Engineering properties of wood under different drying methods

This project work focuses on the comparison of the engineering properties of Pyrus communis under solar and air-drying method. Green samples of the wood were dried simultaneously in both solar kiln and open air for 15 days. The daily moisture content reduction (%MC) under both drying conditions were observed and recorded. Mechanical tests (shear strength, compressive strength, hardness and tensile strength) were conducted. The results showed that open air-dried woods attained fibre saturation point (30-25%MC) within three days. Timbers dried in solar kiln attained lower %MC (12.9, 11.0, 14.3, 12.3) when compared to open-air dried samples (22.1, 18.5, 21.1, 17.1). For all the mechanical tests conducted, solar kiln dried timber had higher mechanical properties than the open air-dried woods.

Drying a Standing Teak Tree using a Solar Kiln Drying Method

Understanding the rate of drying of standing trees dried by using a solar kiln drying method could help in predicting the change of moisture content in the tree over a period of drying time. The purpose of this study was to observe the change of moisture content profile in a standing tree during drying. A standing Tectona grandis tree was selected for the experiment with a diameter at breast height of 29 cm in a mixed-species plantation. The tree was girdled with 20 cm width at 20cm above ground. For the experiment, the tree was wrapped in a transparent plastic sheet and a black plastic sheet was installed at the bottom with an angle of 39 °C facing Southwest to maximize solar radiation, with the method being modified from the solar kiln method, which is known as a greenhouse type, with 2 layers of plastic cover. The black and white sheets were placed on the inner side for insulation and for collecting heat from the sun’s radiation, while the outer layer was transparent, which allowed radiation to propagate unhindered in the black sheet. In this study, a sensor for temperature and relative humidity (DHT22) was attached inside the wrapped plastic and the data recorded every 6 min. The results showed that drying a standing teak tree from an initial average moisture content of 105 % to a constant point of 60 % took 80 days under the maximum of the collected temperature of 46 °C inside the wrapped plastic; this finding confirmed that the predicted model of recharge and discharge curve was likely accurate.

PENGERINGAN KAYU KARET (Hevea brasiliensis) DENGAN METODE RADIASI MATAHARI (GREEN HOUSE)

The aim of this study is to analyze the optimal drying time of rubber wood (Hevea brasiliensis) in direct drying in the sun and by a solar kiln (green house). This research is expected to provide information on optimal drying time on natural drying directly under sunlight (solar radiation) and with kiln (Green House) to prolong the utilization of wood and reduce the costs. The parameters tested in this study are water content, density, drying rate, shrinkage, and color change. The results on optimal drying of rubber wood at 6 weeks drying time either in drying under direct sunlight or solar kiln in the green house.

Drying Tectona grandis boards using the simulating solar kiln conditions technique

Timber cracking, drying stress residuals, and the change of moisture content profile were investigated during the drying of Tectona grandis boards in a conventional laboratory kiln. The study applied a technique that simulated solar kiln conditions using a conventional laboratory kiln to dry timber, based on Vientiane’s climatic conditions (Laos). The theoretical recharge and discharge model was used to generate the potential drying schedule for the Vientiane area; then the drying schedule was mimicked in a conventional laboratory kiln. Timber cracking and drying stress residual were monitored and measured using Image J software, and the change of moisture content profile was determined, based on the oven dry method. Measured moisture content data were compared with the theoretical drying model. The results showed that teak boards, of 25 mm thick, had no cracking. The drying stress residual was 0.8 ± 0.3 mm with the maximum of 1.53 mm. The initial average moisture content of 62% decreased to 12% within 16 d, while the case and core moisture contents reached 12% and 14%, respectively. The drying model described the changes of moisture content profile during drying, with a maximal error of 5%.