectional side view illustrating one apparatus especially adapted for use for agitating a fluid under cryogenic conditions;

Figures 2a and 2b are side and top views illustrating possible arrangements of driving magnets for use in connection with the apparatus of Figure 1 ;

Figure 3 schematically illustrates another embodiment of an apparatus especially adapted for use for agitating a fluid under cryogenic conditions Figures 4a and 4b schematically illustrate different stability magnet arrangements for use in connection with the embodiment of Figure 3;

Figure 5 illustrates yet another embodiment of an apparatus especially adapted for use for agitating a fluid under cryogenic conditions.

Detailed Description of the Invention

One particularly preferred embodiment of an apparatus 10 for use in connection with transferring (e.g., pumping) a fluid F (e.g., gases, mixtures of gases, liquids, mixtures of liquids, or combinations of any of the foregoing) under cryogenic conditions is illustrated in Figure 1. For purposes of this disclosure, the term "cryogenic conditions" encompasses those conditions under which an involved fluid is sufficiently cool to bring, hold and maintain a superconductor at or below a transition temperature in order to induce it to levitate in the presence of an externally applied magnetic field. Examples of fluids that may require agitation under such conditions in the course of regular usage include, but are not limited to, hydrogen, helium, or nitrogen maintained at least partially in a liquid state at respective temperatures between about 90 Kelvin, or around -183 Celsius, to about 2 Kelvin, or around -271 Celsius.

In the illustrated embodiment, the apparatus 10 comprises a vessel 12 for receiving the selected fluid F under cryogenic conditions. Preferably, the vessel 12 comprises an interior compartment for the fluid F during transfer, as well as an inlet 12a in an upper portion for receiving the fluid (such as from an upstream source) and an outlet 12b in a lower portion for discharging the fluid (such as to a downstream location (e.g., a tank) for storage or use). The vessel 12 may be formed of any rigid material, such as stainless steel, plastic, fiberglass, or the like, and may optionally include a vacuum jacket (not shown) for providing insulation from the ambient environment. One or more refrigerators (not shown) may also be provided for cooling the fluid during transfer.

Positioned in the interior compartment of the vessel 12 is a fluid-agitating element 14 adapted to contact and transfer the fluid F. This element 14 includes a superconductor 14a, and most preferably one fabricated from melt-textured Yttrium-Barium-Copper oxide (YBCO) or like materials capable of levitating in the presence of a magnetic field once field cooled and maintained at or below a transition temperature (e.g., 77 Kelvin, in the case of YBCO). Preferably, the superconductor 14a forms the support base of the pumping or mixing element 14 and most preferably, comprises one or more pieces of material arranged circurnferentially with an opening in a center region so as to create an annular configuration (note cross-hatching in Figure 1 of sectional superconductor 14a). The fluid-agitating element 14 may optionally further include one or more blades 14b, but may alternatively include vanes or like structures capable of improving or enhancing the degree of fluid agitation provided (in which case, the fluid-agitating element 14 may be considered an impeller incorporating a superconductor).

External to the vessel 12, a motive device 16 which serves to drive the fluid-agitating element 14 within the interior compartment to pump, mix, or otherwise agitate the fluid F. Preferably, the coupling is by way of magnetic attraction, which advantageously avoids the need for a shaft projecting into the vessel, corresponding dynamic seals or bearings, and concomitant exposure to the ambient environment. To achieve such a non-contact coupling, the motive device 16 may include a plurality of driving magnets 16a . . . 16n for forming a magnetic coupling with the superconductor 14a of the fluid-agitating element 14 through at least one wall of the vessel 12 (and, most preferably, the lower wall or floor, as illustrated). These driving magnets 16a . . . 16n may be supported by a support structure 18 preferably mounted for rotary movement and coupled by a coupler, such as an elongated shaft 20, to a motor 22 (e.g., a variable speed electric motor) or other source of kinetic energy such as a piston. The arrangement of driving magnets 16a . . . 16n is such that an asymmetric magnetic field is created for forming the coupling with the superconductor 14a of the fluid-agitating element 14. As shown in the schematic side view of Figure 2a, this may be achieved by providing at least two driving magnets 16a, 16b that, in use, present alternating polarities adjacent to the superconductor 14a (that is, one with the "north" pole facing the superconductor 14a and the other in opposite orientation). Most preferably, at least six alternating polarity magnets 16a-16f are provided, arranged in a circumferential fashion as shown in Figure 2b (N - north; S- South), to enhance the transmission of torque to and overall rotational stability of the fluid-agitating element 14. As should be appreciated, the driving magnets 16a . . . 16n may be embedded in a suitable (preferably, non-magnetic) inert matrix material, and may be of any known type (including, for example, Neodymium Iron Boron permanent magnets). Alternatively, instead of using driving magnets, it is also possible to create the desired alternating or asymmetrical magnetic field using an electromagnet with windings to which current is supplied.

In operation, the fluid F under cryogenic conditions is introduced into the interior compartment of the vessel 12. This fluid F contacts the fluid-agitating element 14 when present and thus cools the superconductor 14a to at or below the temperature of transition to a superconducting state, or the "transition temperature" (again, for YBCO, approximately 77 Kelvin). To ensure the fluid F is held in the interior compartment, a valve (not shown) may be associated with the outlet 12b and temporarily closed.

During this cooling, the drive magnets 16a . . . 16n preferably are temporarily positioned slightly (e.g., 1-10 mm) farther away from the corresponding side of the vessel 12 than would be the case in the normal operating position. In any case, the cooling of the superconductor 14a in the presence of the magnetic field causes the superconductor to "trap" the magnetic field generated by the driving magnets 16a . . . 16n.

After the field cooling is complete, the driving magnets 16a . , . 16n may then be moved closer to the corresponding sidewall of the vessel 12 in order to levitate the superconductor 14a, and hence the fluid-agitating element 14, within the interior compartment. The motor 22 or like device may then be used to move the driving magnets 16a . . . 16n in a synchronous fashion (clockwise or counterclockwise, in the case of rotation) to transmit torque to the fluid-agitating element 14 and created the desired pumping or mixing action in the surrounding fluid F. In the case where the vessel 12 includes an inlet 12a and outlet 12b (for which any valve closed during field cooling may be opened), the fluid-agitating element 14 thus pumps the fluid F.

In some situations, such as where the fluid is viscous, the torque requirement is otherwise high to achieve a particular degree of agitating, or otherwise where stability or reliability arc of particular concern, it may be desirable to further enhance the "stiffness" of the levitating fluid-agitating element 14. Turning to Figures 3, 4a-4b, and 5, one manner of achieving this object is to provide a stability magnet 24 which is capable of forming a second magnetic coupling with the superconductor 14a. This stability magnet 24 is preferably positioned external to the vessel 12, and may in one possible embodiment include an opening O (such as in the center of the annular structure shown in Figure 3) for receiving a portion of it.

The stability magnet 24 preferably produces a symmetric magnetic field relative to the axis of rotation of the fluid-agitating element 14. To achieve this, the magnetization vector V of the stability magnet 24 can be arranged to extend in a direction aligned with the axis of rotation A of the fluid-agitating element 14, as shown in Figure 4a. Alternatively, the magnetization vector V may extend in the radial direction (i.e., transverse) relative to axis A, as shown in Figure 4b. The stability magnet 24 may also be positioned in the interior compartment of the vessel 12, as shown in Figure 5, which lessens the gap between it and the fluid-agitating element 14 and improves the strength of the magnetic coupling formed therebetween. Preferably, the positioning is such that the stability magnet 24 is adjacent to and concentric with the superconductor 14a when levitated. This may be achieved by using a stability magnet 24 with an opening having an inner diameter greater than the outer diameter of at least the superconductor 14a of the fluid-agitating element 14. As should be appreciated, the stability magnet 24 may be affixed in place, such as by attaching it to a sidewall of the vessel 12.

In any case, it is preferable to move (e.g., lower in the illustrated embodiments) the stabilizing magnet 24 slightly during the process of field cooling. In the Figure 3 embodiment, this may be achieved by moving the stabilizing magnet 24 relative to the vessel 12, such that it is adjacent to the superconductor 14a during field cooling. The stabilizing magnet 24 may then be moved along with the driving magnets 16a . . . 16n to levitate the superconductor 14a, and hence, the fluid- agitating element 14 within the interior compartment of the vessel 12. In the Figure 5 embodiment where the stability magnet 24 is positioned inside the vessel 12 and thus creates a much smaller gap, this relative movement is unnecessary to achieve an acceptable magnetic coupling with the superconductor 14a.

The foregoing descriptions of various embodiments have been presented for purposes of illustration and description. These descriptions are not intended to be exhaustive or to limit the invention to the precise forms disclosed. The embodiments described provide the best illustration of the principles of the invention and its practical applications to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.

Claims

In the Claims

1. An apparatus for agitating a fluid under cryogenic conditions, comprising: a vessel for receiving the fluid; a fluid-agitating element for placement in contact with the fluid, said fluid- agitating element comprising a superconductor; and a motive device for causing the fluid-agitating element to agitate the fluid.

2. The apparatus of claim 1, wherein the vessel includes an inlet for receiving the fluid and an outlet for discharging the fluid.

3. The apparatus of claim 2, wherein an upper portion of the vessel comprises the inlet and a lower portion of the vessel comprises the outlet.

4. The apparatus of claim 1 , wherein the superconductor of the fluid- agitating element includes an opening.

5. The apparatus of claim 1, wherein the fluid-agitating element includes one or more blades.

6. The apparatus of claim 1, wherein the motive device comprises a rotary motor for rotating a plurality of driving magnets for forming a magnetic coupling with the superconductor.

7. The apparatus of claim 1, wherein the plurality of driving magnets have opposite polarities adjacent the superconductor of the pumping or mixing element.

8. The apparatus of claim 8, wherein at least six driving magnets are provided, arranged in a circumferential configuration.

9. The apparatus of claim 1, further including a stability magnet for forming a magnetic coupling with the superconductor.

10. The apparatus of claim 10, wherein the stability magnet comprises a magnet having an opening.

11. The apparatus of claim 10, wherein the stability magnet creates a symmetrical magnetic field.

12. The apparatus of claim 10, wherein the stability magnet is positioned external to the vessel.

13. The apparatus of claim 12, wherein the stability magnet includes an opening for receiving a portion of the vessel.

14. The apparatus of claim 10, wherein the stability magnet is positioned in an interior compartment of the vessel.

15. The apparatus of claim 14, wherein the stability magnet is affixed to the vessel.

16. An apparatus for intended use in transferring a fluid under cryogenic conditions, comprising: a vessel including an inlet for receiving the fluid and an outlet for discharging the fluid; a fluid-agitating element for placement in the vessel in contact with the fluid, said fluid-agitating element comprising a superconductor maintained at or below a transition temperature by the fluid; and a motive device for placement external to the vessel, said motive device including a magnetic field for forming a first magnetic coupling with the superconductor and causing the fluid-agitating element to agitate the fluid.

17. The apparatus of claim 16, further including a stability magnet for forming a second magnetic coupling with the superconductor of the fluid-agitating element.

18. An apparatus for agitating fluids under cryogenic conditions, comprising an impeller including a superconductor.

19. A method of transferring a fluid under cryogenic conditions, comprising: introducing the fluid into a vessel; agitating the fluid using a fluid-agitating element comprising a superconductor so that the fluid is transferred out of the vessel.

20. The method of claim 19, further including the step of field cooling the superconductor using the fluid before the agitating step.

21. The method of claim 19, wherein the agitating step comprises rotating the fluid-agitating element via a magnetic coupling with motive device external to the vessel.

22. The method of claim 19, further including the step of positioning a stabilizing magnet so as to form a magnetic coupling with the superconductor.