Abstract: The invention relates to a heat exchanger (1) with plate structure, comprising a stack (6) of plates composed of circular heat transfer plates (10) by welding and fitted inside a housing unit (2) used as a pressure vessel, whose periphery is provided with flow guides (21, 22), by means of which the second heat transfer medium is guided to desired ducts in the stack (6) of plates. By means of spacing plates (32) fixed inside the flow guides (21, 22), it is possible to arranged several draughts for the stream of the heat transfer medium.

Abstract: An apparatus for transferring heating and cooling power by means of two heat transfer media, wherein at least one of the heating media is arranged to be evaporated or condensed. To reduce the need for space, the apparatus includes a shell (3) inside which at least one plate heat exchanger (1,2) is arranged loosely, flow slots (19) of the heat exchanger being arranged to be completely or mainly open towards the shell (3) in such a manner that the evaporating or condensing heat transfer medium can flow to the plate heat exchanger or from the plate heat exchanger from different sides of the plate heat exchanger on the whole length of that slot (19) which is open.

Abstract: A method and apparatus for welding thin sheets (34) and (35) at the periphery of aligned holes therein by melting the sheets together by a rotating electrode (23) in a protective gas atmosphere. The sheets (34) and (35) are pressed together by copper rings (32) and (33) which also function as heat transfer members to conduct the heat away from the welding seam and thus prevent distortion thereat. The electrode (23) is adjusted to the proper vertical position by a guide (9) in a jig (7), and it is locked to the position determined by the sheets (34) and (35) by a clamp (31).