A two-phase flow experimental measurement system and method for narrow rectangular channels

Abstract

The application discloses a two-phase flow experimental measurement system of a narrow rectangular channel and a measurement method thereof, and comprises an experimental device, wherein the experimental device comprises a stainless steel sheet, a stainless steel boss base, a G10 glass fiber shell, quartz glass and a stainless steel pressing plate; the shell is provided with a hollow groove and two water containing cavities, the hollow groove is connected with the water containing cavities through a connecting groove, and the two water containing cavities are respectively provided with a water inlet and a water outlet; the stainless steel sheet and the stainless steel boss base are installed in the hollow groove; the hollow groove, the connecting groove and the quartz glass form a narrow rectangular channel; the quartz glass is fixed on the narrow rectangular channel through the stainless steel pressing plate; and the stainless steel sheet and the stainless steel boss base are provided with a plurality of temperature measuring holes. The stainless steel sheet with different surface characteristics is used to respectively carry out flow boiling heat transfer characteristic experiments in the micro channel, flow boiling heat transfer pressure drop data of different surfaces are compared, and specific influences of surface modification on flow boiling heat transfer pressure drop in the micro channel are obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of two-phase flow measurement, in particular to a two-phase flow experimental measurement system and method for a narrow rectangular channel. BACKGROUND

[0002] With the vigorous development of microelectronic technology, electronic device size is getting smaller and smaller, and integration is getting higher and higher. High performance and miniaturization together lead to the power of the electronic device being higher and higher. Microchannels with high surface area / volume ratio greatly improve the heat dissipation capacity of electronic devices due to high efficient boiling heat transfer capacity. Currently, the three main ways to strengthen heat transfer in microchannels are: microchannel structure change, heat transfer surface modification and flow medium change. The main purpose of heat transfer enhancement is to reduce the boiling initiation point, improve the heat transfer coefficient, increase the critical heat flux density, reduce the pressure drop loss, etc. There are numerous studies on the modification of the heat transfer surface in the microchannel. In general, surface modification changes the roughness, wettability, porosity, etc. of the surface, thereby affecting the generation, detachment, aggregation and discharge of bubbles in the microchannel, resulting in different bubble dynamics phenomena, and ultimately affecting the heat transfer and pressure drop characteristics in the microchannel. However, the conclusions of different scholars are quite different. Mechanically, the influence of surface modification in the microchannel is not clear. Therefore, in order to explore the flow boiling heat transfer and pressure drop characteristics of different surfaces in a narrow rectangular channel, it is necessary to propose a two-phase flow experimental measurement system and method for a narrow rectangular channel. SUMMARY

[0003] In view of the above shortcomings of the prior art, the present application provides a two-phase flow experimental measurement system and method for exploring the flow boiling heat transfer and pressure drop characteristics of different surfaces in a narrow rectangular channel.

[0004] To achieve the above-mentioned application purposes, the technical scheme adopted by the present application is:

[0005] The utility model provides a kind of two-phase flow experimental measurement system of narrow rectangular channel, including deionized water storage tank, deionized water storage tank is connected with gas-removing storage tank, gas-removing storage tank inside is provided with storage tank heating rod, deionized water storage tank and gas-removing storage tank between being provided with peristaltic pump, the water side of gas-removing storage tank is connected with filtration branch and filtration contrast branch, filtration branch and filtration contrast branch are also connected with gear pump, filtration branch is provided with filter and filter switch valve, filtration contrast branch is provided with no filter switch valve;Gear pump is connected with adjusting loop and mass flowmeter, adjusting loop is connected with gas-removing storage tank, adjusting loop is also provided with adjusting switch valve, and adjusting switch valve is electrically connected with gear pump;Mass flowmeter is connected with constant-temperature preheating pot, constant-temperature preheating pot is connected with experimental device, and the water outlet end of experimental device is connected with gas-removing storage tank;Experimental device is provided with a plurality of temperature measuring points, temperature measuring points are installed with temperature sensor, and narrow rectangular channel and electroplated layer heating surface are also provided in experimental device.

[0006] Further, it also includes high-speed camera, light source, data acquisition end and direct-current direct-current power heater, high-speed camera, light source are installed above experimental device, direct-current direct-current power heater is installed at the bottom of experimental device, and data acquisition end is connected with a plurality of temperature sensors.

[0007] Further, one-way valve and switch valve are arranged between experimental device and gas-removing storage tank, between gas-removing storage tank and filtration branch, between constant-temperature preheating pot and experimental device;One-way valve is also arranged between filtration branch and gear pump, between mass flowmeter and constant-temperature preheating pot and on adjusting loop.

[0008] Further, the water outlet end of constant-temperature preheating pot is provided with preheating pot thermocouple.

[0009] Further, experimental device includes stainless steel sheet, stainless steel boss, G10 glass fiber shell, quartz glass and stainless steel pressing plate;Stainless steel sheet is electroplated with electroplated layer with different surface characteristics;G10 glass fiber shell is provided with hollow slot for mounting stainless steel sheet and two water containing cavities, and the hollow slot is connected with the water containing cavities through connecting groove, and the two water containing cavities are also respectively provided with water inlet and water outlet;Stainless steel sheet is fixed on stainless steel boss, and stainless steel sheet and stainless steel boss are installed in hollow slot;Hollow slot, connecting groove and quartz glass form narrow rectangular channel;Quartz glass is fixed on narrow rectangular channel through stainless steel pressing plate;Stainless steel sheet side is provided with a plurality of upper temperature measuring point holes, and stainless steel boss is provided with a plurality of lower temperature measuring point holes;Shell is provided with temperature measuring corresponding holes communicated with upper temperature measuring point holes and lower temperature measuring point holes, and temperature sensor is installed in upper temperature measuring point holes and lower temperature measuring point holes.

[0010] Further, the two water-containing cavities are provided with thermocouple mounting holes, and water-containing cavity thermocouples are mounted in the two thermocouple mounting holes; the two water-containing cavities are also respectively provided with pressure gauge mounting holes and pressure transmitter mounting holes, the pressure sensor is mounted in the pressure gauge mounting hole, and the pressure transmitter is mounted in the pressure transmitter mounting hole.

[0011] Further, the stainless steel boss base comprises a base and a boss, a plurality of lower temperature measuring point holes are arranged on the boss, and two communicating stud mounting through holes are arranged on the base and the boss; the bottom of the stainless steel sheet is provided with two sheet studs and two stud nuts, and the stainless steel sheet and the stainless steel boss base are connected through the sheet stud and the stud nut.

[0012] Further, a plurality of mounting through holes are arranged on the shell and the stainless steel pressing plate in correspondence, and the shell and the stainless steel pressing plate are connected through a plurality of bolt members.

[0013] Further, the side edge of the stainless steel sheet is provided with three upper temperature measuring point holes, and the stainless steel boss base is provided with six lower temperature measuring point holes, which are divided into two rows and three columns and aligned with the three upper temperature measuring point holes.

[0014] A measurement method of a two-phase flow experimental measurement system of a narrow rectangular channel:

[0015] S1: Assemble the experimental device, install the measurement system, and connect the experimental device to the experimental loop of the measurement system, and adjust the measurement system; specifically including:

[0016] S11: Open the peristaltic pump to pump high-purity deionized water in the deionized water storage tank into the degassing storage tank, and after the degassing storage tank is filled with high-purity deionized water, control the peristaltic pump to run in reverse to exhaust the degassing storage tank;

[0017] S12: Use the storage tank heating rod in the degassing storage tank to heat and boil the deionized water for 30 minutes to remove non-condensable gases in the high-purity deionized water; then turn off the peristaltic pump and stop the heating of the storage tank heating rod, and allow the high-purity deionized water to cool naturally;

[0018] S13: Before the test starts, open and close the switch valve in the measurement system to make the high-purity deionized water circulate in the entire measurement system loop; close the unfiltered switch valve and the adjusting switch valve, and open the remaining switch valves in the measurement system loop to complete the adjustment of the measurement system;

[0019] S2: After adjusting the measurement system, make it run normally, and start the two-phase flow experiment in the narrow rectangular channel after the experimental device is not leaking;

[0020] S3: Set the mass flow valve value Q F , the inlet temperature Tin ; set the mass flow threshold Q of high-purity deionized water through the mass flow meter F , set the inlet temperature T of the experimental device through the constant temperature preheating pot in ;

[0021] S4: turn on the straight cylinder type direct current power heater, heat the bottom of the experimental device by using the straight cylinder type direct current power heater, and finally conduct heat to the electroplated heating surface in the experimental device through heat transfer, and heat the high-purity deionized water in the narrow rectangular channel through the electroplated heating surface;

[0022] S5: adjust the heating power of the straight cylinder type direct current power heater every 3 minutes, and collect data once, until the bubbles generated by the boiling of the high-purity deionized water in the experimental device flow back to occupy the entire flow channel; and use a high-speed camera to shoot and record the flow of the high-purity deionized water in the narrow rectangular channel through the quartz glass; use the data acquisition end to cooperate with the signal express software to collect a plurality of temperature and pressure data on the experimental device; and use the Bronkhorst software to collect the mass flow Q F , so as to collect the electroplated layer heating surface characteristic data;

[0023] S6: replace the different electroplated layer heating surfaces on the experimental device, repeat steps S2-S5 to perform experiments, and obtain the surface characteristic data of different electroplated layer heating surfaces.

[0024] The beneficial effects of the present application are:

[0025] The present application plating chromium on the surface of the stainless steel sheet by electroplating and anodizing, and forming chromium plating layers with different surface characteristics on the surface of the stainless steel sheet by different electroplating times, and using the chromium plating layers with different surface characteristics to respectively perform flow boiling heat transfer characteristic experiments in the microchannel, comparing the flow boiling heat transfer pressure drop data of different surfaces, and obtaining the specific influence of surface modification on the flow boiling heat transfer pressure drop in the microchannel.

[0026] The stainless steel sheet in the present application is convenient to manufacture, has low cost, and can be repeatedly replaced with a new surface, and the influence of the surface characteristics of the heat transfer surface in the microchannel on the flow boiling heat transfer is explored, and since the number of controllable surfaces is increased, more experimental data of different surface characteristics can be compared, and after analyzing and comparing the experimental results, the mechanism of the influence of the surface modification on the flow boiling heat transfer mechanism in the microchannel can be more accurately obtained.

[0027] The present application can obtain several chromium-plated heating surfaces with different surface characteristics by preparing several stainless steel sheets with the same size, respectively performing different degrees of electroplating and anodic oxidation processes, and replacing the chromium-plated heating surfaces when the entire measurement system is used to perform experiments with experimental devices, so that two-phase flow experiments of flow boiling heat transfer pressure drop characteristics of different surfaces in the entire narrow rectangular channel become simpler.

[0028] The two-phase flow experiment measurement system and the measurement method can be used to explore flow boiling heat transfer pressure drop characteristics of different surfaces in the narrow rectangular channel, and analyze the specific influence of surface modification on flow boiling heat transfer pressure drop in the narrow rectangular channel by combining experimental phenomena and surface characteristic data. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the measurement system of the present application;

[0030] Figure 2 It is a schematic diagram of the overall shape structure of the experimental device of the present application;

[0031] Figure 3 It is a right view of the experimental device of the present application;

[0032] Figure 4 It is a structural schematic diagram of the measurement system of the present application;

[0033] Figure 5 It is a schematic diagram of the shape structure of the stainless steel sheet;

[0034] Figure 6 It is a schematic diagram of the shape structure of the stainless steel boss base;

[0035] Figure 7 It is a schematic diagram of part of the shape structure of the experimental device of the present application;

[0036] Figure 8 It is a schematic diagram of the shape structure of the shell;

[0037] Figure 9 It is a schematic diagram of the hot and cold flow cross section corresponding to the center 9 temperature measuring points;

[0038] Figure 10 It is a raw data diagram of chromium-plated stainless steel sheet, stainless steel boss base and inlet and outlet water temperature;

[0039] Figure 11 It is a diagram of 9 temperature measuring points and inlet and outlet water temperature changing with average effective heat flow;

[0040] Figure 12 It is a subcooled boiling curve diagram of three temperature measuring points on the stainless steel sheet and average effective heat flow;

[0041] Figure 13 Fig. 12 is a graph of local heat transfer coefficient versus local heat flux for the left, middle and right positions;

[0042] Figure 14 Fig. 13 is a graph of average heat transfer coefficient versus average effective heat flux;

[0043] Figure 15 Fig. 14 is a graph of fluctuation of pressure difference smoothing signal within 30s when reverse flow periodic fluctuation occurs;

[0044] Figure 16 Fig. 15 is a graph of frequency spectrum of periodic fluctuation pressure difference smoothing signal after FFT signal processing;

[0045] Figure 17 Fig. 16 is a graph of fluctuation of mass flow within 60s when reverse flow periodic fluctuation occurs;

[0046] Figure 18 Fig. 17 is a graph of frequency spectrum of periodic fluctuation mass flow data after FFT signal processing

[0047] The main component symbols in the figures are explained as follows:

[0048] 1. stainless steel sheet; 11. sheet stud; 12. stud nut; 13. upper temperature measuring point hole;

[0049] 2. stainless steel boss base; 21. base; 22. boss; 23. lower temperature measuring point hole; 24. stud mounting through hole;

[0050] 3. shell; 31. mounting through hole; 32. water inlet; 33. water outlet; 34. thermocouple mounting hole; 35. pressure gauge mounting hole; 36. pressure transmitter mounting hole; 37. temperature measuring corresponding hole; 38. hollow groove; 39. connecting groove; 30. water containing cavity;

[0051] 4. quartz glass; 5. stainless steel pressing plate; 6. connecting bolt; 7. connecting nut;

[0052] 81. high-speed camera; 82. light source; 83. experimental device; 84. constant temperature preheating pot; 85. mass flowmeter; 86. deionized water storage tank; 87. gear pump; 88. filter; 89. degassing type storage tank; 810. peristaltic pump; 811. direct current type direct current power heater; 812. data acquisition end; 813. straight cylinder type direct current power heater; 814. storage tank heating rod. DETAILED DESCRIPTION

[0053] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0054] like Figure 1 As shown, the two-phase flow experimental measurement system with a narrow rectangular channel includes a deionized water storage tank 86, which is connected to a deaeration-type water storage tank 89. A water storage tank heating rod 814 is installed inside the deionized water storage tank 89. A peristaltic pump 810 is installed between the deionized water storage tank 86 and the deaeration-type water storage tank 89. A filtration branch and a filtration comparison branch are connected to the outlet side of the deaeration-type water storage tank 89. A gear pump 87 is also connected to the filtration branch. A filter 88 and a filter switching valve are installed on the filtration branch, and a non-filtration switching valve is installed on the filtration comparison branch. The gear pump 87 is connected to a regulating circuit and a mass flow meter 85. The regulating circuit is connected to the deaeration-type water storage tank 89, and a regulating switching valve is also installed on the regulating circuit. The regulating switching valve is electrically connected to the gear pump 87. The mass flow meter 85 is connected to a constant temperature preheating pot 84, the constant temperature preheating pot 84 is connected to an experimental device 83, and the outlet of the experimental device 83 is connected to a degassing water storage tank 89. Several temperature measuring points are set on the experimental device 83, and temperature sensors are installed on the temperature measuring points. The experimental device 83 is also equipped with a narrow rectangular channel and a chromium-plated heating surface.

[0055] The measurement system also includes a high-speed camera 81, a light source 82, a data acquisition terminal 812, and a DC power supply heater 811. The high-speed camera 81 and the light source 82 are mounted on the top of the experimental device 83, the DC power supply heater 811 is mounted on the bottom of the experimental device 83, and the data acquisition terminal 812 is connected to a thermocouple on the experimental device 83.

[0056] One-way valves and on / off valves are installed between experimental device 83 and deaeration water storage tank 89, between deaeration water storage tank 89 and filtration branch, and between constant temperature preheating pot 84 and experimental device 83. One-way valves are also installed between filtration branch and gear pump 87, between mass flow meter 85 and constant temperature preheating pot 84, and on the regulating circuit. A preheating pot thermocouple is installed at the outlet of constant temperature preheating pot 84 to measure the temperature of the high-purity deionized water before it enters experimental device 83.

[0057] like Figure 2 , 3As shown in Figure 4, the two-phase flow experimental apparatus in a narrow rectangular channel includes a stainless steel sheet 1, a stainless steel boss base 2, an outer shell 3, a quartz glass 4, and a stainless steel pressure plate 5. The stainless steel sheet 1 is fixedly mounted on the stainless steel boss base 2, and the quartz glass 4 is fixed to the top of the outer shell 3, secured to the outer shell 3 by the stainless steel pressure plate 5, connecting bolts 6, and connecting nuts 7. The stainless steel sheet 1 is coated with a chromium layer; different chromium coatings are applied to different stainless steel sheets 1 to explore the boiling heat transfer pressure drop characteristics of different surfaces. The outer shell 3 has a perforated groove 38 for mounting the stainless steel sheet 1 and two water-containing chambers 30. The perforated groove 38 and the water-containing chambers 30 are connected by a connecting groove 39. The two water-containing chambers 30 are also equipped with an inlet 32 ​​and an outlet 11, respectively. The stainless steel sheet 1 is fixed to the stainless steel boss base 2, and the stainless steel sheet 1 and the stainless steel boss base 2 are installed in the perforated groove 38; the quartz glass 4 is fixed to the narrow rectangular channel by the stainless steel pressure plate 5. Figure 3 The hollowed-out groove 38, the connecting groove 39, and the quartz glass form the narrow rectangular channel required for the experiment. The heating section of the narrow rectangular channel is 60mm long, 10mm wide, and 1mm high.

[0058] like Figure 5 As shown, the stainless steel sheet 1 includes two sheet studs 11 and two stud nuts 12 located at its bottom. The stainless steel sheet 1 is 60mm long, 10mm wide, and 3mm high. Three upper temperature measuring holes 13, each 1mm in diameter and 5mm deep, are located on the side of the stainless steel sheet 1. These holes are used to mount temperature sensors, preferably thermocouples. The three upper temperature measuring holes 13 are at the same height, with the center of each hole 1mm from the upper surface. The measured temperature is approximately equal to the surface temperature of the corresponding vertical position of the stainless steel sheet 1. The distance between the three upper temperature measuring holes 13 is 10mm, and the left and right upper temperature measuring holes 13 are 20mm from each end of the stainless steel sheet. The two sheet studs 11 are located at the bottom of the stainless steel sheet 1, and stud nuts 12 are mounted on the sheet studs 11. The stainless steel sheet 1 is connected to the stainless steel boss base 2 via the sheet studs 11 and stud nuts 12.

[0059] like Figure 6As shown in the figure, the stainless steel boss base 2 comprises a base 21 and a boss 22, and a plurality of lower temperature measuring point holes 23 are arranged on the boss 22. The base 21 and the boss 22 are provided with two communicating threaded hole mounting holes 24. The stainless steel boss base 2 is used for heat conduction and conversion of local heat flow. The base 21 is 60 mm long, 30 mm wide and 4 mm high. The boss is 7 mm high. The upper surface of the boss 22 is the same size as the stainless steel sheet. The boss 22 has six 1 mm lower temperature measuring point holes 23 on the side. The hole depth is 5 mm. The left and right horizontal distance of the lower temperature measuring point holes 23 is 10 mm. The upper and lower spacing is 4 mm. The center of the uppermost row of lower temperature measuring point holes 23 is 2 mm away from the boss surface. The lower temperature measuring point holes 23 are used to install temperature sensors. The temperature sensor is preferably a thermocouple. The boss 22 has two threaded hole mounting holes 24 with a diameter of 6 mm, which are used to penetrate the sheet threaded hole 11. The threaded hole mounting hole 24 is fastened below the boss 22 by a threaded cap 12, so that the stainless steel sheet 1 and the stainless steel boss base 2 form the experimental section body, as shown in the figure. Figure 7 When different surface experiments are needed, only different surface characteristic stainless steel sheets 1 need to be replaced, which saves cost and causes little damage to the experimental section body.

[0060] As shown in the figure, Figure 8As shown, the role of the shell 3 is to keep warm and form the narrow rectangular channel required by the experiment. The material of the shell 3 is preferably G10 glass fiber, the length of the shell 3 is 120mm, the width is 60mm, and the height is 15mm; the upper surface of the shell 3 is provided with 8 vertical through mounting holes 31, the diameter of the mounting hole 31 is 6mm, which is used to cooperate with the connecting bolt 6, the connecting nut 7 and the quartz glass 4. There are 6mm threaded holes on the left and right sides, one for the water inlet 32 and the other for the water outlet 33. The front side is provided with two thermocouple mounting holes 34, both of which are installed with water cavity thermocouples for measuring the inlet and outlet water temperature. The front side is provided with a pressure gauge mounting hole 35 and a pressure transmitter mounting hole 36, the pressure sensor is installed in the pressure gauge mounting hole 35, and the pressure transmitter is installed in the pressure transmitter mounting hole 36. The pressure gauge mounting hole 35 is used to measure the inlet and outlet pressure, and the pressure transmitter mounting hole 36 is used to measure the pressure difference between the inlet and outlet; the thermocouple mounting hole 34, the pressure gauge mounting hole 35 and the pressure transmitter mounting hole 36 are all 6mm threaded holes. There are 9 temperature measuring holes 37 with a diameter of 1mm on the front side of the shell 3, which are used to install thermocouples, and the positions of the temperature measuring holes 37 correspond to the positions of the temperature measuring holes on the body of the experimental section; the 9 temperature measuring holes 37 are arranged in 3 rows and 3 columns, the distance between the first row of temperature measuring holes 37 and the upper surface of the shell is 2mm, the distance between each row of temperature measuring holes 37 is 4mm, and the distance between the last row of temperature measuring holes 37 and the bottom surface of the shell 3 is 5mm. The length of the hollow groove 38 is 60mm, the width is 10mm, and the two water cavities 30 are in a three-dimensional shape, with a length, width and height of 10mm. The data measured in the whole experiment are the temperatures of the 9 temperature measuring holes, the water temperature of the water inlet 32, the water temperature of the outlet 33, the pressure of the water inlet 33 and the pressure difference after passing through the experimental device 83.

[0061] The experimental method of the two-phase flow experimental measurement system includes the following steps:

[0062] S1: Assemble the experimental device 83, install the measurement system, connect the experimental device 83 to the experimental loop of the measurement system, and adjust the measurement system; specifically including:

[0063] S11: Turn on the peristaltic pump 810 to pump high-purity deionized water in the deionized water storage tank 86 into the degassing storage tank 89, and after adding high-purity deionized water to the degassing storage tank 89, control the peristaltic pump 810 to operate in reverse to exhaust the degassing storage tank 89;

[0064] S12: Use the storage tank heating rod 814 in the degassing storage tank 89 to heat and boil the high-purity deionized water for 30 minutes to remove non-condensable gases in the high-purity deionized water; then turn off the peristaltic pump 810 and stop the heating of the storage tank heating rod 814 to allow the high-purity deionized water to cool naturally;

[0065] S13: Before the experiment, the high-purity deionized water is circulated in the whole measuring system by opening and closing the switch valve in the measuring system; the unfiltered switch valve and the adjusting switch valve are closed, and the rest of the switch valves in the measuring system are opened, and the measuring system is adjusted;

[0066] The specific flow process of high-purity deionized water is as follows: the high-purity deionized water flows out from the degassing storage tank 89, first passes through the filter 88 to remove air, and then flows to the experimental device 83 under the action of the gear pump 87, passing through the mass flow meter 85 and the constant temperature preheating pot 84 in the process; the mass flow meter 85 and the gear pump 87 jointly control the size of the mass flow, when the actual flow value Q S of the mass flow meter 85 is greater than the mass flow valve value Q F of the system, the mass flow meter 85 gives a negative feedback signal to the gear pump 87, and the gear pump 87 adjusts the opening of the adjusting switch valve in the branch, so that part of the high-purity deionized water flows back to the degassing storage tank 89 from the adjusting branch, thereby realizing the control of the flow of the high-purity deionized water flowing into the experimental device 83 by the mass flow meter 85; the high-purity deionized water flows out from the mass flow meter 85 and flows into the constant temperature oil bath pot 84, the spiral heating pipeline in the constant temperature oil bath pot 84 heats the high-purity deionized water flowing through it, and an oil bath pot thermocouple is arranged at the outlet pipeline of the constant temperature oil bath pot 84 to measure the outlet temperature H out of the constant temperature oil bath pot 84, i.e. the inlet temperature T in of the experimental device 83;

[0067] S2: After adjusting the normal operation of the measuring system and ensuring that the experimental device 83 does not leak, the two-phase flow experiment in the narrow rectangular channel is started;

[0068] S3: The mass flow valve value Q F of the mass flow meter 85 is set, and the inlet temperature T in of the experimental device 83 is set; the mass flow valve value Q F of the high-purity deionized water is set by the mass flow meter 85, and the inlet temperature T in of the experimental device 83 is set by the constant temperature preheating pot 84;

[0069] S4: The straight cylinder type direct current power heater 813 is turned on to heat the bottom of the experimental device 83, and through heat transfer, the heat is finally conducted to the chromium plating heating surface in the experimental device 83, and the high-purity deionized water in the narrow rectangular channel is heated through the chromium plating heating surface; after the high-purity deionized water transported to the narrow rectangular channel of the experimental device 83 carries away the heat, the temperature of the high-purity deionized water continues to rise, and phase change occurs to generate steam, and the steam-water mixed high-purity deionized water flows back to the degassing storage tank 815 for cooling;

[0070] S5: Adjust the heating power of the cylindrical DC power heater 813 every 3 minutes and collect data once, until the high-purity deionized water in the experimental apparatus 83 boils dry; use a high-speed camera 81 to record the flow of high-purity deionized water in the narrow rectangular channel through the quartz glass 4; use the data acquisition terminal 812 with Signal Express software to collect several temperature and pressure data on the experimental apparatus 83, and use Bronkhorst software to collect the mass flow rate Q. F This allows for the collection of characteristic data of the chromium-plated heating surface.

[0071] S6: Replace the heating surface with different chromium plating on the experimental device 83, and repeat steps S2-S5 to obtain surface characteristic data of different chromium plating heating surfaces.

[0072] like Figure 9 The figure shows the positional relationship between the nine temperature measuring points at the center of the experimental section and the cold and hot flows. Figure 9 The dashed arrows represent the direction of cold flow, and the solid arrows represent the direction of hot flow. The top row of temperature measuring points represents the surface temperature of the heated wall of the stainless steel sheet 1. In the following diagrams, left, middle, and right represent the first, second, and third columns of the three vertical thermocouple holes, respectively. Top, middle, and bottom represent the first, second, and third rows of the three horizontal thermocouple holes, respectively. For example, top left represents the leftmost thermocouple hole in the first row, and similarly, top middle represents the middle thermocouple hole in the first row, and so on.

[0073] like Figure 10 As shown, the experimental data of bare stainless steel sheets were measured. Combining the experimental phenomena and the processed data, the blue area represents single-phase flow, the green area represents boiling near the outlet of the flow channel, the yellow area represents boiling in the central temperature measurement point area, and the orange area represents the beginning of counterflow at the outlet of the flow channel.

[0074] As shown in Figure 11, this is a graph showing the variation of all temperature measurement points with effective heat flux density. The first dashed line in the figure indicates that boiling begins at the outlet of the corresponding effective heat flux channel. The second dashed line in the figure indicates that boiling begins in the central region of the corresponding effective heat flux channel. The third dashed line in the figure indicates that backflow begins to occur in the corresponding heat flux channel. This is data for a chromium-plated surface. By conducting experiments on different surfaces, obtaining different data graphs, and comparing them, we can determine the impact of surface modification on the flow and boiling of the entire channel.

[0075] In single-phase operation, the effective heat flux is calculated based on the temperature and enthalpy difference between the inlet and outlet water. In two-phase operation, the effective heat flux is approximately equal to the heating power multiplied by the proportionality coefficient at the point of boiling.

[0076] Average heat transfer coefficient h w The calculation formula is as follows:

[0077]

[0078]

[0079]

[0080]

[0081] q is the effective heat flux; T is the average temperature of the sheet; T is the average temperature of the water flow in the whole heating section; in T is the water flow inlet temperature; out T is the water flow outlet temperature; p,m Cp is the specific heat capacity of water at constant pressure; m is the mass flow rate; A is the heating section area; T is the average temperature of the water flow in the whole heating section; w,i T is the temperature of the three thermocouples on the stainless steel sheet 1;

[0082] As shown in Figure 12 , the temperature of the left, middle and right positions on the sheet changes with the wall surface effective heat flux. The lowermost horizontal dashed line represents a single-phase state at the corresponding heat flux. In the middle region between the two dashed lines, the heat flux is in the center of the flow passage, and the outlet area is boiling. The uppermost dashed line represents the center of the flow passage also starting to boil at the corresponding heat flux. The upper left represents Figure 9 the first row left thermocouple position, the upper middle represents the first row middle thermocouple position, and the upper right represents the first row right thermocouple position.

[0083] As shown in Figure 13 , the local heat transfer coefficient changes with the local heat flux. The upper left, upper middle, and upper right in the figure have been introduced in the previous paragraph. The local heat transfer coefficient is calculated according to the following formula:

[0084]

[0085] q i is the local heat flux, calculated using the Fourier heat conduction law; T f,i is the temperature of the water flow cross section above the temperature measuring hole of the stainless steel sheet 1. In single-phase state, the inlet and outlet water temperatures are linearly interpolated according to the heating passage length. In boiling state, the saturation temperature at atmospheric pressure is selected; h l,i is the local heat transfer coefficient;

[0086] When periodic flow boiling occurs, bubbles are generated, detached, aggregated, aggregated into large bubbles, and blocked in the flow passage, causing flow impact force to accumulate to a value greater than the bubble pressure, pushing the bubble out of the flow passage, and the flow passage is re-wetted, and then the next cycle of activity is performed.

[0087] As shown in Figure 14The diagram shown illustrates the variation of the average heat transfer coefficient with the average heat flux density, and its calculation method has been introduced above.

[0088] like Figure 15 The figure shows the change of pressure difference signal over time when periodic flow boiling occurs in the flow channel. By comparing the changes of pressure difference signal over time on different surfaces and combining the phenomena, we can analyze the influence of different surfaces on flow boiling heat transfer in the microchannel.

[0089] like Figure 16 The figure shows the spectrum obtained after the pressure difference smoothing signal is processed by FFT signal. The periodic fluctuation frequency can be obtained from the figure, and the boiling fluctuation period of one channel is calculated to be 5.99s.

[0090] like Figure 17 The figure shows the fluctuation of mass flow rate within 60 seconds during periodic flow boiling. The red curve in the figure indicates that large bubbles occupy the flow channel for a long time during this period and do not exit the flow channel, so there is no periodic fluctuation.

[0091] like Figure 18 As shown, the spectrum of the mass flow rate fluctuation is obtained after FFT signal processing. Based on actual phenomena, the time from the maximum position of bubble backflow to the center of the flow channel is approximately 5.45s.

[0092] In summary, this invention facilitates the investigation of the impact of surface modification on flow boiling heat transfer in microchannels. By combining data and observational analysis of the bubble phenomenon of different surfaces in flow boiling within narrow rectangular channels, the influence of different surfaces on bubble generation during flow boiling is summarized. Ultimately, the influence of different surfaces on the single-phase heat transfer coefficient, ONB, and two-phase heat transfer coefficient in narrow rectangular channels can be obtained.

Claims

1. A two-phase flow experimental measurement system of a narrow rectangular channel, characterized in that, The device comprises a deionized water storage tank (86), a deaerating water storage tank (89) connected to the deionized water storage tank (86), a water storage tank heating rod (814) arranged in the deaerating water storage tank (89), a peristaltic pump (810) arranged between the deionized water storage tank (86) and the deaerating water storage tank (89), a filtering branch and a filtering contrast branch connected to the water outlet side of the deaerating water storage tank (89), the filtering branch and the filtering contrast branch further connected to a gear pump (87), a filter (88) and a filter switch valve arranged on the filtering branch, and a non-filtering switch valve arranged on the filtering contrast branch; the gear pump (87) is connected to an adjusting circuit and a mass flow meter (85), the adjusting circuit is connected to the deaerating water storage tank (89), the adjusting circuit is further provided with an adjusting switch valve, and the adjusting switch valve is electrically connected to the gear pump (87); the mass flow meter (85) is connected to a constant-temperature preheating pot (84), the constant-temperature preheating pot (84) is connected to an experimental device (83), and the water outlet end of the experimental device (83) is connected to the deaerating water storage tank (89); a plurality of temperature measuring points are arranged on the experimental device (83), temperature sensors are arranged in the temperature measuring points, and a narrow rectangular channel and a heating surface modified by a stainless steel surface are further arranged in the experimental device (83). The experimental device (83) comprises a stainless steel sheet (1), a stainless steel boss base (2), a G10 glass fiber shell (3), a quartz glass (4) and a stainless steel pressing plate (5); the stainless steel sheet (1) is electroplated with a chromium plating layer with different characteristics; the G10 glass fiber shell (3) is provided with a hollow groove (38) for mounting the stainless steel sheet (1) and two water containing cavities (30), the hollow groove (38) is connected with the water containing cavities (30) through a connecting groove (39), and the two water containing cavities (30) are respectively provided with a water inlet (32) and a water outlet (33); the stainless steel sheet (1) is fixed on the stainless steel boss base (2), and the stainless steel sheet (1) and the stainless steel boss base (2) are arranged in the hollow groove (38); the hollow groove (38), the connecting groove (39) and the quartz glass (4) form a narrow rectangular channel; the quartz glass (4) is fixed on the narrow rectangular channel through the stainless steel pressing plate (5); a plurality of upper temperature measuring point holes (13) are arranged on the side edge of the stainless steel sheet (1), and a plurality of lower temperature measuring point holes (23) are arranged on the stainless steel boss base (2); a temperature measuring corresponding hole (37) in communication with the upper temperature measuring point holes (13) and the lower temperature measuring point holes (23) is arranged on the shell (3), and the temperature sensors are arranged in the upper temperature measuring point holes (13) and the lower temperature measuring point holes (23). The stainless steel boss base (2) comprises a base (21) and a boss (22), a plurality of lower temperature measuring point holes (23) are arranged on the boss (22), and the base (21) and the boss (22) are provided with two communicating stud mounting through holes (24); the bottom of the stainless steel sheet (1) is provided with two sheet studs (11) and two stud nuts (12), and the stainless steel sheet (1) and the stainless steel boss base (2) are connected through the sheet studs (11) and the stud nuts (12).

2. The two-phase flow experimental measurement system of narrow rectangular channel according to claim 1, characterized in that, A high-speed camera (81), a light source (82), a data acquisition end (812) and a direct-current direct-current power heater (811) are further included, the high-speed camera (81) and the light source (82) are installed above the experimental device (83), the direct-current direct-current power heater (811) is installed at the bottom of the experimental device (83), and the data acquisition end (812) is connected with the temperature sensors.

3. The system for experimental measurement of two-phase flow in a narrow rectangular channel according to claim 1, characterized in that, A one-way valve and an on-off valve are arranged between the experimental device (83) and the degassing type water storage tank (89), between the degassing type water storage tank (89) and the filtering branch, and between the constant-temperature preheating pot (84) and the experimental device (83); one-way valves are also arranged between the filtering branch and the gear pump (87), between the mass flow meter (85) and the constant-temperature preheating pot (84) and on the adjusting loop.

4. The system for experimental measurement of two-phase flow in a narrow rectangular channel according to claim 1, characterized in that, The water outlet end of the constant-temperature preheating pot (84) is provided with a preheating pot thermocouple.

5. The system for experimental measurement of two-phase flow in a narrow rectangular channel according to claim 1, characterized in that, Two water storage cavities (30) are arranged on the bottom of the stainless steel plate (1), and each of the two water storage cavities (30) is provided with a thermocouple mounting hole (34) and a pressure gauge mounting hole (35).

6. The system for experimental measurement of two-phase flow in a narrow rectangular channel according to claim 1, characterized in that, The shell (3) and the stainless steel pressing plate (5) are correspondingly provided with a plurality of mounting through holes (31), and the shell (3) and the stainless steel pressing plate (5) are connected through a plurality of bolt members.

7. The system for experimental measurement of two-phase flow in a narrow rectangular channel according to claim 1, characterized in that, The stainless steel sheet (1) is provided with three upper temperature measuring point holes (13) on the side edge, and the stainless steel boss base (2) is provided with six lower temperature measuring point holes (23), which are divided into two rows and three columns and aligned with the three upper temperature measuring point holes (13).

8. A measuring method using the two-phase flow experimental measuring system of any one of claims 1 to 7, characterized in that, The method comprises the following steps: S1: Assemble the experimental device (83), install the measuring system, connect the experimental device (83) to the experimental loop of the measuring system, and adjust the measuring system; specifically including: S11: Turn on the peristaltic pump (810) to pump high-purity deionized water in the deionized water storage tank (86) into the degassing type water storage tank (89), and control the peristaltic pump (810) to run reversely to exhaust the degassing type water storage tank (89) after the high-purity deionized water is added into the degassing type water storage tank (89); S12: Using the water storage tank heating rod (814) in the degassing water storage tank (89), the high-purity deionized water is heated and boiled for 30 minutes to remove non-condensable gases in the high-purity deionized water; then the peristaltic pump (810) is turned off and the water storage tank heating rod (814) is stopped heating, and the high-purity deionized water is naturally cooled; S13: Before the experiment, the on-off of the switch valve in the measurement system is controlled to make the high-purity deionized water circulate in the entire measurement system circuit; the unfiltered switch valve and the adjusting switch valve are closed, and the remaining switch valves in the measurement system circuit are opened, and the measurement system is adjusted; S2: After adjusting the measurement system, it is normally operated, and after the experimental device (83) is not leaking, the experiment of the internal two-phase flow in the narrow rectangular channel is started; S3: set the mass flow threshold Q of the mass flow meter (85) F , the inlet temperature T of the experimental device (83) in , set the mass flow threshold Q of the high-purity deionized water through the mass flow meter (85) F , set the inlet temperature T of the experimental device (83) through the constant temperature preheating pot (84) in ; S4: The straight cylinder type direct current power heater (813) is turned on, the bottom of the experimental device (83) is heated by the straight cylinder type direct current power heater (813), and through heat transfer, the heat is finally conducted to the surface plated heating surface in the experimental device (83), and the high-purity deionized water in the narrow rectangular channel is heated by the heating surface; S5: The heating power of the straight cylinder type direct current power heater (813) is adjusted every 3 minutes, and data is collected once, until the high-purity deionized water in the experimental device (83) is occupied by the backflow of the bubbles generated by boiling; and the high-speed camera (81) is used to shoot and record the flow of the high-purity deionized water in the narrow rectangular channel through the quartz glass (4); A number of temperature and pressure data on the experimental device (83) are collected by the data collection end (812) in cooperation with signal express software; and the mass flow Q is collected by Bronkhorst software F , so as to collect the plating heating surface characteristic data; S6: Replace the different plated heating surfaces on the experimental device (83), repeat steps S2-S5 to conduct the experiment, and obtain the surface characteristic data of different plated heating surfaces.

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