Heat transfer plate, plate pack and plate heat exchanger

A plate pack comprising

• a plurality of heat transfer plates which each comprise an inlet portion, an outlet portion and a heat transfer portion which is located between the inlet portion and the outlet portion and which presents a number of ridges and troughs pressed into the plate and extending between a geometric top plane and a geometric bottom plane of the plate, said planes being essentially parallel to a geometric central plane of the plate, a fluid being intended to flow in a number of flow areas that are formed by the interspaces between the heat transfer plates constituting the plate pack along a main flow direction which extends between the inlet portion and the outlet portion, wherein
• the heat transfer portion has a plurality of juxtaposed rows of said ridges and troughs, said rows extending in the main flow direction,
• the rows of ridges and troughs are separated from each other in a transverse direction, which is essentially perpendicular to the main flow direction and extends along the central plane of the plate, by essentially plane channel portions of the heat transfer portion, which extend essentially parallel to the central plane of the plate,
• each row presents alternating elongated ridges and elongated troughs which extend in said main flow direction,
• the ridges of two juxtaposed heat transfer plates bear against each other,
• the transition between each ridge and an adjacent trough in the same row is formed by a continuous, essentially straight transition portion of the plate, which is inclined relative to said central plane of the plate and of which a first part forms an end wall of said ridge and a second part forms an end wall of the adjacent trough,
• each channel portion is stepwise divided into a number of essentially plane step portions which are arranged one after the other in the main flow direction and displaced in relation to each other along a normal to the central plane of the plate,
• a main part of the fluid stream flows in the main flow direction in main flow channels which extend along the main flow direction and which are formed by the essentially plane channel portions of two juxtaposed heat transfer plates, and
• a small part of the fluid stream flows in the transverse direction in portions where the troughs of two juxtaposed heat transfer plates form open transverse connections between the main flow channels.