US Patent 10254053 Heat transfer fin and heat exchanger using thereof

A heat transfer fin (31) made of stainless steel-based metal for a heat exchanger, has a plurality of upper stage heat-transfer-tube insertion holes (611), a plurality of lower stage heat-transfer-tube insertion holes formed (612), upper end cut portions (651) formed between the adjacent upper stage heat-transfer-tube insertion holes (611), and lower end cut portions (652) formed between the adjacent lower stage heat-transfer-tube insertion holes (612), wherein the upper end cut portions (651) are formed so as to extend from a fin upper end portion (311) beyond lower ends of the upper stage heat-transfer-tube insertion holes (611) to positions in the vicinity of upper ends of the lower stage heat-transfer-tube insertion holes (612), and the lower end cut portions (652) are formed so as to extend from a fin lower end portion (312) to positions above the lower ends of the lower stage heat-transfer-tube insertion holes (612).