Heat transfer modelling in honeycomb wall-flow diesel particulate filters

Heat transfer in wall-flow monoliths has gained in interest because of the widespread adoption of these systems by automotive industry to fulfil soot emission regulations and the importance of heat exchange on the regeneration process control to avoid damaging the monolith. This paper presents a heat transfer model for wall-flow diesel particulate filters coupled with an unsteady compressible flow solver. The heat exchange between the gas and the solid phase is based on a bi-dimensional discretisation of the porous medium both in axial and tangential directions. The monolith can be discretised in the radial direction to account for the heat fluxes towards the environment through the monolith and the canister, which is also coupled with the inlet and outlet ducts of the filter. The model is validated against experimental data obtained in a flow test rig. A test campaign under non-reacting conditions has been conducted to show the capability for thermal response prediction. Tests cover clean and soot loaded monolith, continuous flow under steady and transient thermal conditions, and pulsating flow. In this case, the characteristics of the pressure waves in amplitude and frequency are similar to those that the monolith can undergo depending on its location along the exhaust line.

► Model for bi-dimensional characterization of wall-flow DPFs heat exchange. ► Expression for effective radial conductivity determination in DPFs with particulate layer in inlet channels. ► DPF heat transfer model coupled with an unsteady compressible flow solver. ► Conduction prevails on convective heat transfer: influence of residence time. ► Increase of heat losses in loaded DPFs and under low amplitude pulsating flow, without influence of pulse frequency.