Deposition of Nanosized Soot Particles in Various EGR Coolers Under Thermophoretic and Isothermal Conditions

Abstract

This study investigates the performance of various types of exhaust gas recirculation (EGR) coolers, that is, smooth tube, corrugated tube, and plate–fin, when subjected to particulate fouling by soot particles. Experiments were carried out for different temperature gradients of 170 and 320°C (thermophoretic) and 0°C (isothermal). Soot particles with an average diameter of 130 nm were produced by a soot generator. Experimental results showed that generally soot deposition under isothermal conditions is negligible compared to thermophoresis for any given cooler geometry, but is not universal. It may become appreciable when complex coolers with extended surfaces, that is, plate–fin type, are used due to impaction and settlement of soot particles onto the extended surfaces, which act as barrier to the flow. Contrariwise, under thermophoretic conditions, the plate–fin cooler performed best, followed by the corrugated tube and smooth tube cooler. Coolers with larger heat transfer surface area are also found to be less sensitive to the loss in effectiveness, but show a higher pressure drop.