Method for manufacturing heat exchangers

A method of manufacturing heat exchangers for counter flow, cross flow or parallel flow, which comprises:

• mutually stacking a plurality of extruded plastic channel plates together with heat-absorbing intermediate spacer members so as to form a first channel system between the channel plates and to form a second channel system consisting of channels in the channel plates, said plates having two outer walls which are mutually connected by parallel intermediate walls to form the second channel system, and wherein the end-edges of the outer walls forming respective channel walls in the first channel system are mutually joined with the aid of heat treatment so as to close the channels of the first channel system at the side edges of said channels, introducing from one of the end sides of the plate pack, where the ends of the second channel system are located, plastic particles into at least one of the spaces defined by the outer surfaces of the outer walls of two mutually adjacent channel plates and intermediate spacer members which are disposed in the proximity of the end-portions of the outer walls, heating said end side with one of radiation heat and thermal convection heat until a given length of the intermediate-wall end-portions has been brought to a given molten state, such that the end-portions of said adjacent outer walls on a respective channel plate are caused to bend away from one another as a result of heat-engendered changes in the stresses in the plastic material and the heat-absorbing intermediate spacer members, and the essentially semi-molten end-portions with the plastic particles introduced therebetween are formed to an integrated unity and essentially integrated with the outwardly bent end-portions of the outer walls of adjacent channel plates and with the plastic particles, and removing the intermediate spacer members.