Patent Application
20200408352
The present disclosure relates to a vacuum adiabatic body and a refrigerator.
A vacuum adiabatic body may suppress 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 30 cm or more may be provided. However, the internal volume of the refrigerator may therefore be 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, Korean Patent No. 10-0343719 (Cited Document 1) of the present applicant has been disclosed. Reference Document 1 discloses 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 such 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 Korean Patent Publication No. 10-2015-0012712 (Cited Document 2). According to Reference Document 2, 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.S. Patent Publication No. US 2004/0226956 A1 (Cited Document 3). However, it is difficult to obtain a practical level of an adiabatic effect by providing a wall of the refrigerator with sufficient vacuum. It may be difficult to prevent a heat transfer phenomenon at a contact portion between an outer case and an inner case having different temperatures, to maintain a stable vacuum state, and 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 3 is limited to a cryogenic refrigerator, and does not provide a level of technology applicable to general households.
The present applicant has studied the above limitation. As a result, a technique to maintain and insulate inside of a vacuum space by a supporting unit made of a resin material is disclosed in Korean Patent Application No. 10-2015-0109727 (Cited Document 4). Cited Document 4 has proposed a material which is capable of being suitably applied to the supporting unit. In Cited Document 4, the resin material is selected with reference to outgassing, compression strength, thermal conductivity, a thermal strain rate, and a maximum operation temperature. However, for the outgassing of the supporting unit which is made of a resin material in the vacuum adiabatic body, an exhausting process is required at a relatively low temperature for several days. Such an excessively long exhaust time has a limitation of remarkably lowering the production efficiency of the product. To solve this limitation, the present inventors have carried out research activities and came to the present disclosure as a result of the improvement of this limitation.
In the contents of Cited Document 4, the contents relating to the present disclosure are also described in the description of the present disclosure to facilitate understanding.
Embodiments provide a vacuum adiabatic body in which outgassing of a support unit is reduced to reduce an exhaust process time.
In one embodiment, a vacuum adiabatic body may include a supporting unit or support configured to support an internal space of the vacuum adiabatic body, The supporting unit may include at least two bars or posts configured to support a first plate member and a second plate member, and each of the bar may be made of poly phenylene sulfide (PPS).
In another embodiment, a refrigerator may include a main body configured to provide an internal space in which goods are stored and a door provided to open and/or close the main body from an external space. At least one of the door or the main body includes a vacuum adiabatic body. A supporting unit or support configured to support an internal space of the vacuum adiabatic body may be provided, and a bar or post configured to maintain a gap of the vacuum adiabatic body may be made of a poly phenylene sulfide (PPS) containing glass fiber.
In further one embodiment, a vacuum adiabatic body may include a support unit or support configured to maintain a vacuum space. The supporting unit may include at least one bar or post configured to support a gap between a first plate member and a second plate member. The bar may be made of phenylene sulfide (PPS) containing glass fiber.
Thus, the supporting unit may obtain sufficient strength, maintain its shape in an exhaust process, has low outgassing, and obtain sufficient injection characteristics.
According to the embodiments, the internal exhaust process of the vacuum adiabatic body may be shortened to improve productivity of the product.
According to the embodiments, the molding process and the impact resistance of the supporting unit may be improved together with the shortening of the exhaust process.
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.
Referring to
The cavity 9 may be supplied with parts or devices of a refrigeration or a freezing cycle in which cold air is supplied into the cavity 9. For example, the parts may include a compressor 4 to compress a refrigerant, a condenser 5 to condense the compressed refrigerant, an expander 6 to expand the condensed refrigerant, and an evaporator 7 to evaporate the expanded refrigerant to take heat. As a typical structure, a fan may be installed at a position adjacent to the evaporator 7, and a fluid blown from the fan may pass through the evaporator 7 and then be blown into the cavity 9. 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.
Referring to
When the vacuum adiabatic body is applied to a refrigerator or a warming apparatus, the first plate member 10 providing a wall of an inner space of the refrigerator may be referred to as an inner case, and the second plate member 20 providing a wall of an outer space of the refrigerator may be referred to as an outer case.
A machine room 8 may include parts providing a refrigerating or a freezing cycle. The machine room may be placed at a lower rear side of the main body-side vacuum adiabatic body, and an exhaust port 40 to form a vacuum state by exhausting air from the vacuum space part 50 is provided at any one side of the vacuum adiabatic body. In addition, a pipeline 64 passing through the vacuum space part 50 may be further installed so as to install a defrosting water line and electric lines.
The first plate member 10 may define at least one portion of a wall for a first space provided thereto. The second plate member 20 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 or heat conduction between the first and second plate members 10 and 20, heat radiation between the first and second plate members 10 and 20, and gas conduction of the vacuum space part 50.
Hereinafter, a heat resistance unit or sheet provided to reduce adiabatic loss related to the factors of the heat transfer will be provided. 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 60 or 63 that resists conduction of heat transferred along a wall of a third space 50 and may further include a side frame coupled to the conductive resistance sheet. The conductive resistance sheet 60 or 63 and the side frame will be clarified by the following description.
Also, the heat resistance unit may include at least one radiation resistance sheet 32 that is provided in a plate shape within the third space 50 or may include a porous material that resists radiation heat transfer between the second plate member 20 and the first plate member 10 within the third space 50. The radiation resistance sheet 32 and the porous material will be clarified by the following description.
First, referring to
The supporting unit or support 30 may be provided to reduce deformation of the vacuum space part 50. The supporting unit 30 includes a bar 31. The bar 31 may extend in a substantially vertical direction with respect to the plate members 10 and 20 to support a distance between the first plate member 10 and the second plate member 20. A support plate or frame 35 may be additionally provided on at least any one end of the bar 31. The support plate 35 may connect at least two or more bars 31 to each other to extend in a horizontal direction with respect to the first and second plate members 10 and 20. The support plate 35 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 10 or 20 decreases, thereby reducing heat transfer. The bars 31 and the support plate 35 are fixed to each other at at least one portion, to be inserted together between the first and second plate members 10 and 20. The support plate 35 contacts at least one of the first and second plate members 10 and 20, thereby preventing deformation of the first and second plate members 10 and 20. In addition, based on the extending direction of the bars 31, a total sectional area of the support plate 35 is provided to be greater than that of the bars 31, so that heat transferred through the bars 31 may be diffused through the support plate 35.
A material of the supporting unit 30 will be described.
The supporting unit 30 may have a high compressive strength so as to endure the vacuum pressure, a low outgassing rate and a low water absorption rate so as to maintain the vacuum state, a low thermal conductivity so as to reduce the heat conduction between the plate members 10 and 20 and. Also, the supporting unit 30 may have a secure compressive strength at a high temperature so as to endure a high-temperature exhaust process, have an excellent machinability so as to be subjected to molding, and have a low cost for molding. Here, the time required to perform the exhaust process takes about a few days. Hence, the time is reduced, thereby considerably improving fabrication cost and productivity. Therefore, the compressive strength is to be secured at the high temperature because an exhaust speed is increased as a temperature at which the exhaust process is performed becomes higher. The inventor has performed various examinations under the above-described conditions.
First, ceramic or glass has a low outgassing rate and a low water absorption rate, but its machinability is remarkably lowered. Hence, ceramic and glass may not be used as the material of the supporting unit 30. Resin may be considered as the material of the supporting unit 30.
Referring to
The present inventor has found an optimal material by performing various studies on resins expected to be used inside the vacuum space part 50. Hereinafter, results of the performed studies will be described with reference to the accompanying drawings.
Referring to
An initial exhaust performance of LCP is best, but its vacuum maintenance performance is bad. This may be caused by sensitivity of the LCP to temperature. Also, it is expected through characteristics of the graph that, when a final allowable pressure is 5×10−3 Torr, its vacuum performance will be maintained for a time of about 0.5 years. Therefore, the LCP may not be used as the material of the supporting unit 30.
Regarding glass fiber PC (G/F PC), its exhaust speed is fast, but its vacuum maintenance performance is low. It is determined that this will be influenced by an additive. Also, it is expected through the characteristics of the graph that the glass fiber PC will maintain its vacuum performance under the same conditions for a time of about 8.2 years. Therefore, PC (G/F PC) may not be used as the material of the supporting unit 30.
It is expected that, in the case of the low outgassing PC (O/G PC), its vacuum maintenance performance is excellent, and its vacuum performance will be maintained under the same conditions for a time of about 34 years, as compared with the above-described two materials. However, it may be seen that the initial exhaust performance of the low outgassing PC is low, and therefore, the fabrication efficiency of the low outgassing PC is lowered.
It may be seen that, in the case of the PPS, its vacuum maintenance performance is remarkably excellent, and its exhaust performance is also excellent. Based on the vacuum maintenance performance, PPS may be used as the material of the supporting unit 30.
As the analyzed result, it may be re-confirmed that the PPS is excellent as the material of the supporting unit 30.
As the analyzed result, it may be seen that the PPS may be used as the resin used inside the vacuum space part 50. However, the low outgassing PC may be used in terms of fabrication cost.
In the above vacuum adiabatic body production process, the exhaust process is performed at about 90 degrees for about 50 hours. The exhaust process for about 50 hours is practically difficult to apply in the production process of the product. The present inventor continued their research activities to find out how to improve them. As a result, it has been found out that the inside of the vacuum adiabatic body is outgassed by an exhaust process time of about one hour if an exhaust temperature increases to a temperature of about 150 degrees or more.
The inventor has confirmed that when the exhaust process is performed at a temperature higher than about 90° C., the outgassing time of the PPS is shortened, however, when the exhaust process is performed at a high temperature, the supporting unit 30 may be thermally deformed. As an embodiment of the thermal deformation, there is an example in which the bar 31 collapses, or the support plate 35 of the supporting unit 30 is deformed. The modification of the supporting unit 30 is leads to the disposal of all products. Therefore, additional research and development are conducted to find a condition in which the supporting unit 30 is not deformed even when the high-temperature exhaust process is performed. This will be described in more detail.
It is confirmed that when a certain amount of glass fiber is added to PPS which is a material of the supporting unit 30, no thermal deformation occurs in the exhaust process.
Table 1 shows experimental results of thermal deformation at 1×10−4 Torr after selecting PPS as a base material of the supporting unit 30 to manufacture the supporting unit 30 with glass fiber having different contents (%). This content represents a weight of the glass fiber with respect to the total weight of the supporting unit 30.
Referring to Table 1, when 100% PPS is used, it was seen that a structure of the supporting unit 30 is collapsed at a temperature about 130 degrees. When 20% of the glass fiber is contained, the structure of the supporting unit collapsed at a temperature of about 140 degrees. Thus, it was seen that the content of the glass fiber has to be about 30% or more so as to perform the exhaust process at a temperature of about 150 degrees. The reason why strength at a high temperature is improved as the content of the glass fiber increases is assumed because the glass fiber reinforces weakened strength even if the PPS is locally weakened due to deterioration at the high temperature.
As the content of the glass fiber increases, impact strength increases.
Referring to
Referring to the experimental results, the content of the glass fiber having impact strength of about 2 times or more as compared to the pure PPS may be selected within a range of about 20% to about 60%.
The inventor could observe that when the supporting unit 30 is manufactured through injection molding, a shape of the supporting unit 30 does not come out properly as the glass fiber is contained therein. Although a certain level of improvement is expected by increasing an injection pressure applied during the injection, if the injection pressure increases, limitations of leakage and enlargement may occur. When the support plate 35 is provided in a lattice shape to reduce a heat loss, and the bar 31 and the support plate 35 are injected together as a single body, since a transfer distance of an injection liquid is distant, the above limitation may remarkably occur.
If any position of the bar 31 at one point is not manufactured with a predetermined diameter or length during the injection, it may not withstand the vacuum pressure at the corresponding position. This is fatal to the vacuum adiabatic body because it does affect not only the limitation but also other bars 31 in its periphery, leading to subsequent failure. If one bar 31 does not withstand the vacuum pressure, force applied to the adjacent bar becomes stronger.
To solve the above limitation, the inventor has found a range in which the flowability of the injection is not deteriorated according to the content of the glass fiber.
Referring to
Hereinafter, a radiation resistance sheet 32 to reduce heat radiation between the first and second plate members 10 and 20 through the vacuum space part 50 will be described. The first and second plate members 10 and 20 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 0.16, and hence a large amount of radiation heat may be transferred. In addition, the supporting unit 30 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 10 and 20. Hence, the supporting unit 30 does not have great influence on radiation heat. Therefore, the radiation resistance sheet 32 may be provided in a plate shape over a majority of the area of the vacuum space part 50 so as to concentrate on reduction of radiation heat transferred between the first and second plate members 10 and 20. A product having a low emissivity may be used as the material of the radiation resistance sheet 32. In an embodiment, an aluminum foil having an emissivity of 0.02 may be used as the radiation resistance sheet 32. Also, since the transfer of radiation heat may not be sufficiently blocked using one radiation resistance sheet 32, at least two radiation resistance sheets 32 may be provided at a certain distance so as not to contact each other. Also, at least one radiation resistance sheet 32 may be provided in a state in which it contacts the inner surface of the first or second plate member 10 or 20.
Referring back to
In the present embodiment, the vacuum adiabatic body may be manufactured without the radiation resistance sheet 32.
Referring to
In the present embodiment, the vacuum adiabatic body may be manufactured without the supporting unit 30. That is to say, the porous material 33 may perform the function of the radiation resistance sheet 32 and the function of the supporting unit 30 together.
First, a conductive resistance sheet 60 proposed in
The conductive resistance sheet 60 may be provided with sealing or welding parts 61 at which both ends of the conductive resistance sheet 60 are sealed to define at least one portion of the wall for the third space or vacuum space part 50 and maintain the vacuum state. The conductive resistance sheet 60 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 vacuum space part 50. The sealing parts 610 may be provided as welding parts, and the conductive resistance sheet 60 and the plate members 10 and 20 may be fused to each other. In order to cause a fusing action between the conductive resistance sheet 60 and the first and second plate members 10 and 20, the conductive resistance sheet 60 and the first and second plate members 10 and 20 may be made of the same material (e.g., a stainless material). The sealing parts 610 are not limited to the welding parts, and may be provided through a process such as cocking. The conductive resistance sheet 60 may be provided in a curved shape. Thus, a thermal conduction distance of the conductive resistance sheet 60 is provided longer than the linear distance of each plate member 10 and 20, so that the amount of thermal conduction may be further reduced.
A change in temperature occurs along the conductive resistance sheet 60. Therefore, in order to block heat transfer to the exterior of the conductive resistance sheet 60, a shielding part or cover 62 may be provided at the exterior of the conductive resistance sheet 60 such that an adiabatic action occurs. In other words, in the refrigerator 1, the second plate member 20 has a high temperature and the first plate member 10 has a low temperature. In addition, thermal conduction from high temperature to low temperature occurs in the conductive resistance sheet 60, and hence the temperature of the conductive resistance sheet 60 is suddenly changed. Therefore, when the conductive resistance sheet 60 is opened to the exterior thereof, heat transfer through the opened place may seriously occur. In order to reduce heat loss, the shielding part 62 is provided at the exterior of the conductive resistance sheet 60. For example, when the conductive resistance sheet 60 is exposed to any one of the low-temperature space and the high-temperature space, the conductive resistance sheet 60 may not serve as a conductive resistor at the exposed portion.
The shielding part 62 may be provided as a porous material contacting an outer surface of the conductive resistance sheet 60. The shielding part 62 may be provided as an adiabatic structure, e.g., a separate gasket, which is placed at the exterior of the conductive resistance sheet 60. The shielding part 62 may be provided as a portion of the vacuum adiabatic body, which is provided at a position facing a corresponding conductive resistance sheet 60 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 2 and the door 3 are opened, the shielding part 62 may be provided as a porous material or a separate adiabatic structure.
A conductive resistance sheet 60 proposed in
In the door-side vacuum adiabatic body, it is difficult to place the conductive resistance sheet 60 at a front end portion of the vacuum space part 50, i.e., a corner side portion of the vacuum space part 50. This is because, unlike the main body 2, a corner edge portion of the door 3 is exposed to the exterior. In more detail, if the conductive resistance sheet 60 is placed at the front end portion of the vacuum space part 50, the corner edge portion of the door 3 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 60.
A conductive resistance sheet 63 proposed in
A heat transfer path between the first and second plate members 10 and 20 will be described with reference back to
The transfer heat may be changed depending on various depending on various design dimensions. For example, the supporting unit 30 may be changed such that the first and second plate members 10 and 20 may endure a vacuum pressure without being deformed, the vacuum pressure may be changed, the distance between the first and second plate members 10 and 20 may be changed, and the length of the conductive resistance sheet 60 or 63 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 10 and 20. In the embodiment, a 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 19.6 mW/m K.
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 {circle around (3)} may become the smallest. For example, the heat transfer amount by the gas conduction heat {circle around (3)} may be controlled to be equal to or smaller than 4% of the total heat transfer amount. A heat transfer amount by solid conduction heat defined as a sum of the surface conduction heat {circle around (1)} and the supporter conduction heat {circle around (2)} is the largest. For example, the heat transfer amount by the solid conduction heat may reach 75% of the total heat transfer amount. A heat transfer amount by the radiation transfer heat {circle around (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 {circle around (3)} may occupy about 20% 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 {circle around (1)}, the supporter conduction heat {circle around (2)}, the gas conduction heat {circle around (3)}, and the radiation transfer heat {circle around (4)} may have an order of Math Equation 1.
eK
solid conduction heat
>eK
radiation transfer heat
>eK
gas conduction heat [Equation 1]
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/AΔT. Here, Q denotes a calorific value (W) and may be obtained using a calorific value of a heater. A denotes a sectional area (m2) of the vacuum adiabatic body, L denotes a thickness (m) of the vacuum adiabatic body, and ΔT denotes a temperature difference.
For the surface conduction heat, a conductive calorific value may be obtained through a temperature difference (ΔT) between an entrance and an exit of the conductive resistance sheet 60 or 63, a sectional area (A) of the conductive resistance sheet, a length (L) of the conductive resistance sheet 60 or 63, and a thermal conductivity (k) of the conductive resistance sheet 60 or 63 (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 (ΔT) between an entrance and an exit of the supporting unit 30, a sectional area (A) of the supporting unit 30, a length (L) of the supporting unit 30, and a thermal conductivity (k) of the supporting unit 30. Here, the thermal conductivity of the supporting unit 30 is a material property of a material and may be obtained in advance. The sum of the gas conduction heat {circle around (3)}, and the radiation transfer heat {circle around (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 {circle around (3)}, and the radiation transfer heat {circle around (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 50.
When a porous material is provided inside the vacuum space part 50, porous material conduction heat {circle around (5)} may be a sum of the supporter conduction heat {circle around (2)} and the radiation transfer heat {circle around (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 ΔT1 between a geometric center formed by adjacent bars 31 and a point at which each of the bars 31 is located may be preferably provided to be less than 0.5° C. Also, a temperature difference ΔT2 between the geometric center formed by the adjacent bars 31 and an edge portion of the vacuum adiabatic body may be preferably provided to be less than 0.5° C. In the second plate member 20, a temperature difference between an average temperature of the second plate member 20 and a temperature at a point at which a heat transfer path passing through the conductive resistance sheet 60 or 63 meets the second plate member 20 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 60 or 63 meets the second plate member 20 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 60 or 63 meets the second plate member 20 becomes highest.
This means that the amount of heat transferred through other points except the surface conduction heat passing through the conductive resistance sheet 60 or 63 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 60 or 63 may be controlled to be larger than that of the plate members 10 and 20.
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/m2) of a certain level may be preferably used.
Under such conditions, the plate members 10 and 20 and the side frame 70 may be 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 31 is decreased so as to limit the support conduction heat, deformation of the plate members 10 and 20 may occur due to the vacuum pressure, which may bad influence on the external appearance of refrigerator. The radiation resistance sheet 32 may be made of a material that has a low emissivity and may be easily subjected to thin film processing. Also, the radiation resistance sheet 32 is to ensure a strength strong enough not to be deformed by an external impact. The supporting unit 30 is provided with a strength strong enough to support the force by the vacuum pressure and endure an external impact, and is to have machinability. The conductive resistance sheet 60 may be made of a material that has a thin plate shape and may endure the vacuum pressure.
In an embodiment, the plate members 10 and 20, the side frame 70, and the conductive resistance sheet 60 or 63 may be made of stainless materials having the same strength. The radiation resistance sheet 32 may be made of aluminum having a weaker strength that the stainless materials. The supporting unit 30 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 60 or 63 may be made of a material having a high or predetermined strength, but the stiffness of the material may be low so as to increase heat resistance and minimize radiation heat as the conductive resistance sheet 60 or 63 is uniformly spread without any roughness when the vacuum pressure is applied. The radiation resistance sheet 32 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 32 may generate conduction heat due to drooping caused by the self-load of the radiation resistance sheet 32. Therefore, a stiffness of a certain level is required. The supporting unit 30 may require a stiffness strong enough to endure a compressive stress from the plate members 10 and 20 and an external impact.
In an embodiment, the plate members 10 and 20 and the side frame 70 may have the highest stiffness so as to prevent deformation caused by the vacuum pressure. The supporting unit 30, particularly, the bar 31 may have the second highest stiffness. The radiation resistance sheet 32 may have a stiffness that is lower than that of the supporting unit 30 but higher than that of the conductive resistance sheet 60 or 63. Lastly, the conductive resistance sheet 60 or 63 may be made of a material that is easily deformed by the vacuum pressure and has the lowest stiffness.
Even when the porous material 33 is filled in the vacuum space part 50, the conductive resistance sheet 60 or 63 may have the lowest stiffness, and the plate members 10 and 20 and the side frame 70 may have the highest stiffness.
Hereinafter, a vacuum pressure preferably determined depending on an internal state of the vacuum adiabatic body. As already described above, a vacuum pressure is to be maintained inside the vacuum adiabatic body so as to reduce heat transfer. At this time, it will be easily expected that the vacuum pressure is preferably maintained as low as possible so as to reduce the heat transfer.
The vacuum space part 50 may resist heat transfer by only the supporting unit 30. Here, a porous material 33 may be filled with the supporting unit 30 inside the vacuum space part 50 to resist the heat transfer. The heat transfer to the porous material 33 may be resisted without applying the supporting unit 30.
The case where only the supporting unit is applied will be described.
Referring to
Referring to
In the embodiment, a point at which the vacuum pressure is not substantially decreased any more even though the gas is exhausted by operating the vacuum pump is set to the lowest limit of the vacuum pressure used in the vacuum adiabatic body, thereby setting the minimum internal pressure of the vacuum space part 50 to 1.8×10−6 Torr.
Referring to
It was seen that, since the size of the gap is small at a point corresponding to a typical effective heat transfer coefficient of 0.0196 W/mK, which is provided to a adiabatic material formed by foaming polyurethane, the vacuum pressure is 2.65×10−1 Torr even when the size of the gap is 2.76 mm. Meanwhile, it was seen that the point at which reduction in adiabatic effect caused by gas conduction heat is saturated even though the vacuum pressure is decreased is a point at which the vacuum pressure is approximately 4.5×10−3 Torr. The vacuum pressure of 4.5×10−3 Torr may be defined as the point at which the reduction in adiabatic effect caused by gas conduction heat is saturated. Also, when the effective heat transfer coefficient is 0.1 W/mK, the vacuum pressure is 1.2×10−2 Torr.
When the vacuum space part 50 is not provided with the supporting unit 30 but provided with the porous material 33, the size of the gap ranges from a few micrometers to a few hundreds of micrometers. In this case, the amount of radiation heat transfer is small due to the porous material 33 even when the vacuum pressure is relatively high, i.e., when the vacuum degree is low. Therefore, an appropriate vacuum pump is used to adjust the vacuum pressure. The vacuum pressure appropriate to the corresponding vacuum pump is approximately 2.0×10−4 Torr. Also, the vacuum pressure at the point at which the reduction in adiabatic effect caused by gas conduction heat is saturated is approximately 4.7×10−2 Torr. Also, the pressure where the reduction in adiabatic effect caused by gas conduction heat reaches the typical effective heat transfer coefficient of 0.0196 W/mK is 730 Torr.
When the supporting unit 30 and the porous material 33 are provided together in the vacuum space part 50, a vacuum pressure may be created and used, which may be a middle pressure between the vacuum pressure when only the supporting unit 30 is used and the vacuum pressure when only the porous material 33 is used.
In the description of the present disclosure, a part for performing the same action in each embodiment of the vacuum adiabatic body may be applied to another embodiment by properly changing the shape or dimension of foregoing another embodiment. Accordingly, still another embodiment may be easily proposed. For example, in the detailed description, in the case of a vacuum adiabatic body suitable as a door-side vacuum adiabatic body, the vacuum adiabatic body may be applied as a main body-side vacuum adiabatic body by properly changing the shape and configuration of a vacuum adiabatic body.
The vacuum adiabatic body proposed in the present disclosure may be 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.
According to the present disclosure, the vacuum adiabatic body may be industrially applied to various adiabatic apparatuses. The adiabatic effect may be enhanced, so that it is possible to improve energy use efficiency and to increase the effective volume of an apparatus.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2018-0074263 | Jun 2018 | KR | national |
This application is a U.S. National Stage Application under 35 U.S.C. § 371 of PCT Application No. PCT/KR2019/007760, filed Jun. 26, 2019, which claims priority to Korean Patent Application No. 10-2018-0074263, filed Jun. 27, 2018, whose entire disclosures are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2019/007760 | 6/26/2019 | WO | 00 |
