JPH0750051B2 - Thermal conductivity measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal conductivity measuring device suitable for measuring the thermal conductivity of various materials such as heat insulating materials and heat insulating materials, especially at high temperatures. .

“Prior Art” Generally, the values of thermal conductivity of various materials used as heat insulating materials and heat insulating materials are not always constant but change with temperature. The higher the temperature, the higher the thermal conductivity. That is, heat tends to be easily transmitted. Therefore, especially in the case of a material whose thermal conductivity at high temperature is a problem, such as a heat insulating material or a heat insulating material used in a temperature condition exceeding 1,000 ° C., the measurement of its thermal conductivity is actually performed. It is necessary to heat it up to the use temperature.

A device shown in FIG. 4 is known as a device for measuring such thermal conductivity. In this conventional thermal conductivity measuring device, a main heater b and an auxiliary heater c are arranged in an upper portion and a lower portion of a protective cylinder a having a heat insulating property to generate a steady downward heat flow in the protective cylinder a. In addition, a heat flow measurement plate d for measuring the heat flow rate of the steady heat flow is provided above the auxiliary heater C. In this thermal conductivity measuring device, a sample S whose thermal conductivity is to be measured is arranged at a central position in a protective cylinder a, and standard heat transfer plates s ₁ and s ₂ whose thermal conductivity is known are arranged above and below the sample S. Main heater b, auxiliary heater c
By this, a thermal equilibrium state shown by a broken line A in the drawing is created inside the protective cylinder a to form a temperature gradient like a broken line B on the sample S and the standard heat transfer plates s ₁ and s ₂ . And
The average internal temperature of the sample S is kept at a temperature to be measured, and the temperature at the upper surface and the lower surface of the sample S is measured by the thermometer e,
Measured by e, the temperature difference between them and the heat flow measurement plate d
The thermal conductivity of the sample S at that temperature is calculated from the heat quantity of the steady heat flow measured by, that is, the heat transmission flow rate that has passed through the sample S.

That is, the heat transmission flow rate is Q (Kcal / h), the thermal conductivity of the sample S is λ (Kcal / m · h · deg), and the thickness dimension of the sample S is t.
(M), the effective area of the sample S is A (m ² ), and the upper surface temperature and the lower surface temperature of the sample S are θ ₁ and θ ₂ (° C.), respectively, Q = (λ / t) · A (θ ₁ − Since the relationship of θ ₂ ) is established, λ can be obtained from this equation as λ = Q · t / A (θ ₁ −θ ₂ ) ... (1).

The standard heat transfer plates s ₁ and s ₂ are for keeping the temperature of the sample S at a high temperature, and the surface temperature of the sample S is measured by a thermometer f ... By comparing the value of the thermal conductivity obtained from the above and the above-mentioned heat transmission flow rate Q with the known value of the thermal conductivity, the measured value is verified and corrected if necessary.

Further, reference characters g ... Are heaters for wall surface temperature compensation, and these heaters g ... Control the surface temperature of the protective cylinder a so that the temperature gradient inside the protective cylinder a is in the state of A. This is to prevent heat transfer between the protective cylinder a and the internal space thereof and prevent the heat flow from radiating from the peripheral surface of the protective cylinder a.

[Problems to be Solved by the Invention] In the conventional thermal conductivity measuring device, the value of the heat transmission flow rate Q passing through the sample S must be accurately measured in order to obtain sufficient measurement accuracy. Of course, the heat flow inside the protective cylinder a must be
It is important that heat is not dissipated to the outside through the peripheral surface, that is, the heat flow does not flow only from the top to the bottom and flows to the side.

For this reason, in the above-mentioned conventional device, the heaters g for wall surface temperature compensation are provided, but this is not enough, and in particular, the lateral sides from the standard heat transfer plates s ₁ and s ₂ are not provided. However, the accuracy of measuring the heat transmission flow rate Q in the calorie measuring device d cannot be said to be sufficiently high.

The heat loss from the standard heat transfer plates s ₁ and s ₂ to the side is not a problem when the standard heat transfer plates s ₁ and s ₂ are sufficiently thin, but When measuring the conductivity, it is necessary to keep the sample S at a high temperature as described above,
For this reason, the thickness of the standard heat transfer plates s ₁ and s ₂ must be increased, and in this case, the amount of heat loss from the standard heat transfer plates s ₁ and s ₂ to the side cannot be ignored. It will be a big one.

The present invention has been made in view of the above circumstances, can effectively prevent lateral heat loss from the standard heat transfer plate, and is particularly suitable for use when measuring thermal conductivity at high temperatures. An object is to provide a thermal conductivity measuring device.

"Means for Solving the Problem" This invention provides a measurement chamber whose periphery is covered with a heat insulating material inside a furnace vessel, and arranges a sample whose thermal conductivity is to be measured in the measurement chamber. A standard heat transfer plate of known conductivity is placed in close contact with at least the lower surface of the sample, and a steady heat flow from the upper part to the lower part of the measurement chamber is generated to hold the sample at a desired set temperature, and The thermal conductivity at the preset temperature of the sample is measured from the value of the thermal penetration flow rate and the temperature difference by measuring the thermal penetration flow rate of the steady heat flow that has passed through the sample and the temperature difference between the upper surface temperature and the lower surface temperature of the sample. In the thermal conductivity measuring device configured to measure, the standard heat transfer plate is formed by closely winding a thin plate-shaped heat insulating material in a spiral shape, and the heat in the radial direction thereof is measured. The value of conductivity becomes the value of thermal conductivity in the thickness direction. It is characterized by being made smaller than that.

"Operation" Since the standard heat transfer plate in the thermal conductivity measuring device of the present invention has a shape in which a thin plate-shaped heat insulating material is wound in a spiral shape, its radial thermal conductivity is in the thickness direction. The standard heat transfer plate is smaller than the heat transfer rate, that is, this standard heat transfer plate is easy to transfer heat in the thickness direction but hard to transfer heat in the radial direction. It is suppressed that the flow in the inside only flows downward and the flow in the lateral direction, so that the heat loss from the standard heat transfer plate to the side is naturally prevented.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an elevational sectional view showing a schematic configuration of a thermal conductivity measuring apparatus according to an embodiment of the present invention, and FIG. 2 is a perspective view of a standard heat transfer plate used in this apparatus.

In FIG. 1, reference numeral 1 is a furnace container, and this furnace container 1
Comprises a body 2 each having a water cooling jacket and a lid 4 connected to the body 2 by a hinge 3.

Inside the furnace vessel 1, a disk-shaped lower heat insulating material 5,
By the upper heat insulating material 6 and the cylindrical side heat insulating material 7,
A measurement chamber 8 in which the sample S is arranged is formed. A main heater 9 for keeping the inside of the measuring chamber 8 at a predetermined temperature is attached to the upper space of the measuring chamber 8, and the inner surface temperature of the lower insulating member 5 is heated by the heat flow in the lower insulating member 5. A compensation heater 10 for keeping the temperature equal to that of a measuring plate 15 (described later) is embedded, and the main heaters 9 thereof are
The compensating heater 10 is connected with electrodes 11 and 12 penetrating the lid 4 and the main body 2 of the furnace vessel 1. Reference numeral 13 is a radiation thermometer for measuring the temperature in the measurement chamber 8.

In addition, the inner surface of the side heat insulating material 7 forming the side wall of the measurement chamber 8 has a sufficient heat resistance and excellent heat conductivity, for example, Grainite, heat resistant steel, molybdenum, etc. Is covered with a wall surface temperature compensating plate 14 formed in a cylindrical shape.

Further, a disk-shaped heat flow measuring plate 15 is arranged in the center of the upper surface of the lower heat insulating material 5, and an annular compensating cooling plate 16 is arranged around it. The heat flow measurement plate 15 has a flow passage for the temperature measurement gas for measuring the heat transmission flow rate formed in a spiral shape, and the temperature measurement gas is circulated in the flow passage as indicated by an arrow in the figure. A gas inlet pipe 17 and a gas outlet pipe 18 are connected to each other. Further, in the compensating cooling plate 16, a flow passage for circulating the cooling gas is formed in a spiral shape, and a cooling gas introducing pipe 19 for circulating the cooling gas as shown by an arrow in the drawing, a cooling The gas outlet pipes 20 are respectively connected. The temperature measuring gas and cooling gas are
After the gas preheaters 21 and 22 embedded in the lower heat insulating material 5 bring them to a predetermined temperature, the heat flow measuring plate 1
5, the compensating cooling plate 16 is to be introduced. Although not shown, thermometers for measuring the inlet temperature and the outlet temperature of the temperature measuring gas and the inlet temperature and the outlet temperature of the cooling gas are respectively provided.

The heat flow measuring plate 15 measures the temperature at the inlet and the outlet of the temperature measuring gas to obtain the heat receiving amount of the temperature measuring gas from the temperature difference and the gas flow rate, that is, the heat transmission flow rate through the sample S. Is for measuring. Further, the compensating cooling plate 16 arranged around the same is for preventing heat transfer between them by being kept at the same temperature as the heat flow measuring plate 15.

A temperature measuring plate 23 is arranged on the upper surfaces of the heat flow measuring plate 15 and the compensating cooling plate 16, and a disc-shaped standard heat transfer plate 24 made of a material whose thermal conductivity is known is arranged on the upper surfaces thereof. . This standard heat transfer plate 24 is the standard heat transfer plate in the conventional device described above.
Similar to s ₁ and s ₂ , the temperature of the sample S is kept at a high temperature, and the temperatures of the upper and lower surfaces of the sample S are measured by a thermometer (not shown) inserted in the temperature measuring plate 23 and This is for verifying and correcting the measured value by measuring with a thermocouple thermometer 27 inserted in the lower temperature measuring plate 25, and the temperature difference between them and the known thermal conductivity.

As shown in FIG. 2, the standard heat transfer plate 24 has a laminated structure in which a thin plate-shaped heat insulating material 24a, for example, a carbon fiber molding plate is densely wound in a spiral shape. Since the thin plate-shaped heat insulating material 24a is wound in this manner, the heat conductivity of the standard heat transfer plate 24 in the thickness direction is 2 to 3 times that of the radial direction. It is getting bigger. That is, the standard heat transfer plate 24 easily transfers heat in its thickness direction but hardly transfers heat in the radial direction.

A lower temperature measuring plate 25 is disposed on the upper surface of the standard heat transfer plate 24, a sample S whose thermal conductivity is to be measured is disposed on the upper surface thereof, and an upper temperature plate 26 is disposed on the upper surface thereof. It is like this. Thermocouple thermometers 27 and 28 are inserted in the lower temperature plate 25 and the upper temperature plate 26, respectively, so that the temperature of the upper surface and the lower surface of the sample S can be measured by these thermocouple thermometers 27 and 28. Has been done.

In order to measure the thermal conductivity λ of the sample S at a high temperature with the apparatus having the above-described configuration, first, the sample S is placed in the measurement chamber 8, the upper measurement plate 26 is placed on the upper surface thereof, and the upper measurement is performed. Board
Insert thermocouple thermometer 28 into 26. Then, the measurement chamber 8 is closed by the upper heat insulating material 6, the lid 4 of the furnace vessel 1 is closed, and the measurement chamber 8 is closed by the main heater 9 and the compensation heater 10.
The inside is heated to a predetermined set temperature, and the internal temperature of the sample S is maintained at the temperature T ° C. at which the thermal conductivity should be measured. Further, the temperature measurement gas and the cooling gas are heated to a predetermined temperature by the preheaters 21 and 22, respectively, and are made to flow through the heat flow measurement plate 15 and the compensating cooling plate 16, and the temperatures thereof are kept equal.

When the temperature in the measurement chamber 8 and the internal temperatures of the sample S and the standard heat transfer plate 24 are in a steady state, the temperature θ of the upper and lower surfaces of the sample S is θ.
_While measuring ₁ and θ ₂ with thermocouple thermometers 28 and 27,
The temperature of the inlet and outlet of the temperature measuring gas flowing through the heat flow measuring plate 15 is measured. Then, from the temperature difference of the temperature measuring gas and the flow rate thereof, the amount of heat received, that is, the heat transmission flow rate Q that has passed through the sample S is obtained, and the heat transmission flow rate Q and the temperatures θ ₁ ,
From θ ₂ and the thickness dimension t of the sample S, the thermal conductivity λ of the sample S at the temperature T is obtained by using the above equation (1).
In this case, the effective area A of the sample S is the area of the heat flow measuring pair 15.

Further, the temperature difference between the upper and lower sides of the standard heat transfer plate 24 is also measured, and the thermal conductivity (heat conductivity in the thickness direction) of the standard heat transfer plate 24 is obtained from those values and the above-described heat penetration flow rate Q, The measurement result may be verified by comparing the value with a known value of thermal conductivity (thermal conductivity in the thickness direction), and may be corrected if necessary.

The thermal conductivity measuring device described above, as the standard heat transfer plate 24, by a thin plate-shaped heat insulating material 24a is wound in a spiral shape, the thermal conductivity in the radial direction of the thickness direction Since the one that is made smaller than the thermal conductivity is used, the steady heat flow that has passed through the sample S is suppressed from flowing only in the standard heat transfer plate 24 toward the lower side and thus toward the side. The heat loss to the side of the heat transfer plate 24 is naturally suppressed, and as a result, the heat transmission flow rate Q can be accurately measured and the measurement accuracy can be improved.

In addition, since this apparatus is provided with the wall surface temperature compensating plate 14 made of a good heat conductive material on the inner surface of the measuring chamber 8, the temperature of the compensating plate 14 is reduced by the heat transfer action of itself. In response to this, the inside of the measurement chamber 8 is naturally maintained at substantially the same temperature and at a temperature balanced by the heat escaping through the side heat insulating material 7 as the distance increases, so that the standard heat transfer plate 24 and the compensating plate are maintained. The temperature difference with 14 is naturally eliminated, and the steady heat flow is prevented from being radiated through the side heat insulating material 7. Therefore, also in this respect, it is possible to improve the measurement accuracy of the heat transmission flow rate Q, and it is not necessary to provide the heater g for wall surface temperature compensation in the conventional device, so that the device can be simplified and downsized.

In the above embodiment, a carbon fiber molded plate is illustrated as the thin plate-shaped heat insulating material 24a forming the standard heat transfer plate 24, but other materials may be used as long as they have heat insulating properties and heat resistance. Of course good things. Further, as shown in FIG. 3, the standard heat transfer plate 30 may be formed by overlapping and winding two thin plates made of different materials. In this case, one of the two thin plates is a thin plate-shaped heat insulating material 30a.
For example, if alumina silica paper or the like is used and the other is a good heat conductive material such as a metal plate 30b, good heat conductivity can be ensured by the metal plate 30b in the thickness direction and heat insulation can be performed in the radial direction. Heat conduction is suppressed by the material 30a, and it is possible to increase the ratio between the heat conductivity in the thickness direction and the heat conductivity in the radial direction. In addition, the combination of graphite insulation and graphite foil wound in multiple layers is also effective for higher temperature applications.

Further, in the above embodiment, the standard heat transfer plate is provided only on the lower surface side of the sample, but the standard heat transfer plate formed in the same manner as above may be provided on the upper surface side of the sample.

"Effects of the Invention" As described in detail above, the thermal conductivity measuring device of the present invention is formed by densely winding a thin plate-shaped heat insulating material in a spiral shape and has a radial thermal conductivity of Since a standard heat transfer plate that is smaller than the thermal conductivity in the direction is used, heat loss to the side of this standard heat transfer plate is naturally suppressed, and as a result, the heat transmission flow rate can be accurately measured. Therefore, the measurement accuracy can be improved, and therefore, it is suitable for use in the measurement of the thermal conductivity under a high temperature where it is particularly necessary to increase the thickness of the standard heat transfer plate.

[Brief description of drawings]

FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is an elevational sectional view showing the overall schematic structure of the thermal conductivity measuring apparatus of this embodiment, and FIG. 2 is a standard heat transfer plate. It is a perspective view which shows the structure of. FIG. 3 is a perspective view showing another configuration example of the standard heat transfer plate. FIG. 4 is a vertical sectional view showing a schematic configuration of a conventional thermal conductivity measuring device. S: Sample, 1 ... Furnace vessel, 5,6,7 ... Insulation, 8 ...
Measuring room, 24,30 ... Standard heat transfer plate, 24a, 30a ... Sheet heat insulating material.

Claims (1)

[Claims] 1. A standard heat transfer system in which a measurement chamber whose circumference is covered with a heat insulating material is provided in a furnace vessel, and a sample whose thermal conductivity is to be measured is placed in the measurement chamber, and which has a known thermal conductivity. The plate is placed in close contact with at least the lower surface of the sample, a steady heat flow from the upper part to the lower part of the measurement chamber is generated to maintain the sample at a desired set temperature, and the heat of the steady heat flow passing through the sample is maintained. By measuring the flow rate and the temperature difference between the upper surface temperature and the lower surface temperature of the sample, the heat configured to measure the thermal conductivity at the set temperature of the sample from the value of the heat flow rate and the temperature difference. In the conductivity measuring device, the standard heat transfer plate is formed by closely winding a thin plate heat insulating material in a spiral shape, and the value of the thermal conductivity in the radial direction is in the thickness direction. That it is smaller than the value of thermal conductivity Thermal conductivity measuring device according to symptoms.