Three condensation paths of exhaust and its five effects on exhaust gas recirculation (EGR) cooler fouling and thermal performance: A review

Fouling has limited the evolution of compact heat exchangers (represented by EGR cooler) to smaller and more efficient sizes, an important reason is the unclear mechanism of the effect of exhaust gas condensation on fouling and thermal performance. This paper reviews the effects of hydrocarbon vapor, water vapor and acid vapor condensation on EGR cooler fouling and thermal performance from 1998 to 2023. Three paths of vapors condensation can occurr: interaction with particles, homogeneous nucleation and interaction with fouling. Beneficial effect (3) and harmful effects (2) to EGR cooler thermal performance have identified: filling, removal and chemical are beneficial effects whereas adhesion and nucleation are harmful effects. Three pathways and five effects play a key role on the composition, the mass, the thickness, density, the morphology and thermal resistance of fouling layer. The involvement level of sub-paths and contribution degree of sub-effects of vapor condensation under different boundary conditions, standard database, holistic model and the effect of renewable synthetic fuels on fouling and thermal performance can be further explored. The results will help researchers to understand the logical relationship between exhaust vapor condensation and fouling and thermal performance from the new perspective of condensation.