CAJ | 학술논문

【目的】提出一种基于有限差分法逆求木材导热系数的方法，以期弥补传统测量法设备复杂、价格高昂的不足，为后续建立导热系数的回归方程提供可靠数据。【方法】运用一维热传导控制方程描述木材升温过程中内部温度变化。以兴安落叶松弦切锯材为对象，通过试验获得锯材沿厚度方向的温度数据(温度检测：使用NEC Remote Scanner Jr． DC3100多点信号巡检仪通过埋入锯材的 T形热电偶获得)，采用有限差分逆求法，合理化边界条件后编程求解其在不同含水率、不同温度下的径向导热系数(其中，控制方程离散后的导热系数差分矩阵采用追赶法求解，所有差分方程均在 Matlab2010b软件编程并运行)，探讨并分析其随含水率、温度的变化规律。【结果】1)兴安落叶松锯材径向导热系数计算值沿厚度方向存在一定波动性，但其平均值0.1061 W·m －1 K －1(标准差0.0108)符合实际要求，且与理论计算值(0.1109，0.1252W·m －1 K －1)较为接近；2)含水率、温度对导热系数影响显著，且前者影响高于后者(含水率与温度的 F－检验分别为126.9421，99.0083)；含水率、温度共同作用对导热系数亦存在显著影响(交互作用的 F －检验为164.2975)；导热系数随含水率的升高而增大，随温度的升高亦增大；3)木材材性与内部含水率分布对导热系数的影响较大。【结论】通过试验获得木材内部可靠的温度分布与变化数据后，运用有限差分逆求法可快速、准确获得内部与测温点相对应位置的导热系数，尽管计算值存在一定波动性，但其平均值与理论计算值相吻合，说明运用该方法测算木材导热系数是可行的。相比传统导热系数测量方法，该方法最大优势在于经济且不受试样尺寸限制；同时，可以测算试样内部任意层位置导热系数。今后为提高测算精度，木材内部由于水分迁移产生的热量变化与材性差异应考虑使用该方法；同时，为推广此方法，将程序可视化亦是今后研究的方向。【目的】提齣一種基于有限差分法逆求木材導熱繫數的方法，以期瀰補傳統測量法設備複雜、價格高昂的不足，為後續建立導熱繫數的迴歸方程提供可靠數據。【方法】運用一維熱傳導控製方程描述木材升溫過程中內部溫度變化。以興安落葉鬆絃切鋸材為對象，通過試驗穫得鋸材沿厚度方嚮的溫度數據(溫度檢測：使用NEC Remote Scanner Jr． DC3100多點信號巡檢儀通過埋入鋸材的 T形熱電偶穫得)，採用有限差分逆求法，閤理化邊界條件後編程求解其在不同含水率、不同溫度下的徑嚮導熱繫數(其中，控製方程離散後的導熱繫數差分矩陣採用追趕法求解，所有差分方程均在 Matlab2010b軟件編程併運行)，探討併分析其隨含水率、溫度的變化規律。【結果】1)興安落葉鬆鋸材徑嚮導熱繫數計算值沿厚度方嚮存在一定波動性，但其平均值0.1061 W·m －1 K －1(標準差0.0108)符閤實際要求，且與理論計算值(0.1109，0.1252W·m －1 K －1)較為接近；2)含水率、溫度對導熱繫數影響顯著，且前者影響高于後者(含水率與溫度的 F－檢驗分彆為126.9421，99.0083)；含水率、溫度共同作用對導熱繫數亦存在顯著影響(交互作用的 F －檢驗為164.2975)；導熱繫數隨含水率的升高而增大，隨溫度的升高亦增大；3)木材材性與內部含水率分佈對導熱繫數的影響較大。【結論】通過試驗穫得木材內部可靠的溫度分佈與變化數據後，運用有限差分逆求法可快速、準確穫得內部與測溫點相對應位置的導熱繫數，儘管計算值存在一定波動性，但其平均值與理論計算值相吻閤，說明運用該方法測算木材導熱繫數是可行的。相比傳統導熱繫數測量方法，該方法最大優勢在于經濟且不受試樣呎吋限製；同時，可以測算試樣內部任意層位置導熱繫數。今後為提高測算精度，木材內部由于水分遷移產生的熱量變化與材性差異應攷慮使用該方法；同時，為推廣此方法，將程序可視化亦是今後研究的方嚮。
【목적】제출일충기우유한차분법역구목재도열계수적방법，이기미보전통측량법설비복잡、개격고앙적불족，위후속건립도열계수적회귀방정제공가고수거。【방법】운용일유열전도공제방정묘술목재승온과정중내부온도변화。이흥안락협송현절거재위대상，통과시험획득거재연후도방향적온도수거(온도검측：사용NEC Remote Scanner Jr． DC3100다점신호순검의통과매입거재적 T형열전우획득)，채용유한차분역구법，합이화변계조건후편정구해기재불동함수솔、불동온도하적경향도열계수(기중，공제방정리산후적도열계수차분구진채용추간법구해，소유차분방정균재 Matlab2010b연건편정병운행)，탐토병분석기수함수솔、온도적변화규률。【결과】1)흥안락협송거재경향도열계수계산치연후도방향존재일정파동성，단기평균치0.1061 W·m －1 K －1(표준차0.0108)부합실제요구，차여이론계산치(0.1109，0.1252W·m －1 K －1)교위접근；2)함수솔、온도대도열계수영향현저，차전자영향고우후자(함수솔여온도적 F－검험분별위126.9421，99.0083)；함수솔、온도공동작용대도열계수역존재현저영향(교호작용적 F －검험위164.2975)；도열계수수함수솔적승고이증대，수온도적승고역증대；3)목재재성여내부함수솔분포대도열계수적영향교대。【결론】통과시험획득목재내부가고적온도분포여변화수거후，운용유한차분역구법가쾌속、준학획득내부여측온점상대응위치적도열계수，진관계산치존재일정파동성，단기평균치여이론계산치상문합，설명운용해방법측산목재도열계수시가행적。상비전통도열계수측량방법，해방법최대우세재우경제차불수시양척촌한제；동시，가이측산시양내부임의층위치도열계수。금후위제고측산정도，목재내부유우수분천이산생적열량변화여재성차이응고필사용해방법；동시，위추엄차방법，장정서가시화역시금후연구적방향。
Objective]To develop a precise,quick and economic method for determination the thermal conductivity of wood,this paper proposed a new numeral method based on the inverse finite difference method,which can overcome the drawback of traditional methods such as depending on relatively complex and expensive instrumentations. This will provide reliable data for the development of thermal conductivity’s regression equation. [Method]A one-dimensional governing equation of the heat conduction was used to describe the temperature variation inside the lumber during the heating process. The timbers obtained through tangential cut in larch ( Larix gmelinii) plantation,with dimensions of 600 mm in length,220 mm in width,and 40 mm in thickness,and moisture contents of 28. 3%,41. 2%,62. 3%,were used in the experiments. Temperature along the thickness direction was obtained via experiments. The detection of temperature was obtained using NEC Remote Scanner Jr. DC3100 with T-type in wood. With inverse finite difference method and rationalization of boundary condition,the determination of thermal conductivity in radial direction with different moisture content and temperature was achieved. Difference matrix of thermal conductivity from the discrete control equations could be solved by tridiagonal matrix algorithm (TDMA). All difference equation were programmed and run in Matlab 2010b. At the end,the variation law of thermal conductivity with the changing of moisture content and temperature was discussed and analyzed. [Result]The results showed that: 1 ) although some fluctuation along the thickness direction of thermal conductivity in larch plantation was observed,the average value (0. 106 1 W·m -1K -1,standard deviation(SD) was 0. 010 8) agreed with theoretical calculating value (0. 110 9,0. 125 2W·m -1K -1);2) MC and T had apparent effect on the thermal conductivity and the former influences slightly higher than the latter ( FMC-test is 126. 942 1,FT-test is 99. 008 3). The interaction of MC and T also had apparent effect on the thermal conductivity (FMC × T-test is 164. 297 5). The thermal conductivity increased with increasing MC and T; 3 ) Wood properties and the distribution of MC had apparent effect on the thermal conductivity. [Conclusion]Reliable temperature data in wood was obtained via experiments. The thermal conductivity in the position corresponding to temperature measuring points was obtained quickly and accurately with IFDM. Although some fluctuation of thermal conductivity was observed,the average value agreed with theoretical calculating value. It indicted that the determination of thermal conductivity with finite difference method is feasible. Compared with traditional method,the main advantage of our method is economic and unconstrained in size of specimen. The thermal conductivity of any layer of wood can be obtained. To improve precision,heat changes with moisture migration and the difference of wood properties should be considered. To expand the method, program visualization should also be researched in the future.