Comparison of the effect of soot deposition on the flow and thermal characteristics of finned-plate-type and shell-and-tube-type exhaust gas recirculation cooling devices

Experiments were conducted to characterize the effect that diesel soot deposition has on the operational characteristics of a finned-plate-type compact exhaust gas recirculation (EGR) cooling device for Reynolds numbers from approximately 900 to 1200, typical of the values used in EGR applications. The results show that the Colburn j factor did not change significantly during diesel exhaust gas exposure for 5h at the lower Reynolds number, but the j factor and friction factor changed by 30–40 per cent during exposure for 5h at the Reynolds number of 1200. The Colburn j factor and friction factor for the plate-type device changed more slowly than those results for shell-and-tube heat exchangers at Reynolds numbers of 7000–9000, typical of the values used for these devices in EGR applications. Thus, the results show that the finned-plate-type compact heat exchanger operational characteristics should be less affected by soot deposition than the shell-and-tube devices in EGR applications.