Abstract: Disclosed is a heat exchanger, particularly an exhaust gas heat exchanger for an internal combustion engine of a motor vehicle, comprising a housing jacket that is open at both ends, and a tube bundle which is inserted into said housing jacket and is penetrated by the hot exhaust gas. The aim of the invention is to produce said heat exchanger in an inexpensive and functionally safe manner. Said aim is achieved by the fact that only the tube bundle with the tube bottoms thereof, which are located on the front side, are made of metal while the housing jacket into which the tube bundle is inserted along with the tube bottoms is made of plastic.

Abstract: The invention relates to an air-cooled exhaust gas heat exchanger, in particular exhaust gas cooler (1) for motor vehicles comprising channels (exhaust gas channels) which can be cross-flown by the exhaust gas of an internal combustion engine, between which ribs (4) for air cooling are arranged. According to the invention, the exhaust gas channels are embodied as tubes, in particular as flat tubes (3), which form the ribs (4) of a rib tube block (2) and the tube (3) has tube ends (3a) which are received in the collecting vessels (5) for the exhaust gas.

Abstract: Fluid friction clutches tend to operate discontinuously when the performance requirement is low and therefore the filling ratio in the working chamber is also low. This so-called "surging" is to be avoided. According to the invention, a forced guiding is provided for the clutch fluid from a front part of the working chamber into the rear part of the working chamber, and only then is the return flow provided to the storage chamber which is achieved by a sealing-off of the working chamber into these two areas by means of the clutch disk and by means of the arrangement of a fluid deflector with damming bodies at a part of the circumference. The resulting forced distribution of clutch fluid on both sides of the clutch disk permits a smooth operation of the clutch and, when pumping elements are arranged, also a reduction of the hysteresis. Fluid friction clutches of this type are particularly suitable for fan drives for cooling devices of motor vehicles.