JP2008309729A - Device and method for measuring thermal conductivity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for measuring thermal conductivity capable of accurately measuring thermal conductivity of an object to be measured having elasticity and an object to be measured having a large contact thermal resistance, and a method therefor. <P>SOLUTION: The device for measuring thermal conductivity comprises: a heating-side rod and a cooling-side rod which are oppositely arranged so as to hold an object to be measured with each end of the rods a temperature sensor provided on each of the rods; a heating unit provided other end of the heating-side rod; and a cooling unit provided at other end of the cooling-side rod, which provides a thermal flow from the heating unit to the cooling unit and measures the temperature gradient between the heating-side rod and the cooling-side rod by a temperature sensor; and calculates the thermal conductivity of the object using the temperature gradient of the object which is calculated by the temperature gradient and the film thickness of the object. The device also comprises a film thickness measuring unit that measures the film thickness of the object at a plurality of points in which the film thickness of the object is determined by the film thickness measured by the film thickness measuring unit. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a measurement apparatus and measurement method for the thermal conductivity of a measurement object, and in particular, a measurement apparatus and measurement for accurately measuring the thermal conductivity of a measurement object having elasticity and a measurement object having a large contact thermal resistance. Regarding the method.

FIG. 5 is a schematic diagram of a conventional thermal conductivity measuring device, indicated as a whole by 500.
In the thermal conductivity measuring apparatus 500, the heating side rod 21 and the cooling side rod 22 whose thermal conductivity krot is known in advance are provided above and below the measured object 23, and the uppermost part of the heating side rod 21 is heated by the heating block 11. The lowermost part of the cooling side rod 22 is cooled by the cooling block 12. A heater 10 is inserted into the heating block 11, and a refrigerant flows through the cooling block 12. Holes are provided in the heating side rod 21 and the cooling side rod 22 at predetermined intervals for temperature distribution measurement, and temperature measurement sensors 41 and 42 are embedded in the holes. In addition, an additional force device 15 for controlling the contact surface pressure between the rods 21 and 22 and the measured object 23 is disposed above the heating block 11, and a load cell 13 is installed for measuring the contact surface pressure. Has been.

When the heat flux passing through the measured object 23, the temperature difference in the z-axis direction, and the film thickness in the z-axis direction are q, ΔT, and ts, respectively, the thermal conductivity ku of the measured object 23 is
ku = q / (ΔT / ts)
(For example, refer nonpatent literature 1).
LSFlether et al., "Themal Conductance of Multilayered Metalic Sheets", AIAA26th Thermophysics Conference, June 24-26,1991, Honolulu Hawaii

  However, as is clear from the above equation, the thermal conductivity ku is greatly influenced by the measurement accuracy of the thickness ts of the measurement target 23. Therefore, for example, when the measured object 23 is a soft material such as grease or rubber, the thickness changes during measurement due to thermal expansion of the measured object or a change in contact pressure. It became accurate and it was difficult to obtain an accurate thermal conductivity.

  Also, when a contact thermal resistance occurs due to the presence of a film such as air on the contact surface between the measured object 23, the heating side rod 21 and the cooling side rod 22, ΔT becomes inaccurate, and an accurate thermal conductivity is obtained. It was difficult.

  Therefore, an object of the present invention is to provide a thermal conductivity measuring device and a measuring method capable of accurately measuring the thermal conductivity of a measured object having elasticity or a measured object having a large contact thermal resistance.

  The present invention relates to a heating side rod and a cooling side rod that are arranged so as to oppose each other to be measured at one end thereof, a temperature sensor provided on each of the heating side rod and the cooling side rod, and a heating side rod. A heating means provided at the other end of the cooling side and a cooling means provided at the other end of the cooling side rod. A heat flow is applied from the heating means to the cooling means, and the temperature sensor detects whether the heating side rod and the cooling side rod are A thermal conductivity measurement device that measures the thermal conductivity of the measured object from the measured object temperature gradient in the measured object and the measured object film thickness of the measured object, measured from the temperature gradient. The thermal conductivity measuring device further includes a film thickness measuring means for measuring the measured object film thickness at a plurality of points, and the measured object film thickness is determined based on the measured film thickness of the film thickness measuring means. This is a thermal conductivity measuring device.

  The present invention also includes a step of sandwiching a measurement object between a heating side rod and a cooling side rod, and a heat flow from the upper end of the heating side rod to the lower end of the cooling side rod, in the heating side rod and in the cooling side rod. A measuring step for measuring the temperature gradient of the measuring object, a step for obtaining a measuring body temperature gradient (ΔT) in the measured body from the measurement result of the temperature gradient of the heating side rod and the cooling side rod, and a measured body during the measuring step From the process of measuring the film thickness of the measured object at a plurality of points to obtain the measured object film thickness (ts), the measured object temperature gradient (ΔT) and the measured object film thickness (ts), the thermal conductivity of the measured object ( and a step of obtaining ku).

  According to the present invention, it is possible to accurately obtain the thermal resistance value of the measured object even when the measured object has elasticity or when the contact thermal resistance is generated between the measured object and the rod.

  FIG. 1 is a schematic diagram of a thermal conductivity measuring apparatus according to an embodiment of the present invention, the whole being represented by 100, FIG. 1 (a) is a schematic diagram of the entire apparatus, and FIG. The sectional view of the cooling side rod 22 when FIG. 1A is viewed in the AA direction is shown. 1, the same reference numerals as those in FIG. 5 indicate the same or corresponding parts.

  As shown in FIG. 1 (a), in the thermal conductivity measuring device 100, a measured object 23 such as grease or rubber is sandwiched between two rods 21 and 22. The upper rod of the measured object 23 as viewed in the z-axis direction (vertical direction) is referred to as a heating side rod 21 and the lower rod is referred to as a cooling side rod 22.

  The heating side rod 21 and the cooling side rod 22 are provided with a plurality of holes along the z-axis direction. In each hole, for example, a thermocouple is measured in order to measure the temperature distribution in the z-axis direction in the rod. The rod temperature measuring sensors 41 and 42 constituted by are inserted. The material of the rods 21, 22 includes copper (thermal conductivity 400W / mK), aluminum (thermal conductivity 200W / mK), stainless steel SUS304 (thermal conductivity 16W / mK), etc. It is preferable to select a material in which the difference in temperature generated between ΔT and the entire length of each of the rods 21 and 22 is approximately the same.

  A heating block 11 to which the heater 10 is attached is arranged on the opposite side of the surface of the heating side rod 21 that contacts the measured object 23. A ceramic heater or the like is used as the heater 10. In order to reduce the temperature difference in the heating block 11, it is preferable to use copper or the like having a high thermal conductivity for the heating block 11.

  On the opposite side of the surface of the cooling side rod 22 that contacts the object to be measured 23, the cooling block 12 in which the refrigerant flows is arranged. In order to reduce the temperature difference in the cooling block 12, it is preferable to use copper or the like having a high thermal conductivity for the cooling block 12 as well.

  On the heating block 11, a heat insulating support member 14 and a load cell 13 for measuring the contact surface pressure are provided. The support member 14 is provided so that heat is transmitted from the heating block 11 and the load cell 13 does not reach a high temperature. As the support member 14, Teflon (registered trademark), ceramic, or the like having a low thermal conductivity is used in order to increase heat insulation.

  A pressure is applied to the load cell 13 by an additional force device 15 via a spring 15a. In FIG. 1, a slide-type pressurization device that operates by a screw mechanism is shown as the additional force device 15, but a pressurization device having another configuration may be used.

  On the other hand, the cooling block 12 and the cooling side rod 22 are provided with a plurality of holes penetrating them from below, and contact type displacement measuring rods (contact type displacement meter probes) 62 are respectively inserted therein. . The contact-type displacement measuring rod 62 is made of, for example, a stainless steel rod having a diameter of about 1 mm and a length of about 50 mm.

  For example, when the cross section of the measured object 23 is 50 mm × 50 mm, five contact displacement measuring rods 62 having a diameter of 1 mm are arranged as shown in FIG.

Next, operation | movement of the thermal conductivity measuring apparatus 100 concerning this Embodiment is demonstrated.
As described above, the measured object 23 is sandwiched between the two rods 21 and 22 and fixed using the additional force device 15. The cross-sectional areas of the two rods 21 and 22 and the measured object 23 are substantially the same. The cross-sectional shape may be a rectangle, a circle, or the like in addition to a rectangle.

When the heating block 11 is heated and the cooling block 12 is cooled, heat flows from the heating block 11 to the heating side rod 21, passes through the measurement object 23, and flows out from the cooling side rod 22.
FIG. 2 shows the temperature distribution at this time. In FIG. 2, the horizontal axis is the measurement position in the vertical direction, and the vertical axis is the temperature of the rods 21 and 22 measured by the rod temperature measurement sensors 41 and 42.
In FIG. 2, when the heat flow velocity flowing from the heating block 11 to the cooling block 12 is q, q is expressed by the following (formula 1).

Here, q ₁ is a heat flux (W / m ² ) flowing from the heating side rod 21 to the measured body 23, and q ₂ is a heat flux (W / m ² ) flowing from the measured body 23 to the cooling side rod 22. It is. The heat fluxes q ₁ and q ₂ are given by the following (formula 2) and (formula 3).

  Therefore, the thermal resistance Rc between the two rods 21 and 22 is obtained from (Equation 4) from the measured temperature gradient of the two rods 21 and 22.

  Here, the thermal resistance Rc depends on the contact pressure between the two rods 21 and 22 and the measured object 23. Therefore, the temperature gradient is measured for each predetermined pressure value while varying the contact pressure between the two rods 21 and 22 and the measured object 23 using the additional force device 15 and the load cell 13. The thermal resistance Rc is obtained.

  Next, when it is desired to examine the thermal conductivity ku of the measurement object 23, temperature measurement sensors are respectively embedded in a plurality of holes provided in the measurement object 23 having a thickness in the z-axis direction. Measure the axial temperature gradient. At this time, the heat flux q passing through the measurement object 23 is defined by (Equation 5).

  Therefore, the thermal conductivity ku of the measured object 23 is obtained by (Equation 6) using the temperature gradient of the measured object 23.

  On the other hand, when the thickness of the measured object 23 is very thin and a plurality of holes cannot be provided, the temperature gradient of the measured object 23 in the z-axis direction is expressed by ΔT (Equation 4) (Temperature difference obtained from extrapolation line of each temperature gradient) and may be substituted into (Equation 6).

  In this case, the thermal conductivity ku of the measurement object 23 is obtained as follows from (Equation 7).

ku = q / (ΔT / ts) (Formula 7)
However, ts is the thickness (m) of the measured object 23.

  Thus, it can be seen from (Equation 7) that the thermal conductivity ku is greatly affected by the measurement accuracy of the thickness ts of the measurement target 23. For example, when the measured object 23 is a soft material such as grease or rubber, the thickness changes due to thermal expansion of the measured object or a change in contact pressure, and the value of the thermal conductivity ku becomes inaccurate.

  On the other hand, in the thermal conductivity measuring device 100, by providing a plurality of contact-type displacement measuring rods 62, the thickness ts of the measured object 23 is measured, and the value of the thermal conductivity ku is obtained with higher accuracy.

A method for measuring the thickness ts of the measurement target 23 will be described below.
FIG. 3 shows a method for calibrating the displacement of the contact-type displacement measuring rod 62. The displacement calibration block 63 is a jig used for displacement calibration of the contact-type displacement measuring rod 62. The displacement calibration block 63 is flat on one side and is provided with a recess having a known depth Hb on the other side.

  In the displacement calibration step, the calibration work is performed by placing the displacement calibration block 63 before placing the measurement object 23 on the cooling side rod 22. FIG. 3A shows a case where the measured object 23 is placed with the flat surface down, and corresponds to a case where the displacement is zero. On the other hand, FIG. 3B shows a case where the surface having the concave portion is placed downward, and the displacement is a known value Hb.

  As shown in FIGS. 3A and 3B, the contact-type displacement measuring rod 62 expands and contracts depending on the presence or absence of a recess in the displacement calibration block 63. The degree of expansion / contraction is converted into an electric signal and measured as a measured value of displacement 0 and Hb. Here, displacement calibration of the contact-type displacement measuring rod 62 is performed using these displacement amounts and measured values.

  Subsequently, a through hole is provided in the film thickness direction in the measured object 23, and the measured object 23 is placed on the cooling side rod 22 so that the contact-type displacement measuring rod 62 passes through the through hole. Further, the heating-side rod 21 is placed on the upper portion so that the tip of the contact-type displacement measuring rod 62 abuts. Thereby, the displacement amount of the contact-type displacement measuring rod 62 becomes equal to the thickness of the measured object 23, and the thickness ts of the measured object 23 can be accurately measured. As a result, the thermal conductivity ku of the measured object 23 can be obtained with high accuracy from (Equation 1) and (Equation 7).

  In particular, as shown in FIG. 1B, since the thickness ts is measured at a plurality of positions of the measured object 23 using a plurality of contact-type displacement measuring rods 62, the measured object 23 is tilted and has a thickness. Even when ts is not constant in the plane, the thermal conductivity ku of the measured object 23 can be accurately obtained by obtaining the average thickness from a plurality of measurement results.

  Next, consider a case where a film such as air exists on the contact surface between the measured object 23 and the heating side rod 21 and the cooling side rod 22 to generate the contact thermal resistance Rs. When there is the contact thermal resistance Rs, the temperature difference ΔT obtained from the extrapolated line of the temperature gradient in the two rods 21 and 22 as shown in FIG. 2 does not become the actual temperature difference of the measured object 23.

  In such a case, by using the additional force device 15 to increase or decrease the contact surface pressure, the thickness ts of the measured object 23 is changed, and the thermal resistance Rc at that time is measured by the two rods 21, It is calculated from (22) temperature gradient by (Equation 4).

FIG. 4 shows the relationship between the test side thickness (ts) of the measurement body 23 and the thermal resistance Rc at that time. The horizontal axis represents the test side thickness (ts) of the measurement body 23 and the vertical axis represents (Expression 4). The thermal resistance ( _RC ) calculated | required from is shown. From the slope of the straight line shown in FIG. 4, the change in Rc (dRc / dts) with respect to the thickness ts of the measured object 23 is obtained.

  Here, the thermal resistance Rc of the measurement object 23 including the two contact surfaces is expressed by the following (formula 8).

          Rc = 2 × Rs + ts / (ku · A) (Formula 8)

  Therefore, by differentiating (Equation 8) by ts, the thermal conductivity ku of the measured object 23 is expressed by the following (Equation 9).

          ku = 1 / (dRc / dts · A) (Formula 9)

  Accordingly, the change in Rc (dRc / dts) with respect to the thickness ts of the measured object 23 is obtained from the slope of FIG. 4 and substituted into (Equation 9), whereby the thermal conductivity ku can be obtained accurately. .

  As described above, by using the thermal conductivity measurement device and measurement method according to the present embodiment, the object to be measured is made of an elastic body such as grease or rubber, and the film thickness changes nonuniformly during measurement. Even so, the thermal conductivity can be accurately determined by measuring the film thickness of the object to be measured at a plurality of points.

  In addition, by using the other thermal conductivity measuring device and measuring method according to the present embodiment, a film such as air exists on the contact surface between the measured object, the heating side rod, and the cooling side rod. Even when thermal resistance occurs on the surface, the thermal conductivity of the measurement object can be accurately obtained.

1 is a thermal conductivity measuring device according to an embodiment of the present invention. It is a temperature distribution of the rod and to-be-measured body of the thermal conductivity measuring apparatus concerning embodiment of this invention. It is the displacement calibration method of the contact-type displacement measuring rod concerning embodiment of this invention. It is the relationship between the test side thickness (ts) of the measurement object and the thermal resistance (Rc) at that time. It is a conventional thermal conductivity measuring device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Heater, 11 Heating block, 12 Cooling block, 13 Load cell, 14 Support member, 15 Applied force apparatus, 15a Spring, 21 Heating side rod, 22 Cooling side rod, 23 Measured object, 41, 42 Rod temperature measurement sensor, 62 Contact-type displacement measuring rod, 100 thermal conductivity measuring device.

Claims (5)

A heating side rod and a cooling side rod, which are opposed to each other so as to sandwich the object to be measured at each end;
A temperature sensor provided in each of the heating side rod and the cooling side rod;
Heating means provided at the other end of the heating side rod;
Cooling means provided at the other end of the cooling side rod,
A heat flow is applied from the heating means to the cooling means, a temperature gradient between the heating side rod and the cooling side rod is measured by the temperature sensor, and a measured object temperature in the measured object calculated from the temperature gradient. A thermal conductivity measuring device that calculates the thermal conductivity of the measured object from the gradient and measured object film thickness of the measured object,
The thermal conductivity measuring device further includes a film thickness measuring means for measuring the measured film thickness at a plurality of points, and the measured film thickness is determined based on the measured film thickness of the film thickness measuring means. A thermal conductivity measuring device characterized by.   The said film thickness measurement means consists of a contact-type displacement measuring rod arrange | positioned so that the said to-be-measured body may be penetrated from the said cooling side rod side, and it may contact | connect the said heating side rod. Thermal conductivity measuring device.   A pressure means for pressurizing the measurement object between the heating side rod and the cooling side rod; and the thermal conductivity of the measurement object in a state where the measurement object is pressurized by the pressure means. The thermal conductivity measuring device according to claim 1, wherein the thermal conductivity measuring device is calculated. Sandwiching the object to be measured between the heating side rod and the cooling side rod;
A measurement step of flowing a heat flow from the upper end of the heating side rod to the lower end of the cooling side rod, and measuring a temperature gradient in the heating side rod and in the cooling side rod;
A step of obtaining a measured object temperature difference (ΔT) in the measured object from a measurement result of a temperature gradient of the heating side rod and the cooling side rod;
Measuring the film thickness of the object to be measured at a plurality of points during the measuring step, and determining the film thickness (ts) of the object to be measured;
A method of measuring a thermal conductivity, comprising: determining a thermal conductivity (ku) of the measured object from the measured object temperature difference (ΔT) and the measured object film thickness (ts). The object to be measured is pressurized between the heating side rod and the cooling side rod, and the heating side rod and the cooling side are in a plurality of states in which the film thickness (ts) of the object to be measured differs depending on the pressure. Obtaining a thermal resistance (Rc) between each of the rods;
The thermal conductivity (ku) of the object to be measured is expressed by the following formula:
ku = 1 / (dRc / dts · A)
The method of measuring thermal conductivity according to claim 4, further comprising:

Images