木材弦向导热系数的理论表达式

Theoretical Expression of Wood Thermal Conductivity in Tangential Direction

分析木材细胞结构形态,以长匣子形作为木材细胞模型,根据材料导热与导电规律的相似性,应用类比推理方法,从欧姆电阻定律推出材料导热的热阻公式;依据该细胞模型和热阻公式推导木材弦向导热系数的理论表达式,从而揭示木材弦向导热系数是木材孔隙率的函数。孔隙率越大的木材,导热系数越小,并实际计算了24种木材的弦向导热系数,与试验值比较,理论值的最大误差12.6%,平均误差小于6.4%。

Cell shape was modeled as a hollow rectanglar body from the cell structure of wood. The formula of thermal resistance of a material was derived by analogy, on the base of the fact that heat conduction of the material was similar to its electric conduction in terms of Ohm＇ resistance law. Theoretical expression of wood thermal conductivity in tangential direction was obtained from the cell shape model and the formula of thermal resistance. The theoretical expression showed that the wood thermal conductivity in tangential direction was a function of fraction void volume in wood. The greater the the fraction void volume was, the smaller the thermal conductivity was. Theoretical values of thermal conductivity were calculated with the derived expression for 24 tree species. The maximum error is 12.6% and average error is below 6.4% between existing experimental values and calculated ones for investigated species in this work.