CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2015-0106667, filed on Jul. 28, 2015 and entitled “CABINET FOR ELECTRIC DEVICE HAVING COOLING STRUCTURE”, which is hereby incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    Technical Field 
         [0003]    The present disclosure relates to a cabinet for electric devices and, more particularly, to a cabinet for electric devices which is capable of regulating flow of air employed as a cooling medium to uniformly cool the interior of the cabinet. 
         [0004]    Description of the Related Art 
         [0005]    A cabinet for electric devices contains multiple devices generating heat. The cabinet has a structure that forcibly cools the devices using air. 
         [0006]      FIG. 1  is a view illustrating configuration of a conventional cabinet for electric devices based on forced cooling. 
         [0007]    As shown in  FIG. 1 , a cabinet  10  for electric devices includes device accommodation spaces  14  forming multiple layers for accommodating electric devices  12 , and a ventilation duct  16  communicating with the device accommodation spaces  14  in the respective layers. 
         [0008]    The front of each device accommodation space  14  is provided with an introduction portion for introducing external air into the device accommodation space  14 , and a heat dissipation fan  18  for discharging hot air from the ventilation duct  16  is provided to an upper portion of the ventilation duct  16 . 
         [0009]    The cabinet  10  for electric devices cools contained devices by introducing external air thereinto. The pressure in the ventilation duct  16  is lowered by operation of the heat dissipation fan  18 . When the pressure in the ventilation duct  16  is lowered, air in the respective device accommodation spaces is drawn into the ventilation duct  16  having a lowered pressure. As air in the respective device accommodation spaces is drawn into the ventilation duct  16 , the pressure of the respective device accommodation spaces is lowered. Thereby, external air is introduced into the respective device accommodation spaces  14  again through the introduction portions to cool the devices. 
         [0010]    In the ventilation duct  16 , the pressure of air varies with the distance from the heat dissipation fan  18 . More specifically, a higher negative pressure is generated at an upper portion close to the dissipation fan  18  than at a lower portion far from the heat dissipation fan  18 . 
         [0011]    In other words, as the distance between a device accommodation space and the heat dissipation fan  18  increases, the flow rate and flow velocity of air introduced into device accommodation space decrease and thus the degree of cooling is lowered. Accordingly, the cabinet  10  cannot implement uniform cooling. 
         [0012]    Conventionally, in the case where the heat dissipation fan is installed at an upper portion of the cabinet, the capacity of the heat dissipation fan  18  is increased in order to increase the degree of cooling of the device accommodation spaces positioned below the heat dissipation fan. In this case, upper device accommodation spaces are excessively cooled, and a high specification is required for the heat dissipation fan  18  in order to increase the capacity of the heat dissipation fan  18 . This results in unnecessary increase of product costs and noise. 
       SUMMARY 
       [0013]    It is an aspect of some embodiments of the present disclosure to provide a cabinet for electric devices which is capable of individually adjusting the flow rate and flow velocity of air in each device accommodation space to effectively and forcibly cool the electric devices using introduced external air. 
         [0014]    In accordance with one aspect of some embodiments of the present disclosure, a cabinet for electric devices includes a plurality of device accommodation spaces defining a plurality of layers for accommodating the electric devices, and a plurality of connection ducts provided to a ventilation side of the device accommodation spaces, wherein each of the connection ducts includes an introduction port connected to a corresponding one of the device accommodation spaces and a discharge port, wherein a flow rate and flow velocity of air passing through each of the connection ducts is adjusted by differentiating flow resistances in the connection ducts provided to the respective layers from each other by differing areas of the discharge ports from each other according to the layers. 
         [0015]    Preferably, the cabinet for the includes a ventilation duct for discharging heat generated from the device accommodation spaces, and a heat dissipation fan for discharging hot air from the ventilation duct, wherein the discharge ports of the connection ducts are connected to the ventilation duct. 
         [0016]    Preferably, the areas of the discharge ports of the connection ducts are adjustable. 
         [0017]    The discharge port of each of the connection ducts may be formed by a pair of hinge-coupled adjustment segments, each of the adjustment segments including a square bracket-shaped cross section. 
         [0018]    In accordance with another aspect of some embodiments of the preservation, a cabinet for electric devices includes a plurality of device accommodation spaces defining a plurality of layers for accommodating the electric devices, and a plurality of connection ducts provided to a ventilation side of the device accommodation spaces, wherein each of the connection ducts includes a damper for adjusting a flow resistance therein, wherein a flow rate and flow velocity of air passing through each of the connection ducts is adjusted by differentiating the flow resistances caused by the dampers from each other according to the layers. 
         [0019]    Preferably, an opening rate is adjustable by adjusting an angle of each of the dampers. 
         [0020]    According to embodiments of the present disclosure, a cabinet for electric devices includes a structure for cooling electric devices accommodated in the device accommodation spaces using external air introduced into the cabinet. As flows of air in the device accommodation spaces of respective layers are individually adjustable, the interior of the cabinet may be uniformly cooled. 
         [0021]    According to embodiments of the present disclosure, a cabinet for electric devices can adjust the degree of cooling of each layer using connection ducts. Accordingly, the cooling power of the heat dissipation fan may be uniformly or variably transferred to the respective layers. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a view illustrating configuration of a conventional cabinet for electric devices based on forced cooling, according to the prior art. 
           [0023]      FIG. 2  is a view illustrating configuration of a cabinet for electric devices according to a first embodiment of the present disclosure. 
           [0024]      FIG. 3  is a cross-sectional view illustrating connection ducts provided to the cabinet according to the first embodiment of the present disclosure. 
           [0025]      FIG. 4  is a view illustrating configuration of a cabinet for electric devices according to a second embodiment of the present disclosure. 
           [0026]      FIG. 5  is a cross-sectional view illustrating connection ducts provided to the cabinet according to the second embodiment of the present disclosure. 
           [0027]      FIG. 6  is a view illustrating configuration of a cabinet for electric devices according to a third embodiment of the present disclosure. 
           [0028]      FIG. 7  is a cross-sectional view illustrating connection ducts provided to the cabinet according to the third embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Terms or phrases used in this disclosure and appended claims should not be construed as having only meaning known to those skilled in the art or defined in dictionaries, and should be interpreted as including a meaning that is consistent with the spirit of the present disclosure in a sense that the inventor can properly define the terms to describe the present disclosure in the best mode. Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood that the present disclosure is not limited to the following embodiments, and that some embodiments are provided for illustrative purposes only. The scope of the disclosure should be defined only by the accompanying claims and equivalents thereof. 
         [0030]      FIG. 2  is a view illustrating configuration of a cabinet for electric devices according to a first embodiment of the present disclosure, and  FIG. 3  is a cross-sectional view illustrating connection ducts provided to the cabinet according to the first embodiment of the present disclosure. 
         [0031]    Referring to  FIG. 2 , the cabinet  100  for electric devices according to the first embodiment includes device accommodation spaces  120  of multiple layers for accommodating electric devices  12 , a ventilation duct  160  for discharging heat generated from the device accommodation spaces  120 , a heat dissipation fan  180  for discharging hot air from the ventilation duct  160 , and connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  for connecting the device accommodation spaces  120  in the respective layers to the ventilation duct  160 . 
         [0032]    By adjusting the flow resistances in the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  provided to the respective layers, the flow rate and flow velocity of cooling air passing through each of the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  may be adjusted. A flow rate and flow velocity of air passing through each of the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  may be adjusted by differentiating between the flow resistances of each of the connection ducts based on the areas of the discharge ports  144 . 
         [0033]    As described above, the pressure in the ventilation duct  160  varies with the distance from the heat dissipation fan  180 . Some embodiments of the present disclosure is intended to eliminate the difference in the degree of cooling resulting from the difference in pressure among positions, using the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6 . 
         [0034]    Each of the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  employed in some embodiments of the present disclosure includes an introduction port  142  connected to the corresponding one of the device accommodation spaces  120  and a discharge port  144  connected to the ventilation duct  160  such that air can flow from the device accommodation spaces  120  to the ventilation duct  160  only through the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6 . 
         [0035]    In this structure, the flow rates and flow velocities of air passing through the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  may be adjusted by changing the flow resistances in the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6 . Thereby, the degree of cooling of each device accommodation space  120  may be individually adjusted. 
         [0036]    In the first embodiment, various kinds of connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  are used to adjust the flow rate and flow velocity of air in each layer. 
         [0037]    As shown in the figures, each of the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  is provided with the introduction port  142  and discharge port  144 . The instruction ports  142  are connected to the device accommodation spaces  120 , and the discharge ports  144  are connected to the ventilation duct  160 . In this structure, the introduction ports  142  include the same cross-sectional area, while the cross-sectional area of the discharge port  144  is adjusted. Thereby, the flow resistances in the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  may be adjusted. 
         [0038]    As shown in the figures, when the heat dissipation fan  180  is arranged at the upper end of the ventilation duct  160 , the cross-sectional area of a discharge port  144  at one position is set to be smaller than that of another discharge port  144  at a lower position. Thereby, air flow resistance may increase as air flow up to an upper layer where a higher negative pressure is generated. Thereby, air can flow through the respective layers with a constant flow rate and flow velocity. 
         [0039]    In the illustrated embodiment, the introduction ports of the connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  are formed with six different introduction angles such that the introduction angles of neighboring connection ducts differ from each other by 15°. Alternatively, the discharge ports may be formed with different discharge angles. The angular difference between neighboring connection ducts and the number of different angles may be properly changed when necessary. 
         [0040]      FIG. 4  is a view illustrating configuration of a cabinet for electric devices according to a second embodiment of the present disclosure, and  FIG. 5  is a cross-sectional view illustrating connection ducts provided to the cabinet according to the second embodiment of the present disclosure. 
         [0041]    Referring to  FIG. 5 , each of the connection ducts  150  applied to the cabinet of the second embodiment is provided therein with a damper  152  for adjusting the flow resistance. 
         [0042]    In the first embodiment, various kinds of connection ducts  140 - 1 ,  140 - 2 ,  140 - 3 ,  140 - 4 ,  140 - 5 , and  140 - 6  are installed in the respective layers to adjust the degree of cooling in each layer. In the second embodiment, the same connection duct  150  is applied to each layer, and the flow resistance in each layer may be adjusted by adjusting the damper  152  of each connection duct  150 . 
         [0043]    As shown in  FIG. 5 , the damper  152  is provided in the connection duct  150  and connected to a hinge shaft  154  such that the angle of the damper  152  is adjustable. The opening rate of the connection duct  150  may be adjusted by adjusting the angle of the damper  152 . 
         [0044]    As shown in  FIG. 4 , the lowest connection duct is given the maximum opening rate, and the upper connection ducts are given lower opening rates such that the opening rate of one connect duct is higher than the opening rate of another connection duct positioned at higher level. The external air introduced into the respective device accommodation spaces may be regulated such that the flow rate and flow velocity of external air does not vary among the device accommodation spaces. 
         [0045]      FIG. 6  is a view illustrating configuration of a cabinet for electric devices according to a third embodiment of the present disclosure, and  FIG. 7  is a cross-sectional view illustrating connection ducts provided to the cabinet according to the third embodiment of the present disclosure. 
         [0046]    Referring to  FIG. 7 , each of the connection ducts  170  according to the third embodiment includes an introduction port  172  connected to a corresponding one of the device accommodation spaces  120  and a discharge port  174  connected to the ventilation duct. Herein, the cross-sectional area of the discharge port  174  is adjustable. Similar to the second embodiment, the flow resistance of air may be adjusted using a single connection duct  170 . 
         [0047]    As shown in the figures, the connection duct  170  includes a connection duct body  170   a  defining an introduction port and a pair of adjustment segments  170   b  hinge-coupled to the connection duct body  170   a.  The adjustment segments  170   b  include a square bracket-shaped cross section and are arranged engaged with each other. Thereby, the cross-sectional area of the discharge port  174  may be adjusted by adjusting the gap between the adjustment segments  170   b.    
         [0048]    Referring to  FIG. 6 , the cabinet  100  for electric devices according to the third embodiment is installed such that the respective device accommodation spaces  120  communicate with the ventilation duct  160  using the connection ducts  170 . The gap between the adjustment segments  170   b  may be adjusted in each layer to obtain a uniform air flow in the device accommodation spaces  120  in the respective layers. 
         [0049]    As shown in the figures, the gap between the adjustment segments  170   b  may be adjusted such that the gap in one layer is narrower than the gap in a lower layer such that the flow resistance of air passing through a connection duct is higher than the flow resistance of air passing through a lower connection duct. Thereby, external air may be uniformly introduced and circulated in the device accommodation spaces  120  of the respective layers. Accordingly, the entire interior of the cabinet  100  may be uniformly cooled. 
         [0050]    Typically, the amounts of heat generated from the electric devices in the respective layers are similar to each other. Accordingly, a uniform air flow may be produced in the respective device accommodation spaces in the cabinet regardless of the distance of the divisive accommodation spaces from the heat dissipation fan  180 . 
         [0051]    It&#39;s possible that different amounts of heat are generated from electric devices installed in the respective layers. In this case, the flow rate and flow velocity necessary for cooling of the electric devices in the respective layers may differ from one layer to another. In this case, the flow rate and flow velocity of air necessary for each layer may be adjusted in a manner that the flow resistance of a connection duct installed in a layer producing a large amount of heat is relatively decreased, and the flow resistance of a connection duct installed in a layer producing a small amount of heat is relatively increased. 
         [0052]    Some embodiments described above should be construed in all aspects as illustrative and not restrictive. The scope of protection sought by the present disclosure should be determined by the appended claims and their equivalents, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein. Also, the features and attributes of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure. Although the present disclosure provides certain preferred embodiments and applications, other embodiments that are apparent to those of ordinary skill in the art, including embodiments which do not provide all of the features and advantages set forth herein, are also within the scope of this disclosure. Accordingly, the scope of the present disclosure is intended to be defined only by reference to the appended claims.
Disclosed embodiments relate to a cabinet for electric devices and, more particularly, to a cabinet for electric devices which is capable of regulating flow of air employed as a cooling medium to uniformly cool the interior of the cabinet. In some embodiments, the cabinet includes a plurality of device accommodation spaces for accommodating the electric devices in a stacking manner, a ventilation duct for discharging heat generated from the device accommodation spaces, a heat dissipation fan for discharging hot air from the ventilation duct, and a plurality of connection ducts for connecting the device accommodation spaces to the ventilation duct, wherein a flow rate and flow velocity of air passing through each of the connection ducts is adjusted by differentiating flow resistances in the connection ducts provided to the respective layers from each other.