Heat exchanger

1. A heat exchanger comprising:

a plurality of flow channels, wherein

the heat exchanger is configured to exchange heat between fluid flowing through the plurality of flow channels,

the plurality of flow channels include:

a first flow channel through which first fluid flows; and

a second flow channel through which second fluid having a temperature different from a temperature of the first fluid flows,

the first flow channel and the second flow channel are provided in such a manner as to be alternately stacked in a stacking direction perpendicular to a direction in which the flow channels extend,

each of the first flow channel and the second flow channel includes:

upstream parts disposed parallel to one another in a direction perpendicular to the stacking direction and to a direction in which the flow channels extend;

downstream parts disposed parallel to one another in a direction perpendicular to the stacking direction and to a direction in which the flow channels extend;

branching parts configured to branch the flow channels immediately upstream of the branching parts into two divergent channels; and

merging parts configured to merge divergent channels adjacent to one another to form next flow channels, between the upstream parts and the downstream parts, wherein

the branching parts and merging parts are provided in a plurality of stages between the upstream parts and the downstream parts,

the second fluid is coolant having a lower temperature than the first fluid, the first fluid is fluid having a higher temperature than the second fluid, and

the divergent channels in the first flow channels are formed more narrowly than the divergent channels in the second flow channels,

wherein the next flow channels between the upstream parts and the downstream parts are linear flow channels, the linear flow channels being provided between an upstream merging part and a downstream branching part in the direction in which the flow channels extend,

wherein the linear flow channels are parallel to the direction in which the flow channels extend, and

wherein a width of the linear flow channels of the first flow channels and a width of the linear flow channels of the second flow channels are the same.

2. The heat exchanger according to claim 1 , wherein

the branching parts and merging parts include:

first branching parts configured to branch N number of flow channels immediately upstream of the branching parts into the two divergent channels for each N number of flow channels, and first merging parts configured to respectively merge the divergent channels adjacent to one another by excluding the two outermost divergent channels, to form a next N+1 number of flow channels, and

second branching parts configured to branch N−1 number of flow channels, out of the N+1 number of flow channels by excluding the two outermost flow channels, immediately upstream of the second branching parts, into the two divergent channels for each N−1 number of flow channels and second merging parts configured to merge the divergent channels adjacent to one another including the two outermost flow channels to form next N number of flow channels, and

the first branching parts and the first merging parts and the second branching parts and the second merging parts are alternately provided in a plurality of stages between the upstream parts and the downstream parts.

3. The heat exchanger according to claim 1 , wherein the two divergent channels being configured to branch in the branching parts or merge in the merging parts are symmetric with respect to a direction in which the flow channels extend, with apexes of branching having an angle of 180 degrees or less.

4. The heat exchanger according to claim 1 , wherein

first plates and second plates are stacked on one another in a part in which heat is exchanged,

the first flow channels are formed as grooves between front faces of the first plates and back faces of the second plates,

the second flow channels are formed as grooves between front faces of the second plates and back faces of the first plates, and

the first plates and the second plates are bonded to each other by diffusion bonding.

5. The heat exchanger according to claim 1 , wherein the second fluid is coolant having a lower temperature than the first fluid, and the first fluid is hydrogen gas having a higher temperature than the second fluid.

6. The heat exchanger according to claim 1 , wherein

the plurality of flow channels include three or more kinds of flow channels including the first flow channel and the second flow channel, and

each of the flow channels are provided in such a manner so as to be stacked in the stacking direction, and each of the flow channels includes an upstream part, a downstream part, a branching part and a merging part.

7. The heat exchanger according to claim 1 , wherein

the two divergent channels that are configured to branch in the branching parts or merge in the merging parts are symmetric with respect to a direction in which the flow channels extend, with apexes of branching having an acute angle.

8. The heat exchanger according to claim 7 , wherein

the branching parts and merging parts include:

first branching parts configured to branch N number of flow channels immediately upstream of the branching parts into the two divergent channels, and first merging parts configured to merge the divergent channels adjacent to one another excluding the two outermost divergent channels to form next N+1 number of flow channels, and

second branching parts configured to branch N−1 number of flow channels, out of the N+1 number of flow channels excluding the two outermost flow channels, immediately upstream of the second branching parts, into the two divergent channels, and second merging parts configured to merge the divergent channels adjacent to one another including the two outermost flow channels to form next N number of flow channels, and

the first branching parts and first merging parts and the second branching parts and second merging parts are alternately provided in a plurality of stages between the upstream parts and the downstream parts.

9. The heat exchanger according to claim 7 , wherein

first plates and second plates are stacked on one another in a part in which heat is exchanged,

the first flow channels are formed as grooves between front faces of the first plates and back faces of the second plates,

the second flow channels are formed as grooves between front faces of the second plates and back faces of the first plates, and

the first plates and the second plates are bonded to each other by diffusion bonding.

10. The heat exchanger according to claim 7 , wherein the second fluid is coolant having a lower temperature than the first fluid, and the first fluid is hydrogen gas having a higher temperature than the second fluid.

11. The heat exchanger according to claim 7 , wherein

the plurality of flow channels include three or more kinds of flow channels including the first flow channel and the second flow channel, and

each of the flow channels are provided in such a manner so as to be stacked in the stacking direction, and each of the flow channels includes the upstream part, the downstream part, and the branching/merging part.