Patent Publication Number: US-2016230932-A1

Title: Low heat loss cryogenic fluid storage equipment using multilayered cylindrical support

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0016991, filed on Feb. 5, 2015, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     The present invention relates to cryogenic fluid storage equipment, and more particularly, to low heat loss cryogenic fluid storage equipment using a multilayered cylindrical support, which minimizes a heat inflow from the outside and can store a cryogenic liquid such as liquefied natural gas (LNG), liquefied propane gas (LPG), liquid oxygen, liquid nitrogen, liquid hydrogen, liquid helium, and the like. 
     As the measure for solving problems of air pollution and global warming caused by excessive use of fossil fuel, research has focused on a system utilizing fuel sources other than hydrocarbon fuel. Hydrogen energy is one such fuel source. 
     In order to efficiently utilize hydrogen energy, a volume of the hydrogen may be reduced to make high density hydrogen. Using high density hydrogen results in superior storage, transport, and ease of use compared to lower density hydrogen. Of the various ways of storing hydrogen, liquefying and storing hydrogen in a liquid phase maintains the largest energy storage. Thus, to extend the utilization of hydrogen energy, cryogenic equipment is needed with the capability of effectively storing hydrogen in a liquid phase in a quick, safe, and effective manner. 
     An important aspect of storing a cryogenic liquid is providing a heat-insulation technique—in particular, a storage container—that can minimize evaporation caused by a heat inflow from external sources. Various methods of insulation have been utilized in the art. For example, vacuum insulation, multilayer insulation (MLI), and the like have been utilized. These methods of insulation can reduce conductive heat transfer, convective heat transfer, and radiant heat transfer caused by air. 
     However, improvements in storage containers for cryogenic liquids is still needed. For example, present containers still allow an undesired amount of heat transfer from the outside environment to the cryogenic liquid, which in the case of hydrogen, is typically stored at about −250° C. or below. 
     One drawback of typical cryogenic storage devices is that, for those containers utilizing an internal container within an external container, the internal container is fixed to a support structure that allows undesirable levels of heat transfer to the internal container. Thus, the support becomes a conductive heat transfer path from the outside to the cryogenic liquid. This, in turn, causes rapid evaporation of the stored cryogenic liquid. 
     SUMMARY 
     The present disclosure is intended to solve the problems laid out above. For example, an object of the present disclosure is to provide a fluid storage device having low heat-loss characteristics. The storage device may include an internal container for storing a cryogenic liquid and an external container at least partially surrounding the internal container. The storage device may include a cover enclosing an upper end of the external container and configured to maintain a vacuum around the inner container, as well as a transferring tube connected to the internal container to supply and/or extract the cryogenic liquid to/from the internal container. The storage device can also include a support structure coupled to both the cover and the internal container such that the internal container is suspended within the external container via the support structure. The support structure itself may include an inner cylindrical body coupled to the internal container and surrounding at least a portion of the internal container, an adjacent cylindrical body coupled to the inner cylindrical body, and an outer cylindrical body coupled to the adjacent cylindrical body. A plurality of coupling members may be disposed between the inner and adjacent cylindrical bodies and the adjacent and outer cylindrical bodies, respectively. 
     Another object of the disclosure is to provide a thermal insulating structure. The thermal insulating structure can include an inner cylindrical body having a heat insulating material attached to a surface of the inner cylindrical body, an adjacent cylindrical body having a heat insulating material attached to a surface of the adjacent cylindrical body, the adjacent cylindrical body being spaced apart from and surrounding the inner cylindrical body, and an outer cylindrical body having a heat insulating material attached to a surface of the outer cylindrical body, the outer cylindrical body being spaced apart from and surrounding the adjacent cylindrical body. Additionally, the thermal insulating structure may include a first set of coupling members disposed between the inner and adjacent cylindrical bodies and coupling said cylindrical bodies to one another and a second set of coupling members disposed between the adjacent and outer cylindrical bodies and coupling said cylindrical bodies to one another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features, and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the accompanying drawings, in which: 
         FIG. 1  is a sectional perspective view of an example cryogenic fluid storage equipment. 
         FIG. 2  is a partial sectional perspective view of an example cryogenic fluid storage equipment. 
         FIG. 3  is a partial sectional perspective view of an example cryogenic fluid storage equipment. 
         FIG. 4  is a partial sectional view of an example multilayered cylindrical support of a cryogenic fluid storage equipment. 
         FIG. 5A  is an exploded view showing a part of an example support in a cryogenic fluid storage device. 
         FIG. 5B  is an exploded view showing a part of an example support in a cryogenic fluid storage device. 
     
    
    
     DETAILED DESCRIPTION 
     Various cryogenic fluid storage devices are described in detail below with reference to the accompanying drawings. While the present disclosure is shown and described in connection with example embodiments thereof, it will be apparent to those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention. 
       FIG. 1  shows an example cryogenic fluid storage device. The cryogenic fluid storage device of  FIG. 1  includes an external container  10 , an internal container  20  for storing a cryogenic fluid, and a transferring tube  30  for transferring cryogenic fluid into and/or out of the internal container  20 .  FIG. 1  also illustrates an example multilayered cylindrical support  100 , and an example multilayered blocking plate  200 . 
     The external container  10  may extend upward as shown in  FIG. 1  and have an open upper end so that other elements such as the internal container  20  can be installed in the external container  10 . An upper cover  15  is coupled with the open upper end. A through hole is formed on the upper cover  15 , and the upper cover  15  includes a sealing plate  16  covering the through hole. In alternative embodiments, upper cover  15  and sealing plate  16  may be replaced by a single cover that seals the external container  10 . 
     In the example embodiment of  FIG. 1 , the internal container  20  serves as a space in which a cryogenic fluid is actually stored, and the internal container  20  is installed in the external container  10  and spaced apart from an inner circumference surface of the external container  10 . A vacuum may be formed in a space between the internal container  20  and the external container  10 , and a vacuum heat insulating layer is may be included around the internal container  20  to increase the insulation of the cryogenic fluid. The vacuum between an inner circumference surface of the external container  10  and an outer circumference surface of the internal container  20  minimizes convective heat transfer and heat conduction caused by air. 
     Various heat insulating structures including a multilayered heat insulating material (not shown) surrounding the internal container  20  may be provided in the space between the external container  10  and the internal container  20 . For example, the space between containers may be filled with an insulating material that is also in a vacuum. 
     The internal container  20  may include a neck portion (shown in  FIG. 2  as  22 ) which extends from a cryogenic liquid filling space formed at a lower portion to an upper portion. Various elements may extend through the neck portion and into the internal container  20 , such as the transferring tube  30  for transferring a cryogenic liquid and a level-measuring tube for measuring an amount of stored cryogenic liquid. A multilayered blocking plate  200  may also be installed within the neck portion of the internal container  20 . The multilayered blocking plate  200  can be used to interrupt an upward movement of boiled-off gas toward an upper end of the internal container  20 , thereby preventing unwanted heat transfer. 
       FIG. 1  shows the internal container  20  suspended from multilayered support  100 , which is in turn suspended from upper cover  15 . In other embodiments, multilayered support  100  may suspend internal container  20  by attaching to the external container  10  rather than upper cover  15 . 
     The transferring tube  30  is connected to the internal container  20  to fill and extract a cryogenic liquid. A filling tube and a discharging tube may be separately formed. In the embodiment of  FIG. 1 , the transferring tube  30  includes an inner tube  32  through which a cryogenic liquid is moved and an outer tube  34  surrounding at least a portion of the inner tube  32 . A vacuum may be formed between the inner tube  32  and the outer tube  34  to block convective heat transfer and heat conduction otherwise caused by air. 
     The transferring tube  30  may penetrate either, or both, the sealing plate  16  and the upper cover  15 . It can also penetrate the various levels of multilayered blocking plate  200 . The outer tube  34  is extended to a location adjacent to a lower end of the neck portion  22 , and the inner tube  32  is extended to a lower end of a main body of the internal container  20 . The outer tube  34  may be extended a shorter or longer distance along inner tube  32 , based on the necessity for insulation along inner tube  32 . 
     As shown in  FIG. 2 , the multilayered cylindrical support  100  includes at least one cylindrical support body surrounding at least a portion of neck portion  22  of internal container  20 . In some embodiments, multilayered cylindrical support  100  includes a multilayered structure in which an inner cylindrical body is spaced apart from another adjacent outer cylindrical body and the outer cylindrical body surrounds the adjacent inner cylindrical body. 
     Among the cylindrical bodies constituting the multilayered cylindrical support  100 , an outermost cylindrical body  102  is attached to a periphery of the through hole  12  under the upper end cover  15  through an upper end thereof and is extended downward to surround the neck portion  22 . The outermost cylindrical body  102  may be formed integrally with the upper end cover  15  at the time of manufacturing the same. 
     Among the cylindrical bodies constituting the multilayered cylindrical support  100 , an innermost cylindrical body  104  is attached to an upper end of the internal container  20 , that is, to an outer circumference surface of an upper end of the neck portion  22  through an upper end thereof, and the innermost cylindrical body is spaced apart from the neck portion  22  and is extended downward to surround the neck portion  22 . 
     A plurality of intermediate cylindrical bodies  106  are further provided between the outermost cylindrical body  102  and the innermost cylindrical body  104 , and the cylindrical bodies  102 ,  104 ,  106  are spaced apart from each other with a certain space. Although the accompanying drawing shows that the multilayered cylindrical support  100  according to the embodiment of the present invention has a multilayered structure in which a space is formed between two adjacent bodies of four (4) cylindrical bodies  102 ,  104 , and  106 , the present disclosure is not limited to the number of the cylindrical bodies. For example, the multilayered cylindrical support  100  may include only one cylindrical body, or may include 6, 8, 10, or more cylindrical bodies. 
     In an example embodiment, a heat insulating material, preferably, a multilayered heat insulating material  115  may be attached to both surfaces of each of the cylindrical bodies  102 ,  104 , and  106  constituting the multilayered cylindrical support (see  FIG. 4 ). Here, the multilayered heat insulating material  115  may be attached by means of an extremely low temperature adhesive. The multilayered heat insulating material  115  attached to one cylindrical body is spaced apart from the multilayered heat insulating material  115  attached to another adjacent cylindrical body. 
     In the example embodiment of  FIG. 2 , the multilayered cylindrical support  100  includes a coupling member  110  for coupling the cylindrical bodies  102 ,  104 , and  106 , which are adjacent to each other and constitute the multilayered cylindrical support  100 , in a state where the cylindrical bodies are spaced apart from each other. Due to the above structure, the multilayered cylindrical support  100  supports the internal container  20  with respect to the upper end cover  15  of the external container  10 . 
       FIGS. 5A and 5B  show an example embodiment of a coupling member  110  coupling two adjacent intermediate cylindrical bodies  106  to one another. A similar type of coupling may be used between the adjacent cylindrical bodies  102 ,  104 , and  106  of, for example,  FIG. 2 . Referring to  FIG. 5 , through holes are formed on main surfaces of the cylindrical bodies  106 , which are faced to each other, and both end portions of the coupling member  110  are inserted in the through holes. 
     In the embodiment of  FIG. 5 , the coupling member  110  has a thickness greater than the sum of thicknesses of both cylindrical bodies. In this embodiment, the length of the coupling member  110  retains a space between adjacent cylindrical bodies  106 . For example, the coupling member may have a cylindrical block shape having a thickness of several millimeters. The coupling member  110  couples the adjacent cylindrical bodies  102 ,  104 , and  106  in a state where the cylindrical bodies are spaced apart from each other, to allow the cylindrical bodies to be supported with respect to each other. 
     Coupling members  110  may be sized such that the friction generated between the coupling member  110  and the hole cause the coupling member  110  to remain in the hole and couple the adjacent cylindrical bodies to one another. In that embodiment, coupling members  110  may be installed via press fitting. In other embodiments, coupling members  110  may have keyholes or other suitable mechanisms for locking into place. 
     According to one embodiment, the cylindrical bodies which are adjacent to each other include at least three coupling members  110  arranged in regular intervals. However, the present invention is not limited by the size and number of the coupling members. For example, if the cryogenic fluid storage equipment has a large capacity, that is, if the block type coupling member is not sufficient to support a weight of the internal container, partial ring-shaped block type coupling members disposed between the adjacent cylindrical bodies  102 ,  104 , and  106  may be employed as the coupling member to support the adjacent cylindrical bodies  102 ,  104 , and  106 . The coupling member  110  is designed such that the coupling member supports a weight exerted between the adjacent cylindrical bodies  102 ,  104 , and  106  and minimizes a heat-conduction area. 
     As shown in  FIG. 2 , in the coupling members  110  of the multilayered cylindrical support  100 , the cylindrical bodies are placed in the spaces adjacent to each other in a radial direction and are alternately arranged at an upper portion and a lower portion to couple the adjacent cylindrical bodies. For example, the outermost cylindrical body  102  and the adjacent intermediate cylindrical body  106  are coupled at a lower portion by the coupling member  110 , the intermediate cylindrical body  106  and another adjacent inside intermediate cylindrical body  106  are coupled at an upper portion by the coupling member  110 , and the inside intermediate cylindrical body  106  and the adjacent innermost cylindrical body  104  are coupled at a lower portion by the coupling member  110 . The arrangement in which the coupling members  110  are placed in the spaces which are adjacent to each other in the radial direction increases a heat conduction length—that is, the length of material through which heat conduction must travel. 
     In addition, the coupling members  110  of the multilayered cylindrical support  100  according to the present invention are arranged such that the coupling members placed in the spaces which are adjacent to each other in the radial direction are disposed in a circumferential direction in a zigzag shape. In other words, if the coupling members  110  are arranged at angular locations of 0°, 120°, and 240° between the outermost cylindrical body  102  and the adjacent intermediate cylindrical body  106 , the coupling members  110  placed in the spaces (which are adjacent to each other in the radial direction) between the other intermediate cylindrical body  106  and the innermost cylindrical body  104  are arranged at angular locations of 60°, 180°, and 300°. Due to the arrangement of the above coupling members  110 , it is possible to further extend the heat conduction length. Other angular locations are also contemplated, especially in situations where additional coupling members  110  are utilized. 
     According to an example embodiment, the coupling member  110  is formed of a low heat-conductive material. For example, coupling member  110  may be formed of GREL (glass reinforced epoxy laminate). GREL includes, for example, G-10, G-11, and G-10 CR. More preferably, G-10 CR (fiberglass epoxy for cryogenic use) may be employed as a material used for forming the coupling member. G-10 CR is advantageous in that the heat-conductivity of G-10 CR at an extremely low temperature is very low, a displacement of heat contraction and heat expansion of G-10 CR is small, and G-10 CR can effectively reduce heat conduction between a low temperature of the internal container and room temperature of the outside. The coupling member  110  formed of GREL satisfies a mechanical strength so as to couple and support the cylindrical bodies and minimizes the heat conduction through a low heat conduction property. 
     Due to the above structure, the multilayered cylindrical support  100  of the present invention can simultaneously perform the functions of supporting the internal container  20  with respect to the external container  10 , reducing a radiant heat transfer, and minimizing heat conduction. Because heat conduction indicates that heat is transferred along/through an object, the rate of heat conduction can be controlled by adjusting the length of a heat transferring path and an area of the heat transferring path. 
     Since the cylindrical body  102 ,  104 , or  106  and the adjacent cylindrical body  102 ,  104 , or  106  are coupled with each other through the coupling member  110 , the heat conduction between the cylindrical body  102 ,  104 , or  106  and the adjacent cylindrical body  102 ,  104 , or  106  necessarily passes through the coupling member  110 . As compared with the cylindrical bodies  102 ,  104 , and  106 , however, the coupling member  110  has a very small heat conduction area, and thus a so-called “thermal bottleneck” phenomenon is generated and heat conducted through the coupling member  110  is minimized. In addition, since the multilayered cylindrical support  100  has the multilayered structure of the cylindrical bodies spaced from each other, conducted heat is reduced whenever the heat passes through the coupling members  110 . Thus, when seen from the innermost cylindrical body  104 , it is possible to minimize inflow heat conducted from outside room temperature. 
     In some embodiments, the coupling members  110  alternately couple the adjacent cylindrical bodies at an upper portion and a lower portion and are disposed in the circumferential direction in the zigzag shape. Heat conducted from the upper cover  15  exposed to an external room temperature to the outermost cylindrical body  102  is transferred to a lower portion along the longest path of the cylindrical body  102 , and is then conducted to the adjacent intermediate cylindrical body  106  through the coupling member  110  placed at the lower portion. The heat conducted to the intermediate cylindrical body  106  is transferred to the upper portion along a path which is the same as the above path, and is conducted to the other inside intermediate cylindrical body  106  through the coupling member  110  connecting the other inside intermediate cylindrical body  106  to this intermediate cylindrical body. In other words, a heat conduction path which is longer than the sum of lengths of the cylindrical bodies is formed. Thus, according to the present invention, it is possible to minimize the heat conduction due to a kind of the thermal bottleneck phenomenon and an extension of the heat conduction caused by the coupling member  110 . In addition, if the coupling member  110  is formed of a GREL material, the heat conduction is further minimized. Simultaneously, since the multilayered heat insulating material  115  is disposed between the cylindrical bodies  102 ,  104 , and  106 , it is possible to minimize the radiant heat transfer. 
     In some embodiments, blocking plates  200  are provided in multiple layers in the neck portion  22  of the internal container  20 . The blocking plates  200  block the neck portion  22  in a transverse direction which is perpendicular to the extension direction of the neck portion  22 , and the blocking plates are formed in a multilayered structure in which the blocking plates are spaced apart from each other to form a space  202  therebetween. Blocking plates  200  may be formed of a GREL material which is a kind of a low heat-conductive material, and preferably, G-10 CR may be utilized as the material for the blocking plate. 
     The multilayered blocking plates  200  prevent, among other things, convective heat transfer in which a gas produced by evaporating a cryogenic fluid in the internal container  20  is moved to an upper portion of the internal container  20 . Since the transferring tube  30  penetrates the multilayered blocking plates  200 , some of evaporated gas is moved upward along a space between an outer circumferential surface of the transferring tube  30  and an inner circumferential surface of the hole of each blocking plate  200  through which the transferring tube  300  passes, that is, along a portion through which the transferring tube  300  passes, and can be then moved to the space  202  between the blocking plates  200 . However, since the blocking plates are provided in a multilayered structure, the spaces  202  formed between the blocking plates  200  are also disposed in a multilayered structure. 
     In other words, since a flow of gas in the space  202  placed on and under the blocking plate  202  is maximally suppressed, and the spaces  202  are disposed in the multilayered structure to maximally suppress the flow of gas, the convective heat transfer caused by the flow of gas can be minimized. 
     In addition, since the blocking plate  200  is formed of a low heat-conductive material, for example, a GREL material, the heat conduction between the upper and lower spaces  202  is suppressed so that the multilayered blocking plates  200  can effectively prevent heat invasion from the outside into the internal container  20 . 
     Various modifications can be made to the above-described example embodiments without departing from the spirit or scope of the invention. Thus, it is intended that the present invention covers all such modifications.