Modeling of Thermophoretic Soot Deposition and Hydrocarbon Condensation in EGR Coolers

EGR coolers are effective to reduce NOx emissions from diesel engines due to lower intake charge temperature. EGR cooler fouling reduces heat transfer capacity of the cooler significantly and increases pressure drop across the cooler. Engine coolant provided at 40 – 90 C is used to cool EGR coolers. The presence of a cold surface in the cooler causes particulate soot deposition and hydrocarbon condensation. The experimental data also indicates that the fouling is mainly caused by soot and hydrocarbons. In this study, a 1-D model is extended to simulate particulate soot and hydrocarbon deposition on a concentric tube EGR cooler with a constant wall temperature. The soot deposition caused by thermophoresis phenomena is taken into account the model. Condensation of a wide range of hydrocarbon molecules are also modeled but the results show condensation of only heavy molecules at coolant temperature. Thermal properties of fouled layer are calculated based on mass fraction of deposited soot and hydrocarbons. The experiments with the same conditions ran to validate the model. Hot EGR gases flow through the inner pipe and the coolant circulates around it in the outer pipe to keep a constant wall temperature. Effectiveness, deposited soot mass, condensed hydrocarbon mass, and pressure drop across the cooler are the parameters that have been compared. The results of the model are in a reasonably good agreement with the experimental results although there are some fields that need to be studied in future to improve the model.