Heat exchanger having wave fin plate for reducing EGR gas pressure difference

1. A heat exchanger comprising:

a heat exchanger body; a gas inlet for introducing exhaust gas into the heat exchanger body; a coolant inlet for introducing a coolant into the heat exchanger body; a gas outlet for discharging the exhaust gas that is cooled by heat exchange with the coolant; and a coolant outlet for discharging the coolant that completes heat exchange with the exhaust gas,

wherein the heat exchanger body comprises:

a laminated tube core formed by laminating a plurality of gas channels side by side;

a housing formed so as to enclose the laminated tube core except for opposite ends thereof; and

a wave fin plate integrally provided with a plurality of wave fins and arranged within each of the gas channels, the wave fins having a wave fin of a ∪-shaped cross-section and a wave fin of a ∩-shaped cross-section that are arranged in series along a width direction of the wave fin plate,

wherein each of the wave fins includes a fixed pitch section adjacent to a position of the gas inlet, and a variable pitch section adjacent to a position of the gas outlet along a longitudinal direction of the wave fin, each of pitches within the variable pitch section of the wave fin being always greater than each of pitches within the fixed pitch section of the wave fin, and the variable pitch section occupying 10 to 60% of a total length of the wave fin plate.

2. The heat exchanger of claim 1 , wherein in each of the wave fins, a first pitch of the variable pitch section is 1.1 to 2.5 times greater than a fixed pitch of the fixed pitch section.

3. The heat exchanger of claim 2 , wherein the variable pitch section includes a plurality of sections in which a pitch gradually increases by 1.2 to 1.8 times greater than a pitch of a preceding section.

4. The heat exchanger of claim 2 , wherein the pitch of the variable pitch section of the wave fin is configured to gradually increase as the pitch of the variable pitch section approaches a position of the gas outlet.

5. The heat exchanger of claim 2 , wherein the pitches of the variable pitch section of the wave fin are configured to be same each other.

6. The heat exchanger of claim 1 , wherein the pitch of the variable pitch section of the wave fin is configured to gradually decrease as the pitch of the variable pitch section approaches a position of the gas outlet.

7. The heat exchanger of claim 1 , wherein the wave fin comprises: a first waveform part, and a second waveform part positioned to follow the first waveform part in series such that the second waveform part defines a predetermined pitch between the first waveform part and the second waveform part, the first waveform part having a first curvature radius, and the second waveform part having a second curvature radius 1.5 to 3 times greater than the first curvature radius.

8. The heat exchanger of claim 1 , wherein each of the wave fins is configured to have a predetermined height of 4 to 8 mm.

9. The heat exchanger of claim 1 , wherein each of the wave fins is configured to be within 3 to 8 mm in all of the pitches.

10. The heat exchanger of claim 1 , wherein the wave fin plate is formed of a metal plate by forming selected from press forming, gear forming, and a combination thereof, and is integrally joined to the laminated tube core therein by joining selected from welding, soldering, adhesion, and a combination thereof.

11. The heat exchanger of claim 10 , wherein the metal plate forming the wave fin plate is made of an austenitic stainless steel of any one selected from SUS 304, SUS 304L, SUS 316, and SUS 316L, and has a thickness of 0.05 to 0.3 mm.