Patent Publication Number: US-11029075-B2

Title: Door for home appliance and home appliance having the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Phase Application under 35 U.S.C. § 371 of International Application PCT/KR2016/007682 filed on Jul. 14, 2016, which claims the benefit of Korean Application No. 10-2015-0099662, filed on Jul. 14, 2015, and Korean Application No. 10-2016-0001137, filed on Jan. 5, 2016, the entire contents of which are hereby incorporated by reference in their entireties. 
     TECHNICAL FIELD 
     The present disclosure relates to a door for home appliance and home appliance having the same. Particularly, the present disclosure relates to a refrigerator door and a refrigerator. 
     BACKGROUND ART 
     In general, refrigerators are apparatuses for keeping stored objects in a frozen or refrigerated state by maintaining a storage region defined therein at a predetermined temperature by means of a refrigeration cycle realized via a compressor, a condenser, an expansion valve, and an evaporator. Accordingly, a refrigerator includes storage regions, for example, a freezing compartment and a refrigerating compartment. Refrigerators may be classified into various kinds of refrigerators depending on the positions of a freezing compartment and a refrigerating compartment. For example, refrigerators may be classified into several kinds of refrigerators, including a top-mounting type refrigerator, in which a freezing compartment is located above a refrigerating compartment, a bottom-freezer type refrigerator, in which a freezing compartment is located below a refrigerating compartment, a side-by-side type refrigerator, in which a freezing compartment and a refrigerating compartment are isolated from each other by means of a partition so as to be located on left and right sides, and the like. Furthermore, refrigerators may be classified into a household refrigerator, which is used in the home, and a commercial refrigerator, which is used in eating places, convenience stores or the like. 
     A freezing compartment and a refrigerating compartment are defined in a cabinet forming the appearance of the refrigerator, and are selectively opened or closed by a freezing compartment door and a refrigerating compartment door, respectively. Some refrigerators also include an interactive touch-input panel provided on a front surface of a door of the refrigerator. Such touch-input panels allow a user to control various functions of the refrigerator by applying a touch-input to the front surface of the refrigerator door. Some refrigerators are provided with a door made of glass so as to enable the inside of the refrigerator to be visible from the outside without opening the door. However, since a household refrigerator is provided with a freezing compartment door and a refrigerating compartment door that are opaque, the inside of the freezing compartment or the refrigerating compartment is typically made visible only by opening the freezing compartment door or the refrigerating compartment door. 
     Some household refrigerators enable the inside thereof to be visible without opening the refrigerator door, thus reducing the loss of cold air caused by frequent opening and closing of the door. In this type of refrigerator, the door is commonly constructed so as to include a transparent window enabling the inside of the refrigerator to be visible from the outside, and a transparent window support part for supporting the transparent window. However, since the transparent window of the door is generally made of glass, there is a disadvantage in that condensation forms on the glass due to the limited thermal insulation capacity of the glass. 
     Some refrigerators have been designed to overcome this disadvantage. Examples of such refrigerators are described in Korean Unexamined Patent Publication No. 10-2013-0113273 and Chinese Unexamined Patent Publication No. 104061740A. Korean Unexamined Patent Publication No. 10-2013-0113273 is directed to a commercial showcase refrigerator, in which a frame having no thermal insulation value supports a glass window. According to this patent, a heating wire is utilized to heat the glass window to prevent condensation on the glass window, but the heating wire is designed to heat the entire glass window, resulting in a disadvantage of excessive power consumption. 
     Furthermore, Chinese Unexamined Patent Publication No. 104061740A is directed to a refrigerator in which a door includes three glass sheets and a frame support part for supporting the three glass sheets. The middle glass sheet of the triple glass sheet is provided on the entire area thereof with an electric heating film, such as an indium-tin oxide conductive film, which serves to heat the entire area of the middle glass sheet to prevent condensation. However, since the heating film also heats the entire area of the middle glass sheet, there is also a disadvantage of excessive electric energy being consumed and the structure being complicated. 
     As described above, the related arts are commonly configured to heat the entire panel using a heating wire or heating film to compensate for the limited thermal insulation capacity of the panel or glass window itself. Since these related arts heat the entire glass window, excessive electric energy is consumed, and the structure is complicated. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure solves the above problems by providing a refrigerator door and a refrigerator that reduce power consumption and more efficiently prevents condensation on a panel using a simplified structure. 
     Technical Solution 
     In accordance with an aspect of the present invention, there are provided a door for a home appliance including a panel assembly including a front panel defining at least a portion of a front appearance of the door, a rear panel disposed behind the front panel, and a spacer disposed between a peripheral portion of the front panel and a peripheral portion of the rear panel so as to maintain a spacing between the front panel and the rear panel, a frame assembly for supporting the panel assembly, the frame assembly including a side frame disposed along a side surface of the door, the side frame contacting outside air, and a heat transfer structure for transferring heat of outside air from the side frame to an interior region defined between the front panel and the rear panel and between the spacer and a side end of the door, and a home appliance including the same. The home appliance may be a refrigerator. 
     The panel assembly may include a rear frame connected to the rear panel, and the side frame may include a rear frame connector connected to the rear frame and a panel connector connected to the front panel. 
     The rear frame may include a first end connected to the rear panel and a second end connected to the side panel, the second end being connected to the rear frame inside the rear frame connector. 
     The rear frame and the side frame may be made of different materials, and the side frame may have a higher coefficient of heat transfer than the rear frame. 
     Specifically, the rear frame may be made of resin material, and the side frame may be made of metal. The resin material may be ABS material having a high thermal insulation value, and the metal may be aluminum having a high heat transfer property. 
     The heat transfer structure may include a heat transfer portion, the heat transfer portion being connected at one end thereof to the side frame and extending toward a side surface of the interior region. The heat of the side frame may be efficiently transferred to the interior region via the heat transfer portion. Specifically, heat may be transferred to a side surface of the interior region. 
     The remaining end of the heat transfer portion may be connected to the side surface of the interior region and may extend along the side surface of the interior region. 
     Cold air behind the panel assembly may be transferred to an area in front of the panel assembly through a peripheral portion of the panel assembly. Specifically, cold air may be transferred through the spacer. Accordingly, the interior region of the panel assembly outside the spacer may be supplied with heat rather than cold air. 
     To this end, outside heat may be supplied from the side frame via the heat transfer structure. 
     The side frame and the heat transfer structure may be integrally formed. As a result, more efficient heat transfer may be implemented. 
     The front panel may include a peripheral front panel portion having a larger width than the rear panel, and the interior region may include a rear surface of the peripheral front panel portion. 
     The heat transfer structure may be disposed at the peripheral front panel portion. 
     The door for a home appliance may further include a heating element disposed at the interior region of the panel assembly. The heating element may supply heat to the interior region, either in conjunction with or independently of the heat transfer structure. 
     The heating element may be disposed at the portion at which the front panel is coupled to the frame assembly. 
     The heating element may be constituted by a heating wire, and may be attached to the rear surface of the front panel using metal tape. 
     A thermal insulating space may be defined between the rear frame, the side frame and the interior region of the panel assembly, and may be provided therein with a thermal insulator. 
     The rear frame may be connected to the rear panel so as to cover the spacer, and a thermal insulator may be provided behind the spacer. As a result, it may be possible to primarily reduce transfer of cold air via the spacer by virtue of the rear frame and the thermal insulator. 
     The heat transfer structure may include a heat transfer portion, which penetrates the thermal insulating space so as to transfer heat from the side frame to the interior region of the panel assembly. In this case, the thermal insulator envelops a conduit for heat transfer formed by the heat transfer structure. As a result, it may be possible to achieve efficient heat transfer via the heat transfer structure. 
     The side frame may include an indented portion that is indented toward the inside of the door, the indented portion defining a handle of the door. 
     In accordance with an aspect of the present invention, there are provided a refrigerator door including a panel assembly including a front panel defining at least a portion of a front appearance of the door, a rear panel disposed behind the front panel, and a spacer disposed between a peripheral portion of the front panel and a peripheral portion of the rear panel so as to maintain a spacing between the front panel and the rear panel, a frame assembly for supporting the panel assembly, the frame assembly including a side frame disposed along a side surface of the door, the side frame contacting outside air, a heat transfer structure or a heat bridge for transferring heat of outside air from the side frame to an interior region defined between the front panel and the rear panel and between the spacer and a side end of the door, and a heating element disposed at the interior region of the panel assembly so as to provide heat to the interior region, and a refrigerator including the same. Obviously, the door may be applied not only to a refrigerator but also to a home appliance having a storage compartment. 
     The panel assembly may be a transparent panel, and the panel assembly may include a see-through region defined by a region inside the spacer and a non-see-through region outside the spacer. 
     The heat transfer structure and the heating element may be disposed at the non-see-through region. As a result, it may be possible to provide the refrigerator door including the see-through region with an improved aesthetic appearance by virtue of the heat transfer structure and the heating element. 
     In accordance with an aspect of the present invention, there is provided a door for a home appliance including a panel assembly including a front panel defining at least a portion of a front appearance of the door, a frame assembly for supporting the panel assembly, the frame assembly including a side frame disposed along a side surface of the door, and a heat transfer structure disposed behind the front panel so as to transfer heat to a region between the side frame and the front panel. 
     The front panel may include a peripheral front panel portion, to which the side frame is connected, and the heat transfer structure may be provided at the peripheral front panel portion. 
     The panel assembly may include a rear panel disposed behind the door, the panel assembly may include a rear frame connected to the rear panel, and the side frame may include a rear frame connector connected to the rear frame and a panel connector connected to the front panel. 
     The panel assembly may include an interior region defined between the front panel and the rear panel, the front panel may have a larger width than the interior region of the panel assembly, and the portion of the front panel that extends outward beyond the width of the interior region of the panel assembly may include the peripheral front panel portion. 
     The panel assembly may include one or more thermal insulation panels provided at the interior region of the panel assembly, the front panel may have a larger width than the maximum width of the one or more thermal insulation panels, and the portion of the front panel that extends beyond the maximum width of the one or more thermal insulation panels may include the peripheral front panel portion. 
     The side frame may be provided at the peripheral front panel portion. 
     The panel assembly may include an inner side surface defining a side surface of the interior region of the panel assembly, and the heat transfer structure may include a heat transfer portion, which is connected at one end thereof to the side frame of the panel assembly and extends toward the inner side surface. 
     The other end of the heat transfer portion may be connected to the inner side surface and may extend along the inner side surface. 
     The other end of the heat transfer portion may be connected to the peripheral front panel portion of the front panel and may extend along the peripheral front panel portion. 
     The front panel, the side frame and the inner side surface defining the side surface of the interior region of the panel assembly may define a thermal insulation region therebetween, and the heat transfer portion may extend from the side frame into the thermal insulation region. 
     The heat transfer structure may include a heating element for generating heat. Specifically, the heat transfer structure may perform transfer and generation of heat. 
     The heat transfer structure may be connected to the heating element. 
     The side frame may be connected to the peripheral front panel portion, and may extend along at least a portion of the length of the peripheral front panel portion. 
     The heating element may be provided at a predetermined position on the inner side surface of the panel assembly. 
     The heating element may be provided at the front panel of the panel assembly. 
     The heating element may be provided at a portion where the front panel is connected to the frame assembly. 
     The side frame and the heat transfer structure may be integrally formed. 
     The side frame may include an indented portion, and the indented portion may be indented toward the inside of the door. 
     The rear frame may be made of thermoplastic resin having a high heat transfer property, preferably ABS. The side frame and the heat transfer structure may be made of metal, preferably aluminum. 
     The front panel may have the same size as the door. 
     The front panel may be a touch-input panel. 
     The front panel may be a transparent glass panel. 
     The home appliance may be a refrigerator, the door may be a sub-door of a refrigerator, the refrigerator may include a cabinet and a main door for opening and closing the cabinet, and the sub-door may be a door of a home appliance, which is hingedly coupled to the main door. 
     In accordance with an aspect of the present invention, there is provided a refrigerator door including a panel assembly including a plurality of panels of thermally insulated glass and spacers disposed between the glass panels, a front glass panel of the plurality of glass panels having a peripheral portion larger than other glass panels; a side frame disposed behind the peripheral portion of the front glass panel, the side frame being connected at one end thereof to the peripheral portion of the front glass panel and at the other end thereof extending rearward from the peripheral portion of the front glass panel; a rear frame being connected at one end thereof to the side frame and at the other end thereof to the rear glass panel of the panel assembly; a thermal insulator disposed in the space defined between the rear frame, the side frame and the peripheral portion of the front glass panel; and a heat transfer structure (heat transfer frame) being connected at one end thereof to the side frame and at the other end thereof extending toward the edge of the panel assembly. The side frame and the heat transfer structure may be made of metal. 
     The heat transfer structure may be in close contact with the inner surface of the peripheral portion of the front glass panel. 
     In accordance with another aspect of the present invention, the present invention may further include another heat transfer structure, which is connected at one end thereof to the side frame and at the other end thereof extends toward the edge of the panel assembly through the thermal insulator. The other end of the heat transfer structure may extend along the edge of the panel assembly. Furthermore, the other end of the heat transfer structure may extend along the inner surface of the front glass panel. 
     The one end of the heat transfer structure may be connected to the side frame and may pass through the thermal insulator. The other end of the heat transfer structure may extend along the edge of the panel assembly or the inner surface of the peripheral portion of the front glass panel. The side frame and the heat transfer structure may be made of aluminum. 
     The side frame and the heat transfer structure may be integrally formed. The peripheral portion of the front glass panel may have the same size as the size of the entire door. The side frame may include an indented portion that is indented toward the inside of the door. 
     In accordance with still another aspect of the present invention, the other end of the rear frame may extend so as to cover the spacer. Preferably, the other end of the rear frame may extend to the position at which the spacer is disposed. The rear frame may be made of thermoplastic resin having a high thermal insulation value. Preferably, the rear frame may be made of ABS. The rear frame and the side frame may at least partially overlap each other. 
     In accordance with a further aspect of the present invention, the panel assembly may further be provided at a predetermined position on the edge thereof with a heating element. The front glass panel of the panel assembly may be the same size as the door. 
     Advantageous Effects 
     Advantageous effects obtained by the door for a home appliance and the home appliance including the same according to the present invention will now be described. 
     First, according to an embodiment of the present invention, there is an advantage of being able to simply and efficiently prevent condensation on the connecting region between the panel assembly and the frame assembly. 
     Second, according to another embodiment of the present invention, it is possible to prevent condensation by heating the connecting region between the panel assembly and the support of the panel assembly without having to heat the entire panel assembly. Accordingly, there is an advantage of being able to drastically reduce power consumption, compared to the case where the entire panel assembly is heated. Specifically, there is an advantage of being able to reduce power consumption to about ⅛ of the power consumption of heating the entire panel assembly  10 . As a result, there are advantages of being able to simplify the structure of the heating element and to improve the freedom in design of the door. 
     Third, according to a further embodiment of the present invention, there is an advantage of being able to prevent condensation by modifying the structure of the support of the panel assembly. Specifically, there are advantages of being able to improve the aesthetic appearance of the door and of being able to prevent condensation on the connecting region between the panel assembly and the support of the panel assembly by making the front glass panel of the panel assembly have substantially the same size as the door. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a perspective view of an example of a refrigerator according to an implementation of the present disclosure; 
         FIG. 2  is a diagram illustrating a cross-sectional view taken along line I-I in  FIG. 1 ; 
         FIG. 3  is a diagram illustrating an exploded perspective view of an example of a sub-door shown in  FIG. 1 ; 
         FIGS. 4A to 4E  are diagrams illustrating cross-sectional views of various implementations of the frame assembly shown in  FIG. 2 ; 
         FIG. 5  is a diagram illustrating a perspective view of an example of a refrigerator according to another implementation of the present disclosure; 
         FIG. 6  is a diagram illustrating a perspective of an example of a sub-door as shown in  FIG. 5 ; and 
         FIG. 7  is a diagram illustrating a perspective view of an example of a refrigerator according to a further implementation of the present disclosure. 
     
    
    
     DESCRIPTION OF IMPLEMENTATIONS AND BEST MODEL 
     In the following description, a bottom freezer type refrigerator will be set forth as an example for convenience of explanation. However, implementations are not limited to a bottom freezer type refrigerator, and may also include a top-mounting type refrigerator, a side-by-side type refrigerator, or other suitable types of refrigerators. Furthermore, in the following description, a refrigerator including a refrigeration compartment door constituted by two doors, a main door and a sub door, will be set forth as an example for convenience of explanation. However, implementations are not limited thereto, and may also include a refrigerator including a refrigeration compartment door consisting of a single door or any suitable number of doors. As such, the present disclosure may be applied to any suitable type of refrigerator. 
     Furthermore, although the present disclosure describes refrigerators, the techniques described herein are not limited to refrigerators and may generally be applied to other types of home appliances that include a door. For example, implementations described herein may be applied to an appliance having a door that is equipped with a transparent material or equipped with a touch-input panel. In general, implementations of the present disclosure may be applied to various types of home appliances to reduce condensation in a panel of a door of the home appliance in a more energy-efficient and less complex manner. The examples that follow are described with reference to a refrigerator as an example of such an appliance. 
     An example of an overall structure of a refrigerator according to a preferred implementation of the present disclosure will be described with reference to  FIG. 1 . However, implementations are not limited to the exact structure of  FIG. 1 , and other refrigerator structures may be used with a different number of doors, a different installation mode of the doors, and the like 
     Referring to the example in  FIG. 1 , a refrigerator includes a cabinet  1  that is provided with a refrigerating compartment at an upper part of the cabinet land with a freezing compartment at a lower part of the cabinet  1 . The refrigerating compartment and the freezing compartment are opened and closed by doors. For example, the upper refrigerating compartment is opened and closed by door  3 , door  5 , and door  7 , the latter of which may be a sub-door. The lower freezing compartment is opened and closed by door  9  and door  11 . 
     In the example of  FIG. 1 , although the right side of the upper refrigerating compartment is illustrated as being opened and closed by both a main door  5  and a sub-door  7 , implementations are not limited thereto, and the right refrigerating compartment door may be provided with a single door. Furthermore, although the refrigerating compartment and the freezing compartment are illustrated as being provided with side-by-side doors, implementations are not limited thereto, and each compartment may be provided with a single door or any suitable number and configuration of doors. According to the implementation of  FIG. 1 , the right refrigerating compartment door includes the main door  5 , hingedly coupled to the cabinet  1 , and the sub-door  7 , hingedly coupled to the main door  5 . The main door  5  is provided with an additional subsidiary storage space, such as a basket, that allows a user to access objects stored in the subsidiary storage space by opening only the sub-door  7 , without necessarily opening the main door  5 . 
     The sub-door  7  according to the implementation of  FIG. 1  includes a panel assembly  10  and a frame assembly  20 . The panel assembly  10  may define a front surface of the sub-door  7 . The frame assembly  20  may include one or more frames that support the panel assembly  10 . 
     In some implementations, the panel assembly  10  may include a transparent panel through which the inside of the refrigerator is visible from the outside thereof. In some implementations, the panel assembly  10  may include an interactive touch-input panel that enables a user to control one or more operations of the refrigerator from the outside. The frame assembly  20  structurally supports the panel assembly  10 . The refrigerator door, for example, the sub-door  7 , including the panel assembly  10  may have a thermal insulation value to prevent leakage of cold air to the outside as well as intrusion of external heat to the inside of the refrigerator. Accordingly, the panel assembly  10  and the frame assembly  20 , which constitute the sub-door  7 , may have a thermal insulation value. 
     However, there may be challenges in maintaining the thermal insulation of the panel assembly  10  and the frame assembly  20 . In some implementations, the panel assembly  10  may be predominantly made of glass to provide transparent see-through capabilities. In some implementations, the panel assembly  10  may be configured with an interactive touch-input panel that enables a user&#39;s touch-input to control operations of the refrigerator. In either implementation, the panel assembly  10  may be difficult to thermally insulate. To address such challenges, the panel assembly  10  may be provided with insulation therein to provide thermal insulation. For example, the panel assembly  10  may include one or more internal thermal insulation panels and/or may be provided with other insulating material within the panel assembly  10  to improve thermal insulation. 
     While thermal insulation of the panel assembly  10  may help maintain a cold temperature inside the refrigerator, there may be additional challenges caused by the resulting differences in temperature and/or humidity between the inside and outside of the refrigerator. For example, condensation may form on the panel assembly  10  due to differences in temperature and/or humidity between the inside and outside of the refrigerator. Such condensation may reduce the overall thermal insulation capabilities of the panel assembly  10  and the frame assembly  20 . To address problems caused by condensation, in some refrigerators, the entire panel assembly  10  may be heated to reduce the difference in temperature and/or humidity between the inside and outside of the panel assembly  10 , thus reducing condensation on the panel assembly  10  while maintaining a cold temperature inside the refrigerator. 
     However, techniques such as those described above may not be able to prevent condensation on the panel assembly  10  in some situations. For example, in some scenarios, condensation may still occur on the panel assembly  10 , in particular along the edges of the panel assembly  10  where the panel assembly  10  connects with the frame assembly  20 . For example, as shown in  FIG. 1 , condensation may occur on a connecting region  10   a  at which the panel assembly  10  connects with the frame assembly  20 . Such condensation may present challenges in maintaining a desired thermal insulation capability. Condensation on the connecting region  10   a  may be exacerbated in certain situations, such as in situations of greater ambient temperatures and higher humidity, for example ambient temperatures greater than 25° C. and relative humidity greater than 80%. 
     Condensation on the peripheral connecting region  10   a  may be exacerbated more than on other regions of the panel assembly  10 , for example an interior region of the panel assembly  10 , due to differences in physical properties between the panel assembly  10  and the frame assembly  20 . Such differences in physical properties may cause differences in thermal insulation values between the panel assembly  10  and the frame assembly  20 , thus posing greater challenges to reducing condensation. As a result, the thermal insulation value may be deteriorated at the connecting region  10   a , more than in other portions of the panel assembly  10  or the frame assembly  20 . 
     Accordingly, to address such challenges and reduce condensation, implementations described herein prevent condensation on the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . In some implementations, the refrigerator may be configured to reduce condensation only on the connecting region  10   a  rather than on the entirety of the panel assembly  10  itself, which may help reduce energy consumption to more efficiently reduce condensation. In addition to improving thermal insulation, such techniques may also improve the usability of refrigerators in which the panel assembly  10  is transparent by allowing users to clearly view the inside of the refrigerator even under adverse conditions, which may be especially useful for household refrigerators. 
     As described above, condensation may be exacerbated at the connecting region  10   a  between the panel assembly  10  and the frame assembly  20  due to a form of heat bridge that is formed between two different physical materials. The difference in thermal insulation values between the panel assembly  10  and the frame assembly  20  may result in the connecting region  10   a  having a relatively low thermal insulation value. As a result, cold air in the refrigerator may tend to be concentrated on this connecting region  10   a , thereby causing condensation. 
     To address these challenges, implementations described herein provide efficient heating at the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . In some implementations, the door  7  may provide heating of the connecting region  10   a . In some implementations, the heating may be provided in addition or as an alternative to changing the structure of the frame assembly  20 . As such, implementations described herein may help reduce electric energy consumption as compared to techniques that heat the entirety of the panel assembly  10 . Furthermore, implementations described herein may help simplify the structure of the refrigerator door and to improve the freedom in design and the aesthetic appearance of the door. 
       FIGS. 2 and 3  are diagrams illustrating an example of a refrigerator according to some implementations. 
     Although  FIGS. 2 and 3  are described with reference to a sub-door  7 , implementations are not limited to a sub-door and techniques described herein may be applied to any suitable door of a home appliance. Therefore, the subsequent description will simply refer to a door  7  for convenience. Furthermore, implementations of the panel assembly  10  of the sub-door are not limited to the panel  10  in  FIGS. 2 and 3 , and in general the panel assembly  10  may be any suitable panel with a heating structure as described herein. 
     The panel assembly  10  of door  7  may have a predetermined thermal insulation value, and may have an approximately rectangular shape, although implementations are not limited thereto. The frame assembly  20  is connected to the peripheral portion of, and thereby supports, the panel assembly  10 , and may have a predetermined thermal insulation value. A heating element  30  is disposed near the connecting region  10   a  at which the panel assembly  10  and the frame assembly  20  are coupled to each other. The heating element  30  is disposed at a location that provides substantial heat to the connecting region  10   a . For example, the heating element  30  may be disposed at a predetermined location on the connecting region  10   a . As another example, the heating element  30  may be spaced apart from the connecting region  10   a  by a predetermined distance that enables substantial heating of the connecting region  10   a.    
     Examples of individual components of the door  7  are described below. 
     An example of the panel assembly  10  is first described. In the example of  FIG. 2 , the panel assembly  10  may include a front panel  16 . The front panel  16  defines a front appearance of the door  7 . The front panel  16  may be made of a transparent material to enable a user to see through the door  7 , or the front panel  16  may be an interactive touch-input panel to enable a user to apply a touch-input and control operations of the home appliance. As such, the front panel  16  may be a glass panel in the case of a transparent panel assembly  10 , or may be a touch-input-enabled panel in the case of an interactive touch-input panel assembly  10 . 
     The internal space defined within the panel assembly  10  may include thermal insulation behind the front panel  16 . In the example of  FIG. 2 , the panel assembly  10  includes a middle panel  14  and a rear panel  12 , which may improve the thermal insulation of the panel assembly  10 . However, implementations are not limited the example of  FIG. 2 , and the panel assembly  10  may include any suitable thermal insulation behind the front panel  16 , such as any suitable number of thermal insulation panels or other suitable thermal insulation behind the front panel  16 . As such, in some implementations, the panel assembly  10  may include the front panel  16  and appropriate thermal insulation behind the front panel  16 . In the case of a transparent panel assembly  10  of  FIG. 2 , the front panel  16 , the middle panel  14 , and the rear panel  12  are glass panels, and the spaces between the panels may be insulated with a suitable gas. In the case of an interactive touch-input panel assembly  10 , the interior space defined within the panel assembly  10  may additionally include one or more sensors, such as touch sensors or electrostatic sensors, enabling touch-input detection on the front panel  16 . 
     In some implementations, the front panel  16  may be larger than the remaining portions of the panel assembly  10 . For example, in  FIG. 2 , the front panel  16  is larger than the middle panel  14  and the rear panel  12 . In some implementations, the front panel  16  may have almost the same size as the door  7  and may cover the frame assembly  20  when viewed from a front of the refrigerator. As described above, since the front panel  16  of the panel assembly  10  defines the appearance of the door  7 , the front panel  16  having the same size as the door  7  provides an improved aesthetic appearance as if the entire door were made of a single panel. To this end, the front panel  16  has a peripheral front panel portion  16   a . The peripheral front panel portion  16   a  is a portion that expands in four directions beyond the edges of the rear panel  12  or the middle panel  14 . 
     In some implementations, spacers  18  are interposed between the panels  12 ,  14  and  16  at the peripheral portions thereof. The panels  12 ,  14  and  16  may be coupled to each other using sealant  19  or other suitable coupling. The panels  12 ,  14  and  16  may be made of insulated material having a predetermined thermal insulation value. In implementations of a transparent panel assembly  10 , two or more panels of thermally insulated glass may be used. In such implementations, the insulated glass panels  12 ,  14  and  16  may be made of low-emissivity glass configured to prevent heat loss due to radiation. The low-emissivity glass may be hard or soft low-emissivity glass, and in some implementations soft low-emissivity glass may be used to obtain high performance low emissivity. 
     In implementations of a transparent panel assembly  10 , tempered glass is used that helps prevent breakage of the panels. The front panel  16  may be made of a glass that has controllable light transmissibility, for example color-changeable glass, such that the inside of the refrigerator is selectively visible from the outside. For example, when the lighting inside the refrigerator is turned off the front panel  16  may become opaque such that the inside of the refrigerator is not visible from the outside; and when the lighting inside the refrigerator is turned on, the front panel  16  may become transparent such that the inside of the refrigerator is visible from the outside. The color-changeable property of the front panel  16  may have any suitable implementation, for example a color glass panel or a glass panel, which is coated with an opaque material through TI deposition, may also be used. The front panel  16  preferably has a high thermal insulation value. 
     The spacer  18  provided between the panels in the panel assembly  10  may be constituted by, for example, aluminum (Al), a thermal protection spacer (TPS) and the like, and a thermal protection space is preferably used in order to improve the thermal insulation value at the portion at which the spacer  18  is installed. The spacer  18  preferably include therein a hygroscopic material. 
     The space  13   a  between the rear panel  12  and the middle panel  14  and the space  13   b  between the middle panel  14  and the front panel  16  may be vacuumized or may be filled with an insulating solid, liquid, or gas. In some implementations, the space  13   a  is filled with air or argon (Ar) gas. Since argon gas has a higher thermal insulation value than air and is an inert gas capable of resisting transformation through chemical action, it is preferable to use argon gas rather than air. 
     Next, the frame assembly  20  will be described in detail. 
     The frame assembly  20  preferably has a predetermined thermal insulation value. To this end, the frame assembly  20  may be constituted by a portion having sufficient rigidity to support the panel assembly  10  and another portion for substantially fulfilling the thermal insulation function, without being limited thereto. The frame assembly  20  defines a thermal insulation space which accommodates a thermal insulator  60  having a predetermined thermal insulation value. The frame assembly  20  is preferably coupled to the panel assembly  10 . 
     The frame assembly  20  is preferably constituted by a plurality of components for the convenience of assembly, without being limited thereto. The overall construction of an example of the frame assembly  20  is first described with reference to  FIG. 3 . 
     In the example of  FIG. 3 , the frame assembly  20  includes a rear frame  200  disposed at the rear portion of the door, a side frame  300  and a side frame  400  disposed at both lateral side ends of the door, an upper frame  500  disposed at an upper end of the door, and a lower frame  600  disposed at a lower end of the door. In some implementations, such as those in which the panel assembly  10  is transparent, the rear frame  200 , the side frames  300 ,  400 , the upper frame  500 , and the lower frame  600  define a thermal insulation space along the sides of the panel assembly  10 . In such implementations of a transparent see-through panel assembly  10 , the thermal insulation space may accommodate a thermal insulator  60 , such as an insulating foam or other material or gas. The panel assembly  10  is coupled to the opening defined by the inner edges of the rear frame  200 , the side frames  300 ,  400 , the upper frame  500 , and the lower frame  600 . In some implementations, such as those in which the panel assembly  10  is transparent, a thermal insulator  60 , such as an insulating foam or other material, may be formed in the space defined by the frames and the peripheral portion of the panel assembly  10  (see  FIG. 2 ). Alternatively, in some implementations, such as where the panel assembly  10  is an interactive touch-input panel, the thermal insulator  60  may not be included, and instead thermal insulation may be generally provided inside the panel assembly  10 , for example between the panels  12  and  14 . 
     The rear frame  200  is disposed at the inner side of the door so as to serve to support the entire door. The frames  300 ,  400 ,  500  and  600  are disposed at lateral, upper, and lower sides of the panel assembly  10  so as to partially define the appearance of the door. The frames  300 ,  400 ,  500  and  600  may serve to prevent warpage of the door, and, in conjunction with the thermal insulator  60  in some implementations, may prevent condensation on the door. 
     The frames  300 ,  400 ,  500 , and  600  may define a portion of the appearance of the door, and in some implementations may be decorative trims that are visible from the exterior of the door. 
     The rear frame  200 , the side frames  300  and  400 , and the relationship therebetween are now described with reference to  FIG. 2 . The relationship between the panel assembly  10 , the rear frame  200 , and the upper and lower frames  500  and  600  may have a similar relationship. The basic structures of the rear frame  200  and the side frames  300  and  400  are first described for convenience of explanation, and an example of the specific structures of the rear frame  200  and the side frames  300  and  400  are described in more detail in an implementation to be described later in which the structure of the panel assembly  10  is modified. 
     A cross-section of an example of the rear frame  200  is illustrated in  FIG. 2 . In this example, the rear frame  200  includes a first end  220  coupled to the panel assembly  10 , a second end  230  coupled to the side frames  300  and  400 , and a connecting portion  210  that connects the first end  220  to the second end  230 . The first end  220  of the rear frame  200  is the portion that is connected to the rear panel  12  of the panel assembly  10 , and the second end  230  is the portion that is connected to the side frames. The connecting portion  210 , connecting the first end  220  to the second end  230 , is substantially parallel to the front face of the cabinet of the refrigerator. The rear frame  200  is provided at an area thereof with a gasket  40 . The inner surface of the gasket  40  is substantially parallel to the connecting portion  210  connecting the two ends of the rear frame  200 . The first end  220  of the rear frame  200  is connected to, and thereby supports, the rear panel  12 . The first end  220  of the rear frame  200  is configured to surround the spacer  18 , which may have a low thermal insulation value. 
     The side frame  400  may include a rear frame connector  420  connected to the rear frame  200 , and a panel connector  410  extending from the rear frame connector  420  substantially to the peripheral portion of the panel assembly  10 , that is, to a position close to the peripheral front panel portion  16   a . The panel connector  410  of the side frame  400  is connected to the end of the peripheral front panel portion  16   a  of the front panel  16 . 
     The side frame  300  may also include a rear frame connector  320  connected to the rear frame  200 , and a panel connector  310  extending from the rear frame connector  320  to the peripheral portion of the panel assembly  10 , that is, to a position close to the peripheral front panel portion  16   a . In some implementations, the side frame  300  includes an indented portion  330  that is indented toward the inside of the door between the rear frame connector  320  and the panel connector  310 . The indented portion  330  may serve as a handle of the door. To define a space configured to receive a user&#39;s hand, the end of the peripheral front panel portion  16   a  that is connected to the side frame  300  is disposed at a position further inward than the rear frame connector  320  of the side frame  300 . For example, the peripheral front panel portion  16   a  of the side frame  300  of the front panel  16  has a smaller width than the side frame  300 . The panel connector  310  of the side frame  300  extends from a position that is spaced inward apart from the end of the peripheral front panel portion  16   a  of the front panel  16  to a position at the end of the peripheral front panel portion  16   a , and is in close contact with the inner surface of the peripheral front panel portion  16   a.    
     As described above, for implementations in which the panel assembly  10  is a transparent see-through panel, the rear frame  200  and the frames  300 ,  400 ,  500  and  600  may define a predetermined space therebetween, and the rear frame  200 , the frames  300 ,  400 ,  500  and  600 , and the peripheral portion of the panel assembly  10  may together define a space that is substantially enclosed. The space may be filled with the thermal insulator  60 , for example, polyurethane foam (PU foam) so as to provide the frame assembly  20  with a predetermined thermal insulation value. For implementations in which the panel assembly  10  is not configured to be transparent, such as an interactive touch-input panel, the space including the thermal insulator  60  may not be necessary due to thermal insulation that fills the interior space of the panel assembly  10 . 
     Next, the heating element  30  is described in detail. 
     As described above, under certain conditions, condensation may be exacerbated at the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 , more than at other portions of the panel assembly  10 . Accordingly, implementations described herein are configured to prevent condensation on this connecting region  10   a.    
     In some implementations, the heating element  30  is disposed near the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 , for example, either at the connecting region  10   a  or near the connecting region  10   a . As a particular example shown in  FIG. 2 , the heating element  30  may be installed at a region, labeled region A in  FIG. 2 , along a side surface of the interior region of the panel assembly  10 , between the thermal insulator  60  and the panel assembly  10 . It is further preferable for the heating element  30  to be positioned close to the front surface of the door  7  so as to reduce condensation at the front surface of the panel assembly  10 . As such, the heating element  30  may be provided at a position at which to heat the front surface of the door  7 . To this end, the heating element  30  is preferably installed on a rear surface of the front panel  16  of the panel assembly  10 , illustrated in  FIG. 2  as region E. 
     In some implementations, the heating element  30  may be provided at a region where the frame assembly  20  connects with the panel assembly  10 . For example, as illustrated in  FIG. 2 , the heating element may be provided at region B either on the inner surface or the outer surface of the first end  220  and panel connector  310  of the frame assembly  20 . As such, the heating element may be provided at a portion at which the front and rear ends of the frame assembly  20  are mainly connected to the panel assembly  10 . Therefore, the heating element  30  may be provided at any one or more of regions B, A, and E in  FIG. 2 , at which the panel assembly  10  is coupled to the frame assembly  20 . 
     As described above, because the spacer  18  is configured to have a low thermal insulation value, the heating element  30  may be installed at a region C at which the spacer  18  is installed. For example, the heating element  30  may be installed in the spacer  18 , may be installed in contact with the spacer  18 , or may be installed near the spacer  18 . However, in the case where the heating element  30  is installed in the spacer  18 , the hygroscopic material in the spacer  18  may leak out, thereby causing condensation inside the panel assembly  10 . Furthermore, because the spacer  18  is positioned inside the panel assembly  10 , an additional mounting structure and additional wiring may be required to provide the heating element  30  in the spacer  18  or in contact with the spacer  18 . Accordingly, there may be advantages in providing the heating element  30  along the peripheral portion of the panel assembly  10 . If the heating element  30  is installed along a peripheral portion of the panel assembly  10 , the heating element  30  may be provided close to the spacer  18  while simplifying the installation structure. 
     Although the above examples have described the heating element  30  provided close to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 , implementations are not limited thereto. The heating element  30  may be installed at any position on the panel assembly  10  that enables the heating element  30  to transfer heat to the connecting region  10   a  and thus prevent condensation. This may be achieved even if the heating element  30  is slightly spaced apart from the connecting region  10   a . For example, the heating element  30  may be provided at the peripheral portion of the front panel  16  of the panel assembly  10 , that is, in at least one region of the inner and outer surfaces D of the peripheral front panel portion  16   a.    
     In some implementations, the heating element  30  may be configured to heat only the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . As such, in some implementations, the heating element  30  may be implemented as a heating wire, which may consume relatively little power. Accordingly, the heating element  30  configured to have a wire shape may be disposed along the peripheral portion of the panel assembly  10 . The heating element  30  may be implemented as a heating wire and have a shape corresponding to the shape of the peripheral portion of the panel assembly  10  (see  FIG. 3 ). By configuring the heating element  30  in such a manner to heat only the connecting portion  10   a , rather than the entire panel assembly  10 , power consumption may be reduced while still achieving reduced condensation. For example, in some implementations the heating element  30  configured according to this structure may consume only about 7 W of power, as compared to about 60 W or more that may be consumed by heating the entire panel assembly  10 . As a result, power consumption may be reduced by a significant fraction, for example, to ⅛ of the power consumption of heating the entire panel assembly  10 . 
     In some implementations, the side frames  300  and  400  may be disposed behind the peripheral front panel portion  16   a  of the front panel  16  so as to be invisible to a user when viewed from in front of the door. Accordingly, the front panel  16  of the panel assembly  10  may be the same size as the door and may have a flat surface, rather than a curved surface. In addition, the panel connector  310  of the side frame  300  may be connected to a rear surface of the peripheral front panel portion  16   a  of the front panel  16  and thus be hidden from view. Furthermore, the heating element  30  may be installed near the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . 
     In addition, an opaque region  50  may be provided on an inner surface of the peripheral front panel portion  16   a  of the front panel  16 , and the heating element  30  may be positioned on an inner surface of the opaque region  50 . As such, this may prevent the heating element  30  from being visible from the outside of the door. The opaque region  50  may be implemented, for example, by an opaque material that is printed on the inner surface of the front panel  16 . 
     The heating element  30  may be attached to the front panel  16  by any suitable heat-conductive attachment, for example by using aluminum (Al) adhesive tape. Heat from the heating element  30  can be efficiently transmitted to the peripheral region of the front panel  16  via the heat-conducting attachment. As another advantage, for implementations in which the panel assembly  10  is a transparent see-through panel, attaching the heating element  30  using aluminum (Al) adhesive tape may enable the heating element  30  to be temporarily held in place during the process of manufacturing the door, thus preventing the heating element  30  from being pushed into the panel assembly  10  upon insertion of the thermal insulator  60 . 
     An example in which condensation is prevented in the refrigerator door according to the implementation of the present disclosure is now described with reference to  FIG. 2 . 
     In this implementation, the panel assembly  10  and the frame assembly  20  have a predetermined thermal insulation value whereby condensation does not occur on the sub-door  7  under general ambient conditions. However, under certain conditions, such as when the environment surrounding refrigerator becomes adverse, for example, during rainy seasons or in a tropical climate, the cold air in the refrigerator may leak to the outside of the door. Accordingly, the heating element  30  provided near the connecting region  10   a  results in heating of the cold air that leaks to the outside of the door. Consequently, even in scenarios of high relative humidity of air around the front panel  16 , condensation does not occur at the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . Furthermore, heat from the heating element  30  is transmitted via the heat-conductive attachment, such as aluminum adhesive tape, that attaches the heating element  30  to the front panel  16 , as well as via the side frames  300  and  400 , thereby preventing condensation even on the side frames  300  and  400 . To this end, the side frames  300  and  400  are preferably made of metal having high heat conductivity. 
     Next, an example of a refrigerator door according to another implementation of the present disclosure is described with reference to  FIG. 2 . In the previous implementation, condensation on the door is prevented by providing the heating element  30 . In this implementation, condensation on the door is prevented by modifying the structure of the frame assembly  20 , either in addition to or as an alternative to providing the heating element  30 . 
     An example of this modified frame assembly  20  is described with reference to the rear frame  200 . 
     In the implementation shown in  FIG. 2 , the first end  220  of the rear frame  200  that is connected to the panel assembly  10  extends so as to cover the peripheral portion of the panel assembly  10 . For example, the first end  220  may extend to cover the portion of the panel assembly  10  at which the spacer  18  is installed. By modifying the first end  220  of the rear frame  200  to cover the spacer  18 , this may further help prevent cold air in the refrigerator from leaking to the outside through the spacer  18 , even in scenarios where the spacer  18  has a relatively low thermal insulation value. In addition, if the space defined between the first end  220  of the rear frame  200  and the spacer  18  is filled with a thermal insulator, this may further improve the thermal insulation value. Although the first end  220  of the rear frame  200  may further extend inward towards the middle of the panel assembly  10  beyond the spacer  18 , this may have a disadvantage of reducing the size of the portion of the panel assembly  10  that is exposed to the outside, thereby reducing the area through which a user views the inside of the refrigerator, in the case of a transparent panel assembly  10 , or reducing the interactive touch-input area, in the case of a touch-input panel assembly  10 . Therefore, in order to achieve a tradeoff between maximizing the size of the panel assembly  10  while minimizing heat transfer to the outside, the first end  220  of the rear frame  200  preferably extends to such an extent as to substantially cover the spacer  18 . For example, the edge of the first end  220  of the rear frame  200  that is connected to the panel may coincide with the edge of the spacer  18  when viewed from the front. 
     The second end  230  of the rear frame  200  that is connected to the side frame  300  or  400  may be connected to the inner side of the side frame  300  or  400 . The portion of the rear frame  200  that is connected to the side frame  400  is preferably disposed at the inner side of the rear frame connector  420  of the side frame  400  so as to overlap it, and is preferably almost the same length as the rear frame connector  420 . Similarly, the portion of the rear frame  200  that is connected to the side frame  300  is also preferably connected to the rear frame connector  320  of the side frame  300  so as to overlap it. However, in some implementations, the portion of the rear frame  200  may also be configured to overlap the remaining portion of the rear frame connector  320  to exclude the indented portion  330 . 
     For implementations that provide the thermal insulator  60  along the edges of the door, such as implementations in which the panel assembly  10  is a transparent window, the thermal insulator  60  is covered by the rear frame  200  having a high thermal insulation value, thereby more reliably preventing cold air that passes through the thermal insulator  60  from leaking out through the rear frame  200 . 
     As the rear frame  200  is positioned inside the refrigerator and is the component that the cold air in the refrigerator first contacts, the rear frame  200  is preferably made of a material having a low coefficient of heat transfer. In addition, the rear frame  200  is preferably made of thermoplastic resin, and more preferably ABS, to facilitate moldability in manufacturing. 
     In the previous implementation, condensation is prevented by modifying the structure of the rear frame  200 . Next, an example of a modified structure of the side frames  300  and  400  is described. The subsequent examples may also be applied to modify the upper frame  500  and the lower frame  600 . 
     In this implementation, condensation is prevented by modifying the structure of the side frames  300  and  400 . The side frames  300  and  400  preferably serve to increase the mechanical strength of the door and may further be configured to prevent condensation. Specifically, if the side frames  300  and  400  are exposed to air outside the refrigerator, the side frames  300  and  400  may be configured to absorb the heat attributable to the ambient temperature outside the refrigerator and exchange heat between the absorbed heat and the front surface of the door  7 , which is cooled by the cold air in the refrigerator, thereby preventing condensation. 
     As such, the side frames  300  and  400  preferably absorb the heat attributable to the ambient temperature outside the refrigerator, and transfer the absorbed heat to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . As a result, heat exchange occurs at the connecting region  10   a , which is cooled by the cold air in the refrigerator, thereby preventing condensation. Accordingly, the side frames  300  and  400  are preferably made of a heat-conducting material, for example a metal such as aluminum (Al), which has a predetermined mechanical strength and is capable of easily radiating heat energy. 
     As in the rear frame  200 , the ends of the side frames  300  and  400  cover the spacer  18 , which may have a relatively low thermal insulation value. However, this may have a disadvantage of increasing the thickness of the frame assembly  20  (in the anteroposterior direction of the door). In addition, as in the above implementation of the modified rear frame  200 , extending the frame assembly  20  towards the interior region the panel assembly  10  (in the direction of the center of the door from the right and left ends and the upper and lower ends of the door) to cover the spacer  18  may reduce the size of the portion of the panel assembly  10  that is exposed to the outside. Accordingly, it is preferable for the front panel  16  of the panel assembly  10  to have the peripheral front panel portion  16   a , and for the side frames  300  and  400  to be disposed behind the peripheral front panel portion  16   a.    
     Furthermore, the refrigerator door preferably includes heat transfer structures  315  and  415  configured to efficiently transfer heat from the ambient temperature that is absorbed by the side frames  300  and  400  to the portion of the front panel  16  having a relatively low thermal insulation value. The heat transfer structures  315  and  415  are also disposed behind the peripheral front panel portion  16   a  of the front panel  16  of the panel assembly  10 . In some implementations, one end of each of the heat transfer structures  315  and  415  are connected to the corresponding one of the side frames  300  and  400 , and the other end of the heat transfer structures  315  and  415  extend to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . 
     An example of the side frame  400  is now described. The side frame  400  preferably includes the heat transfer structure  415 , which extends from a predetermined position thereof to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . The heat transfer structure  415  preferably extends from the side frame  400  to a position close to the spacer  18 . Furthermore, the heat transfer structure  415  more preferably extends so as to contact the inner surface of the peripheral front panel portion  16   a  of the front panel  16 . The heat, which has been transferred to the side frame  400  from the ambient-temperature air outside of the refrigerator, is transferred to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 , thereby preventing condensation on the connecting region  10   a.    
     Similarly, the side frame  300  preferably includes the heat transfer structure  315 , which extends from a predetermined position on the side frame  300  to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . The heat transfer structure  315  preferably extends from the panel connector  310  of the side frame  300  to the connecting region  10   a , and more preferably to a position close to the spacer  18 . Furthermore, the heat transfer structure  315  more preferably extends so as to contact the inner surface of the peripheral front panel portion  16   a  of the front panel  16 . The heat, which has been transmitted to the side frame  300  from the ambient-temperature air outside the refrigerator, is transferred to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20  through the heat transfer structure  315 , thereby preventing condensation on the connecting region  10   a.    
     In some implementations, the heating element  30  may additionally be provided on the front panel  16 , disposed close to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20 . The heating element  30  may provide further heating of the front panel  16 , in addition to the heat that is transferred by the heating structures  315  and  415  from the side frames  300  and  400 . In such implementations, the heating element  30  may also contact the heat transfer structure  315  or  415 . 
     Although the above examples disclose implementation including a modification in the structure of the rear frame  200  and implementations including a modification of the frames  300 ,  400 ,  500  and  600 , the present disclosure is not limited thereto. For example, some implementations may include modifications of the structure of the rear frame  200  in addition to modifications of the structures of the frames  300 ,  400 ,  500  and  600 . 
     An example of an operation of the implementation is now described. For convenience of explanation, an example is described that includes modifications in the structure of the rear frame  200  in addition to modifications of the structures of the frames  300 ,  400 ,  500  and  600 . 
     The transfer of cold air inside the refrigerator to the outside of the refrigerator is primarily blocked by the rear frame  200 . In addition, for implementations in which the panel assembly  10  is transparent, cold air may further be blocked by the thermal insulator  60 . In some implementations, the rear frame  200  is made of thermoplastic resin having a high thermal insulation value, thus more efficiently blocking the transfer of cold air to the outside of the refrigerator. In such implementations, because the second end  230  of the rear frame  200  that is connected to the side frame  300  or  400  is disposed at the inner side of the side frame  300  or  400 , this may further prevent cold air that has passed through the thermal insulator  60  from being transferred to the outside. 
     A portion of the cold air in the refrigerator may be transferred to the front surface of the door  7  without being blocked by the rear frame  200  or the thermal insulator  60 . However, since the side frames  300  and  400  are made of metal having high heat conductivity, the side frames  300  and  400  may absorb heat of external air having an ambient temperature outside the refrigerator, and may transfer the absorbed heat to the inside of the side frames  300  and  400 . Consequently, the heat transferred from the side frames  300  and  400  heats the front surface of the sub door  7 , which is cooled by the cold air transmitted to the front surface without being blocked by the rear frame  200  or by the thermal insulator  60 , thereby preventing condensation on the front surface. Furthermore, the ambient-temperature heat transferred to the side frames  300  and  400  is more efficiently transferred to the connecting region  10   a  between the panel assembly  10  and the frame assembly  20  through means of the heat transfer structures  315  and  415  provided at the side frames  300  and  400 . The resulting heat transferred to the front panel  16  more efficiently prevents condensation. Furthermore, implementations in which the heating element  30  is additionally included may further provide more efficient prevention of condensation. 
     The heat transfer structures  315  and  415  according to the present disclosure may be implemented in various manners to transfer heat from the side frames  300  and  400  of the door to the peripheral front panel portion  16   a  at the periphery of the front panel  16 . As such, the heat transfer structures  315  and  415  may transfer heat to a portion of the panel assembly  10  that connects with the frame assembly  20 , namely the peripheral connecting region  10   a  shown in  FIGS. 1 and 2 , where the panel assembly  10  is most susceptible to condensation. Furthermore, by being confined to this peripheral front panel portion  16   a , the heat transfer structures  315  and  415  may remain outside of an interior region of the panel assembly  10 , where the panel assembly  10  may be provided with transparent glass panels in the case of a transparent panel assembly  10  or where the panel assembly  10  may be provided with sensors and electronic components in the case of an interactive touch-input panel assembly  10 . Various implementations of the heat transfer structures  315  and  415  portion are described with reference to  FIGS. 4A to 4E . 
       FIGS. 4A to 4E  illustrate different examples of the heat transfer structure  315  that transfers heat between the side frame  300  and the front panel  16 . Similar structures may be used for the heat transfer structure  415  between the side frame  400  and the front panel  16 . However, implementations are not limited to these examples, and may include other types of heat transfer structures that transfer heat between the side frames  300 ,  400  and the front panel  16 , specifically the peripheral front panel portion  16   a  of the front panel  16 . 
     In the first example illustrated in  FIG. 4A , the heat transfer structure includes a heat transfer portion  315   a  configured to penetrate the thermal insulator  60 . The heat transfer portion  315   a  includes a penetrating portion  3151  and a contact portion  3153 . The penetrating portion  3151  may extend from the side frame  300  and penetrate the space defined between the side frame  300  and the side surface of an interior region of the panel assembly  10 . In the case of a transparent panel assembly  10 , this space may be filled with the thermal insulator  60 . The contact portion  3153  extends from the penetrating portion  3151  and contacts along the side surface of the interior region of the panel assembly  10 . In this case, the contact portion  3153  preferably has a predetermined length so as to extend along the side surface of the interior region of the panel assembly  10 . In addition, the panel connector  310  of the side frame  300  may be connected to the peripheral front panel portion  16   a  of the front panel  16  at a position spaced inward apart from the end of the peripheral front panel portion  16   a , thus providing additional transfer of heat from the side frame  300  to the peripheral front panel portion  16   a  of the front panel  16 . 
     In the second example illustrated in  FIG. 4B , the heat transfer structure includes a heat transfer portion  315   b . The heat transfer portion  315   b  includes a penetrating portion  3155  and a contact portion  3157 . The penetrating portion  3155  penetrates the space defined between the side frame  300  and the side surface of an interior region of the panel assembly  10 . The contact portion  3157  extends from the penetrating portion  3155  and contacts along the inner surface of the peripheral front panel portion  16   a  of the front panel  16 . In this case, the contact portion  3157  preferably has a predetermined length so as to extend along the inner surface of the peripheral front panel portion  16   a  of the front panel  16 . In addition, the panel connector  310  of the side frame  300  may be connected to the peripheral front panel portion  16   a  of the front panel  16  at a position spaced inward apart from the end of the peripheral front panel portion  16   a , thus providing additional transfer of heat from the side frame  300  to the peripheral front panel portion  16   a  of the front panel  16 . 
     In the third example illustrated in  FIG. 4C , the heat transfer structure  315  includes a heat transfer portion  315   c  extending from the panel connector  310  of the side frame  300  to a location near the side surface of the interior region of the panel assembly  10 . In particular, the panel connector  310  of the side frame  300  is connected to the front panel  16  and is disposed at a location spaced inward apart from the outer edge of the peripheral front panel portion  16   a  of the front panel  16 . The heat transfer portion  315   c  may thus extend from the panel connector  310  to a location near the side surface of the panel assembly  10 . In this case, the panel connector  310  provides a conduit for heat transfer between the side frame  300  and the heat transfer structure, which in turn transfers heat to the peripheral front panel portion  16   a  of the front panel  16 . 
     As illustrated the fourth example  FIG. 4D  and  FIG. 4E , the heat transfer structure may include one or more heat transfer portions that extend along both the side of the panel assembly  10  and that also extend along the front panel  16 . Specifically,  FIG. 4D  illustrates a heat transfer structure including two heat transfer portions  315   d  and  315   e , wherein the heat transfer portion  315   d  is connected to and extends along the side surface of the interior region of the panel assembly  10 , and the heat transfer portion  315   e  is connected to and extends along the front panel  16 . Another example is illustrated in  FIG. 4E , in which the heat transfer structure includes heat transfer portions  315   f  and  315   g , wherein heat transfer portion  315   f  is connected to and extends along the side surface of the interior region of the panel assembly  10 , and heat transfer portion  315   g  is connected to and extends along the peripheral front panel portion  16   a  of the front panel  16 . In these examples, the panel connector  310  also transfers heat between the side frame  300  to the peripheral front panel portion  16   a  of the front panel  16 . 
     In some implementations, the heat transfer structure  315  may constitute a different material than the side frame  300 , and may be connected to the side frame  300 , for example via the panel connecter  310 . Alternatively, in some implementations, the heat transfer structure  315  may be an extension of, and constituting the same material as, the side frame  300  and the panel connector  310 . In addition to the heat transfer structure  315  shown in  FIGS. 4A to 4E , the panel assembly  10  may be additionally provided with a heating element, such as heating element  30  shown in  FIG. 2 , that provides additional heating of the peripheral front panel portion  16   a  of the front panel  16 . 
     The present disclosure is not limited to the above-described implementations, and may be applied to various types of doors that include panels. For example, although the above examples have been described for the case in which the main door  5  is the same size as the sub-door  7 , the present disclosure is not limited thereto. In some implementations, the sub-door may be smaller in size than the main door, so as to fit within the main door when the sub-door is closed. An example of this sub-door configuration is illustrated in  FIG. 5 , in which sub-door  7   a  fits within the main door  5 . As such, the above implementations of heat transfer structures may also be applied to the case in which the sub-door  7   a  has a smaller size than the main door  5 . 
     Furthermore, although the above examples have been described with reference the structure in which the front panel  16  of the panel assembly  10  covers the entire front surface of the sub-door  7 , the present disclosure is not limited thereto. For example, as illustrated in  FIGS. 6 and 7 , implementations may also include a sub-door  7   b  having a panel assembly  10   a  in which a front panel  16   a  of the panel assembly  10   a  does not cover the entire surface of the sub-door  7   b . As shown in  FIG. 7 , the front panel  16   a  of the panel assembly  10   a  may be surrounded by a separate structure, for example the side frames  300   a  and  200   a , that are visible from the front of the refrigerator. The door  7   b  includes a frame assembly  20   a  that supports the panel assembly  10   a , and a heating element  30  disposed at the periphery of the panel assembly  10   a  on the connecting region between the panel assembly  10   a  and the frame assembly  20   a . The frame assembly  20   a  includes a first frame  200   a  and a second frame  300   a , and heat transfer structures may be implemented that transfer heat from the side frames  200   a  and  300   a  to the front panel  16   a  in an analogous manner to the structures of  FIGS. 4A to 4E . 
     The present disclosure is not limited to the above-described implementations, and those skilled in the art will appreciate that various modifications are possible, without departing from the scope and spirit of the disclosure. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               5 ,  7 : door 
               10 : panel assembly 
               20 : frame assembly 
               30 : heating element