WOOD RESEARCH Volume 69, Number 2, 2024
JURAJ KOPÚNEK, JOZEF MARTINKA, PETER RANTUCH, TOMÁŠ ŠTEFKO, IGOR WACHTER, and FILIP MARTINKA

PRELIMINARY STUDY OF DEPENDENCE OF SMOKE AND CARBON MONOXIDE EMISSION ON HEAT RELEASE RATE FROM FAST-GROWING WOOD SPECIES

The aim of this paper is to create the model for prediction of carbon monoxide release rate (CORR) and smoke production rate (SPR) from heat release rate (HRR) of fast-growing wood species. The model is independent on wood species, thus is suitable for all fast-growing wood species. Three wood species hybrid poplar J-105 (Populus nigra × P. maximowiczii A. Henry), white willow (Salix alba L.) and black locust (Robinia pseudoacacia L.) were used for universal model creation. The heat release rate, smoke production rate and carbon monoxide release rate have been measured at three heat fluxes (25, 35 and 50 kW.m-2) by the cone calorimeter. The average values of CORR and SPR for all investigated wood species were 0.051 g.m-2.s-1 and 0.086 m2.m-2.s-1, respectively. Both dependencies of SPR and CORR on HRR have shown similar trends during the ignition phase (unstable trend) and during the intense burning phase (roughly linear increasing with HRR). The main difference was shown during the steady state phase (dependency of SPR on HRR is stable while dependency of CO on HRR is highly unstable). The results also proved a significant impact of wood density on these dependencies, thus, the neural network for prediction of SPR, CORR from HRR was applied. The coefficients of determination R2 for trained neural networks, for both SPR and CORR, were achieved in the range from 0.96 to 0.97

WOOD RESEARCH Volume 68, Number 4, 2023
IGOR WACHTER, TOMÁŠ ŠTEFKO, JOZEF MARTINKA, Peter Ďuriš, PETER RANTUCH, and Zuzana Mária Buchtová

Optical Properties of Transparent Wood prepared from Balsa

In this study, transparent wood was prepared by deactivating chromophore groups in raw balsa wood, followed by solvent free dehydration and a subsequent vacuum-assisted polymer infiltration. Thermal degradation of transparent wood takes place in two main steps. Optical properties (colorimetry, transmittance) of transparent wood made from balsa wood and acrylic polymers were studied. Highest values of transmittance in the visible part of spectra were achieved by 0.7 mm thick samples at approx. 77%. The dependence of thickness on transmittance showed a linear decrease with increasing thickness of transparent wood. The created material also exhibits absorbing properties in visible and UV spectra.

WOOD RESEARCH Volume 68, Number 3, 2023
PETER RANTUCH, JOZEF MARTINKA, TOMÁŠ ŠTEFKO, IGOR WACHTER, and Mária Zuzana Bednáriková

Characterization of the Burning of Oriented Strand Boards Exposed to Flame

Since the methods based on the interaction of a relatively low intensity flame on the lignocellulose sample surface often do not allow measuring the heat release rate (HRR), a procedure using oxygen consumption calorimetry was proposed. The method was applied to OSB samples with dimensions of 320 mm x 140 mm x 25 mm placed in a vertical position. During the measurement, in addition to the HRR, the production of smoke, which was significant after stopping the burner, was also monitored. The average net value of HRR at burner outputs of 3 kW, 4 kW and 5 kW was 2.339 kW and the smoke specific extinction area was in the range of 10.88 m2.kg-1 and 13.19 m2.kg-1.

WOOD RESEARCH Volume 66, Number 5, 2021
Aleš Nečas, JOZEF MARTINKA, PETER RANTUCH, IGOR WACHTER, and TOMÁŠ ŠTEFKO

Impact of the electric cables installation on the ignition parameters of the spruce wood surface

This study is aimed to investigate of an impact of electrical cables installed on Norway spruce (Picea abies (L.) Karst.) wood board surface on main ignition parameters (mainly critical heat flux, ignition temperature, thermal response parameter and thermal inertia). Ignition parameters have been determined by dependence of ignition times (raised to the power of -1, -1/2 and -0.547) on heat flux. Initiation times have been measured for three configurations of spruce wood boards with surface dimensions of 100 x 100 mm ± 1 mm (the first configuration: board without cables on surface, the second configuration: board with three electrical cables on surface – spacing between cables was equal to their diameter and the third configuration: board with five electrical cables – spacing between cables was equal to their diameter) at five heat fluxes (30, 35, 40, 45 and 50 kW·m-2). Obtained results proved that installation of the electrical cables on the spruce wood board surface has a significant impact on the ignition parameters. The critical heat flux (8.5 kW·m-2), apparent thermal inertia 0.20 ± 0.02 kJ2·m-4·K-2·s-1 and ignition temperature 324 ± 105°C of spruce wood board increased up to 18 ± 3 kW·m-2 (critical heat flux), 0.68 ± 0.03 kJ2·m-4·K-2·s-1 (apparent thermal inertia) and 475 ± 27°C (ignition temperature) by the installation of electrical cables on the surface of spruce wood board.

WOOD RESEARCH Volume 65, Number 2, 2020
JOZEF MARTINKA, TOMÁŠ ŠTEFKO, IGOR WACHTER, and PETER RANTUCH

Impact of electrical cables embedded into oriented strand board on critical heat flux

The paper deals with the research of electrical cables embedded in surface grooves of OSBs and its impact on the critical heat flux. An OSB type 3 board (structural board for use in dry or humid environments) and an electrical cable with fire reaction class B2ca have been investigated. Four different configurations of grooves were investigated. The first configuration consisted of an OSB without grooves (control sample). The second configuration consisted of an OSB with a single groove in the centre in which the electrical cable was mounted. In the third and fourth configurations, there were three and five grooves, respectively in which the electrical cables were mounted (the width of the grooves and the spacing between them was 9 mm). The critical heat flux was calculated from the ignition times at five different heat fluxes (30, 35, 40, 45 and 50 kW.m-2) by using a cone calorimeter. The obtained data showed that the OSB without grooves (first configuration) shows the lowest critical heat flux (8.6 kW.m-2) and the lowest standard deviation of ± 0.5 kW.m-2 (lower ignition resistance) compared to the other configurations (critical heat flux in the range from 9 to 10 kW.m-2 and standard deviation from 3.1 to 3.2 kW.m-2).