School of Agriculture, Food and Ecosystem Sciences - Research Publications
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ItemThe drying performance and post-drying qualities of Eucalyptus saligna exposed to intermittent and continuous drying(Ministry of Environment and Forestry, 2020-04-01)Eucalyptus saligna tends to develop defects during its drying process, thus limiting its use as construction or furniture material. Intermittent drying, which applies non-heating phases between heating phases, has the potential to overcome this issue. This study evaluated the effects of 3 intermittent and 1 continuous schedule on the species’ drying performance and post-drying qualities. The results showed that the boards from all intermittent schedules exhibit significantly slower drying rates (from -9.4x10-3 /hour to -1.57 x10-2 /hour) than those from the continuous schedule (from -5.12 x10-2 /hour to -1.03 x10-2 /hour). The intermittently-dried boards also developed lower collapse depth (1.162-2.032 mm) than the continuously-dried boards (5.12 mm). Nevertheless, applying higher temperature than that used in the continuous schedule, during the heating phase of the intermittent schedule, potentially increased the moisture gradient, residual drying stress, end check length, internal check percentage, and spring depth.
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ItemQuality assessment of the drying process for Eucalyptus delegatensis timber using greenhouse solar drying technology(Springer Verlag, 2019-01-24)The aim of this study was to investigate the process of drying Eucalyptus delegatensis in a greenhouse solar kiln. Specific objectives were to assess stress formation, moisture gradients and timber distortion, the moisture content distribution within various sections of the timber stack, and internal checking and collapse development within the boards. The maximal temperature and relative humidity (RH) during day time were set at 430C/72% RH. In the night time the temperature was at ambient condition with 90% RH. The strain measurements were undertaken before and after the samples were sliced. The timber quality at the end of drying was assessed based on Australian and New Zealand standard (AS/NZS 4787:2001). The moisture content values in the three different sections (front, middle and end) of 2400 mm long boards were compared by Analysis of Variance. The results showed that the mean compressive strain was -2 x 10-4 mm/mm in the core layers and the tensile strain was 14 x 10-4 mm/mm in the outer layers. All sample boards were within the acceptable limits for cupping, spring and bow, even though the relative humidity level did not reach the set value. However, the amount of twist in three out of twelve sample boards was above the acceptable limit. Mean moisture gradient was 0.6%. There was a significant difference in moisture content at end section compared to the front and middle sections. Internal checking, collapse and residual stress were graded as Class “C” (class A is the highest grade and D is the lowest).
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ItemDrying timber in a solar kiln using an intermittent drying schedule of conventional laboratory kiln(Taylor & Francis, 2018-10-01)The purpose of this study was to apply an intermittent drying schedule developed from a conventional kiln to a solar kiln. Implementing this experiment could help better understand the oscillation of the temperature inside a solar kiln and timber quality during drying progress. The theoretical recharge and discharge curves were used to predict the temperature inside the solar kiln using experimental data obtained previously using a solar kiln. The surface and internal checks were measured using ImageJ freeware, and the development of the Moisture Content (MC) profile was assessed by coring and slicing method for the Eucalyptus delegatensis boards during drying. The results showed that the recharge and dis-charge model can predict the temperature with less than 2 C error from the experimental data in the solar kiln. The total drying time to 12% MC was 87 days for the solar kiln. The drying rate was equivalent to the conventional kiln decreasing at an average rate of 0.2%per day. The surface check formation was found when the MC gradient between the core and the case of the board was greater than 42% at 9 days of drying in the solar kiln and conventional laboratory kiln. The applied drying schedule used in the solar kiln was success-ful and offered similar drying time. However, the oscillation of temperature in the intermittent drying will require further improvement to get closer conditions in a solar kiln.
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ItemComparing two intermittent drying schedules for timber drying quality(Taylor & Francis, 2018)Intermittent drying techniques for drying timber may provide various benefits by improving timber quality and addressing energy efficiency through saving in energy consumption. The purpose of this study was to compare two intermittent drying schedules applied in the treatment of Eucalyptus delegatensis boards, through assessing surface and internal check development, moisture content (MC) profiles during drying, and timber distortions at the end of drying. The study used identical conditions during the heating phase at 45°C/60% relative humidity (RH), except for RH during the nonheating phase (80 and 90%). The results, discussed in this paper, analyzed the timber quality during and at the end of drying. The different RH during the nonheating phase did not generate a significant difference in MC at the case boards between the two drying schedules. The assessed quality of timber at the end of drying was based on AS/NZS 4787:2001. MC gradient, drying stress residual, internal checking and collapse were graded as class “A” (class A is the highest grade and D is the lowest). Bow, cupping, and spring were under the permissible levels based on grading standard AS 2082–2007. Measured data were validated using Drytek® simulation software showing MC movement in case boards.
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ItemNo Preview AvailableApplying a GIS-based Fuzzy Method to Identify Suitable Locations for Solar Kilns(NORTH CAROLINA STATE UNIV DEPT WOOD & PAPER SCI, 2018)
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ItemNo Preview AvailableQuality assessment of Eucalyptus delegatensis dried in the solar kiln(IUFR, 2017)This research aimed to assess the timber quality of Alpine Ash known as Eucalyptus delegatensis dried in a solar kiln. The maximal temperature and relative humidity (RH) during daytime were set at 430C/72% RH and during the night time at ambient temperature (AmbT)/90% RH. The results showed that the humidity was not reached but all sample boards were under the acceptable limit of cupping, spring, and bow. However, the twist of three out of twelve sample boards was above the acceptable limit. The mean compressive strain was -2 x 10-4 mm/mm in the core layers and the tensile strain was 14 x 10-4 mm/mm in the outer layers. Mean moisture gradient was 0.6% MC between outer and inner layers. There was a significant difference in moisture content at end section compared to the front and middle sections. Internal checking, collapse, stress residual were graded as “C” based on Australian standard AS/NZS 4787:2001.