The Design of a Measuring Instrument for Determining the Diffusion Coefficient of Solvents in Thin Articles Made of Capillary-Porous Materials

Non-destructive testing method for determining the solvent diffusion coefficient in the porous materials products

“…To carry out experimental studies, we used the information-measuring system developed by the "National Instruments" technology [12] with a modernized measuring device [8]. Before carrying out the active experiment, the required value of the pulse mass was preliminarily determined by formula (6).…”

“…At a pulse of 7.0 × 10 -5 kg, the sensors information with coordinates r 0 <4 mm does not allow to calculate the diffusion coefficient at all. The value of C max exceeds C e , and the ECC static characteristic is on the saturation plateau [8]. Figure 4 presents the results of numerical experiments when we determine the dependence max  of the ethanol diffusion coefficient in a gas silicate platе on r 0 obtained in the study for the same values of solvent doses.…”

“…Due to the monotonicity of static ECC characteristic [8], the moments of reaching the maximum concentration C(r 0 ,) and the converter maximum EMF E(r 0 , ) is coincide, it is possible to realize the measurement method without preliminary calibration of the ECC. The experience with the application of electrochemical converters [8,9] shows that it is expedient to use the range of the static characteristic near the value 0.5C e , characterized by high sensitivity and stable signal. Here C e is the diffusing substance concentration in the PM solid phase at equilibrium with saturated solvent vapors at a given temperature.…”

“…The mathematical model of the relative error root-mean-square estimate in determining the sought diffusion coefficient has the form [8,10]: are, respectively, the relative error in determining the coordinate of the calculated cross-section and the time to reach the maximum on the curve of the concentration change in the calculated section; δ m is the total value of the methodical error due to the incomplete correspondence of the mathematical model used to real physical processes.…”

“…It was shown in [8] that when ECC electrodes are located on the equipotential samples surfaces with respect to a pulsed source of solvent dose, a value essentially depends on the nature of the change in the concentration C(r 0 ,) and the error in its determination. In figure 2, 3 it is shown as an example, the calculated dependences in the relative C max /C e concentrations change and the error  C max = ∆C/C max on r 0 obtained in the study of the diffusion coefficient of ethanol in a dry state gas silicate plate (530 kg/m 3 ) for different dose values of the solvent pulse Q.…”