A method for determining a scraping cycle of a scraper in an evaporation process of a high-viscosity material

Abstract

The present application belongs to the field of liquid film evaporation heat transfer, and particularly relates to a method for determining the scraping and film removing cycle of a scraper in the evaporation process of high viscosity materials. The method comprises the following steps: (1) establishing a computational fluid domain geometric model and setting parameters of the computational fluid domain geometric model; the computational fluid domain geometric model is a cubic structure, the bottom surface is a heating wall surface, and the part above the bottom surface is a liquid film and gas area; (2) performing mesh division on the computational fluid domain geometric model, and performing local mesh densification on the heating wall surface; (3) performing transient evaporation calculation on the computational fluid domain geometric model to obtain a curve of the evaporation rate of the bottom of the liquid film changing with time; (4) analyzing the curve of the evaporation rate of the bottom of the liquid film changing with time, and the difference between the time tb corresponding to the highest point and the time ta corresponding to the starting point is the scraping and film removing cycle of the scraper. The method can determine the optimal scraping time of high viscosity materials, effectively destroy the gas film, improve the heat transfer coefficient, accelerate the evaporation rate, and optimize the evaporation efficiency.

Description

Technical Field

[0001] The invention belongs to the field of liquid film evaporation heat transfer, and in particular relates to a method for determining a scraper film scraping cycle in the evaporation process of a high-viscosity material. Background Art

[0002] As a highly efficient evaporation equipment, the scraped film evaporator is widely used in many industries such as chemical, pharmaceutical, food, and textile, mainly for concentrating raw material solutions. Its structure is mainly composed of three parts, which are the feeding area, scraped film area, and extrusion area in the vertical direction. Among them, the scraped film area undertakes the most critical evaporation and concentration tasks. After the material enters the scraped film area, it is evenly distributed on the heated wall surface through forced scraping by the scraper. Figure 1 As shown, the flow field within a wiped-film evaporator can be divided into two main regions: A circular wave forms at the leading edge of the scraper, where the fluid flows downward in a spiral. Between the trailing edge of the scraper and the next circular wave, the scraper's action disappears, transforming into a laminar liquid film. During this process, the volatile components in the material continuously absorb heat, undergoing a phase change and transforming into gas, thereby concentrating the raw material solution.

[0003] When processing highly viscous materials, their inherent poor fluidity and high resistance to heat and mass transfer present numerous challenges to the evaporation process. In a wiped-film evaporator, highly viscous materials are scraped by the scraper to form a liquid film, generating a large number of bubbles. Due to the extremely high viscosity of the material, the resulting liquid film is relatively thick, making it difficult for bubbles generated at the bottom of the film to escape. Instead, they gradually gather at the bottom, forming an air film. The presence of this air film has a profoundly negative impact on evaporation efficiency. From a heat transfer perspective, the air film acts as an insulating layer, severely hindering heat transfer from the heated wall surface to the interior of the material. Heat must struggle to pass through the air film to reach the material, and the thermal resistance of the air film is much higher than that of the material itself. This directly leads to a sharp increase in the heat transfer temperature difference and a significant increase in energy consumption. From a mass transfer perspective, the presence of the air film hinders the escape of moisture from the material. The literature (A Brief Discussion on the Structural Design of Scraper Blades in Scraper-Type Thin Film Evaporators (Part 1) [J]. Pharmaceutical Engineering Design, 2000, (04): 145-146) mentions that in order for moisture to escape smoothly from the interior of the material, the air film needs to be broken as quickly as possible, thereby refreshing the heat transfer surface. The authors used a scraper with a corrugated end face to achieve this goal. However, the authors did not study the timing of breaking the air film. In addition, the authors also mentioned that the specific scraper structure will vary depending on the material and the feed state, but did not discuss this further.

[0004] In industrial production practice, the common means of dealing with the gas film problem faced when evaporating high-viscosity materials is to increase the number of scraper rows or increase the scraper speed. However, simply increasing the number of scraper rows will not only significantly increase the cost of the equipment, but also due to the lack of targeted adaptation design for specific materials, it is difficult to accurately determine the most suitable number of scraper rows, resulting in the evaporation capacity of the equipment not being fully utilized. In fact, the core purpose of increasing the number of scraper rows is to increase the frequency of liquid film scraping, but this frequency is not determined solely by the number of scraper rows. The scraper speed also plays a key role. The existing technology has deeply explored the effect of scraper speed on evaporator performance through experiments. The results show that as the scraper speed increases, the total heat transfer coefficient and evaporation intensity will show a trend of first increasing and then decreasing. Moreover, in actual operation, regulating the scraper speed often requires a long period of trial and error and fine adjustment to barely achieve a relatively good evaporation efficiency.

[0005] It's worth noting that for highly viscous materials, excessive scraping frequency—that is, excessive number of scraper rows or excessive scraper speeds—will not only lead to increased costs and energy consumption, but will also cause the scrapers to scrape the liquid film prematurely, resulting in incomplete evaporation and ultimately affecting the concentration effect. Conversely, scraping too late will exacerbate the thermal resistance of the air film, seriously affecting heat transfer.

[0006] In summary, to effectively avoid the aforementioned issues, it's crucial to accurately determine the optimal scraping timing for evaporating highly viscous materials within a wiped-film evaporator. Only by finding this optimal timing can we ensure both evaporation efficiency and concentration while also balancing equipment costs and energy consumption, fully leveraging the performance advantages of the wiped-film evaporator when handling highly viscous materials. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for determining the scraping cycle of a scraper during the evaporation process of a high-viscosity material.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A method for determining a scraper film scraping cycle during the evaporation process of a high-viscosity material comprises the following steps:

[0010] (1) Establish a computational fluid domain geometry model and set the parameters of the computational fluid domain geometry model;

[0011] The geometric model of the computational fluid domain is a cubic structure, with the bottom surface being the heating wall, and the part above the bottom surface being the liquid film and the gas region, with the gas region being located above the liquid film.

[0012] The parameters of the computational fluid domain geometric model include the thickness of the liquid film, the thickness of the gas region, and the size of the bottom surface of the computational fluid domain geometric model;

[0013] The thickness of the liquid film is obtained by collecting the thickness of the liquid film formed by high-viscosity materials in the scraped film evaporator during the historical production process and taking the average value;

[0014] The thickness of the gas area is obtained by collecting the thickness of the gas area formed by high-viscosity materials in the wiped film evaporator during the historical production process and taking the average value;

[0015] High-viscosity materials are materials whose evaporable components transform into gas during evaporation and cannot escape from the bottom of the liquid film;

[0016] (2) Meshing the geometric model of the computational fluid domain and performing local mesh encryption on the heating wall;

[0017] (3) Set the boundary condition parameters of the computational fluid domain, perform transient evaporation calculations on the geometric model of the computational fluid domain, and obtain the evaporation rate curve at the bottom of the liquid film over time to simulate the heating process of the liquid film before being scraped;

[0018] (4) Analyze the curve of the evaporation rate at the bottom of the liquid film over time. The time corresponding to the starting point is recorded as ta, and the time corresponding to the highest point is recorded as tb. The difference between tb and ta is the scraper scraping cycle. The scraper scraping cycle is the time it takes for adjacent scrapers in the scraped film evaporator to scrape the same liquid film.

[0019] As the preferred technical solution:

[0020] In the above-mentioned method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material, in step (1), the bottom surface of the geometric model of the computational fluid domain is a rectangle with a length of 20-60 mm and a width of 20-60 mm. Since it is a simplified micro-element evaporation, the length and width are set mainly based on the following considerations: first, the full development of flow and heat transfer requires that the size cannot be too small; second, considering the computational resources and computational accuracy, the size cannot be too large. Finally, the length and width are set to balance the two.

[0021] In the above method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material, in step (2), the mesh is divided using a polyhedron-hexahedron hybrid mesh (Poly-Hexcore), such as Figure 2 As shown in (c).

[0022] In the above-mentioned method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material, in step (2), meshing the geometric model of the computational fluid domain refers to meshing the geometric model of the computational fluid domain using ANSYS Fluent Meshing software.

[0023] In the above-mentioned method for determining the scraping cycle of a scraper during the evaporation process of a high-viscosity material, in step (3), the boundary condition parameters of the calculated fluid domain include the temperature of the heated wall (determined according to the process in the industrial production process), the viscosity of the liquid film, and the initial temperature of the liquid film. The initial temperature of the liquid film is the same as the saturation temperature of the high-viscosity material (i.e., the heat absorption temperature of the high-viscosity material rises to reach the critical temperature for evaporation).

[0024] In the method for determining the scraping cycle of a scraper during the evaporation process of a high-viscosity material as described above, in step (3), when calculating transient evaporation, the proportion of the evaporable components of the liquid film is first set by the Species Transport model, and then the gas-liquid interface is tracked based on the VOF model, wherein the liquid phase is the high-viscosity material and the gas phase is steam. Finally, the phase change between the liquid and gas phases of the evaporable components in the high-viscosity material is realized based on the Lee model.

[0025] In the above-mentioned method for determining the scraper film scraping cycle during the evaporation process of a high-viscosity material, in step (3), when calculating transient evaporation, the time step is 0.001s, the number of time steps is 1000, and the total calculation time is 1s.

[0026] In the method for determining the scraping cycle of a scraper during the evaporation of a high-viscosity material as described above, in step (3), the process of obtaining the curve of the evaporation rate of the bottom of the liquid film over time is as follows: with a time interval of 0.1 s, the evaporation rate of the bottom of the liquid film at each moment is calculated, and after obtaining discrete data points, fitting is performed to obtain the curve of the evaporation rate of the bottom of the liquid film over time.

[0027] In the above-mentioned method for determining the scraping cycle of the scraper during the evaporation of a high-viscosity material, the steps for obtaining the evaporation rate at the bottom of the liquid film at each moment are as follows:

[0028] (a) Obtain the liquid phase volume fraction of the discrete layered cross-section of the computational fluid domain geometric model along the height direction at each time. After obtaining the discrete data points, fit them and obtain the curve of the liquid phase volume fraction changing with the height of the computational fluid domain geometric model at each time.

[0029] (b) Analyze the curve of the liquid phase volume fraction changing with the height of the computational fluid domain geometry model at each time, and find the minimum value ha of the computational fluid domain geometry model height when the liquid phase volume fraction is 0.5 at each time;

[0030] (c) Calculate the volume of the region with a height less than ha in the computational fluid domain geometry model at each time, as well as the phase change mass transfer rate. Calculate the evaporation rate at the bottom of the liquid film at each time using the following formula;

[0031] ;

[0032] Where, represents the evaporation rate of the liquid film at the bottom at each time, with units of kg / s; represents the phase change mass transfer rate of the area with a height less than ha in the computational fluid domain geometry model at each time, with units of kg / m 3 ·s; represents the volume of the area with a height less than ha in the computational fluid domain geometry model at each time, with units of m 3 .

[0033] Advantages:

[0034] (1) The present application aims at the problem of processing high-viscosity materials by a wiped film evaporator, and an innovative evaporation calculation model for high-viscosity materials is constructed. The model simplifies the complex three-dimensional model of the wiped film area into a small liquid film model, which fully reflects the influence of components on evaporation, greatly shortens the calculation time and saves the calculation resources. At the same time, the model associates the quantitative evolution of the gas film with the transient heat transfer, accurately determines the wiping frequency by fusing multiple parameter data such as the gas film thickness, the wall heat flux density, and the evaporation rate, and determines the optimal wiping time. This innovative measure not only avoids the problem of insufficient evaporation of the liquid film caused by early wiping, but also effectively suppresses the gas film thermal resistance effect, and realizes the optimal control of heat transfer intensification.

[0035] (2) Thanks to the above-mentioned model and method, the present application can effectively destroy the gas film, improve the heat transfer coefficient, and accelerate the evaporation rate. At the same time, by accurately controlling the optimal wiping time, the evaporation efficiency is closer to the optimal value, and the performance of the wiped film evaporator in processing high-viscosity materials is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a schematic diagram of the internal flow field distribution of a wiped film evaporator; wherein (a) is a perspective view, and (b) is a top view;

[0037] Figure 2 (a) is a computational fluid domain geometry model, (b) is a liquid film evaporation schematic diagram, (c) is a grid division diagram, and (d) is a local grid refinement diagram;

[0038] Figure 3 is a liquid film gas-liquid distribution cloud diagram under different evaporation component proportions;

[0039] Figure 4 is a curve of the liquid film volume fraction of the liquid film with different evaporation component proportions with respect to the height of the computational fluid domain geometry model at each time;

[0040] Figure 5 is a curve of the evaporation rate of the liquid film at the bottom with respect to time under different evaporation component proportions;

[0041] Figure 6 is a curve of the heat flux density with respect to time under different evaporation component proportions. DETAILED DESCRIPTION

[0042] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0043] A method for determining the scraping cycle of a scraper during the evaporation of a high-viscosity material, the specific steps are as follows:

[0044] (1) Establish a computational fluid domain geometry model and set the parameters of the computational fluid domain geometry model;

[0045] like Figure 2 As shown in (a), the geometric model of the computational fluid domain is a rectangular parallelepiped structure with a bottom length of 20 mm, a bottom width of 20 mm, a height of 6 mm, and a heating wall. Figure 2 As shown in (b), the part above the bottom surface is the liquid film (thickness is 3mm) and the gas area. The gas area is located above the liquid film, and the top surface is the steam outlet.

[0046] (2) The computational fluid domain is meshed using ANSYS Fluent Meshing software, using a polyhedron-hexahedron hybrid mesh (e.g. Figure 2 (c) in the figure), and the local mesh of the heated wall is refined (as shown in Figure 2 (d)

[0047] (3) Set the boundary condition parameters of the computational fluid domain and perform transient evaporation calculation on the geometric model of the computational fluid domain (time step size is 0.001s, number of time steps is 1000 steps, and total calculation time is 1s). Obtain the curve of the evaporation rate at the bottom of the liquid film changing with time.

[0048] The boundary condition parameters of the computational fluid domain include the temperature of the heated wall (104°C), the viscosity of the liquid film (200 Pa·s), and the initial temperature of the liquid film (100°C). The initial temperature of the liquid film is the same as the saturation temperature of the high-viscosity material (cellulose pulp, the raw material for producing Lyocell fiber).

[0049] When calculating transient evaporation, the Species Transport model is first used to set the proportion of the evaporable component of the liquid film (the evaporable component is water, and the evaporable component proportion is 10wt%, 20wt%, 30wt%, and 40wt%). Then, the VOF model is used to track the gas-liquid interface, where the liquid phase is a highly viscous material and the gas phase is steam. Finally, the Lee model is used to realize the phase transition between the liquid and gas phases of the evaporable component in the highly viscous material.

[0050] The process of obtaining the curve of the evaporation rate of the bottom of the liquid film over time is as follows: the evaporation rate of the bottom of the liquid film at each time interval is calculated at 0.1s, and the discrete data points are fitted to obtain the curve of the evaporation rate of the bottom of the liquid film over time;

[0051] like Figure 5 As shown in the figure, the evaporation rate of the bottom of the liquid film with different evaporable component ratios has the same trend with time, which increases rapidly at the beginning of heating, then increases slowly, and finally stabilizes; the liquid film with an evaporable component ratio of 40wt% decreases slightly after 0.5s and then stabilizes at around 0.4mg / s, the liquid film with an evaporable component ratio of 30wt% decreases slightly after 0.7s and then stabilizes at around 0.3mg / s; the liquid film with an evaporable component ratio of 20wt% and the liquid film with an evaporable component ratio of 10wt% continue to rise slightly after the slow rising stage, and reach the boundary values ​​of 0.24mg / s and 0.13mg / s respectively after 0.9s; here we focus on the solid-liquid interface with a relatively large evaporation rate, and ignore the gas-liquid interface with a relatively small evaporation rate; therefore, Figure 5 The statistical law of the evaporation rate at the bottom of the liquid film changing with time largely represents the overall situation of liquid film evaporation;

[0052] The steps for obtaining the evaporation rate at the bottom of the liquid film at each time are as follows:

[0053] (a) Obtain the liquid phase volume fraction of the discrete layered cross-section of the computational fluid domain geometric model along the height direction at each time, obtain the discrete data points and perform fitting to obtain the curve of the liquid phase volume fraction at each time as the height of the computational fluid domain geometric model is changed, as shown in Figure 2. Figure 4 As shown;

[0054] (b) Analyze the curve of the liquid phase volume fraction changing with the height of the computational fluid domain geometry model at each time, and find the minimum value ha of the computational fluid domain geometry model height when the liquid phase volume fraction is 0.5 at each time;

[0055] When the liquid phase volume fraction is 0.5, the minimum value ha of the height of the fluid domain geometric model is calculated, that is, the thickness of the gas phase film at the bottom of the liquid film. Figure 4 It can be seen that the higher the proportion of evaporable components, the thicker the gas phase film at the bottom of the liquid film at the same time. Figure 3The liquid film gas-liquid distribution cloud diagram shown also confirms this view. In the liquid film gas-liquid distribution cloud diagram, the blue area is the area where the liquid phase volume fraction in the liquid film is greater than 0.5, representing the liquid phase film, and the light blue area is the area where the liquid phase volume fraction in the liquid film is less than or equal to 0.5, representing the gas phase film. When the proportion of the evaporable component is 20wt%, 30wt%, and 40wt%, there are two light blue areas in total, among which the light blue area at the bottom represents the gas phase film at the bottom of the liquid film.

[0056] (c) Calculate the volume of the region with a height less than ha in the computational fluid domain geometry model at each time, as well as the phase change mass transfer rate. Calculate the evaporation rate at the bottom of the liquid film at each time using the following formula;

[0057] ;

[0058] Where, represents the evaporation rate at the bottom of the liquid film at each moment, in kg / s; Represents the phase change mass transfer rate in the region with a height less than ha in the computational fluid domain geometry model at each time, in kg / m 3 ·s; Represents the volume of the area with a height less than ha in the computational fluid domain geometry model at each moment, in m 3 ;

[0059] (4) Analyze the curve of the evaporation rate at the bottom of the liquid film over time. The time corresponding to the starting point is recorded as ta, and the time corresponding to the highest point is recorded as tb. The difference between tb and ta is the scraper scraping cycle. The scraper scraping cycle is the time it takes for adjacent scrapers in the scraped film evaporator to scrape the same liquid film.

[0060] Next, by determining the rate at which the heated wall transfers heat to the liquid film, we can derive the time-varying pattern of the wall heat flux density. Specifically, we count the wall heat flux density at each grid node at the bottom of the liquid film, and then calculate its average value, which is used as the average heat flux density between the heated wall and the liquid film. Next, we calculate the average wall heat flux density at each moment with a time interval of 0.1s. In the case of different proportions of evaporable components, we also perform calculations according to the above method, and finally obtain the following: Figure 6 The changing pattern shown. Figure 6As can be seen, the wall heat flux decreases rapidly as the heating process progresses, then decreases slowly and gradually stabilizes. Under the same heating conditions, liquid films with a high evaporable component ratio have higher wall heat fluxes. For example, the initial heat flux of a liquid film with a 40wt% evaporable component ratio is 4175 W / m², that of a 30wt% evaporable component ratio is 3640 W / m², that of a 20wt% evaporable component ratio is 2994 W / m², and that of a 10wt% evaporable component ratio is 2196 W / m². In practical applications of thin liquid film heat transfer, it is desirable to ensure rapid heat exchange between the liquid film and the heated wall, while also evaporating quickly to remove heat. Since the evaporation rate of a highly viscous liquid film is highest at the bottom during evaporation, a gas film is generated at the bottom, and the wall heat flux decreases over time. Therefore, in order to obtain better heat transfer effect and increase the evaporation rate of the liquid film, it is necessary to break the air film during the heating process to enhance heat transfer. When the evaporation rate at the bottom of the liquid film reaches the maximum, it is the most appropriate time to break the air film. Figure 5 By analyzing the temporal variation of the liquid film evaporation rate under different evaporable component ratios, we determined that the optimal time to break the film is 0.5s for a 40wt% evaporable component ratio, 0.7s for a 30wt% evaporable component ratio, and 0.9s for both 20wt% and 10wt% evaporable components. Once this optimal time to break the film is determined, the number of scraper rows and the scraper speed can be reversely designed. It should be noted that the film-breaking time is the time it takes for adjacent scrapers to scrape across the same portion of the liquid film within the wiped-film evaporator. If a shorter scraping time is required, and the scraper speed is not limited by energy consumption or structural strength, the scraper speed can be precisely controlled to achieve the optimal scraping time, significantly improving evaporation efficiency. If a shorter scraping time is required, but the scraper speed cannot be further increased due to energy consumption and structural strength limitations, the number of scraper rows can be precisely increased and a completely new structure can be designed, which can also greatly improve the efficiency of the wiped film evaporator.

Claims

1. A method for determining the scraping cycle of a scraper during the evaporation of a high-viscosity material, characterized in that: The following steps are involved: (1) Establish a computational fluid domain geometry model and set the parameters of the computational fluid domain geometry model; The geometric model of the computational fluid domain is a cubic structure, with the bottom surface being the heating wall, and the part above the bottom surface being the liquid film and the gas region, with the gas region being located above the liquid film. The parameters of the computational fluid domain geometric model include the thickness of the liquid film, the thickness of the gas region, and the size of the bottom surface of the computational fluid domain geometric model; The thickness of the liquid film is obtained by collecting the thickness of the liquid film formed by high-viscosity materials in the scraped film evaporator during the historical production process and taking the average value; The thickness of the gas area is obtained by collecting the thickness of the gas area formed by high-viscosity materials in the wiped film evaporator during the historical production process and taking the average value; High-viscosity materials are materials whose evaporable components transform into gas during evaporation and cannot escape from the bottom of the liquid film; (2) Meshing the geometric model of the computational fluid domain and performing local mesh encryption on the heating wall; (3) Setting the boundary condition parameters of the computational fluid domain, performing transient evaporation calculations on the geometric model of the computational fluid domain, and obtaining a curve of the evaporation rate at the bottom of the liquid film varying with time; The steps for obtaining the evaporation rate at the bottom of the liquid film at each time are as follows: (a) Obtain the liquid phase volume fraction of the discrete layered cross-section of the computational fluid domain geometric model along the height direction at each time, obtain the discrete data points, and perform fitting to obtain the change curve of the liquid phase volume fraction at each time as a function of the height of the computational fluid domain geometric model; (b) Analyze the curve of the liquid phase volume fraction changing with the height of the computational fluid domain geometric model at each time, and find the minimum value ha of the computational fluid domain geometric model height when the liquid phase volume fraction is 0.5 at each time; (c) Count the volume of the region with a height less than ha in the computational fluid domain geometry model at each time and the phase change mass transfer rate. Calculate the evaporation rate at the bottom of the liquid film at each time using the following formula; Where, represents the evaporation rate at the bottom of the liquid film at each moment, in kg / s; Represents the phase change mass transfer rate in the region with a height less than ha in the computational fluid domain geometry model at each time, in kg / m 3 ·s; V represents the volume of the area with a height less than ha in the computational fluid domain geometry model at each time, in m 3 ; (4) Analyze the curve of the evaporation rate at the bottom of the liquid film over time. The time corresponding to the starting point is recorded as ta, and the time corresponding to the highest point is recorded as tb. The difference between tb and ta is the scraper scraping cycle. The scraper scraping cycle is the time it takes for adjacent scrapers in the scraped film evaporator to scrape the same liquid film.

2. The method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material according to claim 1, characterized in that: In step (1), the bottom surface of the computational fluid domain geometric model is a rectangle with a length of 20-60 mm and a width of 20-60 mm.

3. The method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material according to claim 1, characterized in that: In step (2), the mesh is divided into polyhedron-hexahedron hybrid meshes.

4. The method for determining the scraping cycle of a scraper during the evaporation of a high-viscosity material according to claim 3, characterized in that: In step (2), meshing the computational fluid domain geometric model refers to meshing the computational fluid domain geometric model using ANSYS Fluent Meshing software.

5. The method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material according to claim 1, characterized in that: In step (3), the boundary condition parameters of the fluid domain are calculated including the temperature of the heated wall, the viscosity of the liquid film, and the initial temperature of the liquid film. The initial temperature of the liquid film is the same as the saturation temperature of the high-viscosity material.

6. The method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material according to claim 5, characterized in that: In step (3), when calculating transient evaporation, the proportion of the evaporable components of the liquid film is first set through the Species Transport model, and then the gas-liquid interface is tracked based on the VOF model, where the liquid phase is a high-viscosity material and the gas phase is steam. Finally, the phase change between the liquid and gas phases of the evaporable components in the high-viscosity material is realized based on the Lee model.

7. The method for determining the scraping cycle of a scraper in the evaporation process of a high-viscosity material according to claim 1, characterized in that: In step (3), when calculating transient evaporation, the time step is 0.001s, the number of time steps is 1000, and the total calculation time is 1s.

8. The method for determining the scraping cycle of a scraper during the evaporation of a high-viscosity material according to claim 7, characterized in that: In step (3), the process of obtaining the curve of the evaporation rate of the bottom of the liquid film over time is as follows: with a time interval of 0.1 s, the evaporation rate of the bottom of the liquid film at each moment is calculated, and after obtaining discrete data points, fitting is performed to obtain the curve of the evaporation rate of the bottom of the liquid film over time.

Images