CN115266814A - Low-temperature thermal conductivity measuring device and measuring method - Google Patents
Low-temperature thermal conductivity measuring device and measuring method Download PDFInfo
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Abstract
The invention discloses a low-temperature heat conductivity testing device and a measuring method, wherein a dipolar cold screen is provided with a dipolar cold plate, one end of a sample to be tested is arranged on the dipolar cold plate, a copper plate is arranged at the other end of the sample to be tested, and a first temperature sensor and a first heating block are arranged on the copper plate; the second temperature sensor and the second heating block are arranged on the diode cooling plate; the secondary cold screen is arranged in the primary cold screen, and the primary cold screen is arranged in the vacuum cavity; the vacuum cavity and the refrigerator are both fixedly arranged on the bracket, and a primary cold head and a secondary cold head of the refrigerator are respectively communicated with the primary cold screen and the secondary cold screen; first temperature sensor and second temperature sensor all are connected with the input of temperature controller, and the output and the second of temperature controller heat the piece and be connected, and first heating piece is connected with hot junction heating power supply, and the one-level cold drawing of first cold screen is connected with quick temperature rise heating power supply. The testing device has less heat leakage and can accurately measure the heat conductivity.
Description
Technical Field
The invention relates to the technical field of low-temperature thermal conductivity measurement, in particular to a low-temperature thermal conductivity measurement device and a measurement method.
Background
Thermal conductivity is one of the basic thermophysical parameters of a substance. With the development of low temperature technology, superconducting technology and aerospace technology and the wide application in the engineering field, the measurement of the thermal conductivity is not only an important means of physical research, but also can provide necessary data for engineering design. For solid materials of the same kind, the low-temperature thermal conductivity of the solid materials still changes along with the change of defects such as temperature, components, impurities, structures and the like, so that the measurement of the low-temperature thermal conductivity of the solid materials plays an important role.
Pages 32-36 of 2008 nd 2 of the journal of the Low temperature engineering disclose a solid material thermal conductivity test system, which is written by Wen and the like, and the test adopts a steady-state longitudinal heat flow method to test the low temperature thermal conductivity of stainless steel, titanium alloy and magnesium alloy. The comparison with the standard sample shows that the test error is within 5 percent. But the result only accords with the experimental condition above the temperature 150k, and the thermal conductivity error gradually increases from 273k to 150k, and the thermal conductivity condition below 150k is not researched.
The pages 1-5 of the 2011 No. 1 of the journal of the Low temperature engineering disclose the development of a low temperature thermal conductivity measuring device taking a refrigerator as a cold source, which is made by Liu Hui Ming and the like. The device adopts the sample test rod that has independent vacuum environment of detachable, compares through the test with the 304 samples of standard stainless steel, has verified the device and has kept within 8% at 8-300K's measuring accuracy, but the error is higher relatively.
The invention patent application with publication number CN104040327A discloses a method for measuring thermal conductivity. The application calculates a first and a second thermal conductivity of the material in a first and a second direction of the material based on the shape of the isotherm and based on a first and a second temperature detected at a point of the front side of the material at two points in time. But it has not been specifically disclosed how to reduce the error in thermal conductivity.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: how to reduce the error in thermal conductivity.
In order to solve the technical problems, the invention provides the following technical scheme:
a low-temperature thermal conductivity measuring device comprises a support, a vacuum cavity, a primary cold shield, a secondary cold shield, a refrigerator, a measuring unit and a control unit;
the two-pole cold screen is provided with a two-pole cold plate, and one end of a sample to be detected is arranged on the two-pole cold plate;
the secondary cold screen is arranged in the primary cold screen, and the primary cold screen is arranged in the vacuum cavity;
the vacuum cavity and the refrigerator are both fixedly arranged on the bracket, and a primary cold head and a secondary cold head of the refrigerator are respectively communicated with the primary cold screen and the secondary cold screen;
the vacuum cavity is also provided with a vacuumizing hole;
the measuring unit is respectively positioned on the first-stage cold plate of the first cold screen, the two-stage cold plate of the second cold screen and the sample to be measured, and the measuring unit is connected with the control unit.
The advantages are that: the testing device provided by the invention is used for ensuring the environment required by the test through the vacuum cavity and the arranged evacuation port, so that the testing process is more accurate. And a primary cold screen and a secondary cold screen are arranged, so that the heat leakage of the system is reduced, and the heating heat is closer to the true value. Meanwhile, the primary cold screen and the secondary cold screen are respectively connected to the primary cold head and the secondary cold head of the refrigerator, so that heat leakage of the system is reduced. Therefore, the testing device has less heat leakage and can accurately measure the heat conductivity.
Preferably, the control unit comprises a hot end heating power supply, a quick temperature return heating power supply and a temperature controller;
the measuring unit comprises a first temperature sensor, a second temperature sensor, a first heating block and a second heating block;
the first temperature sensor and the second temperature sensor are both connected with the input end of a temperature controller, the output end of the temperature controller is connected with a second heating block, the first heating block is connected with a hot end heating power supply, and a primary cold plate of the first cold screen is connected with a rapid temperature return heating power supply;
the first temperature sensor and the first heating block are arranged at the other end of the sample to be detected; and the second temperature sensor and the second heating block are arranged on the diode cooling plate.
Preferably, still include the copper, the copper fixed mounting is in the other end of the sample that awaits measuring, first temperature sensor and first heating block are installed on the copper.
Preferably, the copper plate has a thickness of 2mm.
Preferably, the support is of a rectangular frame structure, and the temperature controller, the hot end heating power supply and the rapid temperature return heating power supply are all installed in the support.
Preferably, the device also comprises an electric connector and a lead; the hot end heating power supply is connected with the first heating block through an electric connector and a lead, the quick temperature return heating power supply and the lead are connected with the first cold plate through the electric connector, and the temperature control instrument is connected with the first temperature sensor and the second temperature sensor through the electric connector and the lead respectively.
Preferably, the conducting wire is subjected to heat sink treatment and is wound on the outer side wall of the secondary cooling screen.
Preferably, the first temperature sensor and the second temperature sensor are both in model DT670; the model of the refrigerator is GM210.
Preferably, the model of the hot-end heating power supply is PS3003D, and the model of the rapid temperature-returning heating power supply is PS6005D; the model of the temperature controller is Lakeshore336.
The invention also discloses a measuring method applying the low-temperature thermal conductivity testing device, which comprises the following steps:
s1, fixedly mounting the bottom of a sample to be measured on a dipolar cold plate, loading an indium sheet on a contact surface, and measuring the diameter D and the height L;
s2, fixedly mounting a copper plate at the upper end of a sample to be detected, and loading an indium sheet on a contact surface;
s3, mounting the first temperature sensor and the first heating block at the upper end of the copper plate, and respectively measuring and heating the temperature to obtain heat flow Q and hot end temperature T1;
s4, installing a second temperature sensor and a second heating block on the cold plate, and respectively measuring and controlling the temperature to obtain a lower end surface temperature T2; obtaining a contact area A according to the used first temperature sensor and the first heating block;
s5, carrying out simulation analysis on the sample to be detected to obtain the temperature T of the upper surface of the sample table under an ideal condition; obtaining equivalent thermal resistance R according to the power Q of the heating power supply; wherein, the calculation formula is:
in the formula, R is equivalent thermal resistance generated by the contact of the first temperature sensor 8, the first heating block 10 and the copper plate 15, T1 is the temperature of the upper surface of the sample to be measured, T is the temperature of the upper surface of the sample to be measured in an ideal state, and Q is a loaded heat flow value;
s6, during calculation, considering thermal resistance to obtain the real thermal conductivity lambda, wherein the calculation formula is as follows:
in the formula, λ is the calculated real thermal conductivity, T1 is the temperature of the upper surface of the sample to be measured, T2 is the temperature of the lower surface of the sample to be measured, Q is the loaded heat flow value, R is the thermal resistance, L is the height of the sample to be measured, and a is the contact area of the first temperature sensor, the first heating block and the copper plate.
Compared with the prior art, the invention has the beneficial effects that:
(1) The testing device provided by the invention adopts the vacuum cavity and the arranged evacuation port to ensure the environment required by the test, so that the testing process is more accurate. And a primary cold screen and a secondary cold screen are arranged, so that the heat leakage of the system is reduced, and the heating heat is closer to the true value. Meanwhile, the primary cold screen and the secondary cold screen are respectively connected to the primary cold head and the secondary cold head of the refrigerator, so that heat leakage of the system is reduced. Therefore, the heat leakage of the testing device is less, and the heat conductivity can be accurately measured.
(2) The testing device carries out heat sink on related wires and winds on the outer side wall of the dipolar cold screen, so that solid heat conduction and heat leakage can be ignored.
(3) According to the invention, the influence of contact thermal resistance is found to be larger through tests and simulations, the sensor, the heater and the like are calibrated, the heat leakage can be minimized through the arrangement of the testing device, but the thermal resistance cannot be eliminated even if indium sheets, heat conduction grease coating and other modes are adopted. Therefore, the invention provides an optimization method based on thermal resistance elimination, and experiments prove that the thermal conductivity error is far smaller than the error in the literature, the accuracy is improved by more than 100 percent, in any material test, if the thermal resistance between contact surfaces can be obtained, the test error is greatly reduced, and if the material is unknown, the thermal resistance error caused by the heater sensor in the invention can be eliminated automatically. Therefore, the testing method has high accuracy.
Drawings
FIG. 1 is a schematic diagram of an overall structure of a first embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating an internal structure of a vacuum chamber according to a first embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a sample to be tested of the testing device according to the first embodiment of the invention;
FIG. 4 is a schematic structural view of a stainless steel according to a second embodiment of the present invention;
FIG. 5 is a graph showing simulation results of stainless steel according to a second embodiment of the present invention;
FIG. 6 is a schematic thermal conductivity and error map of stainless steel of example two of the present invention;
FIG. 7 is a schematic view of a structure of oxygen-free copper according to a second embodiment of the present invention;
fig. 8 is a schematic view of thermal conductivity and error of oxygen-free copper according to a second embodiment of the present invention.
Detailed Description
In order to facilitate the understanding of the technical solutions of the present invention for those skilled in the art, the technical solutions of the present invention will be further described with reference to the drawings attached to the specification.
The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
Example one
Referring to fig. 1, the embodiment discloses a low-temperature thermal conductivity measuring device, which includes a support 1, a vacuum chamber 5, a primary cold shield 6, a secondary cold shield 7, a refrigerator 12, a control unit, and a measuring unit.
The control unit comprises a hot end heating power supply 2, a quick temperature return heating power supply 3 and a temperature controller 4; the measuring unit comprises a first temperature sensor 8, a second temperature sensor 9, a first heating block 10 and a second heating block 11. The support 1 is of a rectangular frame structure, and the hot end heating power supply 2, the quick temperature return heating power supply 3 and the temperature controller 4 are all installed inside the support 1.
Referring to fig. 2 and 3, the vacuum chamber 5 is fixedly installed at the upper end of the bracket 1, the primary cold shield 6 is installed inside the vacuum chamber 5, the secondary cold shield 7 is installed inside the primary cold shield 6, and the sample 14 to be measured is installed inside the secondary cold shield 7. Specifically, the vacuum cavity 5, the primary cold shield 6 and the secondary cold shield 7 are all of a cylindrical structure, the vacuum cavity 5, the primary cold shield 6 and the secondary cold shield 7 can be arranged to be a common rotating shaft, the rotating shaft is in a vertical direction, the primary cold shield 6 is located in the middle of the vacuum cavity 5, and the secondary cold shield 7 is located in the middle of the primary cold shield 6. Further, the vacuum chamber 5 may be mounted on the frame 1 by means of a screw connection. In this embodiment, the primary cold screen 6, the secondary cold screen 7 and the corresponding connection mode are adopted, which is beneficial to reducing the heat leakage of the system, so that the heating heat is close to the real value as much as possible.
Meanwhile, the refrigerator 12 is fixedly installed at the bottom of the vacuum cavity 5, and the primary cold head 121 and the secondary cold head of the refrigerator 12 are respectively connected to the primary cold screen 6 and the secondary cold screen 7, so that heat leakage of the system is reduced, and measurement errors are reduced.
The two-pole cold screen 7 has a two-pole cold plate 701 at the bottom, the sample 14 to be measured is mounted on the two-pole cold plate 701 at the bottom in a threaded connection manner, and a copper plate 15 is mounted at the upper end of the sample 14 to be measured in a threaded connection manner.
The first temperature sensor 8 and the first heating block 10 are fixedly arranged on the copper plate 15, and the second temperature sensor 9 and the second heating block 11 are arranged on one side of the diode cold plate 701, where the sample 14 to be measured is arranged. The thickness of the copper plate 15 of this embodiment is 2mm, and the temperature error of the two sides of the copper plate 15 is very little for the default test temperature of the steel plate is the temperature of the upper end face of the sample 14 to be measured.
The first temperature sensor 8 and the second temperature sensor 9 are both connected with the input end of the temperature controller 4 through the electric connector 13 and an internal heating wire, and the second heating block 11 is connected with the output end of the temperature controller 4 through the electric connector 13 and the internal heating wire; the first connecting block is connected with the hot end heating power supply 2 through an electric connector 13 and an internal heating wire; the first-stage cold plate 601 at the lower end of the first-stage cold screen 6 is connected with the rapid temperature-returning heating power supply 3.
The hot junction heating power supply 2 of this embodiment heats the copper plate 15 through the first heating block 10, and the quick temperature return heating power supply 3 is connected with the one-level cold plate 601 of the one-level cold shield 6 and is used for enabling the whole system to quickly return to the temperature. The temperature controller 4 receives temperature signals of the first temperature sensor 8 and the second temperature sensor 9, and then controls the temperature of the lower end of the sample 14 to be measured.
Meanwhile, the lower end of the vacuum cavity 5 is further provided with an evacuation port 501, and an external evacuation device is connected to the evacuation port 501, so that the interior of the vacuum cavity 5 is vacuumized, and the interior of the vacuum cavity 5 can be kept in a vacuum state.
In some embodiments, all the connecting wires are subjected to heat sinking and wound on the outer side wall of the secondary cooling screen, so that the temperature of the conducting wires led out from the inside of the sample stage is almost equal to the temperature of the secondary cooling head 122 of the refrigerator 12, thereby eliminating the influence caused by heat conduction and leakage, and further enabling the test process of the embodiment to ignore solid heat conduction and leakage.
In some embodiments, chiller 12 is model GM210. The GM210 refrigerator 12 can satisfy the thermal conductivity measurement in the 20K-300K temperature region, and can satisfy the requirement of the thermal conductivity measurement of the present embodiment.
Meanwhile, the first temperature sensor 8 and the second temperature sensor 9 are both model DT670. The model of the hot-end heating power supply 2 is PS3003D, and the model of the rapid temperature-returning heating power supply 3 is PS6005D. The temperature controller 4 is of the type Lakeshore336.
In some embodiments, the four ends of the frame 1 are also mounted with wheels 101 for movement, facilitating movement of the entire testing device.
The testing device of the embodiment heats and returns the temperature of the sample 14 to be tested through the hot end heating power supply 2 and the quick temperature return heating power supply 3, and controls the temperature of the lower end of the sample 14 to be tested through the temperature controller 4. And the structural design of the primary cold screen 6 and the secondary cold screen 7 is adopted, so that the error of the whole device in the measurement process is reduced as much as possible.
Example two
The implementation also discloses a measuring method of the low-temperature thermal conductivity measuring device in the first application embodiment, which comprises the following steps:
s1, fixedly mounting the bottom of a sample 14 to be measured on a two-pole cold plate 701, loading an indium sheet on a contact surface, and measuring the diameter D and the height L;
s2, fixedly mounting a copper plate 15 at the upper end of a sample 14 to be tested, and loading an indium sheet on a contact surface;
s3, mounting the first temperature sensor 8 and the first heating block 10 on the upper end of the copper plate 15, and respectively measuring and heating the temperature to obtain heat flow Q and hot end temperature T1;
s4, mounting the second temperature sensor 9 and the second heating block 11 on a cold plate, and respectively measuring and controlling the temperature to obtain a lower end surface temperature T2; and the contact area a is obtained from the first temperature sensor 8 and the second temperature sensor 9 used.
S5, carrying out simulation analysis on the sample 14 to be detected to obtain the temperature T of the upper surface of the sample table under an ideal condition; obtaining equivalent thermal resistance R according to the power Q of the heating power supply; wherein, the calculation formula is:
in the formula, R is equivalent thermal resistance generated by the contact of the first temperature sensor 8, the first heating block 10 and the copper plate 15, T1 is the temperature of the upper surface of the sample 14 to be measured, T is the temperature of the upper surface of the sample 14 to be measured in an ideal state, and Q is a loaded heat flow value.
S6, during calculation, the thermal resistance is considered, and the real thermal conductivity lambda is obtained, wherein the calculation formula is as follows:
in the formula, λ is the calculated real thermal conductivity, T1 is the temperature of the upper surface of the sample 14 to be measured, T2 is the temperature of the lower surface of the sample 14 to be measured, Q is the loaded heat flow value, R is the thermal resistance, L is the height of the sample 14 to be measured, and a is the contact area of the first temperature sensor 8, the first heating block 10 and the copper plate 15.
In steps S1 and S2, the sample 14 to be measured is fixedly mounted on the cold plate and the copper plate 15 by a screw connection.
Systematic errors originate from multiple directions: system error of instruments and meters, solid heat conduction of wires, and thermal resistance between contact surfaces.
Contact resistance refers to the difference between the temperatures of the two interfacing surfaces divided by the heat flux.
The heat leakage of the system is neglected, the temperature of the secondary cold screen and the temperature of the primary cold screen 6 are respectively consistent with the temperature of the respective cold heads, and the radiation heat leakage can be neglected; the wire is wound on the cold screen to be used as a heat sink, so that the heat leakage of the wire can be ignored, the reading error of the instrument is 1%, and the comprehensive error is very small and can be ignored.
The function of the contact thermal resistance is optimized, the contact thermal resistance generates temperature errors on contact surfaces, the thermal resistance between the wall surface contact surfaces cannot be realized no matter indium sheets are loaded or silver paste is coated, and particularly in a material test with high thermal conductivity, extremely small temperature difference can cause great thermal conductivity errors, so the thermal resistance cannot be ignored. The thermal conductivity result is more accurate because only the tiny heat leakage is left after the contact thermal resistance is optimized.
In the present embodiment, stainless steel is used as the sample 14 to be measured to design:
first, the structure of the stainless steel of the present embodiment is shown in fig. 4. The stainless steel has good thermal conductivity stability in the whole temperature zone, and has standard database comparison. Facilitating the comparison.
The stainless steel is then placed in a measuring device, the bottom of the stainless steel is fixedly mounted on a two-pole cold plate 701, the contact surface is loaded with indium plates, and the diameter D and height L of the stainless steel are measured simultaneously. Specifically, the diameter D and the height L are obtained by taking an average of a plurality of measurements.
The holed copper plate 15 is then fixed to the upper end of the stainless steel by means of external threads, the contact surface is loaded with indium flakes, and the contact is increased by loading indium flakes on the contact surface, reducing the measurement error.
The first temperature sensor 8 and the first heating block 10 are arranged at the upper end of the copper plate 15 and are used for measuring and heating the temperature respectively to obtain heat flow Q and hot end temperature T1. The thickness of the copper plate 15 of the embodiment is 2mm, the temperature error of the two surfaces of the copper plate 15 is small, and the default test temperature is the temperature of the upper end surface of the stainless steel.
The second temperature sensor 9 and the second heating block 11 are installed on the cold plate, and temperature measurement and temperature control are respectively performed to obtain the lower end surface temperature T2.
Carrying out simulation analysis on the stainless steel to obtain the temperature T of the upper surface of the stainless steel under an ideal condition; FIG. 5 is a simulation result of stainless steel at cold end 77K, according to real data T1 measured in the experiment, and according to power Q of the heating power supply, obtaining equivalent thermal resistance R; wherein, the calculation formula is:
in the formula, R is an equivalent thermal resistance generated by the contact of the first temperature sensor 8, the first heating block 10 and the copper plate 15, T1 is a temperature of the upper surface of the sample 14 to be measured, T is a temperature of the upper surface of the sample 14 to be measured in an ideal state, and Q is a loaded heat flow value.
The size of the heating block of this embodiment is 10 x 10mm, and the contact area of the first temperature sensor 8 and the second temperature sensor 9 is 40.77mm2According to the proportion of the contact thermal resistance to the contact surface area, the equivalent heat group value generated at the hot end of the stainless steel sample is analyzed and calculated to be 0.69K/W, the error is far greater than other factors, and therefore the thermal resistance needs to be considered。
And finally, taking the thermal resistance into consideration during calculation to obtain the real thermal conductivity lambda, wherein the calculation formula is as follows:
in the formula, λ is the calculated real thermal conductivity, T1 is the temperature of the upper surface of the sample 14 to be measured, T2 is the temperature of the lower surface of the sample 14 to be measured, Q is the loaded heat flow value, R is the thermal resistance, L is the height of the sample 14 to be measured, and a is the contact area between the first temperature sensor 8, the first heating block 10 and the copper plate 15.
The calculation is carried out by a formula of thermal conductivity and the measured data, the result is shown in fig. 6, a square scatter point represents a theoretical value of stainless steel, and a curve 1 is a thermal conductivity correction value corresponding to the square scatter point; the triangle scatter point represents the relative error between the corrected value and the theoretical value, the curve 2 is the average error of a plurality of measured thermal conductivities at fixed temperatures corresponding to the corrected value, the graph can clearly show that the thermal conductivity after the correction of the embodiment has high coincidence in a measured temperature zone, meanwhile, the error of the thermal conductivity at a single temperature is less than 3%, and the average thermal conductivity is about 1%.
Therefore, the optimized result of the test value of the embodiment has an error of about 1% at the temperature of 20-300K. The accuracy of thermal conductivity measurement is improved.
The thermal conductivity of oxygen-free copper varies greatly at low temperatures, and the thermal conductivity results from thermal contact resistance using oxygen-free copper were verified. Therefore, oxygen-free copper is used as the sample 14 to be tested for auxiliary verification. The specific experimental process is the same as that of stainless steel, and is not described herein.
FIG. 7 is a test sample structure of oxygen-free copper, the middle thin rod is a test sample, the model of the oxygen-free copper is different from a stainless steel structure, the middle thin rod and the upper and lower surfaces are integrated to reduce the contact thermal resistance of the sample, and the diameter of the test sample piece is smaller due to the larger thermal conductivity of the oxygen-free copper, so that the model is suitable for temperature test of more than 100K. The thermal resistance in the model is generated on the lower surfaces of the cold plate and the copper body, the heater and the sensorThe device and the upper surface of the copper body. According to the analysis of stainless steel above, the thermal resistance of the cold plate to the lower surface of the sample, along with other errors, produced an error of about 1%, and therefore, the thermal contact resistance of the sensor to the heater was the primary factor. The contact thermal resistance is proportional to the contact area, the stainless steel thermal resistance calculated according to the above is 0.69K/W, and the area of the heating block is 100mm2The contact area of the sensor is 40.77mm2Total contact area of 1036mm for upper and lower surfaces of the test piece2Therefore, the contact thermal resistance of the heating block and the sensor can be distributed to be 0.3K/W according to the contact area. Wherein, table 1 is partial verification data for oxygen free copper.
TABLE 1
Fig. 8 is a schematic view for verifying thermal conductivity of oxygen-free copper, in which curve 3 is corrected thermal conductivity and curve 4 is theoretical thermal conductivity, and it can be known from fig. 8 by combining the data of table 1 that the error of the thermal conductivity of oxygen-free copper applying the method is less than 2.9% when the thermal conductivity is 100-200 k.
Therefore, the present embodiment provides an optimization method based on elimination of thermal resistance influence, so that the measurement of any unknown material physical property by using the same thermal conductivity of the heater and the sensor as in the present embodiment has high accuracy.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein, and any reference signs in the claims are not to be construed as limiting the claims.
The above-mentioned embodiments only represent embodiments of the present invention, and the scope of the present invention is not limited to the above-mentioned embodiments, and it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit of the present invention, and these embodiments are all within the scope of the present invention.
Claims (10)
1. A low temperature thermal conductivity measuring device is characterized in that: the device comprises a bracket (1), a vacuum cavity (5), a primary cold screen (6), a secondary cold screen (7), a refrigerator (12), a measuring unit and a control unit;
the two-pole cold screen (7) is provided with a two-pole cold plate (701), and one end of a sample (14) to be tested is arranged on the two-pole cold plate (701);
the two-stage cold shield (7) is arranged inside the first-stage cold shield (6), and the first-stage cold shield (6) is arranged inside the vacuum cavity (5);
the vacuum cavity (5) and the refrigerating machine (12) are both fixedly arranged on the bracket (1), and a primary cold head (121) and a secondary cold head of the refrigerating machine (12) are respectively communicated with the primary cold screen (6) and the secondary cold screen (7);
the vacuum cavity (5) is also provided with a vacuumizing opening (501);
the measuring unit is respectively arranged on the first-stage cold plate (601) of the first cold screen (6), the two-stage cold plate (701) of the second cold screen (7) and the sample (14) to be measured, and the measuring unit is connected with the control unit.
2. The low temperature thermal conductivity measurement device of claim 1, wherein: the control unit comprises a hot end heating power supply (2), a quick temperature return heating power supply (3) and a temperature controller (4);
the measuring unit comprises a first temperature sensor (8), a second temperature sensor (9), a first heating block (10) and a second heating block (11);
the first temperature sensor (8) and the second temperature sensor (9) are both connected with the input end of the temperature controller (4), the output end of the temperature controller (4) is connected with the second heating block (11), the first heating block (10) is connected with the hot-end heating power supply (2), and the primary cold plate (601) of the first cold screen (6) is connected with the quick temperature return heating power supply (3);
the first temperature sensor (8) and the first heating block (10) are arranged at the other end of the sample (14) to be measured; the second temperature sensor (9) and the second heating block (11) are arranged on the two-pole cold plate (701).
3. The low temperature thermal conductivity measurement device of claim 2, wherein: the copper plate (15) is further included, and the thickness of the copper plate (15) is 2mm;
copper (15) fixed mounting is in the other end of the sample (14) that awaits measuring, first temperature sensor (8) and first heating piece (10) are installed on copper (15).
4. The low temperature thermal conductivity measurement device of claim 3, wherein: the thickness of the copper plate (15) is 2mm.
5. The low temperature thermal conductivity measurement device of claim 2, wherein: the support (1) is of a rectangular frame structure, and the temperature controller (4), the hot end heating power supply (2) and the quick temperature return heating power supply (3) are all installed in the support (1).
6. The low temperature thermal conductivity measurement device of claim 2, wherein: also comprises an electric connector (13) and a lead; the hot junction heating power supply (2) is connected with the first heating block (10) through an electric connector (13) and a lead, the quick temperature return heating power supply (3) and the lead are connected with the first cold plate through the electric connector (13), and the temperature control instrument (4) is respectively connected with the first temperature sensor (8) and the second temperature sensor (9) through the electric connector (13) and the lead.
7. The low temperature thermal conductivity measurement device of claim 6, wherein: the conducting wire is subjected to heat sink treatment and wound on the outer side wall of the two-pole cold screen (7).
8. The low temperature thermal conductivity measurement device of claim 2, wherein: the models of the first temperature sensor (8) and the second temperature sensor (9) are both DT670; the model of the refrigerating machine (12) is GM210.
9. The low temperature thermal conductivity measurement device of claim 2, wherein: the type of the hot-end heating power supply (2) is PS3003D, and the type of the quick temperature-returning heating power supply (3) is PS6005D; the model of the temperature controller (4) is Lakeshore336.
10. A measurement method using the low temperature thermal conductivity test apparatus according to any one of claims 1 to 9, characterized in that: the method comprises the following steps:
s1, fixedly mounting the bottom of a sample (14) to be measured on a two-pole cold plate (701), loading an indium sheet on a contact surface, and measuring the diameter D and the height L;
s2, fixedly mounting a copper plate (15) at the upper end of a sample (14) to be tested, and loading an indium sheet on a contact surface;
s3, mounting the first temperature sensor (8) and the first heating block (10) at the upper end of the copper plate (15), and respectively measuring and heating the temperature to obtain a heat flow Q and a hot end temperature T1;
s4, a second temperature sensor (9) and a second heating block (11) are arranged on the cold plate, and temperature measurement and temperature control are respectively carried out to obtain the temperature T2 of the lower end face; and obtaining a contact area A according to the used first temperature sensor (8) and the first heating block (10);
s5, carrying out simulation analysis on the sample (14) to be detected to obtain the temperature T of the upper surface of the sample table under an ideal condition; obtaining equivalent thermal resistance R according to the power Q of the antipyretic power supply; wherein, the calculation formula is:
in the formula, R is equivalent thermal resistance generated by the contact of the first temperature sensor (8), the first heating block (10) and the copper plate (15), T1 is the temperature of the upper surface of the sample (14) to be measured, T is the temperature of the upper surface of the sample (14) to be measured in an ideal state, and Q is a loaded heat flow value;
s6, during calculation, considering thermal resistance to obtain the real thermal conductivity lambda, wherein the calculation formula is as follows:
in the formula, lambda is the calculated real heat conductivity, T1 is the temperature of the upper surface of the sample (14) to be measured, T2 is the temperature of the lower surface of the sample (14) to be measured, Q is the loaded heat flow value, R is the thermal resistance, L is the height of the sample (14) to be measured, and A is the contact area of the first temperature sensor (8), the first heating block (10) and the copper plate (15).
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