Evolution of Temperature and Moisture Profiles of Wood Exposed to Infrared Radiation

Abstract

In this article we studied the mechanism of wood drying using infrared (IR) heat transfer. Norway spruce (Picea abies (L.) Karst.) samples of 50 mm and 200 mm thickness were exposed to IR radiation, and the temperature and moisture profiles were recorded at the surface and at the core of the samples under controlled experimental conditions. It is proposed that the moisture transport in wood during drying is governed by osmotic effects. Based on such a hypothesis, the temperature stagnation was explained by a lower localized pressure at the core, which reduced the boiling point temperature of water. As moisture is drawn away due to osmosis from the central region, it cannot fill the empty lumens again; therefore, the pressure decreases locally. The evaporation of the internal moisture is brought about by a partial vacuum resulting in the disappearance of the liquid water.

Uniform large­sized lumber drying system using mw radiation and basing on a single­wire E00 wave energy transmission line

“…Infrared emitters consisting of an energy source and a reflector provide deep or surface heating of the irradiated body or, if necessary, local drying of the object. This type of wood drying is not widely used due to the low degree of penetration of infrared waves into the object [2].…”

Experimental validation of green wood peeling assisted by IR heating – some considerations of the analytical system design

“…The choice of IR technology was also motivated by the potential ease with which IR heaters could be integrated into peeling machines and by the power it offers, which enable a rapid heating, in line with the high peeling speeds (from 1 to 5 m s Previous studies have demonstrated the ability of IR radiation to raise the temperature of the surface and the layers below either for heating ( Makoviny and Zemiar 2004 ) or for drying ( Cserta et al 2012 ). With heating source flux densities of 126 kW m -2 , surface temperatures of 50 ° C can easily be achieved by IR heating in green logs of beech, Douglas fir, and okoum é with peeling speeds of 0.25 -0.5 m s -1 ( Coste 2005 ; in this case, the logs should be defreezed and the IR flux densities were low (4 -20 kW m -2 ) ( B é dard and Lagani è re 2009 ).…”

Mid-infrared absorption properties of green wood

“…Similar measurements applied to oak at moisture contents of between 0 and 20 % suggested that in all probability, the penetration depth of IR was less than 0.1 mm (Makoviny and Zemiar 2004). However, with this method, it remains difficult to precisely evaluate heat absorption into wood by radiation because the measurement techniques are necessarily biased by heat transfer through conduction (Cserta et al 2012). Recent developments in IR spectroscopy have yielded more precise estimates of IR penetration into wood.…”