Valmet Ab

Mattias Gourdon

Lars Gunnar Olausson

Martin Apel

Krister Pettersson

Anders Åkesjö

Anders ÅKesjÖ

The invention relates to a heat transfer tube () for falling film evaporation having a heating medium surface () to be heated by a heating medium, a falling film surface () 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 at least one weld ridge (WR; WR, WR), said weld ridge having a height (h; h) in the range 0.3 to 5.0 mm, a width (w; w) in the range 0.5-15 mm, and an inclination angle (&#x3b1;; &#x3b1;, &#x3b1;) versus a plane orthogonal to a longitudinal axis (CC) of the heat transfer tube in a range of 0-70 degrees so that each weld ridge is inclined and extends helically 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 and forms well ridge portions on the falling film surface such that the distance along the longitudinal axis of the heat transfer tube between adjacent weld ridge portions is within the range of 0 to 250 mm. The invention also relates to a method for manufacturing said heat transfer tube.

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Gothenburg, Sweden

Mattias Gourdon