FIELD: measuring.
SUBSTANCE: invention relates to investigation of thermophysical characteristics of heat-insulating materials. Disclosed is a method of measuring thermophysical properties of heat-insulating materials using a flat pulse heat source using a large volume of experimental data, which consists in making a sample of the analysed material in the form of three plates. Upper and lower plates shall have dimensions H×H×L, and middle plate – H×H×l, where H is size of flat square electric heater, L = 50…70 mm, l = 3...6 mm. Electric heater is placed between the lower and middle plates, and the thermoelectric converter is placed between the middle and upper plates. Sample is placed in an air thermostat, and at the preparatory stage of the experiment, the sample is held at a given initial temperature T0 for a period of time sufficient for a given temperature value T0 to be established at all internal points of the sample. After the beginning of the active stage of the experiment for a given period of time 0<φ≤φu constant power is supplied to the flat electric heater and, according to the thermocouple signal, the change in time of the experimentally measured values of temperature differences is recorded Te(l,τi) = [T(l,τi) –T0] at distance x = l from heater and values of time moments τi corresponding to these measured temperature differences. During the active stage, the obtained experimental data are used to determine the maximum value of the temperature difference Te(l,τmax) =[Tmax–T0] =[T(l,τmax) –T0], after which the current values of temperature differences and the corresponding values of time moments are continued. Value of the parameter γ, which is the ratio of the current temperature difference value [T(l,τi) –T0], taking place at moment in time τi, to maximum value [Tmax–T0] =[T(l,τmax) –T0] temperature difference at a moment in time τ=τmax. Active stage of the experiment is completed as soon as the value of the parameter γ becomes less than preset value γk from range (0.9...0.8), wherein the last recorded value of the moment in time τi is taken as the final value of the moment in time τn. Then, according to the registered experimental data τi,Te(l,τi) = [T(l,τi)–T0], i=1,...,n, calculating the desired values of the thermal diffusivity ax and thermal conductivity λx of the analysed material using an algorithm involving enumeration of values λx, ax with small pitch in preset ranges amin<ax<amax, λmin<λx<λmax and minimization of the objective function, and as the desired values of thermophysical properties, that pair λx, ax, at which the minimum of the objective function F(ax,λx).
EFFECT: high accuracy of determining thermophysical properties of a heat-insulating material by reducing the effect of random measurement errors directly determined during the experiment of physical quantities (temperature differences).
1 cl, 3 dwg
