Importance

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Abstract

An exhaust gas heat exchanger system of a combustion engine has a bypass duct and a heat exchanger duct with a heat exchanger. A valve is controlled by determining when heat is to be transferred from exhaust gas flowing through the exhaust system to the heat exchanger. When heat is to be transferred, the valve is switched into a first position in which all of the exhaust gas flows through the heat exchanger duct. A pressure drop across the heat exchanger system is monitored either directly or indirectly. If the pressure drop reaches a predefined limit, the valve is switched into an intermediate position, resulting in a smaller portion of the exhaust gas flowing through the heat exchanger duct than when the valve is in the first position and a remaining portion flowing through the bypass duct, thereby reducing the pressure drop across the heat exchanger system. If the pressure drop again reaches a predefined limit, the valve is switched into a second position, resulting in an even smaller portion of the exhaust gas flowing through the heat exchanger duct, thereby further reducing the pressure drop across the heat exchanger system.

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First Claim