The Effect of Complex Geometries on Exhaust Gas Recirculation Cooler Fouling*

Exhaust gas recirculation (EGR), which re-introduces a portion of the exhaust back into the engine cylinders after it is cooled in a heat exchanger, is a common method to reduce NOx generation during diesel combustion. Due to the high particle and hydrocarbon concentrations in exhaust, these coolers experience rapid drops in effectiveness due to fouling. To mitigate this and enhance heat transfer, some production EGR coolers utilize sinusoidal fin geometries. The complex flow structures and non-uniform heat transfer the fins generate lead to large variations in the fouling layer thickness along the length and width of each sinusoidal period. To examine why these variations occur, the fluid flow and heat transfer along a single channel of the cooler were simulated using the finite volume methods provided in OpenFOAM, an open source CFD software. Comparing these results with thickness measurements obtained from 20 experimentally fouled coolers provided significant insight into the physical mechanisms driving the spatial variations in the fouling layer. These insights will aid in the development of more fouling resistant coolers in the future.