A heat exchanger unit that includes a plurality of first heat exchanger ducts formed by a plurality of plates configured for a first flow of a coolant, a plurality of second heat exchanger ducts formed by the plurality of plates configured for a second flow to be cooled by the first flow, a first inlet for the first flow, a first outlet for the first flow, a first inlet for the second flow, and a second outlet for the second flow. The heat exchanger unit further includes an inlet chamber for the first flow from which a partial flow of the first flow is branched off, conducted through the plurality of first heat exchanger ducts and circulated within the heat exchanger unit to the first outlet.