A heat exchanger having a first section, through which a first medium can flow, and a second section, through which a second medium can flow. During operation a heat exchange takes place between the first and the second medium. The first section has an inlet chamber and first tubes connected to the inlet chamber, and an outlet chamber and second tubes connected to the outlet chamber. The first tubes are each closed at the ends facing away from the inlet chamber and each second tube is at least partly arranged inside one of the first tubes, and the end of the second tube that faces away from the outlet chamber is open to the interior of the respective first tube. The second section has an inlet means and an outlet means.