The aim of the project is to develop fouling- and corrosion-reducing, long-term resistant, non-toxic coatings with which the relevant inner surfaces of fully assembled heat exchangers can be coated irrespective of the surface. At Fraunhofer FEP, a test setup for parylene coating is to be realized as part of the project, which will allow components of heat exchangers or even the inner surfaces of completely assembled heat exchangers to be coated. The coatings exhibit good thermal and very high chemical stability. By introducing the layer-forming monomers into the circuits of the heat exchangers, even complicated component geometries can be coated. In this context, simulations of the gas flows are carried out to ensure the optimum process pressures and residence times of the monomers required during coating.