CN-120950792-B - Calculation method and calculation device for surface film boiling starting point with dirt

CN120950792BCN 120950792 BCN120950792 BCN 120950792BCN-120950792-B

Abstract

A calculation method and a calculation device for a film boiling starting point of a surface with dirt belong to the field of nuclear power. The calculation method of the film boiling starting point of the surface with dirt comprises the following steps of establishing a heat exchange model of the surface of the fuel rod with dirt according to a fuel rod cladding model with dirt and thermal parameters, calculating the heat conductivity coefficient and the permeability of a dirt area, calculating the thickness of a film at the beginning of film boiling, and calculating the heat flux density corresponding to the minimum value of the thickness of the film according to pressure balance and an energy conservation equation to obtain the initial heat flux density of film boiling. The method can accurately calculate the initial heat flux density of film boiling under the influence of the dirt, and improve the accuracy of systematically analyzing the influence of the dirt on the thermal hydraulic performance of the reactor.

Inventors

WEI CEN
Cong tenglong
WANG ZHE
ZHANG BOTAO
ZHANG SHUNXIANG
WANG XIAOWEN
XU ZHIHONG
GU HANYANG
ZHANG DI

Assignees

上海核工程研究设计院股份有限公司

Dates

Publication Date: 20260508
Application Date: 20250731

Claims (3)

1. A method for calculating a boiling start point of a surface film with dirt, which is characterized by comprising the following steps: Providing a fouled fuel rod cladding model and a thermal parameter, establishing a fouled fuel rod cladding surface heat exchange model according to the fouled fuel rod cladding model and the thermal parameter, and calculating the heat conductivity coefficient and the permeability of a fouled area based on a parting theory and the fouled fuel rod cladding surface heat exchange model, wherein the fouled fuel rod cladding model comprises a fouled thickness, a fouled porosity, a maximum pore diameter, a minimum pore diameter and a fouled solid phase heat conductivity coefficient, the thermal parameter comprises a main flow fluid temperature, a main flow fluid speed, a working pressure and a hydraulic diameter, and the calculation method of the heat conductivity coefficient k fractal of the fouled area comprises the following steps: ; The method for calculating the permeability k of the fouling area is as follows: ; Wherein k series is the dirt series equivalent thermal conductivity, k p is the dirt fractal parallel equivalent thermal conductivity, Φ is the dirt porosity, D f is the fractal dimension of the pore volume, D T is the fractal dimension of the dirt curved capillary path, and λ max is the maximum pore diameter; And b) establishing a steam chimney model, and calculating the thickness of a gas film at the beginning of membranous boiling according to the diameter of the steam chimney, wherein the steam chimney model comprises the diameter of the steam chimney and the inclination angle of the steam chimney, and the calculating method of the thickness delta v of the gas film is as follows: δ v =d ch· sinθ, wherein d ch is the diameter of the steam chimney, and θ is the inclination angle of the steam chimney; And c), calculating the heat flux density corresponding to the minimum value of the air film thickness according to the pressure balance and the energy conservation equation, and using the heat flux density as the film boiling initial heat flux density, wherein the calculating method of the film boiling initial heat flux density q comprises the following steps: ; wherein q b is boiling heat exchange heat flow density, ; Sigma (T) is the surface tension of the liquid at the temperature T, h lv is the latent heat of vaporization of water, For the fouling contact angle, λ max is the maximum pore diameter, v l is the liquid kinematic viscosity, v v is the vapor kinematic viscosity, k is the fouling permeability, L is the fouling thickness, δ v is the fouling inner vapor film thickness, f ch is the fouling vapor chimney area duty cycle, d is the vapor along film escape length, θ is the vapor chimney inclination angle, T sat is the liquid saturation temperature, T b is the mainstream fluid temperature, h 0 is the fouling surface heat transfer coefficient, u f is the hydrodynamic viscosity, α m is the fouling thermal diffusion coefficient, α m =k fractal /ρc pf , ρ is the fouling density, and c pf is the fouling specific heat capacity.
2. The method for calculating the boiling start point of the surface film with the dirt according to claim 1, wherein the dirt thickness L, the dirt porosity phi, the maximum pore diameter lambda max , the steam chimney diameter d ch , the steam chimney inclination angle theta, the dirt series equivalent heat conduction coefficient k series , the dirt fractal parallel equivalent heat conduction coefficient k p and the main flow fluid temperature T b are measured through experiments.
3. A computing device comprising a memory and a processor, wherein the memory stores a fouling surface film boiling start point calculation program which, when executed by the processor, is capable of implementing the fouling surface film boiling start point calculation method according to any one of claims 1 or 2.

Description

Calculation method and calculation device for surface film boiling starting point with dirt Technical Field The invention belongs to the field of nuclear power, and particularly relates to a calculation method and a calculation device for a film boiling starting point of a surface with dirt. Background In the long-term operation process of the pressurized water reactor nuclear power plant, dirt is gradually deposited on the surface of the fuel cladding, the heat exchange characteristic of the surface of the fuel rod cladding is changed, and the boiling heat exchange behavior is further affected. At present, research on a membranous boiling process of a surface with dirt is insufficient, and when the influence of the dirt on the thermal hydraulic characteristics of a reactor is analyzed based on a heat exchange model, different boiling conditions cannot be accurately predicted. Therefore, the method for calculating the boiling start point of the surface film with dirt has positive significance for improving the analysis of the influence of dirt on the thermal hydraulic characteristics of a reactor. Disclosure of Invention The invention aims to provide a calculation method for the boiling starting point of a surface film state with dirt, which improves the accuracy of thermal hydraulic characteristic analysis of the surface with dirt. The invention also provides a computing device. According to an embodiment of one aspect of the present invention, there is provided a method for calculating a boiling start point of a fouled surface film state, the method comprising the steps of: providing a dirty fuel rod cladding model and a thermal parameter, establishing a dirty fuel rod cladding surface heat exchange model according to the dirty fuel rod cladding model and the thermal parameter, and calculating the heat conductivity coefficient and the permeability of a dirty area based on a parting theory and the dirty fuel rod cladding surface heat exchange model; step b), establishing a steam chimney model, and calculating according to the diameter of the steam chimney to obtain the thickness of the air film at the beginning of film boiling; And c), calculating the heat flux density corresponding to the minimum value of the air film thickness according to the pressure balance and the energy conservation equation, and taking the heat flux density as the initial heat flux density of film boiling. Further, in some embodiments, in step a), the fouled fuel rod clad pattern comprises a fouled thickness, a fouled porosity, a maximum pore diameter, a minimum pore diameter, and a fouled solid phase thermal conductivity, and the thermal parameters comprise a main flow fluid temperature, a main flow fluid velocity, a working pressure, and a hydraulic diameter. Further, in some embodiments, in the step a), the method for calculating the thermal conductivity k fractal of the fouling area is: ; The method for calculating the permeability k of the fouling area is as follows: ; Where k series is the scale series equivalent thermal conductivity, k p is the scale fractal parallel equivalent thermal conductivity, Φ is the scale porosity, D f is the fractal dimension of the pore volume, D T is the fractal dimension of the scale tortuous capillary path, and λ max is the maximum pore diameter. Further, in some embodiments, in the step b), the steam chimney model includes a steam chimney diameter and a steam chimney inclination. Further, in some embodiments, in the step b), the method for calculating the air film thickness δ v is: δv=dch·sinθ, wherein d ch is the diameter of the steam chimney, and θ is the inclination angle of the steam chimney. Further, in some embodiments, the method for calculating the film boiling start heat flux density q is as follows: ; wherein q b is boiling heat exchange heat flow density, ; Sigma (T) is the surface tension of the liquid at the temperature T, h lv is the latent heat of vaporization of water,For the fouling contact angle, λ max is the maximum pore diameter, v l is the liquid kinematic viscosity, v v is the vapor kinematic viscosity, k is the fouling permeability, L is the fouling thickness, δ v is the fouling inner vapor film thickness, f ch is the fouling vapor chimney area duty cycle, d is the vapor along film escape length, θ is the vapor chimney inclination angle, T sat is the liquid saturation temperature, T b is the mainstream fluid temperature, h 0 is the fouling surface heat transfer coefficient, u f is the hydrodynamic viscosity, α m is the fouling thermal diffusion coefficient, α m=kfractal/ρcpf, ρ is the fouling density, and c pf is the fouling specific heat capacity. Further, in some embodiments, the scale thickness L, the scale porosity Φ, the maximum pore diameter λ max, the steam stack diameter d ch, the steam stack inclination θ, the scale series equivalent thermal conductivity k series, the scale fractal parallel equivalent thermal conductivity k p, and the mainstream fluid temperatur