Abstract: The invention relates to a device for multi-stage heat exchange and to a method for producing one such device, whereby at least three free-flowing media (fluids) are used in three flow devices subdivided into at least two heat-exchanging or flow modules. Said modules respectively consist of at least two flow elements that are arranged in such a way that different fluids alternately flow through the same. For essentially liquid fluids, the fluids are distributed to the flow elements by means of fluid collecting devices or fluid distributing devices connected in a gas-tight and liquid-tight manner. The main flow directions of all fluids in the flow elements are in essentially parallel planes. At least two flow modules are directly mounted in series and/or by means of fluid distributing devices in a flow-connected manner at least in relation to one flow device.

Abstract: A heat exchanger, in particular an exhaust gas heat exchanger for motor vehicles, has a bundle of tubes through which hot gas flows, a pair of header plates and a housing jacket, which holds the bundle of tubes and the header plates and through which a liquid cooling medium flows. The header plates have openings (8) for receiving tube ends (3a) which are welded to the header plates (2), which are in turn welded to the housing jacket. The header plates (2, 7) are constructed from a plurality of layers of metal sheets which are layered one above another and are fixedly connected together.