A multi-point temperature control experimental device and experimental method for pool boiling heat transfer

Abstract

The application discloses a kind of for pool boiling heat transfer stretch-in multi-point temperature control experimental device and experimental method, belong to energy heat transfer technical field.The device includes boiling chamber, stretch-in pool boiling system, cooling circulation system, data acquisition system and temperature control system.Stretch-in pool boiling system is installed in chamber top cover by L-shaped hollow structure rod, and the second end is provided with heat insulation material, test object is embedded in the surface of heat insulation material, and multi-point temperature control device is located between test object and heat insulation material, to realize local temperature accurate control.The application is through stretch-in structure and multi-point independent temperature control, solve the problem that existing device temperature control precision is low, space utilization is poor and experimental preparation is complicated, and can effectively avoid working medium leakage, provide high-precision experimental platform for bubble dynamics research.

Description

Technical Field

[0001] This invention relates to the field of energy heat exchange technology, and more specifically, to an immersion-type multi-point temperature control experimental device and method for pool boiling heat exchange. Background Technology

[0002] With the rapid development of industrial technology, many industries have placed higher demands on the thermal management of equipment. Ordinary air cooling and water cooling are no longer sufficient to meet the heat dissipation needs of equipment with large heat fluxes. Boiling heat transfer is a typical phase change heat transfer method. The latent heat generated by the continuous and intense phase changes within a liquid in a saturated state carries away a large amount of heat. Pool boiling (also known as boiling within a large container) can enhance heat transfer performance by changing the wall surface condition and the working medium, without requiring additional power. It can provide extremely high heat transfer efficiency under relatively small temperature differences, and therefore has been widely used in the energy and chemical industry.

[0003] Numerous factors influence the boiling heat transfer process in large containers, including the characteristics of the boiling working fluid and the surface physical properties of the heating surface. Among these, wall superheat and surface roughness directly affect the vaporization nucleus density of the wall, thereby altering bubble dynamics and ultimately determining the heat transfer performance of pool boiling. In pool boiling experiments, the measurement of wall temperature is crucial, as it relates to the accuracy of subsequent calculations of heat flux density and boiling heat transfer coefficient.

[0004] However, existing pool boiling experimental apparatuses and methods have many problems. Most existing heating devices are monolithic, which, while increasing simplicity, cannot precisely control local temperatures, leading to ineffective control of bubble dynamics. Specifically, the following drawbacks exist: 1) In the later processing of surface temperature, integrated heating devices often assume uniform wall temperature, which significantly deviates from the non-uniform wall temperature changes during actual pool boiling; 2) Traditional heating devices are large, making it difficult to directly machine the test surface onto its top, often requiring additional test pieces and increasing structural complexity; 3) An unavoidable gap exists between the test object and the side fixing components. Since the test piece must be completely immersed in the working fluid, bubbles easily form within the gap as heat flux density increases, interfering with the visualization of bubble dynamics in the main heat exchange region; 4) After the experiment, additional methods are needed to remove the internal working fluid or replace the boiling surface, resulting in a lengthy and cumbersome experimental preparation process, consuming considerable manpower and resources; 5) Common pool boiling equipment requires openings at the bottom of the chamber to allow the test piece to extend, and the large size of the heating device leads to low overall space utilization. Summary of the Invention

[0005] To address the aforementioned problems in the existing technology, this invention provides an extended multi-point temperature control experimental device and method for pool boiling heat exchange, aiming to solve technical problems such as low accuracy of boiling surface temperature control, high equipment space occupancy, and cumbersome experimental replacement process.

[0006] To address the aforementioned technical problems, this invention provides an extended-type multi-point temperature control experimental device for pool boiling heat exchange, comprising: a boiling chamber, an extended-type pool boiling system, a cooling circulation system, a data acquisition system, and a temperature control system. The extended-type pool boiling system includes an extended-type hollow structural rod, a multi-point temperature control device, thermal insulation material, a power supply line, and a DC power supply. The extended-type hollow structural rod is L-shaped, comprising a first end and a second end. The first end is connected to the top cover of the boiling chamber, and the second end extends into the boiling chamber and has a mounting hole. The thermal insulation material is disposed within the mounting hole, and the side of the thermal insulation material protruding from the second end has a mounting groove. The test object of the pool boiling experimental device is placed in the mounting groove. The multi-point temperature control device is located between the test object and the thermal insulation material, and is connected to the DC power supply located outside the boiling chamber via the power supply line, for independently controlling the temperature of the test object in designated zones.

[0007] Furthermore, the boiling chamber includes a top cover, a chamber wall, and a transparent material. The top cover and the chamber wall are connected by bolts. The transparent material is connected to the chamber wall by bolts, and the transparent material is disposed on the lower portion of both sides of the chamber wall facing each other, for observing changes in bubble dynamics.

[0008] Furthermore, it also includes a sealing element disposed at the connection between the transparent material and the cavity wall to prevent leakage of the boiling working fluid. The sealing element is a silicone ring or a silicone pad.

[0009] Furthermore, it also includes a boiling working medium inlet with a first control valve and a boiling working medium outlet with a second control valve, both of which are located on the side wall of the boiling chamber and are used to control the injection and discharge of the working medium, respectively.

[0010] Furthermore, the heat insulation material is block polytetrafluoroethylene; the test object is a silicon material with a thickness of millimeters; the multi-point temperature control device includes multiple electric heating elements of different specifications and sizes, and the power is controlled by an independent DC power supply.

[0011] Furthermore, the cooling circulation system includes an internal condenser coil, a circulation pump, a liquid outlet valve, and a thermostatic cooler. The condenser coil is located at the top of the boiling chamber, and the cooling medium after heat exchange is cooled by the thermostatic cooler and then reintroduced into the condenser coil.

[0012] Furthermore, the data acquisition system includes a temperature sensor, a multi-channel temperature scanner, a data storage device, a high-speed camera, and a cold light source. The temperature sensor is positioned on the side of the test object facing the insulation material to measure the wall temperature; the high-speed camera is aimed at the transparent material area, and the cold light source is used for supplementary lighting.

[0013] Furthermore, the temperature control system includes a temperature measuring device, a heating rod, and an automatic temperature control system, used to maintain the working fluid inside the boiling chamber in a saturated state.

[0014] The present invention also provides an experimental method for pool boiling heat exchange using the apparatus described above, comprising the following steps: Step 1: Connect the test object to the multi-point temperature control device and temperature sensor, install the extended multi-point temperature control experimental device on the top of the boiling chamber, inject the boiling working fluid and seal it; Step 2: Turn on the DC power supply and temperature control system to bring the working fluid to a saturated boiling state; Step 3: When the temperature sensor detects a temperature change of less than 0.5℃ within 8 minutes, the bubble behavior is recorded using a high-speed camera through a transparent material, and the wall temperature is recorded using a multi-channel temperature scanner. Step 4: Under experimental condition I, control the number of working points of the multi-point temperature control device to control the local temperature and obtain isolated bubbles and bubble merging phenomena under low heat flux density; under experimental condition II, turn on all heating elements and run them at the same power to obtain bubble phenomena and temperature data under different heat flux densities. After the experiment, the bubble diameter and detachment frequency were calculated based on the images from the high-speed camera, and the heat flux density was calculated based on the heating power and area.

[0015] Furthermore, step one also includes: using waterproof sealing silicone to adhere the multi-point temperature control device and temperature sensor to the bottom of the test object, and then attaching the whole assembly to the groove of the heat insulation material. Step five also includes: after the experiment, opening the second control valve to discharge the working fluid, removing the top cover to replace the test object or boiling working fluid for repeatability experiments.

[0016] Compared with the prior art, the technical solution of the present invention has the following advantages: 1. This invention achieves independent temperature control of the test object in different zones through a multi-point temperature control device, which can accurately control the local wall temperature, facilitate the observation of isolated bubble behavior and bubble merging phenomenon, and ensure the accuracy of local temperature by combining thermocouple measurement, thereby improving the accuracy of experimental results.

[0017] 2. This invention adopts an L-shaped hollow structure rod that is connected to the top cover via a flange. It is easy to assemble and disassemble, and the heat exchange surface can be replaced without disassembling the entire equipment. It can also flexibly change the shape and roughness of the test object, while effectively solving the water leakage problem that may exist in external devices.

[0018] 3. The boiling chamber of the present invention is provided with working medium inlet and outlet with valves on the side wall, which facilitates the rapid replacement of working medium after the experiment and simplifies the operation process.

[0019] 4. Except for the transparent observation window, the chambers of this invention are all wrapped with heat-insulating material, which reduces heat loss and ensures the stability of the experimental environment. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the extended multi-point temperature control experimental device for pool boiling heat exchange provided in an embodiment of the present invention.

[0021] The meanings of the markings in the diagram are as follows: 1. Top cover; 2. First control valve; 3. Boiling medium inlet; 4. Cavity wall; 5. Temperature measuring device; 6. Heating rod; 7. Transparent material; 8. Second control valve; 9. Boiling medium outlet; 11. Insulation material; 12. Multi-point temperature control device; 13. Test object; 14. Extendable hollow structure rod; 15. Power supply line; 16. Temperature sensor; 17. External insulation material; 18. Top cover connecting bolt; 19. Fixing bolt; 20. DC power supply; 21. Condensing coil; 22. Pressure gauge; 23. Automatic pressure regulating valve; 24. Circulating pump; 25. Liquid outlet valve; 26. Constant temperature cooler; 27. Automatic temperature control system; 28. Cold light source; 29. ​​High-speed camera; 30. Data storage device; 31. Multi-channel temperature scanner. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. The described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] like Figure 1As shown, an extended-type multi-point temperature-controlled experimental device for pool boiling heat exchange includes a boiling chamber, an extended-type pool boiling system, a cooling circulation system, a data acquisition system, and a temperature control system. The boiling chamber includes a top cover 1, a boiling working fluid inlet 3 with a first control valve 2, a chamber wall 4, a transparent material 7, a boiling working fluid outlet 9 with a second control valve 8, external insulation material 17, and top cover connecting bolts 18. The top cover 1 is connected to the side wall via the top cover connecting bolts 18. The top cover 1 and the boiling chamber wall 4 are made of stainless steel, and the external insulation material is multi-layer aerogel felt. The top cover 1 is equipped with a pressure regulating device including a pressure gauge 22 and an automatic pressure regulating valve 23.

[0024] The cooling circulation system includes an internal condenser coil 21, a circulation pump 24, an outlet valve 25, and a thermostatic cooler 26. The cooling medium after heat exchange is cooled by the thermostatic cooler 26 and then sent back to the condenser coil 21 to condense the internal steam to ensure that the height of the internal experimental medium remains basically unchanged.

[0025] The data acquisition system includes a temperature sensor 16, a multi-channel temperature scanner 31, a data storage device 30, a high-speed camera 29, and a cold light source 28. The temperature sensor 16 works in conjunction with the multi-point temperature control device 12 to measure the temperature of the boiling surface 13 and control the temperature of the area. The high-speed camera 29 is aimed at the boiling surface in the area of ​​the transparent material 7 to capture images. The cold light source 28 is placed on the other side to provide supplementary lighting. The data storage device 30 is connected to the high-speed camera 29 and the multi-channel temperature scanner 31 to store images and temperature data.

[0026] The temperature control system includes a temperature measuring device 5, a heating rod 6, and an automatic temperature control system 27. It heats the working medium by extending into the interior through the opening in the wall 4 of the boiling chamber, and keeps the internal working medium saturated throughout the experiment.

[0027] The extendable pool boiling system also includes an extendable hollow structure rod 14, a test object 13, a multi-point temperature control device 12, a heat insulation material 11, a power supply line 15, a temperature sensor 16, fixing bolts 19, and a DC power supply 20. The multi-point temperature control device 12 is in direct contact with the test object 13, with some leeway. A high thermal conductivity material is used to attach the temperature sensor 16 to the side of the test object 13 facing the heat insulation material 11 for temperature measurement. The test object 13, the multi-point temperature control device 12, and the temperature sensor 16 are attached to the mounting groove provided on the side of the heat insulation material 11 that protrudes from the extendable hollow structure rod 14. The heat insulation material 11 is made of block polytetrafluoroethylene, which is easy to process and has a low thermal conductivity, ensuring that heat is lost only from the boiling surface to the working fluid. The aforementioned device can improve the local temperature control accuracy of the test object and effectively solve the problem of working fluid leakage. In addition, since no additional support structure is required, the space occupancy of the entire device is effectively reduced. Finally, the increase in the working fluid inlet and outlet and the introduction of the extended boiling structure directly optimize the experimental preparation process, thereby shortening the time for multiple experiments.

[0028] Example 1: An experimental method for multi-point temperature control using an insertion method for pool boiling heat exchange, the specific operation steps are as follows: Step 1: Before the experiment, connect the surface to be tested to the heating element and the temperature measuring thermocouple; install the extendable multi-point temperature control experimental device on the top of the boiling chamber, add the boiling working medium into the chamber through the side wall inlet, and seal the chamber.

[0029] Step one further includes: using waterproof sealing silicone to bond the multi-point temperature control device 12 and temperature sensor 16 to the side of the test object 13 facing the heat insulation material 11, and then bonding the above parts into the groove provided on the top of the heat insulation material 11, which significantly reduces the dissipation of wall temperature from other sides. The extended hollow structure rod 14 is divided into two ends. The first end is connected to the top cover 1 by bolts 19, and the second end extends into the boiling chamber and is provided with a mounting hole. The heat insulation material 11 is placed in the mounting hole at the second end of the extended hollow structure rod 14, and the interference part is sealed with sealant to prevent the working fluid from leaking into the extended hollow structure rod 14. The power supply line 15 is connected to the multi-point temperature control device 12 through copper wires to provide Joule heating, and the other end is connected to the DC power supply 20. In order to improve the power control accuracy, an independent DC power supply needs to be provided for each heating point in the multi-point temperature control device 12. The hollow structural rod 14 is connected to the top cover 1 by bolts 19, and then the top cover 1 is installed on the side wall 4 of the boiling chamber by multiple bolts 18 to form a sealed boiling chamber. The second control valve 8 is closed, and the first control valve 2 is opened to allow the boiling working medium to enter the sealed chamber through the inlet channel 3. To ensure a consistent liquid level, the amount of working medium injected into the boiling chamber is kept the same in each experiment. After injection, the first control valve 2 is closed. The transparent material 7 is a highly transparent material, which can be quartz glass but is not the only option. It is fixed in the gap reserved in the side wall of the boiling chamber by a sealing ring and bolts.

[0030] Step 2: Turn on the DC power supply. Its output power is displayed on the power supply's built-in display panel. By changing the power, the heat flux density on the wall is changed. When the temperature reaches the nucleation temperature, boiling begins.

[0031] Step two further includes: turning on the temperature control system 27 to heat the internal working fluid; simultaneously, turning on the constant temperature cooler 26, circulating pump 24, and outlet valve 25 to condense the steam in the boiling chamber and replenish the internal boiling working fluid with the condensed water, ensuring that the liquid level of the internal working fluid remains constant throughout the experiment. Since the test object is significantly lower than the liquid level surface, the impact of dripping liquid on the condenser coil 21 on the experiment can be reduced. The temperature of the circulating cooling working fluid needs to be adjusted during the experiment to accommodate changes in steam volume at different heat flux densities. After the internal working fluid is saturated, it is maintained for a period of time to fully boil and remove non-condensable steam, improving experimental accuracy. An automatic pressure regulating valve 23 is installed on the boiling top cover 1, which automatically controls the internal pressure to maintain it at ambient pressure.

[0032] Step 3: When the temperature change of temperature sensor 16 is less than 0.5℃ within 8 minutes, the behavior of bubbles on the wall surface can be recorded by a high-speed camera through the transparent material on the side wall. The wall surface temperature is recorded by a multi-channel temperature scanner 31. Experimental condition I: When the working fluid temperature inside the boiling chamber reaches the experimental set temperature, the number of heating elements is controlled to control the local temperature of the boiling surface, thereby obtaining the phenomenon of isolated bubble growth and bubble merging under low heat flux density conditions.

[0033] Step three specifically includes: before the experiment, turning on the high-speed camera 29 and the back-lit cold light source 28, determining the shooting parameters of the high-speed camera 29, adjusting the intensity, angle, and position of the cold light source 28 to ensure optimal image quality, turning on the DC power supply 20 according to experimental requirements, and adjusting the power to control the heat flux density. Adjusting the number of multi-point temperature control devices 12 activated to control the temperature of different areas of the boiling surface 13, and operating multi-point temperature control devices 12 with different spacing, numbers, and power levels to observe bubble behavior under low heat flux density conditions. Combined with the high-speed camera 29 and the back-lit cold light source 28, phenomena such as bubble nucleation, bubble growth, bubble detachment, and bubble merging on surfaces with different superheats can be fully analyzed and explained.

[0034] Step 4: After the experimental data collection is completed, calculate the bubble diameter based on the resolution of the high-speed camera and the length of the boiling surface of the observation platform. Calculate the bubble detachment frequency based on the number of bubbles detached captured by the high-speed camera within a certain time. Calculate the heat flux density based on the heating power and heating area. After the experiment, the boiling surface (13) or boiling working medium can be replaced and Step 1 to Step 4 can be repeated to study the boiling heat transfer performance of different boiling surfaces and boiling working media.

[0035] Step four specifically includes: after the experiment, the second control valve 8 can be opened without waiting for the working fluid to cool down, so that the deionized water can flow out of the main boiling chamber through the outlet channel 9; the bolts 18 are removed to separate the top cover 1 and the boiling sidewall 4, and after replacing the boiling surface 13, steps one to four are repeated, so that repeatable experiments can be performed on different boiling surfaces.

[0036] This embodiment can achieve point control of wall temperature by controlling the heating power at multiple locations. Combined with a high-speed camera, it can fully observe the behavior of isolated bubbles and the interaction behavior of bubbles under different wall temperature conditions, and further reveal the influence of bubble behavior on boiling heat transfer performance from a mechanistic perspective.

[0037] Example 2: An experimental method for multi-point temperature control in a pool boiling heat exchange, wherein the experimental conditions and data processing objectives in steps three and four are different from those in Example 1.

[0038] Step 3: When the temperature sensor 16 changes less than 0.5℃ within 8 minutes, the bubble behavior on the wall surface can be recorded by a high-speed camera through the transparent material on the side wall. The wall surface temperature is recorded by a multi-channel temperature scanner 31. Experimental condition II: Turn on all heating elements and ensure that they use the same power. After maintaining this for a period of time, the bubble phenomenon on the boiling surface is obtained when the same heat flux density is obtained. The heating power is continuously increased to obtain the bubble phenomenon and temperature data at different heat flux densities. In this embodiment, step three further includes: before the experiment, turning on the high-speed camera 29 and the back-lit cold light source 28, determining the shooting parameters of the high-speed camera 29, adjusting the intensity, angle, and position of the cold light source 28 to ensure optimal image quality, turning on the DC power supply 20 according to experimental requirements, and adjusting the power to control the heat flux density. All multi-point temperature control devices 12 are run and kept at the same power to observe bubble behavior under different heat flux density conditions. Combined with the high-speed camera 29 and the back-lit cold light source 28, the violent bubble phenomena such as bubble merging, gas column interaction, and film boiling on surfaces with different superheats can be fully analyzed and explained.

[0039] Step 4: After the experimental data acquisition is completed, calculate the bubble diameter based on the resolution of the high-speed camera and the length of the boiling surface of the observation platform. Analyze the triggering mechanism of film boiling based on the violent bubble behavior captured by the high-speed camera. Calculate the average heat flux density based on the heating power and heating area. After the experiment, the boiling surface (13) or boiling medium can be replaced and Step 1 to Step 4 can be repeated to study the boiling heat transfer performance and critical heat flux of different test objects and boiling mediums.

[0040] In this embodiment, step four further includes: after the experiment is completed, the second control valve 8 can be opened without waiting for the working fluid to cool down, so that the deionized water flows out of the main boiling chamber through the outlet channel 9; and the bolts 18 are removed to separate the top cover 1 and the boiling sidewall 4.

[0041] This embodiment can achieve the goal of keeping all parts of the surface at the same temperature by controlling all heating devices to the same power. Combined with a high-speed camera, it can fully observe the merging and detachment of bubbles at high heat flux density, and further reveal the influence of bubble behavior on boiling heat transfer performance from a mechanistic perspective, thereby providing support for predicting the occurrence of film boiling.

[0042] The present invention and its embodiments have been described above illustratively. This description is not restrictive, and the figures shown are only one embodiment of the present invention; the actual structure is not limited thereto. Therefore, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. An immersion-type multi-point temperature control experimental device for pool boiling heat exchange, characterized in that, include: The boiling chamber, the extendable pool boiling system, the cooling circulation system, the data acquisition system, and the temperature control system; the extendable pool boiling system includes an extendable hollow structure rod (14), a multi-point temperature control device (12), heat insulation material (11), a power supply line (15), and a DC power supply (20); the extendable hollow structure rod (14) is an L-shaped structure, which includes a first end and a second end, the first end being connected to the top cover (1) of the boiling chamber, and the second end extending into the boiling chamber and having an installation hole; The heat insulation material (11) is disposed in the mounting hole, and the side of the heat insulation material (11) protruding from the second end is provided with a mounting groove; the test object (13) of the pool boiling test device is placed in the mounting groove; the multi-point temperature control device (12) is located between the test object (13) and the heat insulation material (11), and is connected to the DC power supply (20) located outside the boiling chamber through the power supply line (15) for independent temperature control of the test object (13) in zones.

2. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 1, characterized in that, The boiling chamber includes a top cover (1), a chamber wall (4), and a transparent material (7). The top cover (1) and the chamber wall (4) are connected by bolts (18). The transparent material (7) is connected to the chamber wall (4) by bolts. The transparent material (7) is located on the lower part of the chamber wall (4) on both sides for observing changes in bubble dynamics.

3. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 2, characterized in that, It also includes a sealing element, which is disposed at the connection between the transparent material (7) and the cavity wall (4) to prevent leakage of the boiling working fluid. The sealing element is a silicone ring or a silicone pad.

4. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 1, characterized in that, It also includes a boiling working medium inlet (3) with a first control valve (2) and a boiling working medium outlet (9) with a second control valve (8). The boiling working medium inlet (3) and the boiling working medium outlet (9) are both located on the side wall of the boiling chamber. The first control valve (2) is used to control the injection of the boiling working medium, and the second control valve (8) is used to control the discharge of the boiling working medium.

5. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 1, characterized in that, The heat insulation material (11) is block polytetrafluoroethylene; the test object (13) is silicon material with a thickness of millimeters; the multi-point temperature control device (12) includes multiple electric heating elements of different specifications and sizes.

6. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 1, characterized in that, The cooling circulation system includes an internal condenser coil (21), a circulation pump (24), a liquid outlet valve (25), and a constant temperature cooler (26). The condenser coil (21) is located at the top of the boiling chamber. The cooling medium after heat exchange is cooled by the constant temperature cooler (26) and then sent back to the condenser coil (21).

7. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 1, characterized in that, The data acquisition system includes a temperature sensor (16), a multi-channel temperature scanner (31), a data storage device (30), a high-speed camera (29), and a cold light source (28); the temperature sensor (16) is located on the side of the test object (13) facing the heat insulation material (11) and is used to measure the wall temperature; the high-speed camera (29) is aimed at the area of ​​the transparent material (7), and the cold light source (28) is used for supplementary lighting.

8. The extended multi-point temperature control experimental device for pool boiling heat exchange according to claim 1, characterized in that, The temperature control system includes a temperature measuring device (5), a heating rod (6), and an automatic temperature control system (27) to maintain the working fluid inside the boiling chamber in a saturated state.

9. An experimental method for pool boiling heat transfer using the apparatus described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Connect the test object (13) to the multi-point temperature control device (12) and the temperature sensor (16), install the extended multi-point temperature control experimental device on the top of the boiling chamber, inject boiling working fluid and seal it; Step 2: Turn on the DC power supply (20) and the temperature control system (27) to make the working fluid reach a saturated boiling state; Step 3: When the temperature sensor (16) changes less than 0.5°C within 8 minutes, the bubble behavior is recorded by a high-speed camera (29) through a transparent material (7), and the wall temperature is recorded by a multi-channel temperature scanner (31). Step 4: Under experimental condition I, control the number of working points of the multi-point temperature control device (12) to control the local temperature and obtain isolated bubbles and bubble merging phenomena under low heat flux density; Under experimental condition II, all heating elements were turned on and operated at the same power to obtain bubble phenomena and temperature data under different heat flux densities. After the experiment, the bubble diameter and detachment frequency were calculated based on the images from the high-speed camera (29), and the heat flux density was calculated based on the heating power and area.

10. The experimental method according to claim 9, characterized in that, Step one also includes: using waterproof sealing silicone to bond the multi-point temperature control device (12) and temperature sensor (16) to the bottom of the test object (13), and then bonding them together in the groove of the heat insulation material (11); Step five also includes: after the experiment, opening the second control valve (8) to discharge the working medium, removing the top cover (1) to replace the test object (13) or the boiling working medium for repeatable experiments.

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