Portable ice heat conductivity coefficient tester

Abstract

The utility model discloses a portable ice heat conductivity coefficient tester, and relates to the technical field of heat conduction and heat insulation performance of characterization materials. Comprising an aluminum alloy support, a silica gel pad is fixed to a cross beam at the top end of the aluminum alloy support, a heat insulation supporting column is fixedly connected to the bottom of the silica gel pad, a copper disc is fixedly connected to the bottom end of the heat insulation supporting column, and a base is arranged at the bottom of the aluminum alloy support; a copper disc is also fixed to the top of the heat insulation cover, and an electric push rod is further installed on one side of the aluminum alloy support. Through the arrangement of the heat conductivity coefficient detection platform and the like, on the basis of ingenious mechanical design, the lifting platform and the push rod are matched with each other, so that semi-automation of operation is realized, the operation is convenient, the accuracy of a measurement result is high, the cost is lower, the experiment repeatability is high, the demonstration effect is good, and the application is wide.

Description

Technical Field

[0001] The utility model relates to the technical field of characterizing thermal conductivity and thermal insulation performance of materials, in particular to a portable ice thermal conductivity tester. Background Art

[0002] As a characterization of the thermal physical properties of materials, the accurate measurement of thermal conductivity is of great significance for the research and development and production of various insulation materials. Thermal conductivity meters for measuring thermal conductivity are widely used in various industries. According to the current literature survey, there are relatively few research contents on ice thermal conductivity meters on the market, and there is no systematic instrument structure design plan. Therefore, we believe that the research on ice thermal conductivity meters has great innovation and practicality.

[0003] Combined with the above analysis, we are committed to developing a new ice sample thermal conductivity measuring instrument, including the measuring instrument's mechanical structure system, automatic control system, data acquisition and analysis system, in order to achieve scientific measurement of ice thermal conductivity. As an important thermophysical parameter, ice thermal conductivity is one of the important indicators for measuring the thermal properties of ice, and directly reflects the ability of ice to conduct heat. In view of the current lack of a complete ice sample thermal conductivity measuring instrument on the market, we designed a more systematic experimental device based on the experimental principle of the steady-state method, and optimized and improved the measuring device and measuring method. This experimental device is applied to the field of food processing. By measuring the thermal conductivity of ice samples during the refrigeration and preservation of fruits and vegetables, a classified storage and processing technology plan is formulated according to its characteristics. This will provide reliable theoretical and data references for the storage and processing industry of fresh food.

[0004] Applying this experimental device to the measurement of the thermal conductivity of sea ice will assist in on-site observations of scientific expeditions and provide specific data references for global climate change. Since thermal conductivity is a key thermophysical parameter that characterizes the thermal conductivity and insulation properties of materials, it is widely used in food processing, building energy conservation, electronics industry, aerospace and other fields. Utility Model Content

[0005] The purpose of the utility model is to provide a portable ice thermal conductivity tester to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned purpose, the utility model provides the following technical solutions: a portable ice thermal conductivity tester, comprising a thermal conductivity test platform and a temperature control system, wherein the thermal conductivity test platform comprises an aluminum alloy bracket;

[0007] A silicone pad is fixed to the crossbeam at the top of the aluminum alloy bracket, a heat-insulating support is fixedly connected to the bottom of the silicone pad, and a copper plate is fixedly connected to the bottom of the heat-insulating support;

[0008] A base is provided at the bottom of the aluminum alloy bracket, a lifting platform is installed on the top of the base, a heat insulation cover is fixedly connected to the top of the lifting platform, a heating plate is provided above the heat insulation cover, a copper plate is also fixed on the top of the heating plate, and an electric push rod is also installed on one side of the aluminum alloy bracket.

[0009] Preferably, the thermal insulation cover and the copper plate are on the same axis, a gap is provided between the thermal insulation cover and the copper plate, and the telescopic end of the electric push rod is between the thermal insulation cover and the copper plate.

[0010] Preferably, a camera for recording the detection process is installed on one side of the top of the aluminum alloy bracket.

[0011] Preferably, the temperature control system comprises: a transformer, a relay, a temperature controller and a pt temperature sensor;

[0012] The pt temperature sensor is arranged at the copper plate to detect the temperature of the copper plate. The pt temperature sensor is connected to the temperature controller. The temperature controller, the heating plate and the transformer are all electrically connected to the relay.

[0013] Preferably, the temperature control system further comprises a data acquisition module, a data conversion module and a PC terminal, the pt temperature sensor is also connected to the data acquisition module, and the data acquisition module is connected to the data conversion module and transmitted to the PC terminal.

[0014] Compared with the prior art, the beneficial effects of the utility model are:

[0015] The portable ice thermal conductivity tester is equipped with a thermal conductivity test table, etc., and based on an ingenious mechanical design, the lifting table and the push rod cooperate with each other to achieve semi-automatic operation, easy operation, high measurement accuracy, low cost, high experimental repeatability, good demonstration effect, and wide application.

[0016] At the same time, this experimental device sets a silicone material above the aluminum alloy profile. Taking advantage of the soft and easy-to-deform properties of the silicone material, a lifting platform is used to raise the lower copper plate and the ice sample, so that the ice sample and the copper plate are in close contact to the greatest extent, improving the heat transfer efficiency and reducing the experimental error.

[0017] In addition, the heat-insulating cover made by 3D printing technology in this experiment ensures that the heat generated by the heating plate will not have a significant impact on the ambient temperature, and at the same time ensures that the ice sample and the lower copper plate maintain close contact under the action of their own gravity;

[0018] In addition, a camera is designed in the refrigerator of this experimental device to realize the whole visualization of the experimental process. Therefore, this experimental device is conducive to stimulating students' interest in physics learning and research, and has broad application prospects in experimental teaching, popular science work, and practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the structure of the thermal conductivity test platform of the portable ice thermal conductivity tester of the utility model;

[0020] Figure 2 This is a schematic diagram of the temperature control system structure of the portable ice thermal conductivity tester of the utility model;

[0021] Figure 3 This is a schematic diagram of the structure of the temperature detection system of the present utility model.

[0022] In the figure: 1. Aluminum alloy bracket; 2. Silicone pad; 3. Insulation support; 4. Copper plate; 5. Electric push rod; 6. Lifting platform; 7. Insulation cover; 8. Base; 9. Camera; 10. Transformer; 11. Relay; 12. Temperature controller; 13. Heating plate; 14. pt100 temperature sensor; 15. Data acquisition module; 16. Data conversion module; 17. PC terminal. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] like Figure 1 - Figure 3 As shown, the utility model provides a technical solution: a thermal conductivity testing platform, comprising an aluminum alloy bracket 1;

[0025] A silicone pad 2 is fixed to the top crossbeam of the aluminum alloy bracket 1, a heat-insulating support 3 is fixedly connected to the bottom of the silicone pad 2, and a copper plate 4 is fixedly connected to the bottom of the heat-insulating support 3;

[0026] The bottom of the aluminum alloy bracket 1 is provided with a base 8, the top of the base 8 is provided with a lifting platform 6, the top of the lifting platform 6 is fixedly connected with a heat insulation cover 7, a heating plate 13 is provided above the heat insulation cover 7, and a copper plate 4 is also fixed on the top of the heating plate 13. ， The heat-insulating cover 7 is made by 3D printing technology, and an electric push rod 5 is installed on one side of the aluminum alloy bracket 1.

[0027] Furthermore, the thermal insulation cover 7 and the copper plate 4 are on the same axis, a gap is provided between the thermal insulation cover 7 and the copper plate 4 , and the telescopic end of the electric push rod 5 is between the thermal insulation cover 7 and the copper plate 4 .

[0028] Furthermore, a camera 9 for recording the detection process is installed on one side of the top of the aluminum alloy bracket 1.

[0029] The temperature control system is applied to the thermal conductivity test bench, comprising: a transformer 10, a relay 11, a temperature controller 12, a heating plate 13 and a pt100 temperature sensor 14;

[0030] The pt100 temperature sensor 14 is arranged at the copper plate 4 to detect the temperature of the copper plate 4 . The pt100 temperature sensor 14 is connected to the temperature controller 12 . The temperature controller 12 , the heating plate 13 and the transformer 10 are all electrically connected to the relay 11 .

[0031] The temperature detection system is applied to the thermal conductivity detection platform, including: a pt100 temperature sensor 14 in the temperature control system, a data acquisition module 15, a data conversion module 16, and a PC terminal 17; the temperature sensor 14 is also connected to the data acquisition module 15, and the data acquisition module 15 is connected to the data conversion module 16 and transmitted to the PC terminal 17.

[0032] A portable ice thermal conductivity tester adopts any one of the above thermal conductivity test platforms, temperature control systems or temperature detection systems.

[0033] The mechanical system is mainly composed of an aluminum alloy bracket 1, an electric lifting platform 6, and an electric push rod 5; the temperature control system is mainly composed of a DC regulated power supply, a temperature controller 12, a solid-state relay 11, an AC voltage regulating power supply, and a heating plate 13; the data acquisition system is mainly composed of a DC regulated power supply, a data acquisition module 15, and a PC terminal 17. The device can be operated under the low temperature conditions of the freezer, and most of the operations are completed outside the freezer, thereby reducing the frequency of opening the freezer and reducing the experimental errors caused by changes in ambient temperature. It is simple to operate and is conducive to improving accuracy.

[0034] The semi-automatic operation of this experiment to measure the thermal conductivity of ice is based on the thermal conductivity detection platform among the three modules of thermal conductivity detection platform, temperature control system and temperature detection system. The semi-automatic experiment of this device is realized by wire control and point control handle. The wire control system is mainly used to remotely control the electric lifting platform 6 and the electric push rod 5, and the whole experimental process can be presented on the PC end 17. Its purpose is to ensure that the ambient temperature is not destroyed during the whole experimental process and eliminate the influence of ambient temperature changes on the thermal conductivity measurement of ice. The point control handle is used to specifically control the specific movement of the lifting platform 6 and the electric push rod 5 during the experimental process, so as to realize the contact and separation of the ice sample with the upper and lower copper plates 4 without anyone directly contacting the ice sample, thereby achieving semi-automatic function.

[0035] The temperature control of this experiment is realized based on the temperature control system of the three major systems. The temperature of the lower copper plate 4 is displayed on the temperature controller 12 through the pt100 temperature sensor 14. By setting the hysteresis temperature, the switch of the solid-state relay 11 is controlled, and then the working state of the heating plate 13 is controlled to keep the temperature of the lower copper plate 4 near the set temperature value. It is approximately considered that the temperature of the lower copper plate 4 is constant, achieving the effect of a constant temperature source. When the temperature of the lower copper plate 4 needs to be changed, it is only necessary to change the set temperature on the temperature controller 12. The operation is simple and effective.

[0036] The data collection and analysis of this experiment are realized based on the data collection system of the three major systems. The temperature of the upper copper plate 4 is imported into the PC terminal 17 through the pt100 temperature sensor 14 through the data collection module 15. The collection time interval is set on the upper computer software, and the temperature of the upper copper plate 4 can be recorded once every same time. The collected data is exported and processed, imported into the software, and a curve is fitted to obtain k. The data is automatically recorded through the data collection module 15 to reduce the deviation that may be caused by manual recording, which is conducive to improving the accuracy of the experiment. The curve is fitted by the software, and a fitting method with a higher degree of fitting is selected to calculate k to ensure the accuracy of the experiment.

[0037] At present, the measurement methods of thermal conductivity are mainly divided into steady-state method and non-steady-state method. After consulting existing literature and experiments, the steady-state method and non-steady-state method are compared, and their principles, characteristics and applicable occasions are compared. The test repeatability is poor and the accuracy is not as good as the steady-state method. In the test of thermal insulation materials, its accuracy and repeatability are not as good as the steady-state method. Therefore, we use the steady-state method for detection here;

[0038] Comprehensively considering the common methods in the steady-state method, the heat flow meter method is expensive and is not applicable under sub-zero low temperature conditions; the water flow plate method requires the design of a fluid flow system, and its flow system has a complex mechanical structure and the fluid is easy to solidify at low temperatures, so its feasibility is low; the protective hot plate method has low requirements on the experimental environment temperature conditions, supports thermal conductivity testing under sub-zero low temperature conditions, and the measurement of related physical quantities is simple and easy. The measurement can be completed using existing laboratory equipment, and it has high feasibility.

[0039] After comprehensive consideration, this experiment selected the guarded hot plate method in the steady-state method to measure the thermal conductivity of ice;

[0040] The test mechanism of the guarded hot plate method is as follows: two identical samples to be tested are alternately sandwiched between the cold and hot plates, and the heat is transferred vertically from the central metering panel and the inner guard panel through the sample to the cooling panel, while the temperature of the outer guard panel is the average temperature of the cold and hot plates to reduce the edge heat exchange of the sample, thereby ensuring that a one-dimensional vertical heat flow can be formed on the sample. In addition, if one of the samples is replaced with an auxiliary heating module, a test device with a single sample structure can be constructed. When a stable temperature gradient is formed in the sample, the temperature and thermal power of each module are measured, and the thermal conductivity of the sample can be calculated. The calculation formula is as follows:

[0041]

[0042] Where: λ is the thermal conductivity of the sample, in W·m -1 ·K -1 ; Q is the heating power of the measuring panel, in W; h is the thickness of the sample to be tested, in m; S is the calorimetric area, in m 2 ; T h is the hot surface temperature of the sample, in K; T c is the cold surface temperature of the sample, in K;

[0043] In the experimental calculation, when the length and width of the flat wall exceed 10 times the thickness, the three-dimensional heat conduction is treated as one-dimensional heat conduction, and the error is no more than 1%. During the experiment, the inner diameter of the frozen ice mold was 90mm and the height was 5mm, which met the requirements of treating three-dimensional heat conduction as one-dimensional heat conduction proposed in the literature.

[0044] The theoretical basis of this experiment is Fourier's law:

[0045]

[0046] The amount of heat conducted over a period of time is:

[0047]

[0048] Further conversion to the heat flow formula:

[0049]

[0050] Where ΔT = T1-T2, T1 is the temperature of the lower heating plate, T2 is the temperature of the upper heat sink, S = π·(D / 2) 2 , D is the diameter of the ice sample, H is the thickness of the ice sample;

[0051] Depend on When estimating the heat dissipation rate using the formula, the heat dissipation area included is the upper and lower surfaces and the side surfaces of the heat sink, that is, its total area 2π·(d / 2) 2+π·d·h. In the steady-state heat transfer experiment, the upper surface of the heat sink is covered by the sample disk, and its actual heat dissipation area is π·(d / 2) 2 +π·d·h. Considering that the heat dissipation rate of an object is proportional to its heat dissipation area, Formula to be corrected.

[0052] Since the heat transfer rate of the ice sample is equal to the heat dissipation rate of the heat sink when the steady state is reached, and the heat transferred by the ice sample is equal to the heat absorbed by the heat sink. In the experiment, when the heat transfer is steady, the lower surface of the heat sink is covered by the ice sample, so the heat dissipation rate of the heat sink is corrected in the steady state, and the ratio of heat flow is equal to the ratio of heat dissipation area:

[0053]

[0054] When the steady state is reached, the heat dissipation rate of the ice sample is equal to the heat dissipation rate of the heat sink and the heat transferred by the ice sample is equal to the heat absorbed by the heat sink:

[0055] make

[0056] Final thermal conductivity formula:

[0057]

[0058] Where D(m)-ice sample diameter, H(m)-ice sample thickness, d(m)-heating plate diameter, h(m)-heating plate thickness, T1(K)-heating plate temperature, T2(K)-heating plate temperature, c 散热盘 (J.Kg -1 ·K -1 )-Specific heat capacity of heat sink, m 散热盘 (Kg)-heat sink mass, k(K·s -1 )-heat transfer rate.

[0059] By analyzing the measurement formula, we know that D(, H, d, h) can be directly measured by a vernier caliper, T1 is the set heating plate temperature, c 散热盘 By consulting relevant literature, we know that m 散热盘 It can be measured by an electronic scale. If T2 and k are unknown, they can be measured through experiments.

[0060] Although the embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is limited by the attached embodiments and their equivalents.

Claims

1. A portable ice thermal conductivity tester, characterized in that: It comprises a thermal conductivity testing platform and a temperature control system, wherein the thermal conductivity testing platform comprises an aluminum alloy bracket (1); A silicone pad (2) is fixed to the crossbeam at the top end of the aluminum alloy bracket (1); a heat-insulating support (3) is fixedly connected to the bottom of the silicone pad (2); and a copper plate (4) is fixedly connected to the bottom end of the heat-insulating support (3); A base (8) is provided at the bottom of the aluminum alloy bracket (1), a lifting platform (6) is installed on the top of the base (8), a heat insulation cover (7) is fixedly connected to the top of the lifting platform (6), a heating plate (13) is provided above the heat insulation cover (7), a copper plate (4) is also fixed on the top of the heating plate (13), and an electric push rod (5) is also installed on one side of the aluminum alloy bracket (1).

2. A portable ice thermal conductivity tester according to claim 1, characterized in that: The heat-insulating cover (7) and the copper plate (4) are located on the same axis, a gap is provided between the heat-insulating cover (7) and the copper plate (4), and the telescopic end of the electric push rod (5) is located between the heat-insulating cover (7) and the copper plate (4).

3. A portable ice thermal conductivity tester according to claim 1, characterized in that: A camera (9) for recording the detection process is installed on one side of the top of the aluminum alloy bracket (1).

4. A portable ice thermal conductivity tester according to claim 1, characterized in that: The temperature control system comprises: a transformer (10), a relay (11), a temperature controller (12) and a pt100 temperature sensor (14); The pt100 temperature sensor (14) is arranged at the copper plate (4) to detect the temperature of the copper plate (4); the pt100 temperature sensor (14) is connected to the temperature controller (12); and the temperature controller (12), the heating plate (13) and the transformer (10) are all electrically connected to the relay (11).

5. A portable ice thermal conductivity tester according to claim 4, characterized in that: The temperature control system further comprises a data acquisition module (15), a data conversion module (16) and a PC terminal (17); the pt100 temperature sensor (14) is also connected to the data acquisition module (15); the data acquisition module (15) is connected to the data conversion module (16) and transmitted to the PC terminal (17).

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