PDF Publication Title:
Text from PDF Page: 010
wood drying properties. This is essential to validate and provide actual kiln and wood property data for the modelling component of this project and hence optimise the process. As such the proposed model is ‘deterministic’, whereby actual wood property and kiln data are required to ‘feed’ the model to obtain the most accurate simulations possible. A deterministic model is one in which outcomes are determined through known relationships among states or events, without any room for random variation. In such models, a given input will always produce the same output. The wood drying properties measured were: internal wood temperature at various depths using thermocouples, global shrinkage and stress/strain characterisation using strain gauges and jig, mass/moisture content using load cells, and internal pressure using pressure gauges. The kiln conditions measured during vacuum drying were atmospheric pressure, temperature, relative humidity, and air velocity. 2.4 Drying modelling - Measurement of essential wood properties For each species, we measured a number of wood properties deemed essential input data for the model. They were deemed essential, based on previous modelling research relating to model sensitivities (Perré, 1996, Salin, 2010). We calculated other wood properties required for modelling, either from theory or inferred from essential measured wood properties. The essential wood properties measured to achieve accurate modelling results, were: 2.5 • • • • • • wood density – from drying trials initial wood moisture content – from drying trials fibre and vessel porosity – from microscopy imaging gas permeability (radial, tangential and longitudinal directions) – using specialised equipment diffusivity (radial, tangential and longitudinal directions) – using specialised equipment shrinkage (radial and tangential) and sorption isotherm – using specialised equipment. Drying modelling - Vacuum drying modelling As the anatomical configuration of wood is complex, we must write transport equations at the macroscopic scale. This leads to the definition of empirical laws of migration that can be demonstrated to a large extent by averaging over representative volumes (Perré, 1996). At this level, we observe the porous medium as a fictitious, continuous medium. By using this approach, most fluxes can be written as the product of a coefficient times the driving force, both for the porous medium and the surrounding air. The conservation of liquid, water vapour, air and enthalpy enable a set of equations governing transfer in porous media to be derived (Whitaker, 1977). These equations have subsequently been used to model the softwood drying process (Perré, 1996, Perré and Turner, 1999b), where their ability to describe several different drying configurations has been proven. The most recent application of the model describes the heat and mass transfer drying of single boards applied to the growth rings of softwood (Perré and Turner, 2008). This model describes the drying process for both homogeneous and heterogeneous cross sections, where density and transport differences due to the presence of growth rings are accounted. As the species investigated in this study are relatively homogenous, the majority of the transport model equations are from the homogenous model reference. This softwood model, known as TransPore 2D was used as a basis for the hardwood model. MatLab was the predominant platform used to write the heat and mass transfer model code, with some components written in C++ to enable fast convergence (completion). 3PDF Image | Evaluation of super-heated steam vacuum drying
PDF Search Title:
Evaluation of super-heated steam vacuum dryingOriginal File Name Searched:
PN08_2047_Vacuum_Drying_Reviewed_Report.pdfDIY PDF Search: Google It | Yahoo | Bing
5,000 BF Shipping Container Lumber Dry Kiln For Quality Lumber The 5,000 BF container kiln consists of one 40 foot high-cube aluminum shipping container... More Info
Shipping Container Lumber Dry Kilns by Global Energy Global Energy designed and developed the container kiln back in 1991. The purpose is to give access to portable sawmill owners, furniture makers, and small business the value added profit of dry kiln lumber and quality hardwoods... More Info
Vacuum Kiln Conversion Kit for Lumber and Wood Dry Kilns Convert your existing conventional dry kiln into a fast drying vacuum kiln. Similar to vacuum bagging in the boat building and aircraft industry, we have come up with a proprietary process which allows you to build a very simple vacuum kiln at a fraction of the price, and without the intensive conventional metal chamber structure... More Info
Vacuum Pump Cart System for Bagging Clamping Wood Drying and more Vacuum Cart with 2HP Pump and Dual Pistons with multiple multiplex vacuum ports and liquid reservoir... More Info
Vacuum Bagging Basics Vacuum bagging is a method of clamping, which has traditionally been used in the composites industry, but can also be used for vacuum drying materials, including wood products... More Info
CONTACT TEL: 608-238-6001 Email: greg@globalmicroturbine.com (Standard Web Page)