共查询到18条相似文献，搜索用时 203 毫秒
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概述了微波技术在我国木材干燥、木材改性、胶粘剂合成、材料缺陷检测、竹木产品含水率检测和人造板甲醛释放量检测方面的研究成果及应用现状,微波干燥技术使木材在干燥过程中温度梯度和含水率梯度较小,具有加热时间短、干燥质量好、提高出材率等优点;通过微波改性技术,可以赋予竹木材某些特殊的功能,使低档竹木材高档化,从而有效地利用竹木材料,提高经济价值;借助微波技术进行胶粘剂合成,反应速度比传统的加热方法快数十倍;提出了微波技术在木材干燥、木材改性、无损检测、萃取甲醛释放量检测的发展方向和应用前景. 相似文献
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间歇和连续微波干燥对木材内蒸汽压力与温度变化的影响 总被引：1，自引：0，他引：1
对间歇和连续微波干燥过程中木材内部温度、蒸汽压力的变化以及二者相互关系进行探索.结果表明:木材在连续微波干燥过程中,温度的变化大致分为快速升温段、恒温段和后期升温段;微波辐射功率增加,升温速度加快,恒温段温度提高,时间缩短;内裂通常在高含水率木材高功率连续加热时出现;在木材温度上升到100℃之后,适当减少微波功率输入,或采用间歇输入微波能的方法可有效避免内裂的发生;炭化通常出现在木材干燥后期.适当控制木材中含水率,避免过低,减少微波能输入或采用间歇输入微波能的方法,可有效防止木材炭化. 相似文献
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木材微波-真空干燥基本规律 总被引：2，自引：0，他引：2
对微波一真空干燥马尾松木材的干燥规律进行研究.结果表明:微波一真空干燥过程可分为加速、恒速和减速3个阶段,其中恒速干燥占整个干燥时间的50%以上;随着微波辐射时间和木材初含水率的增加,平均干燥速率显著增加;干燥室的真空度与木材的微波-真空干燥速率存在微弱正相关关系;木材厚度对干燥速率影响不显著. 相似文献
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微波技术以其独特的加热机理和特点为木材快速高效干燥提供了一条新途径。笔者简述了近年来国内外在木材微波干燥工艺方面取得的一些重要的研究进展,主要集中在微波功率、含水率和温度等基本干燥参数的优化及红外摄像技术等先进检测技术的应用等方面。同时指出了在木材微波干燥基础理论、干燥工艺、木材结构特性与微波加热非均匀性等方面缺乏系统性研究的问题。建议今后应加强基础理论研究并结合现代测控技术进行系统研究。 相似文献
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A microwave applicator for on line wood drying: Temperature and moisture distribution in wood 总被引：7，自引：0，他引：7
Summary An especially designed open microwave applicator was analysed using wood as the material to be heated and dried. The idea
was to develop an on line microwave construction consisting of several small open applicators, each fed by a small standard
magnetron (for example 1.4 kW main power). The process was analysed by measuring the wood temperature during heating using
an IR-camera and detecting the moisture distribution during drying by CT-scanning. Pine and birch wood samples were used in
the experiments, mainly 40 mm in thickness. The experiments show that the power distribution differs between dry wood and
moist wood. The analysis of the temperature fields captured by the IR-camera during the first minutes allows a rather accurate
determination of the MW power. Consequently, the drying proceeds unevenly in the wood specimens, especially in the longitudinal
direction. The dimensions of the applicator and its relation to the wood dimension are very important. However, the wood was
not destroyed, the temperature and moisture gradients did not affect the wood in terms of checks or deformations. The drying
rate in different positions of the specimen varied between 0.30 and 0.80 percentage moisture content/min. The uneven energy,
meaning temperature and field distribution, is to be compensated in the future by a moving wood load and by alternating the
position of each applicator in a larger scale microwave pilot plant.
Received 25 February 1997 相似文献
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Improvements in dimensional stability and lightfastness of wood by butyrylation using microwave heating 总被引：1，自引：0，他引：1
Microwave heating was used as the heat source for butyrylation of wood with the aim of reducing the reaction time. The photostability and dimensional stability of butyrylated wood were also investigated in this study. Chemical changes of wood were confirmed by cross polarization/magic angle spin 13C-nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) after butyrylation by microwave heating. Results from DRIFT with the Si-Carb sampling technique revealed that, using microwave heating, a higher degree of butyrylation of maple wood occurred in the middle of the specimen than on the outer surface. The increase in yellowness index of butyrylated wood treated with microwave heating was much less than that of untreated wood after the lightfastness test, indicating that photoyellowing of wood is effectively inhibited by butyrylation using microwave heating. The dimensional stability of wood was also improved after modification. 相似文献
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以烘干法和压干法两种干燥方式处理的8种地采暖用实木地板为试验材料,与烘干法作对比,探究压干法对地采暖用实木地板尺寸稳定性的影响;通过木材水分吸湿特性分析压干法提高地采暖用实木地板尺寸稳定性机理。结果表明:采用压干法能明显提高地采暖用实木地板尺寸稳定性,但对径向耐湿尺寸稳定性改善不大。相比烘干法,采用压干法干燥的番龙眼、印茄、朴木、栎木4个树种的地采暖用实木地板径向收缩率分别降低53.8%、60.0%、47.1%、44.4%,轴向收缩率分别降低70.9%、55.6%、37.0%、37.5%,轴向膨胀率分别降低43.2%、31.8%、23.4%、16.5%。这与木材半纤维素的降解、分子链结构活性的增强和纤维素结晶度增加有关。 相似文献
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木材干燥过程中,介质循环速度是一个影响木材干燥的重要工艺参数.在木材各含水率阶段,通过试验分析研究不同介质循环速度对木材干燥速度的影响.结果表明,介质循环速度对干燥速度的影响显著,但其影响随木材含水率（MC）的降低而减弱.在低介质循环速度条件下,试件MC大于45％时,表现为木材干燥速度和木材含水率偏差（△MC）随循环风速的增加而增加,呈显著正相关关系;试件MC介于35％ ～ 45％之间时,正相关关系存在但不显著;试件MC小于35％时,干燥室内循环风速的大小不影响木材的干燥速度和木材含水率偏差（△MC）.对试件表层含水率分析,试件表层含水率大于25％时,试件表面循环风速对试件表层含水率的影响显著;试件表层含水率小于25％时,试件表面循环风速对试件表层含水率的影响很小,不同循环风速下试件表层含水率基本一样. 相似文献
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为给鲜花椒微波烘干效果的研究和花椒微波烘干机的研制奠定基础,分别利用小型平板层式微波炉及自制大型微波炉对鲜花椒进行了间断式和连续式烘干试验。试验结果表明:无论采用旋转式微波炉还是平板层式微波炉,烘干时间均随鲜花椒投料量的增加而延长,干燥后花椒香味降低;填料约700 g,以小型旋转式微波炉和平板层式微波炉烘干所用时间分别约为44、62 min,前者的烘干效率比后者提高20.48%;鲜花椒在旋转式微波炉中水分蒸散过程表现为抛物线型,在烘干过程中花椒种子集中脱出,烘干效率高,但其在平板层式微波炉中水分蒸散过程呈缓慢降低的斜线型,种子在烘干过程的最后阶段才脱出,烘干效率低;以自制大型微波炉烘干,填料3.45 kg,最佳加热上限温度和运行温度分别为55℃和41～50℃,加热—除湿循环中加热8 min、除湿90 s,烘干时间为45 min,较以小型平板层式微波炉烘干所用时间缩短29%。研究结果还表明:以微波炉烘干鲜花椒,可极大地缩短鲜花椒的干燥时间;以自制大型微波炉烘干鲜花椒,最大填料量约8 kg,可以满足农户对小批量鲜花椒的烘干要求。 相似文献
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Physical interpretation of the three characteristic groups of acoustic signals emitted during convective drying of wood is the main subject of this paper. The acoustic emission (AE) was to evidence the fracture intensity during drying of a birch wood sample of cylindrical shape. To explain the three characteristic groups of acoustic signals, and particularly the last one, a mechanistic model of drying was applied to analyse the drying induced stresses in the tested sample. One can conclude from this analysis that the third group of acoustic signals arises when the surface stop to shrink and the wet core (initially in compression) begins to dry. The shrinkage of the core causes compression of the boundary layer and tension of the core. Thus, the reverse of the stress signs in the cylinder cross-section takes place and this possibly involves the destruction of wood structure in the tensed core. 相似文献