CN103293182A - Automatic heat conductivity coefficient tester through protective heat flow meter method and detection method - Google Patents

Abstract

The invention provides an automatic measuring instrument for thermal conductivity by the protective heat flow meter method. The movement of the piston rod in the cylinder of the pneumatic device of the measuring instrument realizes the lifting of the hot plate and the thermal protection furnace of the test stack, and is located outside the cold plate and the cold plate fixing seat. The support sleeve is installed, and the heat flow sensor is installed on the lower end surface of the upper support sleeve. The electrical signal obtained by the heat flow sensor is transmitted to the control unit for analysis and control. The control unit is connected with the pneumatic device to control the movement of the piston rod of the cylinder of the pneumatic device. . It also provides a detection method for the thermal conductivity automatic measuring instrument of the protective heat flow meter method. The effect of the present invention is to protect the heat flow sensor from pressure loss, realize automatic lifting and lowering of the test stack, avoid cumbersome manual operations, and improve the measurement accuracy of thermal conductivity of thermal insulation and thermal insulation materials and the repeatability of instrument measurement. It is suitable for production enterprises of heat insulation and heat preservation materials, colleges and universities and research institutes and other units.

Description

Protective heat flow meter method thermal conductivity automatic measuring instrument and detection method

technical field

The invention relates to a protective heat flow meter method thermal conductivity measuring instrument, in particular to an automatic protective heat flow meter method thermal conductivity measuring instrument and a detection method.

Background technique

Thermal conductivity is an important parameter used to measure the thermal conductivity and thermal insulation performance of thermal insulation materials and thermal insulation materials. It is a key indicator to measure and identify the heat dissipation and thermal insulation capabilities of materials. Thermal insulation materials and thermal insulation materials are used in various industries, such as construction, metallurgy, military industry, aerospace, etc., and their performance is determined by the thermal conductivity of the material itself. Therefore, as an important parameter to measure the performance of thermal insulation materials and thermal insulation materials - the accurate measurement of thermal conductivity has important practical significance for modern production.

The thermal conductivity measurement methods are mainly divided into transient method and steady state method. As a method in the steady state method, the protective heat flow meter method has a large measurement range and can measure the characteristics of thin film materials and small sample materials. The measurement of the coefficient material has very important reference value for scientific research and production practice.

At present, the leading thermal conductivity meters based on the heat flow meter method are mainly foreign products. At the same time, as far as the development status of domestic related products is concerned, the technology is far from mature and the reliability is poor. The heat flow sensor cannot bear a lot of pressure, and at this stage, the heat flow sensor is adhered to the cold plate with thermal silica gel. If the adhesion is not tight, it will be taken away from the original position by the hot plate or the test piece. Due to the specific heat of the heat flow sensor When the size of the plate or cold plate is small, when there is a gap in thermal conductivity between the heat flow sensor and the surrounding filling material, the heat flow line will shift during the downward transfer of heat flow, resulting in the generation of contact thermal resistance, and the heat flow measured by the heat flow sensor The density will deviate from the theoretical average heat flux density, and at this stage, the thermal protection furnace and the hot plate need to be lifted manually, which is cumbersome to operate and has a low degree of equipment automation. Therefore, it is of great value to design a high-precision protective heat flow meter method thermal conductivity automatic measuring instrument with the function of protective heat flow sensor.

Contents of the invention

Aiming at the structural deficiencies of the prior art, the purpose of the present invention is to provide an automatic measuring instrument and detection method for thermal conductivity of the protective heat flow meter method, so as to achieve the purpose of realizing the reasonable installation of the heat flow sensor and protecting the heat flow sensor, preventing it from being pressured or damaged. Take it away from the original position; and use the calibration method to reduce the thermal conductivity measurement error caused by the contact thermal resistance and heat flow line offset, improve the thermal conductivity measurement accuracy; at the same time further improve the automation of the tester, and realize the thermal plate of the test stack And the automatic lifting of the thermal protection furnace, reducing manual operation, improving the measurement accuracy of the thermal conductivity of thermal insulation and insulation materials and the repeatability of instrument measurement.

In order to achieve the above object, the technical solution adopted by the present invention is to provide a protective heat flow meter method thermal conductivity automatic measuring instrument, wherein: the measuring instrument includes a control unit and an instrument unit, and the instrument unit includes a bracket structure, and the bracket structure is installed There is a test stack. The test stack includes a hot plate, a cold plate, and a thermal protection furnace. The cold plate is fixed on the cold plate fixing seat, the hot plate is fixed on the hot plate fixing seat, and the thermal protection furnace is surrounded by the hot plate and the cold plate. It is characterized in that a pneumatic device is installed above the support structure, the cylinder and piston rod of the pneumatic device are connected with the upper end of the connecting rod in sequence, and the lower end of the connecting rod is connected with the hot plate fixing seat of the test stack and the thermal protection furnace Connected, a heat flow sensor is provided on the lower end surface of the support sleeve outside the cold plate of the test stack, and heat-conducting materials are filled around the heat flow sensor; the electrical signal obtained by the heat flow sensor is transmitted to the control unit for analysis and control. The control unit is connected with the pneumatic device to control the movement of the piston rod of the cylinder of the pneumatic device.

At the same time, it also provides a detection method for protecting the thermal conductivity automatic measuring instrument by heat flow meter method.

The effect of the present invention is that the measuring instrument protects the heat flow sensor, prevents the heat flow sensor from being pressured or taken away from the original position by the hot plate or the test piece, reduces the thermal conductivity measurement error caused by the installation of the heat flow sensor, and improves the thermal conductivity measurement accuracy. At the same time, it realizes the automatic operation of the measuring instrument, avoids the cumbersome manual operation, realizes automatic operation and measurement, improves the repeatability and automation of the instrument, and has a simple structure and easy operation. Even personnel without operating experience can quickly master the operation method. Conducive to the popularization of measuring instruments.

Description of drawings

Fig. 1 is the schematic diagram of measuring instrument mechanical structure of the present invention;

Fig. 2 is a schematic diagram of the detection state of the test piece by the measuring instrument mechanical structure of the present invention;

Fig. 3 is a schematic side view of the installation of the heat flow sensor of the present invention;

Fig. 4 is the pneumatic control block diagram of measuring instrument of the present invention;

Fig. 5 is a block diagram of the electrical control of the measuring instrument of the present invention.

In the picture:

1. Cylinder 2. Cylinder support frame 3. Support frame 4. Heat protection furnace 5. Heat plate fixing seat 6. Heat flow sensor 7. Cold plate 8. Cold plate fixing seat 9. Heat protection furnace pad 10. Piston rod 11. Nut 12. Connecting rod 13, universal joint 14, hot plate 15, test piece 16, upper support sleeve 17, lower support sleeve 18, base 19, motor 20, air pump 21, high pressure cylinder 22, reversing valve 23, Regulating valve 24, filling material

Detailed ways

The protective heat flow meter method thermal conductivity automatic measuring instrument and detection method of the present invention will be further described in conjunction with the accompanying drawings.

The protection heat flow meter method thermal conductivity automatic measuring instrument of the present invention adopts the protection heat flow meter method in the one-dimensional steady-state method, according to the Fourier one-dimensional steady-state heat conduction model, by measuring the heat flux density, the temperature difference between the two sides of the sample and the test Calculate the thermal conductivity of the material using the sample thickness. The basic calculation method is as follows:

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; \&Delta;T</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}$

$\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}$

In the formula, R is the thermal resistance value of the test specimen, ΔT is the temperature difference between the upper and lower surfaces of the test specimen, q is the heat flux density, h is the thickness of the test specimen, and λ is the thermal conductivity value of the test specimen.

The protective heat flow meter method thermal conductivity automatic measuring instrument of the present invention has a structure as shown in Figures 1 and 2. The measuring instrument includes an instrument unit and a control unit, wherein the instrument unit consists of a test stack, a pneumatic device, an automatic temperature control device, and a heat flow control unit. It is composed of sensors and bracket structures, and the control unit is composed of an interconnected upper computer, motor, communication module and control module. A test stack is installed inside the support structure 3, and the cylinder 1 of the pneumatic device is installed above the support structure 3. The cylinder 1 of the pneumatic device, the piston rod 10 and the upper end of the connecting rod 12 are connected in sequence, and the lower end of the connecting rod 12 is connected to the test stack. The hot plate fixing seat 5 is connected, and the thermal protection furnace 4 is connected with the connecting rod 12 in a gap fit. The movement of the piston rod 10 drives the automatic lifting of the hot plate 14 of the test stack and the thermal protection furnace 4. The heat flow sensor 6 is installed on the test stack. The lower end surface of the upper support sleeve 16 outside the cold plate 7, the support sleeve 16 resists the downward pressure and protects the heat flow sensor 6, and is filled with heat-conducting material around the heat flow sensor 6; the electrical signal obtained by the heat flow sensor 6 is transmitted to the control unit analysis on the processing. The hot plate 14, the cold plate 7, and the thermal protection furnace 4 of the test stack all have installation holes, the sensors of the automatic temperature control device are set in the installation holes of the test stack, and the electrical signals of the sensors of the automatic temperature control device are transmitted to the control unit After analyzing and controlling the temperature of the test stack by the control unit, the control unit is connected with the instrument unit of the measuring instrument through the communication module, and the control unit is connected with the pneumatic device to control the movement of the cylinder piston rod 10 of the pneumatic device.

The pneumatic device includes a cylinder 1, a reversing valve 22, a regulating valve 23 and a high-pressure cylinder 21, etc., wherein the cylinder 1 is fixedly installed above the support structure 3 through the cylinder support frame 2, and is connected with the regulating valve 23, The reversing valve 22 is connected with the high-pressure cylinder 21 to form a gas circuit. The intake pipe of the reversing valve 22 is connected with the high-pressure cylinder. The reversing valve 22 is connected with the control unit.

The test stack includes a hot plate 14 , a cold plate 7 , and a thermal protection furnace 4 . The hot plate 14 and the cold plate 7 are generally cylindrical, and their dimensions are generally slightly larger than the external dimensions of the heat flow sensor 6 . Wherein the cold plate 7 is fixed on the cold plate fixing seat 8, the hot plate 14 is fixed on the hot plate fixing seat 5, the hot plate fixing seat and the cold plate fixing seat play the role of fixing and supporting the hot plate and the cold plate. The lower end of the rod 12 is connected with the hot plate fixing seat 5 through the universal joint 13, the upper end of the connecting rod 12 is rigidly connected with the piston rod 10 of the cylinder through the nut 11, and the connecting rod 12 is connected with the heat protection furnace 4 with gap fit, and the lower end of the connecting rod 12 has a step , the outer diameter of the step is greater than the inner diameter of the upper port of the heat protection furnace 4, and the upper end surface of the heat protection furnace is located above the step. The thermal protection furnace 4 provides a test environment with a constant temperature for the test environment, which greatly improves the accuracy and repeatability of instrument measurement.

Described support sleeve comprises upper support sleeve 16 and lower support sleeve 17, and lower support sleeve is installed on the periphery of cold plate 7 and cold plate holder 8, and upper support sleeve 16 is installed on the top of lower support sleeve 17 and cold plate 7, and cold plate The fixed seat 8 and the lower support sleeve 17 are fixed on the base 18, and an insulating layer is installed between the upper and lower support sleeves. The upper support sleeve 16 is made of a material with a small thermal conductivity. The lower end surface of the upper support sleeve 16.

In the detection method of the protection heat flow meter method thermal conductivity automatic measuring instrument of the present invention, during the detection operation, the heat flow sensor 6 is in close contact with the upper support sleeve 16 and the cold plate 7, and the heat flow sensor 6 is filled with thermal conductivity and heat flow The thermally conductive material 24 close to the sensor 6 , such as a thermally conductive silicone sheet, has the same thickness as the heat flow sensor 6 . q is the average heat flux passed from the bottom of the hot plate to the cold plate, and _q1 is the heat flux measured by the heat flow sensor 6, and the relationship between the two is:

q=q ₁ (A ₁ +A ₂ λ ₂ /λ ₁ )/A

Wherein: λ ₁ is the thermal conductivity coefficient of the heat flow sensor 6, λ ₂ is the thermal conductivity coefficient of the filling material 24, A ₁ is the area of the heat flow sensor 6, A ₂ is the area of the filling material 24, and A is the total area of the cold plate 7, so that a =(A ₁ +A ₂ λ ₂ /λ ₁ )/A, when the heat flow sensor 6 and the surrounding filling material 24 are determined, the value of a is constant. A is called a compensation constant. When the temperature around the test piece 15 changes, the heat flux q1 measured by the heat flux sensor 6 changes constantly. The formula q= _q1a can be used to obtain the compensated heat flux, and then _the material’s Thermal Conductivity. The formula for calculating the thermal conductivity after calibration is:

λ=q ₁ ah/ΔT

During measurement, the test specimen 15 is placed above the upper support sleeve 16 . The upper support sleeve 16 and the lower support sleeve 17 play the role of protecting the heat flow sensor 6. On the one hand, the upper support sleeve 16 plays a supporting role to prevent the heat flow sensor 6 from being damaged by pressure. 6 touches and is taken away from its original position.

In the protective heat flow method thermal conductivity measuring instrument, the lifting of the thermal protection furnace 4 and the hot plate 14 of the test stack are all realized by the movement of the cylinder piston rod 10 . The hot plate 14 is fixed on the hot plate fixing seat 5, and the hot plate fixing seat 5 is connected with the connecting rod 12 through the universal joint 13, and the connecting rod 12 is connected with the piston rod 10 through the nut 11. When the piston rod 10 moves, it drives the connecting rod 12 and the heating plate 14 to lift up and down. When the step at the lower end of the connecting rod 12 meets the heat protection furnace 4, because the outer diameter of the step is greater than the inner diameter of the upper port of the heat protection furnace 4, the connecting rod 12 will drive the thermal protection furnace 4 to lift, thereby realizing the lifting control of the hot plate 14 and the thermal protection furnace 4 of the test stack.

The control unit is connected to the instrument unit of the measuring instrument through communication equipment, and the sensor electric signal of the automatic temperature control device is transmitted to the control unit, and the temperature of the stack is measured and controlled by the control unit, and the electric signal obtained by the heat flow sensor is transmitted to the control unit. The processing is carried out on the control unit, and the control unit is connected with the pneumatic device at the same time, and controls the movement of the cylinder piston rod of the cylinder of the pneumatic device and the work of the reversing valve by controlling the electric motor. The control unit is closely combined with the mechanical structure, which smoothly realizes the intelligent measurement process of the instrument.

Application Example: Measuring the thermal conductivity of a certain specimen sample

1. Make test pieces:

The size of the test piece 15 is limited by the standard, and the protective heat flow method thermal conductivity tester can test the size under any standard conditions.

2. Turn on the power and install the sample:

Turn on the power supply, turn on the motor 19, and make the piston rod 10 drive the hot plate 14 to rise. When rising to a certain position, it will run into the heat protection furnace 4, and then drive the heat protection furnace 4 to rise. When it rises to the top, the test piece 15 is placed, and the piston rod 10 moves downward. When the heat protection furnace 4 moves down to the bottom and touches the heat protection furnace pad 9, the heat protection furnace 4 stops moving, and the piston rod 10 drives The hot plate 14 continues to move downwards, and after pressing the test piece 15, the piston rod 10 stops moving.

3. Start the test program, set the temperature of the hot plate 14, the cold plate 7 and the thermal protection furnace 4, so that the ambient temperature meets the measurement requirements.

4. The computer monitors the temperature of the hot plate 14, the cold plate 7, the thermal protection furnace 4, and the output value of the heat flow sensor 6 in real time, and automatically saves them.

5 Analyze the data and print the results, calculate the thermal conductivity of the tested piece according to the calculation formula for thermal conductivity after calibration, complete the measurement of the thermal conductivity of the material, close the program, start the cylinder 1, and take out the test piece 15.

The protective heat flow meter method thermal conductivity automatic measuring instrument realizes the protection and automatic operation functions of the heat flow sensor, improves the repeatability of the instrument, and simplifies the operability of the instrument.

Claims (6)

1. A protective heat flow meter method thermal conductivity automatic measuring instrument, this measuring instrument comprises a control unit and an instrument unit, and the instrument unit includes a support structure, and a test stack is installed in the support structure, and the test stack includes a hot plate, a cold Plate and heat protection furnace, wherein the cold plate is fixed on the cold plate fixing seat, the hot plate is fixed on the hot plate fixing seat, and the heat protection furnace is set around the outer periphery of the hot plate and the cold plate; its feature is: in the support structure A pneumatic device is installed above the cylinder, the cylinder and piston rod of the pneumatic device are connected with the upper end of the connecting rod in sequence, the lower end of the connecting rod is connected with the hot plate fixing seat of the test stack body and the heat protection furnace, and the support sleeve outside the cold plate of the test stack body A heat flow sensor is provided on the lower end surface of the heat flow sensor, and heat-conducting materials are filled around the heat flow sensor; the electrical signal obtained by the heat flow sensor is transmitted to the control unit for analysis and control, and the control unit is connected with the pneumatic device to control the cylinder of the pneumatic device. Piston rod movement is controlled. 2. The protection heat flow meter method thermal conductivity automatic measuring instrument according to claim 1 is characterized in that: the pneumatic device also includes a reversing valve, a regulating valve and a high-pressure cylinder, and the cylinder of the pneumatic device passes through the airtight air The gas circuit is connected with the regulating valve, the reversing valve and the high-pressure cylinder in sequence, the intake pipe of the reversing valve is connected with the high-pressure cylinder, and the reversing valve is connected with the control unit. 3. The protection heat flow meter method thermal conductivity automatic measuring instrument according to claim 1, characterized in that: the upper end of the connecting rod of the pneumatic device is rigidly connected with the piston rod of the cylinder through a nut, and the lower end of the connecting rod is connected to the heat sink through a universal joint. The plate fixing seat is connected, and the connecting rod is connected with the thermal protection furnace with gap fit. There is a step near the lower end of the connecting rod. The diameter of the step is larger than the inner diameter of the upper port of the thermal protection furnace. 4. The protection heat flow meter method thermal conductivity automatic measuring instrument according to claim 1, characterized in that: the support sleeve outside the cold plate comprises an upper support sleeve and a lower support sleeve, and the support sleeve is installed on the cold plate and the cold plate is fixed The outer periphery of the seat, the cold plate fixing seat and the lower support sleeve are fixed on the base, the upper support sleeve is located on the cold plate and the upper support sleeve, and a heat insulation layer is installed between the upper support sleeve and the lower support sleeve, and the heat flow sensor passes through the heat-conducting silica gel Paste on the lower end face of the upper support sleeve. 5. The protective heat flow meter method thermal conductivity automatic measuring instrument according to claim 1, characterized in that: the control unit includes an interconnected upper computer, a motor, a communication module, and a control module, and the control unit communicates with the measurement unit through the communication module The automatic temperature control device in the instrument unit of the instrument is connected to the heat flow sensor, and the heat flux density electrical signal collected by the heat flow sensor and transmitted from the hot plate to the cold plate is transmitted to the control unit for analysis and processing. Drive the pneumatic pump to work, control the movement of the cylinder piston rod of the pneumatic device and the work of the reversing valve through the control module. 6. the detection method of protective calorimeter method thermal conductivity automatic measuring instrument according to claim 1, when the method detects operation, the heat flow sensor of described protective calorimeter method thermal conductivity automatic measuring instrument and upper supporting sleeve and cooling The plates are in close contact, and the thickness of the heat-conducting material filled around the heat flow sensor is the same as the thickness of the heat flow sensor. When testing the specimen, the heat flux q ₁ measured by the heat flow sensor, the thickness h of the test specimen and the temperature of the upper and lower sides of the test specimen are known. The difference ΔT, the calculation formula of thermal conductivity after calibration is: λ=qh/ΔT=q ₁ ah/ΔT In the formula: λ is the thermal conductivity of the test piece, q is the average heat flux from the bottom of the hot plate to the cold plate, q ₁ is the heat flux measured by the actual heat flow sensor, then the relationship between q and q ₁ is: q=q ₁ a, compensation constant a=(A ₁ +A ₂ λ ₂ /λ ₁ )/A, so: q=q ₁ (A ₁ +A ₂ λ ₂ /λ ₁ )/A Where λ ₁ is the thermal conductivity of the heat flow sensor, λ ₂ is the thermal conductivity of the filled thermal conductive material, A ₁ is the area of the heat flow sensor, A ₂ is the area filled with the thermal conductive material, and A is the total area of the cold plate.

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