20.500.12556/RUL-161852 Higroskopnost in difuzija vezane vode v obžganem lesu smreke Hygroscopicity and bound water diffusion in charred spruce wood Raziskali smo strukturne, sorpcijske in difuzijske lastnosti obžganega smrekovega lesa (Picea abies), ki so med drugim pomembne za razumevanje obnašanja konstrukcijskega lesa po požaru in pri njegovi nadaljnji rabi. Vzorce, debeline 35 mm, smo obžigali v konusnem kalorimetru pri konstantnem toplotnemu toku 50 kw/m2, skladno s standardom ISO 5660-1:2015. Higroskopnost in sorpcijske lastnosti obžganih vzorcev smo pri 20 °C v več plasteh po globini (0 mm, 2 mm, 4 mm in 20 mm) določali z dinamično sorpcijo vodne pare (DVS). Difuzivnost vodne pare skozi obžgano površino vzorcev smo določali nestacionarno, z merjenjem polovičnega časa uravnovešanja vzorcev med suho (T = 20 °C, φ = 30 %) in vlažno klimo (T = 20 °C, φ = 75 %). Ugotovili smo valovito površino obžganih vzorcev, s plastjo pooglenelega lesa (⡈ 2–3 mm), ter podpovršinsko plastjo termično modificiranega lesa (⡈ 1 mm). Zunanje plasti obžganih vzorcev so se termično bolj degradirale in so imele na celotnem higroskopskem območju (φ = 0…90 %) nižjo ravnovesno vlažnost. Vlažnost nasičenja primarnih sorpcijskih mest je bila v področju obžgane površine vzorcev (0…4 mm) nižja (u0 = 3,6 %) kot pri kontrolnem lesu (20 mm; u0 = 5,8 %), energija vezave vodnih molekul na primarna sorpcijska mesta pa je bila velika (ΔG1 < –4000 J/mol). Difuzijski koeficient je bil pri obžganih vzorcih, 3-krat manjši (D = 8,33×10–11 m2/s) kot pri kontrolnih vzorcih (D = 2,60×10–10 m2/s). Obžgana površina vzorcev predstavlja težje prehodno plast za difuzijo vezane vode. We investigated the structural, sorption and diffusion properties of charred spruce wood (Picea abies), which are important, among other things, for understanding the post-fire behaviour of structural timber and its further use. The 35 mm thick samples were burnt in a cone calorimeter at a constant heat flux of 50 kW/m2 in accordance with ISO 5660-1:2015. The hygroscopicity and sorption properties of the charred samples were determined by dynamic water vapour sorption (DVS) at 20 °C in several depth layers (0 mm, 2 mm, 4 mm and 20 mm). The diffusivity of water vapour through the charred surface of the samples was determined in a non-stationary manner by measuring the equilibrium half-time of the samples between dry (T = 20 °C, φ = 30 %) and humid climates (T = 20 °C, φ = 75 %). The surface of the charred samples proved to be corrugated, with a layer of charred wood (⡈ 2 to 3 mm) and an underlying layer of thermally modified wood (⡈ 1 mm). The outer layers of the charred samples were more thermally degraded and had a lower equilibrium moisture content over the entire hygroscopic range (φ = 0...90 %). The saturation of the primary sorption sites was lower in the charred area of the samples (0...4 mm; u0 = 3.6 %) than in the control wood (20 mm; u0 = 5.8 %) and the binding energy of the water molecules bound to the primary sorption sites was high (ΔG1 < –4000 J/mol). The diffusion coefficient of the charred samples was three times lower (D = 8.33×10–11 m2/s) than that of the control samples (D = 2.60×10–10 m2/s). The charred surface of the samples represents a diffusion barrier for the transport of bound water. les piroliza sorpcija difuzivnost zoglenela površina wood pyrolysis sorption diffusion charred surface true false false [U. Ribič] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2024-09-15 07:18:02 2024-09-15 07:18:05 2024-09-18 03:21:48 0000-00-00 00:00:00 2024 0 0 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 630*812.141:66.092-97 245386 207590659 DIP_Ribic_Urban_2024.pdf DIP_Ribic_Urban_2024.pdf 1 E7E80A6F84CE49480D068C6968291AE1 2f8d9deaa68e9a550a6a59fc41234b47b8466811a13a51a19654d800980b28a7 ce22dde6-7321-11ef-b232-0050569b8976 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=190838 Biotehniška fakulteta 0 0 0