Method for dynamic control of local exposure and re-submergence water level in high-temperature flow channel

Abstract

The application relates to a high-temperature flow channel local exposure and re-submersion water level dynamic control method. The method comprises the following steps: setting an initial reserved water level, pressure difference induced pressure pipe zero calibration, heating plate power-on heating for pre-experiment; measuring the pressure difference water level based on the pressure difference transmitter, solving the real-time water level based on the quasi-steady energy conservation equation; determining the proportional coefficient based on the empirical relationship obtained through pre-experiment regression; calculating the real water level based on the pressure difference water level, the real-time water level and the proportional coefficient, and triggering water injection submersion if the real water level reaches the target water level. Through pressure difference dynamic zero calibration and thermodynamic model replacement of direct measurement, a boiling interface liquid level control method is constructed, through establishment of a certain mapping relationship among heat input, evaporation consumption and water level drop, traditional uncontrollable two-phase flow fluctuation is converted into a usable physical regulation and control tool, accurate measurement of the water level is realized, and accurate initial conditions are provided for reproduction of the local exposure axial large temperature difference state.

Description

Technical Field

[0001] This application relates to the fields of nuclear engineering and nuclear safety technology, and in particular to a method for dynamic control of water level in local exposed re-submerged areas within high-temperature flow channels. Background Technology

[0002] In small-break loss-of-coolant accidents, the coolant is not completely discharged through the breach, resulting in residual coolant within the reactor core. This creates a localized exposed state and generates a significant axial temperature gradient. To elucidate the reflooding cooling phenomenon under this localized exposed state, it is necessary to experimentally reproduce a physically meaningful scenario—controlling flooding at a specific water level. The key experimental challenge lies in the precise control of the initial residual water level under high-temperature conditions. The high superheat state causes the residual coolant to boil, forming a dynamic two-phase mixture rather than a stable liquid phase. This boiling phenomenon greatly complicates the task of accurately capturing and maintaining a specific water level at the moment of reflooding triggering. Given the water level uncertainty caused by boiling, reproducing the specific initial water level state of localized exposure with a large axial temperature difference in reflooding experiments presents a significant technical obstacle.

[0003] Since the water level control process in reflooding experiments is a dynamic, fluctuating evaporation-decline process, real-time control of the evaporation of the two-phase mixture and accurate water level feedback are crucial. Inaccurate control or untimely feedback leading to excessive water level drops will cause irreversible experimental errors. Under high temperature and pressure conditions, the residual coolant continuously boils, forming a dynamic vapor-liquid two-phase mixture, resulting in significant water level fluctuations. Existing water level control methods (such as differential pressure transmitters or capacitive sensors) are limited by changes in the dielectric constant of the two-phase flow and interface disturbances, making it difficult to stably maintain the target initial water level under boiling conditions. Furthermore, they lack a real-time control mechanism for transient evaporation-condensation equilibrium, and the water level uncertainty caused by boiling further amplifies parameter sensitivity issues. These problems limit the verification accuracy of the core reflooding process prediction model.

[0004] Therefore, there is an urgent need in related technologies for a method that can provide real-time feedback to confirm the water level position when the water level has not reached the preset water level, and immediately trigger a re-flooding experiment when the water level reaches the preset water level. Summary of the Invention

[0005] Therefore, it is necessary to provide a method for dynamic control of water level in high-temperature flow channels that enables local exposure and re-submersion, addressing the aforementioned technical problems.

[0006] Firstly, this application provides a method for dynamically controlling the water level of locally exposed and re-submerged sections within a high-temperature flow channel. The method includes: Set the initial reserved water level, zero-calibrate the differential pressure tap, and power on the heating plate to raise the temperature for a preliminary experiment; The differential pressure water level is measured using a differential pressure transmitter, and the real-time water level is solved based on the quasi-steady-state energy conservation equation. The proportionality coefficient is determined based on the empirical relationship obtained from the pre-experiment regression. The actual water level is calculated based on the pressure difference water level, real-time water level, and proportional coefficient. If the actual water level reaches the target water level, flooding is triggered.

[0007] Optionally, in one embodiment of this application, the differential pressure tap is located at the inlet and outlet of the pre-experiment flow channel.

[0008] Optionally, in one embodiment of this application, an optical fiber temperature sensor is installed on the effective heating section of the heating plate to measure the axial temperature distribution.

[0009] Optionally, in one embodiment of this application, the step of solving the real-time water level based on the quasi-steady-state energy conservation equation includes: The degree of water level drop is calculated based on the sensible heat of the heating plate, the sensible heat of the reserved water level, the latent heat of boiling evaporation, and the total input heat, according to the energy conservation equation. The real-time water level is calculated based on the degree of water level drop and the initial reserved water level.

[0010] Optionally, in one embodiment of this application, determining the proportional coefficient based on the empirical relationship obtained from pre-experimental regression includes: The quenching temperature point was determined based on the axial temperature distribution data from the preliminary experiment. The proportional coefficient is determined by regression fitting of the actual water level and differential pressure water level corresponding to the quenching temperature point with the real-time water level.

[0011] The aforementioned method for dynamic control of water level in locally exposed and re-submerged high-temperature flow channels involves several steps. First, an initial reserved water level is set, the differential pressure tap is zeroed and calibrated, and a heating plate is energized for pre-experimentation. Then, the differential pressure level is measured using a differential pressure transmitter, and the real-time water level is solved based on the quasi-steady-state energy conservation equation. Next, an empirical relationship is obtained based on regression from the pre-experiment to determine the proportionality coefficient. Finally, the actual water level is calculated based on the differential pressure level, real-time water level, and proportionality coefficient. If the actual water level reaches the target water level, flooding is triggered. In other words, by using dynamic zero-calibration of the differential pressure and a thermodynamic model to replace direct measurement, a boiling interface water level control method is constructed. By establishing a deterministic mapping relationship between heat input, evaporation consumption, and water level drop, the traditionally uncontrollable two-phase flow fluctuations are transformed into a usable physical control tool, achieving accurate water level measurement and providing precise initial conditions for reproducing locally exposed axial large temperature difference states. At the same time, it can be applied to partial exposure experiments in other rod bundle elements and plate elements, and can even provide a new method for predicting the actual liquid level in small breakage accidents in engineering technology. Attached Figure Description

[0012] Figure 1 This is a flowchart illustrating a method for dynamically controlling the water level of partially exposed and re-submerged areas within a high-temperature flow channel, as described in one embodiment. Figure 2 This is a schematic diagram of the experimental ontology in one embodiment; Figure 3 This is a schematic diagram illustrating the change of water level height over time in one embodiment. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0014] In one embodiment, such as Figure 1 As shown, a method for dynamic control of local exposed and re-submerged water levels in a high-temperature flow channel is provided, including the following steps: S101: Set the initial reserved water level, zero-calibrate the differential pressure tap, and power on the heating plate to raise the temperature for a preliminary experiment.

[0015] In this embodiment, firstly, a relatively high initial reserved water level is set. In order to eliminate the influence of the loop pressure head on the measurement results, when the water level at the inlet end is level with the initial position of the effective heating section, the water level of the differential pressure tapping pipe is zeroed and calibrated. After that, the heating plate is powered on to heat up and the pre-experiment begins.

[0016] In one embodiment of this application, the differential pressure tap is located at the inlet and outlet of the pre-experiment flow channel.

[0017] In one embodiment of this application, such as Figure 2 As shown, to achieve real-time monitoring of water level data, differential pressure taps are connected to the inlet and outlet positions of the pre-experiment flow channel, i.e., the main body, and observations are made through differential pressure signals. To ensure that the connected differential pressure transmitter accurately measures the water level, the bottom of the experimental section is connected to the loop.

[0018] In one embodiment of this application, an optical fiber temperature sensor is installed on the effective heating section of the heating plate to measure the axial temperature distribution.

[0019] In one embodiment of this application, an optical fiber temperature sensor is installed in the effective heating section of the heating plate to accurately measure the axial temperature distribution. The optical fiber temperature sensor has temperature measuring points with millimeter-level spacing distributed along the axial direction.

[0020] S102: Measure differential pressure water level based on differential pressure transmitter, and solve the real-time water level based on the quasi-steady-state energy conservation equation.

[0021] In this embodiment, as the heating plate heats up upon power-on, the cooling water evaporates and the liquid level drops, causing a change in the real-time differential pressure displayed by the differential pressure transmitter. When the water at the bottom reaches its saturation temperature and begins to boil, continuous boiling forms a dynamic vapor-liquid two-phase mixture, disturbing the water level. In this situation, the measurement accuracy of the differential pressure transmitter decreases due to the instability of the liquid phase.

[0022] When the cooling water temperature is below the saturation temperature, the actual water level equals the pressure difference water level, expressed as: When cooling water continues to boil and forms a vapor-liquid two-phase mixture, its average density... Less than This creates a pressure difference, which is calculated using the following formula:

[0023] However, the differential pressure transmitter's calculations are completely unaware of density changes and still use... The calculation is performed using the following formula:

[0024]

[0025] Therefore, when a differential pressure transmitter measures a vapor-liquid two-phase mixture, the pressure difference it displays corresponds to the water level height. Less than the actual water level Therefore, using only a differential pressure transmitter to measure water level is inaccurate and contains a certain degree of error.

[0026] Simultaneously, the real-time water level is calculated based on the quasi-steady-state energy conservation equation. Specifically, a fiber optic temperature sensor acquires temperature data in real time at a frequency of 10Hz, capturing the temperature of the bottom cooling water and the axial distribution of the wall temperature. When the heating plate is energized and begins to heat up, a portion of the heat is used to raise the subcooled water to its saturation temperature (sensible heat for water level), another portion is used to heat the heating plate to reach the required operating temperature, and the last portion is used for the latent heat of vaporization of the saturated water. The real-time water level is calculated using the temperature and known conditions such as the heating plate mass, the total length of the heating section, and the initial reserved water level.

[0027] Specifically, in one embodiment of this application, the step of solving the real-time water level based on the quasi-steady-state energy conservation equation includes: S201: The degree of water level drop is calculated based on the sensible heat of the heating plate, the sensible heat of the reserved water level, the latent heat of boiling evaporation, and the total input heat, according to the energy conservation equation.

[0028] S202: Calculate the real-time water level based on the degree of water level drop and the initial reserved water level.

[0029] In one embodiment of this application, the average temperature difference between two temperature measurements of the exposed portion is assumed to be... The temperature difference between the two temperature measurements of the cooling water is And other known conditions: represent Mass of the heating plate at the axial height position. represent Mass of the heating plate at the axial height position. Represents the total length of the heating section. To reserve water level height, To trigger the flood level, This represents the latent heat of the cooling water at the corresponding pressure. It is assumed that the temperature distribution in the exposed area above the liquid level is linear and that heat loss during the single-phase convective heat transfer process in the boiling process is negligible, to simplify the calculation. At this point, each small time interval from the start of heating to the triggering of re-submersion is considered. The total input heat is:

[0030] Where P is the input electrical power.

[0031] The input heat will be distributed to the sensible heat of the heating plate Qout1, the sensible heat of the reserved water level Qout2, and the latent heat of boiling evaporation Qout3, specifically as follows:

[0032]

[0033]

[0034] The approximate transient water level drop was calculated in real time based on the energy conservation equation. The real-time water level h obtained through the energy conservation equation method is:

[0035] In actual experiments, there is some heat loss, so not all the heat from the power source is distributed within this heat allocation system. This results in the water level calculated using the quasi-steady-state energy conservation method being higher than the actual water level. Similarly, calculating the water level solely using the energy conservation equation introduces a certain degree of error.

[0036] S103: Determine the proportional coefficient based on the empirical relationship obtained from the pre-experiment regression.

[0037] In this embodiment, after the preliminary experiment, the quenching temperature point at each moment, i.e., the true liquid level height at that moment, can be obtained by processing the experimental temperature data. This liquid level height is a value between the differential pressure water level and the real-time water level. To obtain water level information with higher accuracy than the differential pressure water level and the real-time water level, a proportionality coefficient k is introduced. It is the ratio between the quenching temperature point (true water level height) and the differential pressure water level and the real-time water level, and is composed of dimensionless numbers that affect the boiling and evaporation of saturated water.

[0038] The basic form of the proportionality coefficient k relationship is:

[0039] Among them, dimensionless number and and triggering flood level These are all parameters that can affect the proportionality coefficient k.

[0040] Specifically, in one embodiment of this application, determining the proportional coefficient based on the empirical relationship obtained from pre-experimental regression includes: S301: Determine the quenching temperature point based on the axial temperature distribution data from the preliminary experiment.

[0041] S302: Determine the proportional coefficient by performing data regression fitting based on the actual water level and differential pressure water level corresponding to the quenching temperature point and the real-time water level.

[0042] In one embodiment of this application, the quenching temperature point is determined based on the axial temperature distribution data from a preliminary experiment. Then, a proportionality coefficient is determined by performing data regression fitting between the actual water level and differential pressure level corresponding to the quenching temperature point and the real-time water level. The proportionality coefficient relationship obtained after regression is as follows:

[0043] This formula meets the accuracy requirements for water level measurement and control in this partial exposure and re-submersion experiment.

[0044] S104: The actual water level is calculated based on the pressure difference water level, real-time water level and proportional coefficient. If the actual water level reaches the target water level, water injection and flooding are triggered.

[0045] In the embodiments of this application, the proportionality coefficient obtained from preliminary experiments is used. and the differential pressure transmitter obtained in the experiment And the water level height calculated in real time by the energy conservation equation. It can provide real-time feedback on the actual water level. The conversion formula is as follows, which yields the actual water level information. :

[0046] The differential pressure level and real-time water level obtained through these two methods are corrected using a proportionality coefficient k to obtain more accurate water level information. If the actual water level has not yet reached the set target level, heating and evaporation will continue; if the set target level is reached, flooding will be triggered. Figure 3 As shown in the figure, the final result is that flooding is triggered when all thermal parameters, such as water level measurement and inlet flow rate, are simultaneously met. The water level control accuracy is shown in the figure.

[0047] In the aforementioned dynamic control method for the water level of locally exposed re-submerged areas within a high-temperature flow channel, the following steps are taken: First, an initial reserved water level is set, the differential pressure tap is zeroed and calibrated, and a heating plate is energized to raise the temperature for a preliminary experiment. Then, the differential pressure level is measured using a differential pressure transmitter, and the real-time water level is solved based on the quasi-steady-state energy conservation equation. Next, an empirical relationship is obtained based on regression from the preliminary experiment to determine the proportionality coefficient. Finally, the actual water level is calculated based on the differential pressure level, the real-time water level, and the proportionality coefficient. If the actual water level reaches the target water level, flooding is triggered. In other words, by using dynamic zero-calibration of the differential pressure and a thermodynamic model to replace direct measurement, a boiling interface water level control method is constructed. By establishing a deterministic mapping relationship between heat input, evaporation consumption, and water level drop, the traditionally uncontrollable two-phase flow fluctuations are transformed into a usable physical control tool, achieving accurate water level measurement and providing precise initial conditions for reproducing the locally exposed axial large temperature difference state. At the same time, it can be applied to partial exposure experiments in other rod bundle elements and plate elements, and can even provide a new method for predicting the actual liquid level in small breakage accidents in engineering technology.

[0048] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0049] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments described above. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, etc., and are not limited to these.

[0050] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0051] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for dynamic control of water level in locally exposed and re-submerged areas within a high-temperature flow channel, characterized in that, The method includes: Set the initial reserved water level, zero-calibrate the differential pressure tap, and power on the heating plate to raise the temperature for a preliminary experiment; The differential pressure water level is measured using a differential pressure transmitter, and the real-time water level is solved based on the quasi-steady-state energy conservation equation. The proportionality coefficient is determined based on the empirical relationship obtained from the pre-experiment regression. The actual water level is calculated based on the pressure difference water level, real-time water level and proportional coefficient. If the actual water level reaches the target water level, water injection and flooding are triggered. The method for solving the real-time water level based on the quasi-steady-state energy conservation equation includes: The degree of water level drop is calculated based on the sensible heat of the heating plate, the sensible heat of the reserved water level, the latent heat of boiling evaporation, and the total input heat, according to the energy conservation equation. The real-time water level is calculated based on the degree of water level drop and the initial reserved water level. The determination of the proportionality coefficient based on the empirical relationship obtained from pre-experimental regression includes: The quenching temperature point was determined based on the axial temperature distribution data from the preliminary experiment. The proportional coefficient is determined by regression fitting of the actual water level and differential pressure water level corresponding to the quenching temperature point with the real-time water level.

2. The method for dynamic control of water level in locally exposed and re-submerged areas within a high-temperature flow channel according to claim 1, characterized in that, The differential pressure taps are installed at the inlet and outlet positions of the pre-experiment flow channel.

3. The method for dynamic control of water level in locally exposed and re-submerged areas within a high-temperature flow channel according to claim 1, characterized in that, The effective heating section of the heating plate is equipped with an optical fiber temperature sensor to measure the axial temperature distribution.

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