Humidifier for fuel cell

1. A humidifier for a fuel cell, the humidifier, comprising:

a housing having, at a first side, a moist air supply port through which moist air is supplied from a fuel cell stack and having, at a second side, a moist air discharge port;

a humidifying membrane disposed in the housing and configured to allow dry air to flow along the inside of the humidifying membrane; and

a bypass flow path formed in the housing to allow a part of the moist air supplied to the moist air supply port to continuously flow to the moist air discharge port without passing through the humidifying membrane;

wherein the housing further includes:

a housing main body into which the humidifying membrane is inserted, the housing main body including a first flow path wall disposed above the humidifying membrane; and

a housing cap having a second flow path wall disposed above the first flow path wall to be spaced apart from the first flow path wall, wherein the housing cap is coupled to an upper portion of the housing main body;

wherein the first flow path wall and the second flow path wall define the bypass flow path in cooperation with each other.

2. The humidifier of claim 1 , wherein a cross-sectional area of the bypass flow path is changed selectively.

3. The humidifier of claim 2 , wherein the housing cap includes:

a first cap member configured to be coupled to the housing main body and having the second flow path wall disposed at a first height with respect to the first flow path wall; and

a second cap member configured to be coupled to the housing main body and having the second flow path wall disposed at a second height different from the first height,

wherein the cross-sectional area of the bypass flow path is changed by coupling any one of the first cap member and the second cap member to the housing main body.

4. The humidifier of claim 2 , further comprising:

a first partition wall member having a first size and configured to partially block the bypass flow path; and

a second partition wall member having a second size different from the first size and configured to partially block the bypass flow path,

wherein the cross-sectional area of the bypass flow path is changed by disposing any one of the first partition wall member and the second partition wall member in the bypass flow path.

5. The humidifier of claim 4 , wherein a coupling groove, to which the first partition wall member or the second partition wall member is coupled, is formed in any one of the first flow path wall and the second flow path wall.

6. The humidifier of claim 2 , comprising:

a blocking member configured to partially open or close the bypass flow path; and

a controller configured to open or close the blocking member based on humidity of the fuel cell stack,

wherein the cross-sectional area of the bypass flow path is changed by opening or closing the blocking member.

7. The humidifier of claim 6 , wherein the blocking member is coupled to the second flow path wall to be movable upward and downward, the humidifier includes a lifting unit configured to selectively move the blocking member upward or downward, and the controller is configured to operate the lifting unit based on humidity of the fuel cell stack.

8. The humidifier of claim 7 , wherein the controller is configured to decrease the cross-sectional area of the bypass flow path by moving the blocking member downward when the humidity of the fuel cell stack is less than a target humidity range, and wherein the controller is configured to increase the cross-sectional area of the bypass flow path by moving the blocking member upward when the humidity of the fuel cell stack is greater than the target humidity range.