Integrated test system and method for high-temperature liquid metal convective heat transfer coefficient

Abstract

The application provides a high-temperature liquid metal convection heat exchange coefficient integrated testing system and method, which comprises a gas cylinder, a glove box, a high-temperature heater, a convection heat exchange coefficient testing circulation system, a vacuum pumping system, a data acquisition system and a data processing system, wherein the convection heat exchange coefficient testing circulation system comprises a thermostat, pipeline five, a liquid metal electromagnetic pump, pipeline eight, an electromagnetic flowmeter, pipeline nine, a convection heat exchanger and pipeline four; the glove box is internally provided with a liquid metal storage tank, a precision balance and a liquid metal mixing tank; the inlet and outlet of the convection heat exchanger are respectively provided with an inlet thermocouple and an outlet thermocouple; the inlet and outlet of the outer wall of the convection heat exchanger pipeline are respectively provided with thermocouples; and the outer wall surface of the convection heat exchanger is wrapped with the high-temperature heater. The application can complete the whole process of high-temperature liquid metal storage, configuration, purification, transportation, circulation testing, recovery and post-processing, and safely and accurately realizes the determination of the high-temperature liquid metal convection heat exchange coefficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid metal convective heat transfer coefficient research, in particular, especially relates to a high-temperature liquid metal convective heat transfer coefficient integrated test system and method. BACKGROUND

[0002] In recent years, liquid metals are used for hardware cooling in many engineering systems due to their superior performance. Compared with traditional non-liquid metal fluids represented by water, the main advantages of liquid metals are high thermal conductivity, low viscosity, high boiling point, strong solid-liquid phase conversion ability, etc. At present, liquid metals have been applied to chip cooling, high-power LED lamp cooling, power battery pack cooling and other fields.

[0003] Compared with traditional non-liquid metal fluids represented by water, the convective heat transfer coefficient of liquid metal has an order of magnitude advantage, and the determination and calculation of the convective heat transfer coefficient of liquid metal is the basis for enhanced convective heat transfer. At present, the research on convective heat transfer coefficient mainly focuses on fluids such as water and heat-conducting oil, and the working temperature is lower than 200℃ and the heat flux density is lower than 100W / cm 2 . It cannot meet the requirements of convective heat transfer under high temperature and high heat flux conditions. Since the Prandtl number of liquid metal is generally lower than 0.02, and the Prandtl number decreases with the increase of temperature, the current fluid convective heat transfer coefficient correlation cannot be applied to liquid metal. The determination of the convective heat transfer coefficient of liquid metal is mainly concentrated on the cooling of gallium-indium-tin alloy at room temperature, and for high-temperature liquid metals such as sodium, potassium and rubidium that can be applied in environments exceeding 500℃ and heat flux density exceeding 100W / cm 2 , their chemical properties are very active and easy to oxidize, and they react violently with water and oxygen, and are easy to burn and even explode. There are great difficulties in storage, handling and recovery. The determination conditions of the convective heat transfer coefficient are harsh, and the current convective heat transfer device cannot meet the determination requirements, and there is a lack of safe, reliable and accurate integrated determination system and method. SUMMARY

[0004] In view of the technical problem of the current convective heat transfer device being unable to meet the determination requirements of the convective heat transfer coefficient of liquid metal, a high-temperature liquid metal convective heat transfer coefficient integrated test system and method are provided.

[0005] The technical means adopted by the present application are as follows:

[0006] The application discloses a high-temperature liquid metal convection heat exchange coefficient integrated test system, which comprises a gas cylinder, a glove box, a high-temperature heater, a convection heat exchange coefficient test circulating system, a vacuumizing system, a data acquisition system and a data processing system, wherein the convection heat exchange coefficient test circulating system comprises a constant-temperature tank, pipeline five, a liquid metal electromagnetic pump, pipeline eight, an electromagnetic flowmeter, pipeline nine, a convection heat exchange device and pipeline four; the vacuumizing system is connected with the constant-temperature tank and used for vacuumizing the test system.

[0007] The gas cylinder is connected with the glove box in a sealing mode through pipeline one and is connected with the constant-temperature tank through pipeline three, and is used for supplying gas to the test system.

[0008] The glove box is internally provided with a liquid metal storage tank, a precision balance and a liquid metal mixing tank; the liquid metal storage tank is used for storing liquid metal before treatment; the precision balance is used for weighing the liquid metal; the liquid metal mixing tank is used for storing liquid metal after treatment and is connected with the constant-temperature tank through pipeline two.

[0009] The constant-temperature tank is used for storing liquid metal required for testing and heating or cooling the liquid metal; the constant-temperature tank is connected with the liquid metal electromagnetic pump through pipeline five; the pipeline five extends into the bottom of the constant-temperature tank; the liquid metal electromagnetic pump is used for pumping liquid metal required in the test process and is connected with the electromagnetic flowmeter through pipeline eight; the electromagnetic flowmeter is used for measuring the flow in the pipeline and is connected with the convection heat exchange device through pipeline nine; the convection heat exchange device is connected with the constant-temperature tank through pipeline four; the pipeline four extends into the bottom of the constant-temperature tank.

[0010] At least one inlet thermocouple and outlet thermocouple are respectively arranged at the inlet and outlet of the convection heat exchange device and used for measuring the temperature of the liquid metal flowing in the pipeline; at least one thermocouple is arranged at the inlet and outlet of the outer wall of the pipeline of the convection heat exchange device; the outer wall of the convection heat exchange device is wrapped with the high-temperature heater; and the high-temperature heater is used for heating the convection heat exchange device.

[0011] The liquid metal electromagnetic pump, the electromagnetic flowmeter, the inlet thermocouple, the outlet thermocouple and the thermocouple arranged at the outer wall of the pipeline of the convection heat exchange device are connected with the data acquisition system; the data acquisition system is connected with the data processing system and is used for acquiring the flow, temperature and pipeline temperature data of the liquid metal in the test process and transmitting the acquired data to the data processing system.

[0012] Further, the vacuumizing system comprises pipeline six, a cold trap, pipeline seven, a vacuum gauge and a molecular pump unit; one end of the pipeline six is connected with the pipeline five, the other end is connected with the molecular pump unit through the pipeline seven; the molecular pump unit is used for vacuumizing the test system, and the maximum vacuum degree is less than 10 -5Pa; the cold trap is a low-temperature container connected at the joint of pipeline six and pipeline seven, used for protecting the vacuum gauge and the molecular pump unit from water vapor or impurities during the vacuumizing process; the vacuum gauge is installed on pipeline seven, used for measuring the vacuum degree of the test system;

[0013] The test system further comprises a plurality of vacuum valves, pipeline two is a metal hose, at least one vacuum valve one is installed on pipeline two, at least one vacuum valve two is installed on pipeline three, at least one vacuum valve three is installed on pipeline four, at least one vacuum valve four is installed on pipeline five, and at least one vacuum valve five is installed on pipeline six.

[0014] Further, the gas cylinder contains high-purity argon with a purity of more than 99.99%;

[0015] The glove box is a sealed shell structure, the inside of which is circulated and adsorbed by its own gas, and an inert gas environment is maintained, with a water and oxygen content of less than 0.1 ppm, so as to ensure that the liquid metal is not oxidized during processing and maintain the high purity of the liquid metal;

[0016] The glove box further comprises a magnetic stirrer and a heating tray, the magnetic stirrer is used to accelerate the mixing of liquid metal alloys or nanoparticles, and the heating tray is used to heat high-melting-point liquid metals, so that the liquid metals are melted and maintained in a liquid state, and the heating temperature is higher than 500 DEG C;

[0017] The constant-temperature tank is a sealed shell structure, which maintains the required temperature of the liquid metal through PID adjustment, and the temperature of the liquid metal in the tank reaches 800 DEG C at most;

[0018] The pumping flow of the liquid metal electromagnetic pump reaches 700 liters per hour at most, the internal liquid metal temperature reaches 1200 DEG C, and the pumping speed is adjusted by the liquid metal electromagnetic pump;

[0019] The maximum temperature of the liquid metal in the electromagnetic flowmeter is 850 DEG C;

[0020] Each pipeline and equipment in the convection heat exchange coefficient test circulating system is wrapped with aluminum silicate insulation cotton.

[0021] Further, the convection heat exchanger is a stainless steel pipe with smooth inner wall, and the inlet thermocouple and the outlet thermocouple both extend into the center position of the convection heat exchanger pipeline;

[0022] A high-temperature heat-conducting agent is coated between the inner surface of the high-temperature heater and the convection heat exchanger;

[0023] A plurality of carbon-silicon rods are uniformly inserted in the circumferential direction of the high-temperature heater, the outer wall of the high-temperature heater is provided with a heat insulation coating, and the heat insulation coating is wrapped with aluminum silicate insulation cotton.

[0024] Further, the liquid metal is a metal in liquid state at room temperature, or an alloy in liquid state at room temperature, or a high-temperature liquid metal element in solid state at room temperature and an alloy with various proportions thereof.

[0025] The metal in liquid state at room temperature is at least mercury, cesium or gallium, and the alloy in liquid state at room temperature is at least a gallium-indium-tin alloy; the high-temperature liquid metal element in solid state at room temperature and the alloy with various proportions thereof are at least one of sodium, potassium, rubidium, lithium, tin, bismuth or antimony, or an alloy composed of one or more thereof.

[0026] Further, the inner wall of each pipeline is a smooth surface, and the material is a high-temperature resistant metal, which is at least stainless steel 316L, stainless steel 310S or a nickel-based alloy; the connection mode of the pipeline and the equipment is flange connection or metal sleeve connection, etc., so as to ensure that the vacuum degree of the system is less than 10 Pa during the vacuumizing process. -3 Pa.

[0027] The application further provides a test method of the high-temperature liquid metal convection heat transfer coefficient integrated test system, which comprises the following steps:

[0028] S1, a pretreatment process: including the connection of each equipment in the test system, and the purification, weighing and preparation of the liquid metal working medium;

[0029] S11, first, connect each equipment and pipeline, and close the vacuum valves one, two, three, four and five;

[0030] S12, use the gas cylinder to supply gas to the glove box, open the circulating purification function of the glove box, so that the water and oxygen content in the box is less than 0.1 ppm, and maintain for at least 24 hours;

[0031] S13, place the liquid metal storage tank, magnetic stirrer, precision balance, heating tray and liquid metal mixing tank, etc. in the glove box, store the required liquid metal in the liquid metal storage tank, place the liquid metal mixing tank on the precision balance for skinning weighing, and then purify, weigh and prepare the liquid metal;

[0032] S2, a test process: including the change of the gas atmosphere in the test system, and the delivery and circulation test of the liquid metal;

[0033] S21, based on the active chemical properties of the high-temperature liquid metal, the liquid metal is easy to react with oxygen and water vapor in the air, so the gas atmosphere of the whole test system is changed before the test; after the pretreatment process is completed, the gas atmosphere of the pipeline and equipment of the system except the glove box is air, vacuum valves three, four and five are opened, the cold trap is filled with liquid nitrogen, and the ultra-low temperature state of the cold trap is maintained;

[0034] S22, open the molecular pump unit to vacuumize the system, the vacuum gauge shows less than 10 -3 Pa for one hour, then turn off the molecular pump unit; open the vacuum valve two, use the gas cylinder to supply gas to the test system, so that the system pipeline is full of inert gas; then close the vacuum valve two, open the molecular pump unit to vacuumize again;

[0035] S23, repeat step S22 three times, and finally the test system is in a vacuum state;

[0036] S24, close the vacuum valve two, vacuum valve three, vacuum valve four and vacuum valve five, complete the change of the gas atmosphere in the test system; at this time, the glove box is in a normal pressure inert gas atmosphere, and the constant temperature tank is in a vacuum state;

[0037] S25, open the vacuum valve one, the high-temperature liquid metal in the liquid metal mixing tank is sucked into the constant temperature tank under the action of the pressure difference between the glove box and the constant temperature tank, and the liquid level in the liquid metal mixing tank is higher than the inlet of the pipeline two, so that the inert gas cannot enter the constant temperature tank; then close the vacuum valve one, complete the transportation of the high-temperature liquid metal;

[0038] S26, cycle test process:

[0039] S261, first, open the heating function of the constant temperature tank to melt and preheat the high-temperature liquid metal, so that the high-temperature liquid metal remains in a liquid state; open the high-temperature heater to heat, so that the temperature of the thermocouple on the outer wall of the heat exchanger pipe reaches more than 800℃;

[0040] S262, then open the vacuum valve three and vacuum valve four, open the liquid metal electromagnetic pump, the liquid metal electromagnetic pump has self-suction capacity, the high-temperature liquid metal in the constant temperature tank is sucked into the heat exchanger under the action of the liquid metal electromagnetic pump, and finally returns to the constant temperature tank, forming a working cycle;

[0041] S263, at this time, the high-temperature heater maintains the heating state, and the constant temperature tank enters the cooling state, and finally the heat exchanger pipe reaches the preset temperature, and the heating and cooling are balanced, and at least one hour is maintained in the balanced state, and a group of experimental data is collected; the preset temperature is any temperature in the range from the melting point of the high-temperature liquid metal to 800℃ according to the experimental requirements, the preset temperature is adjusted by changing the heating power of the high-temperature heater, a plurality of experimental data is collected; by changing the volume flow of the liquid metal electromagnetic pump, the mass flow of the high-temperature liquid metal is controlled, by controlling the flow of the high-temperature liquid metal, a plurality of experimental data is collected; the collected experimental parameters include the volume flow in the balanced state, the thermocouple temperature on the outer wall of the heat exchanger pipe, the inlet thermocouple temperature and the outlet thermocouple temperature;

[0042] S3, post-processing process:

[0043] S31, after the data collection is completed, closing the vacuum valve four, the high temperature liquid metal in the counterflow heat exchanger and pipeline is returned to the constant temperature tank under the action of the liquid metal electromagnetic pump, then closing the vacuum valve three, the liquid metal electromagnetic pump and the high temperature heater; at this time, all the high temperature liquid metal is in the constant temperature tank, when the high temperature liquid metal in the constant temperature tank is cooled to 100℃, opening the vacuum valve two to supply gas to the constant temperature tank, at this time, the constant temperature tank is in a positive pressure inert gas atmosphere;

[0044] S32, then placing the liquid metal storage tank under the residual discharge port at the bottom of the constant temperature tank, opening the residual discharge port, the high temperature liquid metal in the constant temperature tank flows into the liquid metal storage tank under the action of the pressure difference and gravity, and the liquid metal storage tank is placed back into the glove box;

[0045] S33, finally, opening the vacuum valve three and the vacuum valve four to make the whole test system full of inert gas, closing the vacuum valve two to complete the post-processing process.

[0046] Further, in the step S13, for the liquid metal with a melting point lower than room temperature, after the oxide film and impurities formed on the surface of the liquid metal are sucked by the micro syringe, the bottom liquid is extracted by the syringe and put into the liquid metal mixing tank to complete the purification of the liquid metal, and finally the weighing is performed according to the requirement; for the high temperature liquid metal with a melting point higher than room temperature, the block solid is stored in the liquid metal storage tank, and the block solid is clamped out by the tweezers, after the surface oxide layer and impurities are removed in the glove box, the block solid is placed back into the liquid metal storage tank, the liquid metal storage tank is placed on the heating tray, the temperature of the heating tray is set to be higher than the melting point by 100℃ to melt the block solid, after the melting, the surface oxide film and impurities are sucked by the micro syringe, and the bottom liquid is extracted by the syringe and put into the liquid metal mixing tank to complete the purification of the high temperature liquid metal, and finally the weighing is performed according to the requirement; for the liquid metal alloy, the same number of liquid metal storage tanks and liquid metal mixing tanks are prepared according to the types of liquid metals in the alloy, the above-mentioned purification process is repeated, the weighing is performed according to the proportion and combined into one liquid metal mixing tank to complete the preparation of the liquid metal alloy.

[0047] In the step S25, for the high temperature liquid metal with a melting point higher than room temperature, the liquid metal mixing tank is placed on the heating tray, and the heating temperature of the heating tray is set to be higher than the melting point of the high temperature liquid metal by 150℃, after the high temperature liquid metal is completely melted, the vacuum valve one is opened to transport the high temperature liquid metal; for the normal temperature liquid metal with a melting point lower than room temperature, the heating tray is not needed to be used for heating.

[0048] Further, the convective heat transfer coefficient of the liquid metal nanofluid after adding various types and proportions of nanoparticles in the liquid metal can be measured. The nanoparticles do not denature and do not react with the liquid metal in the measurement temperature range. The highest measurement temperature is 800℃ and lower than the smaller value of 50℃ lower than the boiling point of the measured liquid metal. The measurement temperature is the temperature measured by the outlet thermocouple.

[0049] The preparation method of the nanofluid is as follows:

[0050] First, the required nanoparticles are placed in a glove box and dried on a heating tray for at least 24 hours at a temperature of 100℃. The anhydrous and oxygen-free environment in the glove box is used to ensure that the nanoparticles are not oxidized during the drying process. A magnetic stirrer is placed on a precision balance for skinning and weighing. A syringe is used to extract the required pure liquid metal from the bottom of the liquid metal storage tank and place it in the magnetic stirrer. The mass of the liquid metal is weighed. The mass of the required nanoparticles is calculated, which is 0.1% to 2.5% of the mass of the liquid metal. The required nanoparticles are weighed on a precision balance and added to the magnetic stirrer. The magnetic stirrer is started to mix and stir the liquid metal and nanoparticles. To prevent overheating during stirring, the speed is lower than 200 revolutions per minute, and the stirring time is not less than 12 hours. The stirred fluid is the required nanofluid.

[0051] Further, the calculation method of the convective heat transfer coefficient of the high-temperature liquid metal is as follows:

[0052] First, the heating power output by the high-temperature heater to the convective heat exchanger is calculated Q :

[0053] ;

[0054] ;

[0055] In the formula, is the mass flow rate of the high-temperature liquid metal, is the specific heat capacity at constant pressure of the high-temperature liquid metal, is the density of the high-temperature liquid metal, is the temperature measured by the outlet thermocouple, is the temperature measured by the inlet thermocouple, is the volume flow rate of the high-temperature liquid metal. The above properties are the values when the temperature of the high-temperature liquid metal is ;

[0056] By measuring the temperatures of the thermocouples at the inlet and outlet of the outer wall of the convective heat exchanger, the temperatures at the inlet and outlet of the inner wall of the convective heat exchanger are obtained:

[0057] ;

[0058] ;

[0059] In the formula, This refers to the temperature at the inlet of the convection heat exchanger's inner wall. Temperature at the inlet of the convection heat exchanger outer wall The wall thickness of the convection heat exchanger. The thermal conductivity of the material used in the convection heat exchanger. This refers to the temperature at the outlet of the convection heat exchanger's inner wall. Temperature at the outlet of the outer wall of the convection heat exchanger;

[0060] The convective heat transfer coefficient of high-temperature liquid metals satisfies the following formula:

[0061] ;

[0062] ;

[0063] ;

[0064] In the formula, The convective heat transfer coefficient of high-temperature liquid metal. The heat transfer area of ​​the convection heat exchanger. The average temperature difference between the high-temperature liquid metal and the inner wall of the convection heat exchanger. The inner diameter of the convection heat exchanger. The effective length of the convection heat exchanger;

[0065] Fitting the correlation of high-temperature liquid metal convective heat transfer coefficient:

[0066] High-temperature liquid metal convective heat transfer coefficient and It relates to the dimensionless Petre number (Pe) in heat transfer, where the Petre number is the product of the Reynolds number (Re) and the Prandtl number (Pr), and satisfies the following formula:

[0067] ;

[0068] ;

[0069] ;

[0070] In the formula, The flow rate of the high-temperature liquid metal. The viscosity of a high-temperature liquid metal. The above property represents the thermal conductivity of a high-temperature liquid metal, where the temperature of the liquid metal is... The value at that time;

[0071] Flow rate of high-temperature liquid metal Satisfy the following formula:

[0072] ;

[0073] The correlation formula of the high-temperature liquid metal convective heat transfer coefficient satisfies the following formula:

[0074] ;

[0075] In the formula, a, b, c and d are constants, b and c are powers of Re and Pe respectively;

[0076] The correlation formula of the high-temperature liquid metal convective heat transfer coefficient is effective when the average error between the experimental value and the predicted value is less than 5%.

[0077] Compared with the prior art, the present application has the following advantages:

[0078] 1. The high-temperature liquid metal convective heat transfer coefficient integrated test system and method provided by the present application can measure liquid metals including mercury, cesium, gallium and other metals that are liquid at room temperature, including gallium-indium-tin alloy and other alloys that are liquid at room temperature. It also includes sodium, potassium, rubidium, lithium, tin, bismuth, antimony and other high-temperature liquid metal elements that are solid at room temperature and their alloys in various proportions. This greatly increases the types of liquid metals that are difficult to measure by current technology, and also increases the measurement temperature, with a maximum temperature of 800℃, which is much higher than the fluid use temperature in current technology.

[0079] 2. The high-temperature liquid metal convective heat transfer coefficient integrated test system and method provided by the present application can measure the convective heat transfer coefficient of liquid metal nanofluid after adding various types and proportions of nanoparticles to the above high-temperature liquid metal, and realize quantitative addition of nanoparticles in a glove box to complete the configuration of nanofluid, laying a foundation for improving the convective heat transfer coefficient of liquid metal.

[0080] 3. Compared with the prior art, the high-temperature liquid metal convective heat transfer coefficient integrated test system of the present application not only provides a test device, but also ensures that the entire test process is water-free, oxygen-free and dust-free, meeting the full-process measurement operation of flammable, explosive and oxidizable liquid metals applied in high-temperature and high-heat flow environments, including all processes of liquid metal storage, configuration, purification, transportation, circulation test, recovery and post-processing, ensuring that the entire process is operated in a sealed shell without contact with the outside world, and the liquid metal after testing does not remain in the system, the gas atmosphere in the entire process is converted in an inert gas and vacuum environment, and the complete liquid metal pretreatment, test and post-processing process can be realized, improving safety and reliability.

[0081] ​4、The prior art in the process of measuring the convective heat transfer coefficient, the heating power of the test part is the input electric power of the heater, and the heater itself has a large amount of heat leakage to the environment, and this part of the measurement has errors, especially under high temperature conditions exceeding 500 DEG C, the heat leakage increases, and the measurement error increases. The present application measures the flow of high-temperature liquid metal and the temperature difference between the inlet and outlet of the convective heat exchanger, and the heat absorbed by the high-temperature liquid metal is used as the heating power, so that the heating power can be accurately measured, the error caused by heat leakage is avoided, and the accuracy of the convective heat transfer coefficient is improved.

[0082] 5、The present application considers the length, pipe diameter, liquid metal density, viscosity, flow rate, thermal conductivity and other factors of the convective heat exchanger according to the measured convective heat transfer coefficient of high-temperature liquid metal, and the convective heat transfer coefficient of high-temperature liquid metal can be fully fitted according to the high-temperature liquid metal convective heat transfer coefficient test method provided by the present application, and the high-temperature liquid metal convective heat transfer coefficient calculation correlation is systematically improved.

[0083] In summary, the technical scheme of the present application can solve the problem that the current convective heat exchange device cannot meet the requirements of liquid metal convective heat transfer coefficient measurement.

[0084] Based on the above reasons, the present application can be widely used in the field of liquid metal convective heat transfer coefficient research. BRIEF DESCRIPTION OF DRAWINGS

[0085] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the drawings needed in the embodiment or prior art description will be briefly introduced below, and obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0086] Figure 1 The present application is a test system schematic diagram.

[0087] Figure 2 The present application is a cross-sectional view of the convective heat exchanger.

[0088] In the figure: 1, gas cylinder; 2, glove box; 3, liquid metal storage tank; 4, magnetic stirrer; 5, precision balance; 6, heating tray; 7, liquid metal mixing tank; 8, constant temperature tank; 9, cold trap; 10, vacuum gauge; 11, molecular pump unit; 12, liquid metal electromagnetic pump; 13, electromagnetic flowmeter; 14, inlet thermocouple; 15, convection heat exchanger; 16, high temperature heater; 17, outlet thermocouple; 18, data acquisition system; 19, data processing system; 21, pipeline one; 22, pipeline two; 23, pipeline three; 24, pipeline four; 25, pipeline five; 26, pipeline six; 27, pipeline seven; 28, pipeline eight; 29, pipeline nine; 31, vacuum valve one; 32, vacuum valve two; 33, vacuum valve three; 34, vacuum valve four; 35, vacuum valve five; 36, high temperature heat conduction agent; 37, carbon-silicon rod; 38, heat insulation coating; 39, thermal insulation cotton. DETAILED DESCRIPTION

[0089] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0090] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0091] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0092] The foregoing merely illustrates the principles of the application. Various modifications and alterations to the methods and devices described herein will be apparent to those skilled in the art in view of the foregoing description. It will be appreciated that exchanges of signals between the various components of the system can be accomplished using any suitable communication medium, such as a wired or wireless communication medium. Moreover, the various components of the system can be implemented using any suitable hardware, software, firmware, or combination thereof. It is intended that all such alterations and modifications be considered as equivalents thereof. Thus, the above description is not intended to limit the scope of the application and many alternatives not explicitly described herein are encompassed by the scope of the application. The disclosure is not limited to the details given herein but can be practiced with variation of form and detail by those skilled in the art, without departing from the spirit or scope of the application. The scope of the application is, therefore, indicated by the appended claims, rather than being circumscribed by the foregoing description. In addition, various publications, patents, and published patent applications are cited or described in the foregoing description in order to more fully describe the state of the art to which the present application pertains. However, nothing in this description is to be construed as an admission that the present application is not entitled to antedate such publications, patents, and published patent applications, including any potential deficiencies thereof.

[0093] In the description of the present application, it is to be understood that the relative terms like "front", "back", "up", "down", "left", "right", "horizontal", "vertical", and "top", "bottom" are intended to indicate the orientation or position of the device or element as shown in the drawings, and are merely used for the purpose of convenience and simplification of the description, and do not indicate or imply that the device or element must have a particular orientation or be constructed and operated in a particular orientation, and therefore should not be construed as limiting the scope of the present application. The relative terms "inner", "outer" refer to the inner and outer sides relative to the outline of the respective components.

[0094] For the purpose of the description, spatially relative terms, such as "above", "below", "top", "bottom", "up", "down", "side", "higher", "lower", "vertical", "horizontal", and the like, can be used herein for the purpose of convenience in describing the present application as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the drawings. For example, if a device shown in the drawings is inverted, elements described as "above" or "up" other elements or structures would then be oriented "below" or "down" the other elements or structures. The exemplary term "above" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terms "first", "second", and the like, as used herein do not have any specific meaning and are used only for the purpose of distinguishing between different components.

[0095] It is to be understood that the use of the terms "first", "second", etc., to describe various components in the examples described herein are used only for the purpose of distinguishing between different components, and are not intended to limit the scope of the present application. Thus, the terms "first", "second", etc., are not intended to denote a particular order or sequence.

[0096] To solve the existing problems, such asFigures 1-2 As shown, the application provides a high-temperature liquid metal convection heat transfer coefficient integrated test system and method. The determination of the convection heat transfer coefficient of various high-temperature liquid metals and their alloys, such as sodium, potassium, rubidium, cesium, sodium-potassium alloy, rubidium-cesium alloy, and other flammable, explosive, and oxidizable liquid metals, can be achieved. The test temperature can reach 800℃. Through the integrated test system, the entire process of high-temperature liquid metal storage, configuration, purification, transportation, circulation test, recovery, and post-processing can be completed, and the determination of the convection heat transfer coefficient of high-temperature liquid metal can be realized safely and accurately. Based on the measured data, a method for establishing a high-temperature liquid metal convection heat transfer coefficient calculation correlation is provided, which expands the application range of high-temperature liquid metal convection heat transfer coefficient and provides important technical support for solving the heat collection and distribution problems in high-temperature, high-heat flow environments such as solar power generation, spacecraft thermal control, liquid metal high-temperature pulsating heat pipe, and atomic energy heat dissipation.

[0097] The high-temperature liquid metal convection heat transfer coefficient integrated test system of the application comprises: a gas cylinder 1, a glove box 2, a liquid metal storage tank 3, a magnetic stirrer 4, a precision balance 5, a heating tray 6, a liquid metal mixing tank 7, a constant temperature tank 8, a cold trap 9, a vacuum gauge 10, a molecular pump unit 11, a liquid metal electromagnetic pump 12, an electromagnetic flowmeter 13, an inlet thermocouple 14, a convection heat exchanger 15, a high-temperature heater 16, an outlet thermocouple 17, a data acquisition system 18, a data processing system 19, a pipeline 1 21, a pipeline 2 22, a pipeline 3 23, a pipeline 4 24, a pipeline 5 25, a pipeline 6 26, a pipeline 7 27, a pipeline 8 28, a pipeline 9 29, a vacuum valve 1 31, a vacuum valve 2 32, a vacuum valve 3 33, a vacuum valve 4 34, and a vacuum valve 5 35.

[0098] The connection mode is that the high-purity argon gas with a purity of more than 99.99% in the gas cylinder 1 is connected with the glove box 2 through the pipeline 21, and the gas cylinder 1 is also connected with the constant-temperature tank 8 through the pipeline 3 23 for supplying gas to the test system, wherein the vacuum valve 2 32 is installed on the pipeline 3 23, and the vacuum valve 2 32 is used for controlling the connection between the gas cylinder 1 and the constant-temperature tank 8. The glove box 2 is a sealed shell structure, and the inside is circulated and adsorbed by the gas itself, and the inert gas environment can be maintained inside, and the water and oxygen content is less than 0.1 ppm, so that the liquid metal is not oxidized during the processing process, and the high purity of the liquid metal is maintained. The liquid metal storage tank 3, the magnetic stirrer 4, the precision balance 5, the heating tray 6 and the liquid metal mixing tank 7 are placed in the glove box 2, which are used for the processing steps such as purification, weighing and configuration of the liquid metal, wherein the liquid metal storage tank 3 is used for storing the liquid metal before processing; the magnetic stirrer 4 is used for accelerating the mixing of the liquid metal alloy or nanoparticles; the precision balance 5 is used for weighing the liquid metal; the heating tray 6 is used for heating the liquid metal with a high melting point, so that it is melted and maintained in a liquid state, and the heating temperature is higher than 500 DEG C; the liquid metal mixing tank 7 is placed in the glove box 2 and is used for storing the liquid metal after processing. The liquid metal mixing tank 7 is connected with the constant-temperature tank 8 through the pipeline 2 22, wherein the vacuum valve 1 31 is installed on the pipeline 2 22, the pipeline 2 22 is a metal hose, and the vacuum valve 1 31 is used for controlling the connection between the liquid metal mixing tank 7 and the constant-temperature tank 8. The constant-temperature tank 8 is a sealed shell structure, which is used for storing the liquid metal required for testing, and can heat or cool the liquid metal, and maintain the required temperature of the liquid metal through PID adjustment, and the temperature of the liquid metal in the tank can reach 800 DEG C at most. The constant-temperature tank 8 is connected with the liquid metal electromagnetic pump 12 through the pipeline 5 25, wherein the vacuum valve 4 34 is installed on the pipeline 5 25, the vacuum valve 4 34 is used for controlling the connection between the constant-temperature tank 8 and the liquid metal electromagnetic pump 12, and the pipeline 5 25 extends into the bottom of the constant-temperature tank 8. The pipeline 5 25 is connected with the molecular pump unit 11 through the pipeline 6 26, the cold trap 9 and the pipeline 7 27 in sequence, wherein the vacuum valve 5 35 is installed on the pipeline 6 26, and the vacuum valve 5 35 is used for controlling the connection between the pipeline 5 25 and the molecular pump unit 11. The vacuum gauge 10 is installed on the pipeline 7 27, and the vacuum gauge 10 is used for measuring the vacuum degree of the system. The pipeline 6 26, the cold trap 9, the pipeline 7 27, the vacuum gauge 10 and the molecular pump unit 11 form an evacuation system, wherein the cold trap 9 is a low-temperature container, which is used for protecting the vacuum gauge 10 and the molecular pump unit 11 from absorbing water vapor or impurities during the evacuation process, the vacuum gauge 10 is used for displaying the current vacuum degree of the system, and the molecular pump unit 11 is used for evacuating the system, and the maximum vacuum degree can be less than 10 -5Pa. The liquid metal electromagnetic pump 12 is used to pump the liquid metal required in the test process, with a flow rate of up to 700 liters per hour and a temperature of up to 1200°C, and the pumping speed can be adjusted by the liquid metal electromagnetic pump 12. The liquid metal electromagnetic pump 12 is connected to the electromagnetic flowmeter 13 through pipeline eight 28, and the electromagnetic flowmeter 13 is used to measure the flow rate in the pipeline, with a maximum temperature of 850°C. The electromagnetic flowmeter 13 is connected to the counterflow heat exchanger 15 through pipeline nine 29, and the counterflow heat exchanger 15 is a stainless steel tube with a smooth inner wall. The inlet and outlet of the counterflow heat exchanger 15 are respectively provided with an inlet thermocouple 14 and an outlet thermocouple 17, both of which extend into the center of the pipeline of the counterflow heat exchanger 15, and are used to measure the temperature of the liquid metal flowing in the pipeline. The inlet and outlet of the outer wall of the pipeline of the counterflow heat exchanger 15 are respectively provided with thermocouples. The outer wall of the counterflow heat exchanger 15 is wrapped with a high-temperature heater 16, which is used to heat the counterflow heat exchanger 15. The counterflow heat exchanger 15 is connected to the constant-temperature tank 8 through pipeline four 24, and a vacuum valve three 33 is installed on pipeline four 24, which is used to control the connection between the counterflow heat exchanger 15 and the constant-temperature tank 8. Pipeline four 24 extends into the bottom of the constant-temperature tank 8. The constant-temperature tank 8, the vacuum valve four 34, the pipeline five 25, the liquid metal electromagnetic pump 12, the pipeline eight 28, the electromagnetic flowmeter 13, the pipeline nine 29, the counterflow heat exchanger 15, the pipeline four 24 and the vacuum valve three 33 form a counterflow heat exchange coefficient test circulating system. The pipelines and equipment of the circulating system are wrapped with aluminum silicate insulation cotton to reduce heat loss during circulation. The data acquisition system 18 is connected to the liquid metal electromagnetic pump 12, the electromagnetic flowmeter 13, the inlet thermocouple 14, the outlet thermocouple 17 and the pipeline outer wall thermocouples of the counterflow heat exchanger 15 through signals, and collects data such as the flow rate, temperature and pipeline temperature of the liquid metal during the test. The collected data is transmitted to the data processing system 19 through signals.

[0099] The test method of the high-temperature liquid metal counterflow heat exchange coefficient integrated test system of the application comprises the following steps:

[0100] I. Pretreatment process: including system connection, and purification, weighing and preparation of liquid metal working medium.

[0101] First, the device and pipeline are connected according to the test system schematic diagram and the above description, and vacuum valve one 31, vacuum valve two 32, vacuum valve three 33, vacuum valve four 34 and vacuum valve five 35 are closed. Use gas cylinder 1 to supply gas to glove box 2, open the circulation purification function of glove box 2, so that the water and oxygen content in the box is less than 0.1 ppm, and maintain at least 24 hours. Further, liquid metal storage tank 3, magnetic stirrer 4, precision balance 5, heating tray 6 and liquid metal mixing tank 7 are placed in glove box 2, and liquid metal storage tank 3 stores the required liquid metal. Liquid metal mixing tank 7 is placed on precision balance 5 for skinning weighing. High-temperature liquid metal has active chemical properties, and after a long time, an oxide film will form on the surface of the liquid metal in the liquid metal storage tank 3. Due to surface tension, the oxide film adheres to the upper layer of the liquid metal. Therefore, for liquid metals with a melting point below room temperature, after removing the surface oxide film and impurities using a micro syringe, the bottom liquid is extracted into liquid metal mixing tank 7 using a syringe, completing the purification of the liquid metal, and finally weighing according to the needs. For high-temperature liquid metals with a melting point higher than room temperature, the liquid metal is stored in the form of a block in liquid metal storage tank 3. When used, the block is removed with tweezers, and the surface oxide layer and impurities are removed in glove box 2, and then placed back into liquid metal storage tank 3. Liquid metal storage tank 3 is placed on heating tray 6, and the temperature of heating tray 6 is set to be 100°C higher than the melting point to melt the block. After melting, the surface oxide film and impurities are removed using a micro syringe, and then the bottom liquid is extracted into liquid metal mixing tank 7 using a syringe, completing the purification of the high-temperature liquid metal. Finally, weighing according to the needs. For liquid metal alloys, prepare the same number of liquid metal storage tanks and liquid metal mixing tanks according to the types of liquid metals in the alloy, repeat the above purification process, weigh according to the proportion and combine into one liquid metal mixing tank 7, complete the preparation of the liquid metal alloy.

[0102] II. Test procedure: including the change of gas atmosphere in the system, and the delivery and circulation test of liquid metal.

[0103] Due to the active chemical properties of high-temperature liquid metal, it is easy to react with oxygen and water vapor in the air, so before testing, the gas atmosphere of the whole test system needs to be changed. After the pretreatment process is completed, the gas atmosphere of the system pipeline and equipment except glove box 2 is air, vacuum valve three 33, vacuum valve four 34 and vacuum valve five 35 are opened, liquid nitrogen is filled in cold trap 9, and the ultra-low temperature state of cold trap 9 is maintained. Open molecular pump unit 11 to vacuum the system, and the vacuum gauge 10 shows a value less than 10 -3After one hour, the molecular pump unit 11 is turned off. The vacuum valve two 32 is opened, and the system is supplied with gas from the gas cylinder 1, so that the system pipeline is filled with inert gas. Then the vacuum valve two 32 is closed, and the molecular pump unit 11 is turned on again to vacuumize, and this process of filling with inert gas and vacuumizing is repeated three times, and finally the system is kept in a vacuum state. The vacuum valve two 32, the vacuum valve three 33, the vacuum valve four 34 and the vacuum valve five 35 are closed, and the change of the gas atmosphere in the system is completed. At this time, the glove box 2 is in a normal pressure inert gas atmosphere, and the thermostat 8 is in a vacuum state.

[0104] For high-temperature liquid metal with a melting point higher than room temperature, the liquid metal mixing tank 7 needs to be placed on the heating tray 6, and the heating temperature of the heating tray 6 is set to be 150°C higher than the melting point of the high-temperature liquid metal. After the high-temperature liquid metal is completely melted, the vacuum valve one 31 is opened, and the high-temperature liquid metal in the liquid metal mixing tank 7 is sucked into the thermostat 8 under the pressure difference between the glove box 2 and the thermostat 8. During the suction process, the liquid level in the liquid metal mixing tank 7 is higher than the inlet of the pipeline two 22, so that inert gas cannot enter the inside of the thermostat 8. For normal temperature liquid metal with a melting point lower than room temperature, heating is not required by using the heating tray 6. Then the vacuum valve one 31 is closed, and the delivery of the high-temperature liquid metal is completed.

[0105] Circulation test procedure: First, the heating function of the thermostat 8 is turned on to melt and preheat the high-temperature liquid metal inside, so that the high-temperature liquid metal remains in a liquid state. The high-temperature heater 16 is turned on to heat, so that the temperature of the thermocouple on the outer wall of the pipeline of the convection heat exchanger 15 reaches above 800°C. Then the vacuum valve three 33 and the vacuum valve four 34 are opened, and the liquid metal electromagnetic pump 12 is turned on. The liquid metal electromagnetic pump 12 has self-suction capacity, and the high-temperature liquid metal in the thermostat 8 is sucked into the convection heat exchanger 15 under the action of the liquid metal electromagnetic pump 12, and finally returns to the inside of the thermostat 8, forming a working cycle. At this time, the high-temperature heater 16 is kept in a heating state, and the thermostat 8 is turned into a cooling state. Finally, after the temperature of the thermocouple on the outer wall of the pipeline of the convection heat exchanger 15 reaches the preset temperature, the heating and cooling are balanced, and the balance is maintained for at least one hour to complete the collection of a group of experimental data. The preset temperature is any temperature in the range from the melting point of the high-temperature liquid metal to 800°C according to experimental requirements. By changing the heating power of the high-temperature heater 16, the preset temperature can be adjusted, and multiple sets of experimental data can be collected. By changing the volume flow of the liquid metal electromagnetic pump 12, the mass flow of the high-temperature liquid metal can be controlled, and by controlling the flow of the high-temperature liquid metal, multiple sets of experimental data can be collected. The collected experimental parameters include the volume flow in the balanced state, the temperature of the thermocouple on the outer wall of the pipeline of the convection heat exchanger 15, the temperature of the inlet thermocouple 14, and the temperature of the outlet thermocouple 17.

[0106] Three, post-processing process:

[0107] After data acquisition, vacuum valve 34 is closed. The high-temperature liquid metal in the convection heat exchanger 15 and pipelines flows back to the constant temperature bath 8 under the action of the liquid metal electromagnetic pump 12. Then, vacuum valve 33, liquid metal electromagnetic pump 12, and high-temperature heater 16 are closed. At this time, all the high-temperature liquid metal is in the constant temperature bath 8. When the high-temperature liquid metal in the constant temperature bath 8 cools to its high-temperature melting point of 100°C, vacuum valve 32 is opened to supply gas to the constant temperature bath 8. At this time, the constant temperature bath 8 is in a positive pressure inert gas atmosphere. Then, the liquid metal storage tank 3 is placed under the drain port at the bottom of the constant temperature bath 8. The drain port is opened, and the high-temperature liquid metal in the constant temperature bath 8 flows into the liquid metal storage tank 3 under the action of pressure difference and gravity. The liquid metal storage tank 3 is then placed back into the glove box 2. Finally, vacuum valves 33 and 34 are opened to fill the entire system with inert gas, and vacuum valve 32 is closed, completing the processing.

[0108] Heat exchanger structure: such as Figure 2 As shown in the cross-sectional view of the convection heat exchanger, the innermost layer is the convection heat exchanger 15. A layer of high-temperature thermally conductive agent 36 is coated between the high-temperature heater 16 and the convection heat exchanger 15 to reduce the contact thermal resistance between them and enhance thermal efficiency. The high-temperature heater 16 is heated by uniformly inserted silicon carbide rods 37. The high-temperature heater 16 is insulated by a heat-insulating coating 38, and the heat-insulating coating 38 is wrapped with aluminum silicate insulation cotton 39 to further improve thermal efficiency and reduce heat loss.

[0109] Types of liquid metals tested in the high-temperature liquid metal convection heat transfer integrated system include metals that are liquid at room temperature, such as mercury, cesium, and gallium, as well as alloys that are liquid at room temperature, such as gallium-indium-tin alloys. It also includes high-temperature liquid metal elements that are solid at room temperature, such as sodium, potassium, rubidium, lithium, tin, bismuth, and antimony, and their alloys in various proportions. Furthermore, the system can measure the convective heat transfer coefficient of liquid metal nanofluids after adding various types and proportions of nanoparticles to the above-mentioned liquid metals. The nanoparticles do not denature or react with the liquid metal within the measurement temperature range. The highest measurement temperature is the smaller of 800℃ and 50℃ below the boiling point of the measured liquid metal. The measurement temperature is the temperature measured by outlet thermocouple 17.

[0110] Nanofluid preparation: first, the required nanoparticles are placed in the glove box 2, and dried for at least 24 hours on the heating tray 6, the temperature is 100℃, the anhydrous and oxygen-free environment in the glove box 2 ensures that the nanoparticles are not oxidized during the drying process. Further, the magnetic stirrer 4 is placed on the precision balance 5 for skinning weighing, the required pure liquid metal is extracted from the bottom of the liquid metal storage tank 3 using a syringe, and placed in the magnetic stirrer 4, and the mass of the liquid metal is weighed. Further, the required mass of the nanoparticles is calculated, the mass of the nanoparticles accounts for 0.1%~2.5% of the mass of the liquid metal, and the required nanoparticles are weighed on the precision balance 5, and the required nanoparticles are added to the magnetic stirrer 4. Start the magnetic stirrer 4 to mix and stir the liquid metal and the nanoparticles, in order to prevent overheating during stirring, the speed is lower than 200 revolutions per minute, and the stirring time is not less than 12 hours. The fluid after stirring is the required nanofluid.

[0111] Pipe: the material of the pipe in the high-temperature liquid metal convection heat exchange integrated test system is stainless steel 316L, stainless steel 310S, nickel-based alloy and other high-temperature resistant metals, and the inner wall of the pipe is smooth. The direct connection method of the pipe and the equipment includes flange connection, metal sleeve connection and the like, which ensures that the vacuum degree of the system is lower than 10 -3 Pa during the vacuumizing process.

[0112] Calculation of convection heat transfer coefficient:

[0113] First, calculate the heating power output by the high-temperature heater 16 to the convection heat exchanger 15:

[0114] ;

[0115] ;

[0116] In the formula, is the mass flow rate of the high-temperature liquid metal, is the specific heat capacity of the high-temperature liquid metal at constant pressure, is the density of the high-temperature liquid metal, is the temperature measured by the outlet thermocouple, is the temperature measured by the inlet thermocouple, is the volume flow rate of the high-temperature liquid metal, and the above-mentioned physical properties are the values when the temperature of the high-temperature liquid metal is .

[0117] By measuring the temperature of the thermocouples at the inlet and outlet of the outer wall of the convection heat exchanger 15, the temperature at the inlet and outlet of the inner wall of the convection heat exchanger 15 can be obtained:

[0118] ;

[0119] ;

[0120] wherein, is the temperature at the inlet of the inner wall of the convection heat exchanger, is the temperature at the inlet of the outer wall of the convection heat exchanger, is the wall thickness of the convection heat exchanger, is the thermal conductivity of the material used for the convection heat exchanger, is the temperature at the outlet of the inner wall of the convection heat exchanger, is the temperature at the outlet of the outer wall of the convection heat exchanger.

[0121] The convection heat exchange coefficient of the high-temperature liquid metal can be obtained by the following formula:

[0122] ;

[0123] ;

[0124] ;

[0125] wherein, is the convection heat exchange coefficient of the high-temperature liquid metal, is the heat exchange area of the convection heat exchanger, is the average temperature difference between the high-temperature liquid metal and the inner wall of the convection heat exchanger, is the inner diameter of the convection heat exchanger, is the effective length of the convection heat exchanger.

[0126] The correlation formula of the convection heat exchange coefficient of the high-temperature liquid metal is fitted as follows:

[0127] Since the Prandtl number of the liquid metal is generally lower than 0.02, and the Prandtl number decreases with the increase of the temperature, the current correlation formula of the fluid convection heat exchange coefficient cannot be applied to the liquid metal. Research shows that the convection heat exchange coefficient of the high-temperature liquid metal is related to the dimensionless number Peclet number Pe, wherein the Peclet number is the product of the Reynolds number Re and the Prandtl number Pr, and can be expressed by the following formula:

[0128] ;

[0129] ;

[0130] ; wherein,

[0131] is the flow rate of the high-temperature liquid metal, is the viscosity of the high-temperature liquid metal, is the thermal conductivity of the high-temperature liquid metal, and the above properties are the values of the high-temperature liquid metal at the temperature of

[0132] ​​Flow rate of high temperature liquid metal The flow rate of high temperature liquid metal can be calculated by the following formula:

[0133] ;

[0134] The correlation formula of convective heat transfer coefficient of high temperature liquid metal can be expressed by the following formula:

[0135] ;

[0136] In the formula, a, b, c and d are all constants, b and c are powers of Re and Pe respectively.

[0137] According to a plurality of sets of experimental data of convective heat transfer coefficient, the values of a, b, c and d can be fitted and calculated to obtain the correlation formula of convective heat transfer coefficient of high temperature liquid metal. The correlation formula of convective heat transfer coefficient of high temperature liquid metal is used to calculate the convective heat transfer coefficient of high temperature liquid metal. When the average error between the experimental value and the predicted value is less than 5%, the correlation formula of convective heat transfer coefficient of high temperature liquid metal is effective.

[0138] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.​

Claims

1. A high-temperature liquid metal convection heat transfer coefficient integrated test system, characterized in that, The utility model relates to a liquid metal heat transfer coefficient test system, which comprises a gas cylinder (1), a glove box (2), a high-temperature heater (16), a convection heat transfer coefficient test circulating system, a vacuumizing system, a data acquisition system (18) and a data processing system (19). The gas cylinder (1) is connected to the glove box (2) through a pipeline (21) and is connected to the constant-temperature tank (8) through a pipeline (23) to supply gas to the test system. The glove box (2) contains a liquid metal storage tank (3), a precision balance (5) and a liquid metal mixing tank (7). The liquid metal storage tank (3) is used to store liquid metal before processing, the precision balance (5) is used to weigh the liquid metal, and the liquid metal mixing tank (7) is used to store liquid metal after processing and is connected to the constant-temperature tank (8) through a pipeline (22). The constant-temperature tank (8) is used to store liquid metal required for testing and heat or cool the liquid metal. The constant-temperature tank (8) is connected to the liquid metal electromagnetic pump (12) through a pipeline (25) that extends into the bottom of the constant-temperature tank (8). The liquid metal electromagnetic pump (12) is used to pump liquid metal required in the test process and is connected to the electromagnetic flowmeter (13) through a pipeline (28). The electromagnetic flowmeter (13) is used to measure the flow rate in the pipeline and is connected to the convection heat transfer device (15) through a pipeline (29). The convection heat transfer device (15) is connected to the constant-temperature tank (8) through a pipeline (24) that extends into the bottom of the constant-temperature tank (8). The inlet and outlet of the convection heat transfer device (15) are respectively provided with at least one inlet thermocouple (14) and outlet thermocouple (17) for measuring the temperature of the liquid metal flowing in the pipeline. At least one thermocouple is arranged at the inlet and outlet of the outer wall of the pipeline of the convection heat transfer device (15). The outer wall of the convection heat transfer device (15) is wrapped with a high-temperature heater (16) for heating the convection heat transfer device (15). The liquid metal electromagnetic pump (12), electromagnetic flowmeter (13), inlet thermocouple (14), outlet thermocouple (17) and thermocouple arranged on the outer wall of the pipeline of the convection heat transfer device (15) are connected to the data acquisition system (18), and the data acquisition system (18) is connected to the data processing system (19) to acquire the flow rate, temperature and pipeline temperature data of the liquid metal in the test process and transmit the acquired data to the data processing system (19). ​ 2. The high temperature liquid metal convective heat transfer coefficient integrated test system of claim 1, wherein, The vacuum system comprises pipeline six (26), a cold trap (9), pipeline seven (27), a vacuum gauge (10) and a molecular pump unit (11), one end of the pipeline six (26) is connected with the pipeline five (25), the other end is connected with the molecular pump unit (11) through the pipeline seven (27), the molecular pump unit (11) is used for vacuumizing the test system, the maximum vacuum degree is less than 10 -5 Pa; the cold trap (9) is a low-temperature container, which is connected at the joint of the pipeline six (26) and the pipeline seven (27) and is used for protecting the vacuum gauge (10) and the molecular pump unit (11) from absorbing water vapor or impurities during the vacuumizing process; the vacuum gauge (10) is installed on the pipeline seven (27) and is used for measuring the vacuum degree of the test system; The test system further comprises a plurality of vacuum valves, the second pipeline (22) is a metal hose, at least one vacuum valve one (31) is installed on the second pipeline (22), at least one vacuum valve two (32) is installed on the third pipeline (23), at least one vacuum valve three (33) is installed on the fourth pipeline (24), at least one vacuum valve four (34) is installed on the fifth pipeline (25), and at least one vacuum valve five (35) is installed on the sixth pipeline (26).

3. The high temperature liquid metal convective heat transfer coefficient integrated test system of claim 1, wherein, The gas cylinder (1) contains high-purity argon with a purity of more than 99.99%; The glove box (2) is a sealed shell structure, and the inside is circulated and adsorbed by inert gas to maintain an inert gas environment, with a water and oxygen content of less than 0.1 ppm, so as to ensure that the liquid metal is not oxidized during processing and maintain high purity of the liquid metal; The glove box (2) further comprises a magnetic stirrer (4) and a heating tray (6), the magnetic stirrer (4) is used to accelerate the mixing of liquid metal alloy or nanoparticles, and the heating tray (6) is used to heat high-melting-point liquid metal to melt and maintain the liquid state, with a heating temperature higher than 500 DEG C. The constant-temperature tank (8) is a sealed shell structure, and the temperature required by the liquid metal is maintained by PID adjustment, with a maximum temperature of the liquid metal in the tank reaching 800 DEG C. The liquid metal electromagnetic pump (12) has a maximum pumping flow of 700 liters per hour, and the internal liquid metal temperature reaches 1200 DEG C, and the pumping speed is adjusted by the liquid metal electromagnetic pump (12). The maximum temperature of the liquid metal in the electromagnetic flowmeter (13) is 850 DEG C. The pipes and equipment in the convection heat exchange coefficient test circulating system are wrapped with aluminum silicate insulation cotton.

4. The high temperature liquid metal convective heat transfer coefficient integrated test system of claim 1, wherein, The convection heat exchanger (15) is a stainless steel pipe with smooth inner wall, and the inlet thermocouple (14) and the outlet thermocouple (17) are both inserted into the center of the pipe of the convection heat exchanger (15). The inner surface of the high-temperature heater (16) and the convection heat exchanger (15) are coated with a high-temperature heat-conducting agent (36). A plurality of carbon-silicon rods (37) are uniformly inserted into the circumferential direction of the high-temperature heater (16), and the outer wall of the high-temperature heater (16) is provided with a heat insulation coating (38), and the heat insulation coating (38) is wrapped with aluminum silicate insulation cotton (39).

5. The high temperature liquid metal convection heat transfer coefficient integrated test system of any of claims 1-4, wherein, The liquid metal is a metal that is liquid at room temperature, an alloy that is liquid at room temperature, or a high-temperature liquid metal element and an alloy with various proportions thereof that is solid at room temperature. The metal that is liquid at room temperature is at least mercury, cesium or gallium, the alloy that is liquid at room temperature is at least gallium-indium-tin alloy, and the high-temperature liquid metal element and the alloy with various proportions thereof that is solid at room temperature are at least an alloy composed of one or more of sodium, potassium, rubidium, lithium, tin, bismuth or antimony.

6. The high temperature liquid metal convection heat transfer coefficient integrated test system of any of claims 1-4, wherein, The inner wall of each pipeline is a smooth surface, and the material is a high-temperature-resistant metal, which is at least stainless steel 316L, stainless steel 310S or nickel-based alloy; the connection mode of the pipeline and the equipment is flange connection or metal sleeve connection, which ensures that the vacuum degree of the test system is lower than 10 -3 Pa during the vacuumizing process.

7. A test method of the high-temperature liquid metal convection heat transfer coefficient integrated test system according to any one of claims 1-6, characterized in that, The method comprises the following steps: S1, pretreatment process: including connection of each equipment in the test system, and purification, weighing and preparation of the liquid metal working medium; S11, first, connect each equipment with the pipeline, and close the vacuum valve one (31), the vacuum valve two (32), the vacuum valve three (33), the vacuum valve four (34) and the vacuum valve five (35); S12, using the gas cylinder (1) to supply the glove box (2), open the circulation purification function of the glove box (2), so that the water oxygen content in the box is less than 0.1 ppm, and maintain at least 24 hours; S13, the liquid metal storage tank (3), magnetic stirrer (4), precision balance (5), heating tray (6) and liquid metal mixing tank (7) are put into the glove box (2), the liquid metal storage tank (3) stores the required liquid metal, the liquid metal mixing tank (7) is placed on the precision balance (5) for skinning weighing, and then the purification, weighing and preparation of the liquid metal are carried out; S2, test process: including the change of gas atmosphere in the test system, and the delivery and circulation test of liquid metal; S21, based on the high temperature liquid metal chemical property, it is easy to react with oxygen and water vapor in the air, before the test, change the gas atmosphere of the whole test system; After the pretreatment process is finished, the gas atmosphere of the system pipeline and equipment except the glove box (2) is air, open the vacuum valve three (33), vacuum valve four (34) and vacuum valve five (35), fill the cold trap (9) with liquid nitrogen, and keep the ultra-low temperature state of the cold trap (9); S22, open the molecular pump unit (11) to the system for vacuum, vacuum gauge (10) measured by the number of less than 10 -3 Pa after one hour, immediately close the molecular pump unit (11); open the vacuum valve two (32), using cylinder (1) to the test system for gas supply, so that the system pipeline full of inert gas; then close the vacuum valve two (32), open the molecular pump unit (11) again to vacuum; S23, repeat step S22 three times, and finally keep the test system in vacuum state; S24, close the vacuum valve two (32), vacuum valve three (33), vacuum valve four (34) and vacuum valve five (35), complete the change of gas atmosphere in the test system; At this time, the glove box (2) is in normal pressure inert gas atmosphere, and the constant temperature tank (8) is in vacuum state; S25, open the vacuum valve one (31), the high temperature liquid metal in the liquid metal mixing tank (7) is sucked into the constant temperature tank (8) under the action of the pressure difference between the glove box (2) and the constant temperature tank (8), and the liquid level in the liquid metal mixing tank (7) is higher than the inlet of the pipeline two (22) during the suction process, so as to ensure that the inert gas will not enter the constant temperature tank (8); Then close the vacuum valve one (31), complete the delivery of high temperature liquid metal; S26, circulation test process: S261, first open the heating function of the constant temperature tank (8) to melt and preheat the internal high temperature liquid metal, so that the high temperature liquid metal remains liquid; Open the high temperature heater (16) for heating, so that the temperature of the thermocouple on the outer wall of the pipeline of the convection heat exchanger (15) reaches more than 800℃; S262, then open the vacuum valve three (33) and vacuum valve four (34), open the liquid metal electromagnetic pump (12), the liquid metal electromagnetic pump (12) has self suction capacity, the high temperature liquid metal in the constant temperature tank (8) is sucked into the convection heat exchanger (15) under the action of the liquid metal electromagnetic pump (12), and finally returns to the constant temperature tank (8), forming a working cycle; S263、At this time, the high-temperature heater (16) maintains the heating state, the thermostat tank (8) turns into the cooling state, and finally, when the temperature of the thermocouple on the outer wall of the pipeline of the convection heat exchanger (15) reaches the preset temperature, the heating and cooling are balanced, and the balance state is maintained for at least one hour to complete the collection of a set of experimental data; the preset temperature is any temperature in the range from the melting point of the high-temperature liquid metal to 800°C according to the experimental requirements, the preset temperature is adjusted by changing the heating power of the high-temperature heater (16), and a plurality of sets of experimental data are collected; the mass flow rate of the high-temperature liquid metal is controlled by changing the volume flow rate of the liquid metal electromagnetic pump (12), and a plurality of sets of experimental data are collected by controlling the flow rate of the high-temperature liquid metal; the collected experimental parameters include the volume flow rate in the balance state, the temperature of the thermocouple on the outer wall of the pipeline of the convection heat exchanger (15), the temperature of the inlet thermocouple (14), and the temperature of the outlet thermocouple (17); S3、Post-processing process: S31、After the data collection is completed, the vacuum valve four (34) is closed, the high-temperature liquid metal in the convection heat exchanger (15) and the pipeline is returned to the thermostat tank (8) under the action of the liquid metal electromagnetic pump (12), and then the vacuum valve three (33), the liquid metal electromagnetic pump (12), and the high-temperature heater (16) are closed; at this time, all the high-temperature liquid metal is in the thermostat tank (8), and when the high-temperature liquid metal in the thermostat tank (8) is cooled to 100°C, the high-temperature melting point, the vacuum valve two (32) is opened to supply gas to the thermostat tank (8), and at this time, the thermostat tank (8) is in a positive pressure inert gas atmosphere; S32、Subsequently, the liquid metal storage tank (3) is placed under the residual opening at the bottom of the thermostat tank (8), the residual opening is opened, and the high-temperature liquid metal in the thermostat tank (8) flows into the liquid metal storage tank (3) under the action of the pressure difference and gravity, and the liquid metal storage tank (3) is placed back into the glove box (2); S33、Finally, the vacuum valve three (33) and the vacuum valve four (34) are opened, the entire test system is filled with inert gas, the vacuum valve two (32) is closed, and the post-processing process is completed.

8. The test method of claim 7, wherein, In step S13, for liquid metal with melting point lower than room temperature, the surface oxide film and impurities are removed by using a micro-syringe, and then the liquid metal is extracted from the bottom of the syringe and put into the liquid metal mixing tank (7), so as to complete the purification of the liquid metal, and finally the liquid metal is weighed according to the requirement; for high-temperature liquid metal with melting point higher than room temperature, the liquid metal is stored in the form of block solid in the liquid metal storage tank (3), and the block solid is taken out by using tweezers, and the surface oxide layer and impurities are removed in the glove box (2), and then the block solid is put back into the liquid metal storage tank (3), the liquid metal storage tank (3) is placed on the heating tray (6), the temperature of the heating tray (6) is set to be 100℃ higher than the melting point of the liquid metal, and the block solid is melted, the surface oxide film and impurities are removed by using a micro-syringe, and then the liquid metal is extracted from the bottom of the syringe and put into the liquid metal mixing tank (7), so as to complete the purification of the high-temperature liquid metal, and finally the liquid metal is weighed according to the requirement; for liquid metal alloy, the same number of liquid metal storage tanks and liquid metal mixing tanks are prepared according to the types of liquid metals in the alloy, the above-mentioned purification process is repeated, the liquid metals are weighed according to the proportion and then combined into one liquid metal mixing tank (7), so as to complete the preparation of the liquid metal alloy. In step S25, for high-temperature liquid metal with melting point higher than room temperature, the liquid metal mixing tank (7) is placed on the heating tray (6), the heating temperature of the heating tray (6) is set to be 150℃ higher than the melting point of the high-temperature liquid metal, and after the high-temperature liquid metal is completely melted, the vacuum valve one (31) is opened to transport the high-temperature liquid metal; for normal-temperature liquid metal with melting point lower than room temperature, the heating tray (6) is not needed to be used for heating.

9. The test method of claim 7, wherein, The convective heat transfer coefficient of the liquid metal nanofluid is measured after adding various types and proportions of nanoparticles in the liquid metal, the nanoparticles do not denature and do not react with the liquid metal in the measurement temperature range, the maximum measurement temperature is 800℃, and the lower value of 50℃ lower than the boiling point of the measured liquid metal, and the measurement temperature is the temperature measured by the outlet thermocouple (17); The preparation method of the nanofluid is as follows: Firstly, the required nanoparticles are placed in the glove box (2), and are dried on the heating tray (6) for at least 24 hours, and the temperature is 100℃, and the water-free and oxygen-free environment in the glove box (2) is used to ensure that the nanoparticles are not oxidized during the drying process; the magnetic stirrer (4) is placed on the precision balance (5) for skinning and weighing, the required pure liquid metal is extracted from the bottom of the liquid metal storage tank (3) by using a syringe, and is placed in the magnetic stirrer (4), and the mass of the liquid metal is weighed; the mass of the required nanoparticles is calculated, the mass of the nanoparticles accounts for 0.1%~2.5% of the mass of the liquid metal, the required nanoparticles are weighed on the precision balance (5), and the required nanoparticles are added to the magnetic stirrer (4); the magnetic stirrer (4) is started to mix and stir the liquid metal and the nanoparticles, in order to prevent overheating during stirring, the rotating speed is lower than 200 revolutions per minute, and the stirring time is not less than 12 hours; the fluid after stirring is the required nanofluid.

10. The method of claim 7-9, wherein the method further comprises: The calculation method of the high-temperature liquid metal convection heat transfer coefficient is as follows: First, the heating power outputted from the high-temperature heater (16) to the convection heat exchanger (15) is calculated Q : ； ； wherein is the mass flow rate of the high temperature liquid metal, is the specific heat capacity at constant pressure of the high temperature liquid metal, is the density of the high temperature liquid metal, is the volume flow rate of the high temperature liquid metal, the above parameters being values at a temperature of the high temperature liquid metal of , is the temperature measured by the outlet thermocouple, is the temperature measured by the inlet thermocouple; The temperature at the inlet and outlet of the inner wall of the convection heat exchanger (15) is obtained by measuring the thermocouple temperature at the inlet and outlet of the outer wall of the convection heat exchanger (15): ； ； wherein Tin is the temperature at the inlet of the inner wall of the counterflow heat exchanger, Tout is the temperature at the outlet of the outer wall of the counterflow heat exchanger, t is the wall thickness of the counterflow heat exchanger, k is the thermal conductivity of the material used for the counterflow heat exchanger, Tin is the temperature at the inlet of the inner wall of the counterflow heat exchanger, Tout is the temperature at the outlet of the outer wall of the counterflow heat exchanger, The high-temperature liquid metal convection heat transfer coefficient satisfies the following formula: ； ； ； wherein is the heat transfer coefficient of the high-temperature liquid metal, is the heat transfer area of the convection heat exchanger, is the average temperature difference between the high-temperature liquid metal and the inner wall of the convection heat exchanger, is the inner diameter of the convection heat exchanger, is the effective length of the convection heat exchanger; The high-temperature liquid metal convection heat transfer coefficient correlation formula is fitted: High temperature liquid metal convective heat transfer coefficient and and the dimensionless number Peclet number (Pe) in heat transfer, wherein the Peclet number is the product of the Reynolds number (Re) and the Prandtl number (Pr), satisfying the following formula: ； ； ； wherein is the flow rate of the high-temperature liquid metal, is the viscosity of the high-temperature liquid metal, is the thermal conductivity of the high-temperature liquid metal, the above parameters being values at a temperature of the high-temperature liquid metal of . Flow rate of high-temperature liquid metal satisfies the following equation: ； The high-temperature liquid metal convection heat transfer coefficient correlation formula satisfies the following formula: ； In the formula, a, b, c, d are all constants, b and c are respectively and the power of Pe; The high-temperature liquid metal convection heat transfer coefficient is calculated through the correlation formula, and when the average error between the experimental value and the predicted value is less than 5%, the high-temperature liquid metal convection heat transfer coefficient correlation formula is effective.

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