落叶松髓心方材高频真空干燥工艺研究
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摘要
本研究以兴安人工林落叶松含髓心方材(规格1800 mm×100 mm×100 mm)为研究对象,进行了系列高频真空干燥试验,通过不断调整干燥参数,掌握了落叶松含髓心方材高频真空干燥特性,并获得了优化工艺基准。在此基础上考察了切口和过热蒸汽预处理对落叶松髓心方材高频真空干燥速率和质量的影响。并将两种处理方式结合,提出了联合处理优化工艺。具体结论如下:
(1)落叶松含髓心方材高频真空干燥过程中,窑内不同位置的温度有差异,试材靠近正极板的温度大于靠近负极板的温度,本试验中,控制温度为试材靠近负极板1/3处的温度,材温是测定的试材中心位置温度,通常材温要比控制温度高10～20℃,当控制温度在设定值以下时,高频发生器正常工作,控制温度达到设定值时,高频发生器停止工作。窑温是罐体内环境温度,本试验中通常维持在35℃左右。
(2)干燥初始阶段,阳极电流较大,容易达到设定值,而极板电压很小,通常在设定值以下,随着干燥过程进行,木材水分减少,介电常数降低,阳极电流逐渐减小,极板电压逐渐增大,因此IP曲线呈下降趋势,而EL曲线呈上升趋势;整个干燥过程中,罐体内一直处于连续真空状态。
(3)研究中获得的高频真空干燥优化工艺基准为:阳极电流0.4A,极板电压2kV,高频加热3min间歇1min,控制温度为50℃,在干燥初期,真空度选择13.33kPa(100mmHg),在干燥后期,真空度选择6.67kPa(50mmHg)。
(4)纵向切口处理能明显减少落叶松髓心方材在高频真空干燥过程中的表面开裂,切口深度尽量接近髓心,且不超过方材中心位置,切口宽度一般不超过3 mm。试材含水率在纤维饱和点以上时,切口处理对高频真空干燥速度的提高效果很明显,但在整个干燥周期里,切口处理对平均干燥速度提高效果并不显著。切口处理的试材,干燥过程中应力释放,切口张大发生变形,但总干缩和变形量不超过4%。干燥结束后切口位置含水率比其他位置稍低。
(5)常压过热蒸汽预处理能有效减少落叶松髓心方材高频真空干燥过程中的表面开裂,蒸汽处理试材,干燥终含水率分布更加匀匀,但总干燥周期有所延长。切口和过热蒸汽联合处理的试材要比任其单一处理试材干燥开裂少。本研究中,联合处理优化工艺的过热蒸汽温度为105℃,且总干燥周期并不延长,为80h左右。
(6) 105℃过热蒸汽和切口联合处理比单一切口处理或110℃过热蒸汽和切口联合处理后的A面干缩变形要小,B面干缩变形没有显著差异。高频真空干燥初始的10～20h内,效率在60%以上,试材含水率高于20%;随着干燥过程试材含水率的降低,加热效率也逐渐降低,终含水率为12%左右时,加热效率为20%。
In this paper, a series of Radio Frequency/Vacuum drying tests were conducted on boxed-heart square timber of plantation Dahurian Larch (size: 1800 mm×100 mm×100 mm), the drying characteristic for the larch was known well and the optimized drying schedule was gained from the continuous adjustment of drying parameters. The effect of kurfed and superheated steam pretreatment on the drying quality and rate were investigated on the basis of the drying schedule. Then the two pretreatment were combined and the optimized combining treatment was given out. The main conclusions obtained from the research are as follows:
(1) In the process of drying test, temperature differences existed in different position of samples, it means sample temperature at the position closing to anode panel is higher than that closing to cathode panel. In these tests, control temperature was measured at the position of 1/3 of sample closing to cathode panel, and sample temperature was measured at the position of sample core. It is usually that the sample temperature is always 10～20℃higher than control temperature. Radio frequency oscillator was running while the control temperature was below the setting value, otherwise it was out of running. Kiln temperature was measured the air in the tank, it always kept at nearly 35℃in these tests.
(2) IP was very high during the early stage, which was easy to reach to the setting point, while EL was very low, which usually kept below the setting point. As the drying process went on, dielectric constant decreased significantly for the reducing of moisture content, then IP decreased while EL increased gradually, that is the why IP curve dropped and EL curve went up slowly. There was always at consistent vacuum in kiln during the whole drying process.
(3) The optimized schedule gained from these test of Radio Frequency/Vacuum drying was that IP was 0.4A, EL was 2kV, radio frequency heating time was 3min and interval time was 1min, the control temperature was 50℃, vacuum pressure was set on 13.33kPa(100mmHg) during the early stage and 6.67kPa(50mmHg) during the last stage.
(4) Before radio frequency/vacuum drying, kerf treatment made along the longitudinal direction of boxed-heart lumber of larch could reduce surface checks apparently. The kerf depth try to reach to pith and do not exceed the center of cross section, the requirement for kerf width was not more than 3mm. When sample moisture content was above the fiber saturation point, kerf treatment had obvious effect on increasing drying rate, but during the whole drying process, that efficiency was not very obvious. In the drying process, the kerf width was broadened for the losing of drying stress, which caused drying shrinkage value increase. Actually the maximum value was not more than 4%, which was the sum of shrinkage and shape changing. The moisture content at kerf position was lower than that at other position of samples.
(5) Superheated steam pretreatment could reduce surface check effectually during the radio frequency vacuum drying. The samples treated with superheated steam had more uniform distribution of final moisture content, but the total drying cycle had a little bit extending. Combining of the kerf and superheated steam treatment had the better efficacy of reducing surface check than any single one of the treatment. In this study, the optimized steam temperature was 105℃in the combining treatment, and the total drying time was about 80 hours, which was not longer than that of no treatment.
(6) Sample made combining treatment with superheated steam at105℃and kurfing had the less drying shrinkage on side A than that treated with single method and combining treatment with superheated team at 110℃, there was no obvious difference on side B. In the early drying stage of 10～20 hours, the radio frequency heating efficiency was above 60% and the samples moisture content were above 20%. As the drying process continued, sample moisture content reduced as well as the heating efficiency. When sample final moisture content was about 12%, the heating efficiency was 20%.
(1)落叶松含髓心方材高频真空干燥过程中,窑内不同位置的温度有差异,试材靠近正极板的温度大于靠近负极板的温度,本试验中,控制温度为试材靠近负极板1/3处的温度,材温是测定的试材中心位置温度,通常材温要比控制温度高10～20℃,当控制温度在设定值以下时,高频发生器正常工作,控制温度达到设定值时,高频发生器停止工作。窑温是罐体内环境温度,本试验中通常维持在35℃左右。
(2)干燥初始阶段,阳极电流较大,容易达到设定值,而极板电压很小,通常在设定值以下,随着干燥过程进行,木材水分减少,介电常数降低,阳极电流逐渐减小,极板电压逐渐增大,因此IP曲线呈下降趋势,而EL曲线呈上升趋势;整个干燥过程中,罐体内一直处于连续真空状态。
(3)研究中获得的高频真空干燥优化工艺基准为:阳极电流0.4A,极板电压2kV,高频加热3min间歇1min,控制温度为50℃,在干燥初期,真空度选择13.33kPa(100mmHg),在干燥后期,真空度选择6.67kPa(50mmHg)。
(4)纵向切口处理能明显减少落叶松髓心方材在高频真空干燥过程中的表面开裂,切口深度尽量接近髓心,且不超过方材中心位置,切口宽度一般不超过3 mm。试材含水率在纤维饱和点以上时,切口处理对高频真空干燥速度的提高效果很明显,但在整个干燥周期里,切口处理对平均干燥速度提高效果并不显著。切口处理的试材,干燥过程中应力释放,切口张大发生变形,但总干缩和变形量不超过4%。干燥结束后切口位置含水率比其他位置稍低。
(5)常压过热蒸汽预处理能有效减少落叶松髓心方材高频真空干燥过程中的表面开裂,蒸汽处理试材,干燥终含水率分布更加匀匀,但总干燥周期有所延长。切口和过热蒸汽联合处理的试材要比任其单一处理试材干燥开裂少。本研究中,联合处理优化工艺的过热蒸汽温度为105℃,且总干燥周期并不延长,为80h左右。
(6) 105℃过热蒸汽和切口联合处理比单一切口处理或110℃过热蒸汽和切口联合处理后的A面干缩变形要小,B面干缩变形没有显著差异。高频真空干燥初始的10～20h内,效率在60%以上,试材含水率高于20%;随着干燥过程试材含水率的降低,加热效率也逐渐降低,终含水率为12%左右时,加热效率为20%。
In this paper, a series of Radio Frequency/Vacuum drying tests were conducted on boxed-heart square timber of plantation Dahurian Larch (size: 1800 mm×100 mm×100 mm), the drying characteristic for the larch was known well and the optimized drying schedule was gained from the continuous adjustment of drying parameters. The effect of kurfed and superheated steam pretreatment on the drying quality and rate were investigated on the basis of the drying schedule. Then the two pretreatment were combined and the optimized combining treatment was given out. The main conclusions obtained from the research are as follows:
(1) In the process of drying test, temperature differences existed in different position of samples, it means sample temperature at the position closing to anode panel is higher than that closing to cathode panel. In these tests, control temperature was measured at the position of 1/3 of sample closing to cathode panel, and sample temperature was measured at the position of sample core. It is usually that the sample temperature is always 10～20℃higher than control temperature. Radio frequency oscillator was running while the control temperature was below the setting value, otherwise it was out of running. Kiln temperature was measured the air in the tank, it always kept at nearly 35℃in these tests.
(2) IP was very high during the early stage, which was easy to reach to the setting point, while EL was very low, which usually kept below the setting point. As the drying process went on, dielectric constant decreased significantly for the reducing of moisture content, then IP decreased while EL increased gradually, that is the why IP curve dropped and EL curve went up slowly. There was always at consistent vacuum in kiln during the whole drying process.
(3) The optimized schedule gained from these test of Radio Frequency/Vacuum drying was that IP was 0.4A, EL was 2kV, radio frequency heating time was 3min and interval time was 1min, the control temperature was 50℃, vacuum pressure was set on 13.33kPa(100mmHg) during the early stage and 6.67kPa(50mmHg) during the last stage.
(4) Before radio frequency/vacuum drying, kerf treatment made along the longitudinal direction of boxed-heart lumber of larch could reduce surface checks apparently. The kerf depth try to reach to pith and do not exceed the center of cross section, the requirement for kerf width was not more than 3mm. When sample moisture content was above the fiber saturation point, kerf treatment had obvious effect on increasing drying rate, but during the whole drying process, that efficiency was not very obvious. In the drying process, the kerf width was broadened for the losing of drying stress, which caused drying shrinkage value increase. Actually the maximum value was not more than 4%, which was the sum of shrinkage and shape changing. The moisture content at kerf position was lower than that at other position of samples.
(5) Superheated steam pretreatment could reduce surface check effectually during the radio frequency vacuum drying. The samples treated with superheated steam had more uniform distribution of final moisture content, but the total drying cycle had a little bit extending. Combining of the kerf and superheated steam treatment had the better efficacy of reducing surface check than any single one of the treatment. In this study, the optimized steam temperature was 105℃in the combining treatment, and the total drying time was about 80 hours, which was not longer than that of no treatment.
(6) Sample made combining treatment with superheated steam at105℃and kurfing had the less drying shrinkage on side A than that treated with single method and combining treatment with superheated team at 110℃, there was no obvious difference on side B. In the early drying stage of 10～20 hours, the radio frequency heating efficiency was above 60% and the samples moisture content were above 20%. As the drying process continued, sample moisture content reduced as well as the heating efficiency. When sample final moisture content was about 12%, the heating efficiency was 20%.
引文
[1]郭伟,费本华,陈恩灵.我国木结构建筑行业发展现状分析[J].木材工业,2009,23(2):19-22.
[2]高瑞清,李晓玲.杉木人工林木材的高频真空干燥工艺[J].木材工业,2005,19(6):8-11.
[3]蔡英春,林和男.木材高频真空干燥机理.哈尔滨:东北林业大学出版社,2007,18.
[4] Harris,R.A. and M,A. Taras.1984.Comparision of moisture content distribution, stress distribution, and shrinkage of red oak lumber dried by a radio frequency/vacuum drying process and a conventional kiln. Forest Prod.J.34(I):44-54.
[5] Comparison of moisture content distribution, stress distribution, and shrinkage of red oak Lumber dried by radio frequency/vacuum drying process and a conventional Kiln. Forest Products Journal.Jan 1984,34(1):44-54.
[6] Comparison of moisture content variation in red oak lumber dried by a radio frequency/vacuum process and a conventional Kiln Forest Products Journal.May 1986;36(5):25-28.
[7]何玲芝,高频真空干燥木材的研究状况及展望.建筑人造板,1996,vol.3:34-36.
[8] Avramidis Stavros,Liu F, Neilson, Bruce J. Radio-frequency/vacuum drying of softwoods: Drying of thick western red cedar with constant electrode voltage. Forest Products Journal.Jan 1994,44(1):41-47.
[9] Liu Fang, Avramidis.Stavros, Zwick.Robert L. Drying thick western hemlock in a laboratory radio-frequency/vacuum dryer with constant and variable electrode voltage. Forest Products Journal.Jun 1994,44(6):71-75.
[10] Nam-Ho Lee,Hee-Suk Jung. Comparison of Shrinkage, Checking, and Absorbed Energy in Impact Bending of Korean Ash Squares Dried by A Radio-Frequency/Vacuum Process and A Conventional Kiln. Forest Products Journal.Feb 2000;50(2):69-72.
[11] Lee NH,Hayashi K(1997) The effect of low pressure steam explosion treatment on the improvement of permeability in the softwood disk(in Korean).J Korean Wood Sci Technol 25(3):37-42.
[12]苗平,庄寿增,刘进等.蒸汽爆破处理对板材渗透性的影响.南京林业大学学报,2007,Vol.31 No.3: 39-42.
[13] Nam-Ho Lee, Jia-Yan Luo. Effect of steam explosion treatments on drying rates and moisture distributions during radio-frequency/vacuum drying of larch pillar combined with a longitudinal kerf Wood Science(2002)48:270-276.
[14]李晓玲,高瑞清,黑田尚宏等.日本柳杉髓心方材高频真空干燥试验[J].北京林业大学学报,Vol.27 Supp.Sep.,2005:42-45.
[15] Philip d.evans, robin wingate-hill, simon c. barry. the effects of different kerfing and center-boring treatments on the checking of acq treated pine posts exposed to the weather forest products journal feb 2000:59-64.
[16] Hwanmyeong Yeo, Kug-Bo Shim, Do-Sik Lee, et al. Effect of center boring and kerf treatment on kiln-drying of larch square and round timbers. forest products journal,2007,57(11):85-92.
[17] Stavros Avramidis, Ph.D.Robert L.Zwick, P.Eng. radio frequency/vacuum drying of b.c.softwoods; preliminary experiments :82-92.
[18] Avramidis.Stavros, Zwick.Robert L, Neilson.J Bruce. Commercial-scale RF/V drying of softwood lumber. Part 1. Basic kiln design considerations. Forest Products Journal.May 1996:46(5):44-51.
[19] Avramidis.Stavros, Zwick.Robert l.commercial-scale rf/v drying of softwood lumber.part 2.drying characteristics and lumber quality. forest products journal.jun 1996;46(6):27-36.
[20] William B.Smith economic analysis of producing red oak dimension squares with a radio frequency vacuum dry kiln. forest products journal.1996;46(3):30-34.
[21] Diego Elustondo,Stavros Avramidis,Robert Zwick. The demonstration of increased lumber value using optimized lumber sorting and radio frequency vacuum drying. Forest Products Journal.Jan 2005;55(1):76-83.
[22] Stavros Avramidis, Diego Elustondo. simulated comparative analysis of sortingstrategies for rfv drying. wood and fiber science.35(1),2003:49-53.
[23] John N.H.Ruddick,Stavros Avramidis,Fang Fang. application of radio frequency heating to utility poles.part 1.radio-frequency/vacuum drying of roundwood. forest products journal.jun 2000,51(7/8):56-60.
[24] Yoshinori Kobayashi, Yasuo Kawai, izumi miura. Hybrid drying with high frequency heating and hot air under atmospheric pressure I: condition of pressure and moisture in Cryptomeria japonica square lumber.木材学会志.vol,46,no.4,p.282-290.
[25] L.Zhang,S.Avramidis,S.G.Hatzikiriakos. Moisture flow characteristics during radio frequency vacuum drying of thick lumber.Wood Science and Technology.31 (1997) :265-277.
[26] Yasuo Kawai,Yoshinori Kobayashi,Misato Norimoto. Hybrid drying with high frequency heating and hot air under atmospheric pressure IV: water movement in Cryptomeria japonica wood during high-frequency heating. J Wood Sci(2003)48:18-21.
[27] Nam-Ho Lee, Wook Kang. Relationship between radial variations in shrinkage and drying defects of tree disks. J Wood Sci(2004)50:209-216.
[28] Zobel BJ, van Buijtenen JP (1989) Wood variation: its causes and control. Spinger, Berlin Heidelberg New York, p 1.
[29] Kang W, Lee NH (2002) Mathematical models to predict drying deformation and stress due to the differential shrinkage within a tree disk with radial variations. Wood Sci Technol 36:463–476.
[30] Kang W, Lee NH, Choi JH, Li C (2001) Variations of free shrinkage in larch log cross section and drying shrinkage during radiofrequency/vacuum drying. In: 2001 Proceedings of the Korean Society of Wood Science and Technology Fall Meeting. October19–20 2001, Korea.
[31] Forest Products Laboratory (1999) Wood handbook. Gen. Tech.Rep. FPL-GTR-113. Madison, WI:U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. pp 4–28.
[32] W.Kang,N.-H. Lee ,J.-H. Choi. A radial distribution of moistures and tangential strains within a larch log cross section during radio-frequency/vacuum drying. Holz Roh Werkst (2004)62:59-63.
[33] Jung et al. (1999) Development of vacuum-press drying technology for structural softwood lumbers and woods for special goods.Report of Korean Ministry of Agriculture and Forestry, Korea,pp 149–173 (in Korean).
[34] Lee NH et al. (1997) Development of the specification technology for international competitive power of the wooden crafts manufacturing companies around Chri-Mountain area. Report of Korean Ministry of Agriculture and Forestry, Korea, pp 33–86 (in Korean).
[35] Jun-Ho Choi,Nam-Ho Lee. Effect of end-taping and removal of sapwood on radial distribution of moisture content and tangential strains during radio frequency vacuum drying of Cedrela sinsensis log cross sections. J Wood Sci(2004) 50:315-320.
[36] Nam-Ho Lee, Chenguan Li, Jun-Ho Choi, Ui-Do Hwang. Comparison of moisture distribution along radial direction in a log cross section of heartwood and mixed sapwood and heartwood during radiofrequency/vacuum drying. J Wood Sci (2004) 50:484-489.
[37] Lee NH, Li C, Choi JH (2002) Determination of trend of a radial distribution of moisture content within a log cross section by oven drying of circumferential slices (in Korean). J Korean Wood Sci Tech 31:10–15.
[38] Choi JH, Lee NH (2001) Determination of radial distribution of tangential strains within a log cross section by a circumferential slicing method (in Korean). Proceedings of 2001 Fall Meeting of the Korean Society of Wood Science and Technology, Taegu Korea, pp 134–137.
[39] Avramidis S, Zhang L, Hatzikiriakos SG (1996) Moisture transfer characteristics in wood during radio-frequency/vacuum drying. Proceedings of the 5th International IUFRO Wood Drying Conference,Quebec, Canada, pp 125–133.
[40] Kang W, Lee NH (2002) Mathematical modeling to predict drying deformation and stress due to the differential shrinkage within a tree disk. Wood Sci Technol 36:463–476.
[41] Nam-Ho Lee,Kazuo Hayashi,Hee-Suk Jung. effect of radio-frequency/vacuum drying and mechanical press-drying on sgrinkage and checking of walnut log cross sections. forest products journal.may 1998;48(5):73-79.
[42] Chengyuan Li,Nam-Ho Lee. Effect of external compressive load on tangential strain behavior in Japanese larch log cross sections during radio-frequency/vacuum drying. J Wood Sci(2007)53:291-295
[43] Li C, Lee NH (2004) Effect of compressive load on shrinkage of larch blocks under radio-frequency/vacuum heating. Wood Fiber Sci 36:9–16.
[44] Burgert I, Okuyama T, Yamamoto H (2003) Generation of radial growth stresses in the big rays of konara oak trees. J Wood Sci 49:131–134.
[45] Chen Z, Lamb FM (2001) The primary drying force in wood vacuum drying. Proceedings of 7th IUFRO Drying Conference, Tsukuba, Japan, p 117.
[46] Nam-Ho Lee,Kazuo Hayashi. effect of end-covering and low pressure steam explosion treatment on drying rate and checking during radio-frequency/vacuum drying of japanese cedar log cross sections. forest products journal.feb 2000;50(2):73-78.
[47]康雅芬,季华,郝志伟等.高频真空干燥落叶松和水曲柳锯材的研究[J].林业科技,1993(18):40-45.
[48]何玲芝.高频真空干燥木材的研究[J].东北林业大学学报,1992(20):49-53.
[49]庄寿增,孙友富.新型木材高频真空干燥机的研制[J].南京林业大学学报,1994(12):188-191
[50] Yingchun Cai, Kazoo hayashi; Pressure and Temperature Distribution in Wood During Radio-Frequency/Vacuum Drying. 7th INTERNATIONAL IUFRO WOOD DRYING CONFERENCE, 2001:386-391.
[51]蔡英春,林和男,刘一星.高频真空干燥过程中木材内部水分移动的机理.第九次全国木材干燥学术讨论会论文集, 2003:202-211.
[52] Yingchun Cai, Kazuo Hayashi. New monitoring concept of moisture content distribution in wood during RF/vacuum drying. J Wood Sci, 2007, 53:1-4.
[53]王喜民,于建芳.樟子松方材微创处理干燥技术研究.第十二次全国木材干燥学术研讨会论文集,2009,170-183.
[54] Avramidis S. drying characteristics of thick lumber in a laboratory radio-frequency/vacuum dryer [J]. Drying Technology, 1994,12(8):1963-1981.
[55]李晓玲,高瑞清,黑田尚宏等.人工林杨木的高频真空干燥工艺[J].木材工业,2004,18(4):12-15.
[56]小林功,黑田尚宏,久田卓兴,等. Superheated steam pretreatment for the drying process of boxed-heart timber from sugi[J].日本木材工业,3003,58(6):258-263.
[57] G Helsing, R D Graham. Saw kerfs reduce checking and prevent internal decay in pressure-treated Douglas-fir poles [J].Holzforschung, 1976,30(6):184-186.
[58] Luiz C oliveirra, John W Wallace, Dal M Wright, et al. Development of superheated team/vacuum drying schedules for western canadian species [D]. Proceeding of 7th International IUFROI Wood Drying Conference, Japan,2001:140-146.
[59] Morrell J J. Effect of kerfing on performance of Douglas-fir utility pole in the Pacific Northwest [D]. Doc No IRG/WP/3604. The Inter Res Group on Wood Pres Stockholm, Sweden, 1990:6.
[60]尹思慈.木材学[J].北京:中国林业出版社,2002,86.
[61]战剑锋,顾继友,蔡英春等.木材流变学特性对板材常规干燥开裂变形的影响.林业机械与木工设备,2007,第10期:33-36.
[62] CHENG W L, MOROOKA T, NORIMOTO M. Shrinkage stress occurring in the drying process of wood using superheated steam J. Wood research,2002,89:25-26.
[63] Katsuhito OHSHIMA, Toshiro MOROOKA, Misato NORIMOTO. Some Mechanical Properties of Wood Under Superheated Steam J. Wood research,2002,89:27
[2]高瑞清,李晓玲.杉木人工林木材的高频真空干燥工艺[J].木材工业,2005,19(6):8-11.
[3]蔡英春,林和男.木材高频真空干燥机理.哈尔滨:东北林业大学出版社,2007,18.
[4] Harris,R.A. and M,A. Taras.1984.Comparision of moisture content distribution, stress distribution, and shrinkage of red oak lumber dried by a radio frequency/vacuum drying process and a conventional kiln. Forest Prod.J.34(I):44-54.
[5] Comparison of moisture content distribution, stress distribution, and shrinkage of red oak Lumber dried by radio frequency/vacuum drying process and a conventional Kiln. Forest Products Journal.Jan 1984,34(1):44-54.
[6] Comparison of moisture content variation in red oak lumber dried by a radio frequency/vacuum process and a conventional Kiln Forest Products Journal.May 1986;36(5):25-28.
[7]何玲芝,高频真空干燥木材的研究状况及展望.建筑人造板,1996,vol.3:34-36.
[8] Avramidis Stavros,Liu F, Neilson, Bruce J. Radio-frequency/vacuum drying of softwoods: Drying of thick western red cedar with constant electrode voltage. Forest Products Journal.Jan 1994,44(1):41-47.
[9] Liu Fang, Avramidis.Stavros, Zwick.Robert L. Drying thick western hemlock in a laboratory radio-frequency/vacuum dryer with constant and variable electrode voltage. Forest Products Journal.Jun 1994,44(6):71-75.
[10] Nam-Ho Lee,Hee-Suk Jung. Comparison of Shrinkage, Checking, and Absorbed Energy in Impact Bending of Korean Ash Squares Dried by A Radio-Frequency/Vacuum Process and A Conventional Kiln. Forest Products Journal.Feb 2000;50(2):69-72.
[11] Lee NH,Hayashi K(1997) The effect of low pressure steam explosion treatment on the improvement of permeability in the softwood disk(in Korean).J Korean Wood Sci Technol 25(3):37-42.
[12]苗平,庄寿增,刘进等.蒸汽爆破处理对板材渗透性的影响.南京林业大学学报,2007,Vol.31 No.3: 39-42.
[13] Nam-Ho Lee, Jia-Yan Luo. Effect of steam explosion treatments on drying rates and moisture distributions during radio-frequency/vacuum drying of larch pillar combined with a longitudinal kerf Wood Science(2002)48:270-276.
[14]李晓玲,高瑞清,黑田尚宏等.日本柳杉髓心方材高频真空干燥试验[J].北京林业大学学报,Vol.27 Supp.Sep.,2005:42-45.
[15] Philip d.evans, robin wingate-hill, simon c. barry. the effects of different kerfing and center-boring treatments on the checking of acq treated pine posts exposed to the weather forest products journal feb 2000:59-64.
[16] Hwanmyeong Yeo, Kug-Bo Shim, Do-Sik Lee, et al. Effect of center boring and kerf treatment on kiln-drying of larch square and round timbers. forest products journal,2007,57(11):85-92.
[17] Stavros Avramidis, Ph.D.Robert L.Zwick, P.Eng. radio frequency/vacuum drying of b.c.softwoods; preliminary experiments :82-92.
[18] Avramidis.Stavros, Zwick.Robert L, Neilson.J Bruce. Commercial-scale RF/V drying of softwood lumber. Part 1. Basic kiln design considerations. Forest Products Journal.May 1996:46(5):44-51.
[19] Avramidis.Stavros, Zwick.Robert l.commercial-scale rf/v drying of softwood lumber.part 2.drying characteristics and lumber quality. forest products journal.jun 1996;46(6):27-36.
[20] William B.Smith economic analysis of producing red oak dimension squares with a radio frequency vacuum dry kiln. forest products journal.1996;46(3):30-34.
[21] Diego Elustondo,Stavros Avramidis,Robert Zwick. The demonstration of increased lumber value using optimized lumber sorting and radio frequency vacuum drying. Forest Products Journal.Jan 2005;55(1):76-83.
[22] Stavros Avramidis, Diego Elustondo. simulated comparative analysis of sortingstrategies for rfv drying. wood and fiber science.35(1),2003:49-53.
[23] John N.H.Ruddick,Stavros Avramidis,Fang Fang. application of radio frequency heating to utility poles.part 1.radio-frequency/vacuum drying of roundwood. forest products journal.jun 2000,51(7/8):56-60.
[24] Yoshinori Kobayashi, Yasuo Kawai, izumi miura. Hybrid drying with high frequency heating and hot air under atmospheric pressure I: condition of pressure and moisture in Cryptomeria japonica square lumber.木材学会志.vol,46,no.4,p.282-290.
[25] L.Zhang,S.Avramidis,S.G.Hatzikiriakos. Moisture flow characteristics during radio frequency vacuum drying of thick lumber.Wood Science and Technology.31 (1997) :265-277.
[26] Yasuo Kawai,Yoshinori Kobayashi,Misato Norimoto. Hybrid drying with high frequency heating and hot air under atmospheric pressure IV: water movement in Cryptomeria japonica wood during high-frequency heating. J Wood Sci(2003)48:18-21.
[27] Nam-Ho Lee, Wook Kang. Relationship between radial variations in shrinkage and drying defects of tree disks. J Wood Sci(2004)50:209-216.
[28] Zobel BJ, van Buijtenen JP (1989) Wood variation: its causes and control. Spinger, Berlin Heidelberg New York, p 1.
[29] Kang W, Lee NH (2002) Mathematical models to predict drying deformation and stress due to the differential shrinkage within a tree disk with radial variations. Wood Sci Technol 36:463–476.
[30] Kang W, Lee NH, Choi JH, Li C (2001) Variations of free shrinkage in larch log cross section and drying shrinkage during radiofrequency/vacuum drying. In: 2001 Proceedings of the Korean Society of Wood Science and Technology Fall Meeting. October19–20 2001, Korea.
[31] Forest Products Laboratory (1999) Wood handbook. Gen. Tech.Rep. FPL-GTR-113. Madison, WI:U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. pp 4–28.
[32] W.Kang,N.-H. Lee ,J.-H. Choi. A radial distribution of moistures and tangential strains within a larch log cross section during radio-frequency/vacuum drying. Holz Roh Werkst (2004)62:59-63.
[33] Jung et al. (1999) Development of vacuum-press drying technology for structural softwood lumbers and woods for special goods.Report of Korean Ministry of Agriculture and Forestry, Korea,pp 149–173 (in Korean).
[34] Lee NH et al. (1997) Development of the specification technology for international competitive power of the wooden crafts manufacturing companies around Chri-Mountain area. Report of Korean Ministry of Agriculture and Forestry, Korea, pp 33–86 (in Korean).
[35] Jun-Ho Choi,Nam-Ho Lee. Effect of end-taping and removal of sapwood on radial distribution of moisture content and tangential strains during radio frequency vacuum drying of Cedrela sinsensis log cross sections. J Wood Sci(2004) 50:315-320.
[36] Nam-Ho Lee, Chenguan Li, Jun-Ho Choi, Ui-Do Hwang. Comparison of moisture distribution along radial direction in a log cross section of heartwood and mixed sapwood and heartwood during radiofrequency/vacuum drying. J Wood Sci (2004) 50:484-489.
[37] Lee NH, Li C, Choi JH (2002) Determination of trend of a radial distribution of moisture content within a log cross section by oven drying of circumferential slices (in Korean). J Korean Wood Sci Tech 31:10–15.
[38] Choi JH, Lee NH (2001) Determination of radial distribution of tangential strains within a log cross section by a circumferential slicing method (in Korean). Proceedings of 2001 Fall Meeting of the Korean Society of Wood Science and Technology, Taegu Korea, pp 134–137.
[39] Avramidis S, Zhang L, Hatzikiriakos SG (1996) Moisture transfer characteristics in wood during radio-frequency/vacuum drying. Proceedings of the 5th International IUFRO Wood Drying Conference,Quebec, Canada, pp 125–133.
[40] Kang W, Lee NH (2002) Mathematical modeling to predict drying deformation and stress due to the differential shrinkage within a tree disk. Wood Sci Technol 36:463–476.
[41] Nam-Ho Lee,Kazuo Hayashi,Hee-Suk Jung. effect of radio-frequency/vacuum drying and mechanical press-drying on sgrinkage and checking of walnut log cross sections. forest products journal.may 1998;48(5):73-79.
[42] Chengyuan Li,Nam-Ho Lee. Effect of external compressive load on tangential strain behavior in Japanese larch log cross sections during radio-frequency/vacuum drying. J Wood Sci(2007)53:291-295
[43] Li C, Lee NH (2004) Effect of compressive load on shrinkage of larch blocks under radio-frequency/vacuum heating. Wood Fiber Sci 36:9–16.
[44] Burgert I, Okuyama T, Yamamoto H (2003) Generation of radial growth stresses in the big rays of konara oak trees. J Wood Sci 49:131–134.
[45] Chen Z, Lamb FM (2001) The primary drying force in wood vacuum drying. Proceedings of 7th IUFRO Drying Conference, Tsukuba, Japan, p 117.
[46] Nam-Ho Lee,Kazuo Hayashi. effect of end-covering and low pressure steam explosion treatment on drying rate and checking during radio-frequency/vacuum drying of japanese cedar log cross sections. forest products journal.feb 2000;50(2):73-78.
[47]康雅芬,季华,郝志伟等.高频真空干燥落叶松和水曲柳锯材的研究[J].林业科技,1993(18):40-45.
[48]何玲芝.高频真空干燥木材的研究[J].东北林业大学学报,1992(20):49-53.
[49]庄寿增,孙友富.新型木材高频真空干燥机的研制[J].南京林业大学学报,1994(12):188-191
[50] Yingchun Cai, Kazoo hayashi; Pressure and Temperature Distribution in Wood During Radio-Frequency/Vacuum Drying. 7th INTERNATIONAL IUFRO WOOD DRYING CONFERENCE, 2001:386-391.
[51]蔡英春,林和男,刘一星.高频真空干燥过程中木材内部水分移动的机理.第九次全国木材干燥学术讨论会论文集, 2003:202-211.
[52] Yingchun Cai, Kazuo Hayashi. New monitoring concept of moisture content distribution in wood during RF/vacuum drying. J Wood Sci, 2007, 53:1-4.
[53]王喜民,于建芳.樟子松方材微创处理干燥技术研究.第十二次全国木材干燥学术研讨会论文集,2009,170-183.
[54] Avramidis S. drying characteristics of thick lumber in a laboratory radio-frequency/vacuum dryer [J]. Drying Technology, 1994,12(8):1963-1981.
[55]李晓玲,高瑞清,黑田尚宏等.人工林杨木的高频真空干燥工艺[J].木材工业,2004,18(4):12-15.
[56]小林功,黑田尚宏,久田卓兴,等. Superheated steam pretreatment for the drying process of boxed-heart timber from sugi[J].日本木材工业,3003,58(6):258-263.
[57] G Helsing, R D Graham. Saw kerfs reduce checking and prevent internal decay in pressure-treated Douglas-fir poles [J].Holzforschung, 1976,30(6):184-186.
[58] Luiz C oliveirra, John W Wallace, Dal M Wright, et al. Development of superheated team/vacuum drying schedules for western canadian species [D]. Proceeding of 7th International IUFROI Wood Drying Conference, Japan,2001:140-146.
[59] Morrell J J. Effect of kerfing on performance of Douglas-fir utility pole in the Pacific Northwest [D]. Doc No IRG/WP/3604. The Inter Res Group on Wood Pres Stockholm, Sweden, 1990:6.
[60]尹思慈.木材学[J].北京:中国林业出版社,2002,86.
[61]战剑锋,顾继友,蔡英春等.木材流变学特性对板材常规干燥开裂变形的影响.林业机械与木工设备,2007,第10期:33-36.
[62] CHENG W L, MOROOKA T, NORIMOTO M. Shrinkage stress occurring in the drying process of wood using superheated steam J. Wood research,2002,89:25-26.
[63] Katsuhito OHSHIMA, Toshiro MOROOKA, Misato NORIMOTO. Some Mechanical Properties of Wood Under Superheated Steam J. Wood research,2002,89:27