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The use of exhaust gas recirculation (EGR) in internal combustion engines has significant impacts on combustion and emissions. EGR can be used to reduce in-cylinder NOx production, reduce emitted particulate matter, and enable advanced forms of combustion. To maximize the benefits of EGR, the exhaust gases are often cooled with on-engine liquid to gas heat exchangers. A common problem with this approach is the build-up of a fouling layer inside the heat exchanger due to thermophoresis and condensation, reducing the effectiveness of the heat exchanger in lowering gas temperatures. Literature has shown the effectiveness to initially drop rapidly and then approach steady state after a variable amount of time. The asymptotic behavior of the effectiveness has not been well explained. A range of theories have been proposed including fouling layer removal, changing fouling layer properties, and cessation of thermophoresis.

Compact heat exchangers have been widely used in various applications in thermal fluid systems including automotive thermal management systems. Radiators for engine cooling systems, evaporators and condensers for HVAC systems, oil coolers, and intercoolers are typical examples of the compact heat exchangers that can be found in ground vehicles. Among the different types of heat exchangers for engine cooling applications, cross flow compact heat exchangers with louvered fins are of special interest because of their higher heat rejection capability with the lower flow resistance. In this study, a predictive numerical model for the cross flow type heat exchanger with louvered fins has been developed based on the thermal resistance concept and the finite difference method in order to provide a design and development tool for the heat exchanger. The model was validated with the experimental data from an engine cooling radiator.

EGR coolers are mainly used on diesel engines to reduce intake charge temperature and thus reduce emissions of NOx and PM. Soot and hydrocarbon deposition in the EGR cooler reduces heat transfer efficiency of the cooler and increases emissions and pressure drop across the cooler. They may also be acidic and corrosive. Fouling has been always treated as an approximate factor in heat exchanger designs and it has not been modeled in detail. The aim of this paper is to look into fouling formation in an EGR cooler of a diesel engine. A 1-D model is developed to predict and calculate EGR cooler fouling amount and distribution across a concentric tube heat exchanger with a constant wall temperature. The model is compared to an experiment that is designed for correlation of the model. Effectiveness, mass deposition, and pressure drop are the parameters that have been compared. The results of the model are in a good agreement with the experimental data.