Statistical Approach to Estimate the Temperature in Chimney Roof Penetration

The paper shows how the Design of the Experiments can be used to determine mathematical relations to estimate the maximum temperature reached by flammable materials at chimney-roof penetrations. Heat transfer between chimney and roof is simulated by means of an appropriate two-dimensional numerical model. This approach allows the analysis of a great number of cases that otherwise could not be analyzed experimentally. In particular, an insulated chimney of internal diameter of 200 mm passing through two different roofs representative of a great number of non-ventilated roofs is considered. Chimneys are considered with thicknesses between 20 mm and 120 mm and thermal conductivities of the insulating material between 0.03 W/m K and 0.28 W/m K. Wooden roofs are studied of thicknesses between 80 mm and 360 mm and made up of one insulating layer over one wooden layer and by one insulating layer between two wooden layers. Configurations with the chimney in contact with the roof, or with clearance of up to 120 mm were considered. Exhaust gas temperatures are studied covering all the classes of chimney considered by the European standards (from T80 and T600). The mathematical relations are also translated into tables to make them suitable for end-users. They are an effective tool to support chimney installers and producers for installations in conditions very different from those contemplated in the certification procedure.