Patent ID: 6926075

Claim:
A plate type heat exchanger comprising a plurality of plates alternately turned and stacked on one another, the plates commonly facing the direction of stacking, each of said plates having: a seal portion, which is provided on an outer peripheral portion of the plate and with an interior of which inflow and outflow ports of heat exchanging fluids are communicated; and heat-transfer surface elements formed in a mountain-shaped manner in a thicknesswise direction of the plate and arranged to form flow passages within the seal portion, wherein the heat-transfer surface elements are in the form of a quadrangular pyramid having flat top, and the seal portion having flat portions on outer peripheral portions of the flow passages to define a bottom surface, and mountain portions, which extend upright from the flat portions and of which tops are formed to be flat in shape, and wherein the flat portions and the mountain portions on the seal portion are arranged alternately in a flow direction of the flow passages.