An apparatus and a method for manufacturing a needle-rib heat-exchanger construction including a band which is wound around a tube is described. Initially, cuts are formed on both sides of an elongate band and thereafter the band is passed through a series of engaging former wheels. A bottom part is formed into the band and top portions of the band are folded onto the bottom part. Needle-shaped ribs are formed to project from the top portions and are placed at an angle in relation to one another. The band with needle-shaped ribs is then mounted on the tube.