Effect of Pre-Steaming on Mass Transfer Properties of Fir Wood (Abies Alba L.); A Gymnosperm Species With Torus Margo Pit Membrane

Abstract

In this research, the effect of pre-steaming on mass transfer properties, including air permeability and water vapor diffusivity of fir wood (Abies alba L.), a gymnosperm species with torus margo pit membrane, was evaluated. The pre-steaming was performed at temperatures of 120, 140, and 160°C for 1 hour under a pressure of 2-3 bars. Then, the presteamed specimens were conventionally dried at a constant temperature of 160°C and a relative humidity of 50% to the final moisture content of 10%. Subsequently, the mass transfer properties of the dried specimens were measured in longitudinal and radial directions. Overall, the presteaming was found to be an effective modification method to improve the mass transfer properties of Abies alba L. The improvement was more remarkable for the air permeability as well as through the radial direction. The specimens steamed at the temperature of 160°C had higher mass transfer rates than those steamed at the temperatures of 120 and 140°C. Results of chemical analyses, FT-IR spectroscopy, and SEM imaging provide some explanations for the effects of pre-steaming.

The levels of trace elements and selected vitamins in goats with chronic fluorosis

“…The cell cavities as well as the pit pores may be completely closed due to the collapse, indicating a highly impermeable condition. Damage of the pit membrane and pit torus due to steaming was also reported in previous research (Zhang and Cai 2008;Dashti et al 2012). On the whole, the degradation of holocellulose and severe cell collapse may contribute to the decreased water vapor diffusion rate.…”

“…Pfriem et al (2010) claimed that heat modification can alter the unsteady water vapor sorption behavior of maple (Acer pseudoplatanus L.) and spruce [Picea abies (L.) Karst.]. Dashti et al (2012) found that water vapor diffusivity through fir wood (Abies alba L.) specimens slightly increased as a result of presteaming of the green wood at temperatures of 120, 140 and 160 °C for 1 h, with a more pronounced effect observed in the case of specimens presteamed at 160 °C. This study aimed to decrease the water vapor diffusion coefficient of poplar wood (Populus nigra L.) by steaming the dried wood.…”

Improving impregnation properties of fir wood to acid copper chromate (ACC) with microwave pre-treatment

“…Fir is a gymnosperm species with torus margo pit membrane; the low permeability is mainly due to the pit aspiration during drying. Different modification methods, such as steaming, mechanical incising, drilling techniques and bio-incising were tested to improve the impregnation properties of such refractory wood species (Schwarze et al 2006, Lehringer et al 2009, Dashti et al 2012a. Microwave (MW) radiation is an innovative method to increase the wood permeability and thus to improve the preservative penetration in the wood of various species (Vinden et al 2003, Brodie 2009, Torgovnikov & Vinden 2009, Dashti et al 2012b).…”

Effects of pretreatment with saturated wet air and steaming on the high-frequency vacuum drying characteristics of wood

“…As such, the internal energy of the water molecules inside the wood is increased, its activity is enhanced, the connection force between the structural components of the wood is reduced, and the flow of molecular chains inside the wood is increased. Simultaneously, it reduces the resistance of wood deformation, so that the moisture content (MC) gradient stress and drying shrinkage anisotropy stress are alleviated to reduce the risk of drying defects (Miao and Zhang 2009;Dashti et al 2012;Ratnasingam et al 2014). Harris et al (1989) found that a 4 h steaming pretreatment improves the drying rate in the early drying stages.…”