Humidifier for fuel cell

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

a membrane module which accommodates therein a humidifying membrane;

a first cap unit coupled to one side of the membrane module and supplying supply air to the membrane module;

a second cap unit coupled to another side of the membrane module and discharging humidified air introduced from the membrane module; and

a bypass tube provided in the second cap unit and bypassing condensate water introduced into the second cap unit to the membrane module,

wherein the bypass tube bypasses moisture, which is introduced into the second cap unit from the membrane module, to the membrane module by a pressure difference between the membrane module and the second cap unit.

2. The humidifier of claim 1 , wherein:

the membrane module includes support members which support both the one end and the other end of the humidifying membrane, and

the bypass tube is provided in the second cap unit, and bypass-connects an interior of the second cap unit and an interior of the membrane module through the support member.

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

a membrane module which accommodates therein a humidifying membrane;

a first cap unit coupled to one side of the membrane module and supplying supply air to the membrane module;

a second cap unit coupled to another side of the membrane module and discharging humidified air introduced from the membrane module; and

a bypass tube provided integrally on an inner wall surface of the second cap unit, and bypass-connecting the second cap unit and the membrane module,

wherein the bypass tube bypasses moisture, which is introduced into the second cap unit from the membrane module, to the membrane module by a pressure difference between the membrane module and the second cap unit.

4. The humidifier of claim 3 , wherein:

the bypass tube is integrally injection molded on the inner wall surface of the second cap unit which corresponds to the membrane module.

5. The humidifier of claim 4 , wherein the bypass tube includes:

a first tube which has an inlet formed at a lower end thereof, is disposed on the inner wall surface of the second cap unit in a vertical direction, and is integrally connected to the inner wall surface of the second cap unit; and

a second tube which is integrally connected to an upper end of the first tube, has an outlet connected with the membrane module, and is disposed on the upper end of the first tube so as to be directed toward the membrane module.

6. The humidifier of claim 5 , wherein:

the bypass tube includes at least one third tube which branches off from the first tube in a horizontal direction, extends in the vertical direction from the direction in which the third tube branches off, has another inlet formed at a lower end thereof, and is integrally connected to the inner wall surface of the second cap unit.

7. The humidifier of claim 3 , wherein:

the bypass tube includes a metal pipe which is formed by insert injection molding on the inner wall surface of the second cap unit which corresponds to the membrane module.

8. The humidifier of claim 7 , wherein:

the metal pipe is fixed to a fixing member integrally formed on the inner wall surface of the second cap unit, and includes a first tube which has an inlet formed at a lower end thereof and is fixed to the fixing member in the vertical direction, and a second tube integrally connected to an upper end of the first tube, has an outlet connected with the membrane module, and is fixed to the fixing member so as to be directed toward the membrane module.

9. The humidifier of claim 8 , wherein:

the metal pipe includes at least one third tube which branches off from the first tube in the horizontal direction, is fixed to the fixing member so as to extend in the vertical direction from the direction in which the third tube branches off, and has another inlet formed at a lower end thereof.

10. The humidifier of claim 5 , wherein:

the bypass tube is provided such that a cross-sectional area of the inlet of the first tube is larger than a cross-sectional area of the outlet of the second tube.

11. The humidifier of claim 5 , wherein:

the bypass tube is provided such that a cross section of the inlet of the first tube is diagonally formed toward the membrane module.

12. The humidifier of claim 3 , wherein:

the second cap unit has an air discharge port through which the humidified air introduced from the membrane module is discharged to a stack, and

the air discharge port is formed in an upper surface of the second cap unit so as to correspond to the second tube.

13. The humidifier of claim 3 , wherein:

the second cap unit has an air discharge port through which the humidified air introduced from the membrane module is discharged to a stack, and

the air discharge port is formed in a side surface of the second cap unit so as to correspond to the second tube.

14. The humidifier of claim 13 , wherein:

the bypass tube is provided integrally on the inner wall surface at the other side of the second cap unit.

15. The humidifier of claim 5 , wherein:

the inlet of the first tube is disposed in a direction different from an air flow direction in the second cap unit.

16. The humidifier of claim 4 , wherein:

the bypass tube includes a first tube disposed on the inner wall surface of the second cap unit so as to extend from the vertical direction to the horizontal direction, has an inlet formed in a direction different from an air flow direction in the second cap unit, and is integrally connected to the inner wall surface of the second cap unit; and

a second tube integrally connected to an upper end of the first tube, has an outlet connected with the membrane module, and is disposed on the upper end of the first tube so as to be directed toward the membrane module.

17. The humidifier of claim 4 , wherein:

the second cap unit includes a duct unit integrally formed on the inner wall surface which corresponds to the membrane module, has a plurality of inlets formed at a lower end thereof, gradually decreases in width upward, and is connected with the bypass tube.

18. The humidifier of claim 17 , wherein:

the bypass tube includes a first tube disposed on the inner wall surface of the second cap unit in the vertical direction, is connected with an upper portion of the duct unit, and is integrally formed on the inner wall surface of the second cap unit; and

a second tube integrally connected to an upper end of the first tube, has an outlet connected with the membrane module, and is disposed on the upper end of the first tube so as to be directed toward the membrane module.

19. The humidifier of claim 3 , wherein:

the membrane module includes support members which support both ends of the humidifying membrane, and

the bypass tube bypass-connects an interior of the second cap unit and an interior of the membrane module through the support member when the second cap unit is assembled to the membrane module.