Method for calculating fracture critical flow of internal coil pipe of high-pressure cooler

Abstract

The invention relates to a method for calculating fracture critical flow of an internal coil pipe of a high-pressure cooler, and belongs to the field of nuclear engineering. The method comprises the steps that cracking leakage of a high-pressure cooler inner coil pipe is modeled into spraying pipe flowing, a high-pressure cooler shell side back pressure critical value is considered, the working medium flow state under the high-pressure cooler coil pipe cracking working condition is divided into single-phase flowing and two-phase flowing, and the single-phase area mass flow rate # imgabs0 # and the flow speed v when the high-pressure cooler inner coil pipe is cracked are calculated through a Bernoulli equation; and calculating the mass flow rate # imgabs1 # and the flow velocity v of the two-phase region when the coil pipe in the high-pressure cooler is broken by using an isentropic stagnation flow formula, and considering the sound velocity limit c in the two-phase region. The method provides an effective and complete theoretical basis for calculating the maximum flow rate when the internal coil pipe of the high-pressure cooler breaks, is suitable for calculating the flow rate when the internal coil pipe of all the high-pressure coolers breaks, is small in calculation conclusion error, is high in theoretical basis credibility, and is suitable for large-scale popularization and application. And the method is suitable for engineering practice of nuclear power and military industries with design requirements and strict requirements.

Description

Technical Field

[0001] The invention relates to a method for calculating a critical flow rate of a coil rupture inside a high-pressure cooler, and belongs to the field of nuclear engineering. Background Art

[0002] The design of the emergency shaft seal injection water system of the shaft seal type nuclear main pump is usually equipped with an external shell and tube type high-pressure cooler to cool and exchange the emergency injection water, so as to ensure that the water temperature entering the shaft seal is within the allowable range. However, when the internal coil welding of the high-pressure cooler is broken or damaged in other places, it will cause leakage of the high-pressure cooler, which is difficult to detect and it is impossible to accurately understand the maximum flow rate when the internal coil of the high-pressure cooler is broken. At present, the calculation of the maximum flow rate of the high-pressure cooler rupture mostly relies on empirical formulas in China. The calculation conclusion has a large error and lacks theoretical basis. The credibility is low, and it is difficult to apply to engineering practice, especially for the nuclear power and military industries with extremely strict design requirements. Summary of the invention

[0003] In order to solve the problem that the maximum flow cannot be estimated when the internal coil of the high-pressure cooler of the shaft seal type nuclear main pump is broken, the present invention discloses a method for calculating the critical flow of the internal coil rupture of the high-pressure cooler, and provides an effective and complete theoretical basis for calculating the maximum flow when the internal coil of the high-pressure cooler is broken.

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] A method for calculating the critical flow rate of a high-pressure cooler internal coil rupture, characterized in that the method for calculating the critical flow rate under the condition of a high-pressure cooler internal coil rupture comprises the following specific steps:

[0006] Step 1: Input the internal coil size, system temperature and system pressure parameters of the high-pressure cooler into Matlab;

[0007] Step 2: Use Matlab to call the Refprop physical property database to calculate the density, entropy, enthalpy and saturation pressure corresponding to the internal coil rupture of the high-pressure cooler;

[0008] Step 3: Use Matlab to call the Refprop physical property database calculation system to obtain the high-pressure cooler shell side back pressure P in the range of 15990 kPa to 1000 kPa through a for loop, with a change interval of 10 kPa, and determine the relative size of the back pressure P and the saturation pressure in the isentropic process;

[0009] Step 4: (1) When the back pressure P in step 3 is greater than or equal to the saturation pressure in the isentropic process, the working medium flow state under the high-pressure cooler tube rupture condition is single-phase flow, and the Bernoulli equation is used to calculate the mass flow rate when the high-pressure cooler tube ruptures;

[0010] (2) When the back pressure P in step 3 is less than the saturation pressure in the isentropic process, the working fluid flow state under the high-pressure cooler tube rupture condition is a two-phase flow. The two-phase region isentropic stagnant flow formula is used to calculate the mass flow rate of the two-phase region when the internal coil of the high-pressure cooler is ruptured. and flow velocity v;

[0011] Step 5: When leakage occurs in the coil inside the high-pressure cooler, the liquid flow velocity will not exceed the speed of sound. Therefore, the maximum liquid outlet velocity can be obtained at the narrowest section at the fracture. Therefore, the pressure at which the outlet velocity v is greater than the speed of sound c is the critical pressure p. c ;

[0012] If the fluid is a two-phase flow, it is necessary to determine whether the flow velocity calculated in step 4 is greater than or equal to the local sound velocity. If the flow velocity is less than the local sound velocity, the mass flow rate when the internal coil of the high-pressure cooler ruptures is the result of the isentropic stagnant flow formula. If the flow velocity is greater than or equal to the local sound velocity, the mass flow rate when the internal coil of the high-pressure cooler ruptures is the sound velocity multiplied by the density of the working fluid at the rupture. If the fluid is a single-phase flow, the mass flow rate when the internal coil of the high-pressure cooler ruptures is the fluid velocity at the rupture multiplied by the density.

[0013] The present invention provides a method for calculating the critical flow rate of a high-pressure cooler internal coil rupture. In step 4, the mass flow rate when the high-pressure cooler is ruptured is calculated using the Bernoulli equation as follows:

[0014] One-way zone Bernoulli equation:.

[0015] Assuming that the coil inside the high-pressure cooler is an incompressible ideal fluid and there is no heat exchange with the outside world, the Bernoulli equation is:

[0016]

[0017] Therefore, the Bernoulli equation is satisfied between any two points in the coil of the high-pressure cooler, that is:

[0018]

[0019] Where v is velocity, m / s; g is acceleration due to gravity, m / s 2 ; z is the height of the fluid, m; p is the pressure, Pa; ρ is the fluid density, kg / m 3 ; Corner marks 1 and 2 represent any two points of the coil inside the high pressure cooler;

[0020] The working fluid flow state in the coil inside the high-pressure cooler is adiabatic single-phase flow, the change of fluid density can be ignored, that is, ρ1=ρ2=ρ, and the height change at the position of the fluid is ignored, that is, z1=z2, and the leakage port is in a stagnant state v1=0m / s. Substituting the above parameters into formula (2), the liquid pressure at any point 1 when the coil inside the high-pressure cooler ruptures is:

[0021]

[0022] Mass flow rate is the mass of fluid passing through the cross section per unit time, and the calculation formula is:

[0023]

[0024] in, is the mass flow rate, kg / s; ρ is the fluid density, kg / m 3 ; v is speed, m / s

[0025] Substituting formula (3) into formula (4) yields the mass flow rate at any second point when the coil inside the high-pressure cooler ruptures: and flow velocity v are:

[0026]

[0027] The present invention provides a method for calculating the critical flow rate of the internal coil rupture of a high-pressure cooler. In step 4, the two-phase region isentropic stagnant flow formula is used to calculate the mass flow rate of the two-phase region when the internal coil of the high-pressure cooler ruptures. and flow velocity v:

[0028] Isentropic stagnation flow formula in two-phase region:

[0029] When the leakage flow after the internal coil of the high-pressure cooler is completely ruptured can be modeled as nozzle flow, and the leakage process has a short path and a short time, which can be considered as a steady-state isentropic expansion process. The stable flow energy equation between any two points of the internal coil of the high-pressure cooler is:

[0030]

[0031] Where q is the heat exchanged with the outside world during the flow process, W; h is the enthalpy value carried by the fluid, J / kg; w net is the work done by the flow process on the outside world, W; v is the velocity, m / s; g is the gravitational acceleration, m / s 2 ; z is the height of the fluid position, m; subscripts 1 and 2 are any two points of the fluid in the high-pressure cooler coil when the internal coil of the high-pressure cooler is completely ruptured;

[0032] After the internal coil of the high-pressure cooler is completely ruptured, q=0, v1=0, Δz=0 and w net =0, and h2 is the enthalpy value of the high-pressure cooler shell side back pressure isentropic process corresponding to h1, so formula (7) can be simplified as:

[0033]

[0034] That is, the flow velocity v at this time is:

[0035]

[0036] The mass flow rate in the isentropic stagnant flow process is for:

[0037]

[0038] The present invention provides a method for calculating the critical flow rate of a coil rupture inside a high-pressure cooler, wherein the speed of sound c in step 5 is:

[0039] The empirical formula for the speed of sound is:

[0040]

[0041] In Matlab, Refprop is called to calculate the change of density with pressure in the isentropic process of the system, and the polynomial fitting formula is used to derive the obtained formula to obtain the speed of sound used. value.

[0042] The present invention has the following beneficial effects:

[0043] The method for calculating the critical flow rate when the internal coil of a high-pressure cooler breaks of the present invention provides an effective and complete theoretical basis for calculating the maximum flow rate when the internal coil of a high-pressure cooler breaks. The method is applicable to the calculation of the flow rate when the internal coil of all high-pressure coolers breaks. The calculation conclusion has a small error and a high credibility of the theoretical basis. The method is applicable to the engineering practice of the nuclear power and military industries with extremely strict design requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0045] Figure 1 It is a flow chart of a method for calculating the maximum flow rate of a high-pressure cooler coil rupture condition according to the present invention;

[0046] Figure 2 It is a schematic diagram of the internal coil of the high pressure cooler in the present invention;

[0047] Figure 3 It is a schematic diagram of the maximum rupture nozzle of the internal coil of the high pressure cooler of the present invention;

[0048] Figure 4 is the temperature-entropy-dryness-enthalpy diagram of water and water vapor in the present invention;

[0049] Figure 5 is a water and water vapor partition diagram in the present invention;

[0050] Figure 6 It is the curve of density variation with pressure of the system parameter isentropic process in the present invention;

[0051] Figure 7 It is the "back pressure-flow rate" relationship curve when the internal coil of the high pressure cooler in the present invention breaks;

[0052] Figure 8 It is the "back pressure-flow rate" relationship curve when the internal coil of the high-pressure cooler in the present invention breaks. DETAILED DESCRIPTION

[0053] The present invention will now be further described in detail with reference to embodiments.

[0054] Embodiment 1: Figure 1-8 As shown in the figure, a flow chart of a method for calculating the maximum flow rate under the condition of internal coil rupture of a high-pressure cooler is provided. By carefully modeling the flow after the high-pressure cooler coil ruptures, a nozzle flow model is adopted, and the corresponding fluid mechanics equations are used for calculation according to the different fluid flow properties (single-phase flow and two-phase flow), the influence of the sonic velocity limitation and the critical value of the shell side back pressure are particularly considered, so as to accurately predict the critical flow rate when the coil ruptures. The specific steps of the method for calculating the critical flow rate under the condition of internal coil rupture of the high-pressure cooler are as follows:

[0055] Step 1: Input the internal coil size, system temperature and system pressure parameters of the high-pressure cooler into Matlab;

[0056] Step 2: Use Matlab to call the Refprop physical property database to calculate the density, entropy, enthalpy and saturation pressure corresponding to the internal coil rupture of the high-pressure cooler;

[0057] Step 3: Use Matlab to call the Refprop physical property database calculation system to obtain the high-pressure cooler shell side back pressure P in the range of 15990 kPa to 1000 kPa through a for loop, with a change interval of 10 kPa, and determine the relative size of the back pressure P and the saturation pressure in the isentropic process;

[0058] Step 4: (1) When the back pressure P in step 3 is greater than or equal to the saturation pressure in the isentropic process, the working fluid flow state under the high-pressure cooler tube rupture condition is single-phase flow. The Bernoulli equation is used to calculate the mass flow rate when the high-pressure cooler tube ruptures:

[0059] One-way zone Bernoulli equation:.

[0060] Assuming that the coil inside the high-pressure cooler is an incompressible ideal fluid and there is no heat exchange with the outside world, the Bernoulli equation is:

[0061]

[0062] Therefore, the Bernoulli equation is satisfied between any two points in the coil of the high-pressure cooler, that is:

[0063]

[0064] Where v is velocity, m / s; g is acceleration due to gravity, m / s 2 ; z is the height of the fluid, m; p is the pressure, Pa; ρ is the fluid density, kg / m 3 ; Corner marks 1 and 2 represent any two points of the coil inside the high pressure cooler;

[0065] The working fluid flow state in the coil inside the high-pressure cooler is adiabatic single-phase flow, the change of fluid density can be ignored, that is, ρ1=ρ2=ρ, and the height change at the position of the fluid is ignored, that is, z1=z2, and the leakage port is in a stagnant state v1=0m / s. Substituting the above parameters into formula (2), the liquid pressure at any point 1 when the coil inside the high-pressure cooler ruptures is:

[0066]

[0067] Mass flow rate is the mass of fluid passing through the cross section per unit time, and the calculation formula is:

[0068]

[0069] in, is the mass flow rate, kg / s; ρ is the fluid density, kg / m 3 ; v is speed, m / s

[0070] Substituting formula (3) into formula (4) yields the mass flow rate at any second point when the coil inside the high-pressure cooler ruptures: and flow velocity v are:

[0071]

[0072] (2) When the back pressure P in step 3 is less than the saturation pressure in the isentropic process, the working fluid flow state under the high-pressure cooler tube rupture condition is a two-phase flow. The two-phase region isentropic stagnant flow formula is used to calculate the mass flow rate of the two-phase region when the internal coil of the high-pressure cooler is ruptured. and flow velocity v:

[0073] Isentropic stagnation flow formula in two-phase region:

[0074] When the leakage flow after the internal coil of the high-pressure cooler is completely ruptured can be modeled as nozzle flow, and the leakage process has a short path and a short time, which can be considered as a steady-state isentropic expansion process. The stable flow energy equation between any two points of the internal coil of the high-pressure cooler is:

[0075]

[0076] Where q is the heat exchanged with the outside world during the flow process, W; h is the enthalpy value carried by the fluid, J / kg; w net is the work done by the flow process on the outside world, W; v is the velocity, m / s; g is the gravitational acceleration, m / s 2 ; z is the height of the fluid position, m; subscripts 1 and 2 are any two points of the fluid in the high-pressure cooler coil when the internal coil of the high-pressure cooler is completely ruptured;

[0077] After the internal coil of the high-pressure cooler is completely ruptured, q=0, v1=0, Δz=0 and w net =0, and h2 is the enthalpy value of the high-pressure cooler shell side back pressure isentropic process corresponding to h1, so formula (7) can be simplified as:

[0078]

[0079] That is, the flow velocity v at this time is:

[0080]

[0081] The mass flow rate in the isentropic stagnant flow process is for:

[0082]

[0083] Step 5: When leakage occurs in the coil inside the high-pressure cooler, the liquid flow velocity will not exceed the speed of sound. Therefore, the maximum liquid outlet velocity can be obtained at the narrowest section at the fracture. Therefore, the pressure at which the outlet velocity v is greater than the speed of sound c is the critical pressure p. c ;

[0084] The empirical formula for the speed of sound is:

[0085]

[0086] In Matlab, Refprop is called to calculate the change of density with pressure in the isentropic process of the system, and the polynomial fitting formula is used to derive the obtained formula to obtain the speed of sound used. Value (see Figure 6 : System parameter isentropic process density variation curve with pressure);

[0087] If the fluid is a two-phase flow, it is necessary to determine whether the flow velocity calculated in step 4 is greater than or equal to the local sound velocity. If the flow velocity is less than the local sound velocity, the mass flow rate when the coil inside the high-pressure cooler ruptures is the result of the isentropic stagnant flow formula. If the flow velocity is greater than or equal to the local sound velocity, the mass flow rate when the coil inside the high-pressure cooler ruptures is the sound velocity multiplied by the density of the working fluid at the rupture. If the fluid is a single-phase flow, the mass flow rate when the coil inside the high-pressure cooler ruptures is the fluid velocity at the rupture multiplied by the density.

[0088] Step 6: According to steps 1-5, the mass flow rate under different working conditions when the internal coil of the high-pressure cooler is ruptured is obtained and flow velocity v, and the critical mass of rupture is obtained by comparing the flow state and flow velocity with the speed of sound.

[0089] Embodiment 2: Figure 1-8 As shown in FIG. 1 , a method for calculating the maximum flow rate of a high-pressure cooler internal coil rupture condition is used. When the liquid inside the high-pressure cooler is in critical flow, when the pressure (back pressure) on the shell side of the high-pressure cooler reaches a critical value, the flow rate of the high-pressure cooler internal coil leakage reaches a maximum value Q max , which is the critical flow rate. Due to the short path and short time of the leakage process, the leakage process can be considered as an isentropic expansion process. The actual back pressure on the shell side of the high-pressure cooler cannot be accurately obtained, and the inflowing fluid may cause the shell side pressure to increase. Therefore, in this calculation method, the back pressure of the high-pressure cooler is set as the dependent variable, and it is changed from the system pressure (p0=16MPa) to 1MPa, and the pressure update step is 10kPa. The leakage flow of the high-pressure cooler under different back pressure conditions is analyzed.

[0090] The internal coil diagram of the high pressure cooler is as follows: Figure 2 As shown, the schematic diagram of the maximum rupture nozzle of the internal coil is as follows Figure 3 shown.

[0091] At the discharge outlet, the coil fluid inside the high-pressure cooler is a supercooled fluid, the temperature is the system temperature (293°C), and the pressure system pressure (16MPa) corresponds to the isentropic process saturation pressure of 7.41MPa, so the tube side fluid is a supercooled fluid under the system parameters. During the discharge, when the shell side back pressure is greater than the saturation pressure corresponding to the process, the discharge is a single-phase flow; when the shell side back pressure of the high-pressure cooler is less than the corresponding saturation pressure, it is a two-phase flow. In this method for calculating the maximum flow rate under the high-pressure cooler coil rupture condition, if the internal coil of the high-pressure cooler is a single-phase flow, the Bernoulli equation is used to deduce the leakage flow of the internal coil of the high-pressure cooler; if the internal coil of the high-pressure cooler is a two-phase flow, the isentropic stagnant flow formula is used and the local sound velocity is used as a constraint to derive the leakage flow of the internal coil of the high-pressure cooler:

[0092] 1. One-way zone Bernoulli equation:

[0093] Assuming that the coil inside the high-pressure cooler is an incompressible ideal fluid and there is no heat exchange with the outside world, the Bernoulli equation is:

[0094]

[0095] Therefore, the Bernoulli equation is satisfied between any two points in the coil of the high-pressure cooler, that is:

[0096]

[0097] Where v is velocity, m / s; g is acceleration due to gravity, m / s 2 ; z is the height of the fluid, m; p is the pressure, Pa; ρ is the fluid density, kg / m 3 ; Corner marks 1 and 2 represent any two points inside the high-pressure cooler coil.

[0098] The liquid in the coil inside the high-pressure cooler is an adiabatic single-phase flow, and the change in fluid density can be ignored, that is, ρ1=ρ2=ρ, and the height change at the location of the fluid is ignored, that is, z1=z2, and the leakage port is in a stagnant state v1=0m / s. Substituting the above parameters into formula (13), the liquid pressure at any point 1 when the coil inside the high-pressure cooler ruptures is:

[0099]

[0100] Mass flow rate is the mass of fluid passing through the cross section per unit time, and the calculation formula is:

[0101]

[0102] in, is the mass flow rate, kg / s; ρ is the fluid density, kg / m 3 ; v is speed, m / s

[0103] Substituting formula (14) into formula (15) can obtain the mass flow rate at any second point when the coil inside the high-pressure cooler ruptures: and flow velocity v are:

[0104]

[0105] 2. Isentropic stagnation flow equation in two-phase region

[0106] When the leakage flow after the internal coil of the high-pressure cooler is completely ruptured can be modeled as nozzle flow, and the leakage process has a short path and a short time, which can be considered as a steady-state isentropic expansion process. The stable flow energy equation between any two points of the internal coil of the high-pressure cooler is:

[0107]

[0108] Where q is the heat exchanged with the outside world during the flow process, W; h is the enthalpy value carried by the fluid, J / kg; w net is the work done by the flow process on the outside world, W; v is the velocity, m / s; g is the gravitational acceleration, m / s 2 ; z is the height of the fluid, m; subscripts 1 and 2 are any two points of the fluid when the coil inside the high-pressure cooler is completely ruptured.

[0109] After the internal coil of the high-pressure cooler of the present invention is completely ruptured, q=0, v1=0, Δz=0 and w in formula (18) net =0, and h2 is the enthalpy value of the high-pressure cooler shell side back pressure isentropic process corresponding to h1. Therefore, formula (18) can be simplified as:

[0110]

[0111] That is, the flow velocity v at this time is:

[0112]

[0113] The mass flow rate in the isentropic stagnant flow process is for:

[0114]

[0115] 3. Speed ​​of sound limit

[0116] When leakage occurs in the coil inside the high-pressure cooler, the liquid flow velocity will not exceed the speed of sound. Therefore, the maximum liquid outlet velocity can be obtained at the narrowest section at the fracture. Therefore, the pressure at which the outlet velocity v is greater than the speed of sound c is the critical pressure p. c .

[0117] The empirical formula for the speed of sound is:

[0118]

[0119] In Matlab, Refprop is called to calculate the change of density with pressure in the isentropic process of the system, and the polynomial fitting formula is used to derive the obtained formula to obtain the speed of sound used. s Value (see Figure 6 : System parameter isentropic process density variation curve with pressure).

[0120] The Bernoulli equation is used to calculate the mass flow rate when a pipe breaks inside the high-pressure cooler and a one-way flow occurs. and flow velocity v, the mass flow rate is calculated using the isentropic stagnant flow formula for two-phase flow The velocity v is used to constrain the mass flow rate of the two-phase flow, thereby improving the accuracy and applicability of the calculation method in this paper. The maximum velocity of the fluid will not exceed the velocity of sound when the nozzle effect is considered. Finally, the "back pressure-flow rate" characteristic curve and "back pressure-flow rate" characteristic curve of the fluid when the coil inside the high-pressure cooler is ruptured are obtained as follows: Figure 7 and Figure 8 shown.

[0121] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for calculating the critical flow rate of a coil rupture in a high-pressure cooler, characterized in that: The specific steps of the critical flow calculation method under the condition of internal coil rupture of the high-pressure cooler are: Step 1: Input the internal coil size, system temperature and system pressure parameters of the high-pressure cooler into Matlab; Step 2: Use Matlab to call the Refprop physical property database to calculate the density, entropy, enthalpy and saturation pressure corresponding to the internal coil rupture of the high-pressure cooler; Step 3: Use Matlab to call the Refprop physical property database calculation system to obtain the high-pressure cooler shell side back pressure P in the range of 15990 kPa to 1000 kPa through a for loop, with a change interval of 10 kPa, and determine the relative size of the back pressure P and the saturation pressure in the isentropic process; Step 4: (1) When the back pressure P in step 3 is greater than or equal to the saturation pressure in the isentropic process, the working medium flow state under the high-pressure cooler tube rupture condition is single-phase flow, and the Bernoulli equation is used to calculate the mass flow rate when the high-pressure cooler tube ruptures; (2) When the back pressure P in step 3 is less than the saturation pressure in the isentropic process, the working fluid flow state under the high-pressure cooler tube rupture condition is a two-phase flow. The two-phase region isentropic stagnant flow formula is used to calculate the mass flow rate of the two-phase region when the internal coil of the high-pressure cooler is ruptured. and flow velocity v; Step 5: When leakage occurs in the coil inside the high-pressure cooler, the liquid flow velocity will not exceed the speed of sound. Therefore, the maximum liquid outlet velocity can be obtained at the narrowest section at the fracture. Therefore, the pressure at which the outlet velocity v is greater than the speed of sound c is the critical pressure p. c ; If the fluid is a two-phase flow, it is necessary to determine whether the flow velocity calculated in step 4 is greater than or equal to the local sound velocity. If the flow velocity is less than the local sound velocity, the mass flow rate when the internal coil of the high-pressure cooler ruptures is the result of the isentropic stagnant flow formula. If the flow velocity is greater than or equal to the local sound velocity, the mass flow rate when the internal coil of the high-pressure cooler ruptures is the sound velocity multiplied by the density of the working fluid at the rupture. If the fluid is a single-phase flow, the mass flow rate when the internal coil of the high-pressure cooler ruptures is the fluid velocity at the rupture multiplied by the density.

2. A method for calculating the critical flow rate of internal coil rupture of a high-pressure cooler according to claim 1, characterized in that: In step 4, the Bernoulli equation is used to calculate the mass flow rate of the high-pressure cooler when the tube is broken: One-way zone Bernoulli equation:. Assuming that the coil inside the high-pressure cooler is an incompressible ideal fluid and there is no heat exchange with the outside world, the Bernoulli equation is: Therefore, the Bernoulli equation is satisfied between any two points in the coil of the high-pressure cooler, that is: Where v is velocity, m / s; g is acceleration due to gravity, m / s 2 ; z is the height of the fluid, m; p is the pressure, Pa; ρ is the fluid density, kg / m 3 ; Corner marks 1 and 2 represent any two points of the coil inside the high pressure cooler; The working fluid flow state in the coil inside the high-pressure cooler is adiabatic single-phase flow, the change of fluid density can be ignored, that is, ρ1=ρ2=ρ, and the height change at the position of the fluid is ignored, that is, z1=z2, and the leakage port is in a stagnant state v1=0m / s. Substituting the above parameters into formula (2), the liquid pressure at any point 1 when the coil inside the high-pressure cooler ruptures is: Mass flow rate is the mass of fluid passing through the cross section per unit time, and the calculation formula is: in, is the mass flow rate, kg / s; ρ is the fluid density, kg / m 3 ; v is speed, m / s Substituting formula (3) into formula (4) yields the mass flow rate at any second point when the coil inside the high-pressure cooler ruptures: and flow velocity v are:

3. The method for calculating the critical flow rate of internal coil rupture of a high-pressure cooler according to claim 1, characterized in that: In step 4, the two-phase region isentropic stagnant flow formula is used to calculate the mass flow rate of the two-phase region when the internal coil of the high-pressure cooler is ruptured. and flow velocity v: Isentropic stagnation flow formula in two-phase region: When the leakage flow after the internal coil of the high-pressure cooler is completely ruptured can be modeled as nozzle flow, and the leakage process has a short path and a short time, which can be considered as a steady-state isentropic expansion process. The stable flow energy equation between any two points of the internal coil of the high-pressure cooler is: Where q is the heat exchanged with the outside world during the flow process, W; h is the enthalpy value carried by the fluid, J / kg; w net is the work done by the flow process on the outside world, W; v is the velocity, m / s; g is the gravitational acceleration, m / s 2 ; z is the height of the fluid position, m; subscripts 1 and 2 are any two points of the fluid in the high-pressure cooler coil when the internal coil of the high-pressure cooler is completely ruptured; After the internal coil of the high-pressure cooler is completely ruptured, q=0, v1=0, Δz=0 and w net =0, and h2 is the enthalpy value of the high-pressure cooler shell side back pressure isentropic process corresponding to h1, so formula (7) can be simplified as: That is, the flow velocity v at this time is: The mass flow rate in the isentropic stagnant flow process is for:

4. A method for calculating the critical flow rate of internal coil rupture of a high-pressure cooler according to claim 1, characterized in that: The speed of sound c in step 5 is: The empirical formula for the speed of sound is: In Matlab, Refprop is called to calculate the change of density with pressure in the isentropic process of the system, and the polynomial fitting formula is used to derive the obtained formula to obtain the speed of sound used. value.

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