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specimen RH1 cable tie saturated NaCL and water Plate 16. Vaporimeter schematic tyre tube flux PVC cylinder hole RH2 RH2 > RH1 glass vessel To create an airtight seal around the device, we used a cylinder of PVC with an attached piece of tyre tube inside the PVC clamped using cable ties. A small hole was drilled into the side of the PVC pipe. Using a vacuum, air was aspirated through the hole, thus sucking the tyre tube against the PVC pipe. This enabled us to lower the apparatus over the specimen and glass. By releasing the vacuum, the tyre tube relaxes tightly against the specimen and vessel creating an airtight seal. We placed the vaporimeter devices into the constant environment chamber at 35 oC and 40% relative humidity (RH1) to produce equilibrium conditions of 7% MC. With this device assembly, two different relative humidities occur on each side of the wood specimen to create a diffusive flux driving force through the sample. We measured the flux by weighing the device periodically over time and measuring the overall weight loss of the device. The samples were weighed inside the constant environment chamber via sealed glove gauntlets in the chamber door, and a mass balance, accurate to 1mg, placed inside the chamber. This allows mass flux measurements without disruption of conditions of temperature and humidity, and assures their good stability whatever the length of testing. By plotting the weight change as a function of time, after a few days a steady-state relationship occurs where the plot becomes a straight line (linear relationship between weight change and time). The diffusion coefficient through gross wood (Db) is then calculated from the following formula (Siau, 1979), Db = 100mL tAGρ w ∆X (39) Where m is the mass vapour transferred through the specimen (g), L is the specimen thickness (m), t is time (s), A is the specimen surface area (m2), G is the specific gravity of the specimen at moisture content X, ρw is the normal density of water (kg/m3), and ∆X is the moisture difference between two parallel surfaces of the specimen (%) calculated by: ∆X = Xb + Xt 2 (40) 32 Evaluation of super–heated steam vacuum drying viability and development of a predictive drying model for Australian hardwood species – Final reportPDF Image | Evaluation of super-heated steam vacuum drying
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