RU2326370C2 - Method of thermal characteristics measurement (variants) and device for its implementation (variants) - Google Patents

Abstract

FIELD: measurement technique.

SUBSTANCE: measuring of the time from beginning of the inner surface heating of the object under study to the beginning of the temperature increasing in the given point on outer or lateral surface of the object under study is carried out. The time dependence of the outer or lateral surface of the object under study overheating is registered, then dependence of the heating first stage time on the overheating value of object under study outer or lateral surface is determined; the temperature conductivity of the object under study for different moments is calculated, then constant or mean value of the temperature conductivity is determined and the thermal conductivity of the object under study is calculated by the value of the temperature conductivity.

EFFECT: adequacy and accuracy increasing of thermal characteristics measurement.

8 cl, 12 dwg

Description

The invention relates to construction equipment and can be mainly used to measure the thermophysical characteristics of various building structures, for example walls, ceilings, floors, bulkheads, ceiling, etc.

A known method of drilling wells and a device for its implementation [1], allowing to obtain samples of materials from various depths. By measuring the parameters of these samples, one can obtain information on the physical and chemical properties and configuration of the deep layers. A disadvantage of the known method and device for its implementation is that they do not provide non-destructive testing of the studied object.

Numerous variants of ultrasonic flaw detection methods and devices that implement them, for example, are known [2, 3], which make it possible to determine the presence of inhomogeneities in various structures and the configuration of these inhomogeneities, however, devices of this kind do not allow measuring the thermophysical characteristics of the materials under study, in particular thermal resistance.

Numerous variants of methods are known for measuring the thermophysical characteristics of various electronic devices, for example, the method for determining the thermal resistance of semiconductor diodes described in [4]. A disadvantage of the known technical solution lies in a narrow scope: it can be used to measure the thermophysical characteristics of only electronic devices, and only one of their class is semiconductor diodes.

Numerous variants of devices are known for measuring the thermophysical characteristics of various electronic devices, for example, a device for measuring the thermal resistance of transistors [5]. A disadvantage of the known technical solution lies in a narrow scope: it can be used to measure the thermal resistance of only electronic devices, and only one of their class - transistors.

A device for determining the characteristics of materials described in [6] is known, comprising a source of pulsed heating, a thermocouple, and an electronic processing unit. A thermocouple is located on the surface of the test sample. The output of the thermocouple is connected to the input of the electronic processing unit. The main disadvantage of the known device is that when using pulsed heating requires complex processing of the measurement results, which requires sophisticated equipment. This leads to a significant increase in the cost of measurements. In addition, the great complexity of processing the measurement results leads to a decrease in their accuracy and reliability.

Closest to the technical nature of the claimed method is a method of non-contact non-destructive testing of the thermophysical properties of materials [7]. The known method consists in measuring the temperature at predetermined points on the surface of the sample and the ambient temperature with two thermal detectors, using the results obtained, determining the correction factor, then acting on the surface of the sample with a fixed point source of heat. At a given point in time, the excess temperatures of the heated surface at predetermined points are measured with two thermal detectors, heating is continued, and a point in time is measured when the temperature of the thermal receiver farther from the heating spot increases by a predetermined value. The measured values determine the coefficients of thermal diffusivity and thermal conductivity.

The closest in technical essence to the claimed device is a thermal probe for non-destructive testing of the thermophysical properties of materials [8], containing a linear heater and two thermocouples located symmetrically relative to the linear heater on both sides of it. The main disadvantage of the known device is that the linear heater forms a heat flux in the material diverging in a plane perpendicular to the axis of the linear heater.

Known technical solutions (method and device) have low consumer properties due to the narrow scope, low accuracy and low reliability of the measurements. The presence of these disadvantages is due to the following factors. Known technical solutions use a point or linear source of thermal energy, so it can be used only when measuring the thermophysical characteristics of homogeneous objects. If the object under study has various inhomogeneities (for example, a reinforced concrete wall), then the measurement results will differ when a point or linear source of thermal energy acts on various points on the surface of the object under study. In prototypes, the point or line of exposure to the source of thermal energy and the points at which the temperature is measured are on the same surface of the object under study, therefore, the known technical solutions are not applicable for measuring the thermophysical characteristics of multilayer objects. If the studied object has different thermophysical characteristics in the direction perpendicular to its surface and in the direction parallel to its surface, then known technical solutions can measure the thermophysical characteristics only in the direction parallel to the surface of the studied object. Thus, the known technical solutions are not applicable for measuring the thermophysical characteristics of anisotropic objects. Low accuracy and reliability of the known technical solutions due to the high complexity of the model that describes their work. So, in the known method, it is necessary to conduct preliminary measurements to determine the correction factor. The work of the known method and device are described by the heat balance equation, in which it is necessary to take into account the loss of thermal power to the environment due to convective and radiant heat transfer. In addition, in the heat balance equation of the known method, it is necessary to take into account the loss of thermal power due to the partial absorption of laser radiation by the environment and the partial reflection of laser radiation by the surface of the object under study. These components are taken into account approximately by calculation. When processing the measurement results in a known manner, an error function is used, calculated by expanding it into a Taylor series. The description of the known method indicates that the calculation of this function in an analytical form is very difficult. It is also indicated there that only for materials with a thermal diffusivity coefficient a≥10 ^-7 m ² / s it is possible to limit oneself to the first member of the Taylor series, and only then can the working formula be used to process the measurement results. All these factors together lead to low consumer properties of the known method and device due to the narrow scope and low accuracy and reliability.

The objective of the invention is to increase consumer properties by expanding the scope and increasing accuracy and reliability.

The solution of the problem in accordance with claim 1 is ensured by the fact that in the known method, which consists in heating the surface of the test object, measuring the temperature of the heated surface of the test object, measuring the surface temperature of the test object at a given point, the following improvements are made: the inner surface area is heated of the investigated object, measure the temperature of the heated portion of the inner surface of the studied object, measure the time interval m I wait for the beginning of heating of the portion of the inner surface of the test object and the start of temperature increase at a given point on the outer surface of the test object, while recording the dependence of the superheat of the outer surface of the test object on time, obtain the dependence of the duration of the first stage of heating on the superheat of the outer surface of the test object, calculate the values thermal diffusivity of the investigated object for different points in time, while setting a constant value of t thermal conductivity or calculate its average value, and the thermal conductivity value is calculated thermal conductivity of the investigated object.

The solution of the problem in accordance with paragraph 2 of the claims is ensured by the fact that in the known method, which consists in heating the surface of the test object, measuring the temperature of the heated surface of the test object, measuring the surface temperature of the test object at a given point, the following improvements are made: the inner surface is heated of the investigated object, measure the temperature of the heated portion of the inner surface of the studied object, measure the time interval m I wait for the beginning of heating of the portion of the inner surface of the test object and the start of temperature increase at a given point on the side surface of the test object, while recording the dependence of the amount of overheating of the side surface of the test object on time, obtain the dependence of the duration of the first stage of heating on the value of overheating of the side surface of the test object thermal diffusivity of the investigated object for different points in time, while setting a constant value of t thermal conductivity or calculate its average value, and the thermal conductivity value is calculated thermal conductivity of the investigated object.

When measuring the thermophysical characteristics of the studied object, the primary thermal conductivity determined by the measured parameters is usually the thermal diffusivity, and the thermal conductivity is calculated by the known thermal diffusivity using the relation [9]

where λ is the thermal conductivity of the material of the measured layer [W / mK]; a - thermal diffusivity of the material of the investigated layer [m ² / s]; with ₀ - volumetric heat capacity [J / m ³ K]; γ is the density of the material of the investigated object [kg / m ³ ].

It should be noted that abroad the thermal diffusivity is accepted as a reference value, and in Russia the thermal conductivity standard is traditionally used.

Note that the final value to be determined in building envelopes is the specific thermal resistance, determined by the formula

where r is the specific thermal resistance [m ² K / W], the reciprocal of the heat transfer coefficient α _s [W / m ² K]; l is the thickness of the investigated object [m].

For a multilayer object under investigation, the specific thermal resistance is determined from the relation

where r _{i is the} thermal resistance of the i-th layer of the investigated object, ar _k are contact thermal resistances between adjacent layers; n is the number of layers.

It is the presence of the second term that mainly prevents the calculation of thermal resistance from the known values of the thermal conductivity of each layer using the obvious equality

where l _i is the thickness of the i-th layer [m]; λ _i - thermal conductivity of the material of the i-th layer [W / mK].

Since the determination of contact thermal resistances between the layers is a serious problem, the use of relation (4) for estimating specific thermal resistances is unacceptable. In practice, the value of the effective specific thermal resistance r should be determined experimentally, in particular, from the experimentally determined effective thermal diffusivity.

It would seem that for a single-layer object under study it is not difficult to determine the specific thermal resistance calculated using formula (2). However, the purpose of the experimental methods for measuring r is precisely to investigate the actual thermal resistance, which depends on the observance of the manufacturing technology, not to mention the presence of reinforcement, inclusions, the possible porosity of the material, and other factors.

Given the foregoing, it becomes urgent to develop experimental methods for measuring specific thermal resistances that would combine the maximum speed of measurements with high accuracy and complete reliability.

We formulate the problem of developing a method and device operating in an unsteady mode and free from the disadvantages of pulse methods. The task includes the development of a physical and mathematical model, method and device, providing high information content, simplicity and accuracy of determining the effective thermal diffusivity of the studied object.

The idea is to fix the moment of completion of the first stage of the thermal regime of the object under study, when, as a result of the supply of heat power to the internal surface at a given point on the external or side surface, the first signs of overheating appear, that is, the temperature begins to differ from the initial one. Determination of the criterion for the end of the first stage, that is, an estimate of the amount of overheating sufficient for registration and subsequent processing, will be performed a posteriori.

Consideration of the case of a single-layer homogeneous object under study of constant thickness.

The purpose of the research is to solve the following problems:

1) development of a research method and an algorithm for processing measurement results;

2) determination of the time required for measurements, depending on the thermophysical properties of the material of the studied object;

3) development of a method and device and determination of requirements for them.

The physical model of the object under consideration - a single-layer object under investigation - can be represented as a uniform unlimited plate with a width L. At the initial moment of time, the inner surface of the plate is brought into contact with a heat source with a temperature t _cl .

We introduce the following restrictions:

1. The contact of the heat source with the heated surface area of the investigated object is carried out so quickly that this contact process can be considered instantaneous.

2. The temperature of the heat source from the beginning to the end of the process remains unchanged.

3. The thermal power of the source is constant throughout the process.

4. The length of the source of thermal power along the surface of the investigated object is much greater than the thickness of the studied object.

These limitations are best satisfied by a compact flow-through heat exchanger, whose thermal inertia is much less than the thermal inertia of the object under study.

We also introduce the following assumptions:

1. The heat flux through the object under study is one-dimensional and uniform in cross section.

2. The thermophysical parameters of the material of the studied object are constant.

3. The heat transfer coefficient from the source to the adjacent surface of the investigated object remains unchanged at any time.

4. Until the completion of the first stage of the unsteady thermal regime, the external (opposite to the one in contact with the heat source) surface of the object under investigation can be considered insulated.

Taking into account the accepted assumptions and limitations, the physical model of the object turns out to be similar to that adopted in the book [9] for a plate heated or cooled on both surfaces by media with the same temperature and heat transfer coefficients.

The mathematical model of the described object within the framework of the described physical model can be represented by a boundary-value problem, including the heat equation

with boundary conditions

and initial condition

where t is the temperature of the plate; θ is the time [s].

We introduce dimensionless variables

where Fo is the criterial Fourier number; y is the dimensionless coordinate of the plate; Bi - Biot criterion; θ is the dimensionless temperature of the plate.

We transform (5) - (8) to the form

We solve the problem by the method of separation of variables. We represent temperature as the product of two functions, the first of which depends only on the variable y, and the second only on the variable Fo.

After substituting (14) into (10) - (13), the problem splits into two.

where k is the parameter we introduced.

The solution of equation (15) will be equal to

We substitute (19) into (16) and (17), then

kA = 0 => A = 0, Y (y) = Bcosky for y = 0,

-kBsink = -BiBcosk for y = 1.

From here we get

This transcendental equation has innumerable roots and can be solved graphically or numerically.

Taking into account the solution of equation (18), we write the general solution as the sum of all particular solutions

The constants C _n can be determined from the initial condition (13) in the form [9]

Where

Then, taking into account (22) - (24), we rewrite (21)

Expression (25) with allowance for (9) allows us to calculate the temperature distribution in the plate at any moment of time for the given thermophysical properties of the plate and the medium.

The process of heating a flat layer is depicted in figure 1, where the abscissa represents the distance from the inner surface of the test object to a certain point inside the test object, and the temperature at this point along the ordinate. In Fig. 1, each moment in time t _i corresponds to its own coordinate X _i , more than which the material layer remains isothermal and preserves the initial temperature, while the temperature field is already higher than the initial one within the coordinate 0 X X <X _i . Within this layer 0≤X <X _i decreases from the temperature values T _i to T _0. Figure 1 shows five lines characterizing the temperature distribution in a layer of thickness L for time instants t ₁ t ₂ , t ₃ , t ₄ and t ₅ . Corresponding to these time instants, the values of the heating depth are, respectively, X ₁ , X ₂ , X ₃ , X _4, and L. Since L corresponds to the total thickness of the studied layer, the time t ₅ corresponds to the duration of the complete heating of the studied layer.

Thus, based on the considered model, it is possible to calculate the warm-up time with any given accuracy. We assume that the heating time has come if the temperature on the insulated surface is t = t ₀ + Δt ₃ , where 0.01 ° С≤Δt ₃ ≤2 ° С. This will correspond to the value of the Fourier number Fo ₁ . The choice of the range is preliminary and corresponds to an a priori idea of the sensitivity of the applied temperature measurement technique.

By measuring the duration of the initial stage of heating τ ₁ experimentally, one can determine the thermal diffusivity by the formula following from the first expression in (9):

To solve the problems formulated earlier, it is necessary to carry out computational studies of characteristic dependencies.

The most important parameters that determine the course of the process, characterized by the Bi ₁ criterion are the contact quality of the heated portion of the test object with the heat power source and the temperature of the heat power source.

Figure 2 shows the dependence of the criterion Fourier number Fo ₁ on criterion Bi ₁ , which characterizes the heat transfer rate of the working surface of the heat source with the inner surface of the object under study (this surface is accepted by the surface U ₁ , and the outer surface of the object under study will be denoted by the number U ₂ ). The value of Fo _{1 was} determined from the dependence of the surface overheating of U ₂ on the Fourier number, and then an inverse relationship was constructed. In this case, the surface overheating value U ₂ relative to the initial value by 0.1 K was selected as a criterion for completing the first heating stage. The calculations were performed at three operating temperatures t _{c1 of the} heat source: 40 ° С (line L ₁ ), 60 ° C (line L ₂ ), 80 ° С (line L ₃ ). As can be seen from figure 2, in a wide range of changes in the value of the Bio criterion - from 0.01 to 1000, the value of Fo ₁ changes only an order of magnitude. Although this change is very small in comparison with the variation of Bi ₁ values, this circumstance nevertheless creates a practical uncertainty in estimating the duration of the process.

Figure 3 presents fragments of the same dependence in a slightly more limited range, namely, when Bi ₁ > 10. As can be seen from figure 3, in the range of variation of the Biot criterion from 10 to 100, the value of Fo ₁ changes at any temperature of the heat source by no more than 10%, and when Bi ₁ > 100, the dependencies become saturated at constant levels. From the data of figure 3 it should be concluded about the need to ensure good thermal contact. In particular, in the case under consideration, in order to fulfill the condition Bi ₁ > 100, it is sufficient to ensure that the contact heat transfer coefficient is not less than 50 W / m ² K. Such contact heat transfer intensity is easily ensured in practice when using a heat-conducting paste of the type at the contact point of the surface of the heat exchanger with the test object sealant.

In Fig. 4, the dependences of the value of Fo ₁ , which characterizes the duration of the first stage of heating a flat object under investigation up to heating its opposite thermally insulated surface by 0.1 K, on the operating temperature of the heat power source with the criterion Bi ₁ equal to 10 (line L ₄ ), 100 (line L ₅ ) and 1000 (line L ₆ ). From the data of Fig. 4 it can be seen that at a heater temperature above 60 ° C, sufficient stability of the considered dependence is ensured with slight fluctuations (within 1 ... 2 ° C) of the temperature of the heat source.

Based on the data of FIG. 3 and FIG. 4, it can be concluded that the practical implementation of a thermal power source with a desired temperature level and thermal contact quality is practical.

The dependences considered above were obtained for one particular case of the criterion for completing the first stage of heating. For practice, it is important to evaluate the dependence of the value of Fo ₁ on the value of overheating of the opposite surface of the studied object selected as a criterion for completing the first stage. Such dependences are presented in FIGS. 5 and 6. FIG. 5 shows the dependence of the criterion number Fo ₁ , selected as a criterion for the duration of the first stage of heating a flat test object, on overheating of the external surface of the test object at criterion Bi ₁ = 10 and at source temperature equal: 40 ° C (line L ₇ ), 60 ° C (line L ₈ ) and 80 ° C (line L ₉ ). Figure 6 shows the dependence of the criterion number Fo ₁ on overheating of the external thermally insulated surface of the flat object under investigation at large values of the Biot criterion (Bi ₁ > 100) and at a temperature of the heat source equal to: 40 ° С (line L ₁₀ ), 60 ° С (line L ₁₁ ) and 80 ° C (line L ₁₂ ). The data of these graphs show that for the criterion Bi ₁ > 100, the value of Fo ₁ does not depend on the further growth of the Biot criterion, as the calculations showed, even if more significant overheating of the opposite surface of the test object is chosen as the criterion for completing the first stage of heating.

From Fig.6 it can be seen that at Δt ₂ = 1K and at a heater temperature of 40 ° C Fo ₁ = 0.11, which exactly corresponds to the data of [10], which presents the results of development and research of an approximate analytical method for calculating unsteady heat regime based on the ideas of two stages of heating. However, this coincidence is particular, and although for large Bio values there is really no further change in the value of Fo ₁ (as shown in [10]), however, there is a dependence on the source temperature and, as expected, on Δt ₂ . From this we can conclude that in the experiment it is useful to record not only the fact of overheating of the opposite surface of the studied object, but also to take the time dependence of the value of this overheat, with the subsequent construction of the inverse relationship. Such dependences, obtained on the basis of a calculation from the dependences of Fig. 6, are shown in Fig. 7, which shows the dependence of the duration of the first stage of heating τ ₁ in hours on overheating of the external thermally insulated surface of the flat object under investigation at Bi ₁ > 100 and at the temperature of the heat source equal to: 40 ° C (line L ₁₃ ), 60 ° C (line L ₁₄ ) and 80 ° C (line L ₁₅ ).

As can be seen from Fig.7, with overheating Δt ₂ = 0.1 ... 0.4 K, the measurement time at 40 ° C <t _c1 <80 ° C will be from 9 to 15 hours. Moreover, the accuracy of determining the thermal diffusivity of the material of the studied object can be significantly increased by removing the dependence of τ ₁ (Δt ₂ ). From Fig.7 it follows that in the range of changes in overheating from 0.1 to 1 K at a temperature of the heat source equal to 80 ° C, such measurements will take about 14 hours.

Thermal diffusivity is determined as follows: the experimental dependence of the form shown in Fig. 7 is removed. Then a theoretical relationship is used, similar to that shown in Fig.6. Then, using the formula (26), the thermal diffusivity values for different time instants are calculated. In this case, either the constancy of thermal diffusivity is established, or its average value is taken.

The conducted studies relate to the model of the studied object with a thermally insulated external surface. However, as the overheating of this surface increases, the intensity of natural radiant-convective heat transfer increases. In order to take this factor into account, we calculated the dependence of the Bi ₂ criterion on the external surface of the object under study on its overheating, the results of which are presented in Fig. 8. From the data of Fig. 8 it follows that even with small overheating of the outer surface of the test object, neglecting heat transfer is, strictly speaking, undesirable, although permissible. Therefore, in some cases it is advisable to solve the problem in a more general and rigorous setting. The evaluation results show that within the limits of overheating Δt ₂ = 1 ... 2K, the result can be refined to 5%.

The solution of the problem in accordance with paragraph 3 of the claims is ensured by the fact that the following improvements are made to the known device comprising a heater, a heat-sensitive element, and thermal insulation: the device further comprises a second heat-sensitive element, configured to fix the moment the temperature rises at a given point moreover, the heater comprises a heat exchanger with an inlet pipe extended in two mutually perpendicular directions To enter the heat carrier into the heat exchanger and the outlet pipe to exit the heat carrier from the heat exchanger, the outer surface of the heat exchanger is provided with thermal insulation except for the section adjacent to the inner surface of the test object, a contact temperature meter used between the inner surface of the test object and the outer surface of the heat exchanger is used as a heat-sensitive element. and a thermal imager was used as the second heat-sensitive element.

In the particular case, in accordance with paragraph 4 of the claims, the optical axis of the thermal imager is directed to the outer surface of the object under study.

In the particular case, in accordance with paragraph 5 of the claims, the optical axis of the thermal imager is directed to the side surface of the object under study.

The solution of the problem in accordance with paragraph 6 of the claims is ensured by the fact that the following improvements are made to the known device containing a heater, a heat-sensitive element, thermal insulation: the device further comprises a second heat-sensitive element, configured to fix the moment the temperature rises at a given point moreover, the heater comprises a heat exchanger with an inlet pipe extended in two mutually perpendicular directions To enter the heat carrier into the heat exchanger and the outlet pipe to exit the heat carrier from the heat exchanger, the outer surface of the heat exchanger is provided with thermal insulation except for the section adjacent to the inner surface of the test object, a contact temperature meter used between the inner surface of the test object and the outer surface of the heat exchanger is used as a heat-sensitive element. as the second thermosensitive element used the second contact meter peratura.

In the particular case in accordance with paragraph 7 of the claims, the second contact temperature meter is located on the outer surface of the test object.

In the particular case, in accordance with paragraph 8 of the claims, the second contact temperature meter is located on the side surface of the test object.

The variants of the structural embodiment of the device for measuring thermophysical characteristics described in paragraphs 3 and 6 of the claims of the model provide for the formation of a one-dimensional heat flux (the heat flux propagates rectilinearly from the inner surface of the test object to the outer surface of the test object), which is described by a much simpler mathematical model, than in the prototype, resulting in increased accuracy and reliability, which leads to increased consumer properties.

The variants of the structural embodiment of the device for measuring thermophysical characteristics described in claim 4 and claim 7 of the invention provide a fixation of the time at which the temperature rises at a given point located on the outer surface of the object under study.

The variants of the structural embodiment of the device for measuring thermophysical characteristics described in paragraphs 5 and 8 of the claims provide for fixing the time of the start of temperature rise at a given point located on the side surface of the investigated object.

The claimed method and device in comparison with the prototype method and the prototype device have higher consumer properties by expanding the scope and increasing the accuracy and reliability of measurements. In contrast to the prototype method and prototype device, the described technical solution uses a heat exchanger extended in two mutually perpendicular directions, therefore, measurements give effective (average) values of thermophysical characteristics, and in most cases, in practice, not point, but effective values of thermal characteristics, for example, when examining the walls of buildings. Due to the fact that the claimed technical solutions carry out heating of the inner surface, and the temperature is measured on the outer or side surface, the described method and device are applicable for the study of multilayer objects. Therefore, the described method and device can be used to measure the thermophysical characteristics of anisotropic objects. The claimed method and device provides the formation of a one-dimensional heat flux (the heat flux propagates linearly from the inner surface of the test object to the outer surface of the test object), which is described by a much simpler mathematical model than in the prototype. Thus, compared with the known technical solutions, the claimed method and device have a wider scope. In the described method and device uses a simpler and more reliable model. In the known method, it is necessary to carry out preliminary measurements to determine the correction factor, and in the described technical solutions this is not necessary. In the heat balance equation describing the operation of the claimed method and device, it is not necessary to take into account the loss of thermal energy to the environment due to convective and radiant heat transfer due to the use of a heat exchanger extended in two mutually perpendicular directions, equipped with thermal insulation. In the heat balance equation of the described method there are no terms necessary for the heat balance equation of the prototype method that describe the partial absorption of thermal power by the environment during the transfer of thermal energy from the energy source to the surface of the object under study and with partial reflection from the surface of the object under study. In the model describing the operation of the claimed method, there is no need to expand any functions in a Taylor series. Thus, the described technical solutions have higher accuracy and reliability. The expansion of the scope and increase the accuracy and reliability of measurements leads to an increase in consumer properties of the claimed technical solutions in comparison with prototypes.

The invention is illustrated by a description of specific embodiments of the claimed device and drawings, in which:

- figure 1-8 are graphs explaining the invention;

- figure 9 shows a diagram of a device corresponding to claim 3 and claim 4 of the claims;

- figure 10 shows a perspective view of a device corresponding to claim 3 and claim 4 of the claims;

- figure 11 shows a diagram of a device corresponding to claim 3 and claim 5 of the claims;

- Fig.12 shows a perspective view of a device corresponding to claim 3 and claim 5 of the claims.

In accordance with claim 3, the device for measuring thermal characteristics includes (Figs. 9-12) a heater, a thermosensitive element, thermal insulation 1, a second thermosensitive element configured to fix the moment the temperature rises at a given point, the heater contains an extended in two mutually perpendicular directions, the heat exchanger 2 is provided with an inlet pipe 3 for the heat carrier entering the heat exchanger and an output pipe 4 for the heat carrier exit and of the heat exchanger, the outer surface of the heat exchanger 2 is provided with thermal insulation 1, in addition to the section adjacent to the inner surface 5 of the test object 6, a contact temperature meter 7 is used as a heat-sensitive element, located between the inner surface 5 of the test object 6 and the outer surface of the heat exchanger 2, and as the second thermal imaging element used imager 8. In Fig.9-12, the following notation is also taken: 9 - optical axis of the imager, 10 - the outer surface of the the following object 6, 11 - the lateral surface of the investigated object 6, arrows 12 and 13 show the direction of movement of the coolant.

In the particular case (claim 4 of the claims), the optical axis 9 of the thermal imager 8 is directed to the outer surface 10 of the investigated object 6 (Fig.9 and Fig.10).

In the particular case (claim 5 of the claims), the optical axis 9 of the thermal imager 8 is directed to the side surface 11 of the investigated object 6 (Fig.11 and Fig.12).

Described in claims 3 to 5 of the claims, variants of a device for measuring thermophysical characteristics work as follows. The heated heat carrier passes through the inlet pipe 3 to the heat exchanger 2, transfers heat energy to the test object 6 through a portion of the inner surface 5 of the test object 6, adjacent to the outer surface of the heat exchanger 2. The contact temperature meter 7 records the moment the temperature rises in the contact area of the outer surface of the heat exchanger 2 s the inner surface 5 of the investigated object 6.

The thermal imager 8 captures the moment the temperature rises at a given point. In accordance with paragraph 4 of the claims, the target point is selected on the outer surface 10 of the test object 6. In accordance with paragraph 5 of the claims, the target point is selected on the side surface 11 of the test object 6. The calculation of the thermophysical characteristics of the test object is carried out according to the method described above.

Corresponding to claims 6-8 of the claims, embodiments of a device for measuring thermophysical characteristics have a design and operating principle similar to those described above, the difference is that instead of a thermal imager 8, a second contact temperature meter is used.

In accordance with paragraph 7 of the claims, the second contact temperature meter is located on the outer surface 10 of the test object 6.

In accordance with claim 8, a second contact temperature meter is located on the side surface 11 of the test object 6.

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Claims (8)

1. The method of measuring the thermophysical characteristics, which consists in heating the surface of the test object, measuring the temperature of the heated surface of the test object, measuring the surface temperature of the test object at a given point, characterized in that they heat the portion of the inner surface of the test object, measure the temperature of the heated portion of the inner surface of the test object, measure the time interval between the start of heating of the portion of the inner surface of the investigated object and the beginning of the temperature increase at a given point on the outer surface of the test object, while recording the dependence of the magnitude of the superheat of the outer surface of the test object on time, get the dependence of the duration of the first stage of heating on the magnitude of the superheat of the outer surface of the test object, calculate the thermal diffusivity of the test object for different times, at this establishes a constant value of thermal diffusivity or calculate its average value, and eraturoprovodnosti calculate the thermal conductivity of the test object. 2. A method of measuring the thermophysical characteristics, which consists in heating the surface of the test object, measuring the temperature of the heated surface of the test object, measuring the surface temperature of the test object at a given point, characterized in that they heat a portion of the inner surface of the test object, measure the temperature of the heated portion of the inner surface of the test object, measure the time interval between the start of heating of the portion of the inner surface of the investigated object and the beginning of the temperature increase at a given point on the side surface of the test object, the time dependence of the amount of overheating of the side surface of the test object is recorded, the dependence of the duration of the first stage of heating on the amount of overheating of the side surface of the test object is obtained, the thermal diffusivity of the test object is calculated for different times, at this establishes a constant value of thermal diffusivity or calculate its average value, and eraturoprovodnosti calculate the thermal conductivity of the test object. 3. A device for measuring thermophysical characteristics, comprising a heater, a thermosensitive element, thermal insulation, characterized in that the device further comprises a second thermosensitive element, configured to fix the moment the temperature rises at a given point, while the heater contains an extended length in two mutually perpendicular directions of the heat exchanger, equipped with an inlet pipe for entering the coolant into the heat exchanger and an outlet pipe for output and the heat carrier from the heat exchanger, the outer surface of the heat exchanger is provided with thermal insulation, in addition to the section adjacent to the inner surface of the test object, a contact temperature meter used between the inner surface of the test object and the outer surface of the heat exchanger is used as a heat-sensitive element, and a thermal imager is used as the second heat-sensitive element. 4. A device for measuring thermal characteristics according to claim 3, characterized in that the optical axis of the thermal imager is directed to the outer surface of the object under study. 5. A device for measuring thermophysical characteristics according to claim 3, characterized in that the optical axis of the thermal imager is directed to the side surface of the object under study. 6. A device for measuring thermophysical characteristics, comprising a heater, a thermosensitive element, thermal insulation, characterized in that the device further comprises a second thermosensitive element, configured to fix the moment the temperature rises at a given point, while the heater contains an extended length in two mutually perpendicular directions of the heat exchanger, equipped with an inlet pipe for entering the coolant into the heat exchanger and an outlet pipe for output and the heat carrier from the heat exchanger, the outer surface of the heat exchanger is provided with thermal insulation, in addition to the section adjacent to the inner surface of the test object, a contact temperature meter is used as a heat-sensitive element, located between the inner surface of the test object and the outer surface of the heat exchanger, the second contact meter is used as the second heat-sensitive element temperature. 7. A device for measuring thermophysical characteristics according to claim 6, characterized in that the second contact temperature meter is located on the outer surface of the test object. 8. A device for measuring thermophysical characteristics according to claim 6, characterized in that the second contact temperature meter is located on the side surface of the test object.

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