Humidity Control Efficiency of Low-Density Particleboards for Interior Walls Ⅲ.Moisture absorption rates and moisture conductivities

摘要

A moisture absorption test and a number of simulations predicting the heat and moisture transfer in a board were conducted for alow-density particleboard(LDPB), a wood lining board(WLB), and some laboratory particleboards. The moisture absorption rate(Va),the moisture conductivity(λu27),and the moisture content profile of each board type were calculated and compared.LDPB was more hygroscopic than WLB in that its Va was calculated to be 1.9 times larger, its λ′ 4.3 times greater, and its d_95(the depth from the board surface which accounts for 95% of the moisture absorbed) 1.6 times larger. These values help explain the superior performance of the LDPB over the WLB for humidity control as described in the first paper of this series. These differences suggest that the vapor diffusion paths are larger and more continuous in LDPB than those in WLB. A reduction in density from 820kg/㎥ to 540kg/㎥ increased Va 1.7 times, λ′ 4.7 times, and d_95 2.1 times. These results suggest that it is the void volumes which determine the penetration of moisture into a board, and that a greater permeability can more than compensate for a decrease of moisture capacity. Treating moisture capacities as a function of humidity for the simulation was found useful in predicting heat and moisture transfers.