Improved Characterization of Fouling in Cooled EGR Systems

An investigation was performed to characterize the effect of soot deposition on the performance of EGR coolers. The main objective was to determine the magnitude of the thermal resistance associated to the fouling on heat exchange surfaces. So far, values coming from literature have been used and generalized for all the heat exchanger technologies, sizes and operation conditions. What is more, normally the effect of fouling has been evaluated directly in the thermal efficiency or overall thermal resistance as a percentage factor. The study has enabled to establish a range of thermal resistance for each heat exchanger technology in a given operation condition. It has been proved that the proper way to consider fouling is to include this thermal resistance in the dimensioning tool for EGR coolers. Though the tests performed do not intend to be comparative with general durability, they help to understand the effect on different technologies and sizes. The study has been focused on a stationary condition, however the comparison when adding in a cyclic way other operation conditions has been also considered. Finally, it has been also intended to implement de-fouling strategies to recover partially the loss in thermal efficiency.