An electronic cigarette liquid evaporation quality calculation method based on an evaporation model

Abstract

This invention discloses a method for calculating the evaporation mass of e-cigarette liquid based on an evaporation model. This method is implemented using fluid simulation software (such as Fluent). It involves adding convection-diffusion equations to the fluid simulation software to solve for the concentration distribution of vapor near the wall, and modifying the model's energy equation by adding a source term to account for the energy loss caused by the heating wire heating the atomizer core and the convective mass transfer on the atomizer core surface. Simulation calculations are performed under specific operating conditions of the atomizer core to obtain the evaporation mass per unit time under those conditions, and simultaneously, the temperature distribution at various points on the atomizer core model under those conditions. This method fills the gap in current e-cigarette liquid evaporation mass calculation models, which lack physically meaningful calculation methods that do not rely on empirical coefficients. This invention is easy to implement and conducive to widespread application.

Description

Technical Field

[0001] This invention belongs to the field of atomizer core design technology, and relates to a design method for atomizer cores, particularly a method for calculating the evaporation mass of e-cigarette liquid based on an evaporation model. This method can more conveniently and effectively calculate the atomization amount per unit time under different atomizer core design schemes, which is beneficial to atomizer core design. Background Technology

[0002] Because the temperature of the e-liquid does not reach its boiling point for most of the heating process of the e-cigarette atomizer, the e-liquid mainly evaporates into vapor. Currently, there are few numerical methods for calculating this evaporation mass, and most of them rely on empirical coefficients determined by experiments, resulting in unclear physical meaning of the calculation models. Summary of the Invention

[0003] This method provides a numerical calculation model for calculating the evaporation mass of e-liquid during the inhalation of electronic cigarettes, which has physical meaning and does not contain empirical coefficients. This numerical calculation method can accurately obtain the evaporation mass per unit time of the atomizer core under the corresponding operating conditions. At the same time, it can also obtain the temperature distribution of various parts of the atomizer core model under the corresponding operating conditions, which makes it easier for designers to design an atomizer core model with excellent atomization performance.

[0004] The technical solution adopted in this invention is as follows:

[0005] A method for calculating the evaporation mass of e-cigarette liquid based on an evaporation model, comprising:

[0006] In fluid simulation software, convection-diffusion equations are added to solve for the concentration distribution of flue gas near the wall, and the energy equation of the model is modified by adding source terms to take into account the energy loss caused by the heating wire heating the atomizing core and the convection mass transfer on the surface of the atomizing core. Simulation calculations are performed under specific operating conditions of the atomizing core to obtain the evaporation mass per unit time of the atomizing core under the corresponding operating conditions, and the temperature distribution of the atomizing core model under the corresponding operating conditions can also be obtained.

[0007] In the above technical solution, the method further includes the following:

[0008] First, draw the atomizing core mesh model containing the airflow channel, import the model into the fluid simulation software, modify the calculation model to a transient model, open the energy equation, calculate the Reynolds number corresponding to the model based on the incoming flow velocity of the airflow channel, and determine whether to use a turbulent model or a laminar flow model.

[0009] After confirming the model, a convection-diffusion equation is added to solve for the concentration distribution on the surface of the atomizing core, and the solution domain is set as the external gas flow domain;

[0010] Set the physical properties of the e-liquid inside the atomizer core, the outside air, and the atomizer core material; set the atomizer core as a porous medium region and set the corresponding porosity; set the boundary conditions.

[0011] The energy equation was modified by adding a heat source term to simulate the heating effect of the electric heating wire on the atomizer core, and by adding a convective mass transfer phase change loss term to simulate the energy loss on the surface of the atomizer core due to convective mass transfer; simulation calculations were then performed.

[0012] Furthermore, when drawing the mesh, it is necessary to distinguish between the external gas flow domain and the atomizing core region, the airflow inlet region at the bottom of the airflow channel, the airflow outlet region at the top of the airflow channel, the wall regions around the airflow channel, the heating section surface in the middle of the atomizing core, and the transport section surfaces on both sides. Further, the boundary conditions include: setting the airflow channel inlet as a velocity inlet, setting the incoming flow velocity and incoming gas temperature; setting the airflow channel outlet as a free flow outlet; setting the airflow channel wall as a symmetrical wall; setting the atomizing core heating section wall as a wall; modifying the thermal conditions to coupling conditions; defining the surface as a wall with specific values; setting the atomizing core transport section and the e-liquid inlet as walls; and setting the thermal conditions as system coupling thermal boundary conditions.

[0013] Furthermore, the numerical value of a specific wall is given by a new expression, as shown below:

[0014]

[0015]

[0016] Where: c VG The concentration of glycerol gas at that wall surface, c PG The concentration of propylene glycol gas on the wall surface is indicated by T, and T represents the temperature at various points on the wall surface.

[0017] Furthermore, a mesh layer on the surface of the atomizing core is extracted, and the volume corresponding to this mesh layer is calculated. Assuming that the heating power of the electric heating wire is uniformly distributed within this volume, the heating power per unit volume can be calculated and added as a heat source term to the energy equation to simulate the actual heating effect of the external electric heating wire on the surface of the atomizing core.

[0018] Furthermore, the surface grid cells of the atomizing core are extracted, and a convective mass loss term is added to the energy equation of these grid cells to simulate the energy loss caused by convective mass transfer on the atomizing core wall. The convective mass loss term is the mass loss at the corresponding grid multiplied by the corresponding latent heat.

[0019] The beneficial effects of this invention are:

[0020] This invention proposes a numerical calculation method for the evaporation mass of e-cigarette liquid during inhalation, based on an evaporation model. This method is physically meaningful and does not rely on empirical coefficients, filling the gap in current e-cigarette liquid evaporation mass calculation models that lack physically meaningful calculation methods that do not depend on empirical coefficients. This method is easy to implement and facilitates widespread application. Furthermore, it can be applied not only to the evaporation mass calculation of e-cigarette atomizing cores but also provides reference and guidance for other surface-heated atomization problems. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the airflow channel grid for the atomizer core.

[0022] Figure 2 This is a grid diagram including airflow channels and atomizing core.

[0023] Figure 3 This is a schematic diagram of the distribution of each boundary of the model.

[0024] Figure 4 This is a schematic diagram of the grid distribution on the wall of the atomizing core.

[0025] Figure 5 A schematic diagram of the cylindrical atomizer core design.

[0026] Figure 6 A schematic diagram of the rectangular atomizing core design.

[0027] Figure 7 This is a schematic diagram of the shape design of a single-groove atomizing core.

[0028] Figure 8 This is a schematic diagram of the external design of the dual-groove atomizing core.

[0029] Figure 9 This is a temperature distribution cloud map of the cross-section of a rectangular atomizing core.

[0030] Figure 10 This is a cloud map showing the temperature distribution across the cross-section of a single-groove atomizing core.

[0031] Figure 11 This is a cloud map showing the temperature distribution across the cross-section of the dual-groove atomizing core.

[0032] Figure 12 Concentration distribution cloud map of single-groove atomizing core cross section

[0033] Figure 13 Concentration distribution cloud map of the cross-section of the dual-groove atomizing core Detailed Implementation

[0034] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0035] This invention provides a method for calculating the evaporation mass of e-cigarette liquid based on an evaporation model. This method is implemented using fluid simulation software (such as Fluent). It involves adding convection-diffusion equations to the fluid simulation software to solve for the concentration distribution of vapor near the wall, and modifying the model's energy equation by adding a source term to account for the energy loss caused by the heating wire heating the atomizer core and the energy loss due to convective mass transfer on the atomizer core surface. Simulation calculations are performed under specific operating conditions of the atomizer core to obtain the evaporation mass per unit time under those conditions, and simultaneously, the temperature distribution at various points on the atomizer core model under those conditions can also be obtained. The principles of this invention are explained below with examples:

[0036] I. Theoretical Basis of Evaporation Model

[0037] Since heat conduction is thermal diffusion caused by random molecular collisions, and mass transfer is mass diffusion caused by the random permeation of molecules in a medium, both are diffusion effects caused by random molecular motion. Therefore, Fick proposed Fick's Law by analogy with Fourier's Law for calculating heat conduction, as shown in the following equation:

[0038]

[0039] Among them: J i This represents the mass flux density of component i, with the negative sign indicating that the mass flux density is related to the concentration gradient. The direction is opposite; the mass flow is along the normal direction of the isoconcentration surface and in the direction of decreasing concentration gradient; D ij This represents the mass diffusion coefficient of component i in medium j.

[0040] Fick's law can be used to calculate the mass flux density of the smoke at the atomizer core wall. Multiplying this by the corresponding area and the latent heat of the smoke components yields the energy loss due to convective mass transfer, as shown in the following formula:

[0041]

[0042] in: A represents the mass loss caused by convective mass transfer at various points within the atomizer core. s This represents the area of ​​a local part of the atomizer core perpendicular to the normal direction.

[0043] II. Adding Convection-Diffusion Equations

[0044] When calculating the mass loss at various local locations of the atomizer core, it is necessary to first determine the concentration gradient of the flue gas near the atomizer core wall. Since the concentration distribution of the flue gas near the wall cannot be directly calculated during the Fluent solution process, a convection-diffusion equation needs to be added manually to solve for the concentration distribution of the flue gas near the wall. The convection-diffusion equation is shown below:

[0045]

[0046] Where: c represents the mass concentration of the component, D represents the mass diffusion coefficient of the corresponding component, and u x u y u z These represent the airflow velocities in the x, y, and z directions, respectively.

[0047] In Fluent, users can add custom scalar transport equations, as shown below:

[0048]

[0049] Expanding the above equation along the x, y, and z directions yields the following result:

[0050]

[0051] Where ρ represents the density of the substance within the watershed in which the convection-diffusion equation is applied, and Γ represents the diffusion coefficient of the component. Analogous to the standard convection-diffusion equation, Fluent's scalar transport equation multiplies both sides by the density of the substance within the watershed. Therefore, when calculating the diffusion coefficient Γ in Fluent's scalar transport equation, it is necessary to multiply the mass diffusion coefficient of the convection-diffusion component by the density of the corresponding substance within the watershed, i.e.:

[0052] Γ=Dρ

[0053] When setting up Fluent's scalar transport equations, the flue gas concentration near the wall and the flue gas diffusion coefficient Γ within the watershed need to be given. Regarding the flue gas composition, after consulting relevant literature, it was found that the main components of flue gas are currently propylene glycol and glycerol. Therefore, this model assumes two types of flue gas: 1) pure propylene glycol; 2) pure glycerol, and the generated flue gas is also composed of propylene glycol and glycerol. The mass diffusion coefficient of propylene glycol in air at 25°C is found to be 8.79 × 10⁻⁶. -6 m 2 The mass diffusion coefficient of glycerol is 7.63 × 10⁻⁶ / s. -6 m 2 / s, assuming the outside air temperature is 25℃, the corresponding air density is 1.185kg / m³. 3 Substituting these values ​​into the equation, the diffusion coefficients in the convection-diffusion equations for pure propylene glycol flue gas and pure glycerol flue gas can be calculated.

[0054] After specifying the diffusion coefficients for different flue gases, the concentrations of different flue gases at the atomizer core wall are also required to solve for the corresponding flue gas mass concentration distribution using the convection-diffusion equation. For the calculation of the flue gas concentration at the wall, it is assumed that the flue gas at the wall satisfies the ideal gas law. According to the ideal gas law:

[0055] pv = nRT

[0056] Where: p represents gas pressure, v represents gas volume, n represents the amount of substance of the gas components, R is the molar gas constant, and T represents gas temperature.

[0057] The formula for calculating gas density can be derived from the ideal gas law:

[0058]

[0059] Where M represents the molar mass of the gaseous component.

[0060] Analysis of the above formula reveals that to calculate the corresponding gas density, it is first necessary to determine the corresponding gas volume and the molar mass of each component within the gas. The molar mass of each component depends only on the component type; once the gas components are determined, their corresponding molar masses can be determined. Therefore, to accurately calculate the density of flue gas, it is first necessary to accurately calculate the flue gas pressure. For the calculation of the pressure of pure propylene glycol and pure glycerol gases, this model will use the Antoine equation for approximation. Currently, there are many empirical coefficients for the Antoine equation for these two gases. This model compares the empirical coefficient values ​​compiled by the National Institute of Standards and Technology (NIST) and the Iranian Chemical Engineers Website (IRCHE). The specific Antoine empirical formulas for pure propylene glycol and glycerol gases provided by NIST are shown below:

[0061]

[0062]

[0063] The Antoine empirical formulas for pure propylene glycol and glycerol gases provided by IRCHE are as follows:

[0064]

[0065]

[0066] Where: the subscript VG represents pure glycerol gas, the subscript PG represents pure propylene glycol gas, the temperature T is in °C, the gas pressure unit of the Antoine equation given by NIST is bar, and the gas pressure unit of the Antoine equation given by IRCHE is mmHg.

[0067] Substituting the two Antoine equations into the Fluent local model yields similar results, so both can be used in subsequent calculations.

[0068] III. Modifying the Energy Equation

[0069] Considering the actual heating effect of the electric heating wire on the atomizer core and the energy loss on the surface of the atomizer core due to atomization mass loss, the energy equation of the atomizer core needs to be modified. The influence of both on the atomizer core temperature is taken into account by adding a source term. The energy equation of the atomizer core is as follows:

[0070]

[0071] Where: ρ represents the density of the atomizing core, c p This represents the isobaric specific heat capacity of the atomizer core, where T represents the temperature at various points within the atomizer core. The velocity of the airflow over the surface of the atomizer coil is represented by k, and the thermal conductivity of the atomizer coil is represented by S. h This is the source term for the atomizer core energy equation. The heat source term and the convective mass transfer loss term in this model will both be added to this source term.

[0072] Add heat source item

[0073] To address the heating effect of the external heating wire on the atomizer core, a heat source term will be added to the model's energy equation. Since the atomizer cores of currently available e-cigarettes from brands like Zhongyan, RELX, and Youzi all utilize surface heating, a mesh layer on the atomizer core surface will be extracted in the Fluent numerical simulation to better simulate the actual heating effect of the heating wire. The volume corresponding to this mesh layer will be calculated. Assuming the heating power of the heating wire is uniformly distributed within this volume, the heating power per unit volume can be calculated.

[0074]

[0075] Where: q represents the heating power per unit volume of the atomizing core surface, P represents the total heating power of the external electric heating wire, and V represents the volume of the atomizing core wall mesh.

[0076] The heating power per unit volume calculated by the above formula is added to the Fluent energy equation to simulate the actual heating effect of an external electric heating wire on the surface of the atomizing core.

[0077] Adding convective mass loss term

[0078] Because the e-liquid within the atomizer core atomizes into vapor under the heating of an external electric heating wire, the mass loss of this e-liquid causes an overall energy loss in the model. Therefore, to simulate the energy loss caused by convective mass transfer in reality, a convective mass transfer loss term needs to be added to the model's energy equation. The calculation of local mass loss has been detailed above. The corresponding energy loss can be calculated by multiplying the mass loss by the corresponding latent heat, as shown below:

[0079]

[0080] Where: h fg This indicates the latent heat corresponding to the components of the atomizing liquid.

[0081] Since convective mass transfer mainly occurs near the outer surface of the atomizer core, in Fluent numerical simulations, analogous to adding a heat source term, the surface mesh cells of the atomizer core are first extracted. Convective mass transfer loss terms are then added to the energy equations of these mesh cells to simulate the energy loss caused by convective mass transfer at the atomizer core wall.

[0082] This method requires commercial fluid simulation software such as Fluent for calculations. First, a mesh model of the atomizing core, including airflow channels, needs to be created using mesh generation software (ICEM, Gambit), as shown below. Figure 1 , Figure 2 As shown;

[0083] In this example, a cylindrical atomizing core model is used, and the external airflow channel is a cuboid flow domain. When drawing the mesh, it is necessary to distinguish the external gas flow domain. Figure 1 The atomizer core area is further divided into the airflow inlet area at the bottom of the airflow channel, the airflow outlet area at the top of the airflow channel, the wall area around the airflow channel, the heating section surface in the middle of the atomizer core, and the transport section surfaces on both sides. The specific distribution of each part is as follows: Figure 3 As shown;

[0084] Import the drawn mesh model into Fluent commercial software, modify the calculation model to a transient model, enable the energy equation, and calculate the Reynolds number corresponding to the model based on the incoming flow velocity in the airflow channel to determine whether to use a turbulent or laminar flow model. In this example, the external airflow channel ( Figure 1 The inlet flow velocity is 0.2 m / s, the cross-sectional diameter of the atomizing core is 3 mm, and the ambient air temperature is assumed to be 25 degrees Celsius. Based on the Reynolds number calculation formula:

[0085]

[0086] In the above formula, ρ represents the density of air in the gas flow domain, v represents the inlet velocity of the airflow channel, d represents the characteristic size of the model, and in this example, the cross-sectional diameter of the atomizing core is 3mm. μ represents the dynamic viscosity of air in the airflow channel. The calculated Reynolds number is compared with 2300. If it is greater than 2300, the turbulence model is turned on; if it is less than 2300, the laminar flow model is turned on.

[0087] After confirming the model, add a convection-diffusion equation to solve for the concentration distribution on the surface of the atomizer core. The convection-diffusion equation is added by adding the UDS equation (User Defined Scalar) in Fluent. Uncheck the InletDiffusion option, select the solution region (set to the external gas flow domain), and keep all other settings unchanged.

[0088] In the Model's Materials section, add the physical properties of the e-liquid inside the atomizer core, the outside air, and the atomizer core material. In the Cell Zone Conditions section, set the atomizer core to a porous zone and set the corresponding porosity; in this example, it is set to 0.44.

[0089] Set boundary conditions: Set the airflow channel inlet as a velocity inlet; in this example, set the incoming flow velocity to 0.2 m / s and the incoming gas temperature to 298.15 K. Set the airflow channel outlet as free flow. Set the airflow channel wall as a symmetry wall. Set the atomizer core heating section wall as a wall. Modify the thermal conditions to coupled conditions. In the UDS equation settings, define this surface as a specified value wall, and the numerical value is expressed by a new expression.

[0090] Given an expression, the specific expression is as follows:

[0091]

[0092]

[0093] In the above two formulas: c VG The concentration of glycerol gas at that wall surface, c PG This refers to the concentration of propylene glycol gas on the wall surface, and T represents the temperature at various points on that wall surface. In this example, it is assumed that the wall surface is entirely covered with propylene glycol flue gas, therefore we choose to calculate c. PG Substitute the formula into the equation.

[0094] The atomizer core transport section and e-liquid inlet are set as walls, and the thermal conditions are system-coupled thermal boundary conditions.

[0095] The pressure-velocity coupling algorithm was modified to a coupled algorithm, and the transient formulation was changed to a second-order implicit form. The time step was set to 0.001s, with a maximum of 20 iterations per time step, for a total of 3000 calculation steps, to simulate the actual 3s pumping time.

[0096] The addition of heat source and phase change loss terms is implemented through UDF code. This code first extracts the mesh of the heating section of the atomizer core near the atomizer core, exports the volume of this side of the mesh, calculates the total volume, and then calculates the heating power per unit volume using the following formula:

[0097]

[0098] in: This represents the heating power per unit volume of the atomizer core surface, where P represents the total heating power of the external electric heating wire, and V represents the volume of the atomizer core wall mesh. In this example, the heating power is 4W.

[0099] The addition of the phase transition loss term employs a similar method. First, the mesh on the heating section wall of the atomizer core, near the atomizer core, is extracted using UDF code. Then, the concentration gradient of a layer of mesh in the gas region adjacent to these meshes in the normal direction is calculated (using the UDS equation added above). The mesh distribution at the atomizer core wall is as follows: Figure 4 As shown;

[0100] The corresponding phase transition energy loss can be calculated using the following formula:

[0101]

[0102] Where: D ij This represents the mass diffusion coefficient of the corresponding flue gas in the external airflow channel. In this example, pure propylene glycol flue gas is used, and its mass diffusion coefficient in air at 25 degrees Celsius is 8.79 × 10⁻⁶. -6 m 2 / s, A represents the concentration gradient of a layer of grid adjacent in the normal direction to the grid on the side of the heating section wall near the atomizer core. s h represents the area of ​​the mesh perpendicular to the normal direction. fg This represents the latent heat corresponding to the components of the flue gas liquid; in this example, it is taken as 810,000 J / kg.

[0103] Finally, the heat source item and phase transition loss term This can be added to the energy equation of the grid on the side of the heating section wall of the atomizer core that is close to the atomizer core.

[0104] Results Analysis

[0105] Using the evaporation mass calculation model introduced earlier, we calculated the atomization volume per unit time for several currently available atomizer coil designs, as shown below:

[0106] This section will mainly discuss the influence of different atomizer core shapes on the temperature distribution and atomization volume per unit time of the atomizer core model. To improve the comparability, we will mainly compare four types of atomizer core models: cylindrical, cuboid, single-groove, and double-groove. The cylindrical atomizer core has a circular cross-section with a radius of 3mm. The axial part is divided into two parts: the middle part is the heating section of the atomizer core, which is uniformly covered with an 8mm long electric heating wire; the two sides are the atomizer core transport sections, which mainly use the capillary force of the atomizer core pores to transport the atomized liquid from the storage chamber through the transport sections to the heating section of the atomizer core for heating. The rectangular atomizing core has a square cross-section with sides of 3mm. Its axial distribution is consistent with the cylindrical atomizing core. The central 8mm section is the heating section, and the two 4mm sections on either side are the transport sections. The single-groove atomizing core is based on the rectangular atomizing core, with a smaller rectangular prism (6mm x 2mm x 2mm) carved out in the center. Heating wires are evenly laid on the groove surface. The double-groove atomizing core is based on the rectangular atomizing core, with two smaller rectangular prisms (6mm x 0.9mm x 2mm) carved out in the center. Heating wires are also evenly laid on the groove surface. Schematic diagrams of the four atomizing core shapes are shown below. Figures 5-8 As shown;

[0107] The comparison of these four atomizer coil shapes still used a heating power of 4W. The overall porosity of the four atomizer coil models was 0.44. Surface heating was used, with the heating surface covering all outer surfaces of the transport section of the four atomizer coil models. The flow velocity of the external airflow channel was set to 0.2m / s. The specific calculation results for the four atomizer coil models are shown in the table below:

[0108] Table 1. Schematic diagram of local suction model results corresponding to four atomizer core shapes.

[0109]

[0110] Table 1 clearly shows that cylindrical atomizing cores have higher overall wall surface temperature and higher atomization rate per unit time compared to cuboid atomizing cores. Single-groove and double-groove atomizing cores, due to their grooved structure, have a larger overall convective mass transfer area and thus a higher atomization rate per unit time compared to cuboid atomizing cores. To better analyze the phenomenon that single-groove and double-groove atomizing cores have higher average wall surface temperatures than cuboid atomizing cores, we derived cross-sectional temperature distribution cloud maps for the three atomizing core models, as shown below. Figure 9 , 10 As shown in Figure 11.

[0111] pass Figure 9 , 10 It's not hard to see that, compared to a single-groove atomizer coil, a rectangular atomizer coil has a larger convective heat transfer area, resulting in greater heat loss through convection. Therefore, under the same external heating power, the surface temperature of the rectangular atomizer coil in contact with the outside air will be higher. However, through... Figure 10 It's easy to see that the grooves of a single-groove atomizer core tend to trap heat. External airflow cannot quickly remove this heat, causing it to accumulate inside the grooves. This results in a higher surface temperature within the grooves, leading to a higher average surface temperature compared to a cuboid atomizer core. While a single-groove atomizer core has a larger convective heat transfer area than a cylindrical one, resulting in greater overall convective heat loss, a lower average surface temperature, and lower surface vapor concentration, the larger overall convective mass transfer area means that the atomization rate per unit time is relatively similar for both. Compared to single-groove atomizer coils, dual-groove coils have a larger overall convective heat transfer area, resulting in greater convective heat loss per unit time. Therefore, the overall temperature of the atomizer coil is lower than that of a single-groove coil. However, due to its smaller groove structure, the dual-groove coil concentrates heat more effectively, leading to higher local temperatures in the groove areas compared to single-groove coils. This results in a higher vapor concentration near the groove walls, a greater concentration gradient, and thus, more vapor production. The cross-sectional concentration distribution cloud diagrams of single-groove and dual-groove atomizer coils are shown below. Figure 12 , Figure 13 .

[0112] From the two images above, it is quite obvious that the concentration near the grooves is greater in a dual-groove atomizing core compared to a single-groove atomizing core, resulting in a greater overall atomization volume per unit time.

[0113] The numerical model proposed above can not only accurately calculate the amount of atomization per unit time under different operating conditions of different atomizer cores, but also obtain the temperature distribution and concentration distribution of various parts of the atomizer core. This is of great help in designing an atomizer core with excellent atomization performance.

Claims

1. A method for calculating the quality of e-liquid vaporization of an electronic cigarette based on a vaporization model, characterized in that, include: In the fluid simulation software, a convection-diffusion equation is added to solve the concentration distribution of flue gas near the wall, and the energy equation of the model is modified to take into account the energy loss caused by the heating wire heating the atomizing core and the convection mass transfer on the surface of the atomizing core by adding a source term. Simulation calculations are performed under specific working conditions of the atomizing core to obtain the evaporation mass per unit time of the atomizing core under the corresponding working conditions, and the temperature distribution of the atomizing core model under the corresponding working conditions can also be obtained. Specifically, the steps include the following: First, draw the atomizing core mesh model containing the airflow channel, import the model into the fluid simulation software, modify the calculation model to a transient model, open the energy equation, calculate the Reynolds number corresponding to the model based on the incoming flow velocity of the airflow channel, and determine whether to use a turbulent model or a laminar flow model. After confirming the model, a convection-diffusion equation is added to solve for the concentration distribution on the surface of the atomizing core, and the solution domain is set as the external gas flow domain; Set the physical properties of the e-liquid inside the atomizer core, the outside air, and the atomizer core material; set the atomizer core as a porous medium region and set the corresponding porosity; set the boundary conditions. The energy equation was modified by adding a heat source term to simulate the heating effect of the electric heating wire on the atomizing core, and by adding a convective mass transfer phase change loss term to simulate the energy loss on the surface of the atomizing core due to convective mass transfer. Perform simulation calculations; The boundary conditions include: setting the airflow channel inlet as a velocity inlet, setting the incoming flow velocity and incoming gas temperature; setting the airflow channel outlet as a free flow outlet, setting the airflow channel wall as a symmetrical wall, setting the atomizer core heating section wall as a wall, modifying the thermal condition to a coupling condition, defining this surface as a specific numerical wall, setting the atomizer core transport section and e-liquid inlet as walls, and setting the thermal condition as a system coupled thermal boundary condition; the specific numerical wall value is given by the following expression: , , wherein: denotes the concentration of propylal gas at the wall surface, denotes the concentration of propylal gas at the wall surface, denotes the temperature at each point of the wall surface; A layer of mesh is extracted from the surface of the atomizer core, and the volume corresponding to this mesh is calculated. Assuming that the heating power of the electric heating wire is uniformly distributed within this volume, the heating power per unit volume can be calculated. This power is then added as a heat source term to the energy equation to simulate the actual heating effect of the external electric heating wire on the surface of the atomizer core.

2. The method of claim 1, wherein, When drawing the grid, it is necessary to distinguish between the external gas flow area and the atomizing core area, the air inlet area at the bottom of the airflow channel, the air outlet area at the top of the airflow channel, the wall area around the airflow channel, the heating section surface in the middle of the atomizing core, and the transport section surfaces on both sides.

3. The method for calculating the evaporation mass of electronic cigarette liquid based on an evaporation model according to claim 1, characterized in that, The surface grid cells of the atomizing core are extracted, and a convective mass loss term is added to the energy equation of these grid cells to simulate the energy loss caused by convective mass transfer on the atomizing core wall. The convective mass loss term is the mass loss at the corresponding grid multiplied by the corresponding latent heat.

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