bottom side the thermomechanical decoupling can be achieved in that side plates 130 132 between the two high temperature stages 102 and low temperature stages 104 also experience a type of abrupt change in stiffness or strength this is realized with a kind of perforation in fig1 another way of realizing the thermomechanical decoupling in the area of side plates 130 132 is shown in fig4 in this case the two high temperature and low temperature stages 102 104 have separate side plates 130 132 for sealing on the charge air side an overlapping plate 408 is used in the intermediate region however it is attached or soldered only at one of side plates 132 here from low temperature stage 104 this achieves that overlapping plate 408 can slide along the underlying side plate 130 which is not soldered because of the different thermal expansions of the two coolant stages 102 104 and thereby can carry out its function of sealing on the charge air side in the area of corrugated fin 402 406 as well there is the possibility of implementing a type of thermomechanical decoupling basically corrugated fins 402 406 can be made separately for both high temperature 102 and low temperature 104 stages so that the corrugated fins extend only in the area of high temperature 400 and low temperature 404 tubes if the intention is to bridge the intermediate region with corrugated fins 402 406 the spacing of corrugated.