Core structure of heat exchanger

A core structure of a heat exchanger, the core structure comprising:

• a plurality of tubes through which a heat exchange medium is to flow;
• a plurality of corrugated fins adhering to said tubes to radiate heat from the heat exchange medium through said tubes;
• and
• a plurality of seat plates arranged opposite to each other with a predetermined space interposed therebetween and having said tubes and said corrugated fins arranged alternately therebetween, said seat plates being provided with connection portions having main body portions and wall portions slanted from said main body portions toward said tubes and being formed with tube holes through which said tubes are inserted to be fixed, wherein
• said tubes have a wall thickness of 0.13 mm to 0.23 mm, and
• a slant angle θ between the connection portions and the main body portions of said seat plates satisfies the following relationship:
• the slant angle θ (°)≧25×(a thickness (mm) of said seat plates)+(−125×(the wall thickness (mm) of said tubes)+25).