Management and Economics wood
asghar tarmian; Amir Sepehr
Abstract
The heat transfer through three orthotropic directions and the evolution of temperature gradient in beech (Fagus orientalis) and spruce (Picea abies) during drying were investigated. Thus, due to low capacity of dryer, small flat-sawn boards with dimensions of 80 × 25 × 40 mm (L×R×T) ...
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The heat transfer through three orthotropic directions and the evolution of temperature gradient in beech (Fagus orientalis) and spruce (Picea abies) during drying were investigated. Thus, due to low capacity of dryer, small flat-sawn boards with dimensions of 80 × 25 × 40 mm (L×R×T) were used. Then, the boards were dried at the dry-bulb temperature of 60 °C and relative humidity of 50 %. Four surfaces of the boards were coated by polyurethane-coated aluminum foil to confine the heat flux along one direction. Then, the boards were thermally insulated by 50 mm-thick Styrofoam. Some holes with 1mm in diameter were made on the board specific distances to measure the temperature using thermocouple. The results showed that the temperature of each wood increased as heating up progressed until it reached to the wet-bulb temperature. Then, it remained at an almost constant value as the wet bulb temperature until the wood moisture content reached the hygroscopic range. Furthermore, the pattern of the temperature profile for both wood species was almost identical. The surface temperature of the boards increased until it reached the dry-bulb temperature of 60 °C, while the core temperate remained as the wet-bulb temperature (48-52 °C) throughout the rest of drying period.
asghar tarmian; Seaid Alireza Dehghan; Elnaz Trighnoor; Mohammad reza Pyramon; Razyeh Shamsy; Mohammad Layeghi
Abstract
In this research, the performance of a semi-greenhouse solar kiln was evaluated for dying different wood species in different season in Karaj. This study was carried out in two separate parts. In the first part, the flat-sawn boards of oak and fir with a nominal thickness of 50 mm were dried during summer ...
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In this research, the performance of a semi-greenhouse solar kiln was evaluated for dying different wood species in different season in Karaj. This study was carried out in two separate parts. In the first part, the flat-sawn boards of oak and fir with a nominal thickness of 50 mm were dried during summer of the year 2012. In the second part, the flat-sawn boards of beech and poplar with the same thickness were dried in autumn, 2014 and spring, 2015. For both parts, the boards were also air-dried. The temperature measured inside the solar kiln was 35 ºC greater than that outside during daytime and also the kiln temperature ranged from 55 to 75ºC during 10 a.m. to 2 p.m.. In both parts of research, all wood species dried in the solar kiln faster with better quality compared to those air-dried. The severity of casehardening and surface checking in the boards dried in the solar kiln was lower and more homogenous moisture profile was observed. In addition, the final moisture content was lower for the boards dried in the solar kiln.
Zibab Frozan; asghar tarmian; Reza Ghamari; hamed matini behzad
Abstract
In this research, the effect of wetwood and blue stain on the drying rate and fluid transport coefficients of poplar (P. nigra) was evaluated. For this purpose, five boards with dimensions of 150 × 35 × 45 mm were cut from wet wood, normal wood and stained -wood areas of freshly cut ...
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In this research, the effect of wetwood and blue stain on the drying rate and fluid transport coefficients of poplar (P. nigra) was evaluated. For this purpose, five boards with dimensions of 150 × 35 × 45 mm were cut from wet wood, normal wood and stained -wood areas of freshly cut lumbers in Taleghan region and then dried to the final moisture content of 8 percent inside a laboratory dryer at temperature of 50 °C, relative humidity of 60% and air velocity of 1 m/s. Overall, drying time was 120 h. After drying, the transverse permeability and diffusion coefficients were measured. The results showed that the wetwood had no decreasing effect on the drying rate of poplar wood; however, it reached to the final moisture content slower due to higher initial moisture content. َAlso, the wetwood had no significant effect on the transverse permeability but reduced the diffusion coefficient. In contrast to the wetwood effects, the drying rate, permeability and diffusion coefficients were increased due to the blue stain.
Mohammad Alishahi; Omid Ramezani; Hossein Kermanian; Mehdi Rahmani nia; Seid Atefeh Nasiri; Sahar Jalalvand
Abstract
In this research, the influence of paper drying condition, as one of the most important variable in paper recycling, on the characteristics of fibers was studied. In this respect, bagasse soda pulp was collected from Pars Paper mill in Khozestan province and handsheets were made. The control hand sheet ...
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In this research, the influence of paper drying condition, as one of the most important variable in paper recycling, on the characteristics of fibers was studied. In this respect, bagasse soda pulp was collected from Pars Paper mill in Khozestan province and handsheets were made. The control hand sheet samples were dried at room temperature and the rest of the handsheets were dried using drum dryer set at 60° C for 3 hours, 100° C for 50 minutes and 120° C for 25 minutes to reach the same moisture content as the sheets dried at room temperature. Then, these handsheets were slushed in water and the pulp properties were determined. The results showed that with increasing the drying temperature, cellulose content did not change while hemicelluloses were reduced. Although the assessment of changing the lignin content with micro kappa method showed an increasing trend, but based on previous literature, it was concluded that the result are not justified. Also, the results indicated that changing the degree of polymerization and crystallinity did not show a consistent trend, showing initial reduction following by increased values. These results were attributed to interaction effect of drying temperature and time.
Asghar Taremian; Zinab Frozan; Amir Sepehr; Hadi Ghlamian; Reza Oladi
Abstract
In this study, the physical and anatomical properties of old date palm wood (Phoenix dactylifera L.) and its drying behavior was studied. Four old date palm trees grown in Bam city (Kerman provenience) were felled. Then, boards with the dimension of 300 × 50 × 30 mm were cut at DBH of trees ...
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In this study, the physical and anatomical properties of old date palm wood (Phoenix dactylifera L.) and its drying behavior was studied. Four old date palm trees grown in Bam city (Kerman provenience) were felled. Then, boards with the dimension of 300 × 50 × 30 mm were cut at DBH of trees from pith to bark. After measuring the green moisture content and specific gravity, boards were dried in a semi-industrial kiln to reach the final moisture content of 8% using a mild wood drying schedule. Cross-sectional anatomical measurements were performed on the nearest boards to the bark and pith. Results showed that the green moisture content and specific gravity of date palm wood ranged between 150-260% and 0.29–0.39 and the moisture content was increased and the specific gravity was decreased from pith to bark. Anatomical observations and statistical analysis revealed that there was no statistically significant difference between average number of vessel elements and vessel bundles between pith and bark, but the mean vessel area in pith was considerably greater than bark. Results also showed that the drying rate of date palm wood was high reaching to the final moisture content of 8% within 7 days. Drying rate of bark samples was higher than those of the pith and no deformation and surface crack was observed in the dried boards.
Management and Economics wood
Asghar Taremian; Mahdi Shahverdi; Saeid Eshaghi; Hadi Dashti
Abstract
In this study, the susceptibility of poplar (P. nigra) tension and normal wood to collapse during drying was investigated. Thus, the poplar boards with nominal dimensions of 100 × 50 × 25 mm (L×T×R) were dried using three different drying schedules. In schedule A, the boards were ...
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In this study, the susceptibility of poplar (P. nigra) tension and normal wood to collapse during drying was investigated. Thus, the poplar boards with nominal dimensions of 100 × 50 × 25 mm (L×T×R) were dried using three different drying schedules. In schedule A, the boards were dried under constant conditions (dry-bulb temperature of 600C and wet-bulb temperature of 440C); in schedules B and C, they were dried under a time-based schedule, consisting of 4 and 2 steps, respectively. The initial dry-bulb temperature in schedules A, B and C were selected as 60, 60 and 820C, respectively. After drying, the severity of collapse in the cross section of boards was determined by scanning electron microscope (SEM). The results revealed that collapse did not occur in the boards dried by schedule A. Collapse occurred slightly in the boards dried by schedule B and severe collapse and cell wall degradation developed in the boards dried by schedule C. In the latter, gelatinous layer of tension wood was separated from fiber cell walls. Tension wood was more sensitive to collapse than normal wood. Based on the results, it can be concluded that the occurrence of collapse is influenced by initial dry-bulb temperature rather than wet-bulb depression.
Management and Economics wood
Sohrab Rahimi; Mohammad mehdi Faezipoor; Saeid Eshaghi; Asghar Taremian
Abstract
Poplar lumbers with nominal thickness of 5 cm from Taleghan region, located in west of Karaj were dried under three different schedules including T8-F4 (recommended schedule by F.P.L for poplar), T8-F5 and T9-F4. The purpose of this research was to study the effects of the kiln’s rows (upper, middle, ...
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Poplar lumbers with nominal thickness of 5 cm from Taleghan region, located in west of Karaj were dried under three different schedules including T8-F4 (recommended schedule by F.P.L for poplar), T8-F5 and T9-F4. The purpose of this research was to study the effects of the kiln’s rows (upper, middle, lower) on the quality of the dried boards. Dry bulb temperatures for the schedules were adjusted at 54, 54 and 60 °C, while the final temperatures were adjusted at 82, 82 and 71 °C, respectively. The severity of warping, internal checking and surface checking in kiln dried lumbers were measured and analyzed. The results indicated that the boards in upper, middle and lower rows of the kiln, in all three schedules, did not have any significant difference in 95% confidence interval. Also, the final moisture content of the boards in all three rows and all three schedules were in acceptable quality.
