Fully Developed Frictional and Heat Transfer Characteristics of Laminar Flow in Wall-Flow Monoliths with Hexagon and Triangular Channels
Wen Wang, Gamma Technologies
In the 1D modeling of flow in the wall flow monolith, it is common to use a friction factor and Nusselt number generated from an idealized 2D/3D solution. The results are usually expressed as a function of wall Reynolds number and Peclet number, and they have been derived for circular tubes and parallel plates decades ago. Recently the 3D solution has been generated for fully developed laminar flow in square channels with porous walls and uniform wall velocity, and the general functions for friction factor and Nusselt number were derived for 1D modeling. In this work we extend the study to the 3D geometry of general polygons, particularly hexagons and triangles since they are commonly used for particulate filters in the exhaust emission community. In the application of particulate filters, asymmetric channel design with higher ash capacity has become an important approach to extend the life of the filters. This includes using different channel shapes or increasing the ratio of inlet to outlet flow areas. For hexagonal channel design, it is common to have two inlet channels per outlet channel. In this work the 3D flow and heat transfer solutions of fully developed flow are generated for hexagonal and triangular channels with asymmetric and symmetric designs. The difference between the asymmetric design and conventional symmetric design is studied and the implication for 1D modeling is discussed.