Concentric circle pipe contact thermal resistance measuring device and measuring method thereof

Abstract

The invention provides a concentric circular tube contact thermal resistance measuring device and a measuring method thereof, and belongs to the technical field of measuring devices. The device comprises a vacuum cover which is externally connected with a vacuum pump and a high-pressure gas source; the heating rod is arranged in the vacuum cover and is used for heating the concentric circular tube; the outer circulation cooling device is arranged in the vacuum cover and sleeves the heating rod and the concentric circular tube; the temperature sensor is used for collecting temperature data at the radius of the concentric circular tube; and the contact part of the concentric circular tube and the vacuum cover is hermetically connected through a heat-insulating material. According to the invention, the measurement of the contact thermal resistance between cylindrical surfaces and the measurement of the contact thermal resistance of more than 1500 DEG C can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of measuring devices, and in particular to a concentric tube contact thermal resistance measuring device and a measuring method thereof. Background Art

[0002] Contact thermal resistance: When two solids are in contact and heat transfer, there is a contact thermal resistance between the two solid contact surfaces. The solid surface that looks flat at a macroscopic level actually has many small bumps and small grooves. Therefore, the solid surface contact at a macroscopic level is actually the contact of some discrete points and surfaces, and the actual contact area accounts for only about one percent of the overall surface. Other non-contact places produce tiny air chambers filled with atmospheric gas. Because these air chambers are extremely small, the atmospheric gas hardly flows between the air chambers, so the heat transfer method of the air chamber part is heat conduction and radiation. When the temperature is low, the radiation heat transfer is very small and can be ignored. Therefore, the heat conduction between the two solid contact surfaces at a macroscopic level is through the contact heat conduction of some discrete points and surfaces and through the tiny air chambers. The thermal conductivity of gas is significantly weaker than that of solids, and heat preferentially passes through the contact surface of solids. Therefore, the heat transfer on the contact surface of two solids at a macroscopic level produces thermal contraction, which is the contact thermal resistance.

[0003] At present, most of the research on contact thermal resistance is focused on two solid planes. It can be roughly divided into three directions: pure theoretical model research, numerical simulation research and experimental research. Existing research shows that the influencing factors of contact thermal resistance are complex. On a macro level, they belong to cross-disciplinary subjects such as geometry, heat, and mechanics (force). The influencing factors include the thermal properties of materials, the elastic-plastic properties of materials, surface shape, processing methods, temperature, contact pressure, and gap media; on a micro level, the influencing factors include surface roughness, microscopic morphology, and the elastic-plastic deformation of surface peaks. The current level of pure theoretical model and numerical simulation research cannot be directly applied to engineering practice.

[0004] For example, the invention patent with the publication number CN 114384116 A discloses an efficient test device and method for interface contact thermal resistance under high temperature conditions. The device includes two upper and lower test modules: the upper test module is composed of an upper loading rod, two specimens, an upper insulation barrel, a lower loading platform and a heating unit; the lower test module is composed of an upper loading platform, two specimens, a lower insulation barrel and a lower loading platform; the entire test module is placed on a lower support platform. The loading device is connected to the test machine and the specimen to load stress on the specimen; the heating unit is located between the upper and lower test modules and heats the upper and lower modules at the same time; the insulation barrel adopts a split structure, and the interlayer is filled with insulation materials to reduce the lateral heat transfer; the insulation barrel and the specimen are processed with channels for installing temperature measuring thermocouples, and the temperature of the corresponding point is measured by the thermocouple in the specimen to calculate the interface contact thermal resistance of the specimen. Its structure limits the measurement of the contact thermal resistance between two planes, and the test in both the upper and lower directions makes it impossible to directly obtain the heat flow through the contact surface, which introduces calculation errors.

[0005] In the above-mentioned prior art, due to structural limitations, only the contact thermal resistance between planes can be tested. There are few measurements of the contact thermal resistance between cylindrical surfaces. The latest cylindrical contact thermal resistance measurement is the invention patent with the publication number CN 115266815A, which uses the transient method, based on the numerical solution of the transient heat conduction problem, and gives the cylindrical interface contact thermal resistance through the inverse problem processing method. It repeatedly iterates the initial set contact thermal resistance value, so that the experimental measurement value is closest to the numerical result, and the contact thermal resistance can be obtained, but its accuracy is affected by the measurement time and the limitation of material properties. The numerical model deviates from reality due to the assumption of isotropy. Its transient method requires additional measurement of the thermal conductivity, specific heat capacity and density of the sample to perform numerical simulation of the temperature field, and its accuracy is limited by the influence of the measurement time and the limitation of material properties, which increases the measurement cost and measurement error. And its measurement range is only up to 1400°C, and it is impossible to measure the contact thermal resistance at higher temperatures (over 1500°C). Summary of the invention

[0006] In view of this, in order to solve the above-mentioned deficiencies in the prior art, on the one hand, the present invention provides a concentric tube contact thermal resistance measuring device, which can measure the contact thermal resistance between cylindrical surfaces and can measure the contact thermal resistance exceeding 1500°C.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A concentric tube contact thermal resistance measuring device, comprising:

[0009] A vacuum cover, which is externally connected to a vacuum pump and a high-pressure gas source;

[0010] A heating rod, which is disposed in the vacuum cover and is used to heat the concentric tubes;

[0011] An external circulation cooling device is arranged in the vacuum cover and sleeved outside the heating rod and the concentric tube;

[0012] The temperature sensor is used to collect temperature data at the radius of the concentric tubes.

[0013] Preferably, the contact point between the concentric circular tube and the vacuum cover is sealed and connected by a heat-insulating material.

[0014] Preferably, the external circulation cooling device is a cooling water jacket.

[0015] On the other hand, the present invention also provides a measurement method of the above-mentioned concentric tube contact thermal resistance measurement device, comprising the following steps:

[0016] 1) Select two concentric circular tubes as the outer sample and the inner sample respectively, open temperature measuring holes for the temperature sensor to collect temperature data at the radius position of the outer sample and the inner sample, put the inner sample outside the heating rod, and put the outer sample outside the inner sample and contact the surface of the inner sample;

[0017] 2) Turn on the high-pressure gas source and use a non-contact high-resolution microscopic imaging system to measure the three-dimensional morphology data of the contact surface of the outer sample, and obtain the overall comprehensive roughness including flatness through post-processing;

[0018] 3) Use one-dimensional steady state to directly measure the contact thermal resistance, as follows:

[0019] Turn on the vacuum pump to evacuate the vacuum cover, and at the same time turn on the high-pressure gas source to inject inert gas into the vacuum cover. After reaching the target pressure, turn off the high-pressure gas source;

[0020] Turn on the external circulation cooling device, set the temperature of the cooling medium, wait for the cooling medium to stably and evenly fill the external circulation cooling device, turn on the heating rod, and set the heating power;

[0021] After the temperature data collected by the temperature sensor is stable, it can be judged that the system has reached a steady-state heat conduction state, and the electric power at this time and the temperature at each sample radius are recorded;

[0022] The contact thermal resistance is calculated using the temperature data and the electrical power of the heating rod.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The concentric tube contact thermal resistance measuring device provided by the present invention can realize the measurement of contact thermal resistance between cylindrical surfaces and the measurement of contact thermal resistance exceeding 1500°C. In particular, by adopting a heating rod (resistance heating method), its electrothermal energy conversion efficiency can almost reach 100%, and the heating temperature can reach up to 2000°C.

[0025] The measuring method of the concentric tube contact thermal resistance measuring device provided by the present invention uses a steady-state method for measurement. The heat flux size is the electric power size of the heating rod. There is no need to additionally measure the heat flux, which reduces measurement errors, simplifies the measuring device, and improves measurement accuracy.

[0026] The measuring method of the concentric circular tube contact thermal resistance measuring device provided by the present invention, according to the steady-state method, measures the temperature distribution of the solid on both sides of the interface along the heat flow direction, and then fits the temperature of the solid on both sides of the interface based on the Fourier heat transfer law, thereby obtaining the temperature difference on both sides of the interface to calculate the interface thermal resistance. Compared with the measurement of planar contact thermal resistance, the circular tube transfers heat along the radial direction, and the heat flux density of the circular cross section with different radii is different. Compared with the transient method, the present invention saves the testing cost of the transient method for measuring the thermal conductivity, specific heat capacity and density of the material. Compared with the transient method, the steady-state method directly obtains the contact thermal resistance with higher accuracy. Therefore, the total heat flow is used to calculate the contact thermal resistance in this method, rather than the heat flux density. It greatly simplifies the test device and improves the accuracy of its test method. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the measuring device of the present invention;

[0028] In the figure, 1. vacuum cover, 2. vacuum pump, 3. high-pressure gas source, 4. heating rod, 5. external circulation cooling device, 6. concentric tubes, 7. temperature sensor, 8. thermal insulation material. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0030] In the description of the present invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "provided with", "mounted / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] like Figure 1 As shown, the present invention provides a concentric tube contact thermal resistance measuring device, comprising:

[0033] A vacuum cover 1 is externally connected to a vacuum pump 2 and a high-pressure gas source 3, wherein the vacuum pump 2 is used to extract gas from the vacuum cover 1, and the high-pressure gas source 3 is used to fill the vacuum cover 1 with an inert gas (wherein the inert gas is preferably nitrogen), and the high-pressure gas source 3 is turned off after reaching the target pressure;

[0034] The heating rod 4 is arranged in the vacuum cover 1 and is used to heat the concentric tubes 6. Figure 1 The figure shows an outer layer sample and an inner layer sample which are sleeved together and have cylindrical surfaces in contact with each other, wherein the heating rod 4 heats the sample by means of resistance heating;

[0035] An external circulation cooling device 5 is arranged in the vacuum cover 1 and sleeved outside the heating rod 4 and the concentric tube 6;

[0036] A temperature sensor 7, which is used to collect temperature data at the radius of the concentric tube 6;

[0037] In the present invention, the contact point between the concentric tube 6 and the vacuum cover 1 is sealed and connected by a heat insulating material 8;

[0038] Among them, preferably, after the concentric tube 6 is installed in the vacuum cover 1, the places where its two ends contact the vacuum cover 1 are sealed and connected by the thermal insulation material 8, and a temperature measuring hole is opened at the radius of the concentric tube 6 (the thermal insulation material 8 is adapted to the openings at both ends of the concentric tube 6, and the radius of the concentric tube 6 is the radius of the thermal insulation material 8). The thermal insulation material 8 prevents axial heat dissipation and ensures one-dimensional heat transfer along the axial direction. Finally, the temperature distribution along the radial direction is measured, and the temperature measuring probe passes through the thermal insulation material 8 and is finally connected to the two samples.

[0039] In the present invention, the external circulation cooling device 5 is a cooling water jacket.

[0040] On the other hand, the present invention also provides a measurement method of the above-mentioned concentric tube contact thermal resistance measurement device, comprising the following steps:

[0041] 1) Select two concentric circular tubes as the outer sample and the inner sample respectively, open temperature measuring holes for the temperature sensor to collect temperature data at the radius position of the outer sample and the inner sample, put the inner sample outside the heating rod, and put the outer sample outside the inner sample and contact the surface of the inner sample;

[0042] Wherein, before step 1), the preparation and processing of the sample to be tested are also included, as follows:

[0043] Prepare concentric tubes of corresponding diameters and lengths according to different types of materials, drill temperature measuring holes at different radius positions, and process the contact surfaces by turning, milling, planing, grinding and coating;

[0044] 2) Turn on the high-pressure gas source and use a non-contact high-resolution microscopic imaging system to measure the overall three-dimensional morphology of the contact surface of the outer sample. The three-dimensional morphology data is post-processed to obtain the overall comprehensive roughness including flatness. Repeat step 2) to obtain the volume comprehensive roughness of the contact surface of the inner sample;

[0045] 3) Use one-dimensional steady state to directly measure the contact thermal resistance, as follows:

[0046] Turn on the vacuum pump to evacuate the vacuum cover, turn on the high-pressure gas source, inject inert gas (wherein the inert gas is preferably nitrogen) into the vacuum cover, and turn off the high-pressure gas source after reaching the target pressure;

[0047] Turn on the external circulation cooling device, set the temperature of the cooling medium, wait for the cooling medium to stably and evenly fill the external circulation cooling device, turn on the heating rod, and set the heating power, wherein the cooling medium is preferably water;

[0048] After the temperature data collected by the temperature sensor is stable, it can be judged that the system has reached a steady-state heat conduction state, and the electric power at this time and the temperature at each sample radius are recorded;

[0049] The contact thermal resistance is calculated using the temperature data read and the electrical power of the heating rod;

[0050] The calculation formula may be as follows:

[0051] First, the electric power of the heating rod is the heating heat flux Q after steady state;

[0052] Secondly, the average temperature T1 of the inner surface of the outer layer sample and the average temperature T2 of the outer surface of the inner layer sample can be calculated based on the temperature distribution;

[0053] Finally, according to the thermal resistance calculation formula, thermal resistance R = (T2-T1) / Q.

[0054] The above are only preferred specific implementations of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and improved concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A concentric tube contact thermal resistance measuring device, characterized in that: include: A vacuum cover, which is externally connected to a vacuum pump and a high-pressure gas source; A heating rod, which is disposed in the vacuum cover and is used to heat the concentric tubes; An external circulation cooling device is arranged in the vacuum cover and sleeved outside the heating rod and the concentric tube; The temperature sensor is used to collect temperature data at the radius of the concentric tubes.

2. A concentric tube contact thermal resistance measuring device according to claim 1, characterized in that: The contact point between the concentric tube and the vacuum cover is sealed and connected by a heat-insulating material.

3. A concentric tube contact thermal resistance measuring device according to claim 1-2, characterized in that: The external circulation cooling device is a cooling water jacket.

4. A method for measuring the contact thermal resistance of concentric tubes according to any one of claims 1 to 3, characterized in that: The steps include: 1) Select two concentric circular tubes as the outer sample and the inner sample respectively, open temperature measuring holes for the temperature sensor to collect temperature data at the radius position of the outer sample and the inner sample, put the inner sample outside the heating rod, and put the outer sample outside the inner sample and contact the surface of the inner sample; 2) Turn on the high-pressure gas source and use a non-contact high-resolution microscopic imaging system to measure the three-dimensional morphology data of the contact surface of the outer sample, and obtain the overall comprehensive roughness including flatness through post-processing; 3) Use one-dimensional steady state to directly measure the contact thermal resistance, as follows: Turn on the vacuum pump to evacuate the vacuum cover, and at the same time turn on the high-pressure gas source to inject inert gas into the vacuum cover. After reaching the target pressure, turn off the high-pressure gas source; Turn on the external circulation cooling device, set the temperature of the cooling medium, wait for the cooling medium to stably and evenly fill the external circulation cooling device, turn on the heating rod, and set the heating power; After the temperature data collected by the temperature sensor is stable, it can be judged that the system has reached a steady-state heat conduction state, and the electric power at this time and the temperature at each sample radius are recorded; The contact thermal resistance is calculated using the temperature data and the electrical power of the heating rod.

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