Method for detecting condensation heat transfer coefficient of steam-non-condensable gas mixed jet flow

Abstract

A steam-non-condensable gas mixed jet condensation heat transfer coefficient detection method comprises the following steps: establishing a relationship between a gas plume boundary and temperature distribution through a pure steam jet condensation heat transfer experiment, a visual image reconstruction method and a movable lattice thermocouple arrangement method, and obtaining steam-non-condensable gas mixed jet condensation temperature field distribution through the experiment. According to the relation between the gas plume condensation length and the temperature distribution position, mixed jet condensation length characteristic parameters are obtained, the mixed gas condensation heat transfer area is calculated, and a mixed gas condensation heat transfer coefficient is calculated based on energy conservation; on the basis of a gas plume jet condensation theory analysis model, the content of non-condensable gas and gas plume interference influence under a porous bubbler structure are considered, a porous bubbler mixed gas condensation heat transfer evaluation model is established, and the problem that mixed gas moves towards the upper portion of a bubbler under the action of buoyancy due to the existence of non-condensable gas is solved. Steam and non-condensable gas interfaces in the mixed gas are difficult to distinguish through a visualization method, and the condensation heat transfer area and the heat transfer coefficient cannot be obtained.

Description

Technical Field

[0001] This invention relates to a technology in the field of nuclear reactors, specifically a method for detecting the heat transfer coefficient of a steam-noncondensable gas mixed jet condensation. Background Technology

[0002] Due to its highly efficient condensation heat and mass transfer, gas-immersed jets are widely used in nuclear reactors, such as in containment suppression systems, to introduce high-temperature, high-pressure gases into a subcooled water pool for containment cooling and depressurization during accidents. Steam condensation generates a continuous jet plume, which transfers heat with the subcooled water at the gas-liquid interface. The presence of non-condensable gases within the containment affects the phase transition from steam to liquid, forming a thermally resistive layer at the gas-liquid interface and reducing its heat transfer efficiency. The core challenge in studying the impact of non-condensable gases on the condensation heat transfer characteristics of mixed gases lies in accurately calculating the condensation heat transfer interface of the mixed gases.

[0003] The condensation heat transfer interface area significantly impacts the assessment of the heat transfer coefficient. In a pure steam jet plume, rapid condensation occurs at the bubbler nozzle, and high-speed imaging captures the gas-liquid interface as the actual effective heat transfer interface. However, during the condensation process of a mixed gas, the presence of non-condensable gases causes them to move towards the water surface above the bubbler under buoyancy. The condensed gas plume is difficult to visualize by distinguishing the interface between steam and non-condensable gases in the mixed gas, making it impossible to obtain the condensation heat transfer area and heat transfer coefficient, thus affecting the assessment of heat transfer characteristics. Therefore, it is necessary to propose a method for measuring and evaluating the condensation heat transfer characteristics of a steam-non-condensable gas mixed jet. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies that cannot measure and characterize the condensation heat transfer interface parameters of steam-non-condensable gas mixed jets, and cannot calculate the condensation heat transfer coefficient of mixed gas jets. It proposes a method for detecting the condensation heat transfer coefficient of steam-non-condensable gas mixed jets, solving the problem that the presence of non-condensable gas causes the mixed gas to move upwards under the action of buoyancy, making it difficult to distinguish the interface between steam and non-condensable gas in the mixed gas through visualization methods, and thus making it impossible to obtain the condensation heat transfer area and heat transfer coefficient.

[0005] This invention is achieved through the following technical solution:

[0006] This invention relates to a method for detecting the condensation heat transfer coefficient of a steam-non-condensable gas mixed jet. Through pure steam jet condensation heat transfer experiments, a visualization image reconstruction method, and a movable lattice thermocouple arrangement method, the relationship between the gas plume boundary and temperature distribution is established. The temperature field distribution of the steam-non-condensable gas mixed jet condensation is obtained experimentally. Based on the relationship between the gas plume condensation length and the temperature distribution location, the characteristic parameters of the mixed jet condensation length are obtained, and the condensation heat transfer area of ​​the mixed gas is calculated. The condensation heat transfer coefficient of the mixed gas is calculated based on energy conservation. Based on the theoretical analysis model of gas plume jet condensation, considering the non-condensable gas content and the gas plume interference effect under the porous bubbler structure, an evaluation model for the condensation heat transfer of the mixed gas in a porous bubbler is established.

[0007] The pure steam jet condensation heat transfer experiment and the steam-noncondensable gas jet condensation heat transfer experiment are realized by a steam-noncondensable gas mixed jet condensation heat transfer characteristic experimental device, which includes: a bubbler installed in a pressure-suppressing water tank and connected to the steam supply system and the noncondensable gas supply system respectively. The bubbler is equipped with a sensing and control mechanism connected to a data acquisition system between the steam supply system and the noncondensable gas supply system and the bubbler. A high-speed camera connected to the data acquisition system is installed outside the pressure-suppressing water tank with a visualization window.

[0008] The aforementioned visualization image reconstruction method refers to obtaining the flow morphology of a pure steam jet plume through visualization observation, and then combining it with image reconstruction methods, including video format conversion to image, grayscale processing, binarization processing, inversion filling, median filtering, inversion dilatation filling, and image overlay, to obtain a cloud map of gas-liquid content distribution within a specific time period, and then extracting the plume boundary and interface parameters.

[0009] The aforementioned movable lattice thermocouple arrangement method refers to using lattice temperature measurement to obtain two-dimensional temperature distribution results inside and outside pure steam plumes and steam-non-condensable gas mixed plumes. Considering that the thermocouple wires should not affect the flow field as much as possible and should be resistant to plume impact, a thermocouple wire size of 0.8 mm is used. The thermocouple response time is much shorter than the time of each movement and the dwell time; therefore, the measurement error caused by the thermocouple response time is ignored. Furthermore, under the same operating conditions, the temperature change of the water tank within a 1-minute movement time range is negligible; therefore, the measurement error caused by water temperature changes is also ignored.

[0010] The relationship between the plume boundary and temperature distribution is described in the pure steam jet condensation heat transfer experiment. Firstly, the plume flow morphology and gas-liquid interface parameters are obtained through visualization image reconstruction to determine the steam jet condensation length. Secondly, the temperature field distribution of the plume is acquired based on movable lattice thermocouples. The distance from the location of the temperature difference between the gas and subcooled water at the nozzle outlet to the bubbler nozzle is used as the steam jet condensation length. Comparing the jet condensation length calculated from the temperature distribution and the jet condensation length calculated from the visualization image reconstruction verifies the accuracy of the relationship between the plume boundary and the location of temperature changes.

[0011] The temperature field distribution of the mixed gas jet condensation is obtained by measuring the internal temperature of the mixed gas plume using a movable lattice thermocouple arrangement method, and then obtaining the dimensional characteristics of the condensation length of the mixed gas jet condensation based on the positional relationship between the condensation length at the plume boundary and the temperature distribution change.

[0012] The condensation heat transfer area of ​​the mixed gas jet is obtained by visually reconstructing images to obtain gas-liquid distribution cloud map data from the bubbler outlet to the condensation length boundary. The video file of the gas plume jet is decomposed into a two-dimensional binary image of the gas content distribution. Within the boundary of the jet condensation length characteristic parameter, assuming that each column of pixels perpendicular to the length direction is cylindrical, the lateral area of ​​the cylinder is calculated. The lateral areas of the cylinders in each column are superimposed to obtain the lateral area of ​​the steam jet. Where: n is the number of pixel columns occupied by the jet condensation length, d i Let be the diameter of the jet plume in the i-th column pixel. N i Let l be the number of pixels in the i-th column that meet the requirements; s The actual length of the plume corresponding to the pixel, in meters per pixel; z i Given the actual width of each column of pixels, m / pixel, obtain the characteristic parameter A of the condensation heat transfer interface area of ​​the mixed gas. c .

[0013] The calculation of the condensation heat transfer area of ​​the mixed gas under gas plume interference in a porous bubbler refers to: by judging the interference characteristics of the mixed gas plume, dividing the gas-liquid interface of the interfering mixed gas into independent gas plume regions and interference gas plume regions, and calculating the heat transfer area of ​​each separately and then summing them up. Specifically, this includes:

[0014] ① For independent gas plume regions of the interference mixture, i.e., when the jet condensation length is less than m, calculate the surface area of ​​each gas plume independently and superimpose them to obtain the heat transfer area A of the independent gas plume region. c1 , , where: d i1 Let d be the diameter of the mixed gas jet at the orifice on the i-th cross-section. i2 Let be the diameter of the mixed gas jet at the lower hole of the i-th cross section.

[0015] ② Interference plume region, i.e., when the jet condensation length is greater than m, merges into a single plume. Assuming that each column of pixels inside the plume is elliptical, calculate the lateral area A of the ellipse. c2 , .

[0016] ③ The total heat transfer area of ​​the condensation of the mixed gas is obtained by superimposing the heat transfer areas of the independent gas plume region and the interference gas plume region, thus obtaining the total heat transfer area A. c , .

[0017] Based on the principle of energy balance, a method and theoretical model for evaluating the condensation heat transfer coefficient of the aforementioned mixed gas were established: Where: h is the direct contact condensation heat transfer coefficient of steam, kW / m³ 2 ℃; G0 is the steam mass flow rate, kg / m³ 2 s;h lg A is the latent heat of vaporization of steam, kJ / kg; A0 is the area of ​​the bubbler nozzle, m². 2 ΔT is the subcooling of the pool water at the bubbler, in °C; A c The gas-liquid interface area is m. 2 .

[0018] The aforementioned theoretical analysis model for vapor plume jet condensation assumes that the vapor plume is axisymmetric. At a small distance dx along the horizontal axis, according to the law of conservation of energy... , where: m s G represents the vapor flow rate in the gas phase at any location, in kg / s. c The condensation rate of steam per unit gas plume boundary area, kg / m² 2 s; r is the radius of any cross-sectional area of ​​the vapor plume, in meters. All the heat released during steam condensation is transferred to the cooling water; according to Newton's law of cooling, , where: h lg ρ is the latent heat of vaporization of steam, J / kg; h is the heat transfer coefficient at any point on the liquid side, W / (m²·℃); Ts is the steam temperature, ℃; Tw is the subcooled water temperature, ℃. The mass flux of the steam plume at a certain cross section is... Define the dimensionless condensation driving potential B and the transport modulus S. and Considering the boundary conditions at the nozzle and the tip of the plume, the condensation heat transfer coefficient is obtained. .

[0019] The aforementioned porous bubbler mixed gas condensation heat transfer evaluation model considers the influence of non-condensable gas content X and introduces the ratio Y of the bubbler orifice area to the cross-sectional area of ​​the pipe flow channel. s Influence, And the influence of the bubbler diameter ratio I, I=P / D, the heat transfer coefficient of the mixed gas condensation in the porous bubbler is expressed as The relationship for evaluating the condensation heat transfer coefficient of the mixed gas under a porous bubbler was obtained by fitting experimental data. Attached Figure Description

[0020] Figure 1 This is a flowchart of the present invention;

[0021] Figure 2 This is a schematic diagram of the experimental device for the condensation heat transfer characteristics of the mixed jet according to the present invention;

[0022] In the diagram: 1. Steam supply system; 2. Mass flow meter; 3. Electric regulating valve; 4. Pressure sensor; 5. Temperature sensor; 6. Non-condensable gas supply system; 7. Pressure reducing valve; 8. Data acquisition system; 9. High-speed camera; 10. Backlight; 11. Pressure suppressing tank; 12. Visualization window; 13. Bubble blower.

[0023] Figure 3 This is a schematic diagram of the arrangement of the dot matrix thermocouples in this invention;

[0024] Figure 4 This is a schematic diagram of the method for obtaining air plume boundaries using the visual observation image reconstruction method of the present invention;

[0025] Figure 5 and Figure 6 This invention provides a pure steam jet condensate plume, fractionation cloud map, and temperature distribution.

[0026] Figure 7 A comparison of the jet condensation length results calculated by the temperature distribution method and the image reconstruction method of this invention;

[0027] Figure 8 and Figure 9 This invention provides morphology and gas fraction cloud diagrams of single gas plumes and jet interference gas plumes of vapor-noncondensable gas mixtures.

[0028] Figure 10 This is a schematic diagram illustrating the calculation of the heat transfer area of ​​a single gas plume and a jet interference gas plume according to the present invention;

[0029] Figure 11 This is a comparison between the calculated and experimental values ​​of the condensation heat transfer coefficient evaluation model of this invention. Detailed Implementation

[0030] like Figure 1 As shown in the figure, this embodiment relates to a method for detecting the condensation heat transfer coefficient of a steam-noncondensable gas mixed jet. By establishing a visualization experimental device for the condensation heat transfer characteristics of a steam-noncondensable gas mixed jet, and based on the condensation of pure steam jet, the relationship between the gas plume boundary parameters and the lattice temperature field distribution is established. According to the temperature field distribution of the condensation of the steam-noncondensable gas mixed jet, the characteristic parameters of the condensation heat transfer length and area of ​​the mixed gas jet are obtained, and the condensation heat transfer coefficient of the mixed gas jet is calculated.

[0031] like Figure 2 As shown, a bubbler 13 is installed in the pressure-suppressing water tank 11 and is connected to the steam supply system 1 and the non-condensable gas supply system 6, respectively. A sensor control mechanism connected to the data acquisition system 8 is provided between the steam supply system 1, the non-condensable gas supply system 6, and the bubbler 13. A high-speed camera 9 connected to the data acquisition system 8 is installed outside the pressure-suppressing water tank 11, which has a visualization window 12.

[0032] The sensing and control mechanism includes: a mass flow meter 2, an electric regulating valve 3, a pressure sensor 4, and a temperature sensor 5 disposed between the steam supply system 1 and the bubbler 13; and a pressure reducing valve 7, a pressure sensor 4, and a temperature sensor 5 disposed between the non-condensable gas supply system 6 and the bubbler 13.

[0033] The pressure-suppressing water tank 11 is preferably equipped with a backlight 10 that matches the high-speed camera 9.

[0034] The steam supply system 1 provides steam at a rated flow rate for the experiment, and uses an electrically heated steam boiler with a rated power of 100kW, a rated evaporation capacity of 143kg / h, and a rated steam pressure of 0.8MPa.

[0035] The non-condensable gas supply system 6 is a nitrogen cylinder group.

[0036] The visualization window of the pressure-suppressing water tank 11 has a size of DN600. The cylindrical experimental water tank has a diameter of 1m and a height of 1.5m. DN600 visualization windows are opened on both sides of the water tank container, using tempered glass that is resistant to high temperature and high pressure, so as to clearly capture the gas condensation plume.

[0037] like Figure 3 The diagram illustrates the arrangement of the movable lattice thermocouples, including lattice thermocouple wires and a two-dimensional movable guide rail, used for the internal and external temperature distribution of pure steam and mixed gas plumes. Considering that the thermocouple wires should minimally affect the flow field and resist plume impact, a wire size of 0.8 mm is used. The thermocouple response time is much shorter than the time of each movement and the dwell time; therefore, measurement errors caused by the thermocouple response time are ignored. Furthermore, under the same operating conditions, the temperature change in the water tank within a 1-minute movement time range is negligible; therefore, measurement errors caused by water temperature changes are also ignored.

[0038] like Figure 4As shown, the plume boundary is obtained by visual image reconstruction using a method that reconstructs images from pure steam jet condensation. This process includes video format conversion to image, grayscale and binarization processing, inversion fill, median filtering, inversion dilatation fill, and image overlay to obtain a gas-liquid distribution cloud map. In this map, the red area represents the bubbler pipe and steam jet plume, with a maximum pixel value of 255; the blue area represents the subcooled water region, with a minimum pixel value of 0. The location of the rated pixel value is taken as the effective position of the gas-liquid interface, and the distance from this point to the bubbler is taken as the steam jet condensation length L. Figure 5 As shown, the steam mass flux is 707 kg / m³. 2 s, water temperature is 70℃.

[0039] like Figure 6 As shown, the axial temperature distribution at the center of the nozzle is obtained through the movable dot matrix thermocouple arrangement, with a steam mass flux of 707 kg / m³. 2 At the bubbler outlet, the temperature gradient is significant. Along the jet direction, steam condensation causes a rapid temperature drop. As distance increases, the temperature along the jet direction gradually converges with the surrounding cooling water temperature. When the temperature difference between the gas at the nozzle outlet and the subcooled water temperature (T...)... g -T w The temperature drops by 90%, and the distance from this temperature point to the bubbler nozzle is taken as the condensation length of the steam jet.

[0040] like Figure 7 As shown, a comparative analysis was conducted on the jet condensation length calculated using the temperature difference method and the image reconstruction method under different operating conditions of pure steam jet condensation. 89.34% of the data had a relative error within ±20%, and the average relative error (MRE) was 10.21%, verifying the accuracy of the temperature distribution measurement method for evaluating jet condensation length.

[0041] like Figure 8 As shown, the gas condensation flow pattern and gas content distribution under the condensation of a vapor-noncondensable gas mixture were obtained using visualization and image reconstruction methods, with a gas mass flux of 531 kg / m³. 2 The water temperature is 30℃, and the proportion of non-condensable gases is 10%. The accumulation of non-condensable gases in the gas plume hinders heat exchange between steam and subcooled water, thus worsening the steam condensation and heat transfer effect.

[0042] The dot-matrix thermocouple measurement system obtains the axial temperature distribution at the center of the nozzle under condensation of the mixed gas, and the temperature difference between the mixed gas and the subcooled water at the nozzle outlet (T). g -T w The overall temperature drops by 90%, and the distance from this temperature point to the nozzle is determined to be the condensation length L of the mixed gas jet.

[0043] like Figure 9The figure shows a cloud map of the gas-liquid distribution at the gas-liquid interface area of ​​the mixed gas, where the steam mass flux is 354 kg / m³. 2 The water temperature is 30℃, the non-condensable gas content is 10%, and the pitch ratio P / D is 5. The gas plume may be an independent plume or an interference-induced coalescence phenomenon. Within a distance m from the bubbler nozzle, the gas plume consists of two independent jets that subsequently interfere and coalesce, making it difficult to calculate the area of ​​the mixed gas plume.

[0044] like Figure 10 As shown in (a), the gas-liquid interface distribution cloud map obtained by the image reconstruction method is processed into a two-dimensional binary image. The pixel value of the gas plume location is represented by a red square. Assuming that each column of pixels is a cylinder, the lateral area of ​​the cylinder is calculated. The lateral areas of each column of cylinders inside the gas plume are superimposed to obtain the gas-liquid heat transfer area Ac of the steam jet. Where: n is the number of pixel columns occupied by the jet condensation length, d i Let be the diameter of the jet plume in the i-th column pixel. N i Let l be the number of pixels in the i-th column that meet the requirements; s The actual length of the plume corresponding to the pixel, in meters per pixel; z i The actual width of each column of pixels, in m / pixel.

[0045] The gas-liquid interface of the interfering gas mixture is divided into two parts: independent gas plume regions, i.e., when the jet condensation length is less than m. The surface area of ​​each gas plume is calculated independently and then superimposed to obtain the heat transfer area A of the independent gas plume region. c1 , , where: d i1 Let d be the diameter of the mixed gas jet at the orifice on the i-th cross-section. i2 The diameter of the mixed gas jet at the lower orifice of the i-th cross section; the interference plume region, i.e., when the jet condensation length is greater than m, is merged into a single plume. Still assuming that each column of pixels inside the plume is an ellipse, calculate the lateral area A of the ellipse. c2 , .like Figure 10 (b) shows a schematic diagram of the pixel matrix of the superimposed independent gas plume region and the interference gas plume region, obtaining the total heat transfer area A of the mixed gas condensation. c , .

[0046] Based on the principle of energy balance, a method and theoretical model for evaluating the heat transfer coefficient of mixed gas condensation are established: Where: h is the direct contact condensation heat transfer coefficient of steam, kW / m³ 2 ℃; G0 is the steam mass flow rate, kg / m³ 2 s;h lg A is the latent heat of vaporization of steam, kJ / kg; A0 is the area of ​​the bubbler nozzle, m².2 ΔT is the subcooling of the pool water at the bubbler, in °C; A c The gas-liquid interface area is m. 2 .

[0047] Based on the theoretical analysis model of vapor plume jet condensation, the vapor plume condensing into a vapor plume is an axisymmetric figure with the horizontal axis being the x-axis and the vertical axis being the r-axis. Over a small distance dx, according to the law of conservation of energy... , where: m s G represents the vapor flow rate in the gas phase at any location, in kg / s. c The condensation rate of steam per unit gas plume boundary area, kg / m² 2 s; r is the radius of any cross-sectional area of ​​the vapor plume, in meters. All the heat released during steam condensation is transferred to the cooling water; according to Newton's law of cooling, , where: h lg T represents the latent heat of vaporization of steam, J / kg; h is the heat transfer coefficient at any location on the liquid side, W / (m²·℃); s T represents the steam temperature, in °C. w The temperature of the subcooled water is ℃. The mass flux of the steam plume at a certain cross-section is... Define the dimensionless condensation driving potential B and the transport modulus S. and Considering the boundary conditions at the nozzle and the tip of the plume, the condensation heat transfer coefficient is obtained. .

[0048] When steam containing non-condensable gases condenses, the influence of the non-condensable gas content is introduced, and the formula for calculating the average condensation heat transfer coefficient of the mixed gas is as follows: When considering the influence of the bubbler structure, the ratio of the bubbler orifice area to the cross-sectional area of ​​the bubbler flow channel is introduced. Furthermore, the influence of the nodal diameter ratio is introduced, and I = P / D. Therefore, the heat transfer coefficient of the mixed gas condensation in the porous bubbler is expressed as... .

[0049] Through specific practical experiments, the relationship for evaluating the condensation heat transfer coefficient of the mixed gas under a porous bubbler was obtained by fitting experimental data. The heat transfer coefficient model of this mixed gas was compared and analyzed with the experimental results of pure steam condensation heat transfer and mixed gas condensation heat transfer, and the experimental data of Li et al. were verified. Figure 11 As shown, the relative error between the experimental results and the model results is within ±30% for 89.34% of the data, and the average relative error (MRE) is 11.24%, indicating that the model can accurately predict the heat transfer coefficient of jet condensation.

[0050] Compared with existing technologies, this method obtains the morphology and gas-liquid interface characteristic parameters of the pure steam jet condensation plume through visualization, compares the internal and external temperature field distribution of the pure steam condensation plume with the arrangement of moving lattice thermocouples, and establishes the relationship between the plume boundary and the temperature drop position. Based on the condensation temperature field boundary of the mixed jet containing non-condensable gases, it obtains the condensation heat transfer characteristic parameters, and by judging the interface flow pattern and plume interference characteristics, it obtains the gas-liquid interface heat transfer area and condensation heat transfer coefficient. Based on the theoretical analysis model of plume jet condensation, considering the non-condensable gas content and the influence of plume interference under the porous bubbler structure, it establishes an evaluation model for the condensation heat transfer coefficient of the mixed gas in the porous bubbler. This invention can support the study of the condensation heat transfer characteristics of steam-non-condensable gas mixed jets.

[0051] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A method for detecting the heat transfer coefficient of a steam-noncondensable gas mixed jet condensation, characterized in that, By employing pure steam jet condensation heat transfer experiments, visualization image reconstruction methods, and movable lattice thermocouple arrangement methods, the relationship between the gas plume boundary and temperature distribution was established. The temperature field distribution of the steam-non-condensable gas mixed jet condensation was obtained experimentally. Based on the relationship between the gas plume condensation length and the temperature distribution location, the characteristic parameters of the mixed jet condensation length were obtained, and the heat transfer area of ​​the mixed gas condensation was calculated. The heat transfer coefficient of the mixed gas condensation was calculated based on energy conservation. Based on the theoretical analysis model of gas plume jet condensation, considering the non-condensable gas content and the gas plume interference effect under the porous bubbler structure, an evaluation model of mixed gas condensation heat transfer in a porous bubbler was established.

2. The method for detecting the heat transfer coefficient of a steam-noncondensable gas mixed jet condensation according to claim 1, characterized in that, The pure steam jet condensation heat transfer experiment and the steam-noncondensable gas jet condensation heat transfer experiment are realized by a steam-noncondensable gas mixed jet condensation heat transfer characteristic experimental device, which includes: a bubbler installed in a pressure-suppressing water tank and connected to the steam supply system and the noncondensable gas supply system respectively. The bubbler is equipped with a sensing and control mechanism connected to a data acquisition system between the steam supply system and the noncondensable gas supply system and the bubbler. A high-speed camera connected to the data acquisition system is installed outside the pressure-suppressing water tank with a visualization window.

3. The method for detecting the condensation heat transfer coefficient of a steam-noncondensable gas mixed jet according to claim 1, characterized in that, The aforementioned visualization image reconstruction method refers to obtaining the flow morphology of a pure steam jet plume through visualization observation, and then combining it with image reconstruction methods, including video format conversion to image, grayscale processing, binarization processing, inversion filling, median filtering, inversion dilatation filling, and image overlay, to obtain a cloud map of gas-liquid content distribution within a specific time period, and then extracting the plume boundary and interface parameters.

4. The method for detecting the heat transfer coefficient of a steam-noncondensable gas mixed jet condensation according to claim 1, characterized in that, The aforementioned movable dot matrix thermocouple arrangement method refers to: using dot matrix temperature measurement to achieve two-dimensional temperature distribution results inside and outside the pure steam plume and the steam-non-condensable gas mixed plume; considering that the thermocouple wire should not affect the flow field as much as possible and resist the impact of the plume, the thermocouple wire size is 0.8mm, the thermocouple response time is much smaller than the time of each movement and the dwell time, the measurement error caused by the thermocouple response time is ignored, and the temperature change of the water pool within 1 minute under the same working condition is negligible, the measurement error caused by the water temperature change is ignored.

5. The method for detecting the condensation heat transfer coefficient of a steam-noncondensable gas mixed jet according to claim 1, characterized in that, The relationship between the gas plume boundary and temperature distribution is described in the pure steam jet condensation heat transfer experiment. On the one hand, the gas plume flow morphology and gas-liquid interface parameters are obtained through visualization image reconstruction to obtain the steam jet condensation length. On the other hand, after the gas plume temperature field distribution is collected based on movable dot matrix thermocouples, the distance from the position of the temperature difference between the gas and subcooled water at the nozzle outlet to the bubbler nozzle is taken as the steam jet condensation length. The accuracy of the relationship between the gas plume boundary and the position of temperature change is verified by comparing the jet condensation length of the temperature distribution with the jet condensation length calculated by visualization image reconstruction.

6. The method for detecting the condensation heat transfer coefficient of a steam-noncondensable gas mixed jet according to claim 1, characterized in that, The temperature field distribution of the mixed gas jet condensation is obtained by measuring the internal temperature of the mixed gas plume using a movable lattice thermocouple arrangement method, and then obtaining the dimensional characteristics of the condensation length of the mixed gas jet condensation based on the positional relationship between the condensation length at the plume boundary and the temperature distribution change.

7. The method for detecting the heat transfer coefficient of a steam-noncondensable gas mixed jet condensation according to claim 1, characterized in that, The condensation heat transfer area of ​​the mixed gas jet is obtained by visually reconstructing images to obtain gas-liquid distribution cloud map data from the bubbler outlet to the condensation length boundary. The video file of the gas plume jet is decomposed into a two-dimensional binary image of the gas content distribution. Within the boundary of the jet condensation length characteristic parameter, assuming that each column of pixels perpendicular to the length direction is cylindrical, the lateral area of ​​the cylinder is calculated. The lateral areas of the cylinders in each column are superimposed to obtain the lateral area of ​​the steam jet. Where: n is the number of pixel columns occupied by the jet condensation length, d i Let be the diameter of the jet plume in the i-th column pixel. N i Let l be the number of pixels in the i-th column that meet the requirements; s The actual length of the plume corresponding to the pixel, in meters per pixel; z i Given the actual width of each column of pixels, m / pixel, obtain the characteristic parameter A of the condensation heat transfer interface area of ​​the mixed gas. c .

8. The method for detecting the condensation heat transfer coefficient of a steam-noncondensable gas mixed jet according to claim 1, characterized in that, The calculation of the condensation heat transfer area of ​​the mixed gas under gas plume interference in a porous bubbler refers to: by judging the interference characteristics of the mixed gas plume, dividing the gas-liquid interface of the interfering mixed gas into independent gas plume regions and interference gas plume regions, and calculating the heat transfer area of ​​each separately and then summing them up. Specifically, this includes: ① For independent gas plume regions of the interference mixture, i.e., when the jet condensation length is less than m, calculate the surface area of ​​each gas plume independently and superimpose them to obtain the heat transfer area A of the independent gas plume region. c1 , , where: d i1 Let d be the diameter of the mixed gas jet at the orifice on the i-th cross-section. i2 The diameter of the mixed gas jet at the lower hole of the i-th cross section; ② Interference plume region, i.e., when the jet condensation length is greater than m, merges into a single plume. Assuming that each column of pixels inside the plume is elliptical, calculate the lateral area A of the ellipse. c2 , ; ③ The total heat transfer area of ​​the condensation of the mixed gas is obtained by superimposing the heat transfer areas of the independent gas plume region and the interference gas plume region, thus obtaining the total heat transfer area A. c , .

9. The method for detecting the condensation heat transfer coefficient of a steam-noncondensable gas mixed jet according to claim 1, characterized in that, Based on the principle of energy balance, a method and theoretical model for evaluating the condensation heat transfer coefficient of the aforementioned mixed gas were established: Where: h is the direct contact condensation heat transfer coefficient of steam, kW / m³ 2 ℃; G0 is the steam mass flow rate, kg / m³ 2 s;h lg A is the latent heat of vaporization of steam, kJ / kg; A0 is the area of ​​the bubbler nozzle, m². 2 ΔT is the subcooling of the pool water at the bubbler, in °C; A c The gas-liquid interface area is m. 2 .

10. The method for detecting the heat transfer coefficient of a steam-noncondensable gas mixed jet condensation according to claim 1, characterized in that, The aforementioned theoretical analysis model for vapor plume jet condensation assumes that the vapor plume is axisymmetric. At a small distance dx along the horizontal axis, according to the law of conservation of energy... , where: m s G represents the vapor flow rate in the gas phase at any location, in kg / s. c The condensation rate of steam per unit gas plume boundary area, kg / m² 2 s; r is the radius of any cross-sectional area of ​​the plume, m. All the heat released by the condensation of steam is transferred to the cooling water. According to Newton's law of cooling, , where: h lg The latent heat of vaporization of steam is J / kg; h is the heat transfer coefficient at any point on the liquid side, W / (m²·℃); Ts is the steam temperature, ℃; Tw is the subcooled water temperature, ℃; and the mass flux of the steam plume at a certain cross section is... Define the dimensionless condensation driving potential B and the transport modulus S. and Considering the boundary conditions at the nozzle and the tip of the plume, the condensation heat transfer coefficient is obtained. ; The aforementioned porous bubbler mixed gas condensation heat transfer evaluation model considers the influence of non-condensable gas content X and introduces the ratio Y of the bubbler orifice area to the cross-sectional area of ​​the pipe flow channel. s Influence, And the influence of the bubbler diameter ratio I, I=P / D, the heat transfer coefficient of the mixed gas condensation in the porous bubbler is expressed as The evaluation formula for the condensation heat transfer coefficient of mixed gas under porous bubbler was obtained by fitting experimental data.

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