Stacked heat exchanger and use of same

Heat exchanger in layered design with multiple, fluidically parallel first layers (1a,1b...) that define first heat exchanger channels (5) through which a first medium can flow, and a respective second layer (2a,2b,...) between two first layers, wherein the respective second layer is in thermal contact with the two adjacent first layers and defines at least one second heat exchanger channel (14a,14b) through which a second medium can flow in parallel. The respective second layer (2a,2b) comprises two fluidically parallel layer sheets (9a,9b), and means are provided for controllably supplying the second medium to one and/or the other layer sheet (9a,9b). Such a heat exchanger can be used in particular as an evaporator with integrated start and main evaporator section.