JP6243811B2 - Method and apparatus for measuring physical property values by steady method - Google Patents

Description

  The present invention relates to a method for measuring a physical property value by a steady method and a measuring apparatus therefor. Here, examples of the sample whose physical property value is to be measured include a porous material and a heat insulating material (ceramic material).

The steady method is a method in which a steady state in which there is no temperature change in a sample (hereinafter also referred to as a measurement sample) is realized, and the thermal conductivity k (physical property value) of the sample is obtained by equation (1) (Fourier equation). Yes (see, for example, Patent Document 1).
Here, when the heat flow rate q can be measured, the thermal conductivity k of the sample can be obtained according to the equation (1) by the stationary absolute method shown in FIG.
However, since it is difficult to measure the heat flow velocity q moving in the sample, the steady comparison method shown in FIG. 12B, that is, a measurement method using a standard sample with a known thermal conductivity is often used. . In this method, a flat measurement sample and a standard sample are brought into close contact so that the heat flow rate q for moving the measurement sample and the standard sample is the same, and the heat of the sample is determined according to equations (2) and (3). This is a method for obtaining the conductivity k.

Note that the variable used is the thermal conductivity of the sample (thermal conductivity by the diffusion heat transfer) k = ρCα, the thermal conductivity k _s of a standard _sample, the measurement sample thickness L _1, the standard sample thickness L ₂ -L ₁ , sample temperature T (0) before irradiation (also referred to as T ₀ ), back surface temperature T (L ₁ ) of the measurement sample in FIG. 12A, back surface temperature of the measurement sample in FIG. T (L ₁ ), back surface temperature T (L ₂ ) of the standard sample in FIG. 12 (B), and heat input amount (heat flux) q per unit area unit time.

  The steady method is widely used as a method for measuring thermal conductivity. In particular, it is often applied to a heterogeneous material such as a porous material or a heat insulating material having a low thermal conductivity. This is because the laser flash method, which is widely used for measuring the thermal conductivity, requires that the sample be a homogeneous material and that the sample thickness be as thin as 1 to 3 mm. This is because it is not suitable for measuring heterogeneous materials.

JP 2005-195550 A

However, the conventional steady-state method still has the following problems to be solved.
Porous materials and heat insulating materials for which many measurements are performed by the steady-state method have voids in the sample, and not only the diffusion heat transfer phenomenon handled by the Fourier equation but also the heat flux due to the radiant heat transfer phenomenon coexists. In addition, a ceramic material often used as a heat insulating material has a property of transmitting infrared rays, and therefore conducts heat due to a diffusion heat transfer phenomenon and a radiation heat transfer phenomenon.
Conventionally, it has been difficult to handle this radiant heat transfer phenomenon. Therefore, the heat conduction due to the diffusion heat transfer phenomenon and the radiant heat transfer phenomenon are all assumed to be heat conduction based on the diffusion heat transfer phenomenon, and according to the above Fourier formula. At present, the apparent thermal conductivity of the sample has been obtained.
Therefore, under conditions where the radiant heat transfer phenomenon cannot be ignored, it is difficult to say that the accurate heat conduction phenomenon is grasped, and the handling of the measured heat conductivity is a problem.

  The present invention has been made in view of such circumstances, and provides a method for measuring a physical property value by a steady method in a measurement sample in which a radiant heat transfer phenomenon and a diffusion heat transfer phenomenon, which have been difficult to handle in the past, and a measurement apparatus thereof are provided. The purpose is to provide.

In the method for measuring physical property values by the steady method according to the first invention in accordance with the above object, after setting the plate-like measurement sample to the temperature T ₀ , the surface side of the measurement sample is heated with a heat flux having a constant intensity, In the measurement method of the physical property value by the steady method for obtaining the physical property value of the measurement sample,
The apparent thermal conductivity k ′ is obtained using the temperature measured on the front and back surfaces of the measurement sample and the thickness dl of the measurement sample, and depends on the thickness dl of the measurement sample and the thermal diffusivity α of the measurement sample. A physical property value calculating step for obtaining the thermal diffusivity α of the measurement sample as a physical property value by using an equation indicating the apparent thermal conductivity k ′.

  In the physical property value measurement method according to the stationary method according to the first invention, an optical thickness μdl, which is a product of an absorption coefficient μ and a thickness dl, of the measurement sample is obtained before the physical property value calculation step, It is preferable to perform a determination step of determining whether heat conduction from the front surface to the back surface of the measurement sample is caused by diffusion heat transfer or radiation heat transfer based on the thickness μdl.

  In the method for measuring physical property values by the steady method according to the first invention, a material whose thermal conductivity is known and whose heat transfer is caused by diffusion heat transfer is closely arranged or impervious to the front and back surfaces of the measurement sample. An optical film can be formed, and heating on the surface side of the measurement sample can be performed by continuous irradiation with heating light.

  In the method for measuring physical property values by the steady method according to the first aspect of the invention, the heating element a is closely disposed on the surface of the measurement sample, and the thermal conductivity is known on the back surface of the measurement sample. It is possible to control the heating of the heating element a by closely arranging a material generated by heat or forming an opaque film.

In the method of measuring physical property values by the steady method according to the first invention, the heating element a is closely arranged on the surface of the measurement sample, and the heating element b is arranged with a gap from the heating element a. The heating element a and the heating element b can be controlled to be heated to the same temperature.
Here, the heating element a is arranged on the surface of the measurement sample via a material whose thermal conductivity is known, heat transfer is caused by diffusion heat transfer, or an opaque film, On the back surface, a material having a known thermal conductivity and heat transfer caused by diffusion heat transfer can be closely arranged or an opaque film can be formed.

  Note that the heating element b preferably covers the heating element a.

  The apparatus for measuring physical property values by the steady method according to the second invention in accordance with the above object is a measuring apparatus used for the method for measuring physical property values by the steady method according to the first invention, and the measurement sample can be disposed inside. And a transparent glass provided at the end of the heating furnace for continuously irradiating heating light on the surface side of the measurement sample.

  Since the physical property value measurement method and the measurement apparatus according to the present invention have a physical property value calculation step, the thickness of the measurement sample can be taken into account when calculating the physical property value. As a result, even if the measurement sample is a coexisting state of the radiant heat transfer phenomenon and the diffusion heat transfer phenomenon, which have been difficult to handle in the past, the physical property value of the measurement sample can be obtained with high accuracy by a steady method.

  In particular, since the determination that the heat conduction of the measurement sample is caused by radiant heat transfer is performed by the determination process using the optical thickness μdl, which is the product of the absorption coefficient μ and the thickness dl of the measurement sample, the heat conduction is A physical property value can be obtained for a measurement sample that does not know whether it is caused by diffusion heat transfer or radiation heat transfer.

It is explanatory drawing of the heat transfer model of the measurement sample used as the precondition of the measuring method of the physical-property value by the stationary method which concerns on one embodiment of this invention. It is a graph which shows the boundary of diffusion heat transfer heat conduction and radiation heat transfer heat conduction. It is an analysis flowchart which shows the procedure at the time of measuring the physical-property value of a measurement sample using the measuring method of the physical-property value by the stationary method which concerns on one embodiment of this invention. Is a graph showing the dependency of the absorption coefficient of the thickness of the measurement sample when the thermal conductivity k ₂ the apparent relative thermal conductivity k ₂ by only diffusion heat transfer _'5% greater. The thermal conductivity of the apparent k _{2 'and} is a graph showing an example of the relationship between the thermal diffusivity alpha ₂ of the second layer. It is a graph which shows the thickness dependence of the apparent thermal conductivity of the material which has the same physical-property value. It is an analysis flowchart which shows the procedure at the time of measuring the physical-property value of a measurement sample using the measuring method of the physical-property value by the stationary method which concerns on a modification. (A) is an explanatory view of a steady heat flux heating method of a three-layer material when a material having a known thermal conductivity is used as the material of the first layer or the third layer, and (B) is a heat conduction as a material of the third layer. It is explanatory drawing of the steady heat flux heating method of a two-layer material in the case of using a material with a known rate. (A), (B) is an explanatory view of a steady heat flux heating method for a three-layer material when a material whose thermal conductivity is not known is used as the material for the first layer and the third layer, respectively, and another steady heat flux heating method It is explanatory drawing of. It is explanatory drawing of the steady heat flux heating method of a single layer material. (A) is explanatory drawing of the measuring device of the physical-property value which applies a light irradiation method, (B) is explanatory drawing of the measuring device of the physical-property value which applies a resistor heating method. (A) is explanatory drawing of the measuring method of thermal conductivity by a stationary absolute method, (B) is explanatory drawing of the measuring method of thermal conductivity by a steady comparison method.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, the preconditions before performing the physical property value measurement method by the steady method according to the embodiment of the present invention will be described with reference to FIG.
The measurement sample 10 to be measured is, for example, a heterogeneous material such as a porous material or a heat insulating material (ceramic material) having a low thermal conductivity, and not only a diffusion heat transfer phenomenon but also a radiant heat transfer phenomenon. It is a plate-like sample that coexists.

Next, the plate materials 11 and 12 made of a material only having diffusion heat transfer are adhered to the front and back surfaces of the measurement sample 10 described above (the measurement sample 10 is sandwiched between the plate material 11 and the plate material 12). ) A three-layer material 13 is formed. For the plate members 11 and 12, for example, graphite or metal can be used.
Further, the opaque material can be formed by making the front and back surfaces of the measurement sample 10 opaque, without using the plate material as described above. In this case, the measurement sample 10 can be a measurement object as a single layer material.

In measuring the thermal conductivity, the entire three-layer material 13 described above is set to a temperature (steady temperature) T ₀ , and then the surface of the plate material 11 (hereinafter also simply referred to as the first layer) as the first layer is stationary. It is assumed that the temperature is measured by heating with a heat flux (a heat flux with a constant intensity) (that is, a steady method).
Here, as a method of setting the entire three-layer material 13 to the temperature T ₀ , for example, there is a method of setting the three-layer material 13 in a heating furnace controlled to the temperature T ₀ .
In addition, as a method of giving a steady heat flux to the surface of the first layer, for example, 1) a method of continuously irradiating the surface of the first layer using heating light, and 2) a constant current using the first layer as a conductive material There is a method of flowing.

For temperature measurement, for example, the temperature of each layer boundary is measured using temperature measuring means such as a thermocouple.
Here, the temperature variation from the steady temperature T ₀ and T. The surface coordinates of the first layer and x = 0, the third layer of the back surface coordinates (plate 12) and x = L _3, the interface coordinates between the first and second layers (measurement sample 10) x = Let L ₁ and the interface coordinates between the second layer and the third layer be x = L ₂ .

It is assumed that energy emission of λ ₃ T ₃ (L ₃ ) is directed outward from the back surface of the third layer. Further, at the interface x = L ₁ , there is λ ₁ T ₁ (L ₁ ) energy radiation from the first layer to the second layer, and at the interface x = L ₂ , λ ₃ from the third layer to the second layer. T ₃ (L ₂ ) energy is emitted.
Here, in order to distinguish the radiation energy from the back surface of the third layer to the outside and the radiation energy from the interface between the second layer and the third layer to the second layer, the back surface of the third layer (x = L ₃ ). U ₁ is added to the radiant energy from the outside to the outside. In addition, when there is energy radiation from the back surface of the three-layer material 13 and the radiation to the second layer (measurement sample 10) side of the third layer (plate material 12) is equal to the radiation to the back surface side, u ₁ is 1. And

The variables used are density ρ _i , specific heat C _i , thermal diffusivity α _i , thermal conductivity (thermal conductivity by diffusion heat transfer) k _i = ρ _i C _i α _i , thermal conductivity k _{s of} standard sample, Thickness dl _i , first layer emissivity ε ₁ , third layer emissivity ε ₃ , second layer refractive index n, second layer absorption coefficient μ, sample temperature before irradiation (temperature before heating) T ₀ , the amount of heat input per unit area unit time (heat flux) q (i = 1,2,3, showing the first to third layers). Here, the emissivity, the refractive index, and the absorption coefficient are generally wavelength-dependent, but those that have been appropriately averaged are used.
Therefore, the following relationship holds.
dl ₁ = L ₁
dl ₁ + dl ₂ = L ₂
dl ₁ + dl ₂ + dl ₃ = L ₃

Further, constants λ ₁ and λ ₃ relating to radiation from the second layer side rear surface of the first layer and the second layer side surface of the third layer are expressed as follows.
λ ₁ = 4ε ₁ σT ₀ ³ (4)
λ ₃ = 4ε ₃ σT ₀ ³ (5)
The constant λ ₂ related to the radiation from the inside of the second layer is expressed as follows.
λ ₂ = e ₁ n ² σT ₀ ³ (6)
In the calculation of λ ₁ , λ ₃ , and λ ₂ described above, the pre-heating temperature T ₀ is used, but the temperature to be measured may be used.
Here, e ₁ in the equation (6) is a constant, and an example of this value is e ₁ = 8π. This value is considered to be somewhat different depending on the radiation and absorption model in the sample. For example, e ₁ = 32/3 may be used. To do. Further, σ is a Stefan Boltzmann constant.

Next, the thermal conductivity formula of the measurement sample 10 serving as the second layer will be described.
The apparent thermal conductivity k ₂ ′ (also expressed as k ′) of the measurement sample 10 by the steady method is defined by the equation (7). In the state where the diffusion heat transfer phenomenon and the radiation heat transfer phenomenon coexist, the apparent thermal conductivity k ₂ ′ of the measurement sample 10 is given by the equation (8).

Here, β ₁₀ , μ _c dl ₂ , p _c , β ₁ (p), and β ₃ (p) are shown in the following formulas (9) to (13), respectively. Note that λ ₁ , λ ₃ , and λ ₂ are expressed by the above-described equations (4) to (6).

Μ _c used in the above equation (8) is an absorption coefficient that becomes a boundary between radiant heat transfer heat conduction and diffusion heat transfer heat conduction.
Therefore, when the absorption coefficient μ is smaller than this value μ _c , the radiant heat transfer is mainly conducted, whereas when the absorption coefficient μ is larger than this value μ _c , the diffusion heat transfer is mainly conducted. . The absorption coefficient μ _c that defines the boundary between the two heat conductions is given by the optical thickness formula (10) shown in FIG. In FIG. 2, the left side from the line of the equation (10) is radiant heat transfer heat conduction, and the right side is diffusion heat transfer heat conduction. The optical thickness of the measurement sample 10 is represented by the product of the absorption coefficient μ and the thickness L (= dl ₂ ) of the measurement sample 10.
In this equation (10), e ₂ is a constant. Further, by using the absorption coefficient mu _c of this boundary, the Laplace variable _{p c} used in equation (8), shown in (11).

Unit volume of internal measurement sample 10 is a second layer, and the energy q _v emitted per unit time, according to (14) below. Here, λ ₂ in the equation (14) is given by the above equation (6).

Constant e ₂ of the optical represents the thickness (10) wherein providing the boundary described above, when the one-dimensional radiation is satisfied is given by (15).
When the radiation into the second layer at the interface between the first layer and the second layer has a Lambertian surface characteristic that is three-dimensionally radiated, the constant e ₂ is a constant different from the equation (15). However, it should be set according to the characteristics of each surface. This Lambertian surface is a surface where the radiation intensity from the surface becomes I ₀ cos (θ), where θ is the angle from the interface vertical direction. I ₀ is the vertical radiation intensity.
The same applies to the interface between the second layer and the third layer.

In addition, the apparent thermal conductivity k ₂ ′ of a single-layer material measured by a steady method (for example, as described above, when an opaque film is formed by performing an opaque process on the front and back surfaces of a measurement sample) Is expressed by equation (16).

Here, dl ₂ is the thickness of the single layer material.
Further, the above-mentioned (8) and the above formula (16) k in formula _{2 (no} dashes "'") is the thermal conductivity due to diffusion heat transfer of the measurement sample 10, k _{2 =} ρ 2 C defined by _{2 α 2.}
The above-described equation (16) is an equation in which the thicknesses of the first layer and the third layer are derived as “0” in the above-described equation (8), and the suffix (subscript) is a three-layer material. is used as an object (e.g., thermal conductivity is used as it the k _2).

Next, a method for measuring physical property values by a steady method according to an embodiment of the present invention will be described with reference to FIG. The following processing is sequentially performed based on a computer program using data input to a computer (arithmetic processing means).
The analysis target is a thermophysical value of the measurement sample 10 to be the second layer shown below.
The other physical property values and the thickness of each layer are known. Specifically, as shown in FIG. 3, the known data of one plate 11 (first layer) is density ρ ₁ , specific heat C ₁ , thermal diffusivity α ₁ , thickness dl ₁ , and measurement sample The known data of 10 (second layer) is density ρ ₂ , specific heat C ₂ , absorption coefficient μ, refractive index n, thickness dl ₂ (also referred to as dl), and the other plate material 12 (third layer). Known data are density ρ ₃ , specific heat C ₃ , thermal diffusivity α ₃ , and thickness dl ₃ .

However, when radiative heat transfer is negligible, the thermal conductivity of the measurement sample can be obtained, so that all physical property values of each layer need not be known.
The measured thermophysical value depends on the material properties, and there are the following two cases.
1) When radiative heat transfer can be ignored: thermal conductivity k ₂ of the second layer
2) When radiant heat transfer cannot be ignored: thermal diffusivity α ₂ (also expressed as α) of the second layer, and thermal conductivity k obtained by multiplying this thermal diffusivity α ₂ by density ρ ₂ and specific heat C _{2. 2} (= ρ ₂ C ₂ α ₂ ) and apparent thermal conductivity k ₂ ′ (dl ₂ ) at the measured thickness

First, the determination process of step 1 (ST1) will be described.
The optical thickness μdl ₂ (product of the absorption coefficient μ and the thickness dl ₂ ) is calculated using the absorption coefficient μ and the thickness dl _{2 of the} measurement sample 10, and radiant heat transfer heat and diffusion heat transfer heat and it compares the optical thickness e ₂ which gives the boundaries of conduction.
Specifically, when the optical thickness μdl ₂ of the measurement sample 10 is sufficiently larger than the optical thickness e ₂ given to this boundary (μdl ₂ >> e ₂ ), that is, the heat conduction of the measurement sample is diffusion heat transfer. If it is determined that the error has occurred, the process proceeds to step 2 (ST2). On the other hand, if not, that is, if it is determined that the heat conduction of the measurement sample is due to radiant heat transfer, the process proceeds to step 3 (ST3).

Here, an example of a method for determining whether or not the optical thickness μdl ₂ of the measurement sample is sufficiently larger than the optical thickness e ₂ that provides a boundary between radiative heat transfer and diffusion heat transfer heat conduction. Show.
When both heat conduction phenomena exist, compared to the thermal conductivity k obtained by assuming that the heat conduction is caused only by diffusion heat transfer, that is, k ₂ = ρ ₂ C ₂ α ₂ The thermal conductivity k ₂ ′ increases. Here, _{k 2} '5% increase as compared to the _{k 2 (k 2' / k} 2 = 105%) the dependency of the absorption coefficient of the sample thickness, shown in FIG.

When deciding in accordance with FIG. 4, is from k _{2 'absorption} coefficient of the measurement sample as compared to the k ₂ Ensure 5% larger thickness, when the thickness dl ₂ of the measurement sample is thicker than this thickness, It proceeds to step 2, to measure the thermal conductivity k ₂ by the diffusion heat transfer thermal conduction. On the other hand, if it is thin, the process proceeds to step 3 to measure the apparent thermal conductivity k ₂ ′.
In addition, FIG. 4 was created using the above-described formula (8) based on the physical property values shown in Table 1 below, and as an actual correspondence, based on the physical property values of the measurement target (8) K ₂ ′ / k ₂ is evaluated and judged using an equation.

Note that the above-described determination may be performed by creating a diagram similar to FIG.
In FIG. 4, the apparent thermal conductivity k ₂ ′ is 5% larger than the thermal conductivity k ₂ by only diffusion heat transfer, but this is an example, and it is necessary for practical use. It is desirable to determine whether the heat conduction is caused by diffusion heat transfer or radiant heat transfer by the same examination according to the accuracy to be performed. At this time, since the physical property value of the measurement sample is unknown, a physical property value referring to a literature value or the like of a similar material may be used.

Then, the heat conductivity calculation process resulting from the diffusion heat transfer of step 2 is demonstrated.
Here, to calculate the thermal conductivity k ₂ of the measurement sample from (17). Note that this step 2, the thermal conductivity of the measurement sample, to be done when it is determined that only the diffusion heat conduction thermal conductivity, the thermal conductivity k ₂ is a thermal conductivity by the diffusion heat transfer.
Here, q is the amount of heat input (heat flux) per unit time and unit area.
Therefore, when a material having a known thermal conductivity is used for the first layer or the third layer, the temperature difference and the thickness at both ends of the first layer or the third layer are used to obtain the equation (18). On the other hand, when a material whose thermal conductivity is unknown is used, the heat flux is obtained by the method shown in the drawings described later.

In addition, the apparent heat conductivity calculation step due to radiant heat transfer in step 3 will be described.
Here, as in step 2 described above, the apparent thermal conductivity k ₂ ′ of the measurement sample is measured using the equations (19) and (18) (that is, the temperature and measurement measured on the front and back surfaces of the measurement sample). Calculate (using sample thickness). In addition, this step 3 is performed when it is determined in the above-described determination in step 1 that the radiative heat transfer cannot be ignored in the heat transfer of the measurement sample.

After the above step 3 is completed, the calculation process of λ ₁ and λ _{3 in} step 4 (ST4) and the physical property value (thermal diffusivity) calculation process in step 5 (ST5) are sequentially performed.
First, step 4 will be described.
When using the above-described three-layer material 13 (or two-layer material) when measuring the measurement sample 10, it is necessary to perform thermal diffusivity analysis in step 5 described later using the above-described equation (8). However, in this case, since it is necessary to calculate the lambda _1, lambda ₃ of sheet material described in (8), using (20) and (21), lambda _1, lambda ₃ calculations To do.
In the measurement of the measurement sample, when using the above-described single layer material, λ ₁ and λ ₃ are calculated using the equation (22).
Note that λ ₁ is obtained as λ ₁ = λ ₃ when the first layer and the third layer are made of the same material.

Next, step 5 (ST5) will be described.
In step 5, the apparent thermal conductivity k ₂ ′ measured in step 3 described above is substituted into the equation (8) that gives the apparent thermal conductivity k ₂ ′ of the measurement sample, and the thermal diffusivity of the measurement sample is substituted. α ₂ is calculated. Incidentally, an expression showing the expression (8), the thermal conductivity k ₂ the apparent depends on the thickness dl ₂ and the thermal diffusivity alpha ₂ of the measurement sample 10 _'.
Here, when obtaining the thermal diffusivity α ₂ of the measurement sample, an example using the physical property values of the three-layer material shown in Table 1 will be described.

When the thickness of the measurement sample is 50 mm, the absorption coefficient that gives the boundary between radiative heat transfer and diffusion heat transfer is μ _c = 35.9 (1 / m).
Here, taking as an example the case where the absorption coefficient of the measurement sample is μ = 25.1 (1 / m), the absorption coefficient of the measurement sample is the boundary between radiant heat transfer and diffusion heat transfer heat conduction. The measurement sample is judged to be in the region of radiative heat transfer.
Then, assuming that the measured apparent thermal conductivity is k ₂ ′ = 21.8 (W / (mK)), this value is substituted into the aforementioned equation (8). Since this equation is a function of only the thermal diffusivity α _{2 of} the measurement sample, the thermal diffusivity of the measurement sample can be obtained, and α ₂ = 9.99 × 10 ⁻⁶ (m ² / s) is obtained. obtain. FIG. 5 shows the relationship between the apparent thermal conductivity k ₂ ′ and the thermal diffusivity α ₂ of the second layer.

Finally, in step 6 (ST6), the obtained measurement result is output as follows.
The measurement results are as follows.
1) When the absorption coefficient is sufficiently large and radiative heat transfer can be ignored, the thermal conductivity k2 of the measurement sample 10 obtained in step ₂ is the measurement result, and this is output as a physical property value. .
2) If the radiation heat transfer thermal conductivity can not be ignored, since the thermal diffusivity alpha ₂ of the measurement sample 10 obtained in Step 5 is the measurement result, and outputs it as physical property values. Further, the thermal conductivity k ₂ (= ρ ₂ C ₂ α ₂ ) by diffusion heat transfer is added as a measurement result (physical property value) by multiplying the thermal diffusivity α ₂ by the density ρ ₂ and the specific heat C _2. Also good. Furthermore, when adding the apparent thermal conductivity to the measurement result, k ₂ ′ obtained by measuring in step 3 is set as k ₂ ′ (dl ₂ ) as the apparent thermal conductivity in the thickness of the measurement sample. This is output as a physical property value.

The apparent thermal conductivity of a material for which radiative heat transfer cannot be ignored is thickness dependent, so the apparent thermal conductivity value measured at a specific thickness can be used as is in actual operation. The field used is a source of error.
This is particularly noticeable in the region of radiative heat transfer. As an example, the thickness dependence of the apparent thermal conductivity of materials having the same physical property values is shown in FIG.

As a measurement procedure of the physical property value of the measurement sample shown above, FIG. 3 illustrates the case where the apparent heat conductivity calculation step due to radiant heat transfer in step 3 is performed after the determination step in step 1 is performed. After performing the apparent heat conductivity calculation process due to radiant heat transfer in step 3, the determination process in step 1 may be performed.
Further, in the analysis flow shown in FIG. 3, the emissivities ε ₁ and ε ₃ of the first layer and the third layer are unknown, but the emissivities ε ₁ and ε ₃ are known, and thus λ ₁ and λ ₃ are known. If is known, step 4 can be omitted.

Furthermore, the physical property value can be measured by assuming that the measurement sample is a material having both diffusion heat transfer heat conduction and radiation heat transfer heat conduction. Hereinafter, the measurement procedure of the physical property value of the measurement sample will be described with reference to FIG. 7, but since it is basically the same as FIG. 3 described above, detailed description thereof will be omitted.
In FIG. 7, since the measurement sample is handled as a material having both diffusion heat transfer and radiant heat transfer, the heat transfer of the measurement sample is caused by either diffusion heat transfer or radiant heat transfer. Step 1 of FIG. 3 for determining whether to do can be omitted. This is because the calculation of step 2 in FIG. 3 is included when calculating the apparent thermal conductivity k ₂ ′ of the measurement sample in step 11 (ST11) similar to step 3 in FIG.
Therefore, first, in step 11, the apparent thermal conductivity k ₂ ′ of the measurement sample is calculated.

After step 11 is completed, λ ₁ and λ ₃ are calculated in step 12 (ST12) (similar to step 4 in FIG. 3), and the thermal diffusivity α ₂ of the measurement sample is further measured in step 13 (ST13). (Similar to step 5 in FIG. 3).
Finally, in step 14 (ST14), the following obtained measurement results are output.
Since the thermal diffusivity α ₂ of the measurement sample 10 obtained in step 13 is a measurement result, this is output as a physical property value. Further, the thermal diffusivity α ₂ is multiplied by the density ρ ₂ and the specific heat C _2, and the thermal conductivity k ₂ (= ρ ₂ C ₂ α ₂ ) by diffusion heat transfer is output as a physical property value. Further, as the apparent thermal conductivity in the thickness of the measurement sample, k ₂ ′ obtained by measurement in step 11 is set as k ₂ ′ (dl ₂ ), and this is output as a physical property value.
In the case where the measurement sample is a material in which radiant heat transfer heat conduction can be ignored and is only regarded as diffusion heat transfer heat transfer, the heat conductivity k ₂ (= ρ ₂₎ obtained by multiplying the thermal diffusivity by the density and specific heat. C ₂ α ₂ ) and the apparent thermal conductivity k ₂ ′ (dl ₂ ) are substantially equal.

A specific example of a steady heat flux heating method applicable to the above-described physical property value measuring method according to the steady method of the present invention will be shown below.
<When a material with known thermal conductivity is used as the material of the first layer or the third layer>
As an example of this heating method, the case of a three-layer material is shown in FIG. 8A, and the case of a two-layer material is shown in FIG. 8B.
Here, FIG. 8A shows that the sample end surface of the three-layer material 13 (the surface of the plate material 11 as the first layer) is continuously irradiated with heating light, and in a steady state, a steady heat flow from the irradiation side to the back surface side. A bundle is realized. In this case, the heat flux q is obtained by the above-described equation (18).
Further, in FIG. 8B, the first layer is an electric resistor (heating element) 14, and heating is controlled by supplying a current using a heating power supply 15. At this time, in a steady state, the heat flux q is obtained by the above-described equation (18) using the temperature difference and the thickness at both ends of the third layer whose thermal conductivity is known.

<When the thermal conductivity of the material of the first layer and the third layer is not known>
As an example of this heating method, the case of a three-layer material is shown in FIGS. 9A and 9B, and the case of a single-layer material is shown in FIG.
The case of a three-layer material will be described below with reference to FIG.
1) The heating element a and the heating element b are installed with a slight gap therebetween, and both are controlled to be heated to the same temperature “T ₀ + T”. The heating control of the heating element a is performed by the heating power source a, and the heating control of the heating element b is performed by the heating power source b.
Here, the temperature rise T is, for example, 10 ° C.

2) In this case, the amount of electrical heat input Q (= I ² R) of one heating element a by the heating power source a almost flows to the measurement sample 10 side. In addition, the radiant heat flux from the heating element a to the heating element b side is suppressed because both the heating elements a and b are controlled at the same temperature.
3) Therefore, the amount of electrical heat input Q to the heating element a becomes the amount of heat input to the measurement sample 10, and the heat flux q is obtained by dividing by the sample area.
4) If a material having a known thermal conductivity is used as the material of the plate materials 11 and 12 of the first layer and the third layer, the heat flux q is calculated using the temperature difference, thickness, and thermal conductivity at both ends of this layer. The heat flux can be obtained with higher accuracy.

Note that, instead of the above-described FIG. 9A, the structure of the heating element b can be modified as shown in FIG. 9B.
As shown in FIG. 9B, the structure of the heating element b is configured so as to cover the heating element a without contacting the heating element a, so that the Joule heat of the heating element a can be made more efficient. Can be transmitted to the measurement sample 10.

Next, the case of a single layer material will be described below with reference to FIG.
If the same heating method as that in FIG. 9A is used, measurement is possible even when the measurement sample 10 is a single body. Here, the heating sample a is heated on the surface of the measurement sample 10 to heat the measurement sample 10.
A heat flux q is obtained from the electric heat input amount Q of the heating element a that inputs heat into the measurement sample 10.
Here, the apparent thermal conductivity k ₂ ′ of the single layer material is obtained by the equation (23).

By using this value and the above-described equation (16) that is an equation of the apparent thermal conductivity of the single-layer material, the above-described measurement results can be obtained as in the case of the three-layer material.
That is, for the measurement sample 10 of a single layer material, when the radiant heat transfer heat conduction is sufficiently smaller than the diffusion heat transfer heat transfer, the heat conductivity k ₂ of the measurement sample is set to When the heat conduction cannot be ignored, the thermal diffusivity α ₂ can be obtained respectively.
In addition, it is the same as the measurement with a three-layer material that the apparent thermal conductivity in the case where radiant heat transfer cannot be ignored has thickness dependency.

At this time, constant ratios λ ₁ and λ ₃ using the emissivities ε ₁ and ε ₃ from the end face of the measurement sample 10 are used in the same expression. Therefore, in order to realize the same condition, the end face of the measurement sample 10 is used. Must be covered with a light-impermeable film.
Further, by using the condition of the above-described formula (22) that the heat flux entering the measurement sample 10 in a steady state is equal to the heat flux radiated from the back surface of the measurement sample, λ _{3 is set} to the back surface temperature T ( L).
Note that, by making the opaque films at both ends of the measurement sample 10 the same, λ ₁ has the same value as λ ₃ .

Here, a method of calculating λ ₁ and λ ₃ will be described below.
First, the case of a three-layer material and a two-layer material will be described.
When the apparent thermal conductivity k ₂ ′ is substituted into the above equation (8) to obtain the thermal diffusivity of the measurement sample, the constants λ ₁ and λ ₃ related to the radiation of the surfaces of the first layer and the third layer are obtained. Need to be calculated.
In the case of the measurements shown in FIGS. 8A, 8B, and 9A, the heat flow rate q flowing through the third layer is equal to the energy flux radiated from the back surface of the measurement sample. 20) Formula is materialized. Thus, the coefficient u ₁ λ ₃ of the energy flux radiated to the outside from the back surface of the third layer is given by the above-described equation (21). From this result, even if the emissivity ε ₃ of the third layer is unknown, λ ₃ can be obtained by temperature measurement.
In the case of the heating method of FIG. 9A, the heat flux q can be obtained from the electric heat input amount Q, and the equation on the left side of the above equation (20) can be obtained without using the temperature of the third layer. Thus, λ ₃ can be obtained.
If the first layer and the third layer are made of the same material, λ ₁ = λ ₃ and λ ₁ is also obtained.

Subsequently, the case of a single layer material will be described.
Even when the apparent thermal conductivity k ₂ ′ is substituted into the above-described equation (16) to obtain the thermal diffusivity of the measurement sample, the constants λ ₁ and λ ₃ need to be calculated.
In this case, as described above, λ ₃ is obtained by the above-described equation (22).
Here, by making the opaque films at both ends of the measurement sample the same, λ ₁ is obtained as the same value as λ ₃ .

Next, a measuring apparatus to which the heating method (light irradiation method) in FIG. 8A is applied is shown in FIG. 11A, and a measuring apparatus to which the heating method (resistor heating method) in FIG. 9A is applied. Are shown in FIG.
A heating furnace 20 shown in FIG. 11 (A) is one in which the three-layer material 13 is disposed via a support base 21. A transparent glass 22 for irradiating the surface of the three-layer material 13 with heating light is disposed at the end (here, the upper portion) of the heating furnace 20.
The heating furnace 25 shown in FIG. 11 (B) also has a three-layer material 13 disposed therein via a support base 21. The heating furnace 25 is hermetically sealed, and the three-layer material 13 is heated using the heating elements a and b.
In the explanatory diagrams shown in FIGS. 11A and 11B, a protective heat plate that suppresses heat escape in the lateral direction (exposed side surface) of the measurement sample 10 is not particularly described. A protective heat plate may be installed on the side surface of the measurement sample to suppress heat escape from the side surface.

In any of the measuring devices, the temperature measurement is performed by a thermocouple or the like, and the measurement result is output to the temperature recording device. This measurement result is input to the computer described above. The physical property value is measured.
From the above, by using the measurement method of physical property values by the steady method of the present invention and its measurement device, a radiant heat transfer phenomenon and a diffusion heat transfer phenomenon, which have been difficult to handle in the past, are measurement samples in a coexisting state. In addition, the physical property value of the measurement sample can be obtained with high accuracy by a steady method.

  As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case in which a part of or all of the above-described embodiments and modifications are combined to constitute a physical property value measuring method and measuring device according to the stationary method of the present invention is also included in the scope of the present invention.

10: measurement sample, 11, 12: plate material, 13: three-layer material, 14: electrical resistor, 15: heating power source, 20: heating furnace, 21: support base, 22: transparent glass, 25: heating furnace

Claims (8)

In a method for measuring physical property values by a steady method, after setting a plate-shaped measurement sample to a temperature T ₀ , the surface side of the measurement sample is heated with a heat flux having a constant intensity, and the physical property value of the measurement sample is obtained.
The apparent thermal conductivity k ′ is obtained using the temperature measured on the front and back surfaces of the measurement sample and the thickness dl of the measurement sample, and depends on the thickness dl of the measurement sample and the thermal diffusivity α of the measurement sample. A method for measuring a physical property value by a steady-state method, comprising a physical property value calculating step of obtaining the thermal diffusivity α of the measurement sample as a physical property value using an equation indicating the apparent thermal conductivity k ′.   2. The method of measuring a physical property value by a steady method according to claim 1, wherein an optical thickness μdl which is a product of an absorption coefficient μ and a thickness dl of the measurement sample is obtained before the physical property value calculating step. The determination of whether the heat conduction from the front surface to the back surface of the measurement sample is caused by diffusion heat transfer or radiation heat transfer is performed based on the thickness μdl. Measuring method.   3. The method for measuring physical property values by the steady method according to claim 1 or 2, wherein a material having a known thermal conductivity and heat transfer caused by diffusion heat transfer is closely arranged on the front and back surfaces of the measurement sample, or is not A method for measuring a physical property value by a steady method, wherein a light-transmitting film is formed and the surface side of the measurement sample is heated by continuous irradiation with heating light.   3. The method for measuring physical property values by the steady method according to claim 1 or 2, wherein a heating element a is disposed in close contact with the surface of the measurement sample, and heat transfer is diffused on the back surface of the measurement sample with a known thermal conductivity. A method for measuring a physical property value by a steady method, wherein a material generated by heat transfer is closely arranged or an opaque film is formed, and the heating element a is controlled by heating.   3. The method of measuring a physical property value by a steady method according to claim 1 or 2, wherein a heating element a is disposed in close contact with the surface of the measurement sample, and a heating element b is disposed with a gap from the heating element a. The method of measuring physical property values by a steady method, wherein the heating element a and the heating element b are controlled to be heated to the same temperature.   6. The method for measuring physical property values by a steady method according to claim 5, wherein the heating element a has a thermal conductivity known, a material in which heat transfer is caused by diffusion heat transfer, or an opaque film, It is arranged on the surface of a measurement sample, and on the back surface of the measurement sample, a material having a known thermal conductivity, heat transfer caused by diffusion heat transfer is closely arranged, or an opaque film is formed A method for measuring physical properties by a steady method.   7. The physical property value measuring method according to claim 5 or 6, wherein the heating element b covers the heating element a.   A measuring apparatus used in the method for measuring a physical property value by the steady method according to claim 3, wherein the measuring sample is disposed inside, a heating furnace provided at an end of the heating furnace, and a surface side of the measuring sample And a transparent glass for continuously irradiating with heating light.

Images