Patent ID: 6948557

Claim:
An inner fin for a heat exchanger flat tube, the inner fin comprising a metal plate having a corrugated cross section, the inner fin being enclosed in the flat tube, ridges and furrows of the inner fin being joinable to an inner surface of the flat tube by brazing, at least one of the ridges and the furrows being provided with a turbulence promoting protrusion facing toward a side opposite to a side to be brazed, the turbulence promoting protrusion being so sized that a clearance to be created between a caved portion formed on a rear side of the turbulence promoting protrusion and the inner surface of the flat tube can be filled with a brazing material, and the turbulence promoting protrusion having a dimension of 1 to 1.5 mm longitudinally of the inner fin and a height of 0.2 to 0.4 mm.