A numerical simulation method applicable to the evaporation and condensation effects of the fog plume in a cooling tower

Abstract

The present invention discloses a numerical simulation method applicable to the evaporation and condensation effects of the fog plume of a cooling tower, comprising the following steps: establishing a model according to the design parameters of the cooling tower; performing mesh division according to the model; based on the divided mesh, combining two methods of continuous phase and discrete phase, the continuous phase simulates the migration and diffusion of the fog plume of the cooling tower, and the discrete phase simulates the deposition of the fog plume of the cooling tower under the action of evaporation and condensation, and then coupling to simulate the deposition, migration and diffusion of the fog plume of the cooling tower. The present invention can realize the simulation of the evaporation and condensation effects of the fog plume of the cooling tower.

Description

Technical Field

[0001] The present invention belongs to the technical field of establishing a simulation method for the evaporation and condensation effects of the fog plume of a cooling tower in the atmospheric boundary layer, and particularly relates to a numerical simulation method applicable to the evaporation and condensation effects of the fog plume of a cooling tower. Background Art

[0002] During the normal operation of a large natural draft cooling tower, a large amount of steam is generated during the water-vapor exchange process. After the steam is discharged, it mixes with the surrounding air, and a part of it may condense to form a white plume of fog, which is called the "fog plume". The cooling tower will cause effects such as shading and salt deposition in the local area, affecting the deposition and diffusion of the fog plume. The calculation of the deposition of cooling tower drift droplets is more difficult than the calculation of particle sedimentation. Because when the relative humidity in the environment is less than 100%, the drift droplets will shrink due to evaporation, and the drift droplets may completely evaporate before reaching the ground, and the remaining very small particles will not have enough sedimentation velocity to fall through the turbulence. Neither particle gravitational deposition nor ballistic trajectory can calculate the deposition of cooling tower drift droplets well. Currently, in the common DPM model when calculating such problems, it is found that the deposition amount of the cooling tower fog plume is quite different from the on-site observation value, and it cannot well estimate the impact of the evaporation and condensation of the cooling tower fog plume on the local environment. Therefore, it is desired to establish a numerical simulation method that can realize the evaporation and condensation effects of the cooling tower fog plume. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention proposes a numerical simulation method applicable to the evaporation and condensation effects of the fog plume of a cooling tower, which can realize the evaporation and condensation effects of the fog plume of the cooling tower.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A numerical simulation method applicable to the evaporation and condensation effects of the fog plume of a cooling tower, comprising the following steps:

[0006] Establish a model according to the design parameters of the cooling tower;

[0007] Perform grid division according to the model;

[0008] Based on the divided grid, a combination of continuous phase and discrete phase is adopted. The continuous phase simulates the migration and diffusion of the cooling tower fog plume, and the discrete phase simulates the deposition of the cooling tower fog plume under the action of evaporation and condensation;

[0009] Couple and simulate the deposition, migration and diffusion of the cooling tower fog plume to realize the simulation of the evaporation and condensation effects of the cooling tower fog plume.

[0010] Preferably, the model is: according to the area to be studied, a km×b km, the simulation calculation domain is 1.5a km×1.5b km, where a < 10 km and b < 10 km.

[0011] Preferably, the divided grid adopts a hexahedral grid structure, with the maximum grid size in the area being 20 m and the minimum grid size being 1 m.

[0012] Preferably, the method for simulating the migration and diffusion of the cooling tower plume using the continuous phase includes:

[0013] where the source term S m is the mass added to the continuous phase from the discrete phase due to the evaporation of the drift droplets, ρ is the air density, t is the time, x i is the distance in the i direction, u i is the velocity in the i direction;

[0014] where p is the static pressure, τ ij is the stress tensor, ρg i is the gravitational body force in the i direction, F i is the external body force in the i direction, x j is the distance in the j direction, u j is the velocity in the j direction;

[0015] where k eff is the effective thermal conductivity, J l is the diffusion flux of component l, S h is the radiative heat transfer, E is the energy, T is the temperature, h is the enthalpy, h l is the enthalpy of component l;

[0016] where m l is the mass fraction of the l-th component; Γ l is the exchange coefficient of the l-th component; R l is the production rate of the l-th component;

[0017] where ρ is the density of the moist air, kg / m 3 , is the velocity vector, φ is the generalized variable, S φ is the source term of the air phase, S pφ is the additional source term due to the interaction between the air and the drift droplets, is the convection term, Γ φ gradφ - diffusion term, where Γ φ is the generalized diffusion coefficient.

[0018] Preferably, the method for simulating the deposition of the cooling tower plume under the action of evaporation and condensation using the discrete phase includes:

[0019] where r p is the drift droplet trajectory, and v p is the instantaneous velocity of the drift droplet;

[0020] where M p is the mass of the drift droplet, in kg, c p is the specific heat of the drift droplet, in J / kg·K, A p is the surface area of the drift droplet, in m 2 , α is the convective heat transfer coefficient, in W / m 2 .K, T adb is the dry-bulb temperature of the air, in K, and T p is the temperature of the drift droplet;

[0021] where k c is the mass transfer coefficient, R is the universal gas constant, and P n (T p ) is the saturation water vapor pressure at the temperature Tp, and C is a constant;

[0022] where is the evaporation rate, in kg / s, and γ 0 is a constant.

[0023] Preferably, the method for coupling and simulating the deposition, migration, and diffusion of the fog plume of a cooling tower includes: calculating P n (T p ), calculating the density of the drift droplet, and calculating the latent heat of the drift droplet.

[0024] Preferably, the calculation method of P n (T p ) includes:

[0025]

[0026] Preferably, the calculation method of the density of the drift droplet includes:

[0027] ρ p = 1063.9999 - 691.8390×T p 3 - 446.8621×T p 6

[0028] + 4766.6072×T p 9 - 2111.3447×T p 12 .

[0029] Preferably, the calculation method of the latent heat of the drift droplet includes:

[0030] HV = 1000×exp[3.5 + 3.45×log 10 (647 - T p ) - 1.053×(log 10 (647 - T p )) 2

[0031] + 0.158345×(log 10 (647 - T p )) 3 - 0.0088×(log 10 (647 - T p )) 4 - 1。

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The present invention combines two methods, i.e., continuous phase (air) and discrete phase (fog plume), to simulate the deposition and diffusion of the fog plume of a cooling tower, and simultaneously considers the evaporation and condensation during the migration and diffusion of water vapor. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0035] Figure 1 Schematic flow chart of a numerical simulation method applicable to the evaporation and condensation effects of the fog plume of a cooling tower in an embodiment of the present invention;

[0036] Figure 2 Schematic diagram of the computational domain and its grid in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of environmental turbulence intensity, wind speed, and environmental humidity profile in an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of the particle size spectrum distribution of the water vapor discharged from the cooling tower in an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of the trajectory curve of the fog plume drift droplets of the cooling tower in an embodiment of the present invention;

[0040] Figure 6 Schematic diagram of the trajectory curve of the fog plume drift droplets of the cooling tower in an embodiment of the present invention, wherein (a) is a schematic diagram of the fog plume of the cooling tower calculated by the DPM model, and (b) is a schematic diagram of the fog plume of the cooling tower calculated by the method of the present invention;

[0041] Figure 7 Schematic diagram for comparing the deposition amount of the fog plume in the cooling tower in the embodiment of the present invention. Specific implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. 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.

[0043] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners.

[0044] Embodiment 1

[0045] As Figure 1 shown, a numerical simulation method applicable to the evaporation and condensation effects of the cooling tower fog plume includes the following steps:

[0046] Establish a model according to the cooling tower design parameters;

[0047] Perform mesh division according to the model;

[0048] Based on the divided mesh, combine the continuous phase and the discrete phase. The continuous phase simulates the migration and diffusion of the cooling tower fog plume, and the discrete phase simulates the deposition of the cooling tower fog plume under the action of evaporation and condensation;

[0049] Couple and simulate the deposition and migration and diffusion of the cooling tower fog plume to realize the simulation of the evaporation and condensation effects of the cooling tower fog plume.

[0050] In this embodiment, first, a model is established according to the cooling tower design parameters. According to the proposed research area of a km × b km (a < 10 km, b < 10 km), the simulation calculation domain is 1.5a km × 1.5b km.

[0051] In this embodiment, the mesh division: the calculation area mesh adopts a hexahedron mesh structure, the maximum mesh size in the area is 20 m, and the minimum mesh size is 1 m.

[0052] In this embodiment, the continuous phase simulation mainly consists of the mass conservation equation, the momentum conservation equation, the energy conservation equation, and the component equation experiment. Specifically:

[0053] (1) Mass conservation equation

[0054]

[0055] Source term S m is the mass added to the continuous phase from the discrete phase due to the evaporation of drifting droplets (water droplets), ρ is the air density, t is the time, x i is the distance in the i direction, u i is the velocity in the i direction.

[0056] (2) Momentum conservation equation

[0057]

[0058] In the formula:

[0059] p—static pressure;

[0060] τ ij —stress tensor;

[0061] ρg i —the gravitational body force in the i direction;

[0062] F i —the external body force in the i direction (such as the buoyancy force generated by the interaction of the discrete phase);

[0063] x j is the distance in the j direction, u j is the velocity in the j direction.

[0064] The stress tensor is:

[0065]

[0066] (3) Energy conservation equation

[0067]

[0068] In the formula:

[0069] k eff —effective thermal conductivity;

[0070] J l —diffusion flux of component l;

[0071] The first three terms on the right side of the equation respectively describe the energy transport brought by heat conduction, component diffusion and viscous dissipation, and S h represents radiative heat transfer.

[0072] In the formula:

[0073] E is the energy, T is the temperature, h is the enthalpy, h l is the enthalpy of component l.

[0074] (4) Component equation

[0075]

[0076] In the formula:

[0077] m l — mass fraction of the l-th component;

[0078] Γ l — exchange coefficient of the l-th component;

[0079] R l — generation rate of the l-th component.

[0080] The air flow equations describing heat transfer, mass transfer and momentum transfer can be used as general equations and are expressed by the following formula:

[0081]

[0082] In the formula:

[0083] ρ – density of humid air, kg / m 3 ;

[0084] – velocity vector;

[0085] φ – generalized variable (such as velocity, mass percentage, etc.);

[0086] S φ – source term of the air phase;

[0087] S pφ – additional source term due to the interaction between air and drift droplets;

[0088] – convective term;

[0089] Γ φ gradφ – diffusion term, where Γ φ is the generalized diffusion coefficient.

[0090] In this embodiment, the discrete phase simulation process includes estimating the motion trajectories and velocities of drift droplets, the heat and mass transferred in and out of the drift droplets, and calculating the influence of the flow pattern between them through the coupling between the two phases. The motion of the drift droplets in the liquid phase field is described from the Lagrangian perspective, and the gas-liquid two-phase flow of the water vapor mixing process is numerically simulated.

[0091] (1) Calculation of drift droplet trajectories

[0092] The motion equations of the drift droplet velocity and trajectory in the Lagrangian coordinate system are as follows:

[0093]

[0094] In the formula:

[0095] rp - Drift droplet trajectory;

[0096] v p - Instantaneous velocity of the drift droplet.

[0097] The motion trajectory of the drift droplet is obtained by integrating the differential equation of the forces acting on the drift droplet in the Lagrangian coordinate system. This force balance is: the various forces acting on the drift droplet (drag force, buoyancy force, and other acting forces) are equal to the inertia of the drift droplet.

[0098] The differential equation form of the forces acting on the drift droplet in the Cartesian coordinate system is:

[0099]

[0100] Where:

[0101] ρ p - Density of the drift droplet, kg / m 3 ;

[0102] v - Air velocity, m / s;

[0103] v p - Drift droplet velocity, m / s;

[0104] F other - Other interaction forces.

[0105] F D Is calculated by the following formula:

[0106]

[0107] Where:

[0108] μ - Air viscosity, kg / m.s

[0109] C D - Drag coefficient,

[0110] Re - Is the relative Reynolds number,

[0111] (2) Heat transfer and mass transfer calculation

[0112] In a wet cooling tower, the heat transfer between the drift droplets and the surrounding air includes contact heat transfer and evaporative heat transfer. Since the amount of radiant heat transfer is very small, it can be ignored.

[0113] To find the value of the drift droplet temperature T p The heat balance of the contact heat transfer between the drift droplet and the surrounding air can be written by the following formula:

[0114]

[0115] Where:

[0116] M p - Drift droplet mass, kg;

[0117] c p - Specific heat of the drift droplet, J / kg·K;

[0118] A p - Surface area of the drift droplet, m 2 ;

[0119] α - Convective heat transfer coefficient, W / m 2 .K;

[0120] T adb - Dry bulb temperature of the air, K;

[0121] T p is the drift droplet temperature.

[0122] Assuming that the drift droplet temperature changes approximately linearly within consecutive integration times, the drift droplet temperature at the next moment is obtained as follows:

[0123]

[0124] The convective heat transfer coefficient (α) is calculated using the following formula:

[0125]

[0126] Where:

[0127] D p - Drift droplet diameter, m;

[0128] k ma - Thermal conductivity of the moist air, W / m.K;

[0129] Re d - Relative Reynolds number defined using the drift droplet diameter as the characteristic dimension;

[0130] Pr ma - Prandtl number of the continuous phase, c p μ / k ma .

[0131] The evaporation rate of the drift droplet is determined by gradient diffusion, i.e., the diffusion rate from the drift droplet to the gas phase is associated with the evaporation concentration gradient between the drift droplet and the air:

[0132]

[0133] Where:

[0134] k c - Mass transfer coefficient, m / s;

[0135] R - Universal gas constant.

[0136] The mass transfer coefficient (k c ) is calculated based on the similarity between heat transfer and mass transfer:

[0137]

[0138] Where:

[0139] D v - Vapor diffusion coefficient, m 2 / s;

[0140] Sc - Schmidt number (for mass transfer).

[0141] Therefore, the mass consumption of the drifting droplet is:

[0142]

[0143] k c is the mass transfer coefficient, R is the universal gas constant, P n (T p ) is the saturated water vapor pressure at temperature T p , and C is a constant.

[0144] Finally, the temperature of the drifting droplet is obtained through its own heat balance, and the calculation formula of the heat balance relates the enthalpy change of the drifting droplet to the contact heat transfer between the two phases and the latent heat of vaporization.

[0145]

[0146] Where:

[0147] - Evaporation rate, kg / s; γ 0 is a constant.

[0148] In this embodiment, evaporation and condensation are simulated:

[0149] When the temperature of the liquid droplet is below the boiling point or the vapor pressure of the water on the liquid droplet surface is less than the ambient pressure, the liquid droplet does not boil, and only evaporation and condensation occur.

[0150] The direction of evaporation or condensation of the liquid droplet, or rather the direction of water phase change, is controlled by the molar concentration of water molecules on the liquid droplet surface and in the moist air, that is, evaporation occurs when the molar concentration of water molecules in the moist air is less than that on the liquid droplet surface, and condensation occurs vice versa. When the mass transfer rates of evaporation and condensation are not large, the mass transfer rate is controlled by Fick's law.

[0151] P n (T p ) calculation method:

[0152]

[0153] Density calculation method of drifting droplets:

[0154] ρ p = 1063.9999 - 691.8390×T p 3 - 446.8621×T p 6

[0155] + 4766.6072×T p 9 - 2111.3447×T p 12

[0156] Latent heat calculation method of drifting droplets:

[0157] H V = 1000×exp[3.5 + 3.45×log 10 (647 - T p ) - 1.053×(log 10 (647 - T p )) 2

[0158] + 0.158345×(log 10 (647 - T p )) 3 - 0.0088×(log 10 (647 - T p )) 4 - 1

[0159] In this embodiment, boundary conditions are set as follows:

[0160] (1) Profile distribution types of the inlet boundary (such as inlet velocity, temperature, turbulence intensity, environmental humidity, etc.);

[0161] (2) Consider the influence of roughness (such as ground roughness);

[0162] (3) Particle inlet boundary can be set (such as mass flow rate, particle size distribution, etc.).

[0163] In this embodiment, result processing and analysis:

[0164] According to the flow field, concentration field and the results of the cooling tower plume deposition obtained by simulation, calculate whether the environmental impacts caused by the cooling tower plume (such as the impact of the plume on the smoke plume, the impact of the plume deposition, etc.) exceed the standards according to the standards. If they exceed, the design parameters need to be adjusted and recalculated.

[0165] According to the above scheme, the simulation of the evaporation and condensation effects of the cooling tower can be realized.

[0166] Example 2

[0167] This example discloses the specific implementation process of the numerical simulation method of the present invention:

[0168] 1. Establish a model

[0169] 2. Mesh generation

[0170] 3. Initial conditions: including inlet conditions, wind speed, temperature turbulence intensity and humidity. Specifically:

[0171] (1) The profile distribution type of the inlet boundary (such as inlet velocity, temperature, turbulence intensity, ambient humidity, etc.);

[0172] (2) Consider the influence of roughness (such as ground roughness)

[0173] (3) Set the particle inlet boundary (such as mass flow rate, particle size distribution, etc.)

[0174] 4. Boundary conditions: The ground is a no-slip wall, the sides are symmetric walls, and the top is an adiabatic wall.

[0175] 5. Continuum phase simulation until the residuals of wind speed, pressure, temperature and concentration are less than 10e-4

[0176] 6. Take the simulation results of the continuum phase steady state as the input conditions for the discrete phase. The discrete phase simulation process includes estimating the motion trajectory and velocity of the drift droplets, the heat and mass transferred in and out of the drift droplets. When the temperature of the droplet is below the boiling point or the vapor pressure of the water on the droplet surface is less than the ambient pressure, the droplet does not boil, only evaporation and condensation occur. At this time, calculate the temperature change and mass change of the drift droplets caused by evaporation and condensation. Then take the simulation results of the discrete phase drift droplets as the input into the continuum phase calculation for coupled simulation.

[0177] 7. Stop the calculation until the residuals of wind speed, pressure, temperature, concentration and deposition amount are less than 10e-4

[0178] 8. Result analysis

[0179] According to the flow field, concentration field and the results of the cooling tower plume deposition obtained from the simulation, calculate whether the environmental impacts caused by the cooling tower plume (the impact of the plume on the smoke plume, the impact of the plume deposition amount, etc.) exceed the standards according to the standards. If they exceed, the design parameters need to be adjusted and recalculated.

[0180] Example 3

[0181] The physical model of this embodiment is based on the on-site tracer experiment data of water vapor emissions from the natural draft cooling tower of the Chalk Point Power Plant in the United States. The cooling tower is 124 m high, with a bottom diameter of 114 m and a top outlet diameter of 54.8 m. The power plant is surrounded by sea on three sides, and the surrounding terrain structure is simple. The water vapor emission temperature is 315.3 T, the ambient temperature is 295.3 T, the ambient relative humidity is 93%, the water vapor emission rate is 4.5 m / s, and the water vapor particle size spectrum distribution is shown in Figure 2 , and during the test, the ambient wind speed at 100 m was measured to be 8 m / s. The ambient turbulence intensity at 50 m was 0.1. The positions of the water vapor ground deposition measurement points are located on an arc with the cooling tower as the center, with radii of 0.5 Km and 1.0 Km, and at intervals of 5° in the downwind direction at 35°.

[0182] The simulation area of this embodiment is centered on the cooling tower, taking 4 Km in the downwind direction of the cooling tower, 1.5 Km in the upwind direction of the cooling tower, 1.0 Km on each of the left and right sides, and the height is 1.0 Km. The computational domain grid adopts a hexahedral grid structure, with a total number of grids of about 800,000. The maximum grid size in the area is 20 m, and the minimum grid size is 1 m. The ambient wind speed above 100 m in the simulation area is a constant 8 m / s. The computational domain and its grid division are shown in Figure 2 , and the ambient turbulence intensity, ambient wind speed, and ambient humidity profile are shown in Figure 3 .

[0183] In this embodiment, the Reynolds-averaged N-S equation is used as the control equation, and the k-ε (RNG) model is used as the turbulence model. The numerical simulation of the gas-liquid two-phase flow in the water vapor mixing process is carried out by the method in this article. The Lagrangian view is used to describe the motion of liquid droplets in the liquid phase field; the SIMPLE algorithm is used for the gas phase field calculation.

[0184] Since the particle size distribution of droplets has a relatively large impact on the calculation of gas-liquid two-phase flow, and during the water vapor mixing process, the droplet diameter is approximately distributed between 10 and 1800 μm. In order to more realistically simulate the actual situation, this embodiment uses the Rosin-Rammler model to simulate the particle size distribution of droplets.

[0185] In the Rosin-Rammler model, the mass percentage M of droplets with a diameter greater than d is M = exp(-(d / dmean)^n), where dmean is the average diameter and n is the spread index. In this calculation, dmean = 0.009 mm and n = 0.65. The water vapor particle size spectrum distribution is shown in Figure 4 .

[0186] Figure 5 The calculation results of the drifting droplets of the cooling tower fog plume considering evaporation and condensation effects are given in

[0187] Figure 6 Among them, (a) and (b) respectively give the calculation results of the trajectory of the cooling tower plume under the DPM model and the present method. It can be seen from the figure that when using the DPM model for calculation, the influence range of the cooling tower plume is small and it settles at a short distance. When using the method of the present invention to consider the evaporation and condensation of the cooling tower, the influence range area becomes larger and is closer to the actual situation.

[0188] Figure 7 The results of the DPM model, the calculation results of the method of the present invention, and the results of on-site observation experiments are given. It can be seen from the figure that the overall deposition amount of the DPM model results on the ground is less than that in the case of considering evaporation and condensation, and the influence range is small, underestimating the impact of the cooling tower plume on the environment. At the same time, when considering the evaporation and condensation effects of the cooling tower, the calculation results of the method proposed in this project are in good agreement with the on-site test results, further verifying the effectiveness of the method of the present invention for the evaporation and condensation of the cooling tower.

[0189] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume, characterized in that, it includes the following steps: Establish a model according to the design parameters of the cooling tower; Perform mesh division according to the model; Based on the divided mesh, combine two methods of continuous phase and discrete phase. The continuous phase simulates the migration and diffusion of the cooling tower plume, and the discrete phase simulates the deposition of the cooling tower plume under the action of evaporation and condensation; Couple and simulate the deposition, migration and diffusion of the cooling tower plume to realize the simulation of the evaporation and condensation effects of the cooling tower plume; The method of using the continuous phase to simulate the migration and diffusion of the cooling tower plume includes: Among them, the source term S m is the mass added from the discrete phase to the continuous phase due to the evaporation of the drifting droplets, ρ is the air density, t is the time, and x i is the distance in the i direction, and u i is the velocity in the i direction; where p is the static pressure, τ ij is the stress tensor, ρg i is the body force of gravity in the i direction, F i is the external body force in the i direction, x j is the distance in the j direction, u j is the velocity in the j direction; Among them, k eff is the effective thermal conductivity, J l is the diffusion flux of component l, S h is the radiative heat transfer, E is energy, T is temperature, h is enthalpy, h l is the enthalpy of component l; where m l is the mass fraction of the l-th component; Γ l is the exchange coefficient of the l-th component; R l is the production rate of the l-th component. where ρ is the density of moist air, kg / m 3 , is the velocity vector, φ is the generalized variable, S φ is the source term of the air phase, S pφ is the additional source term due to the interaction between air and droplets, is the convection term, Γ φ gradφ - the diffusion term, where Γ φ is the generalized diffusion coefficient; The method of using the discrete phase to simulate the deposition of the cooling tower plume under the action of evaporation and condensation includes: Among them, r p is the drift droplet trajectory, and v p is the instantaneous velocity of the drift droplet; Among them, M p is the mass of the droplet, in kg, c p is the specific heat of the droplet, in J / kg·K, A p is the surface area of the droplet, in m 2 , α is the convective heat transfer coefficient, in W / m 2 .K, T adb is the dry-bulb temperature of the air, in K, T p is the droplet temperature; where k c is the mass transfer coefficient, R is the universal gas constant, P n (T p ) is the saturated water vapor pressure at temperature Tp, and C is a constant; Among them, is the evaporation rate, kg / s, and γ 0 is a constant.

2. The numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume according to claim 1, characterized in that, the model is: according to the area to be studied a km×b km, the simulation calculation domain is 1.5a km×1.5b km, where a < 10 km and b < 10 km.

3. The numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume according to claim 1, characterized in that, the divided mesh adopts a hexahedral mesh structure, the maximum mesh size in the area is 20 m, and the minimum mesh size is 1 m.

4. The numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume according to claim 1, characterized in that, The method for coupling the deposition, migration and diffusion of the fog plume of a simulated cooling tower includes: P n (T p ) calculation, calculation of the density of the drifting droplets and calculation of the latent heat of the drifting droplets.

5. The numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume according to claim 4, characterized in that, P n (T p ) is calculated as follows:

6. The numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume according to claim 4, characterized in that, The calculation method of the density of the drifting droplets includes:

7. The numerical simulation method applicable to the evaporation and condensation effects of the cooling tower plume according to claim 4, characterized in that, The calculation method of the latent heat of the drifting droplets includes:

Images