阅读说明：本技术 极低温液化气体运输船的货舱及液化气体燃料容器的膜状物型隔热系统 (Cargo tank for cryogenic liquefied gas carrier and film-shaped heat insulation system for liquefied gas fuel container ) 是由 朴成祐 权升慜 金玹承 姜重圭 于 2018-12-27 设计创作，主要内容包括：本发明涉及极低温液化气体运输船的货舱及液化气体燃料容器的膜状物型隔热系统,设置有多阶段地层叠有二次隔热层的多个板,其中,通过使上板和下板交替地布置,从而最大限度地减少板之间的间隔中可能产生的热损失并且最大限度地减少因温度差而导致的变形。(The present invention relates to a membrane-type thermal insulation system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier, which is provided with a plurality of plates in which secondary thermal insulation layers are laminated in multiple stages, wherein an upper plate and a lower plate are alternately arranged, thereby minimizing heat loss that may occur in the space between the plates and minimizing deformation due to a temperature difference.)

1. A film type heat insulation system of a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier relates to a heat insulation system having a secondary heat insulation layer provided at an inner wall of a hull and a primary heat insulation layer provided at a liquefied gas, wherein a plurality of plates are divided and laminated in multiple stages in a thickness direction of the heat insulation layer, and the divided and laminated upper and lower plates are alternately arranged with each other.

2. The membrane-type heat insulating system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to claim 1, further comprising:

a plate fixing unit fixing the plurality of plates,

wherein the board fixing unit includes a lower board fixing part and an upper board fixing part.

3. The membrane-type heat insulating system for a cargo tank and a liquefied gas fuel container of a very low temperature liquefied gas carrier according to claim 2, wherein the lower plate fixing portion comprises:

a center fixing lower plate fixing part provided at a center of the lower plate; and

corner fixing lower plate fixing parts provided near four corners of the lower plate.

4. The membrane-type heat insulating system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to claim 3, wherein the center fixing lower plate fixing portion comprises:

a fixing rod welded to the hull inner wall and penetrating and disposed in a fixing hole (through portion) formed at the center of the lower plate; and

and a fixing base having a screw thread portion formed at a lower portion to be coupled with an upper end of the fixing rod, and an upper plate fixing stud bolt formed at an upper portion to be coupled with four corner portions of the upper plate.

5. The membrane-type heat insulating system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to claim 3, wherein the corner fixing lower plate fixing portion comprises:

a lower plate fixing stud bolt fixed to the inner wall of the hull on which the lower plate is provided;

a nut fastened to the lower plate with a stud bolt to fix the lower plate;

an elastic body clamped at the lower plate fixing stud bolt and adjusting the degree of elasticity according to the deformation degree of the inner wall of the ship body;

a compression fixing mold clamped at the stud bolts to be laminated under the elastic body to prevent a local damage of the lower plate; and

and the height of the reference plate is adjusted according to the deformation degree of the inner wall of the ship body.

6. The membrane-type heat insulating system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to claim 4, wherein the upper plate fixing portion comprises:

the nut is fixed with the upper plate and is fastened by a stud bolt so as to fix the upper plate;

an elastic body clamped at the upper plate fixing stud and adjusting elasticity; and

a compression fixing die that is sandwiched at the upper plate fixing stud and stacked under the elastic body to prevent a local damage of the upper plate.

7. The membrane-type thermal insulation system for cargo tanks and liquefied gas fuel containers of very low temperature liquefied gas carrier vessels according to claim 1, wherein the primary thermal insulation layer is composed of a composite body of a combination of plywood, a thermal insulation material, and a composite material and has a thickness within 20 to 30% of the thickness of the secondary thermal insulation layer, and

the secondary heat insulation layer is formed by a sandwich form of glass fiber reinforced polyurethane foam and plywood.

8. The membrane type heat insulating system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to claim 1, wherein a plurality of plates in the secondary heat insulating layer are divided and laminated in multiple stages along a thickness direction of the heat insulating layer, and the divided and laminated upper and lower plates are alternately arranged with each other, thereby having a structure that minimizes heat loss that may occur in an interval between the plates and reduces deformation due to a temperature difference.

Technical Field

The present invention relates to a membrane type thermal insulation system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier, and more particularly, to a membrane type thermal insulation system for a liquefied gas fuel container and a cargo tank of a cryogenic liquefied gas carrier, which is provided with a plurality of plates (panels) in which secondary thermal insulation layers are laminated in multiple stages to improve thermal insulation performance, and is capable of minimizing heat loss that may occur in an interval between the plates and minimizing deformation due to a temperature difference by arranging upper and lower plates alternately with each other.

Background

In general, Natural Gas is transported in a gaseous state through a Gas pipeline on land or at sea, or transported to a remote consumption site in the case of being stored in an LNG carrier in a Liquefied Natural Gas (hereinafter, abbreviated as LNG) state.

LNG is obtained by cooling natural gas to very low temperatures (approximately around-163 ℃), and is very suitable for transport over long distances by sea, with a volume reduced to about 1/600 compared to when natural gas is in a gaseous state.

An LNG carrier for loading LNG and operating on the sea and unloading the LNG at a desired location on land, or a regasification vessel (LNG RV) for regasifying and unloading the stored LNG in a natural gas state after loading LNG and operating on the sea and arriving at the desired location on land is provided with a storage tank, i.e., a cargo tank, that can withstand the very low temperature of liquefied natural gas.

Recently, there is an increasing demand for floating offshore structures such as LNG FPSO (floating, production, storage and offloading) or LNG FSRU (floating storage and offloading unit), and such floating offshore structures have a cargo hold provided on an LNG carrier or an LNG RV therein.

The LNG FPSO is a floating offshore structure that is stored in a cargo tank for directly liquefying produced natural gas at sea and is used to transfer LNG stored in the cargo tank to an LNG carrier when necessary.

The LNG FSRU is a floating offshore structure that, after LNG unloaded from an LNG carrier is stored in a cargo tank at an offshore site remote from land, vaporizes the LNG as needed and supplies the LNG to a desired site on the land.

As described above, the cargo tank for storing LNG in a cryogenic state is provided in the offshore structure such as the LNG carrier, the LNGRV, the LNG FPSO, and the LNG FSRU, which transport or store liquid cargo such as LNG on the sea.

The cargo hold may be classified into an independent tank type (independent tank) and a membrane type (membrane type) according to whether a load by the liquid cargo is directly applied to the heat insulating material.

Generally, membrane type cargo holds are classified into GTT NO96 type, TGZ Mark iii type, and the like, and independent tank type cargo holds are classified into MOSS type, IHI-SPB type, and the like.

The thermal insulation material and structure of the membrane type cargo tank are different depending on the type of metal plate, while the GTTNO96 type uses a thin plate of Invar (an alloy having Invar-iron and nickel as main components and having a very low thermal expansion coefficient), and the MARK iii type uses a thin plate of stainless steel.

The GTT NO96 type cargo tank is provided by alternately stacking a primary membrane material and a secondary membrane material made of invar steel having a thickness of 0.5 to 1.5mm and a primary thermal barrier wall and a secondary thermal barrier wall made of plywood box (plywood box), perlite (perlite), and the like inside a ship body.

The insulation system of the GTT NO96 type cargo hold is constructed by laminating invar steel (36% nickel steel) and perlite and an insulation box made of plywood as two layers, and plywood is used as a material for the insulation box.

In the conventional insulation system for the liquefied gas cargo tank, there is a technical limitation in reducing the thickness of the primary insulation layer in order to maintain the insulation performance of the primary insulation layer. That is, when the thickness of the primary heat insulating layer is too thin, a problem in heat insulating performance occurs, and a technical problem occurs in fixing the primary heat insulating layer.

Disclosure of Invention

Technical problem

A liquefied gas cargo tank includes a plurality of heat insulating panels made of polyurethane foam (PUF), and an insulation structure made of polyurethane foam may not be sufficient to effectively insulate extremely low-temperature liquefied natural gas or the like, and for this reason, in order to improve insulation performance, the thickness of the heat insulating panel is conventionally set to be excessively thick, which leads to a problem that the loading volume of the cargo tank is reduced, and as the thickness of the heat insulating panel becomes thicker, not only does the manufacturing cost increase, but also the transportation cost increases due to the weight of the thickened heat insulating panel.

Further, in the case of using other heat insulating panels instead of the conventional heat insulating panels such as polyurethane foam or foam currently used, there may be caused a decrease in heat insulating performance, or a problem of weakness to self-strength or external impact may occur even if the heat insulating performance is excellent.

Fig. 1 is a sectional view showing a general secondary heat insulating layer and a secondary heat insulating layer of a single structure having an enlarged thickness. Further, fig. 2 is a sectional view illustrating heat loss generated in the gap between the secondary heat insulating layers of the single structure having an enlarged thickness, and fig. 3 is a sectional view illustrating heat shrinkage of the secondary heat insulating layers of the single structure having an enlarged thickness.

First, as shown in fig. 1, conventionally, in order to improve the heat insulating performance of the secondary heat insulating layer (10), a method of using a secondary heat insulating layer (20) of a single structure manufactured by simply increasing the thickness of the secondary heat insulating layer (10) is used.

In a heat insulation system composed of a polyurethane foam and plywood, which are materials constituting the secondary heat insulation layer, in order to improve the heat insulation performance, it is necessary to increase the thickness of the polyurethane foam, and there is a limitation in increasing the polyurethane foam at an appropriate thickness.

As shown in fig. 2, the plate having an increased thickness has a shortened thermal path (thermal path) under actual temperature conditions, and thus has a problem in that heat loss such as convection occurs. Further, as shown in fig. 3, there is a problem that a serious deformation of the secondary heat insulating layer (20) of a single structure occurs at the time of heat shrinkage.

In order to solve such problems, the present invention provides a technique in which a film of a metal material usable at an extremely low temperature is used as a primary film and a secondary film, and a primary insulation layer is composed of a composite of a combination of plywood (plywood), a heat insulating material, a composite material, and the like, thus having a thickness within 20 to 30% of that of a secondary insulation layer, and the secondary insulation layer includes a sandwich-type arrangement of glass fiber-reinforced polyurethane foam and plywood, whereas in a manner and structure in which the thickness of the secondary insulation layer is increased (expanded) in order to improve the insulation performance of an insulation system, a conventional manner of simply increasing the thickness of polyurethane foam constituting the secondary insulation layer is avoided, so that the secondary insulation layer is laminated by a plurality of panels in the thickness direction, and upper and lower panels are alternately arranged with each other, therefore, heat loss that may occur in the space between the plates can be minimized, and deformation due to a temperature difference can be minimized as compared to a single plate.

Means for solving the problems

In order to achieve the above object, the present invention relates to an insulation system having a secondary insulation layer provided at an inner wall of a hull and a primary insulation layer provided at liquefied gas, characterized in that the secondary insulation layer in which a plurality of panels are divided and laminated in multiple stages in a thickness direction of the insulation layer, and the divided and laminated upper and lower panels are alternately arranged with each other.

The present invention may further include a board fixing unit fixing the plurality of boards, and the board fixing unit may include a lower board fixing part and an upper board fixing part.

The lower plate fixing parts may include center fixing lower plate fixing parts provided at the center of the lower plate and corner fixing lower plate fixing parts provided near four corners of the lower plate.

The center fixing lower plate fixing part may include a fixing rod welded to the inner wall of the hull and penetrating and disposed in a fixing hole (penetrating part) formed at the center of the lower plate, and a fixing base formed at a lower portion with a screw part to be coupled with an upper end of the fixing rod and at an upper portion with an upper plate fixing stud bolt to be coupled with four corner portions of the upper plate.

The lower plate fixing part for corner fixing may include a lower plate fixing stud bolt fixed on the inner wall of the hull provided with the lower plate, a nut fastened with the lower plate fixing stud bolt to fix the lower plate, an elastic body clamped at the lower plate fixing stud bolt and adjusting elasticity according to a deformation degree of the inner wall of the hull, a compression fixing die clamped at the stud bolt to be laminated under the elastic body to prevent local damage of the lower plate, and a reference plate adjusting height according to the deformation degree of the inner wall of the hull.

The upper plate fixing portion may include a nut fastened with the upper plate fixing stud bolt to fix the upper plate, an elastic body clamped at the upper plate fixing stud bolt and adjusting a degree of elasticity, and a compression fixing die clamped at the upper plate fixing stud bolt and stacked under the elastic body to prevent a local damage of the upper plate.

The primary thermal insulation layer may be formed of a composite of a combination of plywood (plywood), a thermal insulation material, and a composite material, and may have a thickness within 20 to 30% compared to a thickness of the secondary thermal insulation layer.

The secondary thermal insulation layer may be formed in a sandwich form of glass fiber reinforced polyurethane foam and plywood.

Effects of the invention

As described above, although a method of simply increasing the thickness of a single panel in order to improve thermal insulation has been conventionally used, there is a limit in the thickness in this case. That is, there is a limitation in increasing the panel thickness because there is a limitation in the foaming height of the polyurethane foam, whereas in the present invention, there is no limitation in increasing the insulation thickness of the panel by laminating a plurality of panels in multiple stages.

In general, when the thickness of a single plate is increased in order to improve the heat insulation property, thermal shrinkage occurs due to a temperature difference between liquefied gas in the upper and lower portions of the secondary heat insulation layer. At this time, the upper plate positioned closer to the liquefied gas undergoes greater thermal contraction than the lower plate, and when the insulation thickness is increased, the amount of contraction is further increased to create a space between the plates, thereby causing a problem of a decrease in insulation properties.

In order to solve such problems, in the present invention, as a plurality of alternately arranged panels are constructed in a sandwich form, plywood or composite material of the panel surface is less heat-shrunk than polyurethane foam, and thus the amount of shrinkage is reduced as compared with a single panel, and further, due to the alternate arrangement between the upper and lower panels, not only is the interval that may occur between the panels small, but also heat loss that may occur in the interval is not connected to the interval between the lower panels of the secondary insulation layer, and thus heat loss can be greatly reduced.

Further, the upper plate provided on the lower plate presses the lower plate downward, and thus has a function of restricting deformation of the lower plate, so that deformation occurring in the plate can be minimized, and the strength load of the secondary membrane due to deformation of the secondary heat insulating layer can be greatly reduced.

Drawings

Fig. 1 is a sectional view showing a conventional secondary heat insulating layer and a secondary heat insulating layer of a single structure having an enlarged thickness.

Fig. 2 is a sectional view illustrating heat loss generated in the space between the secondary insulation layers of a single structure having an enlarged thickness.

Fig. 3 is a sectional view illustrating thermal contraction of a secondary heat insulating layer of a single structure having an enlarged thickness.

Fig. 4 is a perspective view showing a lower plate of a secondary thermal insulation layer in the cargo tank of the cryogenic liquefied gas carrier and the membrane type thermal insulation system of the liquefied gas fuel container according to the present invention.

Fig. 5 is a perspective view showing the lower plate and the upper plate of the secondary thermal insulation layer in the cargo tank of the cryogenic liquefied gas carrier and the membrane type thermal insulation system for the liquefied gas fuel container according to the present invention.

Fig. 6 is a perspective view showing the lower plate and the upper plate of the secondary thermal insulation layer and the secondary membrane in the membrane type thermal insulation system for the cargo tank and the liquefied gas fuel container of the cryogenic liquefied gas carrier according to the present invention.

Fig. 7 is a sectional view showing a center fixing lower plate fixing portion in the cargo tank of the cryogenic liquefied gas carrier and the membrane-type heat insulating system for the liquefied gas fuel container according to the present invention.

Fig. 8 is a sectional view showing a lower plate fixing part for corner fixing of the present invention with respect to the part a of fig. 6.

Fig. 9 is a sectional view showing an upper plate fixing part of the present invention with respect to a part B of fig. 6.

Fig. 10 is a sectional view illustrating heat loss prevention in the space between the plates of the present invention.

Fig. 11 is a sectional view showing heat shrinkage in the plate of the present invention.

Fig. 12 is a perspective view showing a primary insulation layer made of plywood according to the present invention.

Fig. 13 is a perspective view showing a primary insulation layer composed of a composite material of the present invention.

Detailed Description

Hereinafter, a membrane type thermal insulation system for a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to the present invention will be described with reference to the accompanying drawings.

Fig. 4 is a perspective view showing a lower plate of a secondary thermal insulation layer in the cargo tank of the cryogenic liquefied gas carrier and the membrane type thermal insulation system of the liquefied gas fuel container according to the present invention.

Fig. 5 is a perspective view showing the lower plate and the upper plate of the secondary thermal insulation layer in the cargo tank of the cryogenic liquefied gas carrier and the membrane type thermal insulation system for the liquefied gas fuel container according to the present invention.

Fig. 6 is a perspective view showing the lower plate and the upper plate of the secondary thermal insulation layer and the secondary membrane in the membrane type thermal insulation system for the cargo tank and the liquefied gas fuel container of the cryogenic liquefied gas carrier according to the present invention.

Meanwhile, fig. 7 is a sectional view showing a lower plate fixing part for center fixing in a membrane type heat insulation system of a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier according to the present invention, fig. 8 is a sectional view showing a lower plate fixing part for corner fixing according to the present invention with respect to a portion a of fig. 6, and fig. 9 is a sectional view showing an upper plate fixing part according to the present invention with respect to a portion B of fig. 6.

Referring to the above drawings, the membrane type thermal insulation system of a cargo tank and a liquefied gas fuel container of a cryogenic liquefied gas carrier of the present invention has a secondary thermal insulation layer (200) provided at an inner wall (1) of a hull and a primary thermal insulation layer (100) provided at a liquefied gas, the secondary thermal insulation layer (200) may have a plurality of plates laminated in multiple stages in a thickness direction, and upper and lower plates may be alternately arranged with each other.

That is, the present invention has a configuration in which the secondary insulation layer (200) divides and laminates a plurality of plates (210, 220) in multiple stages in the thickness direction, and the upper and lower plates (210, 220) laminated in multiple stages are alternately arranged with each other, so that heat loss that may occur in the space between the plates (210, 220) can be minimized and deformation due to a temperature difference can be reduced.

For convenience of description, the present embodiment will be described with an example in which the secondary heat insulating layer (200) is formed of a two-stage structure, i.e., a lower plate (210) and an upper plate (220).

In the present embodiment, the plates (120, 220) constituting the secondary thermal insulation layer (200) may be formed in a sandwich form of a glass fiber-reinforced polyurethane foam (R-PUF) and plywood.

The present embodiment may further include a plate fixing unit fixing the lower plate (210) and the upper plate (220).

The plate fixing unit includes a lower plate fixing part fixing the lower plate (210) to the inner wall (1) of the hull and an upper plate fixing part (400) fixing the upper plate (220).

Next, the lower plate fixing portions include center fixing lower plate fixing portions (310) provided at the center of the lower plate (210) and corner fixing lower plate fixing portions (320) provided near four corners of the lower plate (210).

First, as shown in fig. 7, the center fixing lower plate fixing part (310) includes a fixing rod (311) and a fixing base (312), wherein the fixing rod (311) is welded to the hull inner wall (1) and penetrates and is disposed in a fixing hole (through part) (H2) formed at the center of the lower plate (210), and the fixing base (312) is formed at a lower part with a threaded part (312a) to be coupled with an upper end of the fixing rod (311) and at an upper part with four upper plate fixing stud bolts (312b) to be coupled with four corner parts of the upper plate (220).

Further, as shown in FIG. 8, the lower plate fixing portion 320 for corner fixing includes a stud bolt 321 for lower plate fixing, a nut 322, an elastic body 323, a mold 324 for compression fixing, and a reference plate 325, wherein the lower plate fixing stud (321) is fixed on the hull inner wall (1) provided with the lower plate (210), the nut (322) is fastened with the lower plate fixing stud (321) to fix the lower plate (210), the elastic body (323) is clamped at the lower plate fixing stud (321) and the elasticity is adjusted according to the deformation degree of the hull inner wall (1), the compression fixing die (324) is clamped at the lower plate fixing stud (321) to be laminated below the elastic body (323) to prevent the local damage of the lower plate (210), and the reference plate (325) adjusts the height according to the degree of deformation of the hull inner wall (1).

That is, in the present embodiment, the degree of elasticity (spring constant) may be differently set and fixed according to the deformation condition of the hull inner wall (1) of the cargo hold, and examples thereof may include a stud bolt (321), a nut (nut) (322), an elastic body (washer spring) (323), a compression fixing mold (mold) (324), and a reference plate (reference wedge) (325).

The lower plate fixing stud (321) is fixed to the inner wall (1) of the hull on which the lower plate (210) is provided. The stud bolt (321) can be fixed by a common fastening means such as welding.

A nut (322) is fastened to the lower plate fixing stud (321) to fix the lower plate (210).

The elastic body (323) is sandwiched between the lower plate fixing stud bolts (321), and is configured to adjust the degree of elasticity in accordance with the degree of deformation of the hull inner wall (1) of the lower plate (210). The elastic body (323) may be replaced with three stages or five stages or the like to adjust the degree of elasticity.

The compression fixing mold (324) is configured to be sandwiched at the lower plate fixing stud bolt (321) to be laminated under the elastic body (323) to prevent local damage of the lower plate (210), which may use a high-density PUF, compressed wood, or the like.

The reference plate (325) is fixed to the hull inner wall (1), and a stud bolt (321) is vertically fixed to the reference plate (325). The reference plate (325) is configured to be adjustable in height according to the degree of deformation of the hull inner wall (1) of the lower plate (210).

A filling plug (326) is provided in the remaining space of a fixing hole (through part) (H2) formed at the center of the lower plate (210) to play a role of preventing the lower plate (210) from being damaged.

Referring to fig. 9, the upper plate fixing portion (400) includes a nut (422), an elastic body (423), and a compression fixing mold (424), wherein the nut (422) is fastened with the upper plate fixing stud (312b) to fix the upper plate (220), the elastic body (423) is clamped at the upper plate fixing stud (312b) to adjust the degree of elasticity, and the compression fixing mold (424) is clamped at the upper plate fixing stud (312b) to be stacked under the elastic body (423) to prevent local damage of the upper plate (220).

A filling plug (426) is provided in the remaining space of a fixing hole (through part) (H) formed at the corner of the upper plate (220) to prevent the upper plate (220) from being damaged.

When the order of installation of the secondary insulation layer (200) and the primary insulation layer (100) (see fig. 12) is observed with reference to the drawings, the lower plate (210) is additionally fixed with the center fixing lower plate fixing portion (310) after the lower plate (210) is first fixed to the hull inner wall (1) with the corner fixing lower plate fixing portion (320).

The lower plate (210) is first fixed to the hull inner wall (1) by using the lower plate fixing part (320) for corner fixing, and the lower plate is fixed to the hull inner wall (1) by fastening the lower plate fixing stud bolts (321) welded to the hull inner wall (1) with nuts (322) in a state of being inserted into fixing holes (through parts) (H1) perforated near four corners of the lower plate (210).

Further, additional fixation of the lower plate (210) may be configured using the center fixing lower plate fixing portion (310), and by fastening the fixing rod (311) to the threaded portion (312a) of the fixing base (312), the lower plate (210) can be more firmly fixed to the hull inner wall (1). The fixing base 312 may be fixed to the upper surface of the lower plate 210 by a rivet (rivet) or the like.

Then, the upper plate (220) is divided and laminated on the lower plate (210) in the thickness direction, and the lower plate (210) is alternately arranged with the upper plate (220), so that heat loss that may occur in the interval between the lower plate (210) and the upper plate (220) can be minimized, and deformation due to the difference in degree can be reduced.

In this case, the upper plate (220) is fixed to the lower plate (210) by using the upper plate fixing part (400). Since the upper plate fixing part (400) is similar in arrangement to the corner fixing lower plate fixing part (320), detailed description thereof will be omitted.

When the arrangement of the lower plate (210) and the upper plate (220) is completed, the secondary membrane (201) and the primary heat insulating layer (100) are arranged on the upper plate (220) in sequence.

In the present embodiment, the primary thermal insulation layer (100) may be composed of a plurality of plywood as shown in fig. 12, or may be composed of a composite body of a combination of plywood (plywood), a thermal insulation material, and a composite material as shown in fig. 13 and has a thickness within 20 to 30% of the thickness of the secondary thermal insulation layer (200). At this time, the heat insulating material may be provided by any one of glass wool (glasswool), polyurethane foam (PUF), or fiber-reinforced polyurethane foam (R-PUF).

In the membrane type thermal insulation system of the cargo tank and the liquefied gas fuel container of the cryogenic liquefied gas carrier of the present invention configured as described above, as shown in fig. 10, the secondary thermal insulation layer (200) is divided and laminated in two stages of a plurality of plates, for example, the lower plate (210) and the upper plate (220), and the lower plate (210) and the upper plate (220) are alternately arranged with each other, thereby minimizing heat loss that may occur in the interval between the plates. That is, since the thermal path (thermal path) is extended, heat loss such as convection does not occur.

Further, as shown in fig. 11, the upper plate is divided and laminated to the lower plate (210) in the thickness direction and alternately arranged, so that it is possible to reduce deformation due to a temperature difference at the time of thermal shrinkage, thereby minimizing deformation of the secondary heat insulating layer.

In the case of conventionally increasing the thickness of a single panel for the purpose of improving thermal insulation, there is a limit in increasing the thickness of the panel because there is a limit in the thickness of the panel (a limit in the height of foaming), whereas in the case of stacking a plurality of panels in the present invention, there is no limit in increasing the thickness of the thermal insulation.

In other words, in the case of increasing the thickness of the single panel for the purpose of improving thermal insulation, thermal contraction occurs according to a temperature difference between the upper and lower portions of the secondary insulation layer, and the upper portion of the secondary insulation layer contracts more than the lower portion, and in the case of increasing the insulation thickness, the contraction amount thereof further increases, thus generating an interval between panels, whereas in the present invention, as a plurality of panels alternately arranged are configured in a sandwich form, plywood or composite material of the panel surface contracts less than urethane foam, thus reducing the contraction amount compared to the single panel, and furthermore, due to the alternate arrangement between the upper and lower panels, not only is the interval that may be generated between the panels small, but also heat loss that may be generated in the interval is not connected to the interval between the lower panels of the secondary insulation layer, thus greatly reducing the heat loss.

Further, the upper plate provided on the lower plate presses the lower plate downward, thereby having a function of restricting deformation of the lower plate, so that deformation occurring in the plate can be minimized, and thus the strength burden of the secondary membrane due to the deformation of the plate can be reduced.

As described above, the present invention is not limited to the embodiments described, and it will be apparent to those skilled in the art to which the present invention pertains that various modifications and variations can be made without departing from the spirit and scope of the invention.

Therefore, such modifications or variations are intended to fall within the scope of the claims of the present invention.

For example, in describing the present invention, the primary and secondary heat insulating layers are divided into a heat insulating layer adjacent to the liquefied gas and a heat insulating layer adjacent to the inner wall of the hull, respectively, and this is only an arbitrary limitation for convenience of description, and vice versa.

The expressions of the upper portion (upper side) and the lower portion (lower side) are arbitrarily set for convenience of description, and are not limited thereto, and may be inversely changed depending on the position and the direction of observation on the cargo compartment characteristics.