Quality steel aluminum composite finned tube finned ratio (by the finned tube surface area and bare tube area ratio) and the fitting rate (88% national standards for qualified) as the main criterion. Joint rate refers to the fin and the base gap exists between the heat transfer coefficient of the tube, the thermal contact resistance and contact resistance of the gapless for heat transfer coefficient when the ratio of. Steel aluminum composite finned tube finned ratio in the range of 13.5-22.7, and can meet the need of various process conditions. Fitting rate of more than 90%, to ensure the long-term tube operating ambient temperature 210 degrees below the long-term use of the heat exchange efficiency without attenuation.