Chimney in wood-frame houses: preliminary thermal analysis in relation to the fire hazard

This work is a preliminary numerical study performed with the CFD code FLUENT about some critical aspects occurring when a chimney is installed through wood roof-packages of great thickness. The UNI EN 1443 standard [1] imposes the conditions that a chimney must comply to be certified and the UNI EN ISO 1859 standard [2] describes how the prescribed tests have to be performed: in particular it prescribes the thickness of the floors as 13.2 cm and 23.2 cm. Since real wood roof-packages are characterized by greater thicknesses, up to almost 40 cm, the test configuration is very different from these real situations. This paper illustrates some 3D and 2D axisymmetric simulations on two certified elements, indicated as chimney A (T600-N1-G20) and chimney B (T400-N1-G00). The 2D axisymmetric simulations are performed with different internal diameter, different floor thicknesses and different smoke temperatures. The results lead to interesting considerations concerning the problem of chimneys installed through roof-packages of great thickness and concerning the thermal performance test.