Vacuum insulation and refrigerator

Abstract

A vacuum insulation body is provided. The vacuum insulation body includes a support unit configured to maintain a vacuum space. The support unit includes a plurality of rods extending vertically between a first plate member and a second plate member. When the pitch of the rods is *a*, the elastic modulus of the material forming the rods is *E*, and when the cross-section of the rods is elliptical, the major axis radius is *n* and the minor axis radius is *m*, satisfying the following formula.

Description

Technical Field

[0001] This disclosure relates to vacuum insulation materials and refrigerators. Background Technology

[0002] Vacuum insulation is a product that suppresses heat transfer by creating a vacuum inside its body. Vacuum insulation reduces heat transfer via convection and conduction, and is therefore used in heating and refrigeration equipment. In traditional refrigerator insulation methods, although the applications differ between refrigeration and freezing, foam polyurethane insulation walls with a thickness of approximately 30 mm or more are typically used. However, this reduces the internal capacity of the refrigerator.

[0003] In order to increase the internal capacity of refrigerators, people have tried to apply vacuum insulation to refrigerators.

[0004] First, the applicant's Korean Patent No. 10-0343719 (cited in reference 1) has been published. According to reference 1, a method for preparing a vacuum insulation panel and constructing it within the wall of a refrigerator is disclosed, with the exterior of the vacuum insulation panel finished using a separately molded article of polystyrene foam. This method eliminates the need for additional foaming and improves the refrigerator's insulation performance. However, it increases manufacturing costs and complicates the manufacturing process. As another example, Korean Patent Publication No. 10-2015-0012712 (cited in reference 2) discloses a technique using a vacuum insulation material to provide the wall and additionally using a foam-filled material to provide the insulation wall. According to reference 2, this increases manufacturing costs and complicates the manufacturing process.

[0005] As another example, attempts have been made to use a single-product vacuum insulation material to form all the walls of a refrigerator. For instance, U.S. Patent Publication No. 20040226956A1 (cited in reference 3) discloses a technique for setting the insulation structure of a refrigerator to a vacuum state. However, it is difficult to achieve a practical level of insulation by providing sufficient vacuum to the refrigerator walls. Specifically, there are limitations such as difficulty in preventing heat transfer at the contact points between the outer and inner shells at different temperatures, difficulty in maintaining a stable vacuum state, and difficulty in preventing shell deformation due to the negative pressure of the vacuum state. Due to these limitations, the technique disclosed in reference 3 is limited to low-temperature refrigerators and is not applicable to general household use.

[0006] The applicant has filed Korean Patent Application No. 10-2015-0109627 entitled "Vacuum Insulation Body and Refrigerator" (cited in Reference 4). According to this technology, a vacuum insulation body applicable to a practical refrigerator is disclosed. Furthermore, Reference 4 discloses the pitch of the rods of the support unit arranged inside the vacuum insulation body.

[0007] The resin used in the manufacture of the support unit is a major factor causing gas release, and the use of expensive resin materials leads to increased manufacturing costs. Summary of the Invention

[0008] Technical issues

[0009] One embodiment provides a support unit construction in which the amount of resin required to operate the vacuum insulation is minimized.

[0010] The implementation also provides a method in which a pitch for the rods applied to the support unit is proposed.

[0011] The implementation also provides a vacuum pressure and an insulation thickness, under which the insulation efficiency of the vacuum insulation body is improved.

[0012] Solution

[0013] In one embodiment, the vacuum insulation body includes: a thermal resistance unit configured to reduce heat transfer between a first plate member and a second plate member; and a support unit configured to maintain the vacuum space, wherein the support unit includes a plurality of rods extending vertically between the first plate member and the second plate member, and when the pitch of the rods is a, the elastic modulus of the material forming the rods is E, and when the cross-section of the rods is elliptical, the major axis radius is n and the minor axis radius is m, satisfying the following formula. According to an embodiment, a basic method can be provided to provide the pitch between the rods of the vacuum insulation body to obtain a stable gap between the rods.

[0014] The thermal resistance unit may include a conductive impedance sheet that resists heat conduction along the wall of the vacuum space, and may further include a side frame connected to the conductive impedance sheet.

[0015] Additionally, the thermal resistance unit may include at least one radiation-resistant sheet disposed in a plate shape within the vacuum space, or may include a porous material that resists radiative heat transfer between the second plate member and the first plate member within the vacuum space.

[0016] Beneficial effects of the present invention

[0017] Economic feasibility may be higher due to the use of the minimum amount of resin required to operate the vacuum insulation.

[0018] The optimal pitch of the rods applied to the support unit can be recommended to ensure stable operation of the support unit while preventing excessive use of resin.

[0019] According to the described embodiment, the insulation efficiency of the vacuum insulation body can be improved. Attached Figure Description

[0020] Figure 1 This is a perspective view of a refrigerator according to an embodiment.

[0021] Figure 2 This is a schematic view showing the vacuum insulation used in the body and door of the refrigerator.

[0022] Figure 3 This is a view showing multiple embodiments of the internal structure of the vacuum space section.

[0023] Figure 4 This is a view showing multiple embodiments of the conductive impedance sheet and its surrounding components.

[0024] Figure 5 This is a view of the reshaped rod.

[0025] Figure 6 This is a cross-sectional view of the rod.

[0026] Figure 7 A reference view used to explain the pressure per unit area applied to a unit bar.

[0027] Figure 8 The graphs show the changes in thermal insulation performance and gas conductivity relative to vacuum pressure, as demonstrated by applying simulations.

[0028] Figure 9 It is a graph showing the power consumption efficiency of a refrigerator depending on the insulation thickness, based on simulations, specifically the power consumption curve of the pollux model with the optimal vacuum insulation thickness.

[0029] Figure 10 The graph shows the thermal conductivity of the gas at 0.0089m and 0.12m, where 0.0089m and 0.12m are the minimum and maximum insulation thicknesses of the vacuum insulator.

[0030] Figure 11 The table was obtained by changing the vacuum pressure to simulate the thermal conductivity of the gas when the insulation thickness was about 0.12 m. Detailed Implementation

[0031] Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings. However, the present invention can be embodied in many different forms and should not be construed as limited to the embodiments described herein, and those skilled in the art who understand the spirit of the invention can readily implement other embodiments included within the same conceptual scope by adding, changing, deleting, and adding components; rather, it should be understood that they are also included within the scope of the present invention.

[0032] The accompanying drawings shown below may differ from the actual product, or exaggerated, simplified, or detailed descriptions may be omitted, which is helpful in understanding the technical concept of the invention. They should not be construed as limiting.

[0033] In the following description, vacuum pressure refers to any specific pressure state below atmospheric pressure. Additionally, the expression "A has a higher vacuum degree than B" means that the vacuum pressure of A is lower than the vacuum pressure of B.

[0034] Figure 1 This is a perspective view of a refrigerator according to an embodiment.

[0035] refer to Figure 1 The refrigerator 1 includes: a main body 2 having a compartment 9 for storing items; and a door 3 configured to open / close the main body 2. The door 3 can be configured to rotate or slide to open / close the compartment 9. The compartment 9 can provide at least one of a refrigerator compartment and a freezer compartment.

[0036] Multiple components constitute a refrigeration cycle system in which cold air is supplied to chamber 9. These components include, for example, a compressor 4 for compressing the refrigerant; a condenser 5 for condensing the compressed refrigerant; an expander 6 for expanding the condensed refrigerant; and an evaporator 7 for evaporating the expanded refrigerant to obtain heat. As a typical configuration, a fan can be installed adjacent to the evaporator 7, and fluid blown from the fan can pass through the evaporator 7 and then be blown into chamber 9. The refrigeration load can be controlled by adjusting the fan's blowing volume and direction, by adjusting the amount of refrigerant circulating, or by adjusting the compressor's compression rate, thereby enabling control of the refrigeration or freezing space.

[0037] Figure 2 This is a schematic view showing the vacuum insulation used in the body and door of the refrigerator. Figure 2 In the diagram, the main body-side vacuum insulation is shown with the top and side walls removed, and the door-side vacuum insulation is shown with a portion of the front wall removed. Furthermore, for ease of understanding, a segment of the conductive impedance sheet is schematically shown.

[0038] refer to Figure 2The vacuum insulation body includes: a first plate member 10 for providing a wall for a low-temperature space; a second plate member 20 for providing a wall for a high-temperature space; and a vacuum space portion 50 defined as a gap between the first plate member 10 and the second plate member 20. Furthermore, the vacuum insulation body includes conductive impedance sheets 60 and 63 to prevent thermal conduction between the first plate member 10 and the second plate member 20. A sealing portion 61 for sealing the first plate member 10 and the second plate member 20 is configured to keep the vacuum space portion 50 sealed. When the vacuum insulation body is applied to a refrigerator or heating cabinet, the first plate member 10 may be referred to as the inner shell, and the second plate member 20 may be referred to as the outer shell. A machine room 8 housing components that provide the refrigeration cycle is placed on the lower rear side of the main body of the vacuum insulation body, and an exhaust port 40 is provided on either side of the vacuum insulation body, the exhaust port 40 being used to create a vacuum state by venting air from the vacuum space portion 50. In addition, a pipe 64 can be installed through the vacuum space 50 to install defrost water pipes and electrical wires.

[0039] The first plate member 10 may define at least a portion of the wall for providing the first space. The second plate member 20 may define at least a portion of the wall for providing the second space. The first space and the second space may be defined as spaces with different temperatures. Here, the wall of each space may be not only a wall in direct contact with the space, but also a wall that is not in contact with the space. For example, the vacuum insulation of this embodiment may also be applied to products that also have separate walls in contact with each space.

[0040] The heat transfer factors that cause the loss of insulation effect of the vacuum insulation body are: heat conduction between the first plate member 10 and the second plate member 20, heat radiation between the first plate member 10 and the second plate member 20, and gas conduction in the vacuum space 50.

[0041] Hereinafter, the thermal resistance unit is configured to reduce insulation losses related to these heat transfer factors. Furthermore, the vacuum insulation body and refrigerator of this embodiment do not exclude the possibility of providing another insulation device on at least one side of the vacuum insulation body. Therefore, it is also possible to provide an insulation device using foam or the like on the other side of the vacuum insulation body.

[0042] The thermal resistance unit may include a conductive impedance sheet that resists heat conduction along the wall of the third space, and the thermal resistance unit may also include a side frame connected to the conductive impedance sheet. The conductive impedance sheet and the side frame will become clear from the following description.

[0043] Additionally, the thermal resistance unit may include at least one radiation-resistant sheet disposed in a plate-like manner within the third space, or may include a porous material within the third space that resists radiative heat transfer between the second plate member and the first plate member. The radiation-resistant sheet and the porous material will become clear from the following description.

[0044] Figure 3 This is a view showing multiple embodiments of the internal structure of the vacuum space section.

[0045] First, refer to Figure 3 A. The vacuum space 50 can be provided in a third space, the pressure of which differs from that of the first and second spaces, preferably being a vacuum state, thereby reducing insulation loss. The temperature of the third space can be set between the temperatures of the first and second spaces. Since the third space is set as a vacuum state, the first plate member 10 and the second plate member 20 are subjected to a force that contracts in the direction that brings them closer together due to the force corresponding to the pressure difference between the first and second spaces. Therefore, the vacuum space 50 can deform in the direction that reduces the distance between the plate members. In this case, insulation loss may occur due to the increase in thermal radiation caused by the contraction of the vacuum space 50 and the increase in thermal conductivity caused by the contact between the plate members 10 and 20.

[0046] A support unit 30 may be provided to reduce deformation of the vacuum space 50. The support unit 30 includes a rod 31. The rod 31 may extend in a substantially vertical direction relative to the plate members to support the distance between the first plate member and the second plate member. A support plate 35 may be additionally provided at at least either end of the rod 31. The support plate 35 may connect at least two or more rods 31 to each other to extend in a horizontal direction relative to the first plate member 10 and the second plate member 20. The support plate 35 may be plate-shaped or grid-shaped to reduce the contact area between the support plate and the first plate member 10 or the second plate member 20, thereby reducing heat transfer. The rods 31 and the support plate 35 are fixed to each other at least partially to be inserted together between the first plate member 10 and the second plate member 20. The support plate 35 contacts at least one of the first plate member 10 and the second plate member 20 to prevent deformation of the first plate member 10 and the second plate member 20. Furthermore, based on the extension direction of the rod 31, the total cross-sectional area of ​​the support plate 35 is set to be greater than the total cross-sectional area of ​​the rod 31, so that the heat transferred through the rod 31 can be diffused through the support plate 35.

[0047] The support unit 30 can be made of a resin selected from PC, glass fiber PC, low-release PC, PPS and LCP to obtain high compressive strength, low release rate and low water absorption, low thermal conductivity, high compressive strength at high temperature and excellent processing performance.

[0048] The following describes a radiation-resistant sheet 32 ​​used to reduce thermal radiation between the first plate member 10 and the second plate member 20 passing through the vacuum space 50. The first plate member 10 and the second plate member 20 can be made of stainless steel, a material that is corrosion-resistant and provides sufficient strength. Stainless steel has a relatively high emissivity of 0.16, thus it can transfer a large amount of radiant heat. Furthermore, the support unit 30, made of resin, has a lower emissivity than the plate members and is not fully disposed on the inner surfaces of the first plate member 10 and the second plate member 20. Therefore, the support unit 30 has little effect on radiant heat. Therefore, the radiation-resistant sheet 32 ​​can be disposed in a plate shape over a large area of ​​the vacuum space 50 to focus on reducing the radiant heat transferred between the first plate member 10 and the second plate member 20. Products with low emissivity can preferably be used as the material for the radiation-resistant sheet 32. In an embodiment, aluminum foil with an emissivity of 0.02 can be used as the radiation-resistant sheet 32. Furthermore, since using a single radiation-damping sheet may not be sufficient to resist the transfer of radiant heat, at least two radiation-damping sheets 32 can be arranged at a certain distance so that the two radiation-damping sheets 32 do not contact each other. In addition, at least one radiation-damping sheet can be arranged in contact with the inner surface of the first plate member 10 or the second plate member 20.

[0049] Refer again Figure 3 B. The distance between the plate members is maintained by the support unit 30, and a porous material 33 can be filled in the vacuum space 50. The emissivity of the porous material 33 can be higher than that of the stainless steel material of the first plate member 10 and the second plate member 20. However, since the porous material 33 is filled in the vacuum space 50, the porous material 33 has high efficiency in resisting radiative heat transfer.

[0050] In this embodiment, a vacuum insulation body can be manufactured without using the radiation-resistant sheet 32.

[0051] refer to Figure 3 C. The support unit 30 for maintaining the vacuum space 50 may not be provided. The porous material 33 may be surrounded by the membrane 34 instead of the support unit 30. Here, the porous material 33 may be provided in a compressed state to maintain the gap in the vacuum space. The membrane 34, made of, for example, PE material, may be provided with perforations in it.

[0052] In this embodiment, the vacuum insulation body can be manufactured without the support unit 30. That is, the porous material 33 can perform the functions of both the radiation shielding sheet 32 ​​and the support unit 30.

[0053] Figure 4 This is a view showing multiple embodiments of the conductive impedance sheet and its surrounding portion. Figure 2The structure of the conductive impedance sheet is briefly shown in the figure, but a more detailed understanding should be obtained by referring to the accompanying drawings.

[0054] first, Figure 4 The conductive impedance sheet proposed in (a) can preferably be applied to the body-side vacuum insulation. Specifically, the first plate member 10 and the second plate member 20 are sealed to evacuate the interior of the vacuum insulation. In this case, heat transfer may occur between the two plate members due to their different temperatures. The conductive impedance sheet 60 is provided to prevent heat conduction between the two different types of plate members.

[0055] The conductive impedance sheet 60 may be provided with a sealing portion 61, at which both ends of the conductive impedance sheet 60 are sealed to define at least a portion of the wall for the third space and maintain a vacuum state. The conductive impedance sheet 60 may be configured as a thin foil in micrometers to reduce heat conduction along the wall for the third space. The sealing portion 610 may be configured as a welded portion. That is, the conductive impedance sheet 60 may be fused to the plate members 10 and 20. To induce a weld between the conductive impedance sheet 60 and the plate members 10 and 20, the conductive impedance sheet 60 and the plate members 10 and 20 may be made of the same material, and stainless steel may be used as the material. The sealing portion 610 is not limited to a welded portion and may be configured by a process such as cocking. The conductive impedance sheet 60 may be configured as a curved shape. Therefore, the thermal conduction distance of the conductive impedance sheet 60 is set to be longer than the linear distance of each plate member, thereby further reducing the amount of heat conduction.

[0056] Temperature changes occur along the conductive impedance sheet 60. Therefore, to prevent heat transfer to the outside of the conductive impedance sheet 60, a shielding portion 62 can be provided on the outside of the conductive impedance sheet 60 to provide insulation. In other words, in the refrigerator, the second plate member 20 is at a high temperature while the first plate member 10 is at a low temperature. Furthermore, heat conduction from high temperature to low temperature occurs in the conductive impedance sheet 60, resulting in a rapid temperature change. Therefore, when the conductive impedance sheet 60 is opened to the outside, significant heat transfer occurs through the opening. To reduce heat loss, the shielding portion 62 is provided on the outside of the conductive impedance sheet 60. For example, it is not preferable for the conductive impedance sheet 60 and its exposed portion not to function as a conductive impedance element when the conductive impedance sheet 60 is exposed to either a low-temperature space or a high-temperature space.

[0057] The shielding portion 62 can be configured as a porous material in contact with the outer surface of the conductive impedance sheet 60. The shielding portion 62 can be configured as a thermal insulation structure (e.g., a separate gasket placed outside the conductive impedance sheet 60). The shielding portion 62 can be configured as part of a vacuum insulation body, positioned facing the corresponding conductive impedance sheet 60 when the body-side vacuum insulation body is closed relative to the door-side vacuum insulation body. To reduce heat loss even when the body and door are open, the shielding portion 62 can preferably be configured as a porous material or a separate thermal insulation structure.

[0058] Figure 4 The conductive impedance sheet proposed in (b) can be preferably applied to door-side vacuum insulation. Figure 4 (b) describes in detail the relationship with Figure 4 (a) is a different part, and the same description is applied to the same part. Figure 4 (a) is the same as the part in the diagram. A side frame 70 is further provided on the outer side of the conductive impedance sheet 60. Components for sealing between the door and the main body, exhaust ports required for the exhaust process, and degassing ports for vacuum maintenance can be placed on the side frame 70. This is because it is convenient to install components in the vacuum insulation body on the main body side, but the installation position of the components is limited to the vacuum insulation body on the door side.

[0059] In a door-side vacuum insulation body, it is difficult to place the conductive impedance sheet 60 at the front end of the vacuum space (i.e., the corner portion of the vacuum space). This is because, unlike the main body, the corner edges of the door are exposed to the outside. More specifically, if the conductive impedance sheet 60 is placed at the front end of the vacuum space, the corner edges of the door are exposed to the outside, thus presenting a disadvantage: a separate insulation section must be provided to thermally insulate the conductive impedance sheet 60.

[0060] Figure 4 The conductive impedance sheet proposed in (c) can preferably be installed in a pipe passing through the vacuum space. Figure 4 (c) describes in detail the relationship with Figure 4 (a) and Figure 4 (b) is a different part, and the same description is applied to the same part. Figure 4 (a) and Figure 4 The same part as in (b). A section similar to the one in pipe 64 can be installed around the perimeter of pipe 64. Figure 4 (a) Conductive impedance sheet of the same shape, preferably a corrugated conductive impedance sheet 63. Therefore, the heat transfer path can be extended and deformation caused by pressure difference can be prevented. In addition, a separate shield can be provided to improve the thermal insulation performance of the conductive impedance sheet.

[0061] Return to reference Figure 4(a) Describe the heat transfer path between the first plate member 10 and the second plate member 20. The heat transferred through the vacuum insulation body can be divided into: surface conduction heat ①, which is conducted along the surface of the vacuum insulation body (more specifically, the conductive impedance sheet 60); support member conduction heat ②, which is conducted along the support unit 30 disposed within the vacuum insulation body; gas conduction heat ③, which is conducted through the internal gas in the vacuum space; and radiative heat transfer ④, which occurs through the vacuum space.

[0062] Heat transfer can be varied according to different design dimensions. For example, the support unit can be changed so that the first plate member 10 and the second plate member 20 can withstand vacuum pressure without deformation; the vacuum pressure can be changed; the distance between the plate members can be changed; and the length of the conductive impedance sheet can be changed. The heat transfer can be altered based on the temperature difference between the spaces (first space and second space) provided by the plate members respectively. In this embodiment, considering that the total heat transfer of the vacuum insulation is less than that of a typical insulation structure formed by polyurethane foam, a preferred configuration of the vacuum insulation has been found. In a typical refrigerator including an insulation structure formed by polyurethane foam, an effective heat transfer coefficient of 19.6 mW / mK can be achieved.

[0063] By comparing and analyzing the heat transfer of the vacuum insulation in this embodiment, the heat transfer of gas conduction heat ③ is likely the smallest. For example, the heat transfer of gas conduction heat ③ can be controlled to be equal to or less than 4% of the total heat transfer. Solid heat transfer, defined as the sum of surface conduction heat ① and support conduction heat ②, has the largest heat transfer. For example, the heat transfer of solid heat can reach 75% of the total heat transfer. Radiative heat transfer ③ has a smaller heat transfer than solid heat transfer, but a larger heat transfer than gas conduction heat transfer. For example, the heat transfer of radiative heat transfer ③ can account for about 20% of the total heat transfer.

[0064] Based on this heat transfer distribution, the effective heat transfer coefficients (eK: effective K) (W / mK) of surface conduction heat ①, support conduction heat ②, gas conduction heat ③, and radiation heat transfer ④ can follow the order of Formula 1.

[0065] [Formula 1]

[0066] eK 固体传热 >eK 辐射传热 >eK 气体传导热

[0067] Here, the effective heat transfer coefficient (eK) is a value that can be measured using the shape and temperature difference of the target product. The effective heat transfer coefficient (eK) is a value obtained by measuring the total heat transfer and the temperature of at least one heat transfer component. For example, the effective heat transfer coefficient is evaluated by measuring the calorific value (W) using a heat source that can be quantitatively measured in a refrigerator, measuring the temperature distribution (K) of the door using the heat transferred through the body and edges of the door respectively, and using the path of the heat transfer as a conversion value (m).

[0068] The effective heat transfer coefficient (eK) of the entire vacuum insulation is given by k = QL / AΔT. Here, Q represents the calorific value (W) and can be obtained using the calorific value of the heater. A represents the cross-sectional area of ​​the vacuum insulation (m²). 2 L represents the thickness (m) of the vacuum insulation, and ΔT represents the temperature difference.

[0069] For surface heat conduction, the conductive calorific value can be obtained from the temperature difference (ΔT) between the inlet and outlet of the conductive impedance sheet 60 or 63, the cross-sectional area (A) of the conductive impedance sheet, the length (L) of the conductive impedance sheet, and the thermal conductivity (k, which is a material property of the material and can be obtained in advance). For support heat conduction, the conductive calorific value can be obtained from the temperature difference (ΔT) between the inlet and outlet of the support unit 30, the cross-sectional area (A) of the support unit, the length (L) of the support unit, and the thermal conductivity (k) of the support unit. Here, the thermal conductivity of the support unit is a material property of the material and can be obtained in advance. By subtracting the surface heat conduction and support heat conduction from the total heat transfer of the entire vacuum insulation, the sum of gas heat conduction ③ and radiative heat transfer ④ can be obtained. By significantly reducing the vacuum level of the vacuum space 50, when there is no gas heat conduction, the ratio of gas heat conduction ③ to radiative heat transfer ④ can be obtained by evaluating radiative heat transfer.

[0070] When porous material is provided inside the vacuum space section 50, the heat conduction ⑤ of the porous material can be the sum of the heat conduction ② of the support member and the radiative heat transfer ④. The heat conduction of the porous material can vary depending on several variables (including the type and quantity of the porous material).

[0071] According to one embodiment, the temperature difference ΔT1 between the geometric center formed by adjacent rods 31 and the point where each rod 31 is located can preferably be set to less than 0.5°C. Additionally, the temperature difference ΔT2 between the geometric center formed by adjacent rods 31 and the edge of the vacuum insulation can preferably be set to less than 0.5°C. In the second plate member 20, the temperature difference between the average temperature of the second plate and the temperature at the point where the heat transfer path through the conductive impedance sheet 60 or 63 intersects with the second plate can be the largest. For example, when the second space is a region hotter than the first space, the temperature at the point where the heat transfer path through the conductive impedance sheet intersects with the second plate member becomes the lowest. Similarly, when the second space is a region colder than the first space, the temperature at the point where the heat transfer path through the conductive impedance sheet intersects with the second plate member becomes the highest.

[0072] This means that heat transferred through other points, besides the surface conduction heat through the conductive impedance sheet, should be controlled, and the full heat transfer requirement of the vacuum insulation body can only be met when surface conduction heat accounts for the maximum heat transfer. Therefore, the temperature change of the conductive impedance sheet can be controlled to be greater than the temperature change of the plate component.

[0073] The physical properties of the components constituting a vacuum insulation body will be described. In a vacuum insulation body, the force generated by the vacuum pressure is applied to all components. Therefore, components with a certain strength (N / m) are preferably used. 2 (materials).

[0074] In this case, plate members 10 and 20, as well as the side frame 70, can preferably be made of a material with sufficient strength that will not be damaged by uniform vacuum pressure. For example, when the number of rods 31 is reduced to limit heat conduction by the support members, deformation of the plate members due to vacuum pressure may occur, which could adversely affect the appearance of the refrigerator. The radiation-resistant sheet 32 ​​can preferably be made of a material with low emissivity and easy thin-film processing. In addition, the radiation-resistant sheet 32 ​​should ensure sufficient strength to prevent deformation due to external impact. The support unit 30 is strong enough to support the forces generated by vacuum pressure and withstand external impacts, and is also machinable. The conductive impedance sheet 60 can preferably be made of a sheet-like material that can withstand vacuum pressure.

[0075] In one embodiment, the plate members, side frames, and conductive impedance sheets can be made of stainless steel, a material of the same strength. The radiation-resistant sheet can be made of aluminum, which is weaker than stainless steel. The support unit can be made of resin, which is weaker than aluminum.

[0076] Unlike strength analysis from a material perspective, analysis must be conducted from a stiffness perspective. Stiffness (N / m) is the property of not easily deforming. Even using the same material, its stiffness can vary depending on its shape. The conductive impedance sheet 60 or 63 can be made of a material with a certain strength, but the stiffness of this material is preferably low to increase thermal resistance and minimize radiative heat, since the conductive impedance sheet stretches uniformly without any bumps or depressions when vacuum pressure is applied. The radiation-damping sheet 32 ​​requires a certain degree of stiffness to prevent contact with another component due to deformation. In particular, the edge portions of the radiation-damping sheet may generate conductive heat due to sagging caused by the sheet's own load. Therefore, a certain degree of stiffness is required. The support unit 30 needs sufficient stiffness to withstand compressive stresses from the plate member and external impacts.

[0077] In one embodiment, preferably, the plate members and side frames have the highest stiffness to prevent deformation caused by vacuum pressure. Preferably, the support units, particularly the rods, have the second highest stiffness. Preferably, the radiation-resistant sheet has a stiffness lower than the support units but higher than the conductive impedance sheet. Finally, preferably, the conductive impedance sheet can be made of a material that is easily deformed by vacuum pressure and has the lowest stiffness.

[0078] Even when the porous material 33 is filled in the vacuum space 50, preferably, the stiffness of the conductive impedance sheet can be the lowest, and preferably, the stiffness of the plate member and the side frame can be the highest.

[0079] The following describes the construction and characteristics of the support unit and the pitch of the rods. The pitch of rod 31 can affect the cross-sectional shape of the rod, the length of the rod, the material of the rod, and the vacuum pressure. Furthermore, the pitch of rod 31 can affect the material and thickness of the plate member. However, the plate member can apply static loads to the rods over a thin and large area; therefore, the plate member does not significantly affect the pitch of the rods.

[0080] The inventors discovered that the pitch of the rod is defined by a predetermined relationship based on the rod 31 bearing the ultimate buckling stress, and the rod will not even break due to stress generated by the vacuum pressure of the vacuum insulation. This will be described below.

[0081] Figure 5 This is a view showing the state in which the rod has been reshaped. Figure 6 This is a cross-sectional view of the rod.

[0082] refer to Figure 5 The buckling load of the rod is caused by Given. Here, F cr Let L be the buckling load of the rod, I be the length of the rod, E be the moment of inertia, and E be the elastic modulus of the rod material. Additionally, the moments of inertia of the elliptical cylinder in the x-axis and y-axis directions are... and When the cross-section of the rod is elliptical, assuming the rod is undamaged, the moment of inertia applied in the direction of the highest buckling load is l. x This is because m is less than n, and buckling occurs in the x-direction.

[0083] Formula 2 is proposed when the moment of inertia in the x-direction is introduced into the formula for the buckling load of the rod.

[0084] [Formula 2]

[0085]

[0086] Where F cr Let L be the buckling load of the rod, I be the length of the rod, E be the moment of inertia, E be the elastic modulus of the material providing the rod, m be the minor axis radius of the rod's cross-section, and n be the major axis radius of the rod's cross-section. The length L of the rod is equal to the insulation thickness of the vacuum insulation.

[0087] The buckling stress is a value obtained by dividing the buckling load by the cross-sectional area of ​​the bar and can be given by Equation 3.

[0088] [Formula 3]

[0089]

[0090] in It is the buckling load, F cr is the buckling load of the rod, A is the cross-sectional area of ​​the rod, L is the length of the rod, I is the moment of inertia, E is the elastic modulus of the material providing the rod, m is the minor axis radius of the rod's cross-section, and n is the major axis radius of the rod's cross-section.

[0091] As can be seen from Formula 3, if the stress applied to the rod exceeds... The rod will break.

[0092] The stress applied per unit area will be described with reference to the accompanying drawings. Figure 7 On the single rod shown, the stress acts on a unit area according to the pressure applied to the rod.

[0093] refer to Figure 7 When the intervals between the pitches of rods 31 in the left and right directions are the same, it can be considered that the pressure applied to a unit area set at the intervals of the rods is the same as the pressure applied to a single rod.

[0094] Therefore, the stress applied to each rod 31 can be given by Equation 4.

[0095] [Formula 4]

[0096]

[0097] in is the vacuum stress applied to the rod, 'a' is the rod pitch, and 'P' is the pressure applied per unit area.

[0098] According to Equation 4, the buckling stress of the rod is the same as the pressure applied to the rod. That is, the rod will break when the vacuum stress caused by the vacuum pressure within the vacuum insulation reaches the buckling stress. This is summarized in Equation 5 as follows.

[0099] [Formula 5]

[0100]

[0101] Where L is the length of the rod, E is the elastic modulus of the material providing the rod, m is the minor axis radius of the rod's cross-section, n is the major axis radius of the rod's cross-section, a is the rod's pitch, and P is the pressure applied to plate member 10 and plate member 20 (i.e., the value obtained by subtracting the pressure of the vacuum space from atmospheric pressure).

[0102] Formula 5 can be modified as shown in Formula 6.

[0103] [Formula 6]

[0104]

[0105] Formula 6 on the left corresponds to the sum of the elements of the cross-sectional area of ​​the rod and the elastic modulus of the rod in Formula 5.

[0106] When the pressure applied to the vacuum insulation on the right and the length of the rod (the thickness of the thermal insulation) are determined, the cross-sectional shape of the rod (another element) and the material of the rod have a proportional relationship determined according to each index.

[0107] The following facts become clear through Formula 6 above.

[0108] First, all other things being equal, for safety reasons, the square of the pitch of the rod must be proportional to the square root of the pressure applied to the plate member.

[0109] Second, all other things being equal, for safety reasons, the pitch of the rod must be inversely proportional to the length of the rod.

[0110] Third, all other things being equal, for safety reasons, the pitch of the rod must be inversely proportional to the square root of the elastic modulus of the rod material.

[0111] Fourth, all other things being equal, the pitch of the rod should be inversely proportional to the 3 / 2 power of the radius of the major axis of the elliptical cross-section of the rod.

[0112] Fifth, all other things being equal, the pitch of the rod must be inversely proportional to the square root of the minor axis of the elliptical cross-section of the rod.

[0113] Sixth, all other things being equal, when the cross-section of the rod is circular, the pitch of the rod must be inversely proportional to the cross-sectional area.

[0114] Seventh, when other conditions are the same, as long as the insulation thickness of the vacuum insulation body and the width of the vacuum pressure are determined, the pitch and cross-sectional shape of the rod can be determined by a predetermined relationship.

[0115] As can be seen from Formula 6, obtaining the maximum / minimum values ​​of the insulation thickness and the maximum / minimum values ​​of the pressure applied to the vacuum insulation body is crucial for achieving the highest insulation efficiency of the vacuum insulation body. The process for obtaining these maximum / minimum values ​​of insulation thickness and pressure applied to the vacuum insulation body will be described below.

[0116] Figure 8 The graphs show the changes in thermal insulation performance and gas conductivity relative to vacuum pressure, as demonstrated by applying simulations.

[0117] refer to Figure 8 As can be seen, with decreasing vacuum pressure, i.e., increasing vacuum level, the heat load decreases compared to typical products formed by polyurethane foam, especially in the case of only the main body (curve 1) or when the main body and door are connected together (curve 2), thus improving insulation performance. However, it can be seen that the degree of improvement in insulation performance gradually decreases. Furthermore, it can be seen that gas conductivity decreases with decreasing vacuum pressure (curve 3). However, it can be seen that despite decreasing vacuum pressure, the ratio of improvement in insulation performance to improvement in gas conductivity gradually decreases. Therefore, it is preferable to minimize the vacuum pressure as much as possible. However, achieving excessively high vacuum pressure requires a long time and incurs significant costs due to excessive use of degassing agents.

[0118] The greater the insulation thickness, the better the insulation efficiency, but the greater the insulation thickness, the smaller the internal space of the refrigerator.

[0119] The minimum insulation thickness of a vacuum insulator will be described in the context above.

[0120] Figure 9 It is a graph showing the power consumption efficiency of a refrigerator depending on the insulation thickness, based on simulations, specifically the power consumption curve of the pollux model with the optimal vacuum insulation thickness.

[0121] First, the minimum thickness of a vacuum insulation material is considered to be approximately 4 mm, which is the physical limit for the size of the degassing agent inside the vacuum insulation material. However, not only would the size of the degassing agent be reduced, but the power consumption would also be excessive.

[0122] Even though improved insulation performance can be achieved by using vacuum insulation, if power consumption is too high, the effect is not satisfactory even compared to refrigerators using polyurethane foam according to existing technology. Against this backdrop, the inventors have discovered that when the insulation thickness is less than... Figure 9 The power consumption increases sharply at the point where the slope of the curve becomes -1. The minimum insulation thickness in the curve is 8.9 mm. Of course, if the insulation thickness is at the point where the slope of the curve is -1, the improvement in power consumption gradually decreases.

[0123] As a result of the above discussion, the minimum thickness of the vacuum insulation body can be determined to be approximately 8.9 mm (0.0098 m).

[0124] While increasing the thickness of the vacuum insulation improves insulation efficiency, it also reduces the internal volume of the refrigerator, which is not preferable. Therefore, the maximum thickness of the vacuum insulation can be set when its thickness is substantially the same as that of the refrigerator body using polyurethane foam according to existing technology.

[0125] Currently, the most efficient refrigerator body size is approximately 1500 liters, and the internal volume of the refrigerator is approximately 900 liters. Additionally, the refrigerator walls have a capacity of approximately 600 liters. Assuming each side of the body is square, the thickness of the five sides excluding the door is approximately 0.12m.

[0126] As a result of the above discussion, the maximum thickness of the vacuum insulation body can be determined to be approximately 0.12 m.

[0127] like Figure 8 As shown, the lower the vacuum pressure of a vacuum insulator, the lower the gas thermal conductivity, thus improving the insulation performance; the higher the vacuum pressure, the higher the gas thermal conductivity, thus worsening the insulation performance.

[0128] The minimum permissible insulation performance can be considered as the case of insulation provided by polyurethane foam according to relevant technologies. Figure 10 The graph shows the thermal conductivity of the gas at 0.0089m and 0.12m, where 0.0089m and 0.12m are the minimum and maximum insulation thicknesses of the vacuum insulator.

[0129] refer to Figure 10 When the insulation thickness is 0.0089 m at a polyurethane thermal conductivity of 0.0196 W / mK, the maximum insulation thickness of the vacuum insulation can be 8.3 × 10⁻⁶ m. -2 Entrust.

[0130] Based on the above, the maximum value of the vacuum pressure can be determined to be 8.3 × 10⁻⁶. -2 Entrust.

[0131] Since the thermal conductivity of gases decreases with decreasing vacuum pressure, the lowest possible vacuum pressure is preferred for vacuum insulation. However, as the exhaust time increases, the improvement in gas heat conduction becomes less significant once the vacuum pressure drops to a certain level.

[0132] Given the above context, the vacuum pressure is gradually decreased to a constant value. When the improvement in the gas conductivity decreases, the vacuum pressure can be determined. The constant value for decreasing the vacuum pressure is set at 0.1. -n Furthermore, as the exponent increases to a negative value, the width decreases. This is because, for exhaust, as the exponent increases to a negative value, the exhaust time becomes longer. For example, according to the sequence 1.1E... -07 1.0E -07 9.9E -08 9.8E -08 9.7E -08 The vacuum pressure was used to simulate the degree of improvement in the thermal conductivity of the gas.

[0133] Even with the same gas thermal conductivity, a larger vacuum insulation thickness results in a lower vacuum pressure. Therefore, the insulation thickness of the vacuum insulation can be based on 0.12m (maximum). Here, the gas thermal conductivity is used... This formula can be applied to the thermal conductivity of all types of gases.

[0134] Figure 11 This table was obtained by simulating the thermal conductivity of gases under varying vacuum pressures when the insulation thickness is approximately 0.12 m. (Reference) Figure 11 When the vacuum pressure is 9.9 × 10 -9 When the temperature drops, the improvement in the thermal conductivity of the gas decreases to about 1% or less.

[0135] Based on the above, the minimum vacuum pressure can be determined to be 9.9 × 10⁻⁶. -9 Entrust.

[0136] As a result of the above study, the maximum and minimum insulation thickness of the vacuum insulation body were 0.12 m and 0.0089 m, respectively, and the maximum and minimum vacuum pressure of the vacuum insulation body were 8.3 × 10⁻⁶ m and 8.3 × 10⁻⁶ m, respectively. -2 Tor and 9.9×10 -9 Entrust.

[0137] This result can be substituted into Equation 6. Subtract the pressure applied per unit area prior to this from the vacuum pressure of the vacuum insulator at atmospheric pressure. When subtracting 8.3 × 10 from atmospheric pressure of 101,325 Pa... -2 Torr (11.0666 Pa) and 9.9 × 10 -9Tor (1.32x10) -6 When the Pa is 101,313.933 Pa and 101,325 Pa, respectively, the values ​​can be obtained.

[0138] As a result, in Formula 6, the maximum / minimum insulation thickness L of the vacuum insulation body is 0.12 m and 0.0089 m, respectively, and the maximum / minimum pressure P applied per unit area can be 101,313.933 Pa and 101,325 Pa.

[0139] If you substitute the above values ​​into Formula 6, you can obtain the value of Formula 7.

[0140] [Formula 7]

[0141]

[0142] In this case, each pitch 'a' of the rod must be greater than twice the minor axis and twice the major axis of the elliptical rod.

[0143] The specific numerical values ​​that produce the result of Formula 7 are represented by Formula 8.

[0144] [Formula 8]

[0145]

[0146] Referring to Equation 8, since the vacuum pressure decreases when the insulation thickness of the insulation body is large (0.12), the pressure applied per unit area increases (101325). As a result, it can be seen that the result of Equation 8 is divided into the time when the insulation thickness is large and the insulation thickness is small.

[0147] If the rod is circular, m and n are the same value, and the mean value of Equation 7 can be changed to (r is the radius of the rod). For ease of injection, the cross-section of the rod can preferably be set in a circular shape.

[0148] According to Formula 7, the cross-sectional area of ​​the rod and the pitch between the rods are proportional to each other according to a predetermined index.

[0149] Based on the above description, the support unit of the vacuum insulation body can be applied by utilizing the relationship between the material of the rod, the cross-sectional shape of the rod, and the pitch of the rod.

[0150] When Formula 7 is applied, when an element is amplified, it can be positively controlled by its correlation with other elements.

[0151] Of course, the safe use of the support unit can be further enhanced by using Formula 7 and adding an additional safety factor.

[0152] Although Formula 7 assumes that there is nothing in the vacuum space, it can be fully applied to basic security checks if the porous material is contained in the vacuum space.

[0153] The vacuum insulation material disclosed herein is preferably used in refrigerators. However, the application of vacuum insulation material is not limited to refrigerators, and it can be used in various devices, such as cryogenic refrigeration equipment, heating equipment, and ventilation equipment.

[0154] Industrial applicability

[0155] According to the embodiments, the support unit suitable for vacuum insulation can be designed more safely. Vacuum insulation and refrigerators that are closer to industrial applications can be obtained according to the embodiments. Therefore, industrial applications are expected to be available soon.

Claims

1. A vacuum insulation body, comprising: The first panel is configured to define at least a portion of a wall for use in the first space; The second panel is configured to define at least a portion of a wall for use in the second space; The sealing part is configured to seal the first plate and the second plate; A third space, disposed between the first plate and the second plate, is configured as a vacuum space, and the temperature of the third space is between the temperature of the first space and the temperature of the second space. as well as The support includes a plurality of rods disposed in the third space and configured to maintain the distance between the first plate and the second plate; A thermal resistance unit is configured to reduce heat transfer between the first plate and the second plate; as well as The gas in the third space is discharged through the exhaust port. The thickness of the third space in the direction between the first plate and the second plate ranges from 8.9 mm to 0.12 m. The vacuum pressure of the third space is equal to or greater than 9.9 × 10⁻⁶. -9 The value is less than or equal to 8.3 × 10⁻⁶. -2 The support corresponds to the thickness of the third space. Wherein, when the cross-section of the rod is an ellipse including a circle, the plurality of rods satisfy the formula ,and in: 'a' is the distance between two adjacent rods. E is the elastic modulus of the material forming the rod. n is the radius of the major axis of the cross-sectional shape of the rod, and m is the minor axis radius of the cross-sectional shape of the rod, and Wherein, the distance 'a' between two adjacent rods is greater than twice the minor axis diameter of the cross-sectional shape of the rod and greater than twice the major axis diameter of the cross-sectional shape of the rod.

2. The vacuum insulation body according to claim 1, wherein, The square of the distance 'a' between two adjacent rods is proportional to the square root of the pressure applied to one of the first or second plates.

3. The vacuum insulation body according to claim 1, wherein, In the direction between the first plate and the second plate, the distance 'a' between two adjacent rods is inversely proportional to the length of the rod.

4. The vacuum insulation body according to claim 1, wherein, The distance 'a' between two adjacent rods is inversely proportional to the square root of the elastic modulus E of the material forming the rods.

5. The vacuum insulation body according to claim 1, wherein, The distance 'a' between two adjacent rods is inversely proportional to the 3 / 2 power of the major axis radius 'n' of the cross-section of the rod.

6. The vacuum insulation body according to claim 1, wherein, The distance 'a' between two adjacent rods is inversely proportional to the square root of the minor axis radius 'm' of the cross-section of the rod.

7. The vacuum insulation body according to claim 1, wherein, The distance 'a' between two adjacent rods is inversely proportional to the area of ​​the cross-section when the rod has a circular cross-section.

8. The vacuum insulation body according to claim 1 further includes a support plate, the support plate being configured to contact one end comprising at least one of the first plate or the second plate and at least one of the rods.

9. A refrigerator, comprising: The main body has a vacuum insulation body to form an internal space, which is configured to store items; The door is configured to open and close the main body to allow access to the interior space from the outside space; The compressor is configured to compress the refrigerant; A condenser is configured to condense compressed refrigerant; An expander is configured to expand the condensed refrigerant; as well as An evaporator is configured to evaporate the expanded refrigerant to dissipate heat. in, The vacuum insulation body includes: The first panel is configured to define at least a portion of a wall for the interior space; The second plate is configured to define at least a portion of a wall for the external space; The sealing part is configured to seal the first plate and the second plate; A vacuum space is disposed between the first plate and the second plate, and the temperature of the vacuum space is between the temperature of the inner space and the temperature of the outer space; The support includes a plurality of rods disposed in the vacuum space and configured to maintain a distance between the first plate and the second plate. A thermal resistance unit is configured to reduce heat transfer between the first plate and the second plate; and The gas in the vacuum space is discharged through the exhaust port. The thickness of the vacuum space in the direction between the first plate and the second plate ranges from 8.9 mm to 0.12 m, and the vacuum space has a diameter of 8.3 × 10⁻⁶ m. -2 Up to 9.9×10 -9 The pressure on the tube corresponds to the thickness of the vacuum space. Wherein, when the cross-section of the rod is elliptical, the rod satisfies the first formula. ,and in: 'a' is the distance between two adjacent rods in the rod structure. E is the elastic modulus of the material forming the rod. n is the radius of the major axis of the cross-sectional shape of the rod, and m is the minor axis radius of the cross-sectional shape of the rod, and Wherein, the distance 'a' between two adjacent rods is greater than twice the minor axis diameter of the cross-sectional shape of the rod and greater than twice the major axis diameter of the cross-sectional shape of the rod.

10. The refrigerator according to claim 9, wherein, The distance between two adjacent rods is inversely proportional to the 3 / 2 power of the major axis radius n of the rod's cross-section.

11. The refrigerator according to claim 9, wherein, The distance between two adjacent rods is inversely proportional to the square root of the minor axis radius m of the rod's cross-section.

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