RU2153664C1 - Method and device for proximate determination of thermal conductivity of solid materials - Google Patents

Abstract

FIELD: study of thermophysical properties of solid materials, materials possessing heterogeneous properties inclusive. SUBSTANCE: the method consists in heating of specimen surfaces at movement of platform with specimens and heating unit relative to each other and monitoring of temperature, determination of surplus limiting temperatures for calculation of the unknown quantity of thermal conductivity. The novelty is in optimum selection of a number of interrelated operating and design parameters in the process of pretuning of the device for measurements for attainment of the maximum accuracy of measurements, minimum influence of arbitrary distribution of power density according to the heating spot on specimen surfaces and arbitrary shape of the section of temperature monitoring on the results of measurements. The invention provides for measurement of thermal conductivity within a wide range from 0.006 to 250 W(mK) with a total error not exceeding 2.5% at confidence coefficient of 0.95. EFFECT: enhanced accuracy of measurements. 20 cl, 9 dwg

Description

 The invention relates to thermophysical instrumentation, and more specifically to methods of rapid determination of thermal conductivity of solid materials and to devices for their implementation.

 A known method for determining the thermal conductivity of materials, including heating the surface of the test sample with a moving point source of heat and recording the temperature of the surface of the sample along the line of movement of the heat source by a temperature sensor moving with a fixed lag from the heat source [1].

 When implementing this method, the desired value is determined with a large error due to the fact that the optimal relations between the characteristics of the heating source, temperature sensor and the distance between them and the speed of their movement are not determined.

There is also a method for the rapid determination of the thermal conductivity of solid materials [2], which includes heating the surface of the test sample and the surface of the reference sample when moving relative to each other the platform with the samples and the heating block of the samples and recording their temperature, containing a heating source and a temperature sensor. By measuring the surface temperatures of these samples with a temperature sensor at the temperature recording site located along the line of movement of the heating spot behind it, the limiting excess temperatures of the test sample TT ₀ and the reference sample T _R -T _{R0 are} determined, where T and T _R are respectively the limiting temperatures of the heated test and reference samples, T ₀ and T _R0 are the initial temperatures of the investigated and reference samples, and the desired thermal conductivity is calculated by the formula:
λ = λ _R (T _R -T _R0 ) / (TT ₀ ), (1)
where λ _R is the known thermal conductivity of the reference sample. The distance x ₀ from the temperature recording site to the center of the heating spot is set so that the ratio x ₀ > 5 / K ^{1/2 is} satisfied, where K is the concentration coefficient of the source (heating spot) with a dimension of m ² , which is undertaken in order to approximate the excess surface temperature of the studied and reference samples in the area of its registration to excess temperature when the samples are heated by a point source.

The disadvantages of the prototype method [2] include the following. The choice of the distance x _{0 of the} lag of the surface area in which the temperature is recorded from the heating spot from the condition x ₀ > 5 / K ^1/2 does not provide thermal conductivity measurements with controlled or specified accuracy and can be the cause of unacceptably large measurement errors in precision measurements. This is due to the fact that this condition does not take into account the influence of the speed of movement (scanning) of the heating source and temperature sensor, the size of the temperature recording section, and the thermal properties of the heated and reference samples. This condition is not applicable if the shape of the heating spot is different from circular, and the distribution of the specific power of the source over the heating spot does not meet the normal law. The absence of criteria for choosing the size and shape of the temperature recording area on the surface of the reference and studied samples, the absence of criteria for choosing the scanning speed and the reference sample also leads to large errors in the measurements of thermal conductivity. The absence of criteria for choosing the optimal parameters of the measurement mode in their relationship (dimensions of the heating spot and temperature recording area, distance x _{0 of the} lag of the center of the temperature recording section from the center of the heating spot, scanning speed, initial temperatures of the standards and test samples, power of the heating source), assessment criteria for acceptable levels of initial temperatures of the reference and studied samples and criteria for choosing the ratio of thermal conductivity of the reference and studied samples also leads to lower eniyu accuracy. In addition, when registering the initial temperature and the temperature of the heated surfaces of the samples with two temperature sensors without matching the signals from them in time, additional measurement errors may arise for samples with an initial temperature varying along the surface or during the transition when scanning from one sample to another due to that the sensors are spaced apart from each other along the scan line and record the temperature of various surface areas or even different samples.

The known method is implemented by the device [3], which is the closest to the variants of the claimed device and contains a platform for placing the studied and reference samples and a heating-registration unit, including a temperature sensor and a heating source of samples in the form of a lamp, laser or convective heating source, while the sensor the temperature is located so that the center of the surface area of the sample in which the temperature is recorded is located on the line of motion of the center of the heating spot with a distance of Nia X _0> 5 / K ^1/2.

 The known device also has the aforementioned disadvantages for the method. In addition, the device is characterized by significant time and complexity of the measurement process, which is associated with the use of reference samples for each measurement.

SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and apparatus for the rapid determination of the thermal conductivity of solid materials, in which by choosing the best combination of parameters of the measurement mode, including the dimensions of the heating spot and the temperature recording section, the lag of the center of the temperature recording section from the center of the heating spot, the scanning speed, power of the heating source, the distance between the lines on the surface of the samples along which the centers of the heating spot and the istratsii temperature sample surface, improve accuracy and provide thermal conductivity measurements of thermal conductivity detailed registration nonuniform distribution in each sample.

The specified technical result is achieved due to the fact that in the known method for determining thermal conductivity, including preparatory adjustment of the device to measurements, heating the surfaces of the samples under study when moving relative to each other the platform with the samples and the heating unit and recording the temperature of the samples, determining the maximum excess temperatures of the surfaces of the studied samples along the line of movement of the temperature recording section over the surface of the samples under study and determine the thermal conductivity of the studied samples according to the formula
λ = λ _R (T _R -T _R0 ) / (TT ₀ ) or
λ = λ _R (U _R -U _R0 ) / (UU ₀ ) (2)
where λ is the thermal conductivity of the test sample, λ _R is the thermal conductivity of the reference sample, T and T _R are the excess temperature limits of the test and reference samples; T ₀ and T _R0 are the initial temperatures of the studied and reference samples, U _R and U are the values of the electrical signals of the temperature sensor corresponding to the heating temperatures of the reference and studied samples, U _R0 and U ₀ are the values of the electrical signals of the temperature sensor corresponding to the initial temperatures, respectively, of the reference and of the studied samples, in the process of preparatory adjustment of the device for measurements, set the width L in the range between its minimum and maximum values of L ₁ and L ₂ , which are selected within 0.01 <L ₁ / L ₂ <1, and the width L _{2 is} chosen smaller than the distance x ₀ from the center of the temperature recording section to the center of the heating spot, and the width l of the temperature recording section is set in the range between its minimum and maximum values l ₁ and l ₂ , which are selected in the range of 0.001 <l ₁ / l ₂ <1, while the width l _{2 is} chosen smaller than the distance x ₀ from the center of the temperature recording portion to the center of the heating spot, and within the limits of the width of the heating spot L enter more than 60% of the useful power of the heating source, and within the width l of the section p temperature recordings concentrate more than 60% of the useful signal of the temperature sensor 12, and also carry out mutual displacement of the lines along which the heating spot and the temperature recording section move along the surfaces of the samples, choosing the optimal distance between them to achieve the minimum effect on the thermal conductivity measurements of the shape of the heating spot and the section recording temperature.

 It is advisable in the preparatory setup of the device for measurements to form a set of reference samples with various known values of thermal conductivity and thermal diffusivity, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples, determine the heating levels of the reference samples, and then use the data on the heating level of the reference samples when determining thermal conductivity of the studied samples.

 It is also possible that in the process of preparatory adjustment of the device for measurements, a set of reference samples with various known values of thermal conductivity and thermal diffusivity is formed, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples. Further, in the process of determining the thermal conductivity of the test samples, the heating levels of the reference samples are determined, and data on the heating level of the reference samples are used to determine the thermal conductivity of the test samples.

 In the process of preparatory adjustment of the device to measurements, comparative measurements of thermal conductivity are also carried out on reference samples with the same or similar thermal conductivity, but significantly different in thermal diffusivity, and, taking into account the degree of influence of thermal diffusivity on the measurement results, the parameters of the thermal conductivity measurement mode are changed, achieving the least influence of thermal diffusivity on the measurement results thermal conductivity, and thereby determine the optimal parameters of the device oystva.

The technical result is also achieved by using in the invention a device for the rapid determination of the thermal conductivity of solid materials, containing a platform for placing test and reference samples, a heating and recording unit, including a heating source for samples and a temperature sensor, while the platform with samples and the heating and registration unit are installed with the possibility displacements relative to each other, the heat source or the shaper of the heating spot and the temperature sensor or optical communication element positioned relative to each other with the possibility of moving one after the other along the line of movement of the temperature recording section over the surface of the samples, characterized in that the heating and registration unit contains a heating spot former and / or an optical communication element, while in the heating and recording unit there is a heating source or former heating spots and a temperature sensor or optical coupling element are installed at such a distance from the surface of the samples and at such an angle relative to the surface of the samples, and radiation from and source of heat for the samples and the radiation from the sample to the sensor temperature is focused or limited in size and shape so that the width L is reached the heating spot in the range between its minimum and maximum value L ₁ and L _2, which are selected in the range 0.01 <L ₁ / L ₂ <1, and the width L _{2 is} chosen smaller than the distance x ₀ from the center of the temperature recording portion to the center of the heating spot, and the width l of the temperature recording portion in the range between its minimum and maximum values l ₁ and l ₂ , which selected within 0.001 < l ₁ / l ₂ <1, while the width l _{2 is} chosen smaller than the distance x ₀ from the center of the temperature recording section to the center of the heating spot, more than 60% of the useful power of the heating source being introduced within the width L of the heating spot, and within the width l of the temperature recording section, more than 60% of the useful temperature sensor signal is concentrated, the design parameters of the heating and recording unit are determined on the basis that the distance x ₀ from the center of the temperature recording section to the center of the heating spot is selected with respect to the minimum length e l _0min the test and reference samples within the (d _1/2 + d _2/2) <x ₀ <41 _0min, where d ₁ - spots length heating along a line of movement, d ₂ - the length of the temperature registration along the line of motion, l _{0min is} selected in the range from 1 to 2000 mm, to ensure the required quality of the results, the relative velocity of the samples is selected in the range from 0.1 to 300 mm / s, the length d ₁ of the heating spot is selected from the condition d ₁ <l _min , and the length d ₂ plot temperature registration is selected from the condition d ₂ <l _min .

 The device also includes a set of reference samples with different values of thermal conductivity and thermal diffusivity, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples so that the thermal conductivity and thermal diffusivity ranges of the studied and reference samples coincide or are close.

 The device can be made so that between the samples and the platform are insulating gaskets or its platform is made of insulating material.

 According to the invention, the device can be configured such that the heating and recording unit comprises an additional temperature sensor and / or an additional optical connection element for the temperature sensor with the surface of the samples, as well as a time delay unit for the signal corresponding to the initial temperature of the samples relative to the signal corresponding to the temperature of the heated surface samples, while the heating source or the shaper of the heating spot in the heating and registration unit are located between the main and additional sensor temperature or the main and additional elements of optical communication, and the signal delay time by the signal time delay unit is chosen equal to S / v, where S is the distance between the centers of the recording areas of the initial temperature and temperature of the heated surface of the samples, v is the speed of movement of the heating and registration unit relative to the samples .

 Preferably, the platform was made in the form of a two-coordinate table with the ability to move in mutually perpendicular directions.

 The platform may contain a mechanism for its movement in the longitudinal direction, and the heating and registration unit is mounted on a carriage located on the frame, with the possibility of moving the frame in the transverse direction relative to the platform.

 The platform may contain a mechanism for its movement in the transverse direction, and the heating and registration unit is mounted on the carriage on the frame, made with the possibility of moving the carriage along the frame in the longitudinal direction.

 It is possible to implement the device when, when the platform is stationary, the heating and registration unit is mounted on a carriage located on the frame, with the possibility of moving the carriage in the longitudinal direction along the frame, made with the possibility of its movement along the guides in the transverse direction relative to the platform.

 It is also envisaged that the heating and registration unit is mounted with the possibility of rotation around an axis perpendicular to the heated surface of the samples.

 The device is configured such that the heat spot former and / or optical communication elements of the temperature sensors with the surface of the samples are a fiber, and / or a lens, and / or a swivel mirror, and / or a prism.

 It is also possible to implement the device when the heating and registration unit is made with the possibility of oscillatory motion around an axis parallel to the surface of the platform and perpendicular to the plane passing through the line of location of the samples perpendicular to the surface of the platform.

 The device can be configured so that when a heating spot or a heat spot former and a temperature sensor or both temperature sensors or optical communication elements are placed in the heating and registration unit, all of them together and / or each of them are capable of performing their synchronous oscillatory movement with constant distances between the center of the heating spot and the centers of the temperature recording sections.

 The platform can be made in the form of a rotor wheel rotating relative to the heating and registration unit, while the studied and reference samples and the heating and registration unit can be located both on the outside of the rotor wheel and inside it.

 The platform can be made in the form of a closed tape rotating relative to the heating and registration unit.

It is possible to implement a device in which it is equipped with a source data storage unit containing information on the parameter q / (2πx ₀ ), where q is the net power of the heating source, x ₀ is the distance from the center of the temperature recording section to the center of the heating spot, or about the heating level reference samples, which are determined during the preparatory setup of the device for measurements, and connected electrically with the unit for recording and processing information.

BRIEF DESCRIPTION OF THE DRAWINGS
In the future, the invention is illustrated by specific examples of its implementation and the accompanying drawings, in which:
FIG. 1 depicts a functional diagram of a device for the rapid determination of thermal conductivity of solid materials,
FIG. 2 is a top view of the measuring unit of the device,
FIG. 3 is a view of a measuring unit of a device in which a heating and recording unit is mounted to rotate about an axis perpendicular to the surface of the platform (side view),
FIG. 4 - device with a fixed platform and moving in two mutually perpendicular directions heating and registration unit, top view,
FIG. 5 is the same as FIG. 4, view along arrow A,
FIG. 6 is an embodiment of a platform in the form of a rotor wheel (shown in section), rotating relative to the heating and registration unit, located, like the samples, inside the rotor wheel;
FIG. 7 is an embodiment of a platform in the form of a closed tape rotating relative to a heating and recording unit;
FIG. 8 - heating and registration unit with two temperature sensors;
FIG. 9 is a measuring unit with a heating spot former and optical communication elements of the temperature sensors with the surface of the samples.

где n - показатель преобразования температуры в регистрируемый сигнал, t₀ = 1/(4aK), t_0R=1/(4a_RK), α - температуропроводность исследуемого образца в возможном диапазоне ее значений, t - переменная интегрирования, τ - время, необходимое для достижения предельного значения температуры нагрева исследуемого и эталонного образцов, x, y - пространственные координаты - переменные интегрирования.BEST MODE FOR CARRYING OUT THE INVENTION
The method is as follows. Determine (for example, according to available data, using the reference book or by trial approximate measurements) the possible range of thermal diffusivity of the studied samples. Then, with the circular shape of the heating spot and with the normal law of density distribution of the useful (that is, actually absorbed by the heated sample) power of the heating source over the heating spot and with the rectangular shape of the surface temperature recording area of the samples, setting the error δλ of the thermal conductivity measurements, establish the concentration coefficient K of the heating source , dimensions b, c of the temperature registration platform, select the scanning speed v of the heating source and temperature sensor, the distance x ₀ from the center temperature recording to the center of the heating spot, allowable range of initial temperatures of the reference and test samples, a reference sample with thermal diffusivity α _R so that the relation

where n is the indicator of the conversion of temperature into a recorded signal, t ₀ = 1 / (4aK), t _0R = 1 / (4a _R K), α is the thermal diffusivity of the test sample in a possible range of its values, t is the integration variable, τ is time, necessary to achieve the limiting value of the heating temperature of the studied and reference samples, x, y - spatial coordinates - integration variables.

A reference sample with the necessary characteristics is selected from the available set. After that, a reference sample and one or more test samples are sequentially placed on a special platform, which were previously placed in conditions providing a specified range of their initial temperatures. A source of heating the surface of the samples and a temperature sensor is installed in front of the samples (in the case of using a contact temperature sensor, for example thermocouples, bring this sensor into contact with the surface of the samples during measurements) so that when scanning along the surfaces of the studied and reference samples, the centers of the heating spot and the recording area temperatures moved in one line. It is also possible the location of the heating source and temperature sensors under or above the samples, depending on the orientation of the heated surface. Then, the initial temperatures T _R0 and T _{0 of the} reference and test samples are measured, respectively. Initial temperatures can be determined, for example, by moving only a temperature sensor along the surfaces of these samples or using a separate initial temperature sensor located in front of the heating source and moved together with the heating source and temperature sensor during the measurement process. Then, the heating source of constant power and the temperature sensor, rigidly connected to the source and therefore having a constant lag distance, are moved at a constant speed along the surfaces of the standard and the test samples. In the process of heating, the limiting temperature T _R and T of the heated surface is recorded, respectively, for the reference sample and for each sample under study along the line of motion of the source. Then, the excess temperature is determined from the difference between the limiting heating temperature and the previously measured initial temperature, and the thermal conductivity of each of the test samples is calculated by the formula λ = λ _R (T _R -T _R0 ) / (TT ₀ ) or λ = λ _R (U _R - U _R0 ) / (UU ₀ ), (2) where: λ is the thermal conductivity of the test sample, λ _R is the thermal conductivity of the reference sample, T and T _R are the excess temperature limits of the test and reference samples, T ₀ and T _R0 are the initial temperatures of the test and reference samples, U _R and U are the values of the electrical signals of the temperature sensor atures corresponding to the heating temperatures of the reference and studied samples, U _R0 and U ₀ are the values of the electrical signals of the temperature sensor corresponding to the initial temperatures of the reference and studied samples, respectively.

 A set of reference samples with various known values of thermal conductivity and thermal conductivity is formed on the basis of the expected ranges of thermal conductivity and thermal diffusivity of the studied samples so that the thermal conductivity and thermal diffusivity ranges of the studied and reference samples coincide or are close.

Measurements can be carried out in such a way that the heating level of each reference sample, defined as the excess limiting heating temperature T _R -T _R0 or the corresponding voltage difference U _R -U _R0 , will be determined in advance during the preparatory setup of the device for measurements. Further, keeping the useful power q of the heating source constant, the distance x ₀ from the center of the temperature recording section to the center of the heating spot and other parameters of the measurement mode, when measuring the thermal conductivity of the samples to be studied, only excess heat limit temperatures TT _{0 of} the samples to be studied or the corresponding voltage differences UU ₀ and then determine the thermal conductivity of the test samples according to one of the formulas (2), using predefined data on the heating level of the reference samples. The choice of a reference sample and determination of the optimal parameters of the measurement mode is the same both in the case of determining the level of heating of reference samples during the preparatory setup of the device for measurements, and in determining this level together with the level of heating of the studied samples in the case of sequential heating of the studied and reference samples with their simultaneous placement in one series on the platform.

 Relation (3) is justified as follows.

Actually, when measuring thermal conductivity, the following from relations (2) is used, which follows from formula (1):
λ = λ _R (T _R -T _R0 ) / (TT ₀ ) = λ _R (U _R -U _R0 ) / (UU ₀ ). (4)
When recording the initial temperature T ₀ at the elementary site dx • dy of the surface of the studied or reference samples, the recorded electrical signal dU ₀ is determined by the ratio
dU ₀ = CT ₀ ⁿ dx • dy + B, (5)
where B, C, n are constants determined by the characteristics of a particular measuring device; T ₀ - absolute temperature in kelvins.

(8)
куда вместо Θ можем подставить с использованием данных работы (Рыкалин Н.Н. Расчеты тепловых процессов при сварке. М., Машгиз, 1951, с. 167):

где q - полезная мощность источника тепловой энергии.When registering the temperature of the heated bodies T ₀ + Θ, where Θ is the excess temperature limit, the change in the signal recorded at the elementary site dx-dy is determined by the relation
dU-dU ₀ = C (T ₀ + Θ) ⁿ dxdy-CT $\genfrac{}{}{0ex}{}{\text{n}}{\text{0}}$ dx • dy. (6)
Since the condition Θ ≪ T _{0 is} satisfied under real conditions, it follows from (6)
d (UU ₀ ) = Cn (T ₀ ) ^n-1 θ • dx • dy. (7)
Then the total increment of the signal UU ₀ from the temperature recording site, characterized by linear dimensions b, c, when the temperature changes from T ₀ to T ₀ + θ is

(eight)
where instead of Θ we can substitute using the data of work (Rykalin N.N. Calculations of thermal processes during welding. M., Mashgiz, 1951, p. 167):

where q is the net power of the heat source.

The value U _R -U _R0 for the reference sample is determined similarly, which can be written by the relation corresponding to relation (8) taking into account expression (9) and substituting the parameters of the reference sample T _R0 , λ _R , α _R instead of the corresponding parameters of the studied sample.

(10)
где λ′ - фактический результат измерений теплопроводности, λ - действительная теплопроводность образца. Подставляя в (10) вместо λ′, согласно (4),

(11)
а вместо λ, согласно /2/,

(12)
где, согласно /2/,
T_R-T_R0 = q/(2πλ_Rx₀), (13)
T-T₀ = q/(2πλx₀), (14)
и заменяя U_R-U_R0 и U-U₀ на выражения (8) с использованием (9), получаем, в соответствии с (10), соотношение (3).The relative systematic error in the measurements of thermal conductivity δλ is determined from the relation

(10)
where λ ′ is the actual result of measurements of thermal conductivity, λ is the actual thermal conductivity of the sample. Substituting in λ (10) instead of λ, according to (4),

(eleven)
and instead of λ, according to / 2 /,

(12)
where, according to / 2 /,
T _R -T _R0 = q / (2πλ _R x ₀ ), (13)
TT ₀ = q / (2πλx ₀ ), (14)
and replacing U _R -U _R0 and UU ₀ with expressions (8) using (9), we obtain, in accordance with (10), relation (3).

 In the case of an arbitrary distribution of the useful power density over the heating spot, an arbitrary shape of the heating spot, and in the case of an arbitrary shape of the registration surface temperature of the samples, the excessive width of the heating spot, i.e. the size of the heating spot in the direction perpendicular to the direction of movement, or scanning the heating spot along the surface of the samples, and excessive width of the surface temperature recording portion of the samples, i.e., the size of the temperature recording portion in a direction perpendicular to the direction movements or scans on the surface of the samples can lead to unacceptable errors in the measurements of thermal conductivity due to deviations of the idealized relations (13), (14) from the more real relation (9), while the dimensions of the heating spot and the temperature recording section in the scanning direction are less critical , which follows from relations (13) and (14) and the principle of superposition of temperature fields. At the same time, an excessively small width of the heating spot leads to unacceptable overheating of the samples, and with a decrease in the source power, to an unacceptably low level of the heating temperature in the region of its registration behind the source and an unacceptably small signal-to-noise ratio for the temperature sensor. An excessively small width of the registration section leads to an unacceptable effect of individual protrusions of the surface roughness on the temperature sensor readings, as well as to an excessively low level of the temperature sensor signal and an unacceptably small signal-to-noise ratio for the temperature sensor.

Therefore, in the process of preparatory adjustment of the device to measurements, which is carried out before putting the device into operation, set the width L of the heating spot in the range between its minimum and maximum values of L ₁ and L ₂ which are selected in the range of 0.01 <L ₁ / L ₂ <1 while choosing L ₂ less than x ₀ . The width l of the temperature recording portion is set in the range between its minimum and maximum values of l ₁ and l ₂ , which are selected in the range of 0.001 <l ₁ / l ₂ <1, while l ₂ less than x ₀ is selected. At the same time, it is important that it is the middle part of the heating spot that provides the main heating of the samples; therefore, the heating spot is formed so that at least 60% is introduced into the samples within its width L (within the middle part of the width L of the heating spot with undefined boundaries of the heating spot) net power of the heating source. It is necessary that the middle part of the temperature registration section mainly provides a recorded signal characterizing the temperature of the heated surfaces of the samples, therefore, the temperature registration section is formed so that within its width l (within the middle part of the width l of the temperature registration section at undefined boundaries of the temperature registration section) At least 60% of the useful temperature sensor signal was concentrated. Mutual displacement of the lines is also carried out along which the heating spot and the temperature recording section move along the surfaces of the samples, choosing the optimal distance between them to achieve the minimum effect on the thermal conductivity measurements of the shape of the heating spot and the temperature recording section.

 In the case where the measurement conditions make it possible to have a circular shape of the heating spot, under the normal law of the distribution of the power density of the heating source over the heating spot and the rectangular shape of the sample temperature recording section (this case was discussed above), the center of the heating spot and the center of the temperature registration section are moved lines.

 In the case of an arbitrary distribution of the useful power over the heating spot, an arbitrary shape of the heating spot, and in the case of an arbitrary shape of the temperature recording area, there is a need for mutual displacement of the lines along which the heating spot and temperature registration section move on the surface of the studied and reference samples, and in choosing the optimal distance between them until the minimum effect on the results of measurements of thermal conductivity of an imperfect shape of the heating spot and the temperature recording area is achieved.

 To conduct thermal conductivity measurements and carry out preparatory adjustment of the device to measurements, a set of reference samples is formed with various known values of thermal conductivity and thermal diffusivity, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples so that the ranges of thermal conductivity and thermal diffusivity of the studied and reference samples coincide or are close .

It is possible to carry out measurements without using reference samples during each measurement process. In this case, during the preparatory operation, the parameter q / (2πx ₀ ) is determined. This parameter can be determined, for example, by measuring the values of q and x ₀ . According to relation (13), this parameter is equal to the value of the parameter λ _R (T _R -T _R0 ), therefore, from its value from formula (2), we can determine the thermal conductivity of the samples under study by determining the excess temperature limit TT ₀ . Subsequently, when heating the samples under study, the heating source determines the values of their excess limiting temperatures TT ₀ , using data on the value of the parameter q / (2πx ₀ ). Then, using formula (2), substituting the parameter q / (2πx ₀ ) instead of the parameter λ _R (T _R -T _R0 ), the desired values of the thermal conductivity of the studied samples are calculated.

In another case, during the preparatory operation, the level of heating of the reference samples is determined from the excess temperature limit T _R -T _R0 . In this case, by scanning each of the set of reference samples, the heating level is determined for each of them in the form of an excess temperature limit T _R -T _R0 . Subsequently, using the heating and registration unit, the studied samples are heated, their heating level is determined in the form of excess temperature limits TT ₀ . After that, the previously obtained data on the heating levels of the reference samples are used in the form of the parameter T _R -T _R0 , choosing the reference sample that is closest in thermal conductivity to the test sample and meets condition (3). Then, using the formula (2), the desired values of the thermal conductivity of the samples are calculated.

Instead of determining the excess temperature limit T _R -T _R0, it is possible to determine the level of heating of the reference samples from the corresponding voltage difference U _R -U _R0 or equivalent electrical value. To do this, by scanning each of the set of reference samples, the voltage difference U _R -U _R0 (or equivalent electrical value) is determined for each of them. Subsequently, using the heating and registration unit, the samples under study are heated, their heating level is determined by recording the UU ₀ value or an equivalent electric value for the samples under study. After that, information on the voltage difference U _R -U _{R0 is used} for the reference sample that is closest in thermal conductivity to the test sample and meets condition (3). Then, using the formula (2), the desired values of the thermal conductivity of the samples are calculated.

 In another case of measurements, one or more reference samples from the generated set of reference samples are placed on the platform together with the samples to be studied, the samples are heated sequentially using a heating and recording unit, recording their level of heating (equal to or proportional to their maximum excess temperatures) using a heating unit and registration and determine the thermal conductivity of the studied samples using one of the formulas (2).

For a more accurate determination of the optimal parameters of the measurement mode (dimensions of the heating spot and temperature recording section, distance x ₀ from the center of the temperature recording section to the center of the heating spot, scanning speed, initial temperatures of standards and test samples, net power of the heating source, distance between lines on the surface samples along which the heating spot and the registration area of the surface temperature of the samples move) in the process of preparatory setup of the device for measurements, it is necessary carry out comparative measurements on the thermal conductivity of the reference samples with the same or close thermal conductivity, but differ significantly in thermal conductivity. From relations (13) and (14), which are the basis of relation (2), it follows that thermal diffusivity should not affect the measurement results if a point heating spot, a point temperature recording section, exact coincidence of the scanning lines of the heating spot and the temperature recording section are used , exclude the influence of heat transfer to the environment. However, this cannot be achieved with real measurements, therefore, the measurement results for samples with the same thermal conductivity but different thermal diffusivity will be different and larger, the more the measurement mode parameters differ from the optimal ones. Therefore, in advance, for various parameters of the measurement mode, conductivity measurements are carried out on samples with the same or similar thermal conductivity and different thermal diffusivity (with a difference of not less than 5%) in the entire range of thermal conductivity of the samples under study for different parameters of the measurement mode. The parameters of the measurement mode, at which the smallest effect of thermal diffusivity on the results of measurements of thermal conductivity is achieved, is chosen as the optimal parameters of the measurement mode.

 A device for determining the thermal conductivity of solid materials (Fig. 1) includes a measuring unit 1, an information recording and processing unit 2, a scanning speed change unit 3, a signal delay time unit 4, a source data storage unit 5.

 The measuring unit 1 of the device for determining the thermal conductivity of solid materials (Fig. 2, 3) in general contains a working table 6, on which a platform 7 is installed for placing the test and reference samples 8 and 9, respectively, and a heating and recording unit 10 containing a source 11 heating, which can be used as a lamp, laser, contact or jet source, and at least one temperature sensor 12. In this case, the platform 7 can be made in the form of a two-coordinate table with the ability to move in two mutually perpendicular directions along the longitudinal (along the line of movement of the heating and registration unit 10 during measurements) and transverse (perpendicular to the line of movement of the heating and registration unit 10 during measurements) guides 13 and 14, respectively.

 To avoid excessive heat removal from the studied and reference samples 8 and 9 into the material of the platform 7, which entails a deviation of the theoretical assumptions, the platform 7 is made of heat-insulating material, or heat-insulating gaskets 16 are placed between the platform 7 and samples 8 and 9 so that the samples 8 and 9 did not contact directly with platform 7.

 Depending on the design features of the implementation of the tasks, various combinations of mutual movement of the platform 7 and the heating and registration unit 10 are possible. For example, if the heating and registration unit 10 is stationary, then in this case the platform 7 is movable in two mutually perpendicular directions along the longitudinal and transverse guides 13 and 14. If the platform 7 is stationary, then the heating and registration unit 10 should be configured to move in two mutually perpendicular directions relative to the platform (see Fig. 4 and 5); in this case, the heating and registration unit 10 can be placed on the carriage, which moves in the longitudinal direction along the frame 15, which is arranged to move in the transverse direction relative to the platform 7 along the guides 14. If the platform 7 is made movable in the longitudinal direction, along the line of location of the studied and reference samples 8 and 9, the heating and recording unit 10 can be located on the frame 15, which is configured to move along the transverse guides 14; if the platform 7 is made movable in the transverse direction, then the heating and registration unit 10 can be located on the carriage, which is movably placed on the frame 15 and can move along it in the longitudinal direction. The studied and reference samples 8 and 9 can be located on heat-insulating gaskets 16, or the platform 7 itself is made of heat-insulating material.

 The platform 7 can also be made in the form of a closed loop, for example, a circle in the form of a rotor wheel, an ellipse, a rectangle, and is oriented horizontally or vertically, like a horizontal or vertical carousel, a closed conveyor belt, which will provide a continuous measurement process with non-stop unilateral movement of the platform 7 relative to the block 10 heating and registration or block 10 heating and registration relative to the platform 7.

 In FIG. 6 shows a device with a platform 7 (in section) made in the form of a rotor wheel 17, with a heating and recording unit 10 and test and reference samples 8 and 9 located together with a heating and recording unit 10 inside the rotor wheel 7, driven by a drive 18. The heating and registration unit 10 and the test and reference samples 8 and 9 can also be located on the outside of the rotor wheel 7. A variant of the device with the rotation of the heating and registration unit 10 relative to the rotor wheel 17 is possible.

 In FIG. 7 shows a device for the rapid determination of the thermal conductivity of solid materials with a platform made in the form of a closed tape 19, with a heating and registration unit 10 and test and reference samples 8 and 9 located outside the tape 19, driven by a drive 20.

 The listed combinations allow scanning the heating spot from the heating source 11 over the surface of samples 8, 9 with the corresponding scanning of the surface of samples 8, 9 by the temperature sensor 12 and thereby solve the problem of detecting the heterogeneity of the thermal conductivity of the studied samples 8. The measurement performance also increases, since on platform 7 it is possible place a significant number of test samples 8 in several rows (Fig. 2).

 As the heating source 11, a non-contact optical, convective, or contact surface heating source of samples 8, 9 can be used.

 In the block 10 heating and registration can also be used various elements that control the direction of movement of the light, in particular the laser beam, which is the output node of the fiber, a lens, a prism, a crystal, a mirror; a system of lenses, and / or prisms, and / or mirrors, and the like, optically coupled to a heating source 11, for example, a laser that is located outside the heating and recording unit 10 (see FIGS. 4 and 5).

 To improve the speed of the device, the heating and registration unit 10 may include an additional temperature sensor 21 (Fig. 8), which is located in front of the heating source along the direction of the heating and registration unit 10. The additional temperature sensor 21 can be made so that in its optoelectrical characteristics it is similar to the main temperature sensor 12. In this case, after the completion of one measurement cycle performed with the one-way movement of the platform 7, a new cycle is carried out when the platform 7 or the heating and recording unit 10 moves in the opposite direction. In this case, the functions of the main temperature sensor 12 and the additional temperature sensor 21 are changed. In this case, the main temperature sensor 12 will be used to record the initial temperatures of the studied and reference samples 8 and 9, and an additional temperature sensor 21 will record their temperature limits. At different distances from the center of the heating spot to the center of the temperature recording sections of the sensors 12 and 21 and when repeating measurements with the opposite direction of movement of the heating and recording unit 10 for the same inhomogeneous test samples 8, it becomes possible to change the depth of measurement to obtain additional information about the structure of the test samples 8 (thermal tomography).

 In FIG. 9 shows the measuring unit 1, in which the heating and recording unit 10 is made with a heating spot driver 24 and optical sensors 25 and 26 for optical temperature sensors to connect to the surface of samples 8 and 9 (hereinafter referred to as optical communication elements) associated with sensors 12 and 21 temperatures established stationary outside the heating and recording unit 10 and interacting with the surface of samples 8 and 9 through the optical coupling elements 25 and 26. The optical coupling elements 25 and 26 and the heating spot generator 24 are connected to the temperature sensors 12 and 21 and the heating source 11 by the optical coupling lines 27, 28 and 29. It is also possible that the optical communication lines 27 and 28 connect the optical communication elements 25 and 26 not with two temperature sensors 12 and 21, but only with one temperature sensor 12 or 21, while the temperature sensor 12 or 21 alternately at small time intervals (shorter than the minimum scan time of one sample 8 and 9) is connected to the optical communication lines 27 and 28.

 The movement of the platform 7 in the longitudinal direction is carried out (see Fig. 2) using the mechanism 30 for the longitudinal movement of the platform 7, and in the transverse direction using the mechanism 31 for the transverse movement of the platform 7.

 If the platform 7 is stationary (see Fig. 4 and 5), then the heating and registration unit 10 is mounted on the carriage on the frame 15 with the possibility of moving the carriage along the frame 15 in the longitudinal direction, while it is possible to move the frame 15 along the guides 14 in the transverse direction.

 In FIG. 4 and 5 show one of the possible optical connections between the heating source 11 and the surface of the studied and reference samples 8 and 9 through focusing elements that control the direction of the light or laser beam, presented in the form of two rotary mirrors 22 and 23 that direct the light or laser beam on samples 8 and 9. The mirror 22 is fixed by means of a bracket at one of the ends of the frame 15. When moving the heating unit 10 and registering on the carriage along the frame 15 in the longitudinal direction along the samples 8 and 9, the laser radiation and 11 will always fall on the mirror 22 and reflected on a mirror 23 installed in the heating unit 10 and the registration. Reflecting from the rotary mirror 23, the laser beam hits the surface of samples 8 and 9, carrying out their heating.

The achievement of the technical result by the device is ensured by the fact that in the heating and recording unit 10, the heating source 11 and the temperature sensor 12 are installed at such a distance from the surface of samples 8 and 9 and at such an angle relative to the surface of samples 8 and 9, and radiation from the heating source 11 to samples 8 and 9 and the radiation from samples 8 and 9 to the temperature sensor 12 is focused or limited in area and in the shape of the heating spot and in the area and shape of the temperature recording area so that within the part of the spot the heating Whose width is set to L, the sample is introduced over 60% of the useful power of the heat source, and within the zone width l temperature detecting portion are more than 60% of the useful temperature sensor. At the same time, the width L of this part of the heating spot was achieved in the range between its minimum and maximum values L ₁ and L ₂ , which were selected within 0.01 <L ₁ / L ₂ <1, and the width L _{2 was} chosen smaller than the distance x ₀ from the center of the temperature recording portion to the center of the heating spot. The width l of the zone or part of the temperature recording portion is achieved in the range between its minimum and maximum values of l ₁ and l ₂ , which are selected in the range 0.001 <l ₁ / l ₂ <1, while the width l _{2 is} chosen smaller than x ₀ . The dimensions of the heating spot and the temperature recording portion in the scanning direction should be selected so that overlapping of the heating spot and the temperature recording portion is avoided. Therefore, the design parameters of the heating and recording unit 10 are determined on the basis that the distance x ₀ from the center of the temperature recording region to the center of the heating spot is selected with respect to the minimum length l _{0min of the} studied and reference samples 8 or 9 in the range (d _1/2 + d _2/2 ) <x ₀ <41 _0min , where d ₁ is the length of the heating spot along the line of movement along the line of motion of the heating spot and the temperature recording section, d ₂ is the length of the temperature recording section along the movement line of the heating spot and temperature recording section, while value l _{0min is} selected between 0.5 and 2000 mm. The length of the heating spot d _{1 is} selected from the condition d ₁ <l _min , and the length of the temperature recording portion is selected from the condition d ₂ <l _min .

When the length of the samples 8 and 9 is less than 1 mm, it is impossible to implement the proposed method for measuring thermal conductivity using known temperature sensors and heat sources. With a sample length of more than 2000 mm, the elements of the device become excessively large and unrealistic for their implementation. At x ₀ values greater than 41 _0min, the heating temperature of the studied and reference samples 8 and 9 does not reach its limit value, which is necessary for determining the thermal conductivity of the studied samples 8 according to relation (2). To ensure the necessary accuracy of measurements of thermal conductivity, which is representative enough for heterogeneous samples 8, to achieve the required depth of measurements, to distinguish the boundaries of areas with variable thermal conductivity, to exclude overheating of samples 8 and 9 in the heating spot, to ensure the temperature level of the heated surfaces of samples 8 and 9, sufficient to reliable registration, the relative velocity of samples 8 and 9 is selected in the range from 0.1 to 300 mm / s. As practice shows, the power q of the heating source 6 should be selected within 0.01 <q <1000 watts.

 The heating and recording unit 10 may include a non-contact - optical, or convective, or contact heating source 11 of samples 8 and 9. An embodiment of the heating and recording unit 10 is possible, in which it includes a former 24 of the heating spot for samples 8 and 9, which is the output node of the fiber, and / or a lens, and / or a prism, and / or a mirror, a system of lenses, prisms, mirrors, optically coupled to a heating source 11, for example, a laser, which is located outside the heating and registration unit 10. One embodiment of optical communication is shown in FIG. 4 and 5. The heating and recording unit 10 may also contain (Fig. 9) one or two optical communication elements 25 and / or 26 in the form of a light guide (for example, in the form of a flexible optical fiber), and / or a lens, and / or a mirror , and / or prisms, and / or systems of lenses, mirrors, prisms, which form a temperature recording area on the surface of samples 8 and 9 with non-contact recording of the temperature of samples 8 and 9 from the optical radiation of their surface.

 The device includes a set of reference samples 9 with various known values of thermal conductivity and thermal diffusivity, the range of which is selected based on the possible ranges of thermal conductivity and thermal diffusivity of the studied samples 8 so that the thermal conductivity and thermal diffusivity ranges of the studied and reference samples 8 and 9 coincide or are close. When conducting measurements of the thermal conductivity of the studied samples 8, certain reference samples 9 from this set (one, two or several) are selected and installed on the platform 7 with the tested samples 8. The selection of the reference samples 9 is carried out so that their thermal conductivity and thermal conductivity are close to thermal conductivity and thermal diffusivity samples 8 and based on the required signal-to-noise ratio for the signals of temperature sensors 12 and 21 and the associated random measurement error, acceptable level the systematic measurement error, the permissible heating level of the reference and studied 9 and 8 samples, the required measurement performance, and also taking into account relation (3). To increase the accuracy of measurements, not one, but two or more reference samples 9 of the same or different thermal conductivity are installed on the platform 7, the characteristics of which are close to the thermal conductivity and thermal conductivity of the studied samples and meet the above conditions, while the thermal conductivity of the studied samples 8 is determined independently for each of the reference samples 9 using the formula (2) followed by averaging of the measurement results. This allows, firstly, to take into account possible fluctuations in the power of the heating source 11, the sensitivity of the temperature sensors 12 and 21 and other parameters of the device during the cycle of measuring the thermal conductivity of the studied samples 8, placed on the platform 7, and, secondly, to reduce the random error of the thermal conductivity measurements .

 The device can be equipped with a node 3 changes the scanning speed (Fig. 1). In this case, the achievement of optimal parameters of the measurement mode (the shape and dimensions of the heating spot, the distance of the lag of the heating spot from the temperature registration area, the shape and size of the temperature registration area, scanning speed, thermal conductivity and thermal diffusivity of the reference samples 9, the relative position of the scanning lines of the heating spot and the recording area temperature) is provided during the preparatory setup of the device for measurements using control measurements of the thermal conductivity of some reference voltages aztsov 9 by comparing them with other reference samples 9, each time using different scanning speeds, that is, the movements of the heating and recording unit 10 relative to samples 8, 9, which under real measurement conditions affects excess temperature limits (see Rykalin N. N Calculation of thermal processes during welding. M., Mashgiz, 1951, p. 167). Carrying out control measurements at various scanning speeds, the optimal parameters of the device are selected by achieving the least effect of the scanning speed on the results of control measurements and the best fit of the results of control measurements to the real values of thermal conductivity of the reference samples 9.

 The determination of the optimal parameters of the regime is carried out on the basis of specific features and conditions for measuring thermal conductivity. So, the choice of the parameter L close to its maximum possible value allows you to use a higher power q of the heating source 11 without overheating of the investigated and reference samples 8 and 9, thereby increasing the temperature in the region of its registration, which improves the signal-to-noise ratio of temperature sensors 12 and 21 and reduces the random measurement error, but at the same time increases the systematic measurement error. A decrease in L reduces the systematic measurement error, since it brings the heating spot closer to the point spot, but at the same time leads to an increase in the energy density in the heating spot and an increase in the maximum heating temperature of samples 8 and 9, which can lead to their destruction or unacceptable changes.

 An increase in the power q of the heating source 11 increases the accuracy of the measurements, since this increases the temperature in the recording area and improves the signal-to-noise ratio of the temperature sensors 12 and 21, however, this can destroy or impermissible thermal change of the studied or reference samples 8 and 9. Together with Therefore, in studies of water-saturated samples 8, this leads to increased moisture migration, evaporation of the saturating fluid, which reduces the accuracy of the measurements. A decrease in q reduces the accuracy of measurements in connection with a decrease in temperature in the region of its registration and a deterioration in the signal-to-noise ratio of temperature sensors 12 and 21, but ensures greater safety of samples 8 and 9 due to their lower heating and higher accuracy of measurements on moisture-saturated samples 8.

 An increase in the width l of the temperature recording section leads to an increase in the systematic error of thermal conductivity measurements, since the temperature is recorded not only on the heating line, as provided for in the calculation formula (2), but also at numerous points away from the heating line. At the same time, an increase in l makes it possible to improve the signal-to-noise ratio of the temperature sensors 12 and 21 and thereby reduce the random measurement error. A decrease in l reduces the systematic error in its absolute value, but at the same time increases the random measurement error, since it worsens the signal-to-noise ratio of the temperature sensors 12 and 21.

An increase in the distance x ₀ from the center of the temperature recording section to the center of the heating spot leads to an increase in the measurement depth, since this increases the penetration depth of thermal energy into the sample 4 from the heating source. An increase in x ₀ leads to a decrease in the systematic error of measurements of thermal conductivity, since in this case the deviation of the actual dimensions of the heating spot and the temperature registration region from idealized point ones becomes less significant, however, the random measurement error increases in this case, since the temperature in the registration region decreases. A decrease in x ₀ leads to an increase in the systematic error of measurements, but the random error in this case decreases due to an increase in temperature in the region of its registration. At the same time, a decrease in x ₀ causes a decrease in the depth of measurements, which reduces the reliability of the result for heterogeneous samples 8.

 An increase in the speed v of the movement of the heating and recording unit 10 relative to the studied and reference samples 8 and 9 leads to a decrease in the depth of measurements and an increase in the systematic error of measurements, since the influence of the difference between the real heating spot and the temperature registration area from idealized point ones increases, while the measurement performance increases. At the same time, the maximum temperature of samples 8 and 9 in the heating spot decreases. A decrease in the speed v of the movement of the heating and recording unit 10 causes an increase in the depth of measurements and an increase in their accuracy, but reduces the measurement performance and leads to overheating of samples 8 and 9 in the heating spot, which is unacceptable for moisture-saturated and non-heat-resistant test samples 8.

 To further reduce the systematic error of thermal conductivity measurements, the device is implemented in such a way that the source data storage unit 5 contains the values of the systematic errors of thermal conductivity measurements depending on the measured value, which are entered into the source data storage unit 5 during the preparatory setup of the device for measurements and taken into account when comparing the limits excessive temperatures and in the processing of this data by the unit 2 registration and information processing. These values of systematic errors are determined once after the assembly of the device or when it is additionally configured using a set of reference samples 9 selected in the range of thermal conductivity of the studied samples 8 and having a thermal diffusivity selected in the middle of the range of possible values of thermal diffusivity of the studied samples 8. To do this, use the device control determinations of thermal conductivity of reference samples 9 from other reference samples 9 and the recorded difference between measured The real and actual values of the thermal conductivity of the reference samples 9 are determined as systematic measurement errors. Systematic measurement errors in the ranges between the thermal conductivity values of the reference samples 9 are determined by interpolation. The established values of systematic errors, depending on the measured value of thermal conductivity, are introduced into the block 5 for storing the initial data and taken into account in the form of corrections during measurements.

 When registering the temperature with electromagnetic radiation and heating the surfaces of the test and reference samples 8 and 9 with a light beam, their surfaces are preliminarily coated with a thin layer of the same substance (for example, enamel), which absorbs radiation well from the heating source 11 to align optical characteristics (absorption and emissivity) samples 8 and 9. Surfaces can be roughened for the same purpose.

 To increase the speed of the device, the heating and registration unit 10 may include a second temperature sensor 21 (Fig. 8) and / or a second element 26 for optical communication of the temperature sensor 12 or temperature sensor 21 with the surface of samples 8 and 9 (Fig. 9). The second temperature sensor 21 and / or the second optical communication element 26 of the temperature sensor 21 are located in front of the heating source 11 or the heating spot former 24 as the heating and registration unit 10 moves. The second temperature sensor 21 or the optical communication element 26 of the temperature sensor 21 with the surface of samples 8 and 9 can serve as a recorder of the initial temperature of samples 8 and 9. The second temperature sensor 21 and / or the optical communication element 26 of the temperature sensor 21 with the surface of samples 8 and 9 can also be made so that in their optoelectrical characteristics they are similar to the first temperature sensor 12 or the first optical communication element 25 of the temperature sensor 12. In this case, at the end of the measurement cycle, a new cycle is carried out when the heating and registration unit 10 moves in the opposite direction. At the same time, the functions of the temperature sensors 12 and 21 or the elements 25 and 26 of the optical connection of the temperature sensors 12 and 21 with the surface of samples 8 and 9 are changed with respect to recording the initial and limiting excess temperatures of samples 8 and 9.

To increase the productivity and accuracy of measurements, the device comprises a time delay unit 4 of the signal of the temperature sensor 21 or an optical communication element 26 of the temperature sensor 21 with the surface of samples 8 and 9 (hereinafter referred to as the time delay unit 4 of the signal) (Fig. 1). The signal delay time by the signal time delay unit 4 is selected to be S / v, where S is the distance between the centers of the recording sections of the initial temperature and the temperature of the heated surface of samples 8 and 9, v is the speed of the heating and recording unit 10 relative to samples 8 and 9. The delay is used so that the values of the limiting excess temperature T and T _R in each section of samples 8 and 9 can be determined taking into account the initial temperature T ₀ and T _{R0 of} this particular section. The delay is necessary due to the fact that the initial temperature within samples 8 and 9 can vary significantly (for example, due to the specific storage conditions of samples 8 and 9) before measurements, when working with water-saturated samples 8, when the cause of changes in the initial temperature is different the degree of fluid evaporation in different parts of sample 8. In addition, the delay eliminates the error that occurs during each measurement when switching from one sample 8 or 9 to another, when one temperature sensor is registered the initial temperature of the next sample, and yet another temperature sensor detects the temperature of the excess of the previous heating of the sample 8 or 9, in which the conditions different initial temperatures of samples may result in a significant reduction in the accuracy of measurements.

An additional temperature sensor 21 or optical communication element 26 may be made with optoelectrical characteristics different from the corresponding characteristics of temperature sensor 12 or optical communication element 25. In this case, the heating and recording unit 10 is performed in such a way as to enable its rotation by 180 ^° relative to the axis perpendicular to the heating plane of samples 8 and 9, so that when the platform 7 or the heating and recording unit 10 moves in the opposite direction, the temperature sensor 12 continues to measure the limiting heating temperatures, and an additional temperature sensor 21 would record the initial temperatures of samples 8 and 9. In this case, for each new cycle of measuring the thermal conductivity it is necessary to turn heating unit 10 and the register 180 ^o.

 Such a design of the heating and recording unit 10 is possible, which contains one temperature sensor or optical communication element, and between the temperature sensor or optical communication element and the surface of samples 8, 9 there is an optical element (for example, a mirror, prism, lens), oscillating or rotating in such a way that it provides alternating optical communication between the temperature sensor and the portion of the surface of the sample in front of the heating spot and the portion of the surface of the same sample behind the heating spot along the line the movement of the heating and recording unit 10 relative to samples 8 and 9, while the time interval between the transition from communication with one part of the surface (for example, in front of the heating spot) to another part of the surface (for example, behind the heating spot) should be less than the minimum time scanning one sample 8 and 9. This will allow one sensor to alternately take signals characterizing the temperature of the surface area of the sample before it is heated (initial temperature of the sample) and the temperature of the heated area (maximum temperature cheers after passing the heating spots). Thus, there is no need for a second temperature sensor to measure the initial temperature of the studied and reference samples 8 and 9. The electrical signal of the temperature sensor corresponding to the portion of the surface of the sample in front of the heating spot can be delayed by S / v, where S is the distance between the centers of the recording sections the initial temperature and the temperature of the heated surface of the samples 8 and 9, the v-speed of the block of heating 10 and registration relative to samples 8 and 9, using block 4 of the time delay of the signal.

 The heating and registration unit 10 can be made in such a way that its oscillatory movement is provided around an axis parallel to the surface of the platform 7 and perpendicular to the plane passing through the line of location of the samples 8 and 9 perpendicular to the surface of the platform 7. To ensure synchronization of the oscillatory motion, the heating unit 10 and registration as a whole or a heating source 11, and / or a heating spot generator 24, and a temperature sensor 12 and / or 21, or an optical communication element 25 and / or 26 of the temperature sensors 12 and 21 with the surface samples 8 and 9 are kinematically connected to operate a single drive mechanism of the synchronous oscillatory motion.

 The same structural elements can be kinematically connected with the drives of individual mechanisms of their oscillatory movement, while at least one of the mechanisms is connected to the drive speed control unit according to a program that ensures constant values of the distances from the centers of each of the temperature recording sections to the center of the spot heating up. To make it possible to study a larger surface area of inhomogeneous samples 8 and in order to obtain more reliable information about their thermal conductivity, the heating and registration unit 10 is mounted on a frame 15 transverse to the scanning direction of the laser beam on the surface of samples 8 and 9, with the block 10 moving heating and registration along the frame 15 (Fig. 4, 5). The frame 15 itself can be arranged to move along the longitudinal rails 14. In the latter case, the heating and recording unit 10 may further comprise a second temperature sensor 21 or an optical communication element 26 of the sensor 21 with the surface of samples 8 and 9, while the heating unit 10 itself and registration can be performed with the possibility of rotation around an axis perpendicular to the surface of samples 8 and 9. The thermal conductivity of inhomogeneous samples is measured by repeatedly scanning samples 8 and 9, before each measurement it is moving the frame 15 in the transverse direction.

The device can be implemented in such a way that the reference samples 9 are not used during each measurement process. In this case, only during the preparatory operation, the parameter q / (2πx ₀ ) is determined and introduced into the source data storage unit 5, into which information about the parameters of the measurement mode and the heating levels of the reference samples 9 is entered. This parameter can be determined, for example, by measuring q and x ₀ values. Subsequently, when heating the test samples 8 by the heating source 11, they determine the values of their excess temperature limits TT ₀ , registering them in the information recording and processing unit 2, use the data on the parameter q / (2πx ₀ ), translating it together with the data on the value of the excess temperature limits ₀ temperature TT of the storage unit 5 in the initial data unit 2 and the information registration processing which performs an automated registration heating levels test and reference samples 8, 9, the transmission of information in the storage unit iskho GOVERNMENTAL data, data processing and calculation of the thermal conductivity of the samples 8. Further, according to the formula (2), substituting it in place of the parameter λ _R (T _R -T _R0) parameter q / (2πx _0), the desired count value of thermal conductivity of the samples 8.

In another case, a similar implementation of the device during the preparatory operation determine the level of heating of the reference samples 9 from the excess temperature limit T _R -T _R0 . In this case, by scanning each of the set of reference samples 9, the heating level is determined for each of them in the form of an excess temperature limit T _R -T _R0 and introduced into the source data storage unit 5. Subsequently, using the heating and recording unit 10, the test samples 8 are heated, their heating level is determined in the form of excess temperature limits TT ₀ . After that, information stored on the heating levels of the reference samples 9 in the form of the parameter T _R -T _R0 stored in the storage unit 5 of the source data is used, selecting the reference sample 9 closest in thermal conductivity to the test sample 8, and this information is transferred from the source storage unit 5 data in block 2 registration and information processing. Then, using the formula (2), the desired values of the thermal conductivity of the studied samples 8 are calculated.

Instead of determining the excess temperature limit T _R -T _R0, it is possible to determine the heating level of the reference samples 9 from the corresponding voltage difference U _R -U _R0 or an equivalent electrical quantity. To do this, by scanning each of the set of reference samples 9, for each of them, the voltage difference U _R -U _R0 (or an equivalent electric value) is determined and entered into the source data storage unit 5. Subsequently, using the heating and recording unit 10, the test samples 8 are heated, their heating level is determined by recording the UU ₀ value or an equivalent electric value for the test samples 8. After that, the voltage difference information U _R - stored in the source data storage unit 5 is used U _R0 for the reference sample 9, which is the closest in thermal conductivity to the test sample 8, transferring this information from block 5 for storing the initial information to block 2 for recording and processing information. Then, using the formula (2), the desired values of the thermal conductivity of the studied samples 8 are calculated.

 These combinations allow you to scan the heating spot on the surface of the samples (and the corresponding scan of the temperature sensor) and thereby solve the problem of determining the heterogeneity of the thermal properties of the investigated materials. The measurement performance is also increased, since on the platform 7 it is possible to place a large batch of the studied samples 8 in several rows (see Figs. 2 and 3).

INDUSTRIAL APPLICABILITY
The proposed method and device allows to measure the thermal conductivity of solids in its wide range - from more than 0.06 to 250 W / m • K - with a total error of not more than 2.5% with a confidence level of 0.95.

 The high accuracy of the measurements of the proposed method and device allows you to use them to control the accuracy of measurements of the methods and devices used in practice for determining the thermophysical characteristics, as well as for the manufacture of reference samples.

SOURCES OF INFORMATION
1. Popov Yu.A. Some features of the application of the active thermal control method. "Defectoscopy", 1975, N 2, p. 56.

 2. Copyright certificate N 1032382. A method for determining the thermal conductivity of materials. Korostelev V.M., Popov Yu.A., Semenov V.G., Skornyakov S.M., Soloviev G.A. Bull. N 28, 07/30/1983.

 3. Popov Yu.A., Semenov V.G., Korostelev V.M., Berezin V.V. Non-contact determination of thermal conductivity of rocks using a movable heat source. Physics of the Earth, N 7, p. 86-93.

Claims (20)

1. A method for the rapid determination of the thermal conductivity of solid materials, including preparatory adjustment of the device to measurements, heating the surfaces of the samples (8) when moving relative to each other platform (7) with the samples (8) and the block (10) for heating and recording the temperature of the samples ( 8), the determination of the limiting excess temperatures of the surfaces of the studied samples (8) along the line of movement of the temperature recording section along the surface of the studied samples (8) and the determination of thermal conductivity and tracked samples (8) according to the formula
λ = λ _R (T _R -T _R0 ) / (TT ₀ ) (1)
or
λ = λ _R (U _R -U _R0 ) / (UU ₀ ) (2),
where λ is the thermal conductivity of the test sample;
λ _R is the thermal conductivity of the reference sample;
T and T _R are the excess temperature limits of the test and reference samples;
T ₀ and T _R0 are the initial temperatures of the investigated and reference samples;
U _R and U are the values of the electrical signals of the temperature sensor corresponding to the heating temperatures of the reference and the studied samples, respectively;
U _R0 and U ₀ - the magnitude of the electrical signals of the temperature sensor corresponding to the initial temperatures, respectively, of the reference and studied samples,
characterized in that during the preparatory setup of the device for measurements, the width L of the heating spot is set in the range between its minimum and maximum values L ₁ and L ₂ , which are selected within 0.01 <L ₁ / L ₂ <1, and the width L ₂ choose a smaller distance x ₀ from the center of the temperature recording portion to the center of the heating spot, and set the width l of the temperature recording portion in the range between its minimum and maximum values l ₁ and l ₂ , which are selected in the range 0.001 <l ₁ / l ₂ < 1, while the width l ₂ choose less than the distance x ₀ from the center of the temperature recording section to the center of the heating spot, more than 60% of the useful power of the heating source (11) is introduced within the width of the heating spot L, and more than 60% of the useful sensor signal is concentrated within the width l of the temperature recording section (12 ) temperatures, they also carry out mutual displacement of the lines along which the heating spot and the temperature recording section move along the surfaces of the samples, choosing the optimal distance between them until the minimum effect on the results is measured nd thermal conduction heating spot shape and temperature detecting portion.  2. The method for the rapid determination of the thermal conductivity of solid materials according to claim 1, characterized in that in the process of preparatory adjustment of the device for measurements, a set of reference samples is formed (9) with various known values of thermal conductivity and thermal diffusivity, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples (8), determine the heating levels of the reference samples (9) and then use the data on the heating level of the reference samples (9) when determined and thermal conductivity of the samples (8).  3. The method for the rapid determination of the thermal conductivity of solid materials according to claim 1, characterized in that during the preparatory adjustment of the device for measurements, a set of reference samples is formed (9) with various known values of thermal conductivity and thermal diffusivity, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples (8), in the process of determining the thermal conductivity of the studied samples (8) determine the heating levels of the reference samples (9), and use TED on reference samples heating level (9) for determining the thermal conductivity of the samples (8).  4. The method for the rapid determination of the thermal conductivity of solid materials according to claim 1 and any of claims 2 and 3, characterized in that during the preparatory setup of the device for measurements, comparative measurements of thermal conductivity are carried out on reference samples (9) with the same or similar thermal conductivity, but substantially differing in thermal diffusivity, and, taking into account the degree of influence of thermal diffusivity on the measurement results, change the parameters of the thermal conductivity measurement mode, achieving the least influence of thermal diffusivity range on the results of measurements of thermal conductivity, and thereby determine the optimal parameters of the operating mode of the device. 5. A device for the rapid determination of the thermal conductivity of solid materials, containing a platform (7) for placing test and reference samples (8, 9), a heating and recording unit (10), including a sample heating source (11) (8, 9) and a sensor ( 12) temperature, while the platform (7) with samples (8, 9) and the heating and recording unit (10) are mounted with the possibility of moving relative to each other, moreover, the heating source (11) and the temperature sensor (12) are located relative to each other with the ability to move one after another along the line of movement a temperature recording portion over the surface of the samples (8, 9), characterized in that the heating and registration unit (10) comprises a heat spot former (24) and an optical connection element (25) for the temperature sensor (12) with the surface of the samples (8, 9) in this case, in the heating and recording unit (10), the heating source (11) or the heating spot generator (24) and the temperature sensor (12) or the optical coupling element (25) are installed at such a distance from the surface of the samples (8, 9) and under such an angle relative to the surface of the samples (8, 9), and the radiation from the source (11) of heating is not and the samples (8, 9) and the radiation from the samples (8, 9) to the temperature sensor (12) are focused or limited in area and shape so that the width L of the heating spot is achieved in the range between its minimum and maximum values L ₁ and L ₂ , which are selected in the range of 0.01 <L ₁ / L ₂ <1, and the width L _{2 is} chosen smaller than the distance x ₀ from the center of the temperature recording portion to the center of the heating spot, and the width l of the temperature recording portion in the range between minimum and maximum values of l ₁ and l ₂ , which are selected in the range of 0.001 <l ₁ / l ₂ < 1, while the width l _{2 is} chosen smaller than the distance x ₀ from the center of the temperature recording portion to the center of the heating spot, more than 60% of the useful power of the heating source (11) being introduced within the width of the heating spot L, and within the width of the recording portion l more than 60% of the useful signal of the temperature sensor (12) is concentrated, the design parameters of the heating and recording unit (10) are determined on the basis that the distance x ₀ from the center of the temperature recording section to the center of the heating spot is selected with respect to the minimum ine l _0min the test and reference samples (8, 9) within the (d _1/2 + d _2/2) <x ₀ <4l _0min, where d ₁ - spots length heating along a line of movement, d ₂ - the length of the temperature detecting portion along the line of motion, l _{0min is} selected within the range of 1 - 2000 mm, to ensure the required quality of the results, the relative velocity of the samples (8, 9) is selected within 0.1 - 300 mm / s, the length d ₁ of the heating spot is selected from the condition d ₁ <l _min , and the length d ₂ of the temperature recording portion is selected from the condition d ₂ <l _min .  6. A device for the rapid determination of the thermal conductivity of solid materials according to claim 5, characterized in that it includes a set of reference samples (9) with various known values of thermal conductivity and thermal diffusivity, the range of which is selected based on the expected ranges of thermal conductivity and thermal diffusivity of the studied samples (8) so so that the ranges of thermal conductivity and thermal diffusivity of the studied and reference samples (8, 9) coincide or are close.  7. A device for the rapid determination of the thermal conductivity of solid materials according to claim 5 or 6, characterized in that the platform (7) is made of heat-insulating material.  8. A device for the rapid determination of the thermal conductivity of solid materials according to claim 5 or 6, characterized in that between the samples (8, 9) and the platform (7) there are heat-insulating gaskets (16).  9. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5 to 8, characterized in that the heating and recording unit (10) comprises an additional temperature sensor (21) and / or an additional optical communication element (26) of the temperature sensor (21) with the surface of the samples (8, 9), as well as the block (4) of the time delay of the signal corresponding to the initial temperature of the samples (8, 9), relative to the signal corresponding to the temperature of the heated surface of the samples (8, 9), while the source (11) of heating or shaper (24) heating spots in bl An oce (10) of heating and recording is located between the main (12) and additional (21) temperature sensors or the main (25) and additional (26) elements of optical communication, and the signal delay time by the signal delay unit (4) is selected to be S / v , where S is the distance between the centers of the recording areas of the initial temperature and the temperature of the heated surface of the samples (8, 9), v is the speed of movement of the heating and registration unit (10) relative to the samples (8, 9).  10. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5 to 9, characterized in that the platform (7) is made in the form of a two-coordinate table with the ability to move in mutually perpendicular directions.  11. A device for the rapid determination of thermal conductivity of solid materials according to claims 5 to 9, characterized in that the platform (7) contains a mechanism (30) for its movement in the longitudinal direction, and the heating and registration unit (10) is mounted on a carriage mounted on the frame (15), with the possibility of moving the frame (15) in the transverse direction relative to the platform (7).  12. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5 to 9, characterized in that the platform (7) contains a mechanism (31) for its movement in the transverse direction, and the heating and registration unit (10) is mounted on the carriage on the frame (15) ) configured to move the carriage along the frame (15) in the longitudinal direction.  13. A device for the rapid determination of thermal conductivity of solid materials in paragraphs. 5 - 9, characterized in that when the platform is stationary (7), the heating and registration unit (10) is mounted on a carriage located on the frame (15), with the possibility of moving the carriage in the longitudinal direction along the frame (15), made with the possibility of its movement along the guides (14) in the transverse direction relative to the platform (7).  14. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5 to 13, characterized in that the heating and recording unit (10) is mounted with the possibility of rotation around an axis perpendicular to the heated surface of the samples (8, 9).  15. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5-14, characterized in that the driver (24) of the heating spot and / or elements (25, 26) of the optical connection of the sensors (12, 21) of the temperature with the surface of the samples (8, 9) are a fiber, and / or a lens, and / or a swivel mirror, and / or a prism.  16. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5 to 15, characterized in that the heating and recording unit (10) is made with the possibility of oscillatory motion around an axis parallel to the surface of the platform (7) and perpendicular to the plane passing through the sample location line (8, 9) perpendicular to the surface of the platform (7).  17. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5-16, characterized in that when the heating source (11) or the heat generator (24) is placed in the heating unit (10) and the heat former (24) is equipped with a temperature sensor (12) or both temperature sensors (12, 21) or optical communication elements (25, 26), all of them together and / or each of them are configured to synchronously oscillate with constant distances between the center of the heating spot and the centers of the temperature recording sections.  18. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5 to 8, characterized in that the platform (7) is made in the form of a rotor wheel (17) rotating relative to the heating and registration unit (10), while the investigated and reference samples ( 8) and (9) and the heating and registration unit (10) can be located both on the outside of the rotor wheel and inside it.  19. A device for the rapid determination of thermal conductivity of solid materials according to claims 5 to 8, characterized in that the platform (7) is made in the form of a closed tape (19) rotating relative to the heating and registration unit (10). 20. A device for the rapid determination of the thermal conductivity of solid materials according to claims 5-19, characterized in that it is equipped with a source data storage unit (5) containing information on the parameter q / (2πx ₀ ), where q is the useful power of the source (11) heating, x ₀ is the distance from the center of the temperature recording section to the center of the heating spot, or about the heating level of the reference samples (9), which were determined during the preparatory setup of the device for measurements, and connected electrically to the information recording and processing unit (2).

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