In the preceding paper the specific heat capacity, substrate heat capacity, and energy requirements of two types of substrates were discussed in detail both from the standpoint of predictions from measured material property values as well as actual energy measurements on ceramic and metal products. This information is valuable for the catalyst designer because of the light-off impact of this energy requirement. Some material was also presented regarding the change in this energy requirement with washcoat loading.
Other aspects of the substrate which could reasonably come into play to enhance the light-off characteristics of a catalyst are the rates of heat and mass transfer. The latter of these could reasonably be expected to drive the catalyst activity. In addition, the pressure drop which results from the substrate structure could influence and limit the choice of cell configurations and product shapes and sizes, thereby constraining the list of possible options.
These three features - heat transfer, mass transfer, and pressure drop - can all be dealt with by considering the shape of the cell and its impact on the relevant parameters. As with the previous paper, these features will be discussed against the backdrop of the square and sinusoidal cell structures which are available on the market today.