用体积置换法测量木材渗透系数的计算与修正

Analysis of the Gas Permeability Measurement by the Volume Displacement Method

从体积置换法测量木材气体渗透系数的基本原理出发，针对水柱上升和水柱下降两种体积置换法的测量装置，分析了体积置换法测量过程中气体渗透压强的变化，以及非稳态条件对体积置换法测量结果的影响．并详细推导了测量中的有关计算式和对非稳态测量补偿的修正因子．此外，运用动力学分析方法，论证了气体渗透压强在测量中的线性变化．其中关于测量的计算及其修正的关键设定的合理性，进一步从理论上阐明了体积置换法测量木材气体渗透系数的精确性．

Based on the principle of gas permeability measurement,this paper analyzes the change in measuring pressure during the measuring process by the rising water and falling water volume displacement methods.It reveals the causes that the measuring process is in an unsteady state condition and shows the method how to correct the effect on the measuring results from the unsteady state condition.The correction factors are derived in detail for both volume displacement methods and the deriving shows that the measuring results that have been corrected are quite exact.In addition,the postulate that change in measuring pressure is linear is demonstrated.That proves the calculations and corrections for the measurement by both the methods to be founded on the rigorous and rational fundamentals.