A method, device and equipment for predicting the critical heat flux of a supercritical light pipe

Abstract

The present invention discloses a method, device and equipment for predicting the critical heat load of a supercritical light tube. When the position coordinate is not less than the length, the preset heat load, inner diameter, mass flow rate, friction coefficient in the heavy fluid region, friction coefficient in the light fluid region, and the pressure, enthalpy and density at the position of the pseudo-saturated liquid are substituted into the pre-established first heat load prediction function to obtain the first transfer function of the light tube pressure drop with respect to the inlet flow velocity; the first transfer function takes into account the density perturbation in the light fluid region; otherwise, the preset heat load, inner diameter, mass flow rate, friction coefficient in the heavy fluid region, friction coefficient in the light fluid region, the pressure, enthalpy and density at the position of the pseudo-saturated liquid, and the pressure, enthalpy and density at the position of the pseudo-saturated vapor are substituted into the pre-established second heat load prediction function to obtain the second transfer function of the light tube pressure drop with respect to the inlet flow velocity. The present invention can accurately predict the critical heat load at which density wave pulsation occurs under supercritical conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal energy engineering, and particularly relates to a method, device and equipment for predicting the critical heat load of supercritical smooth tubes. Background Art

[0002] Thermal power generation is the main mode of electric power production, and the safe and efficient operation of thermal power units is an important guarantee for economic development. In order to meet the rapidly growing power demand while ensuring "lucid waters and lush mountains", large-capacity and high-parameter supercritical and ultra-supercritical once-through boilers are increasingly being adopted, which have the characteristics of high efficiency and low emissions. Facing higher operating parameters and more complex operating conditions compared with subcritical boilers, it is very important to avoid the occurrence of flow instability phenomena in the boiler water wall.

[0003] As one of the common flow instability phenomena, density wave pulsation can occur not only under subcritical conditions but also under supercritical conditions. The reason for the generation of density wave pulsation is that fluids with large density differences appear in the heating section, causing corresponding changes in the heat transfer coefficient and resistance coefficient, and finally reflecting into the pulsation of the system pressure and flow rate. The occurrence of density wave pulsation will induce phenomena such as heat transfer deterioration, tube thermal fatigue, and water wall tube burst, which is of great significance for the design and safe operation of boiler water walls, nuclear power plant steam generators, and other large heat exchange equipment. Therefore, efforts should be made to avoid the occurrence of density wave pulsation during their operation.

[0004] Super (ultra)-critical once-through boilers have the characteristics of high pressure grade, less metal consumption, high operating flexibility, fast startup and shutdown, and strong variable load operation ability, and are more suitable for large-capacity units than traditional drum boilers. However, the water walls of super (ultra)-critical once-through boilers usually adopt tube coils with smaller diameters, and the boiling point in the water wall will change with different boiler loads, which makes it easier for density wave pulsation to occur in the water wall of super (ultra)-critical once-through boilers. Therefore, it becomes very important to predict the critical heat load of density wave pulsation instability in the water wall under super (ultra)-critical conditions.

[0005] Currently, the frequency domain method models for supercritical density wave pulsation are basically improved on the basis of subcritical models. By analogy with the subcooled water zone, two-phase zone, and superheated zone existing in the subcritical heating tube section, the supercritical heating tube section is also divided into three parts, namely the light fluid zone, the light and heavy fluid mixing zone, and the heavy fluid zone. However, the current prediction method ignores the density change in the light fluid zone and treats the fluid in the light fluid zone as an incompressible fluid, which simplifies the operation in the derivation process of the transfer function but correspondingly increases the calculation error. The current prediction method also does not consider the different states of the outlet working medium, resulting in a slightly larger prediction error. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a method, device and equipment for predicting the critical heat load of a supercritical light pipe, which can accurately predict the critical heat load at which density wave pulsation occurs under supercritical conditions.

[0007] To solve the above technical problems, the present invention is achieved through the following technical solutions:

[0008] A method for predicting the critical heat load of a supercritical light pipe, comprising:

[0009] Obtaining the length, inner diameter and inlet throttling degree of the light pipe, as well as the inlet enthalpy value and mass flow rate of the working fluid in the light pipe;

[0010] Obtaining the pressure, enthalpy value and density at the position of the pseudo-saturated liquid, as well as the pressure, enthalpy value, density and position coordinates at the position of the pseudo-saturated vapor;

[0011] Obtaining the friction coefficient in the heavy fluid region, the friction coefficient in the mixed region of heavy and light fluids, and the friction coefficient in the light fluid region;

[0012] When the position coordinate is not less than the length, substituting the preset heat load, the inner diameter, the mass flow rate, the friction coefficient in the heavy fluid region, the friction coefficient in the light fluid region, and the pressure, enthalpy value and density at the position of the pseudo-saturated liquid into a pre-established first heat load prediction function to obtain a first transfer function of the light pipe pressure drop with respect to the inlet flow velocity; the first transfer function takes into account the density perturbation in the light fluid region;

[0013] Converting the first transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a first Nyquist curve, and predicting the critical heat load of the light pipe according to the first Nyquist curve;

[0014] When the position coordinate is less than the length, substituting the preset heat load, the inner diameter, the mass flow rate, the friction coefficient in the heavy fluid region, the friction coefficient in the light fluid region, the pressure, enthalpy value and density at the position of the pseudo-saturated liquid, and the pressure, enthalpy value and density at the position of the pseudo-saturated vapor into a pre-established second heat load prediction function to obtain a second transfer function of the light pipe pressure drop with respect to the inlet flow velocity;

[0015] Converting the second transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a second Nyquist curve, and predicting the critical heat load of the light pipe according to the second Nyquist curve.

[0016] Further, the first heat load prediction function is:

[0017] δΔp(s)=[G0(s)+G1(s)+G2(s)]δu in (s)

[0018] G0(s)=k in ρhm u in

[0019]

[0020] G2(s) = G 21 (s) + G 22 (s) + G 23 (s)

[0021]

[0022] G 22 (s) = X1(s)·Y1(s) + X2(s)·Y2(s)

[0023]

[0024]

[0025]

[0026]

[0027]

[0028] Where: δ is the small perturbation amount; in is the inlet working fluid parameter; hm is the working fluid parameter in the heavy fluid region; Δp is the pressure drop of the entire heating pipe section; G0(s) is the transfer function of the inlet throttle region; G1(s) is the transfer function of the heavy fluid region; G2(s) is the transfer function of the light and heavy fluid mixing region; u in is the inlet velocity of the working fluid; k in is the inlet throttle coefficient; ρ is the density of the working fluid; Z is the flow direction coordinate; s is the complex variable; f1 is the flow friction coefficient in the heavy fluid region; D e is the equivalent diameter of the pipe section; g is the acceleration due to gravity; Ω1 is the axial change rate of the working fluid velocity in the light and heavy fluid mixing region; G is the mass flow rate; L is the loop length; f2 is the flow friction coefficient in the light and heavy fluid mixing region.

[0029] Furthermore, the second heat load prediction function is:

[0030] δΔp(s) = [G0(s) + G1(s) + G'2(s) + G3(s)]δu in (s)

[0031] G0(s) = k in ρ hm u in

[0032]

[0033] G2'(s) = G 21 '(s) + G 22 '(s) + G 23 (s) + G 24 (s)

[0034]

[0035] G 22 '(s) = X1'(s)·Y1(s) + X2'(s)·Y2(s)

[0036]

[0037]

[0038]

[0039]

[0040] G3(s) = G 31 (s) + G 32 (s) + G 33 (s)

[0041]

[0042]

[0043] G 33 (s) = M(s)·a(s) + N(s)·b(s)

[0044]

[0045]

[0046]

[0047]

[0048] Where: δ is the small perturbation amount; in is the inlet working fluid parameter; hm is the working fluid parameter in the heavy fluid region; ml is the working fluid parameter in the light fluid region; Δp is the pressure drop of the entire heating pipe section; G0(s) is the transfer function of the inlet throttling region; G1(s) is the transfer function of the heavy fluid region; G2(s) is the transfer function of the heavy and light fluid mixing region; G3(s) is the transfer function of the light fluid region; u in is the inlet velocity of the working fluid; k in is the inlet throttling coefficient; ρ is the density of the working fluid; Z is the flow direction coordinate; s is the complex variable; f1 is the flow friction coefficient in the heavy fluid region; D e$D_{eq}$ is the equivalent diameter of the pipe segment; $g$ is the acceleration due to gravity; $\Omega_1$ is the axial change rate of the working fluid velocity in the heavy and light fluid mixing zone; $G$ is the mass velocity; $L$ is the loop length; $f_2$ is the flow friction coefficient in the heavy and light fluid mixing zone; $f_3$ is the flow friction coefficient in the light fluid zone; $\Omega_2$ is the axial change rate of the working fluid velocity in the light fluid zone.

[0049] Further, the method for obtaining the friction coefficient of the heavy fluid zone includes:

[0050] Obtain the dynamic viscosity at the pseudo-saturated liquid position;

[0051] Calculate the friction coefficient of the heavy fluid zone based on the mass flow rate, the density and dynamic viscosity at the pseudo-saturated liquid position;

[0052] The method for obtaining the friction coefficient of the heavy and light fluid mixing zone includes:

[0053] Obtain the dynamic viscosity at the pseudo-saturated vapor position;

[0054] Calculate the friction coefficient of the heavy and light fluid mixing zone based on the mass flow rate, the density and dynamic viscosity at the pseudo-saturated liquid position, and the density and dynamic viscosity at the pseudo-saturated vapor position;

[0055] The method for obtaining the friction coefficient of the light fluid zone includes:

[0056] Calculate the friction coefficient of the light fluid zone based on the mass flow rate, and the density and dynamic viscosity at the pseudo-saturated vapor position.

[0057] Further, the method for obtaining the enthalpy value, density and dynamic viscosity at the pseudo-saturated liquid position includes:

[0058] Calculate the temperature at the pseudo-saturated liquid position based on the pressure at the pseudo-saturated liquid position;

[0059] Query the enthalpy value, density and dynamic viscosity at the pseudo-saturated liquid position based on the pressure and temperature at the pseudo-saturated liquid position;

[0060] The method for obtaining the enthalpy value, density and dynamic viscosity at the pseudo-saturated vapor position includes:

[0061] Calculate the temperature at the pseudo-saturated vapor position based on the pressure at the pseudo-saturated vapor position;

[0062] Query the enthalpy value, density and dynamic viscosity at the pseudo-saturated vapor position based on the pressure and temperature at the pseudo-saturated vapor position.

[0063] Further, the method for obtaining the position coordinates of the pseudo-saturated vapor position includes:

[0064] The position coordinates of the pseudo-saturated vapor position are calculated based on the inlet enthalpy value, the mass flow rate, the inner diameter, and the enthalpy value of the pseudo-saturated vapor position.

[0065] A supercritical smooth tube critical heat flux prediction device, comprising:

[0066] A first acquisition module, configured to acquire the length, inner diameter, and inlet throttling degree of the smooth tube, as well as the inlet enthalpy value and mass flow rate of the working fluid in the smooth tube;

[0067] A second acquisition module, configured to acquire the pressure, enthalpy value, and density of the pseudo-saturated liquid position, as well as the pressure, enthalpy value, density, and position coordinates of the pseudo-saturated vapor position;

[0068] A third acquisition module, configured to acquire the friction coefficient of the heavy fluid region, the friction coefficient of the heavy and light fluid mixing region, and the friction coefficient of the light fluid region;

[0069] A prediction module, configured to, when the position coordinates are not less than the length, substitute a preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, and the pressure, enthalpy value, and density of the pseudo-saturated liquid position into a pre-established first heat load prediction function to obtain a first transfer function of the smooth tube pressure drop with respect to the inlet flow velocity; the first transfer function takes into account the density perturbation of the light fluid region; convert the first transfer function of the smooth tube pressure drop with respect to the inlet flow velocity into a first Nyquist curve, and predict the smooth tube critical heat flux according to the first Nyquist curve; when the position coordinates are less than the length, substitute a preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, the pressure, enthalpy value, and density of the pseudo-saturated liquid position, and the pressure, enthalpy value, and density of the pseudo-saturated vapor position into a pre-established second heat load prediction function to obtain a second transfer function of the smooth tube pressure drop with respect to the inlet flow velocity; convert the second transfer function of the smooth tube pressure drop with respect to the inlet flow velocity into a second Nyquist curve, and predict the smooth tube critical heat flux according to the second Nyquist curve.

[0070] A device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the supercritical smooth tube critical heat flux prediction method are implemented.

[0071] [[ID=2l]]A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the steps of the supercritical smooth tube critical heat flux prediction method are implemented.

[0072] Compared with the prior art, the present invention has at least the following beneficial effects:

[0073] The traditional method does not consider the different states of the outlet working fluid. When the working fluid is in the light-heavy mixed fluid region, if processed according to the traditional method, there are four segments in the transfer function, but actually there are only three segments. The treatment of the traditional method does not match the actual situation seriously. The present invention considers the different states of the outlet working fluid. When the outlet working fluid is in the light-heavy mixed fluid region, that is, when the position coordinate is not less than the length, the transfer function adopts the first transfer function. The first transfer function of the light tube pressure drop with respect to the inlet flow rate is converted into the first Nyquist curve, and the light tube critical heat load is predicted according to the first Nyquist curve. At the same time, when the position coordinate is not less than the length, the present invention uses the first transfer function considering the density perturbation in the light fluid region to predict the light tube critical heat load. That is to say, the present invention considers the density change in the fluid region, and the accuracy of the transfer function is increased through verification; when the outlet working fluid is in the light fluid region, that is, when the position coordinate is less than the length, the transfer function adopts the second transfer function. The second transfer function of the light tube pressure drop with respect to the inlet flow rate is converted into the second Nyquist curve, and the light tube critical heat load is predicted according to the second Nyquist curve. The accuracy of the transfer function is improved through verification.

[0074] To make the above objects, features and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, makes the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0075] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for use in the description of the specific embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0076] Figure 1 It is a schematic flow chart of a method for predicting the critical heat load of a supercritical light tube according to the present invention;

[0077] Figure 2 For the heat load q = 65 kW / m in the embodiment 2 less than the critical heat load q cr of the Nyquist diagram;

[0078] Figure 3 For the heat load q = 69.5 kW / m in the embodiment 2 equal to the critical heat load q cr of the Nyquist diagram;

[0079] Figure 4 For the heat load q = 70 kW / m in the embodiment 2 greater than the critical heat load q cr of the Nyquist diagram;

[0080] Figure 5 Graph for comparing experimental data of the embodiments with those of predecessors

[0081] Figure 6 Schematic diagram of steady-state energy for uniform axial heating of the light pipe

[0082] Figure 7 Comparison of the prediction results between the traditional scheme and the present invention considering the density in the light fluid region

[0083] Figure 8 Comparison of the prediction results between the traditional scheme and the present invention considering different working fluid states at the outlet

[0084] Figure 9 Schematic flow diagram of a method for predicting the critical heat load of a supercritical light pipe according to an embodiment of the present invention Specific implementation manner

[0085] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0086] As a specific implementation manner of the present invention, as Figure 1 shown, the present invention provides a method for predicting the critical heat load of a supercritical light pipe, specifically as follows:

[0087] Obtain the length, inner diameter, and inlet throttling degree of the light pipe, as well as the inlet enthalpy value and mass flow rate of the working fluid in the light pipe;

[0088] Obtain the pressure, enthalpy value, and density at the position of the pseudo-saturated liquid, as well as the pressure, enthalpy value, density, and position coordinates at the position of the pseudo-saturated vapor;[[ID=3�]]

[0089] Among them, the position of the pseudo-saturated liquid refers to the position where the heavy fluid region intersects with the heavy and light fluid mixing region, and the position of the pseudo-saturated vapor refers to the position where the heavy and light fluid mixing region intersects with the light fluid region; [[ID=3৮]]

[0090] Among them, the position coordinates of the pseudo-saturated vapor refer to the coordinates of the interface between the heavy and light mixed fluid region and the light fluid region. When the outlet working fluid is in the heavy and light mixed fluid region, the position coordinates do not exist. When the outlet working fluid is in the light fluid region, the position coordinates exist;

[0091] Obtain the friction coefficient in the heavy fluid region, the friction coefficient in the heavy and light fluid mixing region, and the friction coefficient in the light fluid region;

[0092] When the position coordinate is not less than the length, substitute the preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, and the pressure, enthalpy, and density at the pseudo-saturation liquid position into the pre-established first heat load prediction function to obtain the first transfer function of the light tube pressure drop with respect to the inlet velocity; the first transfer function takes into account the density perturbation in the light fluid region; specifically, the first heat load prediction function is:

[0093] δΔp(s) = [G0(s) + G1(s) + G2(s)]δu in (s)

[0094] G0(s) = k in ρ hm u in

[0095]

[0096] G2(s) = G 21 (s) + G 22 (s) + G 23 (s)

[0097]

[0098] G 22 (s) = X1(s)·Y1(s) + X2(s)·Y2(s)

[0099]

[0100]

[0101]

[0102]

[0103]

[0104] In the formula: δ - infinitesimal perturbation; in - inlet working fluid parameters; hm - working fluid parameters in the heavy fluid region; Δp - pressure drop of the entire heating tube section / Pa; G0(s) - transfer function of the inlet throttling region; G1(s) - transfer function of the heavy fluid region; G2(s) - transfer function of the heavy and light fluid mixing region; u in - inlet velocity of the working fluid / m·s -1 ; k in - inlet throttling coefficient; ρ - density of the working fluid / kg·m -3 ; Z - flow direction coordinate / m; s - complex variable; f1 - flow friction coefficient in the heavy fluid region; D e——Equivalent diameter of the pipe segment / m; g——Acceleration due to gravity / m·s -2 ; Ω1——Rate of change of the working fluid velocity along the axial direction in the mixed region of the light and heavy fluids / s -1 ; G——Mass flow rate / kg·m -2 ·s -1 ; L——Loop length / m; f2——Flow friction coefficient in the mixed region of the light and heavy fluids.

[0105] Convert the first transfer function of the light pipe pressure drop with respect to the inlet velocity into the first Nyquist curve, and predict the critical heat load of the light pipe according to the first Nyquist curve, specifically:

[0106] Judge the stability of the current working condition according to the first Nyquist curve, and continuously adjust the preset heat load until the first Nyquist curve of the preset heat load passes through the origin of coordinates, then the preset heat load is the critical heat load of the light pipe.

[0107] When the position coordinate is less than the length, substitute the preset heat load, the inner diameter, the mass flow rate, the friction coefficient in the heavy fluid region, the friction coefficient in the light fluid region, the pressure, enthalpy and density at the pseudo-saturated liquid position, and the pressure, enthalpy and density at the pseudo-saturated vapor position into the pre-established second heat load prediction function to obtain the second transfer function of the light pipe pressure drop with respect to the inlet velocity; specifically, the second heat load prediction function is:

[0108] δΔp(s) = [G0(s) + G1(s) + G'2(s) + G3(s)]δu in (s)

[0109] G0(s) = k in ρ hm u in

[0110]

[0111] G2'(s) = G 21 '(s) + G 22 '(s) + G 23 (s) + G 24 (s)

[0112]

[0113] G 22 '(s) = X1'(s)·Y1(s) + X2'(s)·Y2(s)

[0114]

[0115]

[0116]

[0117]

[0118] G3(s) = G 31 (s) + G 32 (s) + G 33 (s)

[0119]

[0120]

[0121] G 33 (s) = M(s)·a(s) + N(s)·b(s)

[0122]

[0123]

[0124]

[0125]

[0126] where: δ - small perturbation quantity; hm - working medium parameter in the heavy fluid region; ml - working medium parameter in the light fluid region; Δp - pressure drop of the entire heating pipe section / Pa; G0(s) - transfer function of the inlet throttling region; G1(s) - transfer function of the heavy fluid region; G2(s) - transfer function of the heavy and light fluid mixing region; G3(s) - transfer function of the light fluid region; u in - inlet velocity of the working medium / m·s -1 ; k in - inlet throttling coefficient; ρ - density of the working medium / kg·m -3 ; Z - flow direction coordinate / m; s - complex variable; f1 - flow friction coefficient in the heavy fluid region; D e - equivalent diameter of the pipe section / m; g - gravitational acceleration / m·s -2 ; Ω1 - axial change rate of the working medium flow velocity in the heavy and light fluid mixing region / s -1 ; G - mass flow rate / kg·m -2 ·s -1 ; L - loop length / m; f2 - flow friction coefficient in the heavy and light fluid mixing region; f3 - flow friction coefficient in the light fluid region; Ω2 - axial change rate of the working medium flow velocity in the light fluid region / s -1 .

[0127] Convert the second transfer function of the light tube pressure drop with respect to the inlet flow rate into a second Nyquist curve, and predict the light tube critical heat load according to the second Nyquist curve, specifically:

[0128] Judge the stability of the current working condition according to the second Nyquist curve, and continuously adjust the preset heat load until the second Nyquist curve of the preset heat load passes through the origin of coordinates, then the preset heat load is the light tube critical heat load.

[0129] On the basis of the above embodiments, as a more preferred embodiment, the method for obtaining the friction coefficient of the heavy fluid region is as follows:

[0130] Obtain the dynamic viscosity at the pseudo-saturated liquid position;

[0131] Calculate the friction coefficient of the heavy fluid region according to the mass flow rate, the density and dynamic viscosity at the pseudo-saturated liquid position.

[0132] Specifically, the calculation formula is as follows:

[0133] f1 = (1.82log 10 (Re) - 1.64) -2

[0134] wherein, the Reynolds number Re in the heavy fluid region is calculated according to the pseudo-saturated liquid point parameters.

[0135] On the basis of the above embodiments, as a more preferred embodiment, the method for obtaining the friction coefficient of the heavy and light fluid mixing region is as follows:

[0136] Obtain the dynamic viscosity at the pseudo-saturated vapor position;

[0137] Calculate the friction coefficient of the heavy and light fluid mixing region according to the mass flow rate, the density and dynamic viscosity at the pseudo-saturated liquid position, and the density and dynamic viscosity at the pseudo-saturated vapor position.

[0138] Specifically, the calculation formula is as follows:

[0139] f2 = (1.82log 10 (Re) - 1.64) -2

[0140] wherein, the Reynolds number Re in the heavy and light fluid mixing region is calculated by substituting the arithmetic mean of the pseudo-saturated liquid point and the pseudo-saturated vapor point into the above formula.

[0141] On the basis of the above embodiments, as a more preferred embodiment, the method for obtaining the friction coefficient of the light fluid region is as follows:

[0142] The friction coefficient of the light fluid region is calculated based on the mass flow rate, and the density and dynamic viscosity at the position of the pseudo-saturated vapor.

[0143] Specifically, the calculation formula is as follows:

[0144] f3 = (1.82 log 10 (Re) - 1.64) -2

[0145] Among them, the Reynolds number Re of the light fluid region is calculated by substituting the arithmetic mean of the pseudo-saturated liquid point and the pseudo-saturated vapor point into the above formula.

[0146] Based on the above embodiment, as a more preferred embodiment, the method for obtaining the enthalpy value, density, and dynamic viscosity at the position of the pseudo-saturated liquid is as follows:

[0147] The temperature at the position of the pseudo-saturated liquid is calculated based on the pressure at the position of the pseudo-saturated liquid;

[0148] The enthalpy value, density, and dynamic viscosity at the position of the pseudo-saturated liquid are obtained by querying according to the pressure and temperature at the position of the pseudo-saturated liquid.

[0149] Specifically, the enthalpy value, density, and dynamic viscosity at the position of the pseudo-saturated liquid are obtained by querying from Refprop (NIST physical property query software).

[0150] Based on the above embodiment, as a more preferred embodiment, the method for obtaining the enthalpy value, density, and dynamic viscosity at the position of the pseudo-saturated vapor is as follows:

[0151] The temperature at the position of the pseudo-saturated vapor is calculated based on the pressure at the position of the pseudo-saturated vapor;

[0152] The enthalpy value, density, and dynamic viscosity at the position of the pseudo-saturated vapor are obtained by querying according to the pressure and temperature at the position of the pseudo-saturated vapor. [[ID=�4]]

[0153] Specifically, the enthalpy value, density, and dynamic viscosity at the position of the pseudo-saturated vapor are obtained by querying from Refprop (NIST physical property query software).

[0154] Based on the above embodiment, as a more preferred embodiment, the method for obtaining the position coordinates of the pseudo-saturated vapor position is as follows:

[0155] The position coordinates of the pseudo-saturated vapor position are calculated based on the inlet enthalpy value, the mass flow rate, the inner diameter, and the enthalpy value at the position of the pseudo-saturated vapor.

[0156] Specifically, the calculation formula is as follows:

[0157]

[0158] In the formula: Z hm —— Position coordinate of the pseudo-saturated vapor position / m; Z in —— Position coordinate at the inlet of the pipe section / m; G—— Mass flux / kg·m -2 ·s -1 ; A c —— Flow area of the plain tube / m 2 ; h ml —— Enthalpy value of the pseudo-saturated vapor / kJ·kg -1 ; h in —— Inlet enthalpy value / kJ·kg -1 ; q—— Heat load / kW·m -2 ; P h —— Wetted perimeter of the plain tube / m.

[0159] A specific embodiment is provided below to better explain a method for predicting the critical heat load of a supercritical plain tube of the present invention.

[0160] Figure 2 、 Figure 3 、 Figure 4 For the condition of a pressure of 23 MPa, an inlet enthalpy value of 1200 kJ / kg, a mass flow rate of 180 kg / (m 2 s), an inlet throttling coefficient of 0, and an outlet throttling coefficient of 0.

[0161] According to the pressure, calculate the pseudo-saturated liquid temperature of 344.9121 °C and the pseudo-saturated vapor temperature of 438.9937 °C under supercritical pressure;

[0162] According to the pressure and temperature of the pseudo-saturated liquid point, query the working fluid parameters of the pseudo-saturated liquid point: density 633.57 kg·m -3 、enthalpy value 1595.5 kJ·kg -1 、dynamic viscosity 73.761 μPas;

[0163] According to the pressure and temperature of the pseudo-saturated vapor point, query the working fluid parameters of the pseudo-saturated liquid point: density 101.01 kg·m -3 、enthalpy value 2944.1 kJ·kg -1 、dynamic viscosity 28.232 μPas;

[0164] Input the pipe section parameters of inner diameter 21 mm, length 20000 mm, the condition parameters of pressure 23 MPa, inlet enthalpy value 1200 kJ / kg, mass flux 180 kg / (m 2 s), inlet throttling coefficient of 0 and the data obtained from the above calculations and queries into the transfer function.

[0165] The preset heat load is 65 kW·m -2, the Nyquist curve is calculated, as Figure 2 shown. It is found that the curve does not enclose the origin, and at this time the system is stable and has not reached the critical state; the preset heat load is increased to 69.5 kW·m -2 , the Nyquist curve is calculated, as Figure 3 shown. It is found that the curve just passes through the coordinate origin, so the preset heat load at this time is the boundary heat load; the preset heat load is continuously increased to 70 kW·m -2 , the Nyquist curve is calculated, as Figure 4 shown. It is found that the curve encloses the coordinate origin, and at this time the system is unstable. Figure 3 、 Figure 4 consists of two parts, and the right part is an enlarged view of the left part at the origin.

[0166] According to the experimental data in Table 1 below, as shown in Table 1 below. A smooth straight pipe with a pipe type of length L = 12.6 m and inner diameter D in = 0.01 m is verified. Without considering the inlet throttling coefficient, according to the above calculation process, the predicted boundary heat load is obtained. Figure 5 Comparing the experimental data with the predicted results, an error within 20% is considered to meet the requirements.

[0167] Table 1 Experimental conditions and results

[0168]

[0169] The present invention considers the density change in the fluid region, and the accuracy of the transfer function is increased after verification, as Figure 7 shown. The present invention considers the different states of the outlet working medium. When the outlet working medium is in the heavy-light mixed fluid region, the transfer function adopts the first prediction function. When the outlet working medium is in the light fluid region, the transfer function adopts the second prediction function. The accuracy of the transfer function is improved after verification, as Figure 8 shown. Figure 7 、 Figure 8 The N shown in exp and the threshold power are both parameters related to the boundary heat load, where:

[0170]

[0171] R——Ideal gas constant / kJ·mol -1 ·K -1 ; c p ——Specific heat capacity at constant pressure of ideal gas, kJ·kg -1 ·K -1 ; p——System pressure / MPa; q——Heat load / kW / m 2 ; P h ——Wetted perimeter / m; A c ——Flow area of smooth pipe / m2 ; L—the length of the light pipe / m; u in —the inlet flow velocity / m / s The threshold power = the heat load × the wetted perimeter × the length of the light pipe.

[0172] The following takes the heavy fluid region as an example to elaborate on the derivation process of the first heat load prediction function:

[0173] After establishing the model, it is necessary to simplify different sections:

[0174] (1) It is considered that the heavy fluid region is an incompressible fluid;

[0175] (2) The pressure loss in the pipe is very small compared to the inlet and outlet pressures of the pipe, and it is considered that the inlet and outlet pressure differences are constant;

[0176] (3) The homogeneous flow model is selected for the light and heavy fluid mixing region.

[0177] According to assumption 1, the density in this region is the same, which is the density of the pseudo-saturated liquid point.

[0178] Mass conservation equation

[0179]

[0180] Energy conservation equation

[0181]

[0182] Momentum conservation equation

[0183]

[0184] After linearized micro-perturbation, the steady-state terms are eliminated to obtain the control equation for the heavy fluid region.

[0185] The energy equation is micro-perturbed to obtain

[0186]

[0187] The above equation is rearranged to eliminate the steady-state terms to obtain

[0188]

[0189] According to the steady-state energy conservation equation of the axially uniformly heated pipe, as Figure 6 shown

[0190] ρ hm u in A c dh = qP h dz

[0191] Obtain

[0192]

[0193] Substituting into the energy conservation equation after eliminating the steady-state term gives

[0194]

[0195] Performing Laplace transform

[0196]

[0197] This equation is a first-order nonlinear differential equation. According to the solution formula

[0198] y = ce -∫p(x)dx + e -∫p(x)dx ·∫f(x)e ∫p(x)dx dx

[0199] Solving the above differential equation according to this formula gives

[0200]

[0201] Searching the literature gives

[0202]

[0203] Integrating the momentum conservation equation along the z direction gives

[0204]

[0205] Performing a small perturbation on this equation

[0206]

[0207] Neglecting the higher-order terms of the perturbed quantity and eliminating the steady-state term

[0208]

[0209] is the steady-state term, which is regarded as 0. Performing Laplace transform on this equation

[0210]

[0211] Substituting δZ ht into the above equation

[0212]

[0213] Without considering the perturbation of δh in the above equation can be reduced to

[0214]

[0215] The present invention provides a supercritical light tube critical heat flux prediction device, comprising:

[0216] A first acquisition module, configured to acquire the length, inner diameter, and inlet throttling degree of the light pipe, as well as the inlet enthalpy value and mass flow rate of the working fluid in the light pipe.

[0217] A second acquisition module, configured to acquire the pressure, enthalpy value, and density at the pseudo-saturated liquid position, as well as the pressure, enthalpy value, density, and position coordinates at the pseudo-saturated vapor position.

[0218] A third acquisition module, configured to acquire the friction coefficient in the heavy fluid region, the friction coefficient in the heavy-light fluid mixing region, and the friction coefficient in the light fluid region.

[0219] A prediction module, configured to, when the position coordinates are not less than the length, substitute a preset heat load, the inner diameter, the mass flow rate, the friction coefficient in the heavy fluid region, the friction coefficient in the light fluid region, and the pressure, enthalpy value, and density at the pseudo-saturated liquid position into a pre-established first heat load prediction function to obtain a first transfer function of the light pipe pressure drop with respect to the inlet flow velocity; the first transfer function takes into account the density perturbation in the light fluid region; convert the first transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a first Nyquist curve, and predict the light pipe critical heat load according to the first Nyquist curve; when the position coordinates are less than the length, substitute a preset heat load, the inner diameter, the mass flow rate, the friction coefficient in the heavy fluid region, the friction coefficient in the light fluid region, the pressure, enthalpy value, and density at the pseudo-saturated liquid position, and the pressure, enthalpy value, and density at the pseudo-saturated vapor position into a pre-established second heat load prediction function to obtain a second transfer function of the light pipe pressure drop with respect to the inlet flow velocity; convert the second transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a second Nyquist curve, and predict the light pipe critical heat load according to the second Nyquist curve.

[0220] In one embodiment of the present invention, a computer device is provided. The computer device includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is suitable for implementing one or more instructions. Specifically, it is suitable for loading and executing one or more instructions to implement the corresponding method flow or corresponding function. The processor described in the embodiment of the present invention can be used to implement the operation of a supercritical light tube boundary heat load prediction method.

[0221] In one embodiment of the present invention, when a supercritical light tube boundary heat load prediction method is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, to implement all or part of the processes in the above-described embodiment methods of the present invention, it can also be completed by instructing relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by a processor, the steps of the above-described various method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in the form of source code, object code, executable file, or some intermediate form, etc. The computer-readable storage medium includes permanent and non-permanent, removable and non-removable media, and information storage can be achieved by any method or technology. The information can be computer-readable instructions, data structures, program modules, or other data.

[0222] The computer storage medium can be any available medium or data storage device that can be accessed by a computer, including but not limited to magnetic memories (such as floppy disks, hard disks, magnetic tapes, magneto-optical discs (MO), etc.), optical memories (such as CDs, DVDs, BDs, HVDs, etc.), and semiconductor memories (such as ROMs, EPROMs, EEPROMs, non-volatile memories (NAND FLASH), solid state drives (SSDs)), etc.

[0223] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an all-hardware embodiment, an all-software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0224] The present application is described with reference to the flowcharts and / or block diagrams of the methods, apparatuses (systems), and computer program products of the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks.

[0225] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the functions specified in Figure 1 one or more of the flows Figure 1 or blocks.

[0226] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Therefore, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the flows Figure 1 or blocks.

[0227] Finally, it should be noted that the above-described embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that any technician familiar with the technical field of the present invention can still modify the technical solutions recorded in the foregoing embodiments or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described.

Claims

1. A method for predicting the critical heat flux of a supercritical light tube, characterized in that, Including: Obtaining the length, inner diameter and inlet throttling degree of the light pipe, as well as the inlet enthalpy value and mass flow rate of the working medium in the light pipe; Obtaining the pressure, enthalpy value and density of the pseudo-saturated liquid position, as well as the pressure, enthalpy value, density and position coordinates of the pseudo-saturated vapor position; Obtaining the friction coefficient of the heavy fluid region, the friction coefficient of the heavy-light fluid mixing region and the friction coefficient of the light fluid region; When the position coordinate is not less than the length, substituting the preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, and the pressure, enthalpy value and density of the pseudo-saturated liquid position into a pre-established first heat load prediction function to obtain a first transfer function of the light pipe pressure drop with respect to the inlet flow velocity; the first transfer function takes into account the density perturbation of the light fluid region; Converting the first transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a first Nyquist curve, and predicting the light pipe critical heat load according to the first Nyquist curve; When the position coordinate is less than the length, substituting the preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, the pressure, enthalpy value and density of the pseudo-saturated liquid position, and the pressure, enthalpy value and density of the pseudo-saturated vapor position into a pre-established second heat load prediction function to obtain a second transfer function of the light pipe pressure drop with respect to the inlet flow velocity; Converting the second transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a second Nyquist curve, and predicting the light pipe critical heat load according to the second Nyquist curve.

2. The supercritical light tube boundary heat load prediction method according to claim 1, wherein The first heat load prediction function is: δΔp(s) = [G0(s) + G1(s) + G2(s)]δu in (s) G0(s) = k in ρ hm u in G2(s) = G 21 (s) + G 22 (s) + G 23 (s) G 22 (s) = X1(s)·Y1(s) + X2(s)·Y2(s) where: δ is the small perturbation quantity; in is the inlet working fluid parameter; hm is the working fluid parameter in the heavy fluid region; Δp is the pressure drop of the entire heating pipe section; G0(s) is the transfer function of the inlet throttling region; G1(s) is the transfer function of the heavy fluid region; G2(s) is the transfer function of the light and heavy fluid mixing region; u in is the inlet velocity of the working fluid; k in is the inlet throttling coefficient; ρ is the density of the working fluid; Z is the flow direction coordinate; s is the complex variable; f1 is the flow friction coefficient in the heavy fluid region; D e is the equivalent diameter of the pipe section; g is the acceleration due to gravity; Ω1 is the axial change rate of the working fluid velocity in the light and heavy fluid mixing region; G is the mass flow rate; L is the loop length; f2 is the flow friction coefficient in the light and heavy fluid mixing region.

3. The supercritical light tube boundary heat load prediction method according to claim 1, characterized in that The second heat load prediction function is: δΔp(s) = [G0(s) + G1(s) + G'2(s) + G3(s)]δu in (s) G0(s) = k in ρ hm u in G2'(s) = G 21 '(s) + G 22 '(s) + G 23 (s) + G 24 (s) G 22 '(s) = X1'(s)·Y1(s) + X2'(s)·Y2(s) G3(s) = G 31 (s) + G 32 (s) + G 33 (s) G 33 (s) = M(s)·a(s) + N(s)·b(s) where: δ is the small perturbation quantity; in is the inlet working fluid parameter; hm is the working fluid parameter in the heavy fluid region; ml is the working fluid parameter in the light fluid region; Δp is the pressure drop across the entire heated tube section; G0(s) is the transfer function of the inlet throttling region; G1(s) is the transfer function of the heavy fluid region; G2(s) is the transfer function of the heavy and light fluid mixing region; G3(s) is the transfer function of the light fluid region; u in is the inlet velocity of the working fluid; k in is the inlet throttling coefficient; ρ is the density of the working fluid; Z is the flow direction coordinate; s is the complex variable; f1 is the flow friction coefficient in the heavy fluid region; D e is the equivalent diameter of the tube section; g is the acceleration due to gravity; Ω1 is the axial change rate of the working fluid velocity in the heavy and light fluid mixing region; G is the mass flow rate; L is the loop length; f2 is the flow friction coefficient in the heavy and light fluid mixing region; f3 is the flow friction coefficient in the light fluid region; Ω2 is the axial change rate of the working fluid velocity in the light fluid region.

4. A supercritical light tube critical heat flux prediction method according to claim 1, characterized in that The method for obtaining the friction coefficient of the heavy fluid region includes: Obtaining the dynamic viscosity of the pseudo-saturated liquid position; Calculating the friction coefficient of the heavy fluid region according to the mass flow rate, the density and dynamic viscosity of the pseudo-saturated liquid position; The method for obtaining the friction coefficient of the heavy-light fluid mixing region includes: Obtaining the dynamic viscosity of the pseudo-saturated vapor position; Calculating the friction coefficient of the heavy-light fluid mixing region according to the mass flow rate, the density and dynamic viscosity of the pseudo-saturated liquid position, and the density and dynamic viscosity of the pseudo-saturated vapor position; The method for obtaining the friction coefficient of the light fluid region includes: Calculating the friction coefficient of the light fluid region according to the mass flow rate, and the density and dynamic viscosity of the pseudo-saturated vapor position.

5. A supercritical light tube boundary heat load prediction method according to claim 4, characterized in that The method for obtaining the enthalpy value, density and dynamic viscosity of the pseudo-saturated liquid position includes: Calculating the temperature of the pseudo-saturated liquid position according to the pressure of the pseudo-saturated liquid position; Querying the enthalpy value, density and dynamic viscosity of the pseudo-saturated liquid position according to the pressure and temperature of the pseudo-saturated liquid position; The method for obtaining the enthalpy value, density and dynamic viscosity of the pseudo-saturated vapor position includes: Calculating the temperature of the pseudo-saturated vapor position according to the pressure of the pseudo-saturated vapor position; Querying the enthalpy value, density and dynamic viscosity of the pseudo-saturated vapor position according to the pressure and temperature of the pseudo-saturated vapor position.

6. A method for predicting the critical heat flux of a supercritical light tube according to claim 1, characterized in that The method for obtaining the position coordinates of the pseudo-saturated vapor position includes: The position coordinates of the pseudo-saturated vapor position are calculated based on the inlet enthalpy value, the mass flow rate, the inner diameter, and the enthalpy value of the pseudo-saturated vapor position.

7. A supercritical light tube critical heat flux prediction device, characterized in that Including: A first acquisition module for acquiring the length, inner diameter, and inlet throttling degree of the light pipe, as well as the inlet enthalpy value and mass flow rate of the working fluid in the light pipe; A second acquisition module for acquiring the pressure, enthalpy value, and density of the pseudo-saturated liquid position, as well as the pressure, enthalpy value, density, and position coordinates of the pseudo-saturated vapor position; A third acquisition module for acquiring the friction coefficient of the heavy fluid region, the friction coefficient of the heavy-light fluid mixing region, and the friction coefficient of the light fluid region; A prediction module for, when the position coordinates are not less than the length, substituting a preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, and the pressure, enthalpy value, and density of the pseudo-saturated liquid position into a pre-established first heat load prediction function to obtain a first transfer function of the light pipe pressure drop with respect to the inlet flow velocity; the first transfer function takes into account the density perturbation of the light fluid region; converting the first transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a first Nyquist curve, and predicting the critical heat load of the light pipe according to the first Nyquist curve; when the position coordinates are less than the length, substituting a preset heat load, the inner diameter, the mass flow rate, the friction coefficient of the heavy fluid region, the friction coefficient of the light fluid region, the pressure, enthalpy value, and density of the pseudo-saturated liquid position, and the pressure, enthalpy value, and density of the pseudo-saturated vapor position into a pre-established second heat load prediction function to obtain a second transfer function of the light pipe pressure drop with respect to the inlet flow velocity; converting the second transfer function of the light pipe pressure drop with respect to the inlet flow velocity into a second Nyquist curve, and predicting the critical heat load of the light pipe according to the second Nyquist curve.

8. An apparatus, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein, When the processor executes the computer program, the steps of a method for predicting the critical heat load of a supercritical light pipe according to any one of claims 1 to 6 are implemented.

9. A computer-readable storage medium storing a computer program, characterized in that, When the computer program is executed by the processor, the steps of a method for predicting the critical heat load of a supercritical light pipe according to any one of claims 1 to 6 are implemented.

Images