An evaporator for evaporating a liquid, in particular for a waste heat utilisation device of an internal combustion engine, - with multiple channel plate arrangements, which are stacked in a stacking direction, wherein in each case between two adjacent channel plate arrangements a gas path is formed, through which a gas can be conducted, via which the heat required for evaporating the liquid can be supplied, - wherein each channel plate arrangement contains a liquid inlet, a vapour outlet and a channel connecting the liquid inlet to the vapour outlet, which forms a repeatedly diverted evaporation path for the liquid to be evaporated, - wherein the respective channel plate arrangement comprises two plates (20, 21), wherein the respective channel is formed through stampings, which are either formed in only one of the two plates (20, 21) or in both plates (20, 21) mirror-symmetrically, - wherein two lateral boundary walls (27, 28) are provided, which limit the gas paths on sides located opposite one another in each case from a gas inlet as far as to a gas outlet, - wherein the boundary walls (27, 28) are each formed through multiple wall elements, each of which laterally limit only one of the gas paths, - wherein the wall elements are attached either to both channel plate arrangements limiting this gas path or in each case are integrally formed on one of the plates (20, 21) of a channel plate arrangement limiting this gas path and are attached to the channel plate arrangement which is adjacent thereto, characterized in - that the respective channel comprises at least in one evaporation zone of the evaporation path a cross section through which a flow can flow which increases in the flow direction of the evaporating liquid, - that the one boundary wall comprises inlet openings, which in each case are fluidically connected to a liquid inlet of one of the channel plate arrangements, - in that the one or the other boundary wall comprises outlet openings, each of which is fluidically connected to a vapour outlet of one of the channel plate arrangements. - with multiple channel plate arrangements, which are stacked in a stacking direction, wherein in each case between two adjacent channel plate arrangements a gas path is formed, through which a gas can be conducted, via which the heat required for evaporating the liquid can be supplied, - wherein each channel plate arrangement contains a liquid inlet, a vapour outlet and a channel connecting the liquid inlet to the vapour outlet, which forms a repeatedly diverted evaporation path for the liquid to be evaporated, - wherein the respective channel plate arrangement comprises two plates (20, 21), wherein the respective channel is formed through stampings, which are either formed in only one of the two plates (20, 21) or in both plates (20, 21) mirror-symmetrically, - wherein two lateral boundary walls (27, 28) are provided, which limit the gas paths on sides located opposite one another in each case from a gas inlet as far as to a gas outlet, - wherein the boundary walls (27, 28) are each formed through multiple wall elements, each of which laterally limit only one of the gas paths, - wherein the wall elements are attached either to both channel plate arrangements limiting this gas path or in each case are integrally formed on one of the plates (20, 21) of a channel plate arrangement limiting this gas path and are attached to the channel plate arrangement which is adjacent thereto, - that the respective channel comprises at least in one evaporation zone of the evaporation path a cross section through which a flow can flow which increases in the flow direction of the evaporating liquid, - that the one boundary wall comprises inlet openings, which in each case are fluidically connected to a liquid inlet of one of the channel plate arrangements, - in that the one or the other boundary wall comprises outlet openings, each of which is fluidically connected to a vapour outlet of one of the channel plate arrangements.