METHOD OF MEASUREMENT OF MOISTURE DIFFUSION COEFFICIENT IN CAPILLARY POROUS SHEET MATERIALS Russian patent published in 2011 - IPC G01N13/00 

FIELD: machine building.

SUBSTANCE: method of measurement of moisture diffusion coefficient in capillary-porous sheet materials consists in placement of examined sheet material on flat substrate of moisture-proof material and in pulse point moistening surface of examined material at initial moment of time. Further, values of a signal of galvanometric sensor of moisture content is recorded at a time-constant step. There is determined maximal value of signal E_max. Examined specimen placed of the substrate is covered with a plate of a moisture-proof material. A through orifice for supply of moisture is drilled in centre of the plate. Electrodes of the galvanometric sensor of moisture content with a known calibration characteristic are set at specified distance from the centre of this orifice. Directly before the moment of pulse point moistening the examined specimen there is recorded an initial value of the sensor signal E₀. Tests are completed when a current value of the galvanometric sensor signal of moisture content is lowered to a value of E≤E₀+0.6(E_max-E₀) upon reaching a maximal value of E_max. After completion of the experiment at each time step there is calculated ratio equal to ratio of difference between a current value of the galvanometric sensor signal of moisture content E and an initial value of the signal E₀ to difference between a maximal value of the signal E_max and initial value of the signal E₀. There are fixed two moments of time corresponding to values of ratio α=0.48 and α=0.62, while values of desired coefficient of diffusion is determined by formulas: where a'_m is coefficient of diffusion determined at a moment of time τ' corresponding to α=0.48; α''_m is coefficient of diffusion determined at a moment of time τ" corresponding to α=0.62; r₀ is coordinate of placement of sensor of local moisture content; z' is major root of equation z·exp(1-z)= α at α=0.48; z" is less root of equation z·exp(1-z)= α at α=0.62; also, as a medium value of coefficient α_m + α" of diffusion there is accepted the value

EFFECT: raised accuracy and performance of measurement of moisture diffusion coefficient in capillary-porous materials.

3 dwg