Causes of color changes in wood during drying

The forest industry operates in a dynamic and global market where change and competition are the rule rather than the exception. The color of wood is one of the most attractive features for the modem wood industry. Even when wood is chosen for its structural qualities, attractive and decorative colors are usually an important factor. In many applications, particularly in furniture, decorative products, decorative veneers and flooring, accurate matching of the color of different samples is required. Wood attributes and properties are important because they have a direct bearing on market opportunities and consumer acceptance for many types of manufactured wood products. The aim of this review is to identify causes of wood discoloration and advances in drying technology to overcome this problem. Wood discoloration is a complex phenomenon, mainly affected by heat, light, physiological and biochemical reactions, as well as from attack by microorganisms.

Evaluation of Thermal Effect of PCM Wallboards by Coupling Simplified Phase Change Model with Design Tool

A simplified PCM wallboard model is coupled to an existing design-oriented model of multi-zone buildings. Using a reference model and a basic simulation configuration, the accuracy of the resulting PCM wallboard-building thermal design tool is evaluated. A new performance indicator, called PCM utilization factor, is then proposed in order to estimate the thermal efficiency of using PCM wallboards in buildings. Using this PCM Utilization factor and a degrees-hours indicator, the ability of the PCM wallboard-building thermal design tool to evaluate the effect of PCM wallboards on heating loads and summer thermal comfort in the early design phase of a project is examined in two real case studies: a family house project and an existing office building. The user-friendliness of this design tool, and the short calculation times it leads to when performing a year-long simulation using a standard office computer, make it a well-adapted tool for sensibility studies or multi-criterion optimization for buildings that contain PCM wallboards.

A Kinematics Scalar Projection Method (KSP) for Incompressible Flows with Variable Density

A new scalar projection method presented for simulating incompressible flows with variable density is proposed. It reverses conventional projection algorithm by computing first the irrotational component of the velocity and then the pressure. The first phase of the projection is purely kinematics. The predicted velocity field is subjected to a discrete Hodge-Helmholtz decomposition. The second phase of upgrade of pressure from the density uses Stokes’ theorem to explicitly compute the pressure. If all or part of the boundary conditions is then fixed on the divergence free physical field, the system required to be solved for the scalar potential of velocity becomes a Poisson equation with constant coefficients fitted with Dirichlet conditions.

An Iterative Domain Decomposition Algorithm for the Grad(div)Operator

This paper describes an iterative solution technique for partial differential equations involving the grad(div)operator,based on a domain decomposition.Iterations are performed to solve the solution on the interface.We identify the transmission relationships through the interface.We relate the approach to a Steklov-Poincare operator,and we illustrate the performance of technique through some numerical experiments.

Modes of a Plasma-Filled Waveguide Determined by a Numerical hp Method

We present the application of the recent physics-conforming COOL method[2,4]to the eigenvalue problem of a cylindrical waveguide filled with unmagnetized plasma.Using the Fourier transform only along the waveguide and not in poloidal direction,this is a relevant test case for a numerical discretization method in two dimensions(radial and poloidal).Analytically,the frequency spectrum consists of discrete electromagnetic parts and,depending on the electron density profile of the plasma,of infinitely degenerate and/or continuous,essentially electrostatic parts.If the plasma is absent,the latter reduces to the infinitely degenerate zero eigenvalue of electrostatics.A good discretization method for the Maxwell equations must reproduce these properties.It is shown here that the COOL method meets this demand properly and to very high precision.