Exhaust-gas cooling device for an internal combustion engine

A method for cleaning a U-shaped heat exchange unit of an exhaust-gas recirculation system, wherein the method comprises the steps of:

• in the cleaning mode, connecting a return flow path to an exhaust-gas inlet of the U-shaped heat exchange unit so that a flow direction of exhaust gas through the U-shaped heat exchange unit is reversed;
• and
• subjecting the return flow path of the U-shaped heat exchange unit to hot exhaust gas due to reversal of the flow direction of the exhaust gas through the U-shaped heat exchange unit, wherein a valve device is used to connect the return flow path to the exhaust gas inlet in the cleaning mode, wherein the valve device comprises a centrically supported flap valve that, depending on a position of the flap valve, connects the exhaust-gas inlet to an outbound flow path or to the return flow path of the U-shaped heat exchange unit, wherein the valve device is arranged in a housing that includes a first chamber, a second chamber and a third chamber, wherein the first chamber provides a first fluid connection between the exhaust-gas inlet and the second chamber, and the third chamber provides a second fluid connection between the second chamber and an exhaust-gas outlet, and the valve device is arranged in the second chamber so that the second chamber is divided into at least two partial chambers, wherein a first partial chamber of the at least two partial chambers is arranged in fluid connection with the outbound flow path, and a second partial chamber of the at least two partial chambers is arranged in fluid connection with the return flow path, wherein the flap valve comprises a flap that is operatively connected to move on semi-circular surfaces that extend into the second chamber, wherein the flap includes a bypass channel formed therein, wherein in the cleaning mode the flap is arranged on the semi-circular surfaces so that hot exhaust gas enters the first chamber via the exhaust-gas inlet and without entering the bypass channel, and the hot exhaust gas is then guided via the second partial chamber into the outbound flow path so that a plurality of ribs of the U-shaped heat exchange unit are cleaned.