Plate heat exchanger

Plate heat exchanger comprising a package of thin heat exchange plates, which have been provided by pressing with ridges on both sides, through which ridges the plates abut against each other while forming plate interspaces, and further comprising means for conducting a heat exchange medium through every second plate interspace and another heat exchange medium through the other plate interspace in a way such that the heat exchange media flow in parallel with each other in a predetermined main direction--countercurrently or concurrently--through their respective plate interspaces, the heat exchange plates being formed such that they provide in the plate interspaces a larger flow resistance for the one heat exchange medium than for the other, characterized in that

• each of at least two adjacent plate interspaces (C, H) in the heat exchanger are formed by heat exchange plates, each of which on each side has parallel ridges (19a;
• 19b) which across a substantial part of the heat exchange portion of the heat exchange plate extend in said main direction for the flow of the heat exchange media and which between themselves form parallel valleys (20a;
• 20b) for the flow of the respective heat exchange medium, the plate portions between the ridges (19a;
• 19b) on one side of the plate forming ridges on the other side of the plate,
• the ridges on opposing sides of adjacent heat exchange plates abut against each other in each of said two plate interspaces (C, H) such that said valleys (20b) between the ridges (19b) of one heat exchange plate (26) are situated opposite to corresponding valleys of the other heat exchange plate (24) and forming therewith parallel flow passages for the respective heat exchange medium,
• at least the heat exchange plate (24) forming a wall of the two said adjacent plate interspaces is provided with depressions (21a) at least in its ridges (19a) situated on one side of the beat exchange plate, which depressions form thresholds in the mutually parallel valleys on the other side of the heat exchange plate, and
• depressions (21a) of the said kind are dimensioned and located such that during operation of the heat exchanger the flow resistance for one heat exchange medium in the flow passages of one (C) of the plate interspaces is substantially larger than the flow resistance for the other heat exchange medium in the flow passages of the adjacent other plate interspace (H).