Subsidiary aspect: “Glimmer of insulation materials made from renewable raw resources”
At the Fraunhofer WKI, we are investigating the subsidiary aspect “Glimmer of insulation materials made from renewable raw resources”. Initially, we will develop a methodology for the systematic investigation of the glimmer behavior and investigate the influence of various parameters on glimmer. On this basis, we will analyze the glimmer process of NawaRo insulation materials and identify material-specific evaluation criteria. Furthermore, we are developing appropriate measures for the suppression of glimmer, in order to increase the usability of NawaRo insulation materials.
The Fraunhofer WKI is accredited as an inspection body for the determination of the glimmer and smolder behavior of thermal insulation materials in accordance with DIN EN 16733. In a previous project, we developed a glimmer test rig (Figure 1) and procedures with which the glimmer behavior of thermal insulation materials can be investigated and evaluated in greater detail. These procedures enable the targeted development of insulation materials and aggregates which influence the glimmer and smolder behavior.
The methodical development of the procedure for the testing of NawaRo insulation materials on the Fraunhofer WKI glimmer test rig (Figure 1) is based on various requirements concerning inspection boundary conditions, measurement technology, practicality and dimensioning.
The selected geometries of the chamber, as well as the positioning and dimensioning of the test specimens, are based on numerical flow simulations performed prior to the work. These should primarily provide a forecast for the turbulence behavior. The qualitative progressions of the air flows in the test chamber are shown in Figure 2.
In order to compare the simulations, these were performed with both COMSOL and FDS with an initial flow velocity in the lower region of the test chamber of 0.4 m/s. The simulations with COMSOL occurred over the course of the planning of the test rig, the FDS simulations following the determination of all the geometries with the actual dimensions. Both simulations exhibit qualitatively comparable results, whereby the significant effects in the lesser flow velocities were present in the edge region, the deflection of the directional vectors in the region of the test specimens and the theoretically smaller amounts of the flows in the lower region of the specimen.
The examined test specimens have an area of 100 mm × 100 mm with variable material thicknesses of between 50 mm and 70 mm. The test specimens are irradiated in the Fraunhofer WKI glimmer test rig using a glow igniter until they start to glimmer. This thereby provides us with the glimmer acceleration as a characteristic material property. Within the framework of this project, the results from the Fraunhofer WKI glimmer test rig are to be compared with the results from the standard testing rig (Figure 3) in order to determine the propensity of a building product to undergo continuous smoldering in accordance with DIN EN 16733.
In an initial step, we conducted a parameter study on wood-fiber insulation materials in the Fraunhofer WKI glimmer test rig in order to determine the influence of the bulk density and the particle size on the glimmer. The results are shown in Figure 4. It thereby emerged that a high bulk density and large particles slow down the glimmer acceleration. We will, step by step, extend the investigations to cover all NawaRo insulation materials.