CN109709140B - Method and device for measuring local convective heat transfer coefficient under microscale - Google Patents
Method and device for measuring local convective heat transfer coefficient under microscale Download PDFInfo
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Abstract
The invention provides a method and a device for measuring local convective heat transfer coefficient under microscale, which are characterized in that direct current is conducted to a conductive filament through a DC direct current power supply, a stable temperature gradient is established on the conductive filament in an electric heating mode, an infrared imager is used for obtaining a temperature distribution diagram of the conductive filament, and the local convective heat transfer coefficients at different points on the conductive filament can be obtained according to a related formula of the local convective heat transfer coefficient under the microscale based on temperature values at different positions in the extracted temperature distribution diagram. The device realizes the measurement of the local convective heat transfer coefficient, improves the measurement precision and accuracy, has simple equipment, high measurement precision, good reliability and wide measurement application range, and realizes the technical effect of obtaining the effective measurement of the local convective heat transfer coefficient under the microscale.
Description
Technical Field
The invention relates to the technical field of heat transfer, in particular to a method and a device for measuring a local convective heat transfer coefficient under a microscale.
Background
The natural convection heat transfer coefficient is a basic parameter for evaluating the heat transfer capacity between a fluid and a solid surface, and has a wide application background in the field of heat transfer engineering. With the increasing miniaturization of electronic devices, the microscopic mechanism of convective heat transfer between materials and surrounding gases at the microscale changes, and the assumption of continuous media in macroscopic hydrodynamics and the like are not applicable, so that the value of convective heat transfer coefficient is several orders of magnitude larger than that at the macroscale. Therefore, the method for accurately obtaining the convective heat transfer coefficient of the material under the microscale has important significance on early-stage thermal management analysis of the electronic device.
Infrared imaging is a technique that receives the radiant energy emitted by an object and then extrapolates its temperature back. The local convective heat transfer coefficient refers to the convective heat transfer coefficient of the material at different positions, and the value of the convective heat transfer coefficient can change along with the temperature, the size of a sample and the like. At present, most of experimental measurements are average convective heat transfer coefficients, which only represent the overall level of heat transfer between a material and surrounding fluid and cannot reflect the actual heat transfer intensity of the material at different positions.
In the prior art, patent CN105891255A discloses a method and a system for measuring convective heat transfer coefficient and specific heat capacity of single nanoparticle. The method can simultaneously measure the convective heat transfer coefficient and the specific heat capacity of the nanoparticles, but the method only measures the average convective heat transfer coefficient of the surfaces of the nanoparticles. In addition, the method needs to use a probe to contact with the surface of an actual sample, so that the heat exchange flow field of the sample and surrounding fluid is damaged to a certain extent, and the heat exchange flow field deviates from actual convection heat exchange to a certain extent. Patent CN101285786A discloses a method for measuring the local convective heat transfer coefficient of a microchannel by using a harmonic detection technique. According to the method, the size of a temperature value is obtained through a micro sensor arranged at the bottom of a micro groove, and then the local convection heat transfer coefficient in the micro groove is determined by utilizing the frequency response characteristic of the sensor to the temperature. Due to the limitation of the actual size and the arrangement position of the sensor, the data points which can be measured by the method are very limited, and the measurement result of the local convective heat transfer coefficient is related to the size of the micro sensor and is actually an average value corresponding to the size area of the sensor.
As can be seen from the above, the conventional measurement method has the technical problems that the local convective heat transfer coefficient cannot be measured, and the measurement result is deviated.
Disclosure of Invention
In view of this, the present invention provides a method and an apparatus for measuring a local convective heat transfer coefficient on a microscale, so as to solve or at least partially solve the technical problems that the existing measurement method cannot measure the local convective heat transfer coefficient and the measurement result is biased.
The invention provides a method for measuring local convective heat transfer coefficient under microscale, which comprises the following steps:
step S1: bonding two ends of the micro-scale conductive filament on the metal heat sink by using a conductive adhesive, wherein the diameter of the micro-scale conductive filament is 10-100 micrometers;
step S2: a DC direct current power supply is adopted to supply constant current to the micro-scale conductive filaments, and the magnitude of the current value applied at the moment is recorded;
step S3: when the electric heating reaches a steady state, an infrared thermal image of the micro-scale conductive filament is obtained by shooting through an infrared imager;
step S4: processing an infrared thermal image shot by an infrared imager host through a data collection computer to obtain a temperature distribution map, dividing the conductive filament into a preset number of micro-element areas according to the size of the geometric dimension corresponding to the pixel points in the temperature distribution map, and extracting temperature values of different micro-element areas, wherein the number of the divided micro-element areas is the same as the number of the pixel points in the temperature distribution map;
step S5: calculating resistance values corresponding to different infinitesimal areas according to the temperature values of the different infinitesimal areas, and calculating electric heating power corresponding to the different infinitesimal areas according to the resistance values corresponding to the different infinitesimal areas;
step S6: and obtaining the local convective heat transfer coefficient according to the diameter of the micro-scale conductive filament, the temperature values of different infinitesimal regions, the geometric length of the infinitesimal regions, the electric heating power of the infinitesimal regions and the ambient temperature.
In one embodiment, before step S3, the method further comprises:
and judging whether the electric heating reaches a stable state or not by measuring the voltage value of the micro-scale conductive filament.
In one embodiment, the processing the infrared thermography taken by the infrared imager host through the data collection computer in step S4 to obtain the temperature distribution map specifically includes:
and acquiring a temperature distribution diagram through infrared thermography processing software preset in a data collection computer.
In one embodiment, step 5 specifically includes:
calculating to obtain the resistance value of the micro-scale conductive filament according to the corresponding relation between the temperature and the resistivity of different infinitesimal regions;
and calculating the electric heating power corresponding to different infinitesimal areas according to the resistance value and the heating current value.
In one embodiment, calculating the resistance value corresponding to the infinitesimal area according to the temperature values of different infinitesimal areas specifically includes:
obtaining the resistivity at the corresponding temperature according to the temperatures of different infinitesimal areas and the materials of the micro-scale conductive filaments;
and obtaining the resistance value corresponding to the infinitesimal area according to the resistivity, the area of the cross section of the micro-scale conductive filament and the diameter of the micro-scale conductive filament.
In one embodiment, the temperature values of the different infinitesimal areas comprise the temperature value t of the infinitesimal area to be calculatedmTemperature value t of the previous infinitesimal area of the infinitesimal area to be calculatedm-1And the temperature value t of the subsequent infinitesimal area of the infinitesimal area to be calculatedm+1In step S6, the calculation formula of the local convective heat transfer coefficient is specifically:
wherein h ismIs the local convective heat transfer coefficient, d is the diameter of the micro-scale conductive filament, lambda is the thermal conductivity of the micro-scale conductive filament, Q is the electrical heating power of the infinitesimal region, Deltax is the size of the infinitesimal region, tfIn terms of ambient temperature,. epsilon.is the emissivity of the microscale conductive filaments, and. sigma.is the Stefan-Boltzmann constant.
Based on the same inventive concept, a second aspect of the present invention provides a measuring apparatus applied to the method of the first aspect, the apparatus comprising:
a supporting frame is arranged on the base plate,
the infrared imager comprises an optical lens and an infrared imager host, is arranged in the middle of the support frame, and is provided with a three-dimensional moving platform arranged at the bottom of the support frame;
the metal heat sink is arranged on the three-dimensional mobile platform, and two ends of the metal heat sink are connected with a DC (direct current) power supply;
the micro-scale conductive filament is arranged on the three-dimensional moving platform, two ends of the micro-scale conductive filament are connected to the metal heat sink through the conductive adhesive,
the distance between the micro-scale conductive filament and the infrared imager lens and the relative position of the micro-scale conductive filament in the horizontal direction can be regulated and controlled through the three-dimensional mobile platform, and the distance between the micro-scale conductive filament and the optical lens is a preset distance.
In one embodiment, the present invention provides an apparatus wherein:
the preset distance between the micro-scale conductive filament and the optical lens is not more than 7 cm.
In one embodiment, the present invention provides an apparatus wherein the three-dimensional movable stage is adjusted to an accuracy of 10 microns in both the horizontal and vertical directions.
In one embodiment, the invention provides a device wherein the microscale electrically conductive filaments have a length of 1 cm.
One or more technical solutions in the embodiments of the present application have at least one or more of the following technical effects:
on one hand, according to the method for measuring the local convective heat transfer coefficient under the microscale, the infrared thermograph shot by the infrared imager host is processed through the data collection computer to obtain a temperature distribution map, the conductive filaments are divided into the infinitesimal areas with the preset number according to the size of the geometric dimension corresponding to the pixel points in the temperature distribution map, and the temperature values of different infinitesimal areas are extracted; then, calculating resistance values corresponding to different infinitesimal areas according to the temperature values of the different infinitesimal areas, and calculating electric heating power corresponding to the different infinitesimal areas according to the resistance values corresponding to the different infinitesimal areas; and then obtaining the local convective heat transfer coefficient according to the diameter of the micro-scale conductive filament, the temperature values of different infinitesimal regions, the geometric length of the infinitesimal regions, the electric heating power of the infinitesimal regions and the ambient temperature. The local convective heat transfer coefficient can be obtained according to the conditions of temperature, electric heating power and the like of different infinitesimal regions, so that the actual heat transfer intensity of the material at different positions can be reflected. Therefore, the measurement of the local convective heat transfer coefficient is realized, and the accuracy and precision of the measurement can be improved because the conductive filaments are divided into the micro-element areas with the preset number according to the size of the geometric dimension corresponding to the pixel points in the temperature distribution diagram and the temperature values of different micro-element areas are extracted.
On the other hand, the measuring device provided by the invention can replace materials with different diameters, and meanwhile, the power of electric heating is adjustable, so that the local convective heat transfer coefficients of the materials under different scales and different temperature levels are researched; the device belongs to non-contact measurement, does not damage the heat exchange flow field of the material and surrounding fluid in the measurement process, has simple equipment, high measurement precision, good reliability and wide measurement application range, and realizes effective measurement for obtaining the local convection heat transfer coefficient under the micro-scale.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a flow chart of a method for measuring local convective heat transfer coefficient at a microscale in one embodiment;
FIG. 2 is a structural diagram of a device for measuring a local convective heat transfer coefficient at a microscale in an embodiment.
Detailed Description
The invention provides a method and a device for measuring a local convective heat transfer coefficient under a microscale, which are used for solving the technical problems that the local convective heat transfer coefficient cannot be measured and the measurement result has deviation in the existing measurement method.
The invention relates to a method and a device for measuring local convective heat transfer coefficient under microscale. The method comprises the steps of conducting constant current to a conductive filament through a DC direct current power supply, establishing a stable temperature gradient on the conductive filament in an electric heating mode, obtaining a temperature distribution diagram of the conductive filament by using an infrared imager, extracting temperature values at different positions based on the temperature distribution diagram, and obtaining local convective heat transfer coefficients at different points on the conductive filament according to a related formula of the local convective heat transfer coefficients under the measurement microscale.
The invention has the following advantages: 1. for micro-scale materials, the local convective heat transfer coefficient on the material can be directly measured; 2. the diameter of the material can be controlled and changed, and the power of electric heating can be adjusted, so that the local convective heat transfer coefficients of the material at different scales and different temperature levels can be researched; 3. the method is non-contact measurement, and does not damage the heat exchange flow field of the material and the surrounding fluid in the measurement process; 4. the method has the advantages of simple equipment, high measurement precision, good reliability and wide measurement application range, and realizes effective measurement of the local convective heat transfer coefficient under the microscale.
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
The embodiment provides a method for measuring a local convective heat transfer coefficient on a microscale, please refer to fig. 1, the method includes:
step S1 is first executed: and adhering two ends of the micro-scale conductive filament to the metal heat sink by using a conductive adhesive, wherein the diameter of the micro-scale conductive filament is 10-100 micrometers.
Specifically, the diameter of the micro-scale conductive filament may be selected as required, and the conductive adhesive may be a conventional conductive adhesive or a highly conductive adhesive, such as silver-based conductive paste, gold-based conductive paste, copper-based conductive paste, and carbon-based conductive paste. In order to improve the conductivity, the metal heat sink can be a red copper electrode, and the conductive adhesive can be silver paste. The micro-scale conductive filaments and the red copper electrode are bonded together through the silver paste, so that the contact resistance between the conductive filaments and the metal heat sink is reduced, and the conduction is facilitated.
Then, step S2 is executed: and (3) applying constant current to the micro-scale conductive filaments by using a DC direct current power supply, and recording the magnitude of the applied current value.
Specifically, a constant current may be applied through the micro-scale conductive filaments by a DC direct current power supply, and the temperature of the conductive filaments may be changed by changing the magnitude of the direct current so as to obtain local convective heat transfer coefficients at different temperatures.
Step S3 is then executed: and when the electric heating reaches a stable state, an infrared thermal image of the micro-scale conductive filament is obtained by shooting through an infrared imager.
In one implementation, before step S3, the method further includes:
and judging whether the electric heating reaches a stable state or not by measuring the voltage value of the micro-scale conductive filament.
Specifically, since the resistance of the micro-scale conductive filament is temperature dependent, when the temperature of the conductive filament is constant, the resistance value of the filament will also remain at a constant value. In a specific implementation process, the voltage at two ends of the filament can be measured in real time, and after the electric heating reaches a stable state, the voltage value at two ends of the filament is constant, so that the fact that the electric heating process reaches a stable state is judged.
Step S4 is executed next: processing an infrared thermal image shot by an infrared imager host through a data collection computer to obtain a temperature distribution diagram, dividing the conductive filament into a preset number of micro-element areas according to the size of the geometric dimension corresponding to the pixel points in the temperature distribution diagram, and extracting temperature values of different micro-element areas, wherein the number of the divided micro-element areas is the same as the number of the pixel points in the temperature distribution diagram.
Specifically, the infrared thermography can be processed by processing software preset in the data collection computer to obtain a temperature distribution map. Since the length of the conductive filament is much greater than its diameter, the conductive filament can be considered a one-dimensional object. And then dividing the conductive filament into a plurality of infinitesimal areas according to the size of the geometric dimension corresponding to the pixel points in the temperature distribution map, so as to extract temperature values at different infinitesimal areas, wherein the temperature values at different infinitesimal areas are the temperatures at the infinitesimal areas corresponding to the pixel points.
Step S5: and calculating the resistance values corresponding to the different infinitesimal areas according to the temperature values of the different infinitesimal areas, and calculating the electric heating power corresponding to the different infinitesimal areas according to the resistance values corresponding to the different infinitesimal areas.
Specifically, because the conductive filament resistance has a one-to-one correspondence relationship with the temperature, the magnitude of the actual resistance R of the resistance values corresponding to different infinitesimal regions can be calculated according to the correspondence relationship
Step S6: and obtaining the local convective heat transfer coefficient according to the diameter of the micro-scale conductive filament, the temperature values of different infinitesimal regions, the geometric length of the infinitesimal regions, the electric heating power of the infinitesimal regions and the ambient temperature.
Specifically, the geometric length of the infinitesimal region can be calculated through different infinitesimal regions obtained in the previous steps, the ambient temperature can be measured through a temperature meter or a temperature sensor, and when convective heat transfer is carried out between the ambient temperature and surrounding fluid, the radiation heat transfer is considered, so that the local convective heat transfer coefficient h in the region of the conductive filament m can be obtainedmThe calculation formula of (2). Thereby realizing the measurement of the local convective heat transfer coefficient hmTherefore, the actual heat exchange strength of the material at different positions is reflected, and the measurement accuracy is improved.
In one implementation, the step S4 of processing the infrared thermography taken by the infrared imager host through the data collection computer to obtain the temperature distribution map specifically includes:
and acquiring a temperature distribution diagram through infrared thermography processing software preset in a data collection computer.
In one implementation, step 5 specifically includes:
calculating to obtain the resistance value of the micro-scale conductive filament according to the corresponding relation between the temperature and the resistivity of different infinitesimal regions;
and calculating the electric heating power corresponding to different infinitesimal areas according to the resistance value and the heating current value.
Specifically, calculating a resistance value corresponding to the infinitesimal area according to temperature values of different infinitesimal areas specifically includes:
obtaining the resistivity at the corresponding temperature according to the temperatures of different infinitesimal areas and the materials of the micro-scale conductive filaments;
and obtaining the resistance value corresponding to the infinitesimal area according to the resistivity, the area of the cross section of the micro-scale conductive filament and the diameter of the micro-scale conductive filament.
Specifically, after the temperatures of different infinitesimal regions of the material are obtained, the resistivity ρ at the corresponding temperatures can be further obtained in combination with the measured material. The resistance value of the infinitesimal region is R ═ ρ Δ x/a, where Δ x is the geometric length corresponding to the infinitesimal region, and a ═ d2And/4 is the area of the cross section of the filament, wherein d is the diameter of the filament.
After the resistance value is calculated, Q can be equal to I2And R, calculating to obtain the electric heating power.
In one implementation, the temperature values of the different infinitesimal areas include a temperature value t of the infinitesimal area to be calculatedmTemperature value t of the previous infinitesimal area of the infinitesimal area to be calculatedm-1And the temperature value t of the subsequent infinitesimal area of the infinitesimal area to be calculatedm+1In step S6, the calculation formula of the local convective heat transfer coefficient is specifically:
wherein h ismIs the local convective heat transfer coefficient, d is the diameter of the micro-scale conductive filament, lambda is the thermal conductivity of the micro-scale conductive filament, Q is the electrical heating power of the infinitesimal region, Deltax is the size of the infinitesimal region, tfIn terms of ambient temperature,. epsilon.is the emissivity of the microscale conductive filaments, and. sigma.is the Stefan-Boltzmann constant.
Based on the same inventive concept, the application also provides a device applied to the measurement of the local convective heat transfer coefficient under the micro-scale in the first embodiment, which is detailed in the second embodiment.
Example two
The present embodiment provides a measuring apparatus applied to the method of claim 1, referring to fig. 2, the apparatus includes:
a support frame 6 is arranged on the upper portion of the frame,
the infrared imager 5 comprises an optical lens 3 and an infrared imager main body 1, is arranged in the middle of the supporting frame 6,
the three-dimensional moving platform 9 is arranged at the bottom of the support 6;
the metal heat sink 8 is arranged on the three-dimensional mobile platform 9, and two ends of the metal heat sink 8 are connected with the DC direct-current power supply 2;
a micro-scale conductive filament 7 which is arranged on a three-dimensional moving platform 9, two ends of the micro-scale conductive filament are connected with a metal heat sink 8 through a conductive adhesive 4,
the distance between the micro-scale conductive filament and the infrared imager lens and the relative position of the micro-scale conductive filament in the horizontal direction can be regulated and controlled through the three-dimensional mobile platform, and the distance between the micro-scale conductive filament and the optical lens is a preset distance.
Specifically, the two ends of the micro-scale conductive filament 7 are connected to the metal heat sink 8 by the conductive adhesive 4, the two ends of the metal heat sink 8 are connected with the DC power supply 2, and the temperature of the conductive filament 7 can be changed by changing the magnitude of the DC current. The support frame 6 is connected with the infrared imager 5 through screws, a plurality of screw holes are formed in the support frame 6, and the installation height of the infrared imager host 1 can be adjusted according to the focusing distance of the optical lens 3 used by the infrared imager host 1. The three-dimensional movable platform 9 is arranged at the bottom of the support frame, and can regulate and control the distance between the conductive filament 7 and the infrared imager lens 3 and the relative position of the conductive filament 7 in the horizontal direction. The metal heat sink 8 and the conductive filament 7 are placed on a three-dimensional movable platform 9 and should be kept at a certain distance from the optical lens 3.
In one implementation, in the apparatus provided in this embodiment,
the preset distance between the micro-scale conductive filament and the optical lens is not more than 7 cm.
Specifically, the mounting distance of the optical lens 4 from the conductive filament 7 cannot be too large, and the value of the mounting distance does not exceed 7cm in order to ensure the vicinity of the best focus plane.
In one implementation, the device provided in this embodiment has an adjustment precision of 10 μm for both the horizontal direction and the vertical direction of the three-dimensional movable platform.
Specifically, the three-dimensional movable platform 9 is used to adjust the distance between the conductive filament 7 and the optical lens 3 and the relative position in the horizontal direction, and in order to ensure that the focal plane of the optical lens 3 can be accurately adjusted on the conductive filament 7, the adjustment precision of the three-dimensional movable platform in the horizontal direction and the vertical direction is 10 microns.
In one implementation, the device provided in this example has a microscale conductive filament length of 1 cm.
Specifically, the infrared imager main body 5 is connected to the data collecting computer 1, and can photograph and collect a temperature distribution map of the conductive filament. The length of the conductive thread 7 should not be too long, typically around 1cm, to ensure that the measuring threads are in the ir imaged image. The value of the direct current output by the DC direct current power supply 2 can be adjusted so that the conductive filaments 7 are heated to different temperatures. But the current value should not be too large to avoid the phenomenon of overheating and fusing of the microscale conductive filaments 7, and the current value can be controlled between 1mA and 200 mA.
Alternatively, the diameter of the conductive filament 7 may be replaced in order to study the magnitude of the local convective heat transfer coefficient at different scales.
The embodiment provides a device applied to the measurement of the local convective heat transfer coefficient under the micro-scale in the first embodiment. The device can replace materials with different diameters, and simultaneously the power of electric heating can be adjusted, so that the local convective heat transfer coefficients of the materials with different scales and different temperature levels are researched; the device belongs to non-contact measurement, does not damage the heat exchange flow field of materials and surrounding fluids in the measurement process, has simple equipment, high measurement precision, good reliability and wide measurement application range, and realizes effective measurement for obtaining the local convection heat transfer coefficient under the microscale.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.
Claims (9)
1. A method for measuring local convective heat transfer coefficient under microscale is characterized by comprising the following steps:
step S1: bonding two ends of the micro-scale conductive filament on the metal heat sink by using a conductive adhesive, wherein the diameter of the micro-scale conductive filament is 10-100 micrometers;
step S2: a DC direct current power supply is adopted to supply constant current to the micro-scale conductive filaments, and the magnitude of the current value applied at the moment is recorded;
step S3: when the electric heating reaches a steady state, an infrared thermal image of the micro-scale conductive filament is obtained by shooting through an infrared imager;
step S4: processing an infrared thermal image shot by an infrared imager host through a data collection computer to obtain a temperature distribution map, dividing the conductive filament into a preset number of micro-element areas according to the size of the geometric dimension corresponding to the pixel points in the temperature distribution map, and extracting temperature values of different micro-element areas, wherein the number of the divided micro-element areas is the same as the number of the pixel points in the temperature distribution map;
step S5: calculating resistance values corresponding to different infinitesimal areas according to the temperature values of the different infinitesimal areas, and calculating electric heating power corresponding to the different infinitesimal areas according to the resistance values corresponding to the different infinitesimal areas;
step S6: obtaining a local convective heat transfer coefficient according to the diameter of the micro-scale conductive filament, temperature values of different infinitesimal regions, the geometric length of the infinitesimal regions, the electric heating power of the infinitesimal regions and the ambient temperature;
wherein, the temperature values of different infinitesimal areas comprise the temperature value t of the infinitesimal area to be calculatedmTemperature value t of the previous infinitesimal area of the infinitesimal area to be calculatedm-1And the temperature value t of the subsequent infinitesimal area of the infinitesimal area to be calculatedm+1In step S6, the calculation formula of the local convective heat transfer coefficient is specifically:
wherein h ismIs the local convective heat transfer coefficient, d is the diameter of the micro-scale conductive filament, lambda is the thermal conductivity of the micro-scale conductive filament, Q is the electrical heating power of the infinitesimal region, Deltax is the size of the infinitesimal region, tfIn terms of ambient temperature,. epsilon.is the emissivity of the microscale conductive filaments, and. sigma.is the Stefan-Boltzmann constant.
2. The method of claim 1, wherein prior to step S3, the method further comprises:
and judging whether the electric heating reaches a stable state or not by measuring the voltage value of the micro-scale conductive filament.
3. The method of claim 2, wherein the step S4 of processing the infrared thermography image taken by the infrared imager host through the data collection computer to obtain the thermography profile includes:
and acquiring a temperature distribution diagram through infrared thermography processing software preset in a data collection computer.
4. The method according to claim 2, wherein step 5 specifically comprises:
calculating to obtain the resistance value of the micro-scale conductive filament according to the corresponding relation between the temperature and the resistivity of different infinitesimal regions;
and calculating the electric heating power corresponding to different infinitesimal areas according to the resistance value and the heating current value.
5. The method of claim 4, wherein calculating the resistance value corresponding to the infinitesimal area according to the temperature values of different infinitesimal areas specifically comprises:
obtaining the resistivity at the corresponding temperature according to the temperatures of different infinitesimal areas and the materials of the micro-scale conductive filaments;
and obtaining the resistance value corresponding to the infinitesimal area according to the resistivity, the area of the cross section of the micro-scale conductive filament and the diameter of the micro-scale conductive filament.
6. A measuring device for use in the method of claim 1, the device comprising:
a supporting frame is arranged on the base plate,
the infrared imager comprises an optical lens and an infrared imager host which are arranged in the middle of the supporting frame,
the three-dimensional moving platform is arranged at the bottom of the support frame;
the metal heat sink is arranged on the three-dimensional mobile platform, and two ends of the metal heat sink are connected with a DC (direct current) power supply;
the micro-scale conductive filament is arranged on the three-dimensional moving platform, two ends of the micro-scale conductive filament are connected to the metal heat sink through the conductive adhesive,
the distance between the micro-scale conductive filament and the infrared imager lens and the relative position of the micro-scale conductive filament in the horizontal direction can be regulated and controlled through the three-dimensional mobile platform, and the distance between the micro-scale conductive filament and the optical lens is a preset distance.
7. The apparatus of claim 6, comprising:
the preset distance between the micro-scale conductive filament and the optical lens is not more than 7 cm.
8. The apparatus of claim 6, wherein the three-dimensional movable stage is adjusted to an accuracy of 10 μm in both the horizontal direction and the vertical direction.
9. The device of claim 6, wherein the microscale electrically conductive filament has a length of 1 cm.
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| CN111323453A (en) * | 2020-03-25 | 2020-06-23 | 武汉大学 | Method and device for measuring convective heat transfer coefficients of different surface roughness under microscale |
| CN112415044B (en) * | 2020-10-14 | 2022-03-15 | 武汉大学 | Method for detecting specific heat capacity of solid based on mechanical means |
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