Plate heat exchanger

In a plate heat exchanger, the combination of an assembly of heat exchange plates disposed in substantially parallel relation to form a series of interspaces, one said interspace being provided between each pair of adjacent plates, gasket means sealing off each second plate interspace from the surrounding atmosphere along the periphery of the adjacent plates forming said second interspace, and permanent joints sealing off the other interspaces from the surrounding atmosphere and located between the adjacent plates forming said other interspaces, each plate having a heat exchanging surface and pressed corrugations in said surface, the plates also having pressed grooves around said surfaces for receiving said gasket means, the plates being provided with inlet and outlet ports for two heat exchanging media, said permanent joints being formed along abutting bottoms, of said pressed grooves of the respective adjacent plates, the seals formed by the permanent joints and the seals formed by the gasket means being disposed in substantially aligned relation across the plate heat exchanger, the bottom of the gasket groove of each plate having a narrow flat central portion along which the permanent joint is formed, the groove also having two lateral portions forming an obtuse angle both with said central part and with the respective side walls of the groove.