Heat exchanger

1. A heat exchanger, comprising:

a plurality of flat tubes stacked in layers, including

each of the plurality of the flat tubes having a pair of tube sheets facing each other and joined together,

the tube sheets have a flat part, a depressed recess part having end portions and extending in a longitudinal direction, and a cylindrical tank protruding from the end portions of the recess part, the tube sheet being one of a first tube sheet and a second tube sheet, the first tube sheet having a first type of tank positioned at each end thereof, the second tube sheet having the first type of tank at one end portion of the recess part and a second type of tank at the other end portion of the recess part,

identifiers provided at each end of the second tube sheet, the identifiers distinguishing the second tube sheet from the first tube sheet when viewed externally of the stacked flat tubes, and

a mark provided at one of the identifiers of the second tube sheet.

2. The heat exchanger of claim 1 , wherein:

the mark is provided at the end of the second tube sheet where the second tank is absent.

3. The heat exchanger of claim 1 , further comprising:

a plurality of types of second tanks distinguishable from type to type based on the identifiers; wherein

the identifiers are assigned to the plurality of types of second tanks, respectively, and the identifiers are differed from type to type in at least one of shape, size, and position thereof.

4. The heat exchanger of 1 , wherein:

each identifier is a projection protruding from each end of the second tube sheet.

5. The heat exchanger of claim 2 , wherein:

each identifier is a projection protruding from each end of the second tube sheet.

6. The heat exchanger of claim 3 , wherein:

each identifier is a projection protruding from each end of the second tube sheet.

7. A heat exchanger, comprising:

a plurality of flat tubes stacked in layers, including

each of the plurality of the flat tubes having a pair of tube sheets facing each other and joined together,

the tube sheets having a flat part, a depressed recess part having end portions and extending in a longitudinal direction, and a cylindrical tank protruding from the end portions of the recess part, the tube sheet being one of a first tube sheet and a second tube sheet, the first tube sheet having a first type of tank positioned at each end thereof, the second tube sheet having a first type of tank at one end portion of the recess part and a second type of tank at the other end portion of the recess part,

identifiers provided at each end of the second tube sheet, the identifiers distinguishing the second tube sheet from the first tube sheet when viewed externally of the stacked flat tubes,

a first mark provided at one of the identifiers of the second tube sheet, and

a second mark provided at the other of the identifiers of the second tube sheet.

8. The heat exchanger of claim 1 , wherein:

the first mark is provided at the end of the second tube sheet where the second tank is absent, and

the second mark is provided at the end of the second tube sheet where the second tank is present.

9. The heat exchanger of claim 1 , wherein:

the identifiers are formed at each end of the second tube sheet.

10. The heat exchanger of claim 1 , wherein:

the first type of the tank at the one end and the second type of the tank at the other end are formed in a same outside shape or in a similar outside shape.

11. The heat exchanger of claim 7 , wherein:

the identifiers are formed at each end of the second tube sheet.

12. The heat exchanger of claim 7 , wherein:

the first type of the tank at the one end and the second type of the tank at the other end are formed in a same outside shape or in a similar outside shape.