Untersuchungen zur Wärmeleitung von Vollholz und Werkstoffen auf Vollholzbasis, wesentliche Einflussfaktoren

Thermal conductivity from solid wood and solid wood materials, important parameters.

The thermal conductivity was measured on spruce wood, solid wood panels, as well as massive wood walls with a variable structure. In solid wood a slight influence of the growth ring position (radial-tangential) and a considerable influence of the fibre-load-angle (LR, LT) was observed. In contrast to solid wood in radial and tangential direction solid wood panels with an irregular orientation of the growth rings have a lower thermal conductivity. Marginal holes in the middle layer (e.g. slits to reduce strains) cause a decrease of the values. With increasing temperature and moisture content the thermal conductivity has been rising. Multi-layered wood elements of solid wood show an influence of the number of layers, the growth ring position and holes between the layers. The thermal conductivity is reduced by presenting holes in the middle layer. However, this effect reverses if the holes cause convection. The values also increase a little if mechanical bond elements perpendicular to panel pane such as dowels made of hardwood with a high density are used. The determined parameters about the influence of the position of growth rings, the fibre-load-angle, density and moisture content render the possibility to calculate the thermal conductivity of material combinations by using different computer programs.