Page 29 - Methods For Monitoring And Diagnosing The Efficiency Of Catalytic Converters A Patent - oriented Survey

Introduction I1

A typical monolith has square cross section channels with inside dimensions of the order of 1
mm separated by thin (0.1-0.15 mm) porous walls. The number of channels per cm2 varies
between 60 and 100, although even higher cell densities of the order of 200 channels per cm2
have been demonstrated for metallic honeycombs.

At high operation temperatures of the catalytic converter, heat is transferred from the
converter to the environment. This heat loss occurs via convection (fie and forced) and
radiation from the converter shell. For this reason insulation material is inserted between the
substrate and the housing for thermal protection of the environment.

In the case of ceramic monoliths, a resilient mat is also provided between the housing and the
substrate in order to protect the substrate from being damaged from vibrations or shocks (see
e.g. patent disclosures EP0492083 (1992), EP0505720 (1992), DE19509029 (1995)).