Device and method for measuring flow boiling characteristics of high-temperature high-pressure subcooled water in microchannels

Abstract

The application discloses a device for measuring flow boiling characteristics of high-temperature and high-pressure subcooled water in a micro channel, which comprises a water tank, a first valve, a filter, a high-pressure constant-flow pump, a mass flowmeter, a second valve, a heating test system, a fifth valve, a condenser, a back pressure valve and a float flowmeter connected in sequence through pipelines, and the float flowmeter is further communicated with the water tank through a pipeline; a first temperature sensor is further arranged on the pipeline between the second valve and the heating unit; a data acquisition and display system is further arranged, and the mass flowmeter, the heating test system and the float flowmeter are connected with the data acquisition and display system. The device solves the problems of high cost, low operation reliability and unstable test parameters of the high heat flow subcooled boiling test platform in the prior art. A method for measuring flow boiling characteristics of high-temperature and high-pressure subcooled water in a micro channel is further disclosed.

Description

Technical Field

[0001] This invention belongs to the field of multiphase flow heat transfer testing technology, specifically relating to a device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel, and also relating to a method for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel. Background Technology

[0002] Subcooled boiling refers to the flow boiling phenomenon where the temperature of the main fluid is below the saturation temperature, while the temperature of the heated wall surface has exceeded the saturation temperature. Due to its excellent flow characteristics such as high heat transfer coefficient and low flow resistance, it has been widely used in high heat flux heat transfer applications such as aerospace (Experimental heat transfer results and flow visualization of vertical upflow boiling in Earth gravity with subcooled inlet conditions – In preparation for experiments onboard the International Space Station[J]. International Journal of Heat and Mass Transfer, 2022, 188: 122603.), nuclear reactors (Critical heat flux of highly subcooled water flow boiling in circular tubes with and without internal twisted tapes under high mass fluxes[J]. International Journal of Heat and Mass Transfer, 2016, 95: 606-619.), and electronic equipment cooling (Review of correlations for subcooled flow boiling heat transfer and assessment of their applicability to water[J]. Fusion Engineering and Design, 2017, 122: 52-63.). In recent years, with the rapid development of miniature cooling and heat exchange equipment, subcooled boiling under high heat flux conditions and in microchannels has attracted widespread attention. Among these, the heat transfer characteristics of subcooled boiling flow are a research hotspot, as these characteristics are crucial to the safety, stability, and economy of related cooling and heat exchange systems.

[0003] Due to the high operating parameters, large heat exchange temperature difference, and numerous influencing factors on the heat transfer coefficient and flow resistance of high-heat-flux subcooled boiling systems, many technical problems have arisen in the measurement of the flow and heat transfer characteristics of high-heat-flux subcooled boiling systems. These problems mainly manifest as follows:

[0004] (1) It is difficult to maintain stable test parameters and it is difficult to simultaneously measure the resistance and heat transfer coefficient of high heat flux subcooled boiling with high precision.

[0005] (2) Under high temperature and high pressure conditions, when the pipe size reaches a microscale (internal diameter of 0.2 mm to 2 mm is considered a microchannel), the behavior of boiling bubbles will be significantly different compared to conventional channels (internal diameter > 2 mm). The flow and heat transfer characteristics of the fluid inside the pipe will be more complex, making it more difficult to stably measure the flow and heat transfer characteristics of the fluid inside the pipe.

[0006] (3) The above reasons result in high test costs and difficulty in ensuring test accuracy.

[0007] Therefore, providing a test platform that is reliable in operation, low in testing cost, has a wide range of test measurement parameters, and can accurately measure the heat transfer characteristics of supercooled boiling flow under high temperature and high pressure conditions in microchannels (0.2 mm to 2 mm) is a problem that urgently needs to be solved in this field. Summary of the Invention

[0008] The first objective of this invention is to provide a device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel, which solves the problems of high cost, low operational reliability, and unstable test parameters of existing high-heat-flux subcooled boiling test platforms.

[0009] The second objective of this invention is to provide a method for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel, which solves the problems of traditional measurement methods being complex to operate and difficult to simultaneously measure the subcooled boiling heat transfer coefficient and flow resistance with high precision.

[0010] The first technical solution adopted in this invention is a device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel. It includes a water tank, a first valve, a filter, a high-pressure constant flow pump, a mass flow meter, a second valve, a heating test system, a fifth valve, a condenser, a back pressure valve, and a float flow meter, all connected sequentially by pipes. The float flow meter is also connected to the water tank via a pipe. A first temperature sensor is installed on the pipe between the second valve and the heating unit. The device also includes a data acquisition and display system, with the mass flow meter, heating test system, and float flow meter all connected to the data acquisition and display system.

[0011] The invention is further characterized in that,

[0012] The heating test system includes a regenerator, a third valve, a preheating section, a first reducer, a test heating section, a second reducer, and a fourth valve, which are connected sequentially through pipes to form a loop. The fourth valve is connected to the regenerator through a pipe. A second temperature sensor is installed on the pipe between the regenerator and the third valve. A pressure transmitter and a third temperature sensor are installed on the pipe between the preheating section and the first reducer. A fourth temperature sensor is installed on the pipe between the second reducer and the fourth valve. The system also includes a differential pressure transmitter, which is connected to the inlet and outlet of the test heating section through two pipes. The second temperature sensor, the pressure transmitter, the third temperature sensor, the fourth temperature sensor, and the differential pressure transmitter are all connected to a data acquisition and display system.

[0013] The regenerator is an S-shaped double-layered tube, consisting of an inner tube and an outer tube. One end of the inner tube is the hot fluid inlet, and the other end is the hot fluid outlet. The hot fluid inlet is connected to the fourth valve via a pipe, and the hot fluid outlet is connected to the fifth valve via a pipe. The side wall of the outer tube near the hot fluid inlet has the regenerator's cold fluid outlet, and the side wall near the hot fluid outlet has the regenerator's cold fluid inlet. The regenerator's cold fluid outlet is connected to the third valve via a pipe, and the regenerator's cold fluid inlet is connected to the second valve via a pipe.

[0014] The preheating section includes a third AC electrode plate and a fourth AC electrode plate installed on the pipe between the third valve and the first reducing joint. A second transformer is connected between the third AC electrode plate and the fourth AC electrode plate by a wire. It also includes a second AC power supply and a second voltage regulator that form a closed loop.

[0015] The test heating section includes a microchannel between a first reducing joint and a second reducing joint. A first AC electrode plate and a second AC electrode plate are arranged on the outer wall of the microchannel. A thermocouple wire unit composed of several sets of thermocouple wires is arranged on the wall of the microchannel between the first AC electrode plate and the second AC electrode plate. A first transformer is connected between the first AC electrode plate and the second AC electrode plate by a wire. The section also includes a first AC power supply and a first voltage regulator to form a closed loop. One end of the differential pressure transmitter is connected to the microchannel between the first reducing joint and the first AC electrode plate through a pipe, and the other end of the differential pressure transmitter is connected to the microchannel between the second reducing joint and the second AC electrode plate through a pipe.

[0016] The second technical solution adopted in this invention is a method for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel. This method utilizes the aforementioned measuring device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel and is implemented according to the following steps:

[0017] Step 1: Turn off the power to the measuring device, disconnect the first valve, the second valve, the third valve, the fourth valve and the fifth valve, purge the test circuit in sections with high-pressure nitrogen, and then connect each valve in sequence. After the connection is completed, purge the test circuit again with high-pressure nitrogen to ensure that the pipeline is unobstructed and leak-free.

[0018] Step 2: Check the circuit to ensure there are no broken wires or leakage; open the first, second, third, fourth, and fifth valves to turn on the data acquisition and display system and ensure that all sensors are working properly.

[0019] Step 3: Pour fluid into the water tank; start the high-pressure constant flow pump and set the required mass flow rate for the test; after the fluid has completed multiple cycles in the test circuit, adjust the back pressure valve to make the test circuit reach the set pressure.

[0020] Step 4: Adjust the first voltage regulator of the test heating section, thereby controlling the first transformer to output the required heating power to the test heating section, so as to maintain a stable heat flux density on the test heating section;

[0021] Step 5: Adjust the second voltage regulator in the preheating section to control the second transformer to output a stable heating power, so that the fluid temperature at the inlet of the test heating section reaches the preset initial inlet temperature. After the test data stabilizes, use the data acquisition and display system to record the relevant test data measured by all monitoring instruments in the measuring device. Then, gradually adjust the heating power of the second voltage regulator in the preheating section to make the inlet temperature of the fluid at the inlet of the test heating section reach the next preset value. After the test data stabilizes, record the relevant test parameters measured by all monitoring instruments in the measuring device again. Repeat the above process until the fluid temperature at the inlet of the test heating section reaches the preset maximum inlet temperature, completing the acquisition and measurement of all test data.

[0022] Step 6: Gradually reduce the heating power on the corresponding pipes of the preheating section and the test heating section. After the power is reduced to 0, turn off the first transformer and the second transformer. Then, adjust the back pressure valve to reduce the pressure of the test circuit to atmospheric pressure. Finally, turn off the data acquisition and display system.

[0023] The beneficial effects of this invention are:

[0024] (1) The greatest advantage of the device for measuring the boiling characteristics of high temperature and high pressure subcooled water in microchannels of the present invention is that the test system is safe and reliable to operate, simple to operate, and can collect the flow heat transfer parameters of subcooled boiling fluid in real time. During the test, the various measurement parameters remain stable, which can effectively ensure the measurement accuracy and reduce the test cost, and provide support for the design optimization of microscale flow heat transfer system.

[0025] (2) The device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel of the present invention can quickly and stably measure up to 10MW / m 2 Grade heat flux density, 10 4 kg / (m 2 With a mass flow rate of ·s and a pressure of 10MPa, it has the advantages of wide measurement range, pressure resistance and strong sealing performance; at the same time, the test pipeline is a micro-channel (with an inner diameter as small as 100μm), which provides support for the design optimization of micro-miniature cooling and heat exchange equipment.

[0026] (3) The device for measuring the boiling characteristics of high temperature and high pressure subcooled water flow in a microchannel of the present invention uses high current and low voltage AC power to directly heat the metal pipe. The advantages of this technology are that the heat flux density is easy to adjust, the response is rapid, the adjustment range is wide, and the distribution is uniform. At the same time, the heating method can quickly and stably adjust the inlet subcooling of the test section, thereby reducing the test time and saving the test cost.

[0027] (4) The device for measuring the boiling characteristics of high temperature and high pressure subcooled water flow in a microchannel of the present invention uses a high pressure constant flow pump, back pressure valve and other devices to coordinate and adjust the test parameters such as flow rate and pressure. Compared with traditional plunger pumps and other equipment, it has the advantages of stable parameters and simple operation.

[0028] (5) All the temperature sensors, differential pressure transmitters, pressure transmitters and mass flow meters used in the measuring device for measuring the boiling characteristics of high temperature and high pressure subcooled water flow in the microchannel of the present invention are synchronously transmitted to the data acquisition system, which can monitor and save in real time. This not only improves the accuracy of the measurement data, but also has an over-temperature alarm function to prevent pipe burst accidents in advance.

[0029] (6) The present invention provides a device for measuring the boiling characteristics of high temperature and high pressure subcooled water flow in a microchannel. It utilizes a regenerator to allow the heated high temperature fluid to exchange heat with the low temperature fluid at the inlet, thereby reducing the power required for the test and effectively reducing the test cost.

[0030] (7) The present invention improves the measurement method of high heat flux subcooled boiling flow and heat transfer characteristics in microchannels by improving the measurement method of high heat flux subcooled boiling flow and heat transfer characteristics, and fills the technical defects of the current measurement of heat transfer characteristics of high heat flux subcooled boiling flow in microchannels. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel according to the present invention.

[0032] Figure 2 This is a schematic diagram of the experimental heating section in the microchannel high-temperature and high-pressure subcooled water flow boiling characteristics measuring device of the present invention;

[0033] Figure 3 This is a schematic diagram of the preheating section in the microchannel high-temperature and high-pressure subcooled water flow boiling characteristics measuring device of the present invention;

[0034] Figure 4 This is a schematic diagram of the regenerator in the microchannel high-temperature and high-pressure subcooled water flow boiling characteristics measuring device of the present invention;

[0035] Figure 5 The examples illustrate the effect of mass flow rate G on the subcooled boiling heat transfer coefficient h.

[0036] Figure 6 This example demonstrates the effect of heat flux density q on the subcooled boiling heat transfer coefficient h.

[0037] Figure 7 This example demonstrates the effect of pressure p on the subcooled boiling heat transfer coefficient h.

[0038] In the diagram, 1. Water tank, 2. First valve, 3. Filter, 4. High-pressure constant flow pump, 5. Mass flow meter, 6. Second valve, 7. First temperature sensor, 8. Regenerator, 9. Second temperature sensor, 10. Third valve, 11. Preheating section, 12. Pressure transmitter, 13. Third temperature sensor, 14. Test heating section, 15. Fourth temperature sensor, 16. Differential pressure transmitter, 17. Fourth valve, 18. Fifth valve, 19. Condenser, 20. Back pressure valve, 21. Float flow meter, 22. Data acquisition and display system, 23. 24. Second AC plate, 25. Thermocouple wire unit, 26. First AC power supply, 27. First voltage regulator, 28. First transformer, 29. Third AC plate, 30. Fourth AC plate, 31. Second AC power supply, 32. Second voltage regulator, 33. Second transformer, 34. Hot fluid inlet end of the regenerator, 35. Hot fluid outlet end of the regenerator, 36. Cold fluid outlet end of the regenerator, 37. Cold fluid inlet end of the regenerator, 38. Inner tube, 39. Outer tube, 40. First reducing joint, 41. Second reducing joint. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0040] This invention provides a device for measuring the boiling characteristics of high-temperature, high-pressure subcooled water flow within a microchannel, such as... Figure 1-4As shown, the system includes a water tank 1, a first valve 2, a filter 3, a high-pressure constant flow pump 4, a mass flow meter 5, a second valve 6, a heating test system, a fifth valve 18, a condenser 19, a back pressure valve 20, and a float flow meter 21, all connected in sequence via pipes. The float flow meter 21 is also connected to the water tank 1 via a pipe. A first temperature sensor 7 is also installed on the pipe between the second valve 6 and the heating unit. The system also includes a data acquisition and display system 22, with the mass flow meter 5, the heating test system, and the float flow meter 21 all connected to the data acquisition and display system 22. The entire device operates in an open-loop system. Fluid flows out of water tank 1, passes through high-pressure constant flow pump 4, mass flow meter 5, regenerator 8, preheating section 11, test heating section 14, condenser 19, back pressure valve 20, and float flow meter 21, before returning to water tank 1. The loop is equipped with valves 2, 6, 10, 17, and 18, dividing the test loop into multiple parts. Data is transmitted to a data acquisition and display system 22 using data acquisition devices such as temperature sensor 7, mass flow meter 5, temperature sensor 9, temperature sensor 13, temperature sensor 15, pressure transmitter 12, and differential pressure transmitter 16. The system stores and displays data changes in real time. The regenerator 8, preheating section 11, test heating section 14, and related connecting pipes are all wrapped with insulation cotton to reduce heat loss.

[0041] The heating test system includes a regenerator 8, a third valve 10, a preheating section 11, a first reducer 40, a test heating section 14, a second reducer 41, and a fourth valve 17, which are connected in sequence through pipes to form a loop. The fourth valve 17 is connected to the regenerator 8 through a pipe. A second temperature sensor 9 is installed on the pipe between the regenerator 8 and the third valve 10. A pressure transmitter 12 and a third temperature sensor 13 are installed on the pipe between the preheating section 11 and the first reducer 40. A fourth temperature sensor 15 is installed on the pipe between the second reducer 41 and the fourth valve 17. The system also includes a differential pressure transmitter 16, which is connected to the inlet and outlet of the test heating section 14 through two pipes. The second temperature sensor 9, the pressure transmitter 12, the third temperature sensor 13, the fourth temperature sensor 15, and the differential pressure transmitter 16 are all connected to a data acquisition and display system 22. The regenerator 8 is an S-shaped double-layered tube, including an inner tube 38 and an outer tube 39. One end of the inner tube 38 is the hot fluid inlet 34, and the other end is the hot fluid outlet 35. The hot fluid inlet 34 is connected to the fourth valve 17 via a pipe, and the hot fluid outlet 35 is connected to the fifth valve 18 via a pipe. The side wall of the outer tube 39 near the hot fluid inlet 34 has the regenerator's cold fluid outlet 36, and the side wall of the outer tube 39 near the hot fluid outlet 35 has the regenerator's cold fluid inlet 37. The regenerator's cold fluid outlet 36 is connected to the third valve 10 via a pipe, and the regenerator's cold fluid inlet 37 is connected to the second valve 6 via a pipe. Figure 4 As shown, the regenerator 8 is a counter-flow heat exchanger. It uses the high-temperature fluid at the hot fluid inlet 34 of the regenerator to reheat the low-temperature fluid at the cold fluid inlet 33 of the regenerator. This can reduce the heat loss of the test, reduce the power required for the condenser 19, the preheating section 11 and the test heating section 14, and reduce the power demand of the test circuit on the heating / cooling equipment, thereby effectively saving test costs.

[0042] Water tank 1 is connected to high-pressure constant flow pump 4 via first valve 2 and filter 3. Filter 3 removes impurities from the fluid, protecting the safety of related instruments and equipment in the circulation loop. High-pressure constant flow pump 4 is easy to operate and can stably control the fluid flow rate in the test loop, keeping the flow rate stable during the test. High-pressure constant flow pump 4 is connected to the cold fluid inlet 37 of the regenerator via mass flow meter 5, second valve 6, and first temperature sensor 7. Mass flow meter 5 measures the mass flow rate of the test loop. First temperature sensor 7 measures the temperature of the cold fluid inlet 37 of the regenerator. Fluid from the cold fluid outlet 36 of the regenerator passes through second temperature sensor 9 and third valve 10 to preheating section 11. Preheating section 11 then passes through third temperature sensor 13 and pressure transmitter 12 into test heating section 14. Second temperature sensor 9 measures the temperature of the cold fluid outlet 36 of the regenerator. Second temperature sensor 9 and first temperature sensor 7 are used together to determine and calculate the heat recovery and heat recovery efficiency of regenerator 8 during the test, facilitating the adjustment and design of test conditions by the test personnel.

[0043] like Figure 1 and Figure 4 As shown, the cold fluid outlet 36 of the regenerator passes sequentially through the preheating section 11, pressure transmitter 12, third temperature sensor 13, test heating section 14, fourth temperature sensor 15, differential pressure transmitter 16, and fourth valve 17 before entering the hot fluid inlet 34 of the regenerator. The preheating section 11 is used to regulate the inlet temperature of the test heating section to ensure its stability. The pressure transmitter 12 and differential pressure transmitter 16 are used to measure the pressure and differential pressure of the test heating section 14, respectively. The third temperature sensor 13 and fourth temperature sensor 15 are used to measure the inlet and outlet fluid temperatures of the test heating section 14, respectively. By combining these four measuring instruments, the relevant parameters of the flow heat transfer characteristics of the subcooled boiling fluid in the test heating section can be effectively and accurately measured synchronously.

[0044] like Figure 1 and Figure 4 As shown, the hot fluid outlet 35 of the regenerator 8 passes through the fifth valve 18, condenser 19, back pressure valve 20 and float flow meter 21 in sequence before returning to the water tank 1, completing one test cycle. The condenser 19 is used to cool the high-temperature fluid to room temperature. The back pressure valve 20 is used to adjust the pressure of the test circuit to ensure the pressure stability of the test circuit. The float flow meter 21 is used to measure the mass flow rate of the fluid and compare it with the mass flow meter 5 to detect the stability of the mass flow rate of the test circuit.

[0045] like Figure 1As shown, valves 2 (first valve), 6 (second valve), 10 (third valve), 17 (fourth valve), and 18 (fifth valve) together divide the test circuit into multiple parts, facilitating maintenance, fault location, component replacement, and pipeline cleaning, effectively saving costs.

[0046] The preheating section 11 includes a third AC electrode plate 29 and a fourth AC electrode plate 30 installed on the pipe between the third valve 10 and the first reducing joint 40. The third AC electrode plate 29 and the fourth AC electrode plate 30 are connected by a second transformer 33 through a wire. It also includes a second AC power supply 31 and a second voltage regulator 32 forming a closed loop. The second voltage regulator 32 and the second transformer 33 transmit power to the third AC electrode plate 29, the fourth AC electrode plate 10 and the pipe through electromagnetic inductance, thereby giving the pipe between the two AC electrode plates a certain heat flux density.

[0047] The test heating section 14 includes a microchannel between the third temperature sensor 1 at the first reducing joint 40 and the fourth temperature sensor 15 at the second reducing joint 41. A first AC electrode 23 and a second AC electrode 24 are disposed on the outer wall of the microchannel. A thermocouple wire unit 25, composed of several sets of thermocouple wires, is disposed on the wall of the microchannel between the first AC electrode 23 and the second AC electrode 24 for measuring the wall temperature of the heated pipe in the test heating section 14. A first transformer 28 is connected between the first AC electrode 23 and the second AC electrode 24 via a wire. It also includes a first AC power supply 26 forming a closed loop and a first voltage regulator 27. The first voltage regulator 27 and the first transformer 28 transmit power to the first AC plate 23, the second AC plate 24 and the pipeline through electromagnetic mutual inductance, thereby giving the pipeline between the two AC plates a certain heat flux density. One end of the differential pressure transmitter 16 is connected to the micro-channel between the first reducing joint 40 and the first AC plate 23 through a pipeline, and the other end of the differential pressure transmitter 16 is connected to the micro-channel between the second reducing joint 41 and the second AC plate 24 through a pipeline.

[0048] The condenser 19 is an integrated air-cooled chiller of model HYA-05ASZ; the pressure transmitter 12 is a Rosemont 3051 differential pressure transmitter; the differential pressure transmitter 16 is a Rosemont 3051 pressure transmitter; and the filter 3 is a Xiongchuan SS-216-30.

[0049] Temperature sensor: T-type armored thermocouple, temperature measurement range 0-300℃; Thermocouple wire: K-type thermocouple wire, temperature measurement range 0-800℃; Back pressure valve 20 pressure adjustment range 0-10MPa; High-pressure constant flow pump 4 is a high-pressure resistant (10MPa) constant flow pump with stable output flow; Data acquisition and display system 22 uses NI acquisition system, chassis model NI DAQ-9178, equipped with NI 9203, NI9213 and NI9220 input modules, acquisition program is LABVIEW, used to collect relevant test data measured by all monitoring instruments in the test device;

[0050] Regenerator: Co-pipe counter-current heat exchanger

[0051] This invention also provides a method for measuring the boiling characteristics of high-temperature, high-pressure subcooled water flow in a microchannel, using the aforementioned measuring device for measuring the boiling characteristics of high-temperature, high-pressure subcooled water flow in a microchannel, specifically implemented according to the following steps:

[0052] Step 1: Turn off the power to the measuring device, disconnect the first valve 2, the second valve 6, the third valve 10, the fourth valve 17 and the fifth valve 18, purge the test circuit in sections with high-pressure nitrogen, and then connect each valve in sequence. After the connection is completed, purge the test circuit again with high-pressure nitrogen to ensure that the pipeline is unobstructed and leak-free.

[0053] Step 2: Check the circuit to ensure there are no broken wires or leakage; open valves 2, 6, 10, 17, and 18 to turn on the data acquisition and display system 22 and ensure that all sensors are working properly.

[0054] Step 3: Introduce fluid into water tank 1; start high-pressure constant flow pump 4 and set the required mass flow rate for the test; after the fluid has completed multiple cycles in the test circuit, adjust back pressure valve 20 to make the test circuit reach the set pressure.

[0055] Step 4: Adjust the first voltage regulator 27 of the test heating section 14, thereby controlling the first transformer 28 to output the required heating power to the test heating section 14, so that the test heating section 14 maintains a stable heat flux density.

[0056] Step 5: Adjust the second voltage regulator 32 of the preheating section 11 to control the second transformer 33 to output a stable heating power, so that the fluid temperature at the fluid inlet of the test heating section 14 reaches the preset initial inlet temperature. After the test data stabilizes, use the data acquisition and display system 22 to record the relevant test data measured by all monitoring instruments in the measuring device. Then, gradually adjust the heating power of the second voltage regulator 32 in the preheating section 11 to make the fluid inlet temperature at the fluid inlet of the test heating section 14 reach the next preset value. After the test data stabilizes, record the relevant test parameters measured by all monitoring instruments in the measuring device again. Repeat the above process until the fluid temperature at the fluid inlet of the test heating section 14 reaches the preset maximum inlet temperature (when the inlet temperature reaches the preset maximum inlet temperature, the outlet temperature of the test heating section 14 will reach the limit value, that is, the temperature measured by the fourth temperature sensor is close to the temperature of the supercooled boiling saturation point under the current working conditions), and complete the acquisition and measurement of all test data.

[0057] Step six: Gradually reduce the heating power on the corresponding pipes of the preheating section 11 and the test heating section 14. After the power is reduced to 0, turn off the first transformer 28 and the second transformer 33. Then, adjust the back pressure valve 20 to reduce the pressure of the test circuit to normal pressure. Finally, turn off the data acquisition and display system 22.

[0058] Example

[0059] To study the boiling characteristics of supercooled water under high temperature and pressure, measurements are required, including pressure p, pressure difference Δp, mass flow rate G, and the outer wall temperature T of the experimental heating section. w,out The inlet and outlet fluid temperatures T of the test heating section in and T out The measured parameters were then analyzed; subsequently, relevant heat transfer formulas were used to calculate these directly measured parameters, obtaining the subcooled boiling heat transfer coefficient h, the heat flux density q of the experimental heating section, and the inner wall temperature T. w,in The calculation parameters, including those for high-temperature and high-pressure subcooled water, were used to study and analyze the boiling characteristics of the water flow.

[0060] Using the microchannel high-temperature and high-pressure subcooled water flow boiling characteristic measurement device and method provided by this invention, experiments were conducted on deionized water under nine different operating conditions to obtain measurement and calculation parameters of high-temperature and high-pressure water in a pipe with an inner diameter of 1 mm. The heat transfer characteristics of high-temperature and high-pressure subcooled water flow boiling were thus obtained. The nine different operating conditions are as follows: Figure 5-7 As shown, Figure 5 The operating conditions are (1) p = 4.0 MPa, G = 3200 kg / (m²) 2 ·s),q=5.0MW / m 2; (2)p=4.0MPa, G=3700kg / (m 2 ·s),q=5.0MW / m 2 ; (3)p=4.0MPa, G=4200kg / (m 2 ·s),q=5.0MW / m 2 ; Figure 6 The operating conditions are respectively (1) p=4.2MPa, G=8000kg / (m 2 ·s),q=10.0MW / m 2 ; (2)p=4.2MPa, G=8000kg / (m 2 ·s),q=7.5MW / m 2 ; (3)p=4.2MPa, G=8000kg / (m 2 ·s),q=12.5MW / m 2 ; Figure 7 The operating conditions are (1) p = 3.0 MPa, G = 2500 kg / (m²) 2 ·s),q=5.0MW / m 2 ; (2)p=4.0MPa, G=2500kg / (m 2 ·s),q=5.0MW / m 2 ; (3)p=5.0MPa, G=2500kg / (m 2 ·s),q=5.0MW / m 2 .

[0061] Figure 5-7 Inner wall temperature T w,in By comparing the form of the subcooled boiling heat transfer coefficient h, the effects of pressure p, mass flow rate G, and heat flux density q in the experimental heating section on the subcooled boiling heat transfer coefficient h are accurately presented. Figure 5-7 It is known that as the temperature rises, the fluid gradually transitions from a single-phase state to a subcooled boiling state, continuously increasing the heat transfer coefficient and enhancing heat transfer performance. Simultaneously, pressure, mass flow rate, and heat flux density all affect the fluid's heat transfer performance. Under the same wall temperature conditions, increasing the mass flow rate and decreasing the pressure and heat flux density can all increase the heat transfer coefficient, thereby enhancing heat exchange. These nine sets of experiments also demonstrate that the device of this invention can stably and accurately obtain high-heat-flux subcooled boiling flow and heat transfer characteristics (10MW / m²) within a microchannel. 2 Grade heat flux density, 10 4 kg / (m 2 The measurement results (at mass flow rates of 10 MPa and pressures of 10 MPa) have significant engineering application value.

[0062] The device of this invention can accurately measure the flow heat transfer characteristics of high-heat-flux subcooled boiling. Compared with existing devices, it has many advantages such as low experimental cost, simple operation, stable measurement parameters, and stable and safe operation. This invention improves the measurement method of high-heat-flux subcooled boiling flow and heat transfer characteristics, and fills the technical defects in the current measurement of high-heat-flux subcooled boiling flow heat transfer characteristics in microchannels.

Claims

1. A device for measuring the boiling characteristics of high-temperature, high-pressure subcooled water flow in a microchannel, characterized in that, The system includes a water tank (1), a first valve (2), a filter (3), a high-pressure constant flow pump (4), a mass flow meter (5), a second valve (6), a heating test system, a fifth valve (18), a condenser (19), a back pressure valve (20), and a float flow meter (21), which are connected in sequence by pipes. The float flow meter (21) is also connected to the water tank (1) by a pipe. A first temperature sensor (7) is also installed on the pipe between the second valve (6) and the heating unit. The system also includes a data acquisition and display system (22), and the mass flow meter (5), the heating test system, and the float flow meter (21) are all connected to the data acquisition and display system (22). The heating test system includes a regenerator (8), a third valve (10), a preheating section (11), a first reducing joint (40), a test heating section (14), a second reducing joint (41), and a fourth valve (17) connected in sequence to form a loop. The fourth valve (17) is connected to the regenerator (8) via a pipe. A second temperature sensor (9) is installed on the pipe between the regenerator (8) and the third valve (10). A pressure transmitter (12) and a third reducing joint (40) are installed on the pipe between the preheating section (11) and the first reducing joint (40). Temperature sensor (13); a fourth temperature sensor (15) is installed on the pipeline between the second reducer (41) and the fourth valve (17); a differential pressure transmitter (16) is also included, which is connected to the inlet end of the test heating section (14) and the outlet end of the test heating section (14) through two pipelines respectively; the second temperature sensor (9), pressure transmitter (12), third temperature sensor (13), fourth temperature sensor (15) and differential pressure transmitter (16) are all connected to the data acquisition and display system (22); The regenerator (8) is an S-shaped double-layered tube, including an inner tube (38) and an outer tube (39). One end of the inner tube (38) is the hot fluid inlet end (34), and the other end of the inner tube (38) is the hot fluid outlet end (35). The hot fluid inlet end (34) is connected to the fourth valve (17) through a pipe, and the hot fluid outlet end (35) is connected to the fifth valve (18) through a pipe. The side wall of the outer tube (39) near the hot fluid inlet end (34) is provided with the cold fluid outlet end (36) of the regenerator, and the side wall of the outer tube (39) near the hot fluid outlet end (35) is provided with the cold fluid inlet end (37) of the regenerator. The cold fluid outlet end (36) of the regenerator is connected to the third valve (10) through a pipe, and the cold fluid inlet end (37) of the regenerator is connected to the second valve (6) through a pipe.

2. The device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel according to claim 1, characterized in that, The preheating section (11) includes a third AC electrode plate (29) and a fourth AC electrode plate (30) installed on the pipe between the third valve (10) and the first reducing joint (40). A second transformer (33) is connected between the third AC electrode plate (29) and the fourth AC electrode plate (30) by a wire. It also includes a second AC power supply (31) and a second voltage regulator (32) forming a closed loop.

3. The device for measuring the boiling characteristics of high-temperature and high-pressure subcooled water flow in a microchannel according to claim 1, characterized in that, The test heating section (14) includes a microchannel between the first reducing joint (40) and the second reducing joint (41). The outer wall of the microchannel is provided with a first AC electrode plate (23) and a second AC electrode plate (24). The wall of the microchannel between the first AC electrode plate (23) and the second AC electrode plate (24) is provided with a thermocouple wire unit (25) composed of several sets of thermocouple wires. The first AC electrode plate (23) and the second AC electrode plate (24) are connected by a wire to a first transformer (28). The microchannel also includes a first AC power supply (26) forming a closed loop and a first voltage regulator (27). One end of the differential pressure transmitter (16) is connected to the microchannel between the first reducing joint (40) and the first AC electrode plate (23) through a pipe. The other end of the differential pressure transmitter (16) is connected to the microchannel between the second reducing joint (41) and the second AC electrode plate (24) through a pipe.

4. A method for measuring the boiling characteristics of high-temperature, high-pressure subcooled water flow in a microchannel, using the measuring device for measuring the boiling characteristics of high-temperature, high-pressure subcooled water flow in a microchannel as described in any one of claims 1-3, characterized in that... The specific steps are as follows: Step 1: Turn off the power of the measuring device, disconnect the first valve (2), the second valve (6), the third valve (10), the fourth valve (17) and the fifth valve (18), purge the test circuit in sections with high-pressure nitrogen, and then connect each valve in sequence. After the connection is completed, purge the test circuit again with high-pressure nitrogen to ensure that the pipeline is unobstructed and leak-free. Step 2: Check the circuit to ensure there are no broken wires or leakage; open the first valve (2), the second valve (6), the third valve (10), the fourth valve (17) and the fifth valve (18), and turn on the data acquisition and display system (22) to ensure that each sensor works normally; Step 3: Pass fluid into water tank (1); Start the high-pressure constant flow pump (4) and set the mass flow rate required for the test; after the fluid has completed multiple cycles in the test circuit, adjust the back pressure valve (20) so that the test circuit reaches the set pressure; Step 4: Adjust the first voltage regulator (27) of the test heating section (14), thereby controlling the first transformer (28) to output the required heating power to the test heating section (14), so that the test heating section (14) maintains a stable heat flux density; Step 5: Adjust the second voltage regulator (32) of the preheating section (11) to control the second transformer (33) to output a stable heating power so that the fluid temperature at the fluid inlet of the test heating section (14) reaches the preset initial inlet temperature. After the test data stabilizes, use the data acquisition and display system (22) to record the relevant test data measured by all monitoring instruments in the measuring device at this time. Then, gradually adjust the heating power of the second voltage regulator (32) in the preheating section (11) so that the fluid inlet temperature at the fluid inlet of the test heating section (14) reaches the next preset value. After the test data stabilizes, record the relevant test parameters measured by all monitoring instruments in the measuring device again. Repeat the above process until the fluid temperature at the fluid inlet of the test heating section (14) reaches the preset maximum inlet temperature, and complete the acquisition and measurement of all test data. Step 6: Gradually reduce the heating power on the corresponding pipes of the preheating section (11) and the test heating section (14). After the power is reduced to 0, turn off the first transformer (28) and the second transformer (33). Then, adjust the back pressure valve (20) to reduce the pressure of the test circuit to normal pressure. Finally, turn off the data acquisition and display system (22).

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