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Most European hardwoods are nowadays under-utilized due to drawbacks such as low dimensional stability, durability and surface hardness. Seven hardwood species were thermally and/or chemically modified in order to improve these disadvantages. Heat treatment was carried out in air at atmospheric pressure at three temperatures, while two types of chemical modifications were tested, the first being based on furfuryl alcohol with tartaric acid, the second being based on succinic anhydride and glycerol. Then, modified woods were studied to determine weight loss due to thermal treatment, solution uptake, weight percent gain and swelling due to chemical modification processes. After that, main properties of chemically modified woods were characterized including density, equilibrium moisture content, dimensional stability and surface hardness. Effect of thermal pretreatment on subsequent chemical modification and on properties of modified woods obtained have also been evaluated. Combination of thermal modification with chemical modification had led to better improvements than each separately. Furfurylation treatment appeared to be more efficient than polyester modification. Most of the modified samples were denser, more stable and harder than native wood. These modified woods might compete with imported tropical wood for applications requiring high stability and hardness, such as joinery, decking or flooring, music instruments, handles for tools or kitchen utensils. [ABSTRACT FROM AUTHOR]

An X-ray density analyzer was used to determine the evolution of the moisture content (MC) profiles of a wood board during drying. Tests were performed on quartersawn boards of five wood species (oak, beech, Scotch pine, birch, alder) of two thicknesses (20 and 40 mm) dried at low temperature. The water vapor diffusion coefficient and liquid permeability of each wood species were determined by inverse analysis of the profiles using a computational model of coupled heat and mass transfer. These parameters were also measured by classical methods for validation purposes. The inverse method gives values close to the measured ones when using the evolution of the moisture profile, but also quite remarkably when using only the evolution of moisture at the core of the board. On the contrary, the method is less accurate when using only the average kinetics as experimental information. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the effect of the position of the solar collector absorber and stagnant air relative to the airflow path on the thermodynamic properties of traversing air and the overall thermal performance of the collector. A numerical model was developed and validated using five different absorber design positions. Numerical results are validated using experimental data obtained from Epinal (France). The model was subsequently used to parametrically study the influence of these absorber positions on the density, temperature, velocity variations of the airflow through the collector and the thermal efficiency of each case scenario. The study showed the importance of stagnant air in solar collector thermal performance. Also, it showed that when one absorber is used, it is better to locate the absorber on the top of the airflow path than below the airflow path. Sandwiching the airflow path between double absorbers with the upper absorbers having stagnant air between it and the plexiglass cover and the down absorber having stagnant air between it and the bottom of the collector can produce a thermal efficiency of 31% which is 2% higher than the closest case and 13% higher than the worst-case design. [ABSTRACT FROM AUTHOR]