CFD study of the fouling layer evolution due to soot deposition and hydrocarbon condensation inside an exhaust gas recirculation cooler

Abstract

The fouling deposits that appear in the gas-side of the exhaust gas recirculation (EGR) coolers are commonly made up of soot particles and hydrocarbons condensate. The buildup of this less thermally conductive material causes the degradation of the performance of the cooler, even clogging the tubes after only few hours of work. The present study examines the hydrocarbon condensation coupled with particle matter deposition on the heat exchanger surfaces of a test probe using computational fluid dynamics simulations. The proposed methodology considers the physicalchemical characteristics of hydrocarbon species and takes into account the deposition and removal mechanisms to compute the fouling accumulation and the condensate flux that appear on the upper surface of the deposit. The fouling process has been simulated during five hours taking into account the hydrocarbon species dodecane (C12H26), pentadecane (C15H32), hexadecane (C16H34) and eicosane (C20H42). The growth of the fouling deposit has been computed and the areas where hydrocarbon condensation takes places have been detected. The evolution of the condensation process has been monitored and the total amount of hydrocarbon has been estimated. Results show that, as fouling layer grows, hydrocarbon condensation is reduced due to the increase of the temperature of the deposit. For the selected boundary conditions, dodecane condensation does not take place at any moment of the test, while C15, C16 and C20 condenses mainly in the area located at the end of the test section, where the temperature of the deposit is lower. Eicosane has produced the highest amount of condensate and, at second hour of test, 68.7% of the area of the probe is exposed to eicosane condensation.