Method and device for measuring contact thermal resistance of solid cylindrical surface

Abstract

A method for measuring contact thermal resistance of a solid cylindrical surface comprises the following steps: winding a tungsten wire on a carbon rod, arranging an inner copper pipe as a heating module, sleeving an inner sleeve and an outer sleeve on the heating module to serve as a test pipe fitting, sleeving an outer copper pipe outside the outer sleeve, and arranging thermocouples on the inner surface and the outer surface of the test pipe fitting; the heating module is used for heating the test pipe fitting, the heat flow q = (Q-Q ') / A of the interface of the inner sleeve and the outer sleeve is calculated according to the heating power Q, the loss power Q' and the outer surface area A of the inner copper pipe, and the interface thermal resistance R = (T1-T2) / q is calculated according to the average temperature T1 of the inner surface of the test pipe fitting and the average temperature T2 of the outer surface of the test pipe fitting. According to the method, the contact thermal resistance on the cylindrical surface can be accurately measured based on a steady-state method, and guidance is provided for heat transfer design and optimization of a solid reactor core. The invention further provides a solid cylindrical surface contact thermal resistance measuring device.

Description

Technical Field

[0001] The invention belongs to the field of heat transfer, and in particular relates to a method and a device for measuring contact thermal resistance of a solid cylindrical surface. Background Art

[0002] There is no liquid loop in the solid-state reactor core, and a solid metal matrix is ​​used as the heat transfer medium between the fuel rod and the heat pipe. Therefore, the heat transfer efficiency between the fuel rod and the metal matrix and between the metal matrix and the heat pipe becomes an important factor affecting the solid-state reactor core. However, on the one hand, the operating temperature of the solid-state reactor core exceeds 700℃, and temperature measurement is difficult; on the other hand, the heat transfer interface of the solid-state core is an arc surface, and conventional thermal resistance test methods are difficult to achieve accurate measurement.

[0003] Patent CN115266815A discloses a method for testing high-temperature contact thermal resistance of a cylindrical interface. However, this method uses a transient method to measure thermal resistance. The structure of the measuring device is complex and the test cost is high. When the contact area of ​​the measured object is large, there are measurement difficulties. The measurement results are greatly affected by the environment, and there are reliability issues during multiple repeated tests. It is difficult to apply to solid-state reactor core heat transfer measurement.

[0004] Therefore, providing a simpler and more reliable method for measuring the contact thermal resistance of solid cylindrical surfaces has positive significance for improving the efficiency of research and development and design of solid-state reactor cores. Summary of the invention

[0005] The purpose of the present invention is to provide a method for measuring the contact thermal resistance of a solid cylindrical surface, so as to improve the efficiency and reliability of heat transfer measurement of a solid reactor core. The present invention also provides a device for measuring the contact thermal resistance of a solid cylindrical surface.

[0006] According to an embodiment of one aspect of the present invention, a method for measuring contact thermal resistance of a solid cylindrical surface is provided, the method comprising the following steps:

[0007] Step a): a carbon rod wrapped with tungsten wire is provided, and an inner copper tube is arranged outside the carbon rod as a heating module; a test pipe is provided, the test pipe comprises a nested outer sleeve and an inner sleeve, the test pipe is sleeved outside the heating module, and an outer copper tube is sleeved outside the test pipe to obtain a thermal resistance measurement test device;

[0008] The thermal resistance measurement test device is provided with a plurality of temperature measurement positions in the axial direction, and at each of the temperature measurement positions, a thermocouple is provided between the outer copper tube and the test tube and between the test tube and the inner copper tube;

[0009] Step b): using the heating module to heat the test pipe and obtain the heating power Q; obtaining the power loss Q' at both ends of the axial direction of the thermal resistance measurement test device, and calculating the heat flow from the heating module to the test pipe as q = (Q-Q') / A, where A is the outer surface area of ​​the inner copper tube;

[0010] The average temperature T1 of the inner surface of the inner sleeve and the average temperature T2 of the outer surface of the outer sleeve are measured and calculated by the thermocouple, and the interface thermal resistance R=(T1-T2) / q between the inner sleeve and the outer sleeve is calculated.

[0011] This method accurately measures the contact thermal resistance on the cylindrical surface based on the steady-state method. It has simple operation, low test cost, and strong repeatability. It is suitable for simulating the actual operating conditions of the solid-state reactor core and can effectively improve the safety design level of the solid-state reactor.

[0012] Furthermore, in some embodiments, the step a) further includes the step of filling a gap between the inner sleeve and the outer sleeve with gas or solid medium.

[0013] According to the actual situation of the specific project, the corresponding medium can be filled in the gap to better simulate the actual heat transfer conditions of the solid-state reactor core.

[0014] Furthermore, in some embodiments, in the step a), at least three temperature measuring positions are provided, and a plurality of the thermocouples are evenly arranged circumferentially on each temperature measuring position.

[0015] Using thermocouples evenly arranged around the circumference to measure temperature is helpful to eliminate random errors in the test process.

[0016] Furthermore, in some embodiments, a calibration test is further included before performing the step b), and the calibration test includes the following steps:

[0017] Providing a calibration sample, wherein the calibration sample is made of the same material as the test pipe fitting, and the wall thickness of the calibration sample is the same as the sum of the wall thicknesses of the outer sleeve and the inner sleeve;

[0018] Substituting the calibration sample for the test pipe in the thermal resistance measurement test device to obtain a calibration test device;

[0019] The calibration sample is heated by the heating module, and the average temperatures of the inner surface and the outer surface of the calibration sample are respectively measured and calculated to obtain the test thermal conductivity of the calibration sample;

[0020] The test thermal conductivity is compared with the standard thermal conductivity of the material of the calibration sample, and when the difference between the test thermal conductivity and the standard thermal conductivity exceeds a given threshold, the test thermal conductivity is corrected by a correction coefficient.

[0021] The calibration test can be used to verify the effectiveness of the test device to further improve the test accuracy.

[0022] Further, in some embodiments, in the step b), the method for obtaining the loss power Q' is:

[0023] The calibration test device is used to measure and calculate the radial heat flux of the calibration test piece using the thermocouple, and the axial heat flux loss Q' is determined according to the difference between the output power of the heating module and the radial heat flux.

[0024] Furthermore, in some embodiments, step b) is performed in a closed test box.

[0025] Conducting the test in a closed test chamber helps to eliminate external environmental interference and reduce the impact of factors such as ambient temperature or convection on the test results.

[0026] Furthermore, in some embodiments, in the step b), the heating temperature does not exceed 900°C.

[0027] Too high test temperature affects the structural stability of the copper tube.

[0028] According to another aspect of the present invention, a solid cylindrical surface contact thermal resistance measuring device is provided, which is used in the solid cylindrical surface contact thermal resistance measuring method provided in any of the above embodiments. The device comprises:

[0029] A heating module, wherein the heating module comprises a carbon rod, a tungsten wire and an inner copper tube, wherein the carbon rod is arranged vertically, the tungsten wire is wound around the carbon rod, and the inner copper tube is sleeved on the outer side of the carbon rod;

[0030] A test pipe, the test pipe comprising an inner sleeve and an outer sleeve of equal length, the inner sleeve is nested in the outer sleeve, and a measurement interface is formed between the inner sleeve and the outer sleeve;

[0031] A heat insulation module, the heat insulation module comprising an outer copper tube and a heat insulation layer, the outer copper tube is sleeved outside the test tube, and the heat insulation layer covers the outer copper tube from the outside;

[0032] A measuring module, wherein the measuring module comprises a plurality of axially arranged thermocouples, wherein the thermocouples comprise an inner thermocouple arranged between the test tube and the inner copper tube and an outer thermocouple arranged between the test tube and the outer copper tube, and each axial position where a thermocouple is arranged is provided with the inner thermocouple and the outer thermocouple arranged in pairs along the radial direction.

[0033] Furthermore, in some embodiments, the device also includes a cooling module, wherein the cooling module is configured as a heat sink, and the heat sink is disposed outside the thermal insulation module.

[0034] The cooling module protects external equipment and further improves the stability and repeatability of test conditions.

[0035] Furthermore, in some embodiments, the device also includes an isolation box, in which an isolation environment is formed to isolate the heating module, the test tube, and the thermal insulation module from the external environment.

[0036] Furthermore, in some embodiments, the measurement module also includes an infrared temperature measuring device, which is disposed in the isolation box and measures the end surface temperature of the test pipe in a non-contact manner.

[0037] The infrared temperature measuring device can perform external verification of the test data through non-contact measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a schematic diagram of the cross-sectional structure of a solid cylindrical surface contact thermal resistance measuring device in one embodiment;

[0039] Figure 2 It is a schematic diagram of the test results of thermal conductivity of the calibration sample in one embodiment.

[0040] Meaning of the reference symbols:

[0041] 1-Carbon rod;

[0042] 2-Inner copper tube;

[0043] 3-Inner casing;

[0044] 4-Outer sleeve;

[0045] 5- Gap;

[0046] 6-outer copper tube;

[0047] 7- Thermal insulation layer;

[0048] 8-Heat sink;

[0049] 9- measuring point;

[0050] 10- base;

[0051] 11- Isolation box;

[0052] 12-Infrared thermometer.

[0053] The purpose of the above drawings is to explain the present invention in detail so that those skilled in the art can understand the technical concept of the present invention, but it is not intended to limit the present invention. For the sake of simplicity, the above drawings only schematically illustrate the structures related to the technical features of the present invention, and do not strictly follow the actual proportions to draw the complete structure and all details. DETAILED DESCRIPTION

[0054] The present invention is further described in detail below through specific embodiments in conjunction with the accompanying drawings.

[0055] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The phrase appearing in various locations in the specification does not necessarily refer to the same embodiment, nor is it limited to mutually exclusive independent or alternative embodiments. Those skilled in the art should be able to understand that the embodiments herein may be combined with other embodiments without causing structural conflicts.

[0056] In the description of this article, unless otherwise clearly specified and limited, the technical terms "installed", "connected", "connected" and the like should be understood in a broad sense, which can be a movable connection, a fixed connection or an integral connection. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of this application can be understood according to specific circumstances.

[0057] In the description of this document, terms indicating orientation or positional relationships, such as "up", "down", "left", "right", "horizontal", "vertical", "height", "length", and "width", are intended to accurately describe the embodiments and simplify the description, but are not intended to limit the parts or structures involved to have a specific orientation, be installed or operate in a specific orientation, and should not be construed as a limitation on the embodiments in this document.

[0058] In the description of this article, the terms "first", "second" and the like are only used to distinguish different objects, and cannot be understood as indicating relative importance or limiting the quantity, specific order or primary and secondary relationship of the described technical features. In the description of this article, the meaning of "plurality" is at least two.

[0059] Solid-state core reactors use high-temperature resistant metals as heat exchange media. Compared with traditional pressurized water reactors, the size and weight can be significantly reduced. At the same time, they have the characteristics of factory prefabrication, transportable equipment, and self-adjustment in operation. Therefore, the solid-state core reactor can be greatly simplified in system design, and can be quickly installed, deployed and applied in different environmental scenarios. Since the core of the solid-state core reactor needs to operate at a high temperature level (above 700°C) for a long time, this is a challenge to the heat transfer performance between the core materials and components.

[0060] The nuclear fuel cladding and the substrate composed of metal exchange heat in the form of cylindrical contact. Due to the influence of assembly and processing technology, the substrate and the fuel cladding cannot fit tightly, resulting in a contact gap, which increases the contact thermal resistance of the fuel cladding-substrate interface. This will greatly reduce the heat transfer efficiency between the substrate and the cladding, causing nuclear fuel overheating, which directly affects the safe and stable operation of the reactor. Therefore, measuring the contact thermal resistance of the cylindrical surface at high temperature is crucial for the safety design of the reactor. For the test device for measurement, the solid core cylindrical surface contact thermal resistance measurement test needs to simulate the high temperature, contact state and other factors during the operation of the core, and obtain the contact thermal resistance under different combinations of parameters such as temperature and contact form through reasonable measurement methods.

[0061] At present, common contact thermal resistance measurement methods generally include transient method and steady-state method. The transient measurement method generally has the characteristics of short cycle, fast response, high resolution, and can measure films / interfaces of special shapes. However, the transient method is difficult to achieve high-temperature measurement and measurement requirements of larger contact scales. The steady-state method is mainly based on the American national standards ASTM E1105 and ASTM D5470-06. Its physical meaning is clear. It is generally based on one-dimensional thermal conductivity principles and formulas and has high accuracy. However, it has high requirements for measurement technology at high temperatures, and the existing technology cannot be directly applied to the contact thermal resistance measurement of solid cylindrical surfaces.

[0062] Therefore, there is an urgent need for a steady-state cylindrical surface contact thermal resistance measurement test method suitable for the high temperature requirements of the solid core operating environment, which can be used to measure the contact thermal resistance of the fuel cladding-matrix of the solid core reactor in a high temperature environment.

[0063] To this end, an embodiment of one aspect of the present invention provides a method for measuring the contact thermal resistance of a solid cylindrical surface. Figure 1 The solid cylindrical surface contact thermal resistance measuring device is used for measurement.

[0064] The method comprises the following steps:

[0065] Firstly, a solid cylindrical surface contact thermal resistance measuring device is provided.

[0066] A carbon rod 1 is vertically arranged on the base 10, a tungsten wire is wound on the carbon rod 1, and then an inner copper tube 2 is arranged outside the carbon rod. The carbon rod 1, the tungsten wire and the inner copper tube 2 together serve as a heating module. The tungsten wire generates heat as a heating wire after being energized, and the inner copper tube 2 has good thermal conductivity, which can ensure uniform axial heat generation of the heating module. The vertically arranged heating module can avoid uneven axial and circumferential contact caused by gravity and thermal deformation under heating conditions when arranged horizontally, and reduce system errors. The device can simulate high temperature conditions not exceeding 900°C.

[0067] The test tube is sleeved outside the heating module. The test tube includes an inner sleeve 3 and an outer sleeve 4 of equal length, the inner sleeve 3 and the outer sleeve 4 are coaxially arranged, the outer sleeve 4 is sleeved outside the inner sleeve 3, and the interface between the inner sleeve 3 and the outer sleeve 4 is used as the thermal resistance interface to be measured in the test. According to the actual working environment of the simulated solid core, the gap 5 between the inner sleeve 3 and the outer sleeve 4 can be set to a vacuum state, or filled with gas or solid medium.

[0068] An outer copper tube 6 is provided on the outside of the outer sleeve 4 to improve the uniformity of the axial temperature distribution. An insulation layer 7 is provided on the outside of the outer copper tube 6 to play a role in heat preservation and reduce the influence of environmental factors on the test results. An oil cooling plate heat sink 8 is provided on the outside of the insulation layer 7 to provide a stable temperature environment and obtain the temperature gradient required for the test.

[0069] The test device is provided with a plurality of measuring positions along the axial direction, and a plurality of measuring points 9 with the same axial height are provided at each measuring position, and a thermocouple is provided at the measuring point, wherein the measuring point 9 between the inner copper tube 2 and the inner sleeve 3 is provided with an inner thermocouple, and the measuring point 9 between the outer sleeve 4 and the outer copper tube 6 is provided with an outer thermocouple, and the inner thermocouple and the outer thermocouple at the same measuring position are arranged in pairs along the radial direction. In a preferred embodiment, a plurality of pairs of thermocouples are evenly arranged circumferentially at the same measuring position, so as to effectively reduce the random error by taking the average value of the measurement results of the plurality of thermocouple pairs. In a further preferred embodiment, at least three measuring positions are provided along the axial direction.

[0070] The test device is also provided with an isolation box 11 to enclose the heating module, test pipe, insulation layer 7 and heat sink 8 in the isolation box and isolate them from the external environment, thereby reducing the impact of factors such as external temperature and airflow on the test results.

[0071] In a preferred embodiment, an infrared thermometer 12 is further provided in the isolation box 11 for assisting in temperature measurement in a non-contact manner.

[0072] Next, a measurement test was carried out using a solid cylindrical surface contact thermal resistance measurement device.

[0073] The tungsten wire is energized for heating, and the temperature distribution is obtained by measuring with thermocouples arranged at each measuring point 9, and the measurement results are averaged to obtain the average temperature T1 of the inner surface of the inner sleeve 3 and the average temperature T2 of the outer surface of the outer sleeve 4; the tungsten wire heating power Q is obtained according to the energized state of the tungsten wire; the heat flux q=(Q-Q') / A between the inner sleeve 3 and the outer sleeve 4 is calculated, wherein Q' is the power loss at both ends of the axial direction of the test device, and A is the outer surface area of ​​the inner copper tube 2; the contact thermal resistance R=(T1-T2) / q between the inner sleeve 3 and the outer sleeve 4 is calculated.

[0074] In a preferred embodiment, a calibration test is first performed before performing a measurement test.

[0075] The calibration test uses a calibration sample to replace the inner sleeve 3 and the outer sleeve 4. The wall thickness of the calibration sample is the same as the material of the test pipe, and the wall thickness is equal to the sum of the wall thickness of the inner sleeve 3 and the outer sleeve 4. The calibration test device is assembled by replacing the test pipe with the calibration sample.

[0076] The calibration sample is heated by the heating module, and the temperature of each part of the calibration sample is measured by the thermocouples arranged at each measuring point 9, and the average temperature of the inner surface and the outer surface of the calibration sample is calculated, and the thermal conductivity of the calibration sample is calculated according to the measurement results to obtain the test thermal conductivity. The test thermal conductivity is compared with the standard thermal conductivity of the calibration sample material. In a preferred embodiment, when the difference between the test thermal conductivity and the standard thermal conductivity is small, for example, Figure 2 As shown, when it is less than 10%, no correction is required; and when it exceeds 10%, correction can be made using a correction factor.

[0077] In some embodiments, the power loss Q' can be calculated by setting thermocouples at the base 10 and the top of the carbon rod to measure the temperature.

[0078] In a preferred embodiment, the measurement can be performed by a calibration test device.

[0079] Specifically, the temperatures measured by the two inner thermocouples and the outer thermocouple arranged radially in pairs on the surface of the calibration sample are t1 and t2 respectively. According to Fourier's law of heat conduction, the heat flux q1 on this section can be calculated; the heat flux q2, q3…q n , then the difference between the heating power Q of the heating module and the radial heat flux is the heat flux loss Q' at both ends of the axial direction, that is, Q' = Q-(q1+q2+…q n ) / n.

[0080] Compared with the existing technical solutions, the technical solutions provided in the above embodiments have the following advantages:

[0081] (1) It can realize the steady-state and refined measurement of the contact thermal resistance of the cylindrical surface.

[0082] (2) The ambient temperature of the sample can reach 900℃.

[0083] (3) The test device operates in a closed environment, which can realize the effect of different interface filling gases on thermal resistance.

[0084] (4) Use an infrared thermal imager to observe the temperature field distribution on the end face of the casing through a visualization window.

[0085] (5) Collect temperature at multiple measuring points and correct each other to reduce test errors.

[0086] The purpose of the above embodiments is to further explain the present invention in detail in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, the optimization or equivalent replacement of the structures or method steps involved, and the combination of implementation methods in different embodiments without conflict of structure and principle, all fall within the protection scope of the present invention.

Claims

1. A method for measuring contact thermal resistance of a solid cylindrical surface, characterized in that: The following steps are involved: Step a): a carbon rod wrapped with tungsten wire is provided, and an inner copper tube is arranged outside the carbon rod as a heating module; a test pipe is provided, the test pipe comprises a nested outer sleeve and an inner sleeve, the test pipe is sleeved outside the heating module, and an outer copper tube is sleeved outside the test pipe to obtain a thermal resistance measurement test device; The thermal resistance measurement test device is provided with a plurality of temperature measurement positions in the axial direction, and at each of the temperature measurement positions, a thermocouple is provided between the outer copper tube and the test tube and between the test tube and the inner copper tube; Step b): using the heating module to heat the test pipe and obtain the heating power Q; obtaining the power loss Q' at both ends of the axial direction of the thermal resistance measurement test device, and calculating the heat flow from the heating module to the test pipe as q = (Q-Q') / A, where A is the outer surface area of ​​the inner copper tube; The average temperature T1 of the inner surface of the inner sleeve and the average temperature T2 of the outer surface of the outer sleeve are measured and calculated by the thermocouple, and the interface thermal resistance R=(T1-T2) / q between the inner sleeve and the outer sleeve is calculated.

2. The method for measuring contact thermal resistance of a solid cylindrical surface according to claim 1, characterized in that: The step a) further includes the step of filling the gap between the inner sleeve and the outer sleeve with gas or solid medium.

3. The method for measuring the contact thermal resistance of a solid cylindrical surface according to claim 1 or 2, characterized in that: In the step a), at least three temperature measuring positions are provided, and a plurality of thermocouples are evenly arranged circumferentially on each temperature measuring position.

4. The method for measuring the contact thermal resistance of a solid cylindrical surface according to claim 1 or 2, characterized in that: Before performing step b), a calibration test is also included, and the calibration test includes the following steps: Providing a calibration sample, wherein the calibration sample is made of the same material as the test pipe fitting, and the wall thickness of the calibration sample is the same as the sum of the wall thicknesses of the outer sleeve and the inner sleeve; Substituting the calibration sample for the test pipe in the thermal resistance measurement test device to obtain a calibration test device; The calibration sample is heated by the heating module, and the average temperatures of the inner surface and the outer surface of the calibration sample are respectively measured and calculated to obtain the test thermal conductivity of the calibration sample; The test thermal conductivity is compared with the standard thermal conductivity of the material of the calibration sample, and when the difference between the test thermal conductivity and the standard thermal conductivity exceeds a given threshold, the test thermal conductivity is corrected by a correction coefficient.

5. The method for measuring contact thermal resistance of a solid cylindrical surface according to claim 4, characterized in that: In the step b), the method for obtaining the power loss Q' is: The calibration test device is used to measure and calculate the radial heat flux of the calibration test piece using the thermocouple, and the axial heat flux loss Q' is determined according to the difference between the output power of the heating module and the radial heat flux.

6. The method for measuring contact thermal resistance of a solid cylindrical surface according to claim 1, characterized in that: The step b) is carried out in a closed test box.

7. The method for measuring contact thermal resistance of a solid cylindrical surface according to claim 1, characterized in that: In the step b), the heating temperature does not exceed 900°C.

8. A solid cylindrical surface contact thermal resistance measuring device, characterized in that: A method for measuring the contact thermal resistance of a solid cylindrical surface according to any one of claims 1 to 7, comprising: A heating module, wherein the heating module comprises a carbon rod, a tungsten wire and an inner copper tube, wherein the carbon rod is arranged vertically, the tungsten wire is wound around the carbon rod, and the inner copper tube is sleeved on the outer side of the carbon rod; A test pipe, the test pipe comprising an inner sleeve and an outer sleeve of equal length, the inner sleeve is nested in the outer sleeve, and a measurement interface is formed between the inner sleeve and the outer sleeve; A heat insulation module, the heat insulation module comprising an outer copper tube and a heat insulation layer, the outer copper tube is sleeved outside the test tube, and the heat insulation layer covers the outer copper tube from the outside; A measuring module, wherein the measuring module comprises a plurality of axially arranged thermocouples, wherein the thermocouples comprise an inner thermocouple arranged between the test tube and the inner copper tube and an outer thermocouple arranged between the test tube and the outer copper tube, and each axial position where a thermocouple is arranged is provided with the inner thermocouple and the outer thermocouple arranged in pairs along the radial direction.

9. The solid cylindrical surface contact thermal resistance measuring device according to claim 8, characterized in that: It also includes a cooling module, which is configured as a heat sink and is arranged outside the thermal insulation module.

10. The solid cylindrical surface contact thermal resistance measuring device according to claim 8, characterized in that: It also includes an isolation box, in which an isolation environment is formed to isolate the heating module, the test tube, and the thermal insulation module from the external environment.

11. The solid cylindrical surface contact thermal resistance measuring device according to claim 10, characterized in that: The measuring module also includes an infrared temperature measuring device, which is arranged in the isolation box and measures the end surface temperature of the test pipe in a non-contact manner.

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