A device having a heat exchanger includes a housing having an inlet and an outlet for a fluid and an inner tube having a first end face extending in axial direction, an opposite second end face and a circumferential surface having openings. A plurality of heat exchanger tubes is disposed parallel to the axial direction on the outside of the circumferential surface. The housing encloses the heat exchanger tubes and the inner tube and the inlet is fluidically connected to the first end face. Guide elements are disposed between the heat exchanger tubes so that the fluid entering the inner tube through the first end face flows out across the heat exchanger tubes in radial direction starting from the inner tube. The device is used particularly for constructing a thermoelectric generator for positioning in the underbody of a motor vehicle. A motor vehicle having the device is also provided.