Method for optimizing discharge experiment system with flash evaporation effect

Abstract

The invention relates to a method for optimizing a discharge experiment system with a flash effect, which comprises the following steps of: calculating the container volume of the discharge experiment system to be optimized based on a container discharge process isentropic equation by combining a saturated water flash energy conservation equation, a saturated water mass conservation equation and a discharge mass flow rate similarity equation; according to the two-fluid non-uniform and non-equilibrium state model, a critical flow model and a steam condensation model are combined, and thermal hydraulic parameters of the container and the pipeline are obtained through calculation; calculating a wave load and a thrust load according to the thermal hydraulic parameters to obtain the total load stress of the pipeline; the pressure load of the wall surface of the pool is calculated by utilizing the discharge pressure of a pipeline outlet, a bubble oscillation equation and a Rayleigh bubble analysis equation, and the optimization of the discharge experiment system is realized by judging whether the mechanical load of the pipeline and the pressure load of the wall surface of the pool meet requirements or not. According to the method, the pipeline mechanical load and the pool wall surface pressure load are obtained through calculation by combining a two-fluid non-uniform and non-equilibrium state model with a critical flow model, a steam condensation model, a bubble oscillation equation and a Rayleigh bubble analysis equation.

Description

Technical Field

[0001] The present invention relates to a technology in the field of reactors, in particular to an optimization method for a discharge experiment system including a flash evaporation effect. Background Art

[0002] As a dedicated safety facility, the safety relief system can provide overpressure protection for the reactor coolant system. When simulating the pressure load on the pool wall during the initial emptying stage of relief, it is necessary to ensure that the mass flow rate of the relief test container is consistent with the mass flow rate of the prototype pressurizer. Experiments usually use small-volume containers instead of pressurizers to conduct safety relief experiments to achieve the same effect or economy under similar conditions. Due to the small volume of the experimental container, the steam flow rate will decrease at a relatively fast rate during the relief process, while the steam flow rate of the pressurizer decreases slowly during relief. In the relief test, how to design the capacity of the experimental container and ensure that the mass flow rate of the exhaust gas is similar to that of the prototype within the specified time is a key issue in correctly simulating the mechanical shock load during safety relief. Summary of the Invention

[0003] In response to the shortcomings of existing technologies that are unable to measure and calculate the impact of high-speed two-phase fluid on pipelines and water pool walls during high-pressure discharge, and unable to characterize the mechanical load conditions of pipelines and water pools during the discharge process, the present invention proposes a discharge experimental system optimization method with flash evaporation effect. By combining the non-uniform and non-equilibrium state model of two fluids with the critical flow model and the steam condensation model as well as the bubble oscillation equation and the Rayleigh bubble analysis equation, the mechanical load on the pipeline and the pressure load on the water pool wall are calculated.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to an optimization method for a discharge experiment system with a flash evaporation effect. The method comprises the following steps: by simultaneously establishing a saturated water flash evaporation energy conservation equation, a saturated water mass conservation equation, and a discharge mass flow rate similarity equation, and calculating the container volume of the discharge experiment system to be optimized based on an isentropic equation of the container discharge process; calculating the thermal-hydraulic parameters of the container and the pipeline based on a two-fluid non-uniform non-equilibrium state model combined with a critical flow model and a steam condensation model; calculating the wave load and the thrust load based on the thermal-hydraulic parameters to obtain the total load stress of the pipeline; and calculating the water pool wall pressure load based on the pipeline outlet discharge pressure, a bubble oscillation equation, and a Rayleigh bubble analysis equation. The discharge experiment system is optimized by judging whether the pipeline mechanical load and the water pool wall pressure load meet the requirements.

[0006] The discharge test system includes: a discharge test container, a high-pressure steam generator, a flow meter, an electric regulating valve, a check valve, a safety valve, a quick-opening ball valve, a vacuum breaking valve, a gas cylinder group, a bubbler, a pressure suppression pool, a strain sensor, and a pressure sensor.

[0007] The energy conservation of saturated water flash evaporation refers to: The saturated water mass conservation equation is: The discharge mass flow rate is similar The steam mass m of saturated water flash is calculated by combining the above equations. g-2 , where: l is the density of saturated water, m l and m g are the masses of saturated water and saturated steam, respectively, H l and H g are the specific enthalpies of saturated water and saturated steam, respectively. The subscript P0 indicates that the corresponding parameters in the brackets are all at the pressure P0 corresponding to the saturated water state, and the subscript P1 indicates that the corresponding parameters in the brackets are all at the pressure P0 corresponding to the saturated water state.

[0008] The discharge mass flow rate is: The discharge mass flow rate is similar Where: k0 is the isentropic coefficient when the pressurizer starts to discharge, k1 is the isentropic coefficient after the pressurizer discharges t seconds, ρ0 is the steam density when the pressurizer starts to discharge, ρ1 is the steam density after the pressurizer discharges t seconds, and the isentropic coefficient k=c p / c v , c p is the molar heat capacity at constant pressure, c v is the molar heat capacity at constant volume.

[0009] The isentropic equation for the container discharge process is: Where: k is the isentropic coefficient, ρ i is the density, G0 is the critical flow mass flow rate at the initial pressure P0 and initial density ρ0.

[0010] The container volume of the discharge system Where: G0 is the critical flow mass flow rate under the initial pressure P0 and initial density ρ0, A is the cross-sectional area of ​​the pipe, t is the experimental discharge time, α1 is the water space volume ratio, is the specific enthalpy of saturated water corresponding to pressure P0, is the specific enthalpy of saturated water corresponding to pressure P1, is the density of saturated water corresponding to pressure P0.

[0011] The two-fluid non-uniform non-equilibrium model refers to using a two-fluid, non-uniform, non-equilibrium model to solve the mass, momentum, and energy conservation equations of the vapor and liquid phases, respectively, where the mass conservation equation of the vapor and liquid phases is: The gas-liquid momentum conservation equation is: The gas-liquid energy conservation equation is: Where: g is the gas phase; f is the liquid phase; m is the gas-liquid mixture; w is the wall; i is the gas-liquid interface; A is the cross-sectional area of ​​the flow channel, m 2 ; α is the cavitation fraction; Г is the mass transfer rate, kg / m 3 s; v is the flow velocity, m / s; ρ is the density, kg / m 3 ; FIG and FIF are the drag coefficients of the gas and liquid interfaces, s -1 ; FWG and FWF are the gas-liquid wall drag coefficients, s -1 ; B is the body force term, m / s 2 ; C is the virtual force coefficient; P is the pressure, Pa; Q is the volume heat source, W / m 3 ; U is internal energy, J / kg; h is enthalpy, J / kg; DISS is heat dissipation term, W / m 3 .

[0012] The critical flow model, namely the Henry-Fauske model, is specifically: Where: α HE is the thermal equilibrium sound velocity of the two-phase mixture; α g , ρ g 、v g are respectively the gas phase cavitation fraction, gas phase density and gas phase volume; α f , ρ f 、v f are the liquid phase cavitation fraction, liquid phase density, and liquid phase volume respectively; C pg is the specific heat of saturated steam at constant pressure; C pf is the specific heat of saturated liquid at constant pressure; κ g is the steam isothermal compressibility coefficient; κ f is the isothermal compressibility of the liquid; β g is the isobaric thermal expansion coefficient of steam; β f is the isobaric thermal expansion coefficient of the liquid; P is the fluid pressure.

[0013] The steam condensation model is: Where: P vi is the vapor partial pressure at the gas-liquid interface; T vi is the temperature at the gas-liquid interface; h m is the mass transfer coefficient s; h fgb is the latent heat of vaporization; ρ vb is the steam density in the mixed gas; P vi is the pressure at the gas-liquid interface; P and P vb are the total pressure and the vapor partial pressure in the mixed gas, respectively.

[0014] The thermal hydraulic parameters of the container and pipeline are: density, viscosity, specific heat capacity, flow rate, temperature, pressure, enthalpy and cavitation fraction of steam and water.

[0015] The total pipeline load stress is the sum of wave load, momentum thrust load and outlet pressure difference thrust load, where wave load Where: α g , ρ g 、v g are respectively the gas phase cavitation fraction, gas phase density and gas phase velocity; α f , ρ f 、v f are the liquid phase cavitation fraction, liquid phase density and liquid phase velocity; momentum thrust load in: is the mass flow rate at the pipeline outlet, v e is the outlet flow rate of the pipeline; outlet pressure difference thrust load F p =-(P e -P a )A e , where: P e is the pipeline outlet pressure, P a is atmospheric pressure, A e is the pipe flow area.

[0016] The bubble oscillation equation is: Where: ν1 is the kinematic viscosity of the liquid, p gas,0 is the bubble diameter corresponding to the reference bubble diameter R0, p ∞ Add the hydrostatic pressure to the atmospheric pressure.

[0017] The Rayleigh bubble analysis equation is: Δp1=p1-p ∞ , Δp b =p b -p ∞ , where: p1 and p b are the pool oscillation pressure and bubble pressure respectively, R is the bubble diameter, is the velocity of bubble diameter change.

[0018] The pressure load on the pool wall is specifically: the load formed on the wall by the pool oscillation pressure and hydrostatic pressure. Technical Effects

[0019] Compared to existing technologies, this method designs the experimental vessel and discharge system based on similar discharge mass flow rates by considering the flash effect. It also derives the discharge system's thermal-hydraulic parameters based on a two-fluid, non-uniform, non-equilibrium model, a critical flow model, and a steam condensation model containing non-condensable gases. Based on these thermal-hydraulic parameters, the total pipeline load is calculated through wave load, momentum thrust load, and pressure differential thrust load calculations. The tank wall load is also calculated based on bubble vibration characteristics. This complete method provides a method and reference for the design of discharge system simulation vessels, pipelines, and tanks. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flowchart of the present invention;

[0021] Figure 2 Schematic diagram of the discharge experiment system;

[0022] In the figure: 1 discharge test vessel, 2 high-pressure steam generator, 3 flow meter, 4 electric regulating valve, 5 check valve, 6 safety valve, 7 quick-opening ball valve, 8 vacuum breaker valve, 9 gas cylinder assembly, 10 bubbler, 11 pressure suppression pool, 12 strain sensor, 13 pressure sensor;

[0023] Figure 3 This is the calculation diagram of the pressure drop model considering the flash effect;

[0024] Figure 4 This is the strain response diagram of the pool wall during the emptying stage of the discharge system;

[0025] Figure 5 This is the experimental and calculated results of the pool pressure response during the emptying phase of the discharge system. In the figure: the red line is the bubble oscillation calculation result, and the black line is the experimental result. DETAILED DESCRIPTION

[0026] like Figure 1 As shown, this embodiment relates to an optimization method for a discharge experiment system including a flash evaporation effect, including:

[0027] Step 1: Design the experimental container, including:

[0028] 1.1 Determine the experimental discharge time, initial discharge pressure, water space volume ratio, and pressurizer mass flow rate change rate as the initial conditions for calculation;

[0029] 1.2 Calculate the discharge end pressure by using the pressure estimation formula;

[0030] 1.3 According to the conservation of energy and mass in the flash evaporation process of saturated water, calculate the steam mass of saturated water flash evaporation in the container under constant pressure drop:

[0031] 1.4 Calculate the critical flow rate in the initial state;

[0032] 1.5 Calculate the average flash vaporization rate, derive the pressure drop formula for the container considering flash vaporization, and calculate the container volume based on the formula;

[0033] Step 2: Obtain the thermal hydraulic parameters of the discharge system, including: density, viscosity, specific heat capacity, flow rate, temperature, pressure, enthalpy and cavitation fraction of steam and water.

[0034] 2.1 Obtain the container volume and dimensions, discharge system piping layout and dimensions, discharge system pool dimensions, valve layout, number of nozzle openings, and submergence depth;

[0035] 2.2 Obtain the initial pressure, temperature, water level, non-condensable gas content and valve opening time of the container;

[0036] 2.3 Construct a two-fluid non-uniform non-equilibrium model, a critical flow model, and a steam condensation model containing non-condensable gases;

[0037] 2.4 Using the model constructed in step 2.3, calculate the thermal-hydraulic parameters for different vessel volumes and sizes, discharge system piping layouts and sizes, discharge system pool sizes, valve layouts, number of nozzle openings, submergence depths, and different vessel initial pressures, temperatures, water levels, non-condensable gas fractions, and valve opening times.

[0038] Step 3: Pipeline load analysis, including:

[0039] 3.1 Unsteady reaction force (wave load) caused by the rate of change of fluid momentum;

[0040] 3.2 Thrust load caused by momentum flux;

[0041] 3.3 Thrust load caused by the pressure difference between the inlet and outlet of the pipeline;

[0042] 3.4 Pipeline total load stress analysis;

[0043] Step 4: Analysis of the pool wall pressure load, including:

[0044] 4.1 Discharge pressure at the outlet of the discharge system pipeline;

[0045] 4.2 The oscillation equation of bubbles in the water pool is used to calculate the diameter and velocity changes of released bubbles;

[0046] 4.3 Using the Rayleigh bubble analysis equation, calculate the pressure field in the liquid around the oscillating spherical bubble and obtain the pool wall load;

[0047] Step 5: Determine whether the total pipeline load stress is less than the strain and stress requirements of the pipeline material; and whether the pool wall load is less than the strain and stress requirements of the pool material. If not, adjust the system parameters designed in Step 2.4 and recalculate until the requirements are met.

[0048] Step 6. Establish a discharge system simulation experimental loop, arrange pipeline strain and pool pressure measurement points to collect pipeline mechanical loads and pool wall pressure loads during the discharge process to verify the total load results calculated in Step 3 and the pool wall load results calculated in Step 4. Specifically, add strain gauges to the straight and curved sections of the discharge pipeline, and add high-frequency pressure sensors and low-frequency pressure sensors inside the bubbler plume, at the plume boundary, and on the pool wall to detect the pressure inside and on the pool wall.

[0049] After specific actual experiments, under the pressure difference of 10MPa and the container volume of 2.3m 3 Under the conditions of 23% non-condensable gas content, 3.5m nozzle immersion depth, normal temperature and pressure of exhaust gas and pool water, and valve opening time of 1.7s, the pipeline mechanical load and pool wall pressure load were obtained, as shown in Figure 2. Figure 4 and Figure 5 The experimental results are shown.

[0050] At the initial stage of discharge of the discharge test system, the air in the discharge pipe is rapidly compressed under the action of the pressure difference and enters the pressure suppression tank through the nozzle. The bubbles expand rapidly to form an oscillating air cavity, which may cause impact and mechanical damage to the structure and wall of the pressure suppression tank. Emptying is usually a short-term process of 1-2 seconds. When simulating the pressure load on the wall of the tank during the initial emptying stage of discharge, it is necessary to ensure that the mass flow rate of the discharge test container during the emptying time is consistent with the mass flow rate of the prototype of the stabilizer. Therefore, when the gas in the experimental container drops from the saturated state 10MPa to the saturated state P1 within 10 seconds of the experimental discharge time, the mass flow rate change rate of the stabilizer is 96.5%, in order to simulate the emptying and subsequent steam jet establishment process. The saturated state P1 should meet That is, the volume calculation of the experimental container takes into account the discharge process in which the pressure drops from 10 MPa to 8 MPa.

[0051] The initial state of the experimental container is 10MPa, and it is filled with 50% steam gas and 50% saturated water. 3 , the mass of water in 50% of the container volume at 10 MPa saturation state m l = (334.21V) kg. The steam mass of saturated water flashing in the experimental container is m g-2 According to the energy conservation and mass conservation of the flash evaporation process of saturated water, the specific results are: Where: l is the density of saturated water (kg / m 3 ), m l and m g are the masses of saturated water and saturated steam (kg), H l and H g are the specific enthalpies of saturated water and saturated steam (kJ / kg), V is the volume of the experimental container (m 3 ) Combine the above formulas to calculate the amount of steam m of saturated water flashing during the process of saturated water in the experimental container changing from 10MPa saturation state to 8MPa saturation state. g-2 is (21.67V)kg.

[0052] Calculate the discharge flow rate Q according to the initial state during the pressure relief discharge process max , A=3.3×10 -4 m 2 , Q max =G0* A=5.89kg / s, the maximum discharge flow is 5.89kg / s, the expected discharge time is 10 seconds, and the container volume can be obtained That is, the volume of the experimental container is at least 2.09m 3 .

[0053] like Figure 2 As shown, the optimized release test system obtained based on the above method includes: a release test container, a high-pressure steam generator, a gas cylinder group and a pressure suppression water pool, wherein: the high-pressure steam generator and the gas cylinder group are connected to the release test container through a steam supply pipeline and a nitrogen injection pipeline; the pressure suppression water pool is connected to the release test container through a release pipeline, and a bubbler is arranged at the end of the release pipeline water pool.

[0054] According to the above optimization method, the volume of the discharge test container is set to 2.3m 3 Greater than 2.09m 3 , inner diameter is 1000mm, design pressure is 12MPa, and design temperature is 400℃.

[0055] The rated pressure of the steam generator is set to 12 MPa, the rated steam temperature is 324° C., and the rated power is 100 kW.

[0056] The maximum design volume of the pressure suppression pool is set to 35.92m 3 , inner diameter 2.6m, height approximately 7.2m, maximum water depth of the pool 6.51m.

[0057] The bubbler is an I-shaped bubbler with an opening diameter of 10 mm and 192 openings.

[0058] The steam pipeline is located between the steam generator and the discharge test container. The pipeline is arranged with a check valve, an electric regulating valve and a flow meter. Steam is introduced into the discharge test container for pressurization.

[0059] The nitrogen injection pipeline is located between the gas cylinder group and the release test container. The pipeline is arranged with a check valve, an electric regulating valve and a flow meter, and is pressurized by introducing nitrogen into the release test container.

[0060] The discharge pipeline, located between the discharge test vessel and the pressure suppression tank, is equipped with a flow meter, an electric regulating valve, a quick-opening ball valve, and a vacuum breaker valve. The electric regulating valve is used to change the flow area of ​​the discharge pipeline, adjust the discharge flow rate, and simulate the pressure drop characteristics of the safety valve. The quick-opening hydraulic ball valve is used to control the valve's on-off time.

[0061] During the experiment, the release test vessel was pressurized to 10 MPa via a steam generator and nitrogen pipeline. The pressure was then released to the suppression tank via a quick-opening ball valve to simulate the mechanical impact loads associated with a safety release. A geometric model was established based on the design and layout of the release test system's vessel, piping, and bubbler. Based on initial pressure parameters, temperature, and the fraction of noncondensable gases, a two-fluid inhomogeneous, nonequilibrium model was employed to solve the conservation equations for mass, momentum, and energy for the vapor and liquid phases.

[0062] In order to consider the impact of the non-condensable gas fraction on the pipe and pool load, it is assumed that the non-condensable gas is an ideal gas that satisfies the ideal gas state equation. The velocity of the non-condensable gas is equal to the velocity of the vapor phase, and the temperature of the non-condensable gas is equal to the temperature of the vapor phase. That is: v n =v g , T n =T g , where T is temperature, v is velocity, subscript n is the non-condensable gas, and g is the vapor phase. By adding the mass fraction of the non-condensable gas, the mass-energy conservation equation considering the non-condensable gas is established.

[0063] The calculated pressure change of the release test container during release with time is as follows: Figure 3 As shown by the solid line, the pressure of the experimental container changes with time when it is released. Figure 3 Without considering flash evaporation, the pressure change of the experimental container during discharge is calculated as follows: Figure 3 As shown by the dotted line. As can be seen, the predicted results, considering the flash effect, are close to the experimental results for the same volume. However, when the flash effect is not considered, the lack of steam replenishment leads to a faster pressure drop and a significant difference from the experimental results. This method ensures that the mass flow rate of the discharged gas is similar to that of the prototype within the specified time, thereby accurately simulating the mechanical impact loads during the emptying process during safe discharge.

[0064] like Figure 4 and Figure 5As shown in the figure, by analyzing the discharge process of the safety relief system, the hydrodynamic load caused by the exhaust gas on the pool and the pool wall during the emptying stage was obtained. The relevant test results and calculation methods can provide data support for the design of the header and nozzle, and the load of the pipeline and the multi-functional pool.

[0065] Compared with existing technologies, this method calculates the container volume based on the energy and mass conservation equations for saturated water flash evaporation and the similarity of the discharge mass flow rate. It also calculates the thermal-hydraulic parameters of the container and pipeline based on a two-fluid non-uniform, non-equilibrium model combined with a critical flow model and a steam condensation model. It also calculates wave loads, thrust loads, and other factors based on thermal-hydraulic parameters such as pipeline flow rate and pressure differential to obtain the total pipeline load stress. The pressure load on the pool wall is calculated using the pipeline outlet discharge pressure, bubble oscillation equation, and Rayleigh bubble analysis equation. This method can provide a calculation method for the design and analysis of discharge experimental systems.

[0066] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A method for optimizing a discharge test system with a flash evaporation effect, characterized in that: By simultaneously solving the saturated water flash energy conservation equation, the saturated water mass conservation equation, and the discharge mass flow rate similarity equation, the container volume of the discharge experimental system to be optimized is calculated based on the isentropic equation of the container discharge process. The thermal-hydraulic parameters of the container and pipeline are calculated based on the two-fluid non-uniform non-equilibrium state model combined with the critical flow model and steam condensation model. The wave load and thrust load are calculated based on the thermal-hydraulic parameters to obtain the total load stress of the pipeline. The discharge pressure at the pipeline outlet is used, and the bubble oscillation equation and Rayleigh bubble analysis equation are used to calculate the pressure load on the pool wall. By judging whether the mechanical load on the pipeline and the pressure load on the pool wall meet the requirements, the discharge experiment system is optimized.

2. The method for optimizing a discharge test system with a flash vaporization effect according to claim 1, wherein: The discharge test system includes: a discharge test container, a high-pressure steam generator, a flow meter, an electric regulating valve, a check valve, a safety valve, a quick-opening ball valve, a vacuum breaking valve, a gas cylinder group, a bubbler, a pressure suppression pool, a strain sensor, and a pressure sensor.

3. The method for optimizing a discharge test system with a flash vaporization effect according to claim 1, wherein: The energy conservation of saturated water flash evaporation refers to: The saturated water mass conservation equation is: The discharge mass flow rate is similar The steam mass m of saturated water flash is calculated by combining the above equations. g-2 , where: l is the density of saturated water, m l and m g are the masses of saturated water and saturated steam, respectively, H l and H g are the specific enthalpies of saturated water and saturated steam, respectively. The subscript P0 indicates that the corresponding parameters in the brackets are all at the pressure P0 corresponding to the saturated water state. The subscript P1 indicates that the corresponding parameters in the brackets are all at the pressure P0 corresponding to the saturated water state. The discharge mass flow rate is: The discharge mass flow rate is similar Where: k0 is the isentropic coefficient when the pressurizer starts to discharge, k1 is the isentropic coefficient after the pressurizer discharges t seconds, ρ0 is the steam density when the pressurizer starts to discharge, ρ1 is the steam density after the pressurizer discharges t seconds, and the isentropic coefficient k=c p / c v , c p is the molar heat capacity at constant pressure, c v is the molar heat capacity at constant volume; The isentropic equation for the container discharge process is: Where: k is the isentropic coefficient, ρ i is the density, G0 is the critical flow mass flow rate at the initial pressure P0 and initial density ρ0.

4. The method for optimizing a discharge test system with a flash evaporation effect according to claim 1 or 3, wherein: The container volume of the discharge system is: Where: G0 is the critical flow mass flow rate under the initial pressure P0 and initial density ρ0, A is the cross-sectional area of ​​the pipe, t is the experimental discharge time, α1 is the water space volume ratio, is the specific enthalpy of saturated water corresponding to pressure P0, is the specific enthalpy of saturated water corresponding to pressure P1, is the density of saturated water corresponding to pressure P0.

5. The method for optimizing a discharge test system with a flash evaporation effect according to claim 1, wherein: The two-fluid non-uniform non-equilibrium model refers to using a two-fluid, non-uniform, non-equilibrium model to solve the mass, momentum, and energy conservation equations of the vapor and liquid phases, respectively, where the mass conservation equation of the vapor and liquid phases is: The gas-liquid momentum conservation equation is: The gas-liquid energy conservation equation is: Where: g is the gas phase; f is the liquid phase; m is the gas-liquid mixture; w is the wall; i is the gas-liquid interface; A is the cross-sectional area of ​​the flow channel, m 2 ; α is the cavitation fraction; Г is the mass transfer rate, kg / m 3 s; v is the flow velocity, m / s; ρ is the density, kg / m 3 ; FIG and FIF are the drag coefficients of the gas and liquid interfaces, s -1 ; FWG and FWF are the gas-liquid wall drag coefficients, s -1 ; B is the body force term, m / s 2 ; C is the virtual force coefficient; P is the pressure, Pa; Q is the volume heat source, W / m 3 ; U is internal energy, J / kg; h is enthalpy, J / kg; DISS is heat dissipation term, W / m 3 ; The critical flow model, namely the Henry-Fauske model, is specifically: Where: α HE is the thermal equilibrium sound velocity of the two-phase mixture; α g , ρ g 、v g are respectively the gas phase cavitation fraction, gas phase density and gas phase volume; α f , ρ f 、v f are the liquid phase cavitation fraction, liquid phase density, and liquid phase volume respectively; C pg is the specific heat of saturated steam at constant pressure; C pf is the specific heat of saturated liquid at constant pressure; κ g is the steam isothermal compressibility coefficient; κ f is the isothermal compressibility of the liquid; β g is the isobaric thermal expansion coefficient of steam; β f is the isobaric thermal expansion coefficient of the liquid; P is the fluid pressure; The steam condensation model is: Where: P vi is the vapor partial pressure at the gas-liquid interface; T vi is the temperature at the gas-liquid interface; h m is the mass transfer coefficient s; h fgb is the latent heat of vaporization; ρ vb is the steam density in the mixed gas; P vi is the pressure at the gas-liquid interface; P and P vb are the total pressure and the vapor partial pressure in the mixed gas, respectively.

6. The method for optimizing a discharge test system with a flash evaporation effect according to claim 1 or 5, characterized in that: The thermal hydraulic parameters of the container and pipeline are: density, viscosity, specific heat capacity, flow rate, temperature, pressure, enthalpy and cavitation fraction of steam and water.

7. The method for optimizing a discharge test system with a flash vaporization effect according to claim 6, wherein: The total pipeline load stress is the sum of wave load, momentum thrust load and outlet pressure difference thrust load, where wave load Where: α g , ρ g 、v g are respectively the gas phase cavitation fraction, gas phase density and gas phase velocity; α f , ρ f 、v f are the liquid phase cavitation fraction, liquid phase density and liquid phase velocity; momentum thrust load in: is the mass flow rate at the pipeline outlet, v e is the outlet flow rate of the pipeline; outlet pressure difference thrust load F p =-(P e -P a )A e , where: P e is the pipeline outlet pressure, P a is atmospheric pressure, A e is the pipe flow area.

8. The method for optimizing a discharge test system with flash evaporation effect according to claim 1, wherein: The bubble oscillation equation is: Where: ν1 is the kinematic viscosity of the liquid, p gas,0 is the bubble diameter corresponding to the reference bubble diameter R0, p ∞ Add hydrostatic pressure to atmospheric pressure; The Rayleigh bubble analysis equation is: Δp1=p1-p ∞ , Δp b =p b -p ∞ , where: p1 and p b are the pool oscillation pressure and bubble pressure respectively, R is the bubble diameter, is the velocity of change of bubble diameter; The pressure load on the pool wall is specifically: the load formed on the wall by the pool oscillation pressure and hydrostatic pressure.

Images