Patent Description:
A vacuum adiabatic body is a product for suppressing heat transfer by vacuumizing the interior of a body thereof. The vacuum adiabatic body may reduce heat transfer by convection and conduction, and hence is applied to heating apparatuses and refrigerating apparatuses. In a typical adiabatic method applied to a refrigerator, although it is differently applied in refrigeration and freezing, a foam urethane adiabatic wall having a thickness of about <NUM> or more is generally provided. However, the internal volume of the refrigerator is therefore reduced.

In order to increase the internal volume of a refrigerator, there is an attempt to apply a vacuum adiabatic body to the refrigerator.

First, <CIT> (Cited Document <NUM>) of the present applicant has been disclosed. According to Reference Document <NUM>, there is disclosed a method in which a vacuum adiabatic panel is prepared and then built in walls of a refrigerator, and the exterior of the vacuum adiabatic panel is finished with a separate molding as Styrofoam. According to the method, additional foaming is not required, and the adiabatic performance of the refrigerator is improved. However, fabrication cost is increased, and a fabrication method is complicated. As another example, a technique of providing walls using a vacuum adiabatic material and additionally providing adiabatic walls using a foam filling material has been disclosed in <CIT> (Cited Document <NUM>). According to Reference Document <NUM>, fabrication cost is increased, and a fabrication method is complicated.

As further another example, there is an attempt to fabricate all walls of a refrigerator using a vacuum adiabatic body that is a single product. For example, a technique of providing an adiabatic structure of a refrigerator to be in a vacuum state has been disclosed in U. Patent Laid-Open Publication No. <CIT> (Cited Document <NUM>). However, it is difficult to obtain a practical level of an adiabatic effect by providing a wall of the refrigerator with sufficient vacuum. In detail, there are limitations that it is difficult to prevent a heat transfer phenomenon at a contact portion between an outer case and an inner case having different temperatures, it is difficult to maintain a stable vacuum state, and it is difficult to prevent deformation of a case due to a negative pressure of the vacuum state. Due to these limitations, the technology disclosed in Reference Document <NUM> is limited to a cryogenic refrigerator, and does not provide a level of technology applicable to general households.

The present applicant has proposed a <CIT> (Cited Document <NUM>), titled vacuum adiabatic body and refrigerator. According to this technology, a vacuum adiabatic body that is capable of being applied to an actual refrigerator is disclosed. Also, Cited Document <NUM> discloses a pitch of a bar of a supporting unit disposed inside a vacuum adiabatic body.

A resins used in the manufacture of the support unit is a main factor causing outgassing, and use of expensive resin materials leads to an increase in manufacturing costs.

<CIT> discloses a vacuum adiabatic body that includes: a first plate member; a second plate member; a sealing part; a supporting unit; a heat resistance unit; and an exhaust port, wherein an extending part extending toward the third space to be coupled to the supporting unit is provided to at least one of the first and second plate members, and the extending part is formed to extend downward from an edge portion of the at least one of the first and second plate members.

Embodiments provide a configuration of a supporting unit in which an amount of resin required for an operation of a vacuum adiabatic body is minimally used.

An example not part of the claimed invention also provides a method in which a pitch of a bar applied to a supporting unit is proposed.

Embodiments also provide a vacuum pressure and an adiabatic thickness at which adiabatic efficiency of a vacuum adiabatic body is improved.

In one embodiment, a vacuum adiabatic body includes: a heat resistance unit configured to reduce a heat transfer amount between a first plate member and a second plate member; and a supporting unit configured to maintain a vacuum space part, wherein the supporting unit includes a plurality of bars extending in a vertical direction between the first plate member and the second plate member, and when a pitch of the bar is a, an elastic modulus of a material forming the bar is E, and a radius of a long axis is n and a radius of a short axis is m when a cross-section of the bar has an elliptical shape is n, the following equation: <MAT> is satisfied. According to a non-claimed example, a basic method of providing the pitch between the bars of the vacuum adiabatic body may be provided to obtain a stable interval of the bars.

The heat resistance unit may include a conductive resistance sheet that resists conduction of heat transferred along a wall of a vacuum space part and may further include a side frame coupled to the conductive resistance sheet.

Also, the heat resistance unit may include at least one radiation resistance sheet that is provided in a plate shape within the vacuum space part or may include a porous material that resists radiation heat transfer between the second plate member and the first plate member within the vacuum space part.

Since the amount of resin required for the operation of the vacuum adiabatic body is minimally used, the economical feasibility may be superior.

The pitch of the bar applied to the supporting unit may be optimally proposed to lead to the stable action of the supporting unit while suppressing the excessive use of the resin.

According to the embodiments, the adiabatic efficiency of the vacuum adiabatic body may be improved.

Hereinafter, exemplary embodiments will be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein, and a person of ordinary skill in the art, who understands the spirit of the present invention, may readily implement other embodiments included within the scope of the same concept by adding, changing, deleting, and adding components; rather, it will be understood that they are also included within the scope of the present invention.

The drawings shown below may be displayed differently from the actual product, or exaggerated or simple or detailed parts may be deleted, but this is intended to facilitate understanding of the technical idea of the present invention. It should not be construed as limited.

In the following description, the vacuum pressure means any pressure state lower than the atmospheric pressure. In addition, the expression that a vacuum degree of A is higher than that of B means that a vacuum pressure of A is lower than that of B.

<FIG> is a perspective view of a refrigerator according to an embodiment.

Referring to <FIG>, the refrigerator <NUM> includes a main body <NUM> provided with a cavity <NUM> capable of storing storage goods and a door <NUM> provided to open/close the main body <NUM>. The door <NUM> may be rotatably or slidably movably disposed to open/close the cavity <NUM>. The cavity <NUM> may provide at least one of a refrigerating compartment and a freezing compartment.

Parts constituting a freezing cycle in which cold air is supplied into the cavity <NUM>. In detail, the parts include a compressor <NUM> for compressing a refrigerant, a condenser <NUM> for condensing the compressed refrigerant, an expander <NUM> for expanding the condensed refrigerant, and an evaporator <NUM> for evaporating the expanded refrigerant to take heat. As a typical structure, a fan may be installed at a position adjacent to the evaporator <NUM>, and a fluid blown from the fan may pass through the evaporator <NUM> and then be blown into the cavity <NUM>. A freezing load is controlled by adjusting the blowing amount and blowing direction by the fan, adjusting the amount of a circulated refrigerant, or adjusting the compression rate of the compressor, so that it is possible to control a refrigerating space or a freezing space.

<FIG> is a view schematically showing a vacuum adiabatic body used in the main body and the door of the refrigerator. In <FIG>, a main body-side vacuum adiabatic body is illustrated in a state in which top and side walls are removed, and a door-side vacuum adiabatic body is illustrated in a state in which a portion of a front wall is removed. In addition, sections of portions at conductive resistance sheets are provided are schematically illustrated for convenience of understanding.

Referring to <FIG>, the vacuum adiabatic body includes a first plate member <NUM> for providing a wall of a low-temperature space, a second plate member <NUM> for providing a wall of a high-temperature space, a vacuum space part <NUM> defined as a gap part between the first and second plate members <NUM> and <NUM>. Also, the vacuum adiabatic body includes the conductive resistance sheets <NUM> and <NUM> for preventing thermal conduction between the first and second plate members <NUM> and <NUM>. A sealing part <NUM> for sealing the first and second plate members <NUM> and <NUM> is provided such that the vacuum space part <NUM> is in a sealing state. When the vacuum adiabatic body is applied to a refrigerating or heating cabinet, the first plate member <NUM> may be referred to as an inner case, and the second plate member <NUM> may be referred to as an outer case. A machine room <NUM> in which parts providing a freezing cycle are accommodated is placed at a lower rear side of the main body-side vacuum adiabatic body, and an exhaust port <NUM> for forming a vacuum state by exhausting air in the vacuum space part <NUM> is provided at any one side of the vacuum adiabatic body. In addition, a pipeline <NUM> passing through the vacuum space part <NUM> may be further installed so as to install a defrosting water line and electric lines.

The first plate member <NUM> may define at least one portion of a wall for a first space provided thereto. The second plate member <NUM> may define at least one portion of a wall for a second space provided thereto. The first space and the second space may be defined as spaces having different temperatures. Here, the wall for each space may serve as not only a wall directly contacting the space but also a wall not contacting the space. For example, the vacuum adiabatic body of the embodiment may also be applied to a product further having a separate wall contacting each space.

Factors of heat transfer, which cause loss of the adiabatic effect of the vacuum adiabatic body, are thermal conduction between the first and second plate members <NUM> and <NUM>, heat radiation between the first and second plate members <NUM> and <NUM>, and gas conduction of the vacuum space part <NUM>.

Hereinafter, a heat resistance unit provided to reduce adiabatic loss related to the factors of the heat transfer will be provided. Meanwhile, the vacuum adiabatic body and the refrigerator of the embodiment do not exclude that another adiabatic means is further provided to at least one side of the vacuum adiabatic body. Therefore, an adiabatic means using foaming or the like may be further provided to another side of the vacuum adiabatic body.

The heat resistance unit may include a conductive resistance sheet that resists conduction of heat transferred along a wall of a third space and may further include a side frame coupled to the conductive resistance sheet. The conductive resistance sheet and the side frame will be clarified by the following description.

Also, the heat resistance unit may include at least one radiation resistance sheet that is provided in a plate shape within the third space or may include a porous material that resists radiation heat transfer between the second plate member and the first plate member within the third space. The radiation resistance sheet and the porous material will be clarified by the following description.

<FIG> is a view illustrating various embodiments of an internal configuration of the vacuum space part.

First referring to <FIG>, the vacuum space part <NUM> may be provided in a third space having a pressure different from that of each of the first and second spaces, preferably, a vacuum state, thereby reducing an adiabatic loss. The third space may be provided at a temperature between the temperature of the first space and the temperature of the second space. Since the third space is provided as a space in the vacuum state, the first and second plate members <NUM> and <NUM> receive a force contracting in a direction in which they approach each other due to a force corresponding to a pressure difference between the first and second spaces. Therefore, the vacuum space part <NUM> may be deformed in a direction in which it is reduced. In this case, the adiabatic loss may be caused due to an increase in amount of heat radiation, caused by the contraction of the vacuum space part <NUM>, and an increase in amount of thermal conduction, caused by contact between the plate members <NUM> and <NUM>.

The supporting unit <NUM> may be provided to reduce deformation of the vacuum space part <NUM>. The supporting unit <NUM> includes a bar <NUM>. The bar <NUM> may extend in a substantially vertical direction with respect to the plate members to support a distance between the first plate member and the second plate member. A support plate <NUM> may be additionally provided on at least any one end of the bar <NUM>. The support plate <NUM> may connect at least two or more bars <NUM> to each other to extend in a horizontal direction with respect to the first and second plate members <NUM> and <NUM>. The support plate <NUM> may be provided in a plate shape or may be provided in a lattice shape so that an area of the support plate contacting the first or second plate member <NUM> or <NUM> decreases, thereby reducing heat transfer. The bars <NUM> and the support plate <NUM> are fixed to each other at at least one portion, to be inserted together between the first and second plate members <NUM> and <NUM>. The support plate <NUM> contacts at least one of the first and second plate members <NUM> and <NUM>, thereby preventing deformation of the first and second plate members <NUM> and <NUM>. In addition, based on the extending direction of the bars <NUM>, a total sectional area of the support plate <NUM> is provided to be greater than that of the bars <NUM>, so that heat transferred through the bars <NUM> may be diffused through the support plate <NUM>.

The supporting unit <NUM> may be made of a resin selected from PC, glass fiber PC, low outgassing PC, PPS, and LCP to obtain high compressive strength, a low outgassing and water absorption rate, low thermal conductivity, high compressive strength at a high temperature, and superior processability.

A radiation resistance sheet <NUM> for reducing heat radiation between the first and second plate members <NUM> and <NUM> through the vacuum space part <NUM> will be described. The first and second plate members <NUM> and <NUM> may be made of a stainless material capable of preventing corrosion and providing a sufficient strength. The stainless material has a relatively high emissivity of <NUM>, and hence a large amount of radiation heat may be transferred. In addition, the supporting unit <NUM> made of the resin has a lower emissivity than the plate members, and is not entirely provided to inner surfaces of the first and second plate members <NUM> and <NUM>. Hence, the supporting unit <NUM> does not have great influence on radiation heat. Therefore, the radiation resistance sheet <NUM> may be provided in a plate shape over a majority of the area of the vacuum space part <NUM> so as to concentrate on reduction of radiation heat transferred between the first and second plate members <NUM> and <NUM>. A product having a low emissivity may be preferably used as the material of the radiation resistance sheet <NUM>. In an embodiment, an aluminum foil having an emissivity of <NUM> may be used as the radiation resistance sheet <NUM>. Also, since the transfer of radiation heat may not be sufficiently blocked using one radiation resistance sheet, at least two radiation resistance sheets <NUM> may be provided at a certain distance so as not to contact each other. Also, at least one radiation resistance sheet may be provided in a state in which it contacts the inner surface of the first or second plate member <NUM> or <NUM>.

Referring back <FIG>, the distance between the plate members is maintained by the supporting unit <NUM>, and a porous material <NUM> may be filled in the vacuum space part <NUM>. The porous material <NUM> may have a higher emissivity than the stainless material of the first and second plate members <NUM> and <NUM>. However, since the porous material <NUM> is filled in the vacuum space part <NUM>, the porous material <NUM> has a high efficiency for resisting the radiation heat transfer.

In the present embodiment, the vacuum adiabatic body may be manufactured without the radiation resistance sheet <NUM>.

Referring to <FIG>, the supporting unit <NUM> for maintaining the vacuum space part <NUM> may not be provided. A porous material <NUM> may be provided to be surrounded by a film <NUM> instead of the supporting unit <NUM>. Here, the porous material <NUM> may be provided in a state of being compressed so that the gap of the vacuum space part is maintained. The film <NUM> made of, for example, a PE material may be provided in a state in which a hole is punched in the film <NUM>.

<FIG> is a view illustrating various embodiments of conductive resistance sheets and peripheral parts thereof. Structures of the conductive resistance sheets are briefly illustrated in <FIG>, but will be understood in detail with reference to the drawings.

First, a conductive resistance sheet proposed in <FIG> may be preferably applied to the main body-side vacuum adiabatic body. Specifically, the first and second plate members <NUM> and <NUM> are to be sealed so as to vacuumize the interior of the vacuum adiabatic body. In this case, since the two plate members have different temperatures from each other, heat transfer may occur between the two plate members. A conductive resistance sheet <NUM> is provided to prevent thermal conduction between two different kinds of plate members.

The conductive resistance sheet <NUM> may be provided with the sealing part <NUM> at which both ends of the conductive resistance sheet <NUM> are sealed to defining at least one portion of the wall for the third space and maintain the vacuum state. The conductive resistance sheet <NUM> may be provided as a thin foil in unit of micrometer so as to reduce the amount of heat conducted along the wall for the third space. The sealing parts <NUM> may be provided as welding parts. That is, the conductive resistance sheet <NUM> and the plate members <NUM> and <NUM> may be fused to each other. In order to cause a fusing action between the conductive resistance sheet <NUM> and the plate members <NUM> and <NUM>, the conductive resistance sheet <NUM> and the plate members <NUM> and <NUM> may be made of the same material, and a stainless material may be used as the material. The sealing parts <NUM> are not limited to the welding parts, and may be provided through a process such as cocking. The conductive resistance sheet <NUM> may be provided in a curved shape. Thus, a thermal conduction distance of the conductive resistance sheet <NUM> is provided longer than the linear distance of each plate member, so that the amount of thermal conduction may be further reduced.

A change in temperature occurs along the conductive resistance sheet <NUM>. Therefore, in order to block heat transfer to the exterior of the conductive resistance sheet <NUM>, a shielding part <NUM> may be provided at the exterior of the conductive resistance sheet <NUM> such that an adiabatic action occurs. In other words, in the refrigerator, the second plate member <NUM> has a high temperature and the first plate member <NUM> has a low temperature. In addition, thermal conduction from high temperature to low temperature occurs in the conductive resistance sheet <NUM>, and hence the temperature of the conductive resistance sheet <NUM> is suddenly changed. Therefore, when the conductive resistance sheet <NUM> is opened to the exterior thereof, heat transfer through the opened place may seriously occur. In order to reduce heat loss, the shielding part <NUM> is provided at the exterior of the conductive resistance sheet <NUM>. For example, when the conductive resistance sheet <NUM> is exposed to any one of the low-temperature space and the high-temperature space, the conductive resistance sheet <NUM> does not serve as a conductive resistor as well as the exposed portion thereof, which is not preferable.

The shielding part <NUM> may be provided as a porous material contacting an outer surface of the conductive resistance sheet <NUM>. The shielding part <NUM> may be provided as an adiabatic structure, e.g., a separate gasket, which is placed at the exterior of the conductive resistance sheet <NUM>. The shielding part <NUM> may be provided as a portion of the vacuum adiabatic body, which is provided at a position facing a corresponding conductive resistance sheet <NUM> when the main body-side vacuum adiabatic body is closed with respect to the door-side vacuum adiabatic body. In order to reduce heat loss even when the main body and the door are opened, the shielding part <NUM> may be preferably provided as a porous material or a separate adiabatic structure.

A conductive resistance sheet proposed in <FIG> may be preferably applied to the door-side vacuum adiabatic body. In <FIG>, portions different from those of <FIG> are described in detail, and the same description is applied to portions identical to those of <FIG>. A side frame <NUM> is further provided at an outside of the conductive resistance sheet <NUM>. A part for sealing between the door and the main body, an exhaust port necessary for an exhaust process, a getter port for vacuum maintenance, and the like may be placed on the side frame <NUM>. This is because the mounting of parts is convenient in the main body-side vacuum adiabatic body, but the mounting positions of parts are limited in the door-side vacuum adiabatic body.

In the door-side vacuum adiabatic body, it is difficult to place the conductive resistance sheet <NUM> at a front end portion of the vacuum space part, i.e., a corner side portion of the vacuum space part. This is because, unlike the main body, a corner edge portion of the door is exposed to the exterior. In more detail, if the conductive resistance sheet <NUM> is placed at the front end portion of the vacuum space part, the corner edge portion of the door is exposed to the exterior, and hence there is a disadvantage in that a separate adiabatic part should be configured so as to thermally insulate the conductive resistance sheet <NUM>.

A conductive resistance sheet proposed in <FIG> may be preferably installed in the pipeline passing through the vacuum space part. In <FIG>, portions different from those of <FIG> are described in detail, and the same description is applied to portions identical to those of <FIG>. A conductive resistance sheet having the same shape as that of <FIG>, preferably, a wrinkled conductive resistance sheet <NUM> may be provided at a peripheral portion of the pipeline <NUM>. Accordingly, a heat transfer path may be lengthened, and deformation caused by a pressure difference may be prevented. In addition, a separate shielding part may be provided to improve the adiabatic performance of the conductive resistance sheet.

A heat transfer path between the first and second plate members <NUM> and <NUM> will be described with reference back to <FIG>. Heat passing through the vacuum adiabatic body may be divided into surface conduction heat ① conducted along a surface of the vacuum adiabatic body, more specifically, the conductive resistance sheet <NUM>, supporter conduction heat ② conducted along the supporting unit <NUM> provided inside the vacuum adiabatic body, gas conduction heat ③ conducted through an internal gas in the vacuum space part, and radiation transfer heat ④ transferred through the vacuum space part.

The transfer heat may be changed depending on various depending on various design dimensions. For example, the supporting unit may be changed such that the first and second plate members <NUM> and <NUM> may endure a vacuum pressure without being deformed, the vacuum pressure may be changed, the distance between the plate members may be changed, and the length of the conductive resistance sheet may be changed. The transfer heat may be changed depending on a difference in temperature between the spaces (the first and second spaces) respectively provided by the plate members. In the embodiment, a preferred configuration of the vacuum adiabatic body has been found by considering that its total heat transfer amount is smaller than that of a typical adiabatic structure formed by foaming polyurethane. In a typical refrigerator including the adiabatic structure formed by foaming the polyurethane, an effective heat transfer coefficient may be proposed as <NUM> mW/mK.

By performing a relative analysis on heat transfer amounts of the vacuum adiabatic body of the embodiment, a heat transfer amount by the gas conduction heat ③ may become the smallest. For example, the heat transfer amount by the gas conduction heat ③ may be controlled to be equal to or smaller than <NUM>% of the total heat transfer amount. A heat transfer amount by solid conduction heat defined as a sum of the surface conduction heat ① and the supporter conduction heat ② is the largest. For example, the heat transfer amount by the solid conduction heat may reach <NUM>% of the total heat transfer amount. A heat transfer amount by the radiation transfer heat ③ is smaller than the heat transfer amount by the solid conduction heat but larger than the heat transfer amount of the gas conduction heat. For example, the heat transfer amount by the radiation transfer heat ③ may occupy about <NUM>% of the total heat transfer amount.

According to such a heat transfer distribution, effective heat transfer coefficients (eK: effective K) (W/mK) of the surface conduction heat ①, the supporter conduction heat ②, the gas conduction heat ③, and the radiation transfer heat ④ may have an order of Math Equation <NUM>.

Here, the effective heat transfer coefficient (eK) is a value that may be measured using a shape and temperature differences of a target product. The effective heat transfer coefficient (eK) is a value that may be obtained by measuring a total heat transfer amount and a temperature at least one portion at which heat is transferred. For example, a calorific value (W) is measured using a heating source that may be quantitatively measured in the refrigerator, a temperature distribution (K) of the door is measured using heats respectively transferred through a main body and an edge of the door of the refrigerator, and a path through which heat is transferred is calculated as a conversion value (m), thereby evaluating an effective heat transfer coefficient.

The effective heat transfer coefficient (eK) of the entire vacuum adiabatic body is a value given by k=QL/A△T. Here, Q denotes a calorific value (W) and may be obtained using a calorific value of a heater. A denotes a sectional area (m<NUM>) of the vacuum adiabatic body, L denotes a thickness (m) of the vacuum adiabatic body, and △T denotes a temperature difference.

For the surface conduction heat, a conductive calorific value may be obtained through a temperature difference (△T) between an entrance and an exit of the conductive resistance sheet <NUM> or <NUM>, a sectional area (A) of the conductive resistance sheet, a length (L) of the conductive resistance sheet, and a thermal conductivity (k) of the conductive resistance sheet (the thermal conductivity of the conductive resistance sheet is a material property of a material and may be obtained in advance). For the supporter conduction heat, a conductive calorific value may be obtained through a temperature difference (△T) between an entrance and an exit of the supporting unit <NUM>, a sectional area (A) of the supporting unit, a length (L) of the supporting unit, and a thermal conductivity (k) of the supporting unit. Here, the thermal conductivity of the supporting unit is a material property of a material and may be obtained in advance. The sum of the gas conduction heat ③, and the radiation transfer heat ④ may be obtained by subtracting the surface conduction heat and the supporter conduction heat from the heat transfer amount of the entire vacuum adiabatic body. A ratio of the gas conduction heat ③, and the radiation transfer heat ④ may be obtained by evaluating radiation transfer heat when no gas conduction heat exists by remarkably lowering a vacuum degree of the vacuum space part <NUM>.

When a porous material is provided inside the vacuum space part <NUM>, porous material conduction heat ⑤ may be a sum of the supporter conduction heat ② and the radiation transfer heat ④. The porous material conduction heat may be changed depending on various variables including a kind, an amount, and the like of the porous material.

According to an embodiment, a temperature difference △T<NUM> between a geometric center formed by adjacent bars <NUM> and a point at which each of the bars <NUM> is located may be preferably provided to be less than <NUM>. Also, a temperature difference △T<NUM> between the geometric center formed by the adjacent bars <NUM> and an edge portion of the vacuum adiabatic body may be preferably provided to be less than <NUM>. In the second plate member <NUM>, a temperature difference between an average temperature of the second plate and a temperature at a point at which a heat transfer path passing through the conductive resistance sheet <NUM> or <NUM> meets the second plate may be the largest. For example, when the second space is a region hotter than the first space, the temperature at the point at which the heat transfer path passing through the conductive resistance sheet meets the second plate member becomes lowest. Similarly, when the second space is a region colder than the first space, the temperature at the point at which the heat transfer path passing through the conductive resistance sheet meets the second plate member becomes highest.

This means that the amount of heat transferred through other points except the surface conduction heat passing through the conductive resistance sheet should be controlled, and the entire heat transfer amount satisfying the vacuum adiabatic body may be achieved only when the surface conduction heat occupies the largest heat transfer amount. To this end, a temperature variation of the conductive resistance sheet may be controlled to be larger than that of the plate member.

Physical characteristics of the parts constituting the vacuum adiabatic body will be described. In the vacuum adiabatic body, a force by vacuum pressure is applied to all of the parts. Therefore, a material having a strength (N/m<NUM>) of a certain level may be preferably used.

Under such circumferences, the plate members <NUM> and <NUM> and the side frame <NUM> may be preferably made of a material having a sufficient strength with which they are not damaged by even vacuum pressure. For example, when the number of bars <NUM> is decreased so as to limit the support conduction heat, deformation of the plate member occurs due to the vacuum pressure, which may bad influence on the external appearance of refrigerator. The radiation resistance sheet <NUM> may be preferably made of a material that has a low emissivity and may be easily subjected to thin film processing. Also, the radiation resistance sheet <NUM> is to ensure a strength enough not to be deformed by an external impact. The supporting unit <NUM> is provided with a strength enough to support the force by the vacuum pressure and endure an external impact, and is to have machinability. The conductive resistance sheet <NUM> may be preferably made of a material that has a thin plate shape and may endure the vacuum pressure.

In an embodiment, the plate member, the side frame, and the conductive resistance sheet may be made of stainless materials having the same strength. The radiation resistance sheet may be made of aluminum having a weaker strength that the stainless materials. The supporting unit may be made of resin having a weaker strength than the aluminum.

Unlike the strength from the point of view of materials, analysis from the point of view of stiffness is required. The stiffness (N/m) is a property that would not be easily deformed. Although the same material is used, its stiffness may be changed depending on its shape. The conductive resistance sheets <NUM> or <NUM> may be made of a material having a strength, but the stiffness of the material is preferably low so as to increase heat resistance and minimize radiation heat as the conductive resistance sheet is uniformly spread without any roughness when the vacuum pressure is applied. The radiation resistance sheet <NUM> requires a stiffness of a certain level so as not to contact another part due to deformation. Particularly, an edge portion of the radiation resistance sheet may generate conduction heat due to drooping caused by the self-load of the radiation resistance sheet. Therefore, a stiffness of a certain level is required. The supporting unit <NUM> requires a stiffness enough to endure a compressive stress from the plate member and an external impact.

In an embodiment, the plate member and the side frame may preferably have the highest stiffness so as to prevent deformation caused by the vacuum pressure. The supporting unit, particularly, the bar may preferably have the second highest stiffness. The radiation resistance sheet may preferably have a stiffness that is lower than that of the supporting unit but higher than that of the conductive resistance sheet. Lastly, the conductive resistance sheet may be preferably made of a material that is easily deformed by the vacuum pressure and has the lowest stiffness.

Even when the porous material <NUM> is filled in the vacuum space part <NUM>, the conductive resistance sheet may preferably have the lowest stiffness, and the plate member and the side frame may preferably have the highest stiffness.

Hereinafter, a configuration and characteristic of the supporting unit and a pitch of the bar will be described. The pitch of the bar <NUM> may affect a cross-sectional shape of the bar, a length of the bar, a material of the bar, and a vacuum pressure. In addition, the pitch of the <NUM> may affect a material and thickness of the plate member. However, the plate member may apply a static load to the bar on a thin and large area, and thus, the plate member may not have a great influence on the pitch of the bar.

The inventor has found that the pitch of the bar is defined by a predetermined relationship based on the fact that the bar <NUM> withstands limit buckling stress that does not break even by the stress due to the vacuum pressure of the vacuum adiabatic body. This will be described below.

<FIG> is a view illustrating a state in which the bar is remodeled, and <FIG> is a cross-sectional view of the bar.

Referring to <FIG>, a buckling load of the bar is given by <MAT>.

Here, Fcr is the buckling load of the bar, L is a length of the bar, I is inertia moment, and E is an elastic modulus of a material of the bar. Also, the inertia moment of an elliptical column is given by <MAT> and <MAT> in x-axis and y-axis directions. When a cross-section of the bar is elliptical, the inertia moment in a direction in which the highest buckling load applied to the bar without damage is applied will be lx. This is because m is less than n, and buckling is performed in the x direction.

When introducing the inertia moment in the x direction into the equation of the buckling load of the bar, Equation <NUM> is proposed.

Where Fcr is a buckling load of the bar, L is a length of the bar, I is inertia moment, E is an elastic modulus of a material providing the bar, m is a short-axis radius of a cross-section of the bar, and n is a long-axis radius of the cross-section of the bar. The length L of the bar may be equal to an adiabatic thickness of a vacuum adiabatic body.

Buckling stress is a value obtained by dividing the buckling load by the cross-section of the bar and may be given by Equation <NUM>.

Where αcr is a buckling load, Fcr is a buckling load of the bar, A is a cross-sectional area of the bar, L is a length of the bar, I is inertia moment, E is an elastic modulus of a material providing the bar, m is a short-axis radius of a cross-section of the bar, and n is a long-axis radius of the cross-section of the bar.

As seen through Equation <NUM>, if the stress applied to the bar exceeds αcr, the bar may be broken.

Stress per unit area on which the stress according to the pressure applied to the bar is applied to a unit bar illustrated in <FIG> will be described with reference to the reference view.

Referring to <FIG>, when intervals between the pitches of the bars <NUM> are the same in the left and right direction, the pressure applied to the unit area provided at the interval of the bars may be considered to be the same as the pressure applied to the unit bar.

Thus, the stress applied to the individual bars <NUM> may be given by Equation <NUM>.

Where αnormal is vacuum stress applied to the bar by the pressure, a is pitch of the bar, and P is a pressure applied to the unit area.

Buckling stress and a pressure applied to the bar according to Equation <NUM> may have the same value. That is to say, when a vacuum stress due to a vacuum pressure inside the vacuum adiabatic body reaches the buckling stress, the bar may be broken. This is summarized in Equation <NUM> as follows.

Where L is a length of the bar, E is an elastic modulus of a material providing the bar, m is a short-axis radius of a cross-section of the bar, n is a long-axis radius of the cross-section of the bar, a is a pitch of the bar, P is a pressure applied to plate members <NUM> and <NUM>, i.e., a value obtained by subtracting a pressure of a vacuum space part from an atmospheric pressure.

Equation <NUM> may be modified as shown in Equation <NUM>.

Equation <NUM> corresponds to the sum of elements of a cross-sectional area of the bar and an elastic modulus of the bar on a left side in Equation <NUM>.

When the pressure applied to the vacuum adiabatic body on a right side and a length of the bar (a thickness of the heat adiabatic body) are determined, a cross-sectional shape of the bar, which is another element, and a material of the bar have a proportional relation that is determined according to each index.

The following facts become clear through the above Equation <NUM>.

First, when the other conditions are the same, for safety, the square of the pitch of the bar has to be in proportional to the square root of the pressure exerted on the plate member.

Second, when the other conditions are the same, for safety, the pitch of the bar has to be in inverse proportion to the length of the bar.

Third, when the other conditions are the same, for safety, the pitch of the bar has to be in inverse proportion to the square root of the elastic modulus of the bar material.

Fourth, when the other conditions are the same, the pitch of the bars should be in inverse proportion to an index of <NUM>/<NUM> on the long axis of the elliptical cross-section of the bar.

Fifth, when the other conditions are the same, the pitch of the bar has to be in inverse proportion to the square root of the short axis of the elliptical cross-section of the bar.

Sixth, when the other conditions are the same, the pitch of the bar has to be in inverse proportion to the area of the cross-section when the cross-section of the bar is a circle.

Seventh, when the other conditions are the same, the pitch and cross-sectional shape of the bars may be determined with a predetermined mutual relationship as long as the adiabatic thickness of the vacuum adiabatic body and the width of the vacuum pressure are determined.

Referring to Equation <NUM>, it is seen that maximum/minimum values of the adiabatic thickness of the vacuum adiabatic body and maximum/minimum values of the pressure applied to the vacuum adiabatic body are obtained so as to obtain the highest adiabatic efficiency by the vacuum adiabatic body. Hereinafter, a process of obtaining the maximum/minimum values of the adiabatic thickness of the vacuum adiabatic body and the maximum/minimum values of the pressure applied to the vacuum adiabatic body will be described.

<FIG> illustrates graphs showing changes in adiabatic performance and changes in gas conductivity with respect to vacuum pressures by applying a simulation.

Referring to <FIG>, it may be seen that, as the vacuum pressure is decreased, i.e., as the vacuum degree is increased, a heat load in the case of only the main body (Graph <NUM>) or in the case where the main body and the door are joined together (Graph <NUM>) is decreased as compared with that in the case of the typical product formed by foaming polyurethane, thereby improving the adiabatic performance. However, it may be seen that the degree of improvement of the adiabatic performance is gradually lowered. Also, it may be seen that, as the vacuum pressure is decreased, the gas conductivity (Graph <NUM>) is decreased. However, it may be seen that, although the vacuum pressure is decreased, the ratio at which the adiabatic performance and the gas conductivity are improved is gradually lowered. Therefore, it is preferable that the vacuum pressure is decreased as low as possible. However, it takes long time to obtain excessive vacuum pressure, and much cost is consumed due to excessive use of a getter.

The more the adiabatic thickness increases, the more the increase of the adiabatic efficiency is better, but the more the adiabatic thickness increases, the more the internal space of the refrigerator is reduced.

The lowest value of the adiabatic thickness of the vacuum adiabatic body will be described under the above background.

<FIG> is a graph showing consumption efficiency of the refrigerator depending on an adiabatic thickness according to a simulation, i.e., a graph showing power consumption for a vacuum adiabatic thickness of a pollux model in which the efficiency of the power consumption is best.

First, the minimum value of the thickness of the vacuum adiabatic body is considered as about <NUM>, which is a physical limit of the getter size disposed inside the vacuum adiabatic body. However, the size of the getter may not only be reduced but also the power consumption is excessively large.

Even through an effect of improving the adiabatic performance to be obtained by using the vacuum adiabatic body is obtained, if the power consumption is excessively large, a good effect may not be obtained even compared with the refrigerator using the foamed urethane according to the related art. Under this background, the inventor has found that when the adiabatic thickness becomes smaller than a point at which the inclination becomes -<NUM> in the graph shown in <FIG>, the power consumption increases sharply. In the graph, the thickness is <NUM> as the lowest value of the adiabatic thickness. Of course, if the adiabatic thickness at the point where the inclination is -<NUM> in the graph, the improvement of the power consumption gradually decreases.

As a result of the above discussion, the minimum thickness of the vacuum adiabatic body may be determined to be about <NUM> (<NUM>).

As the thickness of the vacuum adiabatic body increases, the adiabatic efficiency is improved, but the internal volume of the refrigerator decreases, which is not preferable. Under this background, a case in which the thickness of the vacuum adiabatic body is substantially the same as that in the case of using the refrigerator body using the foamed urethane according to the related art may be set as the maximum thickness of the vacuum adiabatic body.

At present, the most efficient refrigerator body is about <NUM>,<NUM> liters in size, and the internal volume of the refrigerator is about <NUM> liters. Also, the refrigerator wall has capacity of about <NUM> liters. When assuming that each side of the body is provided as a square, the thickness of the five sides excluding the door is about <NUM>.

As a result of the above discussion, the maximum thickness of the vacuum adiabatic body may be determined to be about <NUM>.

As illustrated in <FIG>, the more the vacuum pressure of the vacuum adiabatic body decreases, the more the gas thermal conductivity decreases to improve the adiabatic performance, and the more the vacuum pressure increases, the more the gas thermal conductivity increases to deteriorate the adiabatic performance.

The minimum value of the adiabatic performance that is tolerated may be considered as a case of providing the adiabatic body by foaming the polyurethane according to the related art. <FIG> is a graph of gas thermal conductivity of <NUM> and <NUM>, which are minimum and maximum values of the adiabatic thickness of the vacuum adiabatic body.

Referring to <FIG>, the maximum value of the adiabatic thickness of the vacuum adiabatic body may be <NUM>. 3x10-<NUM> Torr when the adiabatic thickness at which the thermal conductivity of polyurethane is <NUM> W/mK is <NUM>.

On the basis of the above, the maximum value of the vacuum pressure may be determined to be <NUM>×<NUM>-<NUM> Torr.

The lowest value of the vacuum pressure of the vacuum adiabatic body is preferable due to the lower gas thermal conductivity as the vacuum pressure is lower. However, as an exhaust time becomes longer, and the vacuum pressure decreases below a certain level, the improvement effect of the gas heat conduction is insignificant.

Under the above background, it is possible to determine the vacuum pressure when a degree of improvement of the gas thermal conductivity becomes small as the vacuum pressure is gradually lowered by a constant value. The constant value for lowering the vacuum pressure is determined as <NUM>-n, and the width is narrowed as the index increases to a negative value. This is because, as for the exhaust, the index is grown to the negative value, and the exhaust time becomes longer. For example, a simulation with respect to the degree of improvement of the gas thermal conductivity according to the vacuum pressure in order of <NUM>. 1E-<NUM> ⇒ <NUM>. 0E-<NUM> ⇒ <NUM>. 9E-<NUM> ⇒ <NUM>. 8E-<NUM> = <NUM>.

Even when the gas thermal conductivity is the same, the vacuum pressure is lowered when the adiabatic thickness of the vacuum adiabatic body is large. Thus, the adiabatic thickness of the vacuum adiabatic body may be based on <NUM>, which is the thickest. Here, the gas thermal conductivity uses <MAT>. This equation may be applied to all types of gas heat conductivity.

<FIG> is table obtained by simulating gas thermal conductivity while changing a vacuum pressure when the adiabatic thickness is about <NUM>. Referring to <FIG>, the degree of improvement of the gas thermal conductivity is dropped to about <NUM>% or less when the vacuum pressure is <NUM>. 9x10-<NUM> Torr.

On the basis of the above, the minimum value of the vacuum pressure may be determined to be <NUM>×<NUM>-<NUM> Torr.

As a result of the above investigation, the maximum/minimum values of the adiabatic thickness of the vacuum adiabatic body is <NUM> and <NUM>, respectively, and the maximum/minimum values of the vacuum pressure of the vacuum adiabatic body is <NUM>×<NUM>-<NUM> Torr and <NUM>×<NUM>-<NUM> Torr, respectively.

This result may be substituted into Equation <NUM>. The pressure applied to the unit area before this is to be subtracted from the vacuum pressure of the vacuum adiabatic body at an atmospheric pressure. When subtracting <NUM>×<NUM>-<NUM> Torr (<NUM> Pa) and <NUM>×<NUM>-<NUM> Torr (<NUM>×<NUM>-<NUM> Pa) at the atmospheric pressure of <NUM>,<NUM> Pa, <NUM>,<NUM> Pa and <NUM>,<NUM> Pa may be obtained, respectively.

As a result, in Equation <NUM>, the maximum/minimum values of the adiabatic thickness L of the vacuum adiabatic body are <NUM> and <NUM>, respectively, and the maximum/minimum values of the pressure P applied to the unit area may use <NUM>,<NUM> Pa and <NUM>,<NUM> Pa.

If the above value is substituted into Equation <NUM>, the value of Equation <NUM> may be obtained.

In this case, each pitch a of the bars has to be larger than twice the short axis of the elliptical shape of the bar and twice the long axis.

The assignment of the concrete numerical values yielding the result of Equation <NUM> is expressed by Equation <NUM>.

Referring to Equation <NUM>, since the vacuum pressure is lowered when the adiabatic thickness of the adiabatic body is large (<NUM>), the pressure applied to the unit area becomes larger (<NUM>,<NUM>). As a result, it is seen that the results of Equation <NUM> is divided into the time when the adiabatic thickness is large, and the time when the insulation thickness is small.

If the bar has a circular shape, m and n are the same value, and the median value of Equation <NUM> may be changed to Er<NUM>/a<NUM> (where r is a radius of the bar). The cross-section of the bar may preferably be provided in the circular shape for convenience of injection.

According to Equation <NUM>, the cross-sectional area of the bar and the pitch between bars are proportional to each other depending on a predetermined index.

According to the above description, the supporting unit of the vacuum adiabatic body may be applied by using the relationship between the material of the bar and the cross-sectional shape of the bar and the pitch of the bar.

When applying Equation <NUM>, when one element is enlarged, it is possible to positively control through correlation with other elements.

It is of course possible to further enhance the safe use of the supporting unit by using Equation <NUM> and additionally adding the safety factor.

Although Equation (<NUM>) assumes that there is nothing in the vacuum space part, if the porous material is contained in the vacuum space part, it may be sufficiently applied for a basic safety check.

The vacuum adiabatic body proposed in the present disclosure may be preferably applied to refrigerators. However, the application of the vacuum adiabatic body is not limited to the refrigerators, and may be applied in various apparatuses such as cryogenic refrigerating apparatuses, heating apparatuses, and ventilation apparatuses.

Claim 1:
A vacuum adiabatic body comprising:
a first plate member (<NUM>) configured to define at least a portion of a wall for a first space;
a second plate member (<NUM>) configured to define at least a portion of a wall for a second space having a temperature different from that of the first space;
a sealing part (<NUM>) configured to seal the first plate member (<NUM>) and the second plate member (<NUM>) so as to provide a third space (<NUM>) that has a temperature between a temperature of the first space and a temperature of the second space and is a vacuum space;
a supporting unit (<NUM>) configured to maintain the third space (<NUM>);
a heat resistance unit configured to reduce a heat transfer amount between the first plate member (<NUM>) and the second plate member (<NUM>); and
an exhaust port (<NUM>) through which a gas of the third space (<NUM>) is exhausted,
wherein the supporting unit (<NUM>) comprises a plurality of bars (<NUM>) extending between the first plate member (<NUM>) and the second plate member (<NUM>) in a vertical direction;
characterized in that:
when a pitch between the bars (<NUM>) is a, an elastic modulus of a material forming the bar (<NUM>) is E, and a radius of a long axis is n and a radius of a short axis is m when a cross-section of the bar (<NUM>) has an elliptical shape, the following equation: <MAT> is satisfied