HEAT TRANSFER TUBE AND METHOD FOR MANUFACTURING A HEAT TRANSFER TUBE

The invention relates to a heat transfer tube ( 9) for falling film evaporation having a heating medium surface (21) to be heated by a heating medium， a falling film surface (20) to have spent liquor passing over it， and being made from an iron based high alloy stainless steel material with an alloy content above 16.00% for Chromium and above 1% for Nickel. The falling film surface of the heat transfer tube is equipped with one or several protrusions/indentations forming a multitude of stamped bumps (SB) on the envelope surface of a heat transfer tube such that the distance between adjacent stamped bumps (SB) along a line on the envelope surface parallel to the longitudinal axis of the heat transfer tube is within the range of 3 to 250 mm， said stamped bumps (SB) having a height (hp) in the range 0.3 to 5.0 mm， a width (wp) in the range 1.0-20 mm， and an inclination angle (a) versus a plane orthogonal to a longitudinal axis (CC) of the heat transfer tube in a range of 0-70 degrees so that each stamped bump (SB) is inclined and extends along at least a portion of the heat transfer tube or extend within a plane orthogonal to the longitudinal axis of the heat transfer tube. The invention also relates to a method for manufacturing said heat transfer tube.