Patent Publication Number: US-2023135382-A1

Title: Ventilation device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korea Patent Application No. 10-2021-0150734, filed on Nov. 4, 2021, which is incorporated herein by reference for all purposes as if fully set forth herein. 
     TECHNICAL FIELD 
     The present disclosure relates to a ventilation device. More specifically, the present disclosure relates to a ventilation device for refrigerator with an optimal structure of a scroll. 
     BACKGROUND 
     In general, a refrigerator can cool food or prevent spoilage by providing cold air using a refrigeration cycle device including a compressor, a condenser, an expansion mechanism, and an evaporator. A refrigerator is a device that stores food for a long time in a fresh state using cold air. 
     In the refrigerator, a ventilation device is installed on a flow path, which blows air into a refrigerator compartment and a freezer compartment after forcing the air to flow from the refrigerator compartment and the freezer compartment through the evaporator. 
     A refrigerator generally includes an outer case with a front opening, an inner case disposed in the outer case, a storage compartment (e.g., a refrigerator compartment or a refrigerator compartment) disposed in the inner case, and a door that is disposed on a front surface of the outer case to open and close the storage compartment. 
     In this case, the refrigerator may further include an evaporator that is formed on one side of the storage compartment and heat-exchanges a refrigerant and air to generate a cold air, a cold air flow path disposed between the outer case and the inner case, and a ventilation device that circulates the cold air from the evaporator to the storage compartment through the cold air flow path. 
     To increase the internal capacity of the refrigerator, it is necessary to reduce the size of the evaporator, the cold air flow path, and a fan. 
     When the size of the evaporator generating the cold air decreases, the number of cooling fins of the evaporator may increase to increase an amount of heat exchange per unit area. When the cold air flow path narrows, a flow path resistance may increase two times or more under the same flow rate condition. Therefore, the fan requires more than twice the work. 
     As disclosed in prior document 1 (Korean Patent No. 10-0389395) and prior document 2 (Korean Patent No. 10-1577875), a diameter of a turbofan is generally about 110 mm to 140 mm, and a rotational speed is about 1200 rpm. Here, the turbofan may indicate a fan in which blades are formed to be convex in a rotation direction of the fan. 
     If the diameter of the fan is reduced to 85 mm, the rotational speed of the fan is inversely proportional to fan’s diameter to the power of 3 according to the affinity laws of the fan. Therefore, the rotational speed of the fan increases up to 2600 rpm. 
     Further, as mentioned above, when the flow path resistance increases by more than two times as the number of cooling fins increases and the flow path narrows, the rotational speed of the fan excessively increases according to the affinity laws. 
     There is a problem in that noise increases due to an aerodynamic force or a vibration resultant from an excessive increase in the number of revolutions of the fan. 
     There is also a problem in that the excessive increase in the number of revolutions of the fan reduces the lifespan of components such as a motor and an oil-impregnated bushing bearing. 
     Prior Art Document 
     
         
         (Patent Document 1) Korean Patent No. 10-0389395 B (published on Jun. 27, 2003) 
         (Patent Document 2) Korean Patent No. 10-1577875 B (published on Dec. 28, 2015) 
       
    
     SUMMARY 
     An object of the present disclosure is to provide a ventilation device capable of reducing the number of revolutions of a fan while increasing an internal capacity of a refrigerator. 
     Another object of the present disclosure is to provide a ventilation device for reducing a noise due to an aerodynamic force or a vibration generated by an increase in the number of revolutions of a fan. 
     Another object of the present disclosure is to provide a ventilation device capable of improving lifespan of components of a refrigerator. 
     Another object of the present disclosure is to provide a ventilation device capable of improving efficiency by preventing a cold air from flowing backward and preventing a vortex from occurring. 
     Another object of the present disclosure is to provide a ventilation device capable of reducing the number of revolutions of a fan by reducing a minimum shaft power. 
     Another object of the present disclosure is to provide a ventilation device capable of improving discharge efficiency of a cold air discharged from a fan. 
     Another object of the present disclosure is to provide a ventilation device capable of reducing a vibration and a noise generated by a difference in a gap between a fan and a scroll. 
     In order to achieve the above and other objects, in one aspect of the present disclosure, there is provided a ventilation device comprising a fan comprising a hub coupled to a rotating shaft, a plurality of blades disposed at the hub and disposed radially with respect to the rotating shaft, and a shroud connecting the plurality of blades, a scroll guide configured to guide a cold air discharged from the fan in both directions, and first and second ducts extending from the scroll guide and extending along a rotation direction of the fan. 
     In this case, in the first and second ducts, a length of a hub-side surface may be greater than a length of a shroud-side surface. 
     Hence, the present disclosure can improve efficiency of the ventilation device by preventing a cold air, that is discharged from the fan and passes through the first and second ducts, from flowing backward and preventing a vortex from occurring. 
     The first duct may comprise a first surface connecting a first hub-side surface and a first shroud-side surface, and a second surface that connects the first hub-side surface and the first shroud-side surface and is disposed along the rotation direction of the fan as compared to the first surface. The first surface and the second surface may form a predetermined angle. 
     An angle between a straight line passing through a shroud-side cutoff point of the second surface and a center of the fan and a straight line passing through a hub-side cutoff point of the second surface and the center of the fan may be 15 ° to 35 °. Hence, the present disclosure can reduce the number of revolutions of the fan by reducing a minimum shaft power. 
     The first surface may comprise a first curved portion extending from the scroll guide and a first straight portion extending from the first curved portion. The second surface may comprise a second straight portion extending from the scroll guide. 
     In this case, an angle between the first straight portion and a line extending in a horizontal direction from the center of the fan may be 32 ° to 43 °. Hence, the present disclosure can reduce noise generated in the fan by reducing the minimum shaft power. 
     An angle between the first straight portion and a hub-side line of the second straight portion may be 32.5 ° to 35.5 °. Hence, the present disclosure can reduce the number of revolutions of the fan by reducing the minimum shaft power. 
     The second duct may comprise a third surface connecting a second hub-side surface and a second shroud-side surface, and a fourth surface that connects the second hub-side surface and the second shroud-side surface and is disposed along the rotation direction of the fan as compared to the third surface. The third surface and the fourth surface may form a predetermined angle. 
     A straight line passing through a shroud-side cutoff point of the fourth surface and the center of the fan and a straight line passing through a hub-side cutoff point of the fourth surface and the center of the fan may form a predetermined angle. 
     The third surface may comprise a second curved portion extending from the scroll guide and a third straight portion extending from the second curved portion. The fourth surface may comprise a fourth straight portion extending from the scroll guide. 
     In this case, an angle between the third straight portion and a line extending in a vertical direction from the center of the fan may be 63 ° to 69 °. Hence, the present disclosure can reduce noise generated in the fan by reducing the minimum shaft power. 
     An angle between the third straight portion and a hub-side line of the fourth straight portion may be 6.5 ° to 9.5 °. Hence, the present disclosure can reduce the number of revolutions of the fan by reducing the minimum shaft power. 
     An angle between a straight line connecting a hub-side cutoff point of the second surface and the center of the fan and a straight line connecting a hub-side cutoff point of the fourth surface and the center of the fan may be 117 ° to 132 °. Hence, the present disclosure can provide an optimal scroll structure. 
     The first duct may extend in a downward direction of the scroll guide, and the second duct may extend in an upward direction of the scroll guide. Hence, the present disclosure can improve discharge efficiency of the cold air discharged from the fan. 
     Lines connecting shroud-side cutoff points and hub-side cutoff points of the first and second ducts may be a straight line. Static pressure rise efficiency when the lines connecting the shroud-side cutoff points and the hub-side cutoff points of the first and second ducts are a straight line can further increase as compared to when the lines connecting the shroud-side cutoff points and the hub-side cutoff points of the first and second ducts are a curved line. Accordingly, the present disclosure can reduce the generation of vortex around the cutoff points and prevent the cold air from flowing backward. 
     There may be a uniform distance between the scroll guide and the fan. Hence, the present disclosure can reduce a vibration and a noise generated by a difference in a gap between the fan and the scroll guide. 
     Cross-sectional areas of the first and second ducts may increase as the first and second ducts become far away from the fan. Hence, the present disclosure can prevent the cold air from flowing backward and can allow the cold air to flow in the duct. 
     The blade may be formed to be entirely concave in the rotation direction. Hence, the present disclosure can maintain the lower number of revolutions of the fan than a turbofan while increasing the internal capacity of the refrigerator. Further, the present disclosure can reduce noise due to an aerodynamic force or a vibration generated by an increase in the number of revolutions of the fan, and can increase lifespan of components of the refrigerator by reducing the number of revolutions of the fan. 
     The present disclosure can provide a ventilation device capable of reducing the number of revolutions of a fan while increasing an internal capacity of a refrigerator. 
     The present disclosure can provide a ventilation device for reducing a noise due to an aerodynamic force or a vibration generated by an increase in the number of revolutions of a fan. 
     The present disclosure can provide a ventilation device capable of improving lifespan of components of a refrigerator. 
     The present disclosure can provide a ventilation device capable of improving efficiency by preventing a cold air from flowing backward and preventing a vortex from occurring. 
     The present disclosure can provide a ventilation device capable of reducing the number of revolutions of a fan by reducing a minimum shaft power. 
     The present disclosure can provide a ventilation device capable of improving discharge efficiency of a cold air discharged from a fan. 
     The present disclosure can provide a ventilation device capable of reducing a vibration and a noise generated by a difference in a gap between a fan and a scroll. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the present disclosure and constitute a part of the detailed description, illustrate embodiments of the present disclosure and serve to explain technical features of the present disclosure together with the description. 
         FIG.  1    is a cross-sectional view of a refrigerator according to an embodiment of the present disclosure. 
         FIG.  2    is a cross-sectional view of a ventilation device according to an embodiment of the present disclosure. 
         FIG.  3    is a perspective view of a fan according to an embodiment of the present disclosure. 
         FIG.  4    is a plan view of a fan according to an embodiment of the present disclosure. 
         FIG.  5    is a cross-sectional view of a fan according to an embodiment of the present disclosure. 
         FIG.  6    is an enlarged view of a part A of  FIG.  4   . 
         FIG.  7    schematically illustrates a blade according to an embodiment of the present disclosure. 
         FIG.  8    is a perspective view illustrating a scroll guide and a duct according to an embodiment of the present disclosure. 
         FIG.  9    is a cross-sectional view illustrating a scroll guide, a duct, and a fan according to an embodiment of the present disclosure. 
         FIG.  10    illustrates operation of a scroll guide, a duct, and a fan according to an embodiment of the present disclosure. 
         FIG.  11    illustrates a flow of a cold air in a scroll guide and a duct according to a related art. 
         FIG.  12    illustrates a flow of a cold air in a scroll guide and a duct according to an embodiment of the present disclosure. 
         FIGS.  13  to  18    are graphs illustrating a minimum shaft power depending on a shape of a duct according to an embodiment of the present disclosure. 
         FIGS.  19  to  21    illustrate a line connecting cutoff points of a duct according to an embodiment of the present disclosure. 
         FIG.  22    is a graph illustrating a static pressure depending on a shape of a line connecting cutoff points of a duct according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     It should be understood that when a component is described as being “connected to” or “coupled to” other component, it may be directly connected or coupled to the other component or intervening component(s) may be present. 
     It will be noted that a detailed description of known arts will be omitted if it is determined that the detailed description of the known arts can obscure embodiments of the present disclosure. The accompanying drawings are used to help easily understand various technical features and it should be understood that embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be understand to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. 
     In addition, a term of “disclosure” may be replaced by document, specification, description, etc. 
       FIG.  1    is a cross-sectional view of a refrigerator according to an embodiment of the present disclosure. 
     Referring to  FIG.  1   , a refrigerator  10  according to an embodiment of the present disclosure may include an outer case  11 , an inner case  12 , a door  13 , an evaporator  14 , a cold air flow path  16 , and a ventilation device  100 . However, the refrigerator  10  may be implemented including more or less components according to an embodiment. 
     The outer case  11  may have a front opening and an inner space. The outer case  11  may form an appearance of the refrigerator  10 . The outer case  11  may be formed substantially in a hexahedral shape with the front opening. However, the outer case  11  is not limited thereto and can be variously changed. 
     The inner case  12  may be disposed inside the outer case  11 . The inner case  12  may be spaced apart from the outer case  11 . The inner case  12  may include an inner space. A storage compartment may be formed in the inner space of the inner case  12 . The storage compartment may be referred to as a refrigerator compartment or a freezer compartment. The storage compartment may include a plurality of storage compartments. The plurality of storage compartments may be maintained in different temperature zones. One of the plurality of storage compartments may be a refrigerator compartment, and other may be a freezer compartment. 
     The door  13  may be disposed at a front surface of the outer case  11 . The door  13  may selectively open and close the storage compartment by a user. A plurality of doors  13  may be provided depending on the number of storage compartments. 
     The evaporator  14  may be disposed between the outer case  11  and the inner case  12 . The evaporator  14  may be disposed at one side or the rear of the storage compartment. The evaporator  14  may be disposed under the cold air flow path  16 . The evaporator  14  may be disposed under the ventilation device  100 . The evaporator  14  may be disposed in a lower area of the refrigerator  10 . The evaporator  14  may heat-exchange air supplied from the storage compartment with a refrigerant to generate a cold air. The cold air generated by the evaporator  14  may be provided to the ventilation device  100 . 
     The evaporator  14  may include a plurality of evaporators. One of the plurality of evaporators may cool the refrigerator compartment, and the other may cool the freezer compartment. Alternatively, both the refrigerator compartment and the freezer compartment may be cooled by one evaporator. 
     The refrigerator  10  according to an embodiment of the present disclosure may include a refrigeration cycle device including a compressor (not shown) for compressing the refrigerant, a condenser (not shown) for condensing the refrigerant compressed by the compressor, an expansion mechanism for expanding the refrigerant condensed by the condenser, and the evaporator  14  to which the refrigerant expanded by the expansion mechanism is provided. 
     The cold air flow path  16  may be disposed between the outer case  11  and the inner case  12 . The cold air flow path  16  may be disposed at one side or the rear of the storage compartment. The cold air flow path  16  may extend in an up-down direction or a vertical direction. The cold air flow path  16  may provide a path through which the cold air flows. One side of the cold air flow path  16  may be connected to the ventilation device  100 , and the other side may be connected to the storage compartment. The cold air flow path  16  may be disposed on the ventilation device  100 . The cold air flow path  16  may be disposed on the evaporator  14 . 
     The ventilation device  100  may be disposed between the outer case  11  and the inner case  12 . The ventilation device  100  may be disposed under the cold air flow path  16 . The ventilation device  100  may be disposed in a lower area of the cold air flow path  16 . The ventilation device  100  may be disposed on the evaporator  14 . The ventilation device  100  may flow the cold air generated by the evaporator  14  to the storage compartment through the cold air flow path  16 . 
       FIG.  2    is a cross-sectional view of a ventilation device according to an embodiment of the present disclosure. 
     Referring to  FIG.  2   , the ventilation device  100  according to an embodiment of the present disclosure may include a housing  120 , a motor  150 , and a fan  200 . However, the ventilation device  100  may be implemented including more or less components according to an embodiment. 
     The housing  120  may include an intake port  120   a  through which cold air generated by the evaporator  14  is sucked, and a discharge port  120   b  for discharging the refrigerant passing through the fan  200 . The housing  120  may be fixed to the motor  150 . The fan  200  may be rotatably disposed inside the housing  120 . The housing  120  may form a flow path for cold air and air. 
     A bell mouth  110  may extend from the housing  120 . The bell mouth  110  may be formed in a central area of the rear of the housing  120 . An inner diameter of the bell mouth  110  may increase as it goes toward the fan  200 . Further, the ventilation device  100  may include a convex portion  110   a  that is formed between the bell mouth  110  and the housing  120  to be convex toward the fan  200 . 
     The motor  150  may be driven by external power. The motor  150  may be coupled to the housing  120 . A rotating shaft  151  of the motor  150  may be coupled to the fan  200 . The motor  150  may allow the fan  200  to rotate in one direction according to the rotation of the rotating shaft  151  of the motor  150 . 
     The fan  200  may be disposed in the housing  120 . The fan  200  may be rotatably connected to the motor  150 . The fan  200  may rotate in one direction according to the rotation of the rotating shaft  151  of the motor  150 . The fan  200  may be disposed in front of the motor  150 . 
       FIG.  3    is a perspective view of a fan according to an embodiment of the present disclosure.  FIG.  4    is a plan view of a fan according to an embodiment of the present disclosure.  FIG.  5    is a cross-sectional view of a fan according to an embodiment of the present disclosure.  FIG.  6    is an enlarged view of a part A of  FIG.  4   .  FIG.  7    schematically illustrates a blade according to an embodiment of the present disclosure. 
     Referring to  FIGS.  3  to  7   , the fan  200  according to an embodiment of the present disclosure may include a hub  210 , a blade  230 , a shroud  220 , and a coupling portion  240 . However, the fan  200  may be implemented including more or less components according to an embodiment. 
     The hub  210  may be disposed in the housing  120 . The hub  210  may be rotatably coupled to the motor  150 . The hub  210  may be coupled to the rotating shaft  151  of the motor  150 . The hub  210  may rotate in one direction according to the rotation of the rotating shaft  151  of the motor  150 . The blade  230  may be disposed at the hub  210 . 
     The hub  210  may include a first area  212 . The blade  230  may be disposed in the first area  212 . The blade  230  may be disposed on a front surface of the first area  212 . The first area  212  may be formed flat. The first area  212  may be disposed closer to the motor  150  than a second area  214 . The first area  212  may be disposed behind the second area  214 . 
     The hub  210  may include the second area  214 . The second area  214  may extend from the first area  212 . The second area  214  may have curvature. The second area  214  may be formed to be convex in the opposite direction or forward of the motor  150 . The second area  214  may be formed in a semicircular shape. The second area  214  may have an infection point. Hence, the hub  210  can improve the intake efficiency of the cold air while guiding the air or refrigerant sucked through the intake port  120   a  toward the blade  230  disposed in the first area  212 . 
     The blade  230  may be disposed at the hub  210 . The blade  230  may be disposed in the first area  212  of the hub  210 . The blade  230  may be disposed on the front surface of the first area  212  of the hub  210 . The blade  230  may be spaced apart from a central area of the hub  210 . The blade  230  may have entirely curvature. The blade  230  may have no inflection point. A width of the blade  230  may be constant. Here, the width of the blade  230  may indicate a minimum distance between a pressure surface  233  and a negative pressure surface  232 . 
     The blade  230  may include a leading edge  231  disposed at a radially inner side of the fan  200 , a trailing edge  234  disposed at a radially outer side of the fan  200 , the pressure surface  233  that connects the leading edge  231  and the trailing edge  234  and is disposed along the rotation direction of the fan  200 , and the negative pressure surface  232  that connects the leading edge  231  and the trailing edge  234  and is disposed in the opposite direction of the rotation direction of the fan  200 . The pressure surface  233  has a higher pressure than the atmospheric pressure and thus can push out the air. The negative pressure surface  232  is a rear surface of the pressure surface  233  and may have a pressure lower than the atmospheric pressure. The leading edge  231  may contact the cold air introduced through the intake port  120   a , and the trailing edge  234  may discharge the cold air toward the discharge port  120   b . 
     In one embodiment of the present disclosure, a minimum distance between a center of the leading edge  231  and a center of the trailing edge  234  is defined as a chord length L 2 ; a virtual line connecting the center of the leading edge  231  and the center of the trailing edge  234  in a straight line is defined as a chord line; a line connecting midpoints of the pressure surface  233  and the negative pressure surface  232  is defined as a camber line L 1 ; when a virtual line perpendicular to the chord line is connected to the camber line L 1 , a height at a maximum camber is defined as a maximum camber amount L 3 ; and a distance from the leading edge  231  to the maximum camber is defined as a maximum camber position L 4 . 
     The blade  230  may be formed to be entirely concave in the rotation direction. For example, with reference to  FIG.  4   , when the fan  200  rotates clockwise, the blade  230  may be formed to be concave clockwise or convex counterclockwise. The trailing edge  234  of the blade  230  which is a radially outer end of the fan  200  may be disposed along the rotation direction, as compared to the leading edge  231  which is a radially inner end of the fan  200 . For example, with reference to  FIG.  4   , when the fan  200  rotates clockwise, the trailing edge  234  may be disposed more clockwise or to the right than the leading edge  231 . 
     In this case, since the chord length L 2  is shorter than that of a turbofan according to the related art, the number of blades  230   a ,  230   b , and  230   c  can increase. Hence, the present disclosure can further reduce the number of revolutions of the fan under the same flow rate and discharge pressure conditions, as compared to that of the turbofan according to the related art. 
     Further, the present disclosure can maintain the fan  200  at the lower number of revolutions than the turbofan according to the related art while increasing the internal capacity of the refrigerator  10 . 
     Accordingly, the present disclosure can reduce noise due to an aerodynamic force or a vibration generated by an increase in the number of revolutions of the fan  200 . Further, the present disclosure can increase lifespan of the components of the refrigerator  10 , for example, the motor  150  and an oil-impregnated bushing bearing by reducing the number of revolutions of the fan  200 . 
     The blade  230  may include the plurality of blades  230   a ,  230   b , and  230   c . The plurality of blades  230   a ,  230   b , and  230   c  may be disposed radially with respect to the rotating shaft  151  of the motor  150 . The plurality of blades  230   a ,  230   b , and  230   c  may be disposed radially with respect to the central area of the hub  210 . The plurality of blades  230   a ,  230   b , and  230   c  may be spaced apart from each other in a circumferential direction. 
     The shroud  220  may be coupled to the front surface of the blade  230 . The shroud  220  may be coupled to an outer surface or the trailing edge of the blade  230 . The shroud  220  may connect the plurality of blades  230 . The shroud  220  may be formed in a circular band shape or a ring shape. 
     The coupling portion  240  may be formed in the hub  210 . The coupling portion  240  may be formed in the central area of the hub  210 . The coupling portion  240  may be formed in a central portion of the second area  214  of the hub  210 . The coupling portion  240  may be coupled to the rotating shaft  151  of the motor  150 . 
       FIG.  8    is a perspective view illustrating a scroll guide and a duct according to an embodiment of the present disclosure.  FIG.  9    is a cross-sectional view illustrating a scroll guide, a duct, and a fan according to an embodiment of the present disclosure.  FIG.  10    illustrates operation of a scroll guide, a duct, and a fan according to an embodiment of the present disclosure.  FIG.  11    illustrates a flow of a cold air in a scroll guide and a duct according to a related art.  FIG.  12    illustrates a flow of a cold air in a scroll guide and a duct according to an embodiment of the present disclosure.  FIGS.  13  to  18    are graphs illustrating a minimum shaft power depending on a shape of a duct according to an embodiment of the present disclosure. 
     Referring to  FIGS.  8  to  10   , the housing  120  may include a scroll guide  122 , a first duct  124 , and a second duct  126 . However, the housing  120  may be implemented including more or less components according to an embodiment. 
     The fan  200  may be disposed inside the scroll guide  122 . The scroll guide  122  may guide the cold air discharged from the fan  200  in both directions. An inner surface of the scroll guide  122  may be spaced apart from the fan  200 . A separation distance between the scroll guide  122  and the fan  200  may be constant. Through this, it is possible to reduce vibration or noise generated due to an irregular separation distance between the scroll guide  122  and the fan  200 . The scroll guide  122  may be connected to the first duct  124  and the second duct  126 . The first duct  124  may be connected below the scroll guide  122 , and the second duct  126  may be connected above the scroll guide  122 . The scroll guide  122  may guide the cold air discharged from the fan  200  to the first duct  124  and the second duct  126 . 
     The ducts  124  and  126  may extend from the scroll guide  122  and extend along the rotation direction of the fan  200 . An embodiment of the present disclosure describes a double scroll structure in which the two ducts  124  and  126  are formed, by way of example. 
     Cross-sectional areas of the first duct  124  and the second duct  126  may increase as they become far away from the fan  200 . Hence, this can prevent the cold air from flowing backward and can allow the cold air to flow smoothly in the duct. 
     The first duct  124  may extend from the bottom toward an upper left end of the fan  200 . The first duct  124  may extend from a lower part of the scroll guide  122  in a rotation direction Wo of the fan  200 . The first duct  124  may include a first shroud-side surface  124   a , a first hub-side surface  124   b , a first surface  124   c , and a second surface  124   d . 
     A length of the first hub-side surface  124   b  may be formed to be greater than a length of the first shroud-side surface  124   a . Specifically, referring to  FIG.  8   , a horizontal length of the first hub-side surface  124   b  may be greater than a horizontal length of the first shroud-side surface  124   a  on the same plane. That is, a cross-section of the first duct  124  may be formed in a trapezoidal shape. 
     The first surface  124   c  may connect the first hub-side surface  124   b  and the first shroud-side surface  124   a . The first surface  124   c  may be positioned in a direction opposite to the rotation direction Wo of the fan  200 , as compared to the second surface  124   d . 
     The first surface  124   c  and the second surface  124   d  may form a predetermined angle. Specifically, the first surface  124   c  and the second surface  124   d  may not be parallel to each other. 
     When viewed from the front of the refrigerator  10 , the first surface  124   c  may include a first curved portion  1242  extending from the scroll guide  122  and a first straight portion  1244  extending from the first curved portion  1242 . Through this, the smooth flow of cold air from the fan  200  to the first duct  124  is enabled. 
     The second surface  124   d  may connect the first hub-side surface  124   b  and the first shroud-side surface  124   a . The second surface  124   d  may be disposed along the rotation direction Wo of the fan  200 , as compared to the first surface  124   c . 
     The second surface  124   d  may include a second straight portion  1245  extending from the scroll guide  122 . 
     A straight line passing through a shroud-side cutoff point  1243   a  of the second surface  124   d  and the center O of the fan  200  and a straight line passing through a hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  may have a predetermined angle CL. 
     Referring to  FIG.  10   , in the related art, if a straight line passing through a shroud-side cutoff point  1243   a  of a second surface  124   d  and the center O of a fan  200  and a straight line passing through a hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  do not have a predetermined angle, it can be seen that a vortex occurs in an area connecting the shroud-side cutoff point  1243   a  of the second surface  124   d  and the hub-side cutoff point  1243   b  of the second surface  124   d . 
     Referring to  FIG.  11   , in the ventilation device  100  according to an embodiment of the present disclosure, since the straight line passing through the shroud-side cutoff point  1243   a  of the second surface  124   d  and the center O of the fan  200  and the straight line passing through the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  have the predetermined angle CL, a refrigerant having a relatively high discharge speed as passing through the hub  210  of the fan  200  is first introduced into the first duct  124 , and a refrigerant having a relatively low discharge speed as passing through the shroud  220  of the fan  200  is then introduced into the first duct  124 . Hence, a vortex can be prevented from occurring in an area connecting the shroud-side cutoff point  1243   a  of the second surface  124   d  and the hub-side cutoff point  1243   b  of the second surface  124   d . Further, the efficiency of the ventilation device  100  can be improved by preventing the reverse flow of cold air. 
     The angle CL between the straight line passing through the shroud-side cutoff point  1243   a  of the second surface  124   d  and the center O of the fan  200  and the straight line passing through the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  may be 15 ° to 35 °. Referring to  FIG.  13   , when the angle CL between the straight line passing through the shroud-side cutoff point  1243   a  of the second surface  124   d  and the center O of the fan  200  and the straight line passing through the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  is 25 °, the required shaft power of the ventilation device  100  is minimized. That is, when the angle CL between the straight line passing through the shroud-side cutoff point  1243   a  of the second surface  124   d  and the center O of the fan  200  and the straight line passing through the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  is 15 ° to 35 °, the required shaft power is minimized as compared to other areas. Therefore, the present disclosure can reduce the number of revolutions of the fan  200  and also reduce the size of the ventilation device  100 . 
     An angle L 1  between the first straight portion  1244  and a line X extending in the horizontal direction from the center O of the fan  200  may be 32 ° to 43 °. Referring to  FIG.  14   , when the angle L 1  between the first straight portion  1244  and the line X extending in the horizontal direction from the center O of the fan  200  is 38 °, the required shaft power of the ventilation device  100  is minimized. That is, when the angle L 1  between the first straight portion  1244  and the line X extending in the horizontal direction from the center O of the fan  200  is 32 ° to 43 °, the required shaft power is minimized as compared to other areas. Therefore, the present disclosure can reduce the number of revolutions of the fan  200  and also reduce the size of the ventilation device  100 . 
     An angle L 2  between the first straight portion  1244  and a hub-side line  1245   b  of the second straight portion  1245  may be 32.5 ° to 35.5 °. Referring to  FIG.  15   , when the angle L 2  between the first straight portion  1244  and the hub-side line  1245   b  of the second straight portion  1245  is 34 °, the required shaft power of the ventilation device  100  is minimized. That is, when the angle L 2  between the first straight portion  1244  and the hub-side line  1245   b  of the second straight portion  1245  is 32.5 ° to 35.5 °, the required shaft power is minimized as compared to other areas. Therefore, the present disclosure can reduce the number of revolutions of the fan  200  and also reduce the size of the ventilation device  100 . 
     The second duct  126  may extend from the top toward an upper right end of the fan  200 . The second duct  126  may extend from an upper part of the scroll guide  122  in the rotation direction Wo of the fan  200 . The second duct  126  may include a second shroud-side surface  126   a , a second hub-side surface  126   b , a third surface  126   c , and a fourth surface  126   d . 
     A length of the second hub-side surface  126   b  may be formed to be greater than a length of the second shroud-side surface  126   a . Specifically, referring to  FIG.  8   , a horizontal length of the second hub-side surface  126   b  may be greater than a horizontal length of the second shroud-side surface  126   a  on the same plane. That is, a cross-section of the second duct  126  may be formed in a trapezoidal shape. 
     The third surface  126   c  may connect the second hub-side surface  126   b  and the second shroud-side surface  126   a . The third surface  126   c  may be positioned in a direction opposite to the rotation direction Wo of the fan  200 , as compared to the fourth surface  126   d . 
     The third surface  126   c  may include a second curved portion  1262  extending from the scroll guide  122  and a third straight portion  1264  extending from the second curved portion  1262 . 
     The fourth surface  126   d  may connect the second hub-side surface  126   b  and the second shroud-side surface  126   a . The fourth surface  126   d  may be disposed along the rotation direction Wo of the fan  200 , as compared to the third surface  126   c . 
     The third surface  126   c  and the fourth surface  126   d  may form a predetermined angle. Specifically, the third surface  126   c  and the fourth surface  126   d  may not be parallel to each other. 
     A straight line passing through a shroud-side cutoff point  1263   a  of the fourth surface  126   d  and the center O of the fan  200  and a straight line passing through a hub-side cutoff point  1263   b  of the fourth surface  126   d  and the center O of the fan  200  may have a predetermined angle. 
     Referring to  FIG.  10   , in the related art, if a straight line passing through a shroud-side cutoff point  1263   a  of a fourth surface  126   d  and the center O of the fan  200  and a straight line passing through a hub-side cutoff point  1263   b  of the fourth surface  126   d  and the center O of the fan  200  do not have a predetermined angle, it can be seen that a vortex occurs in an area connecting the shroud-side cutoff point  1263   a  of the fourth surface  126   d  and the hub-side cutoff point  1263   b  of the fourth surface  126   d . 
     Referring to  FIG.  11   , in the ventilation device  100  according to an embodiment of the present disclosure, since the straight line passing through the shroud-side cutoff point  1263   a  of the fourth surface  126   d  and the center O of the fan  200  and the straight line passing through the hub-side cutoff point  1263   b  of the fourth surface  126   d  and the center O of the fan  200  have the predetermined angle CL, a refrigerant having a relatively high discharge speed as passing through the hub  210  of the fan  200  is first introduced into the second duct  126 , and a refrigerant having a relatively low discharge speed as passing through the shroud  220  of the fan  200  is then introduced into the second duct  126 . Hence, a vortex can be prevented from occurring in an area connecting the shroud-side cutoff point  1263   a  of the fourth surface  126   d  and the hub-side cutoff point  1263   b  of the fourth surface  126   d . Further, the efficiency of the ventilation device  100  can be improved by preventing the reverse flow of cold air. 
     The fourth surface  126   d  may include a fourth straight portion  1265  extending from the scroll guide  122 . 
     An angle R 1  between the third straight portion  1264  and a line Y extending in the vertical direction from the center O of the fan  200  may be 63 ° to 69 °. Referring to  FIG.  16   , when the angle R 1  between the third straight portion  1264  and the line Y extending in the vertical direction from the center O of the fan  200  is 66 °, the required shaft power of the ventilation device  100  is minimized. That is, when the angle R 1  between the third straight portion  1264  and the line Y extending in the vertical direction from the center O of the fan  200  is 63 ° to 69 °, the required shaft power is minimized as compared to other areas. Therefore, the present disclosure can reduce the number of revolutions of the fan  200  and also reduce the size of the ventilation device  100 . 
     An angle R 2  between the third straight portion  1264  and a hub-side line  1265   b  of the fourth straight portion  1265  may be 6.5 ° to 9.5 °. Referring to  FIG.  17   , when the angle R 2  between the third straight portion  1264  and the hub-side line  1265   b  of the fourth straight portion  1265  is 8 °, the required shaft power of the ventilation device  100  is minimized. That is, when the angle R 2  between the third straight portion  1264  and the hub-side line  1265   b  of the fourth straight portion  1265  is 6.5 ° to 9.5 °, the required shaft power is minimized as compared to other areas. Therefore, the present disclosure can reduce the number of revolutions of the fan  200  and also reduce the size of the ventilation device  100 . 
     An angle CA between a straight line connecting the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  and a straight line connecting the hub-side cutoff point  1263   b  of the fourth surface  126   d  and the center O of the fan  200  may be 117 ° to 132 °. Referring to  FIG.  18   , when the angle CA between the straight line connecting the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  and the straight line connecting the hub-side cutoff point  1263   b  of the fourth surface  126   d  and the center O of the fan  200  is 125 °, the required shaft power of the ventilation device  100  is minimized. That is, when the angle CA between the straight line connecting the hub-side cutoff point  1243   b  of the second surface  124   d  and the center O of the fan  200  and the straight line connecting the hub-side cutoff point  1263   b  of the fourth surface  126   d  and the center O of the fan  200  is 117 ° to 132 °, the required shaft power is minimized as compared to other areas. Therefore, the present disclosure can reduce the number of revolutions of the fan  200  and also reduce the size of the ventilation device  100 . 
       FIGS.  19  to  21    illustrate a line connecting cutoff points of a duct according to an embodiment of the present disclosure.  FIG.  22    is a graph illustrating a static pressure depending on a shape of a line connecting cutoff points of a duct according to an embodiment of the present disclosure. 
     Referring to  FIG.  19   , lines  1243  and  1263  connecting the shroud-side cutoff points  1243   a  and  1263   a  and the hub-side cutoff points  1243   b  and  1263   b  of the first and second ducts  124  and  126  may be formed to be convex in the radially outward direction of the fan  200 . 
     Referring to  FIG.  20   , the lines  1243  and  1263  connecting the shroud-side cutoff points  1243   a  and  1263   a  and the hub-side cutoff points  1243   b  and  1263   b  of the first and second ducts  124  and  126  may be formed as a straight line. 
     Referring to  FIG.  21   , the lines  1243  and  1263  connecting the shroud-side cutoff points  1243   a  and  1263   a  and the hub-side cutoff points  1243   b  and  1263   b  of the first and second ducts  124  and  126  may be formed to be concave in the radially inward direction of the fan  200 . 
     Referring to  FIG.  22   , static pressure rise efficiency when the lines  1243  and  1263  connecting the shroud-side cutoff points  1243   a  and  1263   a  and the hub-side cutoff points  1243   b  and  1263   b  of the first and second ducts  124  and  126  are formed as a straight line can further increase as compared to static pressure rise efficiency when the lines  1243  and  1263  connecting the shroud-side cutoff points  1243   a  and  1263   a  and the hub-side cutoff points  1243   b  and  1263   b  of the first and second ducts  124  and  126  are formed to be convex or concave. 
     That is, as the lines  1243  and  1263  connecting the shroud-side cutoff points  1243   a  and  1263   a  and the hub-side cutoff points  1243   b  and  1263   b  of the first and second ducts  124  and  126  are formed as a straight line, the present disclosure can reduce the generation of vortex around the cutoff points and prevent the cold air from flowing backward by increasing the static pressure rise efficiency. 
     Some embodiments or other embodiments of the present disclosure described above are not exclusive or distinct from each other. Some embodiments or other embodiments of the present disclosure described above can be used together or combined in configuration or function. 
     For example, configuration “A” described in an embodiment and/or the drawings and configuration “B” described in another embodiment and/or the drawings can be combined with each other. That is, even if the combination between the configurations is not directly described, the combination is possible except in cases where it is described that it is impossible to combine. 
     The above detailed description is merely an example and is not to be considered as limiting the present disclosure. The scope of the present disclosure should be determined by rational interpretation of the appended claims, and all variations within the equivalent scope of the present disclosure are included in the scope of the present disclosure.