Axial fan and refrigerator

An axial fan comprising:

• an impeller to rotate about a rotation axis extending in a vertical direction;
• a motor to rotationally drive the impeller;
• a housing radially outside the impeller and the motor;
• an intake port provided at an upper portion of the housing in the vertical direction;
• and
• an exhaust port provided at a lower portion of the housing in the vertical direction;
• wherein
• in a region overlapping in the vertical direction with the impeller, an inner wall surface of the housing includes at least one first wall including a narrow gap with a radially outer edge of the impeller and at least one second wall including a wide gap with the radially outer edge of the impeller;
• the housing includes a bottom plate at the lower portion;
• an outer wall surface of the housing extends upward from the outer edge of the bottom plate and has a square or substantially square shape in a cross-sectional view perpendicular to the vertical direction;
• the at least one first wall extends from the bottom plate to an upper end of the housing;
• the housing includes a space provided between the at least one second wall and the impeller;
• the space is defined by an empty void which extends all the way from the bottom plate to the upper end of the housing;
• the at least one first wall is provided in the center of one side of the housing;
• the at least one second wall includes a plurality of second walls located at positions nearer to four corners of the housing than the first wall is;
• the exhaust port is a circular opening;
• and
• an inner wall surface of the at least one first wall is flush with a circumferential edge of the exhaust port such that the inner wall surface of the at least one first wall and the circumferential edge of the exhaust port overlap with each other in an axial view parallel to the vertical direction.