placed on housing 2 the design of rib elements 7 may also be oriented in particular to the specific stresses occurring at diffuser 1 an orientation of rib elements 7 that deviates from the design illustrated in fig1 may therefore also be provided a fluid connection 8 is shown in the left area of fig1 this connection forms the fluid outlet of diffuser 1 the more exact structure of fluid connection 8 is explained in fig2 below fig2 shows a sectional view of diffuser 1 in fig1 in fig2 a detail of an exhaust gas heat exchanger 15 is illustrated as a whole which comprises a housing 2 and diffuser 1 manufactured from plastic a flow channel 11 is formed within housing 2 through which a coolant advantageously flows a tube sheet 10 is disposed between flow channel 11 and diffuser 1 tubes may be inserted into this tube sheet 10 which are however not illustrated for reasons of clarity tube sheet 10 creates a fluid tight separation between flow channel 11 and the interior of diffuser 1 as a result no fluid communication exists between the interior of diffuser 1 and flow channel 11 the interior of diffuser 1 is in fluid communication with the inner area of the tubes which are not illustrated the tubes form the first flow channel through which an exhaust gas advantageously flows a coolant advantageously flows through flow channel 11 forming the second flow channel for this purpose housing 2 has a fluid connection 13 via which a coolant may be introduced into housing 2 the.