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Exhaust gases of diesel vehicles are considered as a major reason of city air pollutions. The DOC(Diesel Oxidation Catalyst) and DPF(Diesel Particulate Filter) have been used to reduce the emissions of diesel vehicles. The DOC can oxides HC, CO and SOF(Soluble Organic Fraction) in the PM emissions, and the DPFs can filter the most of solid PM, such as carbon particles. As the DPFs, wall flow type ceramic honeycomb filters have been commonly used and now being still advanced. However, the cost and durability of the currently used DPFs are not perfect yet. Metal foam is the one of promising materials for the DPFs due to its cost effectiveness, good thermal conductivity and high mechanical strength. The metal foam can be produced with various pore sizes and strut thickness and finally can be coated with catalytic wash-coats with low cost.

The purpose of this research was to investigate the extent to which the thermal conductivity of non-Newtonian fluids is affected by fluid motion under conditions in which it is known that the viscous properties undergo significant changes, and then the effect of these shear rate dependent thermal conductivity measured in Lee [1995], on the heat transfer for a typical convective system. A coaxial cylinder apparatus with a rotating outer cylinder was used for the determination of the thermal conductivity of non-Newtonian liquids in a shear field. A simple parallel plate flow model with temperature independent properties gave increases in heat transfer of the order of 30--80% over the entire temperature range (20°C--50°C) of CMC solutions depending on the inlet average velocity due to the effect of the shear dependent thermal conductivity.

This paper examines the effects of viscous heating in the flow of Newtonian and non-Newtonian fluids. Two system were analyzed theoretically. One uses a Couette Flow model between two infinite parallel plates. The other examines Couette flow between concentric cylinders (infinite in length). It is found that, for the thermal boundary condition of constant wall temperature, the generalized Prandtl number (Prg) is the parameter which indicates whether or not viscous heating effects are important.