JP4258667B2 - Thermophysical property measuring method and apparatus - Google Patents

Description

  The present invention relates to a thermophysical property measuring method in which thermal properties such as thermal diffusivity, specific heat capacity, and thermal conductivity of various substances can be measured from a sample temperature response by periodically heating the sample to be measured, and its It relates to an apparatus for carrying out the method.

It is strongly desired to accurately measure thermal properties such as thermal diffusivity, specific heat capacity, thermal conductivity, etc., related to heat transfer and accumulation for constituent materials of various devices. In measuring the specific heat capacity, the conventional thermophysical property measuring apparatus performs temperature control by changing the heat generation of the heater, as shown in, for example, Patent Document 1 (Method and apparatus for measuring thermophysical properties) below. Was common.
JP 2005-249427 A

  This method allows efficient temperature control when the sample temperature decreases rapidly due to heat radiation, etc., when the heat generation of the heater is reduced, such as at high temperatures, but natural cooling of the sample is not possible when measuring near room temperature. Since it is slow, it takes a long time to return the temperature to the original state once the sample is heated, and a considerable amount of time is required to obtain thermophysical values at a plurality of temperatures.

  Therefore, the main object of the present invention is to provide a thermophysical property measurement method and apparatus that can easily control the temperature of the sample, can quickly control the temperature of the sample to the set temperature, and can measure quickly and accurately.

The thermophysical property measuring method according to the present invention solves the above problems based on the following principle.
(1) About thermal diffusivity measurement by periodic heating method,
When the surface of the sample is heated periodically, the phase lag δ from the AC cyclic heating of the sample temperature response of the thickness L insulated from the outside world is expressed by the following equation according to the heat capacity, thermal conductivity or thermal diffusivity of the sample. Is done.

・・・（１）
位相遅れ：

・・・（２）
周期加熱された面と反対側の面（裏面）の温度応答は
相対振幅：

・・・（３）
位相遅れ：

・・・（４）
で与えられる。ここでＢは次式により表される無次元のパラメーターである。

・・・（５）
ただしＬは試料の厚さ、ωは加熱の角周波数、αは試料の熱拡散率である。
上記の式により、試料の厚さと加熱の角周波数が既知であれば、表面または裏面の温度応答の位相遅れから試料の熱拡散率を求めることができる。また、ヒータに角周波数ωの電流を流し、ヒータの温度変化をヒータ両端間の交流電圧の３ω成分から測定することによって熱物性の測定を行うことができる。 The temperature response of the periodically heated surface is the relative amplitude:

... (1)
Phase lag:

... (2)
The temperature response of the opposite surface (back surface) to the periodically heated surface is relative amplitude:

... (3)
Phase lag:

... (4)
Given in. Here, B is a dimensionless parameter expressed by the following equation.

... (5)
Where L is the thickness of the sample, ω is the angular frequency of heating, and α is the thermal diffusivity of the sample.
If the thickness of the sample and the angular frequency of heating are known, the thermal diffusivity of the sample can be obtained from the phase delay of the temperature response on the front or back surface. In addition, it is possible to measure thermophysical properties by passing a current of angular frequency ω through the heater and measuring the temperature change of the heater from the 3ω component of the AC voltage across the heater.

・・・（６） (2) About heat capacity measurement by the periodic heating method When a standard sample A having a known heat capacity with the same bottom area (C _A ) and a sample B to be measured with a unknown heat capacity (C _B ) are installed and the heater is heated periodically Observe the temperature response. When the respective amplitudes are P _A and P _B , and the phase differences are δ _A and δ _B , the heat capacity ratio C _B / C _A is obtained as a function of P _B / P _A and δ _A and δ _B.

... (6)

Although the present invention is based on the principle as described above, a more specific thermophysical property measuring method according to the present invention is to periodically heat a sample using a thermoelectric module and a flat heater,
Thermophysical properties to obtain the temperature response of the sample by a temperature sensor installed at the same position as the heater or at a certain distance from the heater, and to determine at least one of the thermal diffusivity, specific heat capacity, and thermal conductivity of the sample by the temperature response of the sample In the measurement method, the flat heater is installed on the surface of the thermoelectric module, the sample is periodically heated, and the thermoelectric module performs heat absorption equal to the average calorific value of the flat heater so that the average temperature of the sample is constant. The temperature response of the heater is measured from the 3ω component of the AC voltage across the heater, and the sample and the temperature sensor are in thermal contact with grease or an adhesive. The thermal properties of grease or adhesive are measured by high-frequency periodic heating, and the grease or adhesive observed by low-frequency periodic heating is measured. It is characterized in that the thermophysical value of the sample is obtained by correcting the contribution of the thermophysical property of the grease or the adhesive from the signal based on the contribution of both the thermophysical value and the thermophysical value of the sample .

The thermophysical property measuring apparatus according to the present invention includes a heating means for periodically heating a sample with a thermoelectric module and a flat heater, a temperature sensor installed at the same position as the heater or at a fixed distance from the heater, and the temperature sensor. In the thermophysical property measuring apparatus provided with an arithmetic means for obtaining at least one of the thermal diffusivity, specific heat capacity, and thermal conductivity of the sample from the obtained temperature response , a flat heater is installed on the surface of the thermoelectric module, Periodically heating the flat heater, causing the thermoelectric module to perform an endotherm equal to the average calorific value of the flat heater, keeping the average temperature of the sample constant, and passing a current with an angular frequency ω to the heater, The temperature response of the heater is measured from the 3ω component of the AC voltage across the heater, and the sample and the temperature sensor are brought into thermal contact with grease or an adhesive. The calculation means measures the thermophysical value of grease or adhesive by high-frequency periodic heating, and is based on the contribution of both the thermophysical value of grease or adhesive and the thermophysical value of the sample observed by low-frequency cyclic heating. The thermophysical property value of the sample is obtained by correcting the contribution of the thermophysical property of the grease or adhesive from the signal .

  In the present invention, by attaching the thermoelectric module to the flat heater, the temperature control is simplified and the temperature of the sample can be quickly controlled to the set temperature. As a result, the measurement time was dramatically shortened.

In particular, the thermophysical property measuring method and apparatus according to the present invention enables the following various measurements.
(1) The sample is periodically heated by a thermoelectric module and a flat heater, and the thermal diffusivity, specific heat capacity, and thermal conductivity of the sample are calculated from the temperature response of the sample obtained by the heater itself or a temperature sensor installed at a certain distance from the heater. It can be determined quantitatively.
(2) A flat heater is installed on the surface of the thermoelectric module, the flat heater is periodically heated, and the thermoelectric module absorbs heat equal to the average calorific value of the flat heater to keep the average temperature of the sample constant. Therefore, the measurement time can be shortened.
(3) By using a flat heater as a temperature sensor, the configuration of the apparatus can be simplified, and the temperature response of the sample can be measured more accurately.
(4) A temperature response of the heater can be detected with high sensitivity by using a 3ω component of the AC voltage across the heater by passing a current having an angular frequency ω through the flat heater.
(5) By installing a temperature sensor on the back of the sample, the temperature response of the sample can be measured on the back of the sample.
(6) The temperature response in the creeping direction of the sample can be measured by installing a temperature sensor in a plane adjacent to the flat heater.
(7) The temperature response of the heated surface of the sample can be measured by installing a temperature sensor between the sample and the flat heater.
(8) The thermophysical property value of grease or adhesive can be measured and corrected. That is, the sample is attached to the heater with grease or an adhesive. When the heater is heated with a low frequency current, the heat diffuses through the sample through the grease or adhesive and reaches the back of the sample. In this case, a temperature response reflecting the thermal properties of both the grease or adhesive and the sample can be observed. On the other hand, when the heater is heated with a high-frequency current, the heat diffusion remains almost in the grease or adhesive, and a temperature response reflecting the thermal properties of only the grease or adhesive can be observed. Therefore, the thermal property value of the sample itself can be obtained by correcting the measurement result at the low frequency using the thermal property of the grease or the adhesive obtained by the measurement at the high frequency.
(9) Simultaneous measurement of thermophysical values of a plurality of samples and relative measurement of a sample to be measured based on the thermophysical values of a standard sample can be performed. That is, a plurality of samples are attached to a flat heater, and a temperature sensor is installed between them. Since the temperature of the heater is uniformly controlled by the thermoelectric module, the thermophysical values of a plurality of samples can be measured simultaneously. Moreover, the heat capacity of the sample to be measured can be measured by using a standard sample whose thermal diffusivity, specific heat capacity, density, and dimensions are known as one of the plurality of samples.

  The present invention has a problem that temperature control is simple and a thermophysical property can be measured quickly and accurately even when a set temperature is a steady temperature, and a sample is periodically heated by a thermoelectric module and a flat heater, This was realized by obtaining one of the thermal diffusivity, specific heat capacity, and thermal conductivity of the sample from the temperature response obtained by a temperature sensor installed at the same position as the heater or at a fixed distance from the heater.

  FIG. 1 shows the principle of a thermophysical property measuring apparatus according to the present invention. In the example shown in FIG. 1A, a flat heater 2 is installed on a thermoelectric module 1, and a flat sample 3 is installed thereon. The flat heater 2 is energized with an alternating current and periodically heated, and at the same time, the thermoelectric module 1 is used to cool the sample to control the average temperature of the sample to the set temperature. Measure with

  In the example shown in FIG. 1 (b), a flat heater / temperature sensor 5 is installed on the thermoelectric module 1, and a flat sample is installed on the heater / temperature sensor 5 by passing an alternating current. 3 is periodically heated and cooled by the thermoelectric module 1 in the same manner as described above. The heater / temperature sensor 5 measures the temperature by utilizing the fact that the resistance value varies depending on the temperature of the heater, and the current value varies depending on the temperature change even when a current is passed through the heater / temperature sensor 5 at a constant voltage. It has a function, thereby serving as both a heater and a temperature sensor.

In the example shown in FIGS. 1A and 1B, the temperature sensor is attached by adopting one of the following four methods.
(i) Using a heater as a temperature sensor [Fig. 1 (b)]
(ii) Mount the temperature sensor on the back of the sample [Fig. 1 (a)]
(iii) Mount the temperature sensor in a plane adjacent to the flat heater [Fig. 1 (a)]
(iv) Install the temperature sensor between the sample and the flat heater [Fig. 1 (a)]
The temperature change at this time is determined by the thickness, thermal diffusivity, and volumetric heat capacity of the sample. Therefore, by measuring the temperature change of the flat plate in contact with the sample, these thermophysical values of the sample 3 can be determined according to the principle of the present invention. Can be sought.

  By using the thermoelectric module 1 as described above together with the heater 2 or the heater / temperature sensor 5, conventionally, the thermophysical value is obtained in a state of being heated to a normal temperature or higher by the heater, or the ambient temperature of the measurement portion is lowered to reduce the heater. Although it was necessary to manage the sample temperature so that it was as steady as possible when heated by the sample, in the present invention, as shown in FIG. By canceling the steady rise in the temperature by cooling with the thermoelectric module, the temperature of the sample is feedback-controlled at a constant level. Therefore, the thermophysical properties can be measured quickly and accurately.

  FIG. 2 shows a method for more accurately obtaining the thermal property of the sample by evaluating the thermal property of the adhesive or grease when the sample is bonded to the heater with an adhesive or grease. In the example shown in FIG. 2, when the flat heater / temperature sensor 5 is heated with a high-frequency current as shown in FIG. 2B, the heat diffusion remains almost in the grease (adhesive) 6, and the grease ( The temperature response reflecting the thermophysical properties of the adhesive 6) can be measured. Conversely, when the flat heater / temperature sensor 5 is heated with a low-frequency current as shown in FIG. 5A, the heat is diffused through the grease (adhesive) 6 to the sample 3 and on the back surface of the sample 3. Therefore, the temperature response reflecting the thermal properties of the grease (adhesive) 6 and the sample 3 can be measured.

  Accordingly, the thermophysical value of the sample 3 can be accurately obtained by correcting the measured value using the thermophysical property of the adhesive or the grease obtained when heated with a high frequency current. In the example shown in FIG. 2, the thermophysical property value of the sample can also be obtained by measuring the temperature with the temperature sensor 4 using the heater 2 as shown in FIG.

FIG. 3 shows a method for obtaining the thermophysical value of the sample to be measured with reference to the standard sample. That is, the standard sample A and the sample B to be measured having the same bottom area are installed on the surface of the heater 2 installed on the thermoelectric module 1. When the heat capacity (C _A ) of the standard sample A is known and the heat capacity (C _B ) of the sample B to be measured is unknown, the heater 2 is periodically heated in the same manner as described above, and the temperature response at that time is observed. Since the heat capacity of the standard sample is known, the heat capacity of the sample to be measured can be obtained by obtaining the respective temperature responses (amplitude difference, phase difference) when the flat heater is periodically heated. That is, as described in the principle of the present invention, assuming that the respective amplitudes are P _A and P _B and the phase differences are δ _A and δ _B , the heat capacity ratio C _B / C _A is P _B / P _A and δ _A , it can be determined by the equation (6) as a function of [delta] _B.

  FIG. 4 shows a block diagram of a thermophysical property measuring apparatus according to the present invention. The sample 3 is periodically heated by the heater 2 to which the AC heating current generated by the amplifier 16 is supplied and cooled by the thermoelectric module 1. The temperature change at that time is measured by the temperature sensor 4, and the average temperature becomes constant. Thus, the thermoelectric module 1 is controlled. A predetermined AC signal generated by the function generator 13 is amplified by the amplifier 16 and used as a reference signal described later as a heating current for the sample 3.

  The measurement signal of the temperature sensor 4 is transmitted to the lock-in amplifier 12, and a predetermined reception signal by the function generator 13 is output to the lock-in amplifier 12 as a reference signal. The lock-in amplifier 12 amplifies a component synchronized with the reference signal of the function generator 13 in the detected signal, and obtains phase delay data with respect to the reference signal. The obtained result is subjected to data analysis by the calculation unit 15 in the personal computer 14, the thermal property value of the thermal diffusivity and the heat capacity is measured, and displayed on the personal computer 14. At this time, the steady temperature set by the temperature controller 11 is input to the calculation unit 15 and used as back data of the measured thermophysical property value.

It is a figure which shows the principle of this invention and 1st Example. It is a figure which shows the 2nd Example. It is a figure which shows the 3rd Example. It is a functional block diagram of the thermophysical property measuring apparatus by this invention.

Explanation of symbols

1 Thermoelectric Module 2 Heater 3 Sample 4 Temperature Sensor 5 Heater / Temperature Sensor

Claims (2)

The sample is periodically heated using a thermoelectric module and a flat heater,
Obtain the temperature response of the sample with a temperature sensor installed at the same position as the heater or at a fixed distance from the heater,
In the thermophysical property measurement method for obtaining at least one of the thermal diffusivity, specific heat capacity, and thermal conductivity of the sample by the temperature response of the sample ,
The plate heater is installed on the surface of the thermoelectric module to periodically heat the sample, and the thermoelectric module performs heat absorption equal to the average calorific value of the plate heater to keep the average temperature of the sample constant,
A current with an angular frequency ω is passed through the heater, and the temperature response of the heater is measured from the 3ω component of the AC voltage across the heater,
The sample and the temperature sensor are brought into thermal contact with grease or an adhesive, and the thermal property value of the grease or adhesive is measured by high-frequency periodic heating,
By correcting the contribution of the thermal properties of the grease or adhesive from the signal based on the contribution of both the thermal properties of the grease or adhesive and the thermal properties of the sample observed by low-frequency periodic heating, A thermophysical property measuring method characterized by obtaining a physical property value . Heating means for periodically heating the sample with a thermoelectric module and a flat heater;
A temperature sensor installed at the same position as the heater or at a fixed distance from the heater;
In the thermophysical property measuring apparatus comprising a calculation means for obtaining at least one of the thermal diffusivity, specific heat capacity, and thermal conductivity of the sample from the temperature response obtained by the temperature sensor ,
Installing a flat heater on the surface of the thermoelectric module, periodically heating the flat heater,
The thermoelectric module performs heat absorption equal to the average calorific value of the flat heater to keep the average temperature of the sample constant,
A current with an angular frequency ω is passed through the heater, and the temperature response of the heater is measured from the 3ω component of the AC voltage across the heater,
The sample and the temperature sensor are brought into thermal contact with grease or an adhesive, and the arithmetic means measures the thermal property value of the grease or adhesive by high-frequency periodic heating, and the grease or Thermophysical property of a sample is obtained by correcting the contribution of the thermal property of grease or adhesive from the signal based on the contribution of both the thermal property value of the adhesive and the sample. measuring device.

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