Deriving Transport Properties using Quasi-Heat-Pulse Solutions for Luikov's Equations of Heat and Moisture Transfer with K-Tester Enhanced with Surface RH Sensors

摘要

The classical Laplace transform solutions of Luikov's differential equations for one-dimensional heat and moisture transfer in porous hydroscopic orthotropic materials for the boundary condition of a gradual heat pulse applied to both surfaces of a flat slab was applicable to this work. The K-tester supplies a quasi-heat-pulse to both sides of a 2 ft square specimen and records precise signals as function of time from surface thermocouples and heat flux thermopiles. With wood products being hydroscopic, tiny surface RH and temperature sensors were placed in a small cavity of an aluminum plate with screen holes that served as the impervious covering for the material sample. The RH and temperature surface measures in conjunction with the isotherm relation for the uniformly wood particle board provided surface moisture content data as a function of time. By supplying heating pulse to one side and cooling pulse to the other side of an encapsulated sample, the changing surface moisture contents for both sides provided data to derive the moisture transport properties, as well as the heat transport properties that were derived with the surface temperature and heat flux measurements. For wood particle board and also calcium silicate board, the estimations of diffusion coefficient, isotherm gradient parameter, and heat of bound moisture evaporation and of heat capacity and thermal conductivity in the Luikov's equations were provided in a single test. Test repetition and comparisons with independent measures provided for error determinations. Future work will include dependencies on temperature and moisture content for the five coefficients