Patent ID: 6854511

Claim:
A heat exchanger, comprising: a hollow header; and a plurality of heat exchanging tubes connected to said hollow header, wherein said hollow header includes an inner peripheral wall portion having a generally flattened arc-shaped cross-sectional shape to which said tubes are connected, an outer peripheral wall portion having a generally semi-circular cross-sectional shape which faces to said inner peripheral wall portion and connecting curved peripheral wall portions connecting said inner peripheral wall portion and said outer peripheral wall portion, and wherein said hollow header fulfills all of the following conditions A to E: condition A: r=5-15 mm; condition B: Ra≧6r; condition C: Rb≧4 mm; condition D: h=4-6 mm; and condition E: T=0.1r-0.2r, where “Ra” is a radius of curvature of an external surface of said inner peripheral wall portion, “Rb” is a radius of curvature of an external surface of said connecting curved peripheral wall portion, “r” is a radius of curvature of an external surface of said outer peripheral wall portion, “h” is a perpendicular line length from a circular center of said outer peripheral wall portion to an external surface of said inner peripheral wall portion and “T” is a thickness of a peripheral wall of said header.