Steady-state heat conductivity coefficient tester capable of meeting size diversity of building material samples

Abstract

The invention discloses a steady-state heat conductivity coefficient tester capable of meeting the size diversity of building material samples. The steady-state heat conductivity coefficient tester comprises a heat conductivity coefficient measuring module and a power unit, the heat conductivity coefficient measuring module structures are symmetrically distributed up and down based on a to-be-measured material test piece; the upper cold plate unit is sequentially provided with a cold plate heater and a cold plate from top to bottom; the lower hot plate unit is sequentially provided with a hot plate heater, a hot plate and a temperature difference sensor from bottom to top; temperature sensors are arranged in the cold plate and the hot plate; the base, the protective shell and the top cover jointly form an external sealing structure; the protective shell comprises a fixed protective shell and a movable protective shell, the movable protective shell and the fixed protective shell can be mutually fixed and detached, and the movable protective shell can move back and forth along the bottom guide rail; the power unit can adjust lifting of the cold plate and movement of the movable protective shell. The test cavity can adapt to measurement test blocks of different sizes, and the test device is simple, easy to operate, high in precision and high in test speed.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal property testing of building materials, and relates to a steady-state thermal conductivity coefficient measuring instrument which can flexibly adjust the size of a measuring cavity and meet the diversity of test sample sizes. Background Art

[0002] The thermal conductivity of building materials is a key indicator of thermal properties. Its value directly impacts the thermal performance of the building envelope, which in turn influences building loads and energy consumption. Therefore, accurately determining the thermal conductivity of building materials is fundamental to building thermal design and energy-saving calculations, and plays a vital role in the sustainable development of the construction industry.

[0003] Steady-state thermal conductivity testing methods offer high accuracy, good repeatability, and a wide range of applications. They are currently widely used in fields such as building materials, industrial materials, electronics, and environmental science. Steady-state thermal conductivity testers primarily include the guarded hot plate method and the heat flow meter method. The thermal conductivity of a material is calculated by applying a steady heat flux to the specimen and measuring the temperature on both sides. In the steady-state thermal conductivity method, the heat flux path through the material must remain consistent to ensure that the measured temperature change is primarily determined by the thermal conductivity of the material itself, unaffected by other factors. Therefore, in this type of steady-state thermal conductivity test, the instrument's measurement points must be completely covered by the test sample, placing strict requirements on the test sample's dimensions. Steady-state thermal conductivity testers typically require a standard specimen with a base size of 300mm x 300mm, with measurement points distributed over a central area of 150mm x 150mm. The minimum base size must be no less than 200mm x 200mm.

[0004] However, in actual application, the test specimens often fail to meet the test size requirements, which can be mainly divided into two situations: (1) For building materials such as steam-pressurized concrete test blocks (length × width × height: 300 × 240 × 200 mm) and sintered porous bricks (290 × 240 × 90 mm), they can be cut to meet the minimum bottom area size requirement of 200 mm × 200 mm. In this case, in order to ensure sufficient contact between the test piece and the hot and cold plates of the measuring instrument and reduce the gap in the measuring cavity, an auxiliary insulation material is often embedded outside the test piece to form a "U"-shaped combined test piece with a bottom area of 300 mm × 300 mm. (2) For building materials such as clay bricks, shale bricks, and coal gangue bricks (length × width × height: 240 × 115 × 90 mm), it is difficult to meet the 200 mm × 200 mm size requirement and the steady-state thermal conductivity coefficient tester cannot be used. In summary, the use of the steady-state thermal conductivity tester is limited due to the strict requirements on the size of the test sample. In addition, for nested composite materials, the production process is complicated and the measurement result error is relatively large. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a steady-state thermal conductivity coefficient measuring instrument that meets the diversity of building material sample sizes. By adjusting the positions of the three movable protective shells of the test instrument, the test cavity of the instrument can be adapted to measurement test blocks of different sizes. The test device is simple, easy to operate, highly accurate, and has a fast test speed; it solves the problem that the thermal conductivity of non-standard-sized building insulation materials cannot be measured or the measurement is inaccurate under actual measurement conditions.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A steady-state thermal conductivity measuring instrument that meets the diversity of building material sample sizes includes a thermal conductivity measurement module and a power unit;

[0008] The thermal conductivity coefficient measurement module structure is based on the symmetrical distribution of the material specimen to be tested, and includes an upper cold plate unit, a lower hot plate unit, a temperature sensor, a base, a protective shell and a top cover;

[0009] The base, the protective shell around the sides and the top cover together form an external sealed structure, in which the upper cold plate unit and the lower hot plate unit are arranged;

[0010] The upper cold plate unit includes a cold plate heater and a plurality of cold plates of different sizes below it; the lower hot plate unit is provided with a hot plate heater, a plurality of hot plates of different sizes and a temperature difference sensor in order from bottom to top; the material specimen to be tested is placed between the cold plate and the temperature difference sensor; the temperature sensor is installed in the cold plate and the hot plate;

[0011] The cold plate corresponds to the hot plate below it one by one; the protective housing includes a fixed protective housing and a movable protective housing, and the movable protective housing can be moved along the bottom guide rail to form closed protective housings of different sizes to correspond to different sizes of test pieces of materials to be tested and cold plates and hot plates;

[0012] The power unit includes a screw telescopic assembly, and multiple screw telescopic assemblies are respectively arranged on the top cover and the base to be connected to multiple cold plates and different mobile protective shells respectively to control the lifting and lowering of each cold plate and the movement of the mobile protective shell.

[0013] The present invention also includes the following technical features:

[0014] Specifically, the screw telescopic assembly includes a screw, a rotating nut sleeved on the screw, a screw base mounted on the end of the screw, a pulley matching the rotating nut and a servo motor connected thereto; a displacement sensor is provided on the screw base.

[0015] Specifically, the fixed protective shell includes a fixed protective shell a and a fixed protective shell b; the fixed protective shell a and the fixed protective shell a are both 90° right-angle bent plates, and the two are arranged diagonally;

[0016] The mobile protective shell includes a mobile protective shell a, a mobile protective shell b and a mobile protective shell c; the mobile protective shell a and the mobile protective shell b have the same width, and the two can be spliced to each other on one side between the fixed protective shell a and the fixed protective shell b; the mobile protective shell c has the sum of its width and can be placed on the other side between the fixed protective shell a and the fixed protective shell b; the mobile protective shell a and the mobile protective shell b are perpendicular to the mobile protective shell c; the fixed protective shell and the mobile protective shell can form a square protective shell.

[0017] Specifically, the outer walls of the mobile protective shell a, mobile protective shell b and mobile protective shell c are all provided with positioning seats and can be respectively connected to the screw bases of the corresponding power units to control the movement of each mobile protective shell through the power unit; a plurality of mounting seats are provided on the base to fix the corresponding power units.

[0018] Specifically, the mobile protective shell is provided with a fixing buckle so that it can be fixed and disassembled with the fixed protective shell; a locking buckle is provided at the lower part of the mobile protective shell, and the mobile protective shell cooperates with the locking hole of the guide rail on the base through the locking buckle so that the mobile protective shell is fixed after moving along the guide rail; the mobile protective shell a, the mobile protective shell b and the mobile protective shell c respectively correspond to a guide rail perpendicular to themselves.

[0019] Specifically, the cold plates include cold plate a, cold plate b, and cold plate c; they are independent of each other and can be fixed or separated; cold plate a, cold plate b, and cold plate c are respectively provided with positioning seats to connect with the screw bases of the corresponding power units, so that the power units can control the lifting of each cold plate; the top cover is provided with multiple mounting seats to fix the corresponding power units;

[0020] The hot plates include a, b and c, which are independent of each other and can be fixed or separated. A hot plate fixing seat is installed under each of the hot plates a, b and c, and the two are connected to the base by screws.

[0021] The upper cold plate unit has the same structure as the lower hot plate unit, and the thermal conductivity coefficient measuring points are distributed on cold plate a, cold plate b and cold plate c, hot plate a, hot plate b and hot plate c, which are flexible and adjustable.

[0022] Specifically, temperature sensors are provided in the middle of the cold plates a, b and c, and the hot plates a, b and c. The temperature sensors use T-type thermocouples, and their output electrical signals are transmitted to the controller through signal acquisition and transmission, and the temperature control of the cold plates and hot plates is realized by the controller.

[0023] Specifically, the top cover is rigidly connected to the fixed protective shell through a fixing screw.

[0024] The measuring method of the steady-state thermal conductivity measuring instrument that meets the diversity of building material sample sizes includes:

[0025] The material specimen to be tested is placed in the test chamber, and the position of the mobile protective shell and the cold plate is adjusted by the power unit. A thermal conductivity coefficient measurement chamber of corresponding size is constructed according to the size of the material specimen to be tested. The mobile protective shell and the cold plate are attached to the four sides and top of the material specimen to be tested, and together with the hot plate at the bottom, form a closed test chamber; when the cold plate contacts the top of the material specimen to be tested, the thickness of the material specimen to be tested can be automatically measured by reading the displacement sensor on the screw base in the power unit; at this time, the upper and lower surface temperatures of the material specimen to be tested are obtained by the temperature sensors in the cold plate and the hot plate, and the thermal conductivity coefficient of the material specimen to be tested is calculated by the Fourier formula.

[0026] Specifically, according to the Fourier one-dimensional steady-state heat conduction model, the heat transfer rate is equal to the heat dissipation rate during steady-state heat transfer. The thermal conductivity of the material is calculated by measuring the temperature difference on both sides of the test specimen and the thickness of the specimen. The calculation formula is as follows:

[0027]

[0028] Where: λ is the thermal conductivity of the material, W / (m·K); d is the thickness of the specimen, m; t1 is the temperature of the hot surface of the specimen, °C; t2 is the temperature of the cold surface of the specimen, °C; F is the area of the hot plate in the instrument, m 2 ; Q is the heat flow through the metering hot plate heater, W; I is the current through the metering hot plate heater, A; R is the resistance of the metering hot plate heater, Ω.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] (1) The thermal conductivity tester of the present invention has a protective shell composed of a fixed protective shell and a movable protective shell. By adjusting the position of the movable protective shell, a thermal conductivity measurement cavity with a bottom surface size of 300mm×300mm, 200mm×200mm, and 100mm×100mm can be constructed, thereby quickly adapting to the measurement of thermal conductivity of specimens with various area sizes.

[0031] (2) The thermal conductivity tester of the present invention consists of three parts, the cold plate and the hot plate, which can be fixed and disassembled to each other. The cold and hot plates with sizes of 300mm×300mm, 200mm×200mm, and 100mm×100mm can be spliced together. The corresponding modules are opened according to the size of the test piece, so that the area of the cold and hot plates is completely fitted with the bottom surface of the test piece, and together with the protective shell, they form a closed test cavity, which effectively reduces external disturbances.

[0032] (3) The thermal conductivity tester of the present invention has various distributions of measuring points, which can be flexibly adjusted according to the size of the tested piece, ensuring that the heat flow can completely pass through the tested piece and the reliability of the measurement results.

[0033] (4) In the thermal conductivity tester of the present invention, the cold plate can be raised and lowered freely, and the displacement sensor provided at the bottom can realize automatic measurement of the thickness of the test piece. The close contact between the test piece and the hot and cold plates can effectively reduce the contact thermal resistance and improve the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the explosion of the measuring instrument device of the present invention.

[0035] Figure 2 It is a schematic diagram of the structure of the movable hot plate and top cover in the measuring instrument device of the present invention.

[0036] Figure 3 It is a schematic diagram of the bottom cold plate and track in the measuring instrument device of the present invention.

[0037] Figure 4 It is a schematic diagram of the distribution of measuring points in the hot and cold plates of the measuring instrument device of the present invention.

[0038] Figure 5 It is a vertical cross-sectional view of the thermal conductivity measurement module in the measuring device of the present invention.

[0039] Figure 6 It is the electrical control block diagram of the measuring instrument device of the present invention.

[0040] The meaning of each number in the figure is:

[0041] 1. Cold plate a, 2. Cold plate b, 3. Cold plate c, 4. Fixed protective housing a, 5. Mobile protective housing a, 6. Mobile protective housing b, 7. Mobile protective housing c, 8. Fixed protective housing b, 9. Base, 10. Positioning seat, 11. Hot plate a, 12. Hot plate b, 13. Hot plate c, 14. Guide rail, 15. Mounting seat, 16. Screw base, 17. Rotating nut, 18. Displacement sensor, 19. Screw, 20. Pulley, 21. Servo motor, 22. Top cover, 23. Fixed screw, 24. Cold plate heater, 25. Temperature difference sensor, 26. Hot plate heater, 27. Temperature sensor, 28. Material specimen to be tested. DETAILED DESCRIPTION

[0042] The present invention provides a steady-state thermal conductivity tester that can meet the diverse sizes of building material samples, and mainly includes a thermal conductivity measurement module and a power unit. The thermal conductivity measurement module structure is based on the symmetrical distribution of the material specimens to be tested. The upper cold plate unit is sequentially provided with a cold plate heater and a cold plate from top to bottom, and the lower hot plate unit is sequentially provided with a hot plate heater, a hot plate, and a temperature difference sensor from bottom to top. The cold and hot plates are both equipped with temperature sensors. The base, protective shell and top cover together form an external sealing structure; the protective shell is composed of a fixed protective shell and a movable protective shell. The movable protective shell is provided with a fixed buckle that can be fixed to and separated from the fixed protective shell. A locking buckle is provided at the bottom, which can move forward and backward along the bottom guide rail. The power unit is composed of a rotary nut, a displacement sensor, a screw, a pulley and a servo motor. The screw base is connected to the positioning seat, which can adjust the lifting and lowering of the cold plate and the movement of the movable protective shell. The present invention fully utilizes the advantages of the steady-state thermal conductivity coefficient test method, which has high accuracy and good repeatability, and avoids the disadvantage of strict requirements on the test piece size. The volume of the measurement cavity can be flexibly and freely adjusted according to the size of the tested piece, and can adapt to various test block sizes. The measurement point arrangement is flexible and adjustable, and the test block height can be automatically measured. The thermal conductivity coefficient measuring instrument has a high reference value for scientific research and production practice, and is also of great significance to the fields of building energy conservation and testing.

[0043] Specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0044] Example 1:

[0045] This embodiment provides a steady-state thermal conductivity tester that meets the requirements of building material sample size diversity. Figures 1 to 5 As shown, it includes a thermal conductivity measurement module and a power unit.

[0046] The thermal conductivity coefficient measurement module structure is symmetrically distributed up and down based on the material specimen 28 to be tested, and includes an upper cold plate unit, a lower hot plate unit, a temperature sensor 27, a base 9, a protective shell and a top cover 22.

[0047] The base 9, the protective shell around the sides and the top cover 22 together form an external sealed structure, in which the upper cold plate unit and the lower hot plate unit are arranged.

[0048] The upper cold plate unit includes a cold plate heater 24 and multiple cold plates of different sizes below it; the lower hot plate unit is equipped with a hot plate heater 26, multiple hot plates of different sizes and a temperature difference sensor 25 from bottom to top; the material specimen 28 to be tested is placed between the cold plate and the temperature difference sensor 25; the temperature sensor 27 is installed in the cold plate and the hot plate.

[0049] The cold plate corresponds to the hot plate below it one by one; the protective shell includes a fixed protective shell and a movable protective shell, and the movable protective shell can be moved along the bottom guide rail to form closed protective shells of different sizes to correspond to different sizes of test material specimens 28 and cold plates and hot plates.

[0050] The power unit includes multiple screw telescoping assemblies, located on the top cover and base. These assemblies connect to the cold plates and various mobile protective housings, controlling the lifting and lowering of the cold plates and the movement of the mobile protective housings. Specifically, there are eight power units, secured to mounting brackets 15, which are rigidly connected to base 9 and top cover 22.

[0051] The screw extension assembly includes a screw 19, a rotating nut 17 that fits over the screw 19, a screw base 16 mounted at the end of the screw 19, a pulley 20 that matches the rotating nut 17, and a servo motor 21 connected to the screw base 16. A displacement sensor 18 is mounted on the screw base 16. The servo motor 21 drives the rotating nut 17 via the pulley 20, controlling the extension and retraction of the screw 19. The screw base 16 is connected to the positioning base 10, thereby controlling the elevation of the cold plate and the movement of the mobile protective housing.

[0052] The fixed protective shell includes a fixed protective shell a4 and a fixed protective shell b8; the fixed protective shell a4 is a 90° right-angle bent plate with a single-side width of 300mm, and the fixed protective shell b8 is a 90° right-angle bent plate with a single-side width of 100mm arranged diagonally to the fixed protective shell a4.

[0053] The mobile protective shell includes a mobile protective shell a5, a mobile protective shell b6 and a mobile protective shell c7; the mobile protective shell a5 and the mobile protective shell b6 have the same width, both 100 mm, and the two can be spliced to each other on one side between the fixed protective shell a4 and the fixed protective shell b8; the width of the mobile protective shell c7 is the sum of the first two, which is 200 mm, and can be placed on the other side between the fixed protective shell a4 and the fixed protective shell b8; the mobile protective shell a5 and the mobile protective shell b6 are perpendicular to the mobile protective shell c7; the fixed protective shell and the mobile protective shell can form a square protective shell.

[0054] Specifically, the mobile protective shell can be moved by the bottom guide rail 14, thereby constructing a closed protective shell with a bottom surface size of 300mm×300mm, 200mm×200mm, and 100mm×100mm.

[0055] The outer walls of the mobile protective shell a5, the mobile protective shell b6 and the mobile protective shell c7 are all provided with positioning seats 10 and can be respectively connected to the screw base 16 of the corresponding power unit to control the movement of each mobile protective shell through the power unit; a plurality of mounting seats 15 are provided on the base 9 to fix the corresponding power unit.

[0056] The mobile protective shell is provided with a fixing buckle so that it can be fixed and disassembled with the fixed protective shell; a locking buckle is provided at the lower part of the mobile protective shell, and the mobile protective shell cooperates with the locking hole of the guide rail 14 on the base 9 through the locking buckle so that the mobile protective shell can be moved along the guide rail 14 and then fixed; the mobile protective shell a5, the mobile protective shell b6 and the mobile protective shell c7 respectively correspond to a guide rail perpendicular to themselves; the guide rail 14 is rigidly connected to the base 9.

[0057] The cold plates include cold plate a1, cold plate b2 and cold plate c3; they are independent of each other and can be fixed or disassembled, and can be composed of cold plates with sizes of 300mm×300mm, 200mm×200mm, and 100mm×100mm as required; cold plates a1, b2 and c3 are respectively provided with positioning seats 10 to be connected to the screw bases 16 of the corresponding power units to control the lifting of each cold plate through the power units; multiple mounting seats 15 are provided on the top cover 22 to fix the corresponding power units.

[0058] The hot plates include a11, b12, and c13. They are independent of each other and can be fixed or separated. They can be combined into cold plates with sizes of 300mm×300mm, 200mm×200mm, and 100mm×100mm as required. Hot plate fixing seats are installed under the hot plates a11, b12, and c13, and the two are connected to the base 9 by screws.

[0059] The upper cold plate unit has the same structure as the lower hot plate unit, and the thermal conductivity coefficient measuring points are distributed on cold plates a1, b2 and c3, and hot plates a11, b12 and c13, and are flexible and adjustable. When the size is 100mm×100mm, measuring points ① to ④ are opened, when the size is 200mm×200mm, measuring points ④ to ⑦ are opened, and when the size is 300mm×300mm, measuring points ⑦ to ⑩ are opened. The heat sources all use sheet electric heaters.

[0060] Temperature sensors 27 are installed between cold plates a1, b2, and c3, and hot plates a11, b12, and c13. These sensors use T-type thermocouples, and their output signals are transmitted to a controller through signal acquisition and transmission. The controller controls the temperatures of the cold and hot plates. The controller includes a signal acquisition module, a temperature control module, a motor control module, and a communication module. Figure 6 This is the electrical control block diagram of the measuring instrument device of the present invention,

[0061] The top cover 22 is rigidly connected to the fixed protective housing a4 and the fixed protective housing b8 via fixing screws 23 , and there are six fixing screws 23 in total.

[0062] The present invention also provides a method for measuring the steady-state thermal conductivity coefficient of a building material sample that meets the diversity of sample sizes. The method includes: placing a test piece 28 of the material to be tested into a test chamber, controlling the lifting and lowering of a screw 19 by a power unit servo motor 21 and a rotary nut 17, and connecting a screw base 16 to a positioning seat 10 installed on a cold plate and a mobile protective shell, thereby being able to adjust the position of the mobile protective shell and the cold plate, and constructing corresponding bottom surface sizes of 300mm×300mm, 200mm×200mm, and 1 according to the size of the test piece 28 of the material to be tested. 00mm×100mm thermal conductivity measurement chamber, the mobile protective shell and the cold plate are attached to the four sides and top of the material specimen 28 to be tested, and together with the hot plate at the bottom form a closed test chamber; when the cold plate contacts the top of the material specimen 28 to be tested, the thickness of the material specimen 28 to be tested can be automatically measured by the reading of the displacement sensor 18 on the screw base 16 in the power unit; at this time, the upper and lower surface temperatures of the material specimen 28 to be tested are obtained by the temperature sensors 27 in the cold plate and the hot plate, and the thermal conductivity of the material specimen 28 to be tested is calculated by the Fourier formula.

[0063] The present invention adopts the steady-state guarded hot plate method. According to the Fourier one-dimensional steady-state thermal conductivity model, the heat transfer rate in the steady-state heat transfer process is equal to the heat dissipation rate. The thermal conductivity of the material is calculated by measuring the temperature difference between the two sides of the test specimen and the thickness of the specimen. The calculation formula is as follows:

[0064]

[0065] Where: λ is the thermal conductivity of the material, W / (m·K); d is the thickness of the specimen, m; t1 is the temperature of the hot surface of the specimen, °C; t2 is the temperature of the cold surface of the specimen, °C; F is the area of the hot plate in the instrument, m 2 ; Q is the heat flow through the metering hot plate heater, W; I is the current through the metering hot plate heater, A; R is the resistance of the metering hot plate heater, Ω.

[0066] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0067] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. To avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0068] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A steady-state thermal conductivity tester that meets the diversity of building material sample sizes, characterized in that: Includes thermal conductivity measurement module and power unit; The thermal conductivity coefficient measurement module structure is symmetrically distributed up and down based on the material specimen (28) to be tested, and includes an upper cold plate unit, a lower hot plate unit, a temperature sensor (27), a base (9), a protective shell and a top cover (22); The base (9), the protective shell around the side, and the top cover (22) together form an external sealed structure, in which the upper cold plate unit and the lower hot plate unit are arranged; The upper cold plate unit includes a cold plate heater (24) and a plurality of cold plates of different sizes below it; the lower hot plate unit is provided with a hot plate heater (26), a plurality of hot plates of different sizes and a temperature difference sensor (25) in order from bottom to top; the material specimen (28) to be tested is placed between the cold plate and the temperature difference sensor (25); the temperature sensor (27) is installed in the cold plate and the hot plate; The cold plate corresponds to the hot plate below it one by one; the protective shell includes a fixed protective shell and a movable protective shell, and the movable protective shell can be moved along the bottom guide rail to form closed protective shells of different sizes to correspond to different sizes of test material specimens (28) to be tested and the cold plate and hot plate; The power unit includes a screw telescopic assembly, and multiple screw telescopic assemblies are respectively arranged on the top cover and the base to be connected to multiple cold plates and different mobile protective shells respectively to control the lifting and lowering of each cold plate and the movement of the mobile protective shell.

2. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes according to claim 1, characterized in that: The screw telescopic assembly comprises a screw (19), a rotary nut (17) sleeved on the screw (19), a screw base (16) mounted on the end of the screw (19), a pulley (20) matched with the rotary nut (17) and a servo motor (21) connected thereto; a displacement sensor (18) is provided on the screw base (16).

3. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes as claimed in claim 2, characterized in that: The fixed protective shell includes a fixed protective shell a (4) and a fixed protective shell b (8); the fixed protective shell a (4) and the fixed protective shell a (8) are both 90° right-angle bent plates, and the two are arranged diagonally; The mobile protective shell includes a mobile protective shell a (5), a mobile protective shell b (6) and a mobile protective shell c (7); the mobile protective shell a (5) and the mobile protective shell b (6) have the same width, and the two can be spliced to one side between the fixed protective shell a (4) and the fixed protective shell b (8); the mobile protective shell c (7) has a width equal to the sum of the widths of the former two, and can be placed on the other side between the fixed protective shell a (4) and the fixed protective shell b (8); the mobile protective shell a (5) and the mobile protective shell b (6) are perpendicular to the mobile protective shell c (7); the fixed protective shell and the mobile protective shell can form a square protective shell.

4. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes as claimed in claim 3, characterized in that: The outer walls of the mobile protective housing a (5), the mobile protective housing b (6) and the mobile protective housing c (7) are all provided with positioning seats (10) and can be respectively connected to the screw bases (16) of the corresponding power units so as to control the movement of each mobile protective housing through the power units; the base (9) is provided with a plurality of mounting seats (15) for fixing the corresponding power units.

5. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes as claimed in claim 3, characterized in that: The mobile protective shell is provided with a fixing buckle so as to be fixed to and detached from the fixed protective shell; a locking buckle is provided at the lower part of the mobile protective shell, and the mobile protective shell cooperates with the locking hole of the guide rail (14) on the base (9) through the locking buckle so that the mobile protective shell moves along the guide rail (14) and is fixed; the mobile protective shell a (5), the mobile protective shell b (6) and the mobile protective shell c (7) respectively correspond to a guide rail perpendicular to themselves.

6. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes as claimed in claim 2, characterized in that: The cold plates include a cold plate a (1), a cold plate b (2) and a cold plate c (3); they are independent of each other and can be fixed or separated; the cold plates a (1), the cold plates b (2) and the cold plates c (3) are respectively provided with positioning seats (10) to be connected with the screw bases (16) of the corresponding power units so as to control the lifting of each cold plate through the power units; the top cover (22) is provided with a plurality of mounting seats (15) to fix the corresponding power units; The hot plates include a hot plate a (11), a hot plate b (12) and a hot plate c (13); they are independent of each other and can be fixed or separated; a hot plate fixing seat is installed below the hot plate a (11), the hot plate b (12) and the hot plate c (13), and the two are connected to the base (9) by screws; The upper cold plate unit is constructed in the same manner as the lower hot plate unit. The thermal conductivity measurement points are distributed on the cold plate a (1), cold plate b (2), cold plate c (3), hot plate a (11), hot plate b (12), and hot plate c (13), and are flexible and adjustable.

7. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes according to claim 6, characterized in that: Temperature sensors (27) are provided in the middle of the cold plate a (1), the cold plate b (2), the cold plate c (3), the hot plate a (11), the hot plate b (12), and the hot plate c (13). The temperature sensors (27) are T-type thermocouples, and their output electrical signals are transmitted to the controller through signal collection and transmission, so that the temperature of the cold plate and the hot plate is controlled by the controller.

8. The steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes according to claim 1, characterized in that: The top cover (22) is rigidly connected to the fixed protective shell via a fixing screw (23).

9. The measuring method of the steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes according to any one of claims 2 to 8, characterized in that: include: The material specimen to be tested is placed in the test chamber, and the position of the mobile protective shell and the cold plate is adjusted by the power unit. A thermal conductivity coefficient measurement chamber of corresponding size is constructed according to the size of the material specimen to be tested. The mobile protective shell and the cold plate are attached to the four sides and top of the material specimen to be tested, and together with the hot plate at the bottom, form a closed test chamber; when the cold plate contacts the top of the material specimen to be tested, the thickness of the material specimen to be tested can be automatically measured by reading the displacement sensor on the screw base in the power unit; at this time, the upper and lower surface temperatures of the material specimen to be tested are obtained by the temperature sensors in the cold plate and the hot plate, and the thermal conductivity coefficient of the material specimen to be tested is calculated by the Fourier formula.

10. The measuring method of the steady-state thermal conductivity measuring instrument that satisfies the diversity of building material sample sizes according to claim 9, characterized in that: According to Fourier's one-dimensional steady-state heat conduction model, the heat transfer rate is equal to the heat dissipation rate during steady-state heat transfer. The thermal conductivity of the material is calculated by measuring the temperature difference on both sides of the test specimen and the thickness of the specimen. The calculation formula is as follows: Where: λ is the thermal conductivity of the material, W / (m·K); d is the thickness of the specimen, m; t1 is the temperature of the hot surface of the specimen, °C; t2 is the temperature of the cold surface of the specimen, °C; F is the area of the hot plate in the instrument, m 2 ; Q is the heat flow through the metering hot plate heater, W; I is the current through the metering hot plate heater, A; R is the resistance of the metering hot plate heater, Ω.

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